NOTE REGARDING FORWARD-LOOKING STATEMENTS

Unless the context requires otherwise, in this Annual Report on Form 10-K10‑K the terms “Ardelyx”, “we,” “us,” “our” and “the Company” refer to Ardelyx, Inc.

This Annual Report on Form 10-K10‑K contains forward-looking statements that involve risks and uncertainties. Any statements contained herein that are not statements of historical facts may be deemed to be forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “continue,” “could,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “predict,” “potential,” “positioned,” “seek,” “should,” “target,” “will,” “would,” and other similar expressions that are predictions of or indicate future events and future trends, or the negative of these terms or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

Factors that could cause actual results or conditions to differ from those anticipated by these and other forward-looking statements include those more fully described in the “ITEM“ITEM 1A. RISK FACTORS”FACTORS” section and elsewhere in this Annual Report on Form 10-K.10‑K. Except as required by law, we assume no obligation to update any forward-looking statement publicly, or to revise any forward-looking statement to reflect events or developments occurring after the date of this Annual Report on Form 10-K,10‑K, even if new information becomes available in the future. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in any such forward-looking statement.

ITEM 1. BUSINESS

COMPANY OVERVIEWCompany overview

We are a clinical-stagespecialized biopharmaceutical company focused on developing first-in-class, disruptive medicines for the discovery, developmenttreatment of renal diseases. Our primary therapeutic focus is on treating people with renal diseases, which affect both the heart and commercialization of innovative, minimally-systemic therapeutic drugs that work exclusively in the gastrointestinal, or GI, tract to treat GI and cardio-renal diseases. We have developed a proprietary drug discovery and design platform enabling us, in a rapid and cost-efficient manner, to discover and design novel drug candidates. Utilizing our platform, we discovered and designed our lead product candidate, tenapanor, which is currently being evaluated in two pivotal Phase 3 clinical studies in patients with constipation-predominant irritable bowel syndrome, or IBS-C. In a Phase 2b clinical study, tenapanor demonstrated the ability to improve the symptoms of IBS-C. In a separate Phase 2b clinical trial, tenapanor demonstrated the ability to lower elevated serum phosphorus levels inkidneys. This includes patients with end-stage renal disease, or ESRD.ESRD, who suffer from elevated serum phosphorus, or hyperphosphatemia; patients with chronic kidney disease, or CKD, and/or heart failure patients with elevated serum potassium, or hyperkalemia. We have initiated an additionalalso developed a number of programs directed toward treating gastrointestinal, or GI, disorders, including the treatment of irritable bowel syndrome with constipation, or IBS-C.

Our portfolio is led by the development of tenapanor, a first-in-class inhibitor of NHE3. In our renal pipeline, tenapanor is being evaluated in a second Phase 2b clinical3 trial for the treatment of hyperphosphatemia in patients with ESRD who are on dialysis. This registration trial follows a successful first Phase 3 trial completed in 2017, which achieved statistical significance for the primary endpoint. We are also advancing a small molecule potassium secretagogue program, RDX013, for the potential treatment of hyperkalemia. We believe that both tenapanor and RDX013 have the potential to evaluate dosing regimensprovide treatment options that are differentiated significantly from binders, the current standards of care in both of these markets. We believe our small molecule approach to treating these conditions could significantly reduce the pill burden for patients, leading to higher compliance, and offer completely new mechanisms of action that interact with receptors in the gut, potentially allowing improved efficacy in some patients.

In addition to the development for renal diseases, we have developed tenapanor for the treatment of hyperphosphatemia,patients with IBS-C. In 2017, we completed the T3MPO program for this indication, including two Phase 3 studies, both of which achieved statistical significance for the primary endpoint, and a long-term safety extension study. We believe that data from the T3MPO program collectively demonstrated the ability of tenapanor to provide sustained relief of constipation and reduced abdominal pain with a generally favorable tolerability profile. Based on the results of the T3MPO clinical program in IBS-C, we are preparing to submit our first New Drug Application, or elevated serum phosphorus, in ESRD patients,NDA, to the United States Food and we expect to receive results from this trialDrug Administration, or FDA, in the second half of 2016. We are developing another drug candidate, RDX022,2018 for tenapanor for the treatment of hyperkalemia, or elevated serum potassium. In January 2016, we announced the results of an open label clinical study evaluating the pharmacodynamic activity of RDX022 in healthy adult volunteers. The study demonstratedIBS-C.

Our Commercial Strategy

We aim to build a multi-product company that RDX022 was generally well-tolerated at all doses evaluated and effectively binds to potassium in the GI tract, supporting our plans to proceed with a Phase 3 clinical program, which we currently expect to initiate in the second half of 2016. We are pursuing a 505(b)(2) regulatory pathway for RDX022. We have additional drug candidates in earlier stages of research and development focused in GI and cardio-renal diseases including RDX009, a secretagogue of glucagon-like peptide-1, or GLP-1, and glucagon-like peptide-2, or GLP-2, and RDX013, a potassium secretagogue. We currently expect to file an investigational new drug application, or IND, for RDX009 in the second half of 2016.

Tenapanor is a minimally-systemic small molecule that acts locally in the GI tract to inhibit the sodium transporter NHE3 and reduce sodium and phosphorus uptake from the gut. In human studies of orally- administered tenapanor, the drug was detected in the blood in only 0.7% of more than 3,000 collected serum samples, and even in those, at very low levels (< 1.5 ng/mL). We have evaluated tenapanor in fourteen human clinical studies in over 1,000 individuals to date. We are currently evaluating tenapanor in two different programs:

We believe the market opportunity for tenapanor for these two potential patient populations may be significant. Based on reports in the literature regarding the prevalence of IBS in the U.S. population and the percentage of individuals who have IBS-C as compared to other forms of IBS, we believe that 1.4% of the U.S. population, or approximately 4.4 million individualscommercializes its renal products in the United States haveStates. Our strategy is to leverage ex-U.S. collaborations with established industry leaders to efficiently bring our renal medicines to patients outside the United States. Additionally, our goal is to bring tenapanor for IBS-C to market by leveraging domestic and ex-U.S. collaborations.

In November 2017, we entered into a license agreement that approximately 1.0 million of those patients have been diagnosedprovides Kyowa Hakko Kirin Co., Ltd., or KHK, with IBS-C. Additionally, we estimate that there are about 6.6 million IBS-C patients in Europeexclusive rights to develop and about 3.4 million in Japan.

We are developing RDX022commercialize tenapanor for the treatment of hyperkalemia. RDX022 is our proprietary oral, non-absorbed potassium-binder. It iscardiorenal diseases, including hyperphosphatemia, in Japan. Under the terms of the license agreement, we received a $30 million upfront payment and are eligible to receive up to $130 million in development and commercialization milestones based on polystyrene sulfonate, a well-known and well-characterized polymer, used to treat hyperkalemia. We have made numerous improvements toupon currency exchange rates as of the polymer by engineering into RDX022 several key physical and chemical modifications in an effort to improve various properties. We also changedeffective date of the counter-ion from sodium to calcium to be more consistent with standard of care in these patients. We have filed a patent application covering the composition of matter for these modifications. Data from the literaturelicense agreement, as well as independent market research suggests that hyperkalemia affects about 900,000 individualshigh-teen royalties on net sales throughout the term of the agreement.

In December 2017, we entered into a license agreement with CKD Stage 3bShanghai Fosun Pharmaceutical Industrial Development Co. Ltd., or Stage 4, about 900,000Fosun Pharma, providing Fosun Pharma with the exclusive rights to develop and commercialize tenapanor in China for the treatment of patients with HFhyperphosphatemia related to CKD and about 200,000 patients with ESRD. In January 2016,IBS-C. Under the terms of the agreement, we announced resultsreceived an upfront payment of $12 million and are eligible to receive additional milestones of up to $113 million, as well as tiered royalties on net sales ranging from an open-label pharmacodynamic study of RDX022 in healthy adult volunteers. In this study, RDX022 was administered at 4.6 g BID (9.2 g/day), 6.9 g BID (13.8 g/day), 4.6 g TID (13.8 g/day) and 9.2 g TID (27.5 g/day), and resulted in a mean increase of fecal potassium from baseline of 888 mg/day, 1,791 mg/day, 1,408 mg/day, and 1,670 mg/day, respectively. RDX022 was generally well-tolerated at all doses and demonstrated comparable resultsthe mid-teens to those observed with sodium polystyrene sulfonate. Other fecal electrolytes were monitored during the study and no unexpected changes were observed; in particular, fecal magnesium remained unchanged from baseline. We currently expect to begin a Phase 3 clinical study with RDX022 in the second half of 2016.20%.

Utilizing our proprietary drug discovery and design platform, we are pursuing other internal discovery and lead-development programs that are currently in the research phase.

OUR PROPRIETARY DRUG DISCOVERY AND DESIGN PLATFORM

Our platform, comprised of proprietary know-howIn line with our overall strategy and drug discovery and design tools, provides us with a competitive advantage in drug development. This platform enables us, in a rapid and cost-efficient manner,transition to discover and design novel drug candidates that work exclusively in the GI tract to treat GI and cardio-renal diseases. By targeting receptors and transporters localized in the GI tract, we can modulate certain important functions of the gut, such as absorption of specific nutrients and minerals, or the gut’s various hormonal functions, to treat and prevent diseases while avoiding systemic toxicities.

The pillars offocus solely on our drug discovery and design platform include the following:

OUR STRATEGY

We are a biotechnology company with a clinical pipeline of drug candidates in the fields of GI and cardio-renal diseases. We are currently advancing the clinical development of our two product candidates, tenapanor and RDX022, and we currently expect to file an IND for RDX009 in the second half of 2016.

Our goal is to use our proprietary drugunique discovery and design platform to discover new minimally-systemic drug candidates that preventhelp 

elucidate first-in-class mechanisms of action, as with tenapanor, and treat important diseases in these same therapeutic areas of GI and cardio-renal diseases. To date, all ofto inform preclinical experiments to help advance our drug candidates have resulted fromproduct candidates. We also use our internal research.

If our drug candidates are approved for marketing byplatform to further support the U.S. Food and Drug Administration, or FDA, we expect to participate in thepotential commercialization of our programs, which is valuable to us and future partners. We believe that our platform, and early pipeline, represent additional collaborative opportunities, market potential and downstream value-creation.

Using our platform, we have been able to discover targets found in the GI tract that regulate important processes in the body and design products candidates that act upon those targets to take advantage of the gut’s ability to communicate with other organs. Our platform integrates two critical concepts: (i) our own specialty-based sales force, initially targeting gastroenterologistsproprietary chemistry capabilities that enable us to design and nephrologists.

optimize gut-restricted compounds that can provide a higher margin of safety than systemically absorbed compounds, and (ii) our stem cell-based translational technology called the Ardelyx Primary Enterocyte and Colonocyte Culture System, or APECCS, that enables us to discover targets in the GI tract which control health and disease processes, to optimize drug candidates and to understand their mechanisms of action. Our executive management team, and in particular our President and Chief Executive Officer, Michael Raab, has extensive experience in developing and commercializing therapeutic drugsplatform can be applied across the entire GI tract, allowing for the CKD and ESRD markets, and we expectbroadest evaluation of disease targets to leverage this expertise in a manner that will allowdevelop medicines optimized for specific diseases. The predictive ability of our platform enables us to create and retain significant value from our marketed products.better assess, at a very early stage, the potential for small molecule compounds to treat specific diseases.

OUR PRODUCT PIPELINE

Tenapanor: A New Approach for Treating Hyperphosphatemia in ESRD Patients on Dialysis

The following table summarizes key information aboutlead product candidate in our product candidates as of December 31, 2015:

Tenapanor

Tenapanorrenal portfolio is a minimally-systemic small molecule that acts locally in the GI tract to inhibit the sodium transporter NHE3 and reduce sodium and phosphorus uptake from the gut. In human studies of orally- administered tenapanor, the drug was detected in the blood in only 0.7% of more than 3,000 collected serum samples, and even in those, at very low levels (< 1.5 ng/mL) confirming that tenapanor is minimally-systemic. We have evaluated tenapanor in fourteen human clinical studies in over 1,000 individuals to date. We are currently evaluating tenapanor for the treatment of constipation and pain in IBS-C patients and for the treatmenthyperphosphatemia, or high levels of hyperphosphatemiablood phosphorus, in ESRD patients.

Tenapanor for treating IBS-C

IBS-Cpatients on dialysis. Hyperphosphatemia is a GI disorder in which abdominal pain or discomfort is associated with constipation, which significantly affects the health and quality of life of affected patients. In a recent study led by Dr. Joel J. Heidelbaugh (published in 2015), over 50% of IBS-Csignificant problem among dialysis patients rated their pain, constipation and straining as being “extremely bothersome.” In the same study, GI symptoms led to an average 4.9 days of “disrupted productivity” and 0.8 days of missed work per month. Additionally, IBS-C led to over 50% of patients seeking physician care in the past 12 months and over a third were “a little or not at all satisfied” with their physician care. It is currently unknown what causes IBS-C. There is no specific test or biomarker for IBS-C and therefore, its presence is diagnosed by symptoms and by eliminating other disorders. IBS-C is very similar to chronic constipation and it is clinically distinguished by a significant pain component.

Clinical data supporting tenapanor in IBS-C

We conducted a Phase 2b clinical trial in IBS-C patients and announced results from that study in October 2014. The clinical trial was a randomized, double blind, placebo-controlled, multi-center study to evaluate the safety and efficacy of three dose levels of tenapanor in 371 subjects with IBS-C as defined by the Rome III criteria and who had active disease as determined during a two-week screening period. Subjects who qualified

and who were randomized into the study received 5, 20, or 50 mg of tenapanor or placebo twice daily for 12 consecutive weeks. At the end of this treatment period, subjects were followed for an additional 4 weeks. The results were reported on an intent-to-treat basis.

The primary endpoint, CSBM responder rate, was achieved in 60.7% of patients receiving tenapanor 50 mg twice daily versus 33.7% receiving placebo (p<0.001). A CSBM responder was defined as a patient who had an increase of greater than or equal to one CSBM from baseline during 6 out of 12 weeks. We also measured a more stringent CSBM response where a responder was defined as a patient who an increase of greater than or equal to one CSBM from baseline and had three or more CSBMs per week during 9 out of 12 weeks. The CSBM 9 of 12 week responder rate was achieved in 23.8% of patients receiving tenapanor 50 mg twice daily versus 7.9% receiving placebo (p<0.004).

An abdominal pain responder was achieved in 65.5% of patients receiving tenapanor 50 mg twice daily versus 48.3% receiving placebo (p<0.026). An abdominal pain responder was defined as a patient who experienced at least a 30% decrease in abdominal pain from baseline for 6 of 12 weeks. We also measured a more stringent abdominal pain responder rate where a responder was defined as a patient who experienced at least a 30% decrease in abdominal pain from baseline for 9 of 12 weeks. For this more stringent abdominal pain measurement, the abdominal pain 9 of 12 responder rate was achieved in 48.8% of patients receiving tenapanor 50 mg twice daily versus 31.5% receiving placebo (p<0.022).

The overall responder rate, or dual composite endpoint percent, was achieved in 50% of patients receiving tenapanor 50 mg twice daily versus 23.6% receiving placebo (p<0.001). An overall responder was defined as a patient who was a CSBM responder and an abdominal pain responder during the same week for 6 of 12 weeks. We also measured a more stringent overall responder rate where a responder was defined as a patient who was both a CSBM responder and an abdominal pain responder during the same week for 9 of 12 weeks. The overall 9 of 12 week responder rate was achieved in 20.2% of patients receiving tenapanor 50 mg twice daily versus 6.7% receiving placebo (p<0.01).

Most other secondary endpoints measured also demonstrated significant improvements for patients receiving 50 mg tenapanor twice daily compared to placebo-treated patients.

A dose response relationship among all doses was observed in the primary endpoint, as well as in most secondary endpoints, although statistical significance was not achieved at the 5 mg or 20 mg doses. Additionally, the activity of tenapanor was maintained throughout the entire 12-week treatment period.

Tenapanor was well-tolerated in these patients, and the safety results were consistent with those observed in previous tenapanor trials. The most common adverse events at 50 mg twice daily (greater than or equal to 5%) that occurred more frequently in tenapanor-treated patients compared to placebo-treated patients were diarrhea at 11.2% vs. 0%, and urinary tract infections at 5.6% vs. 4.4%. Overall rates of discontinuation due to adverse events were 4.5% for the tenapanor-treated patients (50 mg twice daily) and 3.3% for the placebo-treated patients. Based on the analysis of plasma samples tested as part of the study, the minimally-systemic nature of tenapanor was confirmed.

In the fourth quarter of 2015, we initiated two pivotal Phase 3, randomized, placebo-controlled clinical trials evaluating tenapanor in IBS-C patients. We expect to enroll approximately 600 patients in each trial, and we currently expect results from these two Phase 3 clinical trials in 2017. The primary endpoint in each of the trials is the 6 of 12 week overall responder rate. An overall responder is defined as a weekly responder for 6 of 12 weeks where both an abdominal pain response and a CSBM response criteria are met during the same week. An abdominal pain responder is defined as a patient with a 30% or greater reduction in average weekly worst abdominal pain compared to baseline during the week, and a CSBM responder is defined as a patient who has an increase of one or more in average weekly CSBMs compared to baseline during the week. We are also evaluating other endpoints in these studies, including CSBM and abdominal pain responder rates for 6 of 12 weeks as well as for 9 of 12 weeks, abdominal symptoms and other clinically relevant endpoints.

The IBS-C market opportunity

Numerous treatments exist for the constipation component of IBS-C, many of which are over-the-counter. We are aware of two prescription products marketed for IBS-C, Linzess (linaclotide) marketed by Ironwood Pharmaceuticals and Allergan and Amitiza (lubiprostone) marketed by Sucampo and Takeda. In Phase 3 clinical trials of Linzess in IBS-C patients, up to 20% more patients receiving Linzess than placebo reached the primary endpoint, overall responder rate, indicating a significant response during 6 out of 12 weeks of treatment. In these studies, Linzess caused diarrhea in up to 17% more patients than placebo.

We believe that tenapanor may offer a significant benefit over currently marketed drugs like Amitiza and Linzess, due in part to the potential to adjust the dose and/or dose frequency of tenapanor in order to optimize its efficacy and minimize diarrhea. The data we have generated in both animal and human studies have suggested that the effect of tenapanor for the treatment of IBS-C can be modulated by adjusting its dose and dose frequency.

Based on reports in the literature regarding the prevalence of IBS in the U.S. population and the percentage of individuals who have IBS-C as opposed to other forms of IBS, we estimate that approximately 1.4% of the U.S. population has IBS-C, or about 4.4 million individuals, and that approximately 1.0 million of those patients have been diagnosed with IBS-C. Additionally, we estimate there are about 6.6 million IBS-C patients in Europe and about 3.4 million in Japan.

Tenapanor for treating hyperphosphatemia in ESRD patientsworldwide.

CKD is the progressive deterioration of renal function that can occur over several months or years. The symptoms of worsening kidney function are nonspecific, and can include having less energy, reduced appetite, dry itchy skin, swollen feet and ankles or generally just not feeling well. If the deterioration continues and is not halted by either changes in lifestyle or with the assistance of pharmacological intervention, the disease will likely cause significant cardiovascular morbidity, and can progress to ESRD, the final stage of CKD, where kidney function will be lost entirely.

Current management of ESRD includes hemodialysis and peritoneal dialysis as a means to filter toxins from the blood once kidneys have failed. Unless this intervention occurs, kidney failure results in the accumulation of waste products that may ultimately cause death. Hemodialysis, the most common form of dialysis, generally requires a patient to visit a dialysis center at least three times per week for a three- to five-hour session, significantly reducing quality of life.

Phosphorus, a vital element required for most cellular processes, is present in almost every food in the Western diet, and, in individuals with normal kidney function, any excess dietary phosphorus is efficiently removed by the kidneykidneys and excreted in urine. In adults with functioning kidneys, normal serum phosphorus levels are 2.62.5 to 3.84.5 mg/dL. With kidney failure, elevated phosphorus becomes harmful and is diagnosed as hyperphosphatemia when serum phosphorus levels are greater than 5.0 mg/dL. Although patients with ESRD rely on dialysis to eliminate harmful agents, phosphorus is not readily removed by the procedure and other means of managing phosphorus levels must be employed.

In ESRD patients, excess levels of phosphorus have been shown to lead to an increase in cardiovascular disease risk, as well as increases in serum FGF-23,FGF‑23, an important serum endocrine hormone that regulates phosphorus metabolism,regulator of phosphate and vitamin D metabolism. Highly elevated levels of FGF23 is an independent risk factor for adverse cardiac clinical outcomes as well as the development of secondary hyperparathyroidism, or SHPT, marked by elevated parathyroid hormone, also known as secondary hyperparathyroidism. These endocrine changes in ESRD patients are a concern as elevated parathyroid hormone leads to the development ofhormone. SHPT is associated with renal osteodystrophy, a condition of abnormal bone growth characterized by brittle bones.

Since dialysis is unable to efficiently eliminate excess phosphorus, ESRD patients are put on restrictive low phosphorus diets and are currently prescribed medications called phosphate binders, the only pharmacologic interventions currently marketed for the treatment of hyperphosphatemia. Binders are a collection of drugs whose function is

to bind, or absorb,Phosphate binders act by binding dietary phosphorus and arecommonly need to be taken in conjunction with meals and snacks. They include calcium, iron or lanthanum, a rare-earth metal, which bind to and precipitate with dietary phosphate in the GI tract. The goal of these elemental phosphorusphosphate binders is for patients to eliminate, 

through their stool, the precipitated phosphorus in their stool. A limitationthat comes from the food they ingest. Phosphate binders have a number of this approach is the systemic excess absorption of calcium, iron or lanthanum, resulting in side effects and other unintended consequences for ESRD patients.limitations, including:

Safety and tolerability have also been significant concerns with many approved phosphate binders, with side effects that include long-term vascular calcification with calcium-based binders and iron-overload with iron-based binders. The more common side effects of certain approved phosphate binders include long-term vascular calcification,GI-related adverse events such as nausea, and vomiting, diarrhea, or constipation and ileus or disruption of the normal propulsive ability of the GI tract.dyspepsia as well as hypercalcemia for calcium-based binders and discolored feces for iron-based binders.

ESRD patients, take on average 10-14 oral medications each day, and theywho generally are severely restricted in their fluid intake. In addition, to control their serum phosphorus, their phosphate binder-related pill burden is significant, typically consisting of nineintake, are prescribed as many as 12 or more phosphate binder pills a day.per day, among other medications. The amount of phosphatephosphorus a binder can remove is limited by its binding capacity, and therefore, increasing the dose, and thereforehence the pill burden, of the binder is the only way to increase the amount of phosphatephosphorus being bound and excreted. As a result of pill burden and mass, as well as a number of side effects, prescribed phosphate binder doses are intolerable for many patients.

Clinical data supporting tenapanor in hyperphosphatemia

In February 2015, we announced results frompatients, leading to a Phase 2b clinical trial evaluating tenapanor for the control of hyperphosphatemia in ESRD patients. This Phase 2b trial was a randomized, double blind, placebo-controlled, multi-center, international study evaluating the safety and efficacy of six dose levels of tenapanor (3 and 30 mg once daily, and 1, 3, 10, and 30 mg twice daily) in 161 ESRD patients with hyperphosphatemia. The primary efficacy endpoint was the change from baseline of serum phosphate levels to the endlack of treatment adherence and the endpoint was analyzed using an analysis of covariance model (ANCOVA). The study met its primary endpoint by demonstrating a statistically significant dose-related decrease in serum phosphate levels for tenapanor-treated patients compared to patients receiving placebo (p=0.012).compliance.

The Effect of Tenapanor on Serum Phosphate in ESRD Patients with Hyperphosphatemia

As shown in the table, a dose-response relationship was observed in the primary endpoint and twice daily dosing had better pharmacodynamic activity than once daily dosing.

As expected, due to its pharmacological actions, the most frequent adverse event was diarrhea. The rate of diarrhea and the discontinuation rate due to diarrhea at the highest doses were higher than expected based on previous clinical trials. Higher discontinuations rates due to diarrhea were observed primarily in the 30 mg once daily and 30 mg twice daily dose groups. There were no other notable gastrointestinal adverse events that appeared to be tenapanor related. The overall safety profile remains consistent with that observed in previous tenapanor trials in this patient population.

Phase 2b ESRD Hyperphosphatemia: Discontinuations Due to Adverse Events

In December 2015, we initiated a Phase 2b clinical trial to evaluate the optimal dosing regimen forWe are developing tenapanor for the treatment of hyperphosphatemia in ESRD patients on dialysis, as we believe it has the potential to address certain of the key limitations of current treatments and we expectoffer a completely new mechanism of action. If approved, tenapanor would be the first small molecule/non-binder approach to receive results from this trialtreating hyperphosphatemia, with a unique mechanism of action that acts by inhibiting, or blocking, the NHE3 transporter in the second halfGI tract to reduce the absorption of 2016.

dietary sodium. When tenapanor blocks the NHE3 sodium transporter in the GI tract, it reduces the absorption of dietary sodium, resulting in an increase in protons within the cells. This increase in protons causes a selective reduction in phosphate uptake by tightening junctions or pores that are involved in the regulation of phosphate homeostasis, which then limits the amount of dietary phosphate that can pass from the gut into the blood. We have not observed this impact on other ions, nutrients or macromolecules in our clinical trials. We have submitted a manuscript for publication of this mechanism in a scientific peer-reviewed journal.

This unique mechanism of action allows tenapanor to be active in many patients at a dose of 10mg to 30mg twice daily as opposed to the multiple gram quantities per day required of the phosphate binders. Over the course of a week, the amount of tenapanor required would be less than 500mg, or a total of 14 small pills, whereas the amount of phosphate binder required, based on package inserts, would be 10 to 30 grams, or up to 64 large pills, depending on the phosphate binder. We believe this significant pill burden advantage will result in better adherence and compliance which could lead to more consistent efficacy in ESRD patients on dialysis.

Tenapanor has been specifically designed thisto work exclusively within the GI tract, thereby significantly reducing the amount of drug that is absorbed into the bloodstream and the potential side effects that could occur. In human studies of orally-administered tenapanor, the drug was detected in the blood in less than 1% in thousands of collected serum samples, and even in those, at very low levels (< 1.5 ng/mL). We have evaluated tenapanor across 20 clinical studies in over 2,500 individuals to date.

Clinical data supporting tenapanor in hyperphosphatemia

In February 2017, we announced data from our first Phase 2b3 clinical trial and the statistical analysis plan so that, assuming positive results, there is potential that the FDA may agree that this trial could be considered the first of two well-controlled studies to support an NDA forevaluating tenapanor for the treatment of hyperphosphatemia in ESRD patients.patients on dialysis.

SizeThe Phase 3 trial was an eight-week, double-blind, randomized trial, with a four-week placebo-controlled randomized withdrawal period. We enrolled a total of 219 ESRD patients with hyperphosphatemia who are on dialysis. Enrolled patients were randomized evenly into three arms, in which all groups received tenapanor for eight weeks.

Tenapanor was administered at doses of 3 mg or 10 mg twice-daily and in a dose-titration arm starting at 30 mg twice-daily with the option to down-titrate once a week during the first four weeks to 20, 15, 10 and 3 mg twice-daily, based on GI tolerability. After the end of the eight-week treatment period, patients were re-randomized 1:1 to either remain on their current tenapanor dose or switch to placebo for a four-week, placebo-controlled, randomized withdrawal period.

The primary endpoint of the trial was the difference in change in serum phosphorus between the pooled tenapanor-treated patients and placebo-treated patients from the end of the eight-week treatment period to the end of the four-week randomized withdrawal period, in the responder population. The responder population, which was reviewed by the FDA, is defined as patients who demonstrate a greater than or equal to 1.2 mg/dL decrease in serum phosphorus from baseline during the initial eight-week treatment period.

The study demonstrated a statistically significant difference in serum phosphorus levels from the end of the eight-week treatment period to the end of the four-week randomized withdrawal period between the tenapanor-treated group and the placebo-treated group in the responder patient population (mean -1.01 mg/dL, median of -1.3 mg/dL) and met its primary endpoint (95% confidence interval, -1.44, -0.21, LSmean -0.82 mg/dL, p=0.01). The responder population (n=80 out of 164) had a mean reduction in serum phosphorus from baseline to the end of the eight-week treatment period of 2.56 mg/dL, with a reduction of up to 5.7 mg/dL. Notably, in this group, 33% of patients had a reduction in serum phosphorus of greater than 3 mg/dL.

Tenapanor was well-tolerated in the trial. In the eight-week treatment period, the only adverse event that affected more than five percent of patients treated with tenapanor was diarrhea (39%), a patient-reported side effect of loosened stool or increased frequency in bowel movements regardless of magnitude. In the four-week randomized withdrawal period, there was a diarrhea rate of 1.2% for patients treated with tenapanor compared with 2.4% on placebo. Treatment discontinuations due to diarrhea for patients on tenapanor was 7.8% (n=17). There were no discontinuations due to diarrhea in the randomized withdrawal period.

In order to fully assess GI tolerability, patients used an eDiary to record the frequency of daily bowel habits, as well as stool form using the Bristol Stool Form Scale, or BSFS. During the eight-week treatment period, there was an average 0.4 per day increase in bowel movement frequency from baseline, and during the four-week randomized withdrawal period, there was an average 0.29 per day increase as compared to placebo. Average bowel movement frequency was within the normal range in all groups. During the eight-week treatment period, there was an average 0.87 point increase in BSFS from a baseline score of 4.2, out of a maximum of seven, where seven is liquid stool. During the four-week randomized withdrawal period, there was an average 0.7 point difference in BSFS between placebo (4.4) and tenapanor treatment (5.1).

We have initiated a second Phase 3 study of tenapanor for the treatment of hyperphosphatemia in ESRD patients on dialysis.  The study's design, shown in the figure, will include a 26‑week open-label treatment period, with a 12-week randomized withdrawal period followed by an additional 14‑week safety extension. Results from this study are expected in 2019. We currently intend to build our own sales and marketing organization to market and sell tenapanor for hyperphosphatemia in the United States.

The hyperphosphatemia market

Phosphate binders are the only pharmacologic interventions currentlydrugs marketed for the treatment of hyperphosphatemia. Calcium-based binders are the least expensive option to treat hyperphosphatemia. In hemodialysis patients, sevelamer has a 35% patient share versus 45% for calcium-based binders, 15% for lanthanum and 12% for iron-based binders.hyperphosphatemia in ESRD patients. The various types of phosphate binders commercialized in the United States include the following:

Generic sevelamer was expected to enter the U.S. market in early 2014 after expiration of Sanofi’s patent, but as of early 2016, no generic sevelamer has yet been approved. Generic sevelamer was approved, however, in certain jurisdictions in Europe in 2015.

Each of these agents has certain limitations. Calcium carbonate and calcium acetate can cause long term vascular calcification.

Lanthanum carbonate (Fosrenol) entered the market in 2004 as an alternative to calcium and aluminum based agents, but nephrologists’ concerns about the long term toxicity from the absorption of metals such as lanthanum and its GI side effect profile have limited its market penetration. Sevelamer hydrochloride (Renagel) is an acidic formulation of sevelamer that has been linked with worsening of metabolic acidosis in patients. Sevelamer carbonate (Renvela) was developed as an improved formulation of sevelamer to reduce incidence of acidosis. The active ingredient of both products, sevelamer, is associated long-term with vomiting (22%), nausea (20%), diarrhea (19%), dyspepsia (16%), abdominal pain (9%), and flatulence (8%).

Ferric citrate (Auryxia), an iron-based phosphate binder, was approved by FDA in September 2014. While iron is often deficient in ESRD patients because of CKD-associated anemia and lack of sufficient dietary iron, the FDA has required Auryxia to add a warning of iron-overload in the label.

The hydrochloride form of sevelamer, Renagel, was launched in the United States by Genzyme Corporation in 1998 prior to its acquisition by Sanofi, and the carbonate form, Renvela, was launched in 2008. Renvela is currently priced in the United States at a cost of more than $7,000 per patient per year, Fosrenol (lanthanum carbonate) is priced at about $7,500 and calcium-based binders are approximately $900. Sevelamer is the leading phosphate binder product in the hemodialysis market with 35% patient share (versus 45% split among several calcium-based binders). Sanofi booked €935reported €922 million ($1.041.05 billion) in worldwide sales of sevelamer during 2015. The2016 and €802 million ($0.98 billion) in 2017. Generic sevelamer carbonate has been approved in certain jurisdictions in Europe since 2015 and in the U.S. patents for sevelamer expired in February 2014 and generic launch was allowed in March 2014.market since June 2017.

In addition to the currently marketed phosphate binders, we are aware of at least two other binders in development, including fermagate (Alpharen), an iron-based binder in Phase 23 studies being developed by Opko Health, Inc., and PT20, an iron-based binder in Phase 23 being developed by PhosphateShield Therapeutics.

According to the most recent data available from the U.S. Renal Data System, in 20132015 there were 421,349444,337 patients on hemodialysis in the United States. Additionally, according to the European ERA-EDTA Registry 20122015 Annual Report and a study in 20102014 by the Japanese Society for Dialysis Therapy, there were approximately 280,000317,000 patients on hemodialysis in Europe and about 250,000255,000 in Japan. We estimate, based on phosphate binder utilization, the only approved therapies for hyperphosphatemia, that there are approximately 290,000, 225,000310,000, 250,000 and 220,000260,000 ESRD patients with hyperphosphatemia in the United States, countries in Europe and Japan, respectively.respectively, resulting in approximately 820,000 ESRD patients with hyperphosphatemia in such countries.

Because many ESRD patients with hyperphosphatemia are unable to lower serum phosphorus levels to below 5.5 mg/dL with currently marketed phosphate binders, we believe there is a significant opportunitymedical need for new agents with

new mechanisms, demonstrated efficacy, a strong safety profile, and significantly lower pill burden.

We believe that tenapanor, if approved, has the potential to have the lowest pill burden and mass among any currently marketed hyperphosphatemia drugs,products, with milligram rather than gram quantities dosed once or twice daily.quantities. In addition, we may evaluate whether tenapanor has the potential to be used in combination with phosphate binders for those patients who cannot achieve adequate phosphate control with a single agent.

RDX022Our intention is to build a United States-focused, highly efficient, specialized sales and marketing organization focused on nephrology. The nephrology market is a concentrated market strongly influenced by key opinion leaders. There were 10,083 nephrologists in the United States in 2015 and 6,620 dialysis facilities in the United States that offer in-center dialysis. Based on the experience of our management team, we believe that a specialty salesforce is appropriate for treating hyperkalemia

this marketplace. We are developing RDX022believe that tenapanor for the treatment of hyperkalemia. RDX022 is our proprietary oral, non-absorbed potassium-binder. It based on polystyrene sulfonate,hyperphosphatemia could represent a well-knownmarket opportunity of between $500 million and well-characterized polymer. We have made numerous improvements to the polymer by engineering into RDX022 several key physical and chemical modifications in an effort to improve various properties. We have filed a patent application covering the composition of matter for these modifications.

Clinical data supporting RDX022 in hyperkalemia

In January 2016, we announced results from an open-label pharmacodynamic study of RDX022 in healthy adult volunteers. The study consisted of a two-day treatment-free baseline period and a four-day treatment

period. The study included four cohorts, and in each cohort 12 subjects received RDX022 and three subjects received a similar dose of sodium polystyrene sulfonate, or SPS for a total of 60 subjects. RDX022 was administered at 4.6 g BID (9.2 g/day), 6.9 g BID (13.8 g/day), 4.6 g TID (13.8 g/day) and 9.2 g TID (27.5 g/day), and resulted in a mean increase of fecal potassium from baseline of 888 mg/day, 1,791 mg/day, 1,408 mg/day, and 1,670 mg/day, respectively. RDX022 was generally well-tolerated at all doses and demonstrated comparable results to those observed with SPS. Other fecal electrolytes were monitored during the study and no unexpected changes were observed; in particular, fecal magnesium remained unchanged from baseline.

Sodium is currently used as a counter-ion in SPS products marketed$700 million in the United StatesStates.

As a first-in-class treatment, and certain other products under development. We formulated RDX022as the first non-binder option with a calcium counter-ion, rather thanwell-tolerated safety profile, we believe tenapanor could address the significant pill burden challenges and intolerability that patients experience with today’s binder treatments. After the second Phase 3 study readout, if successful, we intend to submit a sodium counter- ion, as adding sodiumNew Drug Application to the daily intakeFDA in 2019 and would plan for a potential launch 2020.

To bring tenapanor to patients outside the United States, we intend to establish strategic collaborations with industry leading pharmaceutical companies with established commercial infrastructures. In 2017, we entered into two collaboration partnerships, and the revenues recorded from those collaboration partnerships in 2017 accounted for more than 10% of total revenues recorded during the year ended December 31, 2017.

License agreement with KHK

In November 2017, we entered into a license agreement (“KHK License Agreement”) with KHK under which we granted KHK an exclusive license to develop and commercialize tenapanor in Japan for the treatment of cardiorenal diseases and conditions, excluding cancer (“KHK Field”). We retained the rights to tenapanor outside of Japan, and also retained the rights to tenapanor in Japan for indications other than those in the KHK Field. Pursuant to the KHK License Agreement, KHK is responsible for all of the targetdevelopment and commercialization costs for tenapanor in the KHK Field in Japan.

Under the KHK License Agreement, we are responsible for supplying the tenapanor drug product for KHK’s use in development and during commercialization until KHK has assumed such responsibility. Additionally, we are responsible for supplying the tenapanor drug substance for KHK’s use in development and commercialization throughout the term of the KHK License Agreement, provided that KHK may exercise an option to manufacture the tenapanor drug substance under certain conditions.

Under the terms of the KHK License Agreement, we have received a $30.0 million upfront payment and are eligible to receive up to an additional $130.0 million in development and commercialization milestones, based upon currency exchange rates as of the effective date of KHK License Agreement.

We are also eligible to receive royalties based on aggregate annual net sales of the licensed products at a high teen percentage, subject to certain single digit reductions under certain circumstances described in the KHK License Agreement.

The KHK License Agreement will continue until all of KHK’s applicable payment obligations under the KHK License Agreement have been performed or have expired, or the agreement is earlier terminated. Under the terms of the KHK License Agreement, we and KHK each have the right to terminate the agreement for material breach by the other party. In addition, KHK may terminate the agreement for convenience; for certain safety reasons or if certain primary endpoints under an applicable development plan are not met despite KHK’s commercially reasonable efforts and KHK reasonably determines that it cannot obtain regulatory approval. KHK may also terminate the agreement if certain pivotal clinical trials conducted by us do not meet their primary endpoints. We may terminate the KHK License Agreement if KHK challenges any patents licensed to KHK under the agreement.

License agreement with Fosun

In December 2017, we entered into a license agreement (the “Fosun License Agreement”) with Fosun Pharma under which we granted Fosun Pharma an exclusive license to develop and commercialize tenapanor in China for the treatment, diagnosis or prevention of (i) irritable bowel syndrome with constipation and chronic idiopathic constipation, (ii) hyperphosphatemia related to chronic kidney disease and (iii) other diseases or conditions for which we obtain marketing approval in either the US or China (collectively, “Fosun Field”). The Fosun Field excludes the treatment of cancer. We retained the rights to tenapanor outside of China, and also retained the rights to tenapanor in China for indications other than those in the Field. Pursuant to the terms of the Fosun License Agreement, Fosun Pharma is responsible for all of the development and commercialization costs for tenapanor in the Fosun Field in China.

Under the terms of the Fosun License Agreement, we are responsible for supplying the tenapanor drug product for Fosun Pharma’s use in development and during commercialization until Fosun Pharma has assumed such responsibility. Additionally, we are responsible for supplying the tenapanor drug substance for Fosun Pharma’s use in development and commercialization throughout the term of the Fosun License Agreement.

Under the terms of the Fosun License Agreement, we received an upfront payment of $12 million and are eligible to receive additional milestones of up to $113 million in the aggregate, as well as tiered royalty payments on aggregate net sales ranging from the mid-teen percent to twenty percent, subject to certain reductions under certain circumstances, as described in the Fosun License Agreement.

The Fosun License Agreement will continue until all of Fosun Pharma’s applicable payment obligations under the License Agreement have been performed or have expired, or the agreement is earlier terminated. Under the terms of the Fosun License Agreement, we and Fosun Pharma each have the right to terminate the agreement for material breach by the other party or in the event of insolvency by the other party. In addition, Fosun Pharma may terminate the agreement for convenience and we may terminate the agreement if Fosun Pharma challenges any patents licensed to it under the agreement.

RDX013 Program: Small Molecule for Treating Hyperkalemia

RDX013 is our novel, small molecule program for the potential treatment of hyperkalemia. Our RDX013 approach works by tapping into the GI tract’s natural ability to secrete potassium into the lumen of the gut to reduce serum potassium levels. This mechanism differs significantly from the potassium binders currently on or approaching the market. For a potassium binder to work, it must be present when dietary potassium is ingested so that the agent can bind the potassium and prevent its absorption in the gut. This results in the need for large quantities of binder in order to bind the large amounts of potassium in the diets of most individuals. In contrast, we observed in our preclinical models that a small amount of RDX013 could cause potassium to be secreted into the lumen of the gut. In this way, we believe that RDX013 may have the potential to lower serum potassium whether or not potassium is present in the diet and could result in a very low pill burden, potentially allowing better patient population runs countercompliance, longer-term use and potentially better efficacy than potassium binders. As described below, certain medications commonly administered to best clinical practice. In patients with CKD and/or HF,heart failure can also cause hyperkalemia. With the standardsuccessful development of care is a low-sodium diet as sodium can contributean effective potassium secretagogue to fluid overload and edema, a common experience for these patients. In addition, excess sodium diminishes the beneficial effects of blood pressure drugs that inhibit the renin-angiotensin-aldosterone system, or RAAS. We have also improved both the physical properties of polystyrene sulfonate and the formulationtreat hyperkalemia in a manner that we expect may lead to improved patient adherence and compliance. Notably, in a single center, randomized, crossover study to evaluate various oral formulations of RDX022 in healthy subjects, RDX022 consistently outperformed SPS in all aspects of the taste assessments, including mouth feel, texture and flavor.

We currently expect to initiate a Phase 3 clinical trial for RDX022 in the second half of 2016. The Phase 3 clinical trial will enroll patients with CKD, with or without HF, who are taking RAAS inhibitors and are diagnosed with hyperkalemia, a common side effect that occurs in patients taking RAAS inhibitors. Based on discussions with the FDA,small, convenient pill format, we believe we will be ableour RDX013 approach may allow nephrologists and cardiologists with an opportunity to submit an application for RDX022 undertreat hyperkalemia chronically without reducing the 505(b)(2) regulatory pathway.

Sizedose of the hyperkalemia marketthese medications.

Hyperkalemia is generally defined as the presence of blood potassium levels greater than 5.0mEq/5.0 mEq/L. Normal levels are 3.5 to 5.0 mEq/L. When hyperkalemia is severe, or above 7.0mEq/7.0 mEq/L, there is a significantly increased risk of death because of the potential for heart conductance problems.

Hyperkalemia can be caused by a variety of sources.issues. Kidney disease can result in the build-upelevation of potassium in the blood. Also, certainCertain drugs such as the common blood pressurehypertension medications known as RAAS inhibitors, or inhibitors ofwhich inhibit the renin-angiotensin-aldosterone system, can cause hyperkalemia. As a result, the dosage of RAAS inhibitors though quite effective for controlling blood pressure, aremust often be significantly reduced in patients suchwhose potassium levels are elevated (such as in those with CKD and HF whose potassium levels are elevated becauseheart failure). Because of the fearrisk of hyperkalemia, several published guidelines have suggested that elevated potassium can cause significantly worse problems thanphysicians should reduce and

possibly discontinue RAAS inhibitors in order to manage the risk of hyperkalemia in CKD and heart failure patients. The alternative medications used to control hypertension, including sudden cardiac arrestdiuretics and calcium channel blockers, are less effective than RAAS inhibitors, particularly in patients with failing kidneys and severe cases.hypertension. According to the 2015 publication Market Dynamix: Hyperkalemia, released by Spherix Global Insights, U.S. cardiologists reported that of the patients who would benefit from RAAS inhibition, up to 38% of patients with heart failure and up to 55% of patients with both heart failure and CKD are being administered a sub-optimal dose or none at all. Nephrologists reported that at least one-third of patients who would benefit from RAAS inhibition receive a sub-optimal dose or none at all. We believe there is clearly a strong medical need for new medications that control hyperkalemia in order to allow for optimal use of RAAS inhibitors to control hypertension in these patient populations.

The hyperkalemia market

Of the people with CKD and/or heart failure in the United States, we estimate that there are approximately 2.1 million people who also have occurrences of hyperkalemia. According to a retrospective observational study conducted in 2005 of a national cohort of 246,000 veteranspatients cared for in the Veterans Health Administration, about 21% and 42% of patients with CKD Stage 3b and Stage 4, respectively, had a hyperkalemic event during a 12-month period, suggesting that hyperkalemia affects about 900,000 individuals with CKD Stage 3b or Stage 4 in the United States. According to the United States Renal Data System 2014 Atlas of CKD & ESRD, over 50% of CKD Stage 3b and Stage 4 patients are prescribed RAAS inhibitors because of their efficacy in controllingto control hypertension and success in slowingto slow the clinical course of CKD.

Additionally, according to the American Heart Association, 5.7 million Americans arenumber of adults in the U.S. living today with heart failure.failure is about 6.5 million, based on data collected in the National Health and Nutrition Examination Survey, which is taken in stages over multiple years. Our proprietary research suggests that up to 16%, or approximately 900,000,1,000,000, of these patients had hyperkalemia during a 12-month period. Over half of heart failure patients are prescribed RAAS inhibitors.

Despite the success of RAAS inhibitors in both of these populations, several published guidelines have suggested that physicians should reduce and possibly discontinue RAAS inhibitors in order to manage the risk of hyperkalemia in CKD and heart failure patients. The alternative medications used to control hypertension, including diuretics and calcium channel blockers, are significantly less effective than RAAS inhibitors, particularly in patients with failing kidneys and severe hypertension. According to the publication Market

Dynamix: Hyperkalemia recently released by Spherix Global Insights, U.S. cardiologists reported that of the patients who would benefit from RAAS inhibition, up to 38% of patients with heart failure and up to 55% of patients with both heart failure and CKD are being administered a sub-optimal dose or none at all, and nephrologists reported that at least one-third of patients who would benefit from RAAS inhibition receive a sub- optimal dose or none at all. We believe there is a strong medical need for new medications that control hyperkalemia in order to allow for continued use of RAAS inhibitors to control hypertension in these patient populations.

An additional market not currently addressed by any product on the market is hyperkalemia in ESRD patients. Our proprietary research also suggests that up to 48% of patients on dialysis have at least one intervention for hyperkalemia during a 12-month period despite being dialyzed, resulting in a 7% mortality rate. This suggests up to 200,000 patients with ESRD thatin the U.S. could benefit from an agent that treats hyperkalemia.

We are aware of at least two drugs approaching or on the market for the treatment of hyperkalemia. Veltassa (patiromer FOS), an oral, polymer-based potassium binder, was approved for marketing by the FDA in October 2015 and was just recently commercially launched by Relypsa. Relypsa, which was acquired by Galenica AG for $1.5 billion in September 2016. However, according to a 2017 survey of more than 200 nephrologists and cardiologists, conducted by Spherix Global Insights, about half of those surveyed note that, even with Veltassa available, there remains a high unmet need for new treatments for hyperkalemia.

Additionally, a new drug application, orZS Pharma submitted an NDA was submitted in June 2015 for ZS-9, a sodium zirconium cyclosilicate-based oral potassium binder being developedbinder. ZS Pharma was acquired by AstraZeneca in December 2015 for $2.7 billion.

We believe that, unlike these agents which require large amounts of drug for the desired effect, RDX013 may have the potential to lower serum potassium whether or not potassium is present in the diet and could result in very low pill burden, allowing better compliance, longer-term use and potentially better efficacy than potassium binders.

If we are successful in developing RDX013 and obtaining marketing authorization from the FDA, we would expect to leverage the renal sales and marketing organization that we intend to build to support commercialization in the United States of tenapanor for treating hyperphosphatemia in dialysis patients.

Tenapanor: NHE3 Inhibitor for Treating IBS-C

In addition to its development for hyperphosphatemia, we have completed development of tenapanor for the treatment of hyperkalemia by AstraZeneca after its acquisition of ZS PharmaIBS-C and are pursuing strategic collaborations to bring it to market in December 2015.

OTHER DEVELOPMENT PROGRAMS

Other product candidatesthis indication. We have completed two Phase 3 clinical trials in our pipeline include the following:

RDX009 Program

Our focus is the discoverypatients with IBS-C (T3MPO-1 and development of minimally-systemic TGR5 agonists that stimulate GLP-1T3MPO-2) along with a long-term safety study (T3MPO-3) and GLP-2 secretion for various indications. In December 2015, we declared a development candidate for RDX009, and we currently expect to filesubmit an IND for RDX009NDA to the FDA in the second half of 2016. We are evaluating RDX009 in animal models for its effect in multiple indications.2018.

TGR5IBS-C is a receptor present onGI disorder in which abdominal pain or discomfort is associated with constipation, and which significantly impacts the membranehealth and quality of certain cells withinlife of affected patients. A study published in the American Journal of Gastroenterology in 2015, showed that over 50% of IBS-C patients rated their pain, constipation and straining as being

“extremely bothersome.” In the same study, GI symptoms led to an average 4.9 days of “disrupted productivity” and 0.8 days of missed work per month. There is no specific test or biomarker for IBS-C and therefore its presence is diagnosed by symptoms and by eliminating other disorders. IBS-C is very similar to chronic constipation and is clinically distinguished by a significant abdominal pain component.

Tenapanor is a minimally-systemic small molecule that acts locally in the GI tract to inhibit the sodium transporter NHE3 and reduce sodium uptake from the gut. Part of its mechanism to treat constipation caused by IBS-C is an osmotic effect in the intestines – water follows salt and stool is gently loosened by the body’s own fluids. In addition to this mechanism, data from nonclinical studies, which were presented in November 2017 at the American Society of Nephrology Annual Meeting, suggest that respondstenapanor reduced abdominal pain caused by IBS-C through the inhibition of TRPV-1 dependent signaling. TRPV-1, better known as the "hot chili pepper receptor," is a well-established pain target known for transmitting painful stimuli from a variety of sources including heat, protons and inflammatory molecules. Using an established rodent model of IBS-like colonic hypersensitivity, preclinical data showed that tenapanor treatment reduced visceral hypersensitivity (pain in the internal organs) and normalized colonic sensory neuronal excitability and TRPV-1 currents. Treatment with tenapanor also increased stool excretion and stool water content. In these nonclinical studies, tenapanor had a superior effect on visceral hypersensitivity than placebo or PEG, a well-known laxative not known to bile acids secretedhave an analgesic effect.

Phase 3 clinical data supporting tenapanor in response to food.IBS-C

At the end of 2017, we completed our Phase 3 program, the T3MPO program, for tenapanor for the treatment of IBS-C. This included two Phase 3 studies, T3MPO-1 and T3MPO-2, and a long-term safety extension study, T3MPO-3. In the normal physiological response, bindingdiscussion below, statistical significance is denoted by p-values. The p-value is the probability that the reported result was achieved purely by chance (e.g., a p-value <0.001 means that there is a less than a 0.1% probability that the observed change was purely due to chance). Generally, a p-value less than 0.05 is considered statistically significant.

In May 2017, we reported data from the first Phase 3 study, T3MPO-1. T3MPO-1 was a 12-week, double-blind, placebo-controlled, multi-center, randomized trial with a four-week, randomized withdrawal period conducted in a total of bile acids610 patients meeting the ROME III criteria for the diagnosis of IBS-C. Patients were randomized one to TGR5 stimulatesone to receive either 50 mg of tenapanor or placebo twice-daily. The trial included a two-week screening period, during which patients with active disease, based on bowel movement frequency and abdominal pain score recorded in a daily phone diary, were randomized into the productiontrial.

The study achieved statistical significance for the primary endpoint and seven of hormones such as glucagon- like peptides 1eight secondary endpoints. The primary endpoint, the combined responder rate for six of 12 weeks, showed that a greater proportion of tenapanor-treated patients compared to placebo-treated patients (27.0% vs 18.7%, p=0.02) had at least a 30% reduction in abdominal pain and 2 (GLP-1 and GLP-2). GLP-1 is involvedan increase of one or more complete spontaneous bowel movements, or CSBM, in maintaining insulin sensitivity and in aiding glucose and lipid metabolism. GLP-2 is involved in maintenancethe same week for at least six of the structural integrity12 weeks of the guttreatment period. The CSBM responder rate in the six of 12 weeks (defined as having an increase of at least one CSBM from baseline during a week for six of 12 weeks) did not reach statistical significance (33.9% vs. 29.4%, p=0.27); however, the abdominal pain responder rate in the six of 12 weeks (defined as having at least a 30% decrease in abdominal pain from baseline during a week for six of 12 weeks) did achieve statistical significance (44.0% vs. 33.1%, p=0.008). In the nine of 12 treatment weeks, the study achieved statistical significance for the combined responder rate (13.7% vs. 3.3%, p<0.001), in which patients must have had an increase of at least one CSBM from baseline and at least three CSBMs during a week for nine of 12 weeks as well as its growth.a 30% or greater reduction in abdominal pain for nine of the 12 weeks. In addition, for the nine of 12 weeks, the study achieved statistical significance for the individual CSBM responder rate (16.9% vs. 5%, p<0.001) and the abdominal pain responder rate (30.3% vs. 19.4%, p=0.003).

Tenapanor was well-tolerated in the study. The only adverse events observed in more than two percent of patients treated with tenapanor, as compared with placebo, were diarrhea (14.6% vs 1.7%) and nausea (2.6% vs 1.7%). The placebo adjusted discontinuation rate due to diarrhea was 5.3%.

In October 2017, we reported results from the second Phase 3 study of tenapanor for the treatment of IBS-C, T3MPO-2, a 26-week, double-blind, placebo-controlled, multi-center, randomized trial in 593 patients. Patients were

randomized one to one to receive either 50 mg of tenapanor or placebo twice-daily. The trial included a two-week screening period, during which patients with active disease, based on bowel movement frequency and abdominal pain score recorded in a daily phone diary, were randomized into the trial.

The study achieved statistical significance for the primary endpoint and all secondary endpoints evaluated for the topline results and demonstrated the ability to normalize bowel movements. The primary endpoint, the combined responder rate for six of 12 weeks, showed that a greater proportion of tenapanor-treated patients compared to placebo-treated patients (36.5% vs. 23.7%, p<0.001) had at least a 30% reduction in abdominal pain and an increase of one or more CSBMs in the same week for at least six of the 12 weeks of the treatment period. The study achieved statistical significance for the CSBM and abdominal pain responder rates in the six of 12 weeks (47.4% vs. 33.3%, p<0.001; 49.8% vs. 38.3%, p=0.004). In the nine of 12 treatment weeks, the study achieved statistical significance for the combined responder rate (18.4% vs. 5.3%, p<0.001), in which patients must have had an increase of at least one bowel movement from baseline and at least three per week and a 30% reduction in abdominal pain for nine of the 12 weeks. In addition, for the nine of 12 weeks, the study achieved statistical significant for the individual CSBM responder rate (22.2% vs. 6.0%, p<0.001) and the abdominal pain responder rate (35.8% vs. 26.7%, p=0.015). The study also achieved statistical significance for all three durable responder endpoints, the combined responder rate (18.1% vs. 5.0%, p<0.001), CSBM responder rate (21.2% vs. 5.7%, p<0.001) and abdominal pain responder rate (34.8% vs. 26.7%, p=0.028), which are identical to the nine of 12-week responder endpoints, except the response must also occur in three of the last four treatment period weeks.

Tenapanor was well-tolerated in the T3MPO-2 study. The only adverse events observed in more than two percent of patients in the tenapanor-treated group that were also greater than placebo were diarrhea (16.0% vs. 3.7%), flatulence (3.1% vs. 1.0%), nasopharyngitis (4.4% vs. 3.7%) and abdominal distension (3.4% vs. 0.3%). The placebo adjusted discontinuation rate due to diarrhea was 5.8%.

Patients who completed T3MPO-1 and T3MPO-2 were eligible to enter T3MPO-3, our open-label, long-term safety trial where patients could continue to receive tenapanor for up to one year. In late 2017, we completed T3MPO-3 and have reported results that tenapanor had a mean compliance rate of approximately 98%, and that tenapanor was well-tolerated among the 240 patients treated. Of patients treated, 9.2% reported experiencing diarrhea, with 1.7% of patients discontinuing treatment due to diarrhea. The overall discontinuation rate in the study was 2.1%.

Based on the positive results from the T3MPO program, we are preparing to submit an NDA to the FDA to request marketing approval of tenapanor for the treatment of IBS-C in the United States.

To support the global commercialization of tenapanor for IBS-C, we are pursuing strategic collaborations to bring tenapanor to patients. In December 2017, we entered into a license agreement to provide Fosun Pharma with the exclusive rights to develop and commercialize tenapanor in China for the treatment of patients with IBS-C and hyperphosphatemia related to chronic kidney disease.

The IBS-C market

Numerous treatments exist for the constipation component of IBS-C, many of which are over-the-counter. There are three prescription products marketed for IBS-C: (i) Linzess (linaclotide), marketed by Ironwood Pharmaceuticals and Allergan, (ii) Amitiza (lubiprostone), marketed by Takeda and Sucampo, a wholly-owned subsidiary of Mallinckrodt, and (iii) Trulance (plecanatide), marketed by Synergy Pharmaceuticals.

We believe that endogenoustenapanor may offer a significant benefit over currently marketed drugs like Amitiza, Linzess and local secretionTrulance in part because of GLP-1 and GLP-2 triggered by the stimulationprofile demonstrated in our Phase 3 program, which showed best-in-class efficacy results for the 9-of-12 week combined responder rates. Within the United States, there are approximately 11 million patients that suffer that suffer from IBS-C. There is significant unmet need for prescription medications, where, according a 2015 American Gastroenterological Association report, only 1 in 4 treated patients are very satisfied with the current FDA approved treatments in IBS-C.

Other GI Programs

In addition to tenapanor for IBS-C, we have an early GI pipeline comprised of RDX8940, a minimally absorbed, oral TGR5 agonist may have significant therapeutic potential for the treatment of several conditions. An injectable, stabilized form of GLP-2, called teduglutide (Gattex), is marketed for short bowel syndromewhich we submitted an investigational new drug application, or IND, in late 2016; RDX011, our second-generation NHE3 inhibitor; and has been studied in Crohn’s disease. GLP-2 is hypothesized to work in inflammatory bowel disease, or IBD, such as Crohn’s disease and ulcerative colitis, or UC, by stimulating the repair of the gut and improving the structural integrity of gut wall that is damaged in patients with IBD. Additionally, GLP-2 and its analogs have been shown to prevent chemotherapy-induced diarrhea in animal models. Injectable stabilized GLP-1 analogs that are commercially available, such as exenatide (Byetta) and liraglutide (Victoza), are commonly used to treat type 2 diabetes, among other metabolic conditions. Additionally, injectable GLP-1 analogs are being evaluated in the treatment of NASH because they are known to improve lipid metabolism in the liver. In all of these cases, GLP-1 and GLP-2 analogs are injectable thus we believe an oral agent that can emulate these effects would be welcome.

Historically one of the limitationsour RDX023 program for the development of TGR5 agonists has been the observation with systemic compounds that stimulation of TGR5 in the gallbladder results in excess gallbladder filling, potentially increasing the risk of gallstones. Utilizing our approachgut-biased farnesoid X receptor, or FXR, agonists. While we are not currently actively developing these programs, they represent potential collaboration opportunities to design small molecules, we have created novel TGR5 agonist candidates that have extremely low systemic exposure and we have shown that these agents do not result in excess gallbladder filling in preclinical animal models.

We have selected a development candidate for the RDX009 program. This compound, in combination with a DPP-IV inhibitor, has demonstrated proof-of-concept in an animal efficacy model of IBD, and analogs of this compound have shown activity in animal models of chemotherapy-induced diarrhea and short bowel syndrome. We continue to evaluate the development candidate in several animal models of disease as we complete our pre-clinical studies with the intent of filing an IND in the second half of 2016.

RDX013 Program

Our RDX013 program is aimed at discovering and evaluating small molecule, orally-administered drug candidates that modulate the transport of potassium in the GI tract. Our agents will be designed to enhance potassium secretion or prevent potassium absorption in the colon and correct hyperkalemia disorders in CKD patients. We believe that specific potassium transporters in the intestines may serve as useful targets for our program. We believe that such agents may be used as stand-alone agents or used in combination with potassium binders to boost efficacy or to reduce the pill burden of the potassium binders. Several agents we have developed have demonstrated significant activity in animals.

RDX011 Program

We intend to leverage our knowledge of NHE3 inhibitors andsupport their effect on phosphate management as we seek to further understand tenapanor’s phosphate lowering mechanism of action. We also intend to evaluate new indications for tenapanor and other NHE3 inhibitors in order to exploit the unique capabilities and tools we have developed to modulate ion transport channels located on mucosal surfaces.continued development.

INTELLECTUAL PROPERTY

Our commercial success depends in part on our ability to obtain and maintain proprietary protection for our drug candidates, manufacturing and process discoveries, and other know-how, to operate without infringing the proprietary rights of others and to prevent others from infringing our proprietary rights. Our policy is to seek to protect our proprietary positionintellectual property by, among other methods, filing U.S. and foreign patent applications related to our proprietary technology inventions and improvementsinventions that are important to the development and implementationoperation of our business. We also rely on trade secrets and careful monitoring of our proprietary information to protect aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection.

As a normal course of business, we pursue composition-of-matter and method-of-use patents for our product candidates in key therapeutic areas. We also seek patent protection for broader structural and functional attributes of our product candidates that enable a minimally-systemic or minimally-systemic profile.

The patent positions of biopharmaceutical companies like us are generally uncertain and involve complex legal, scientific and factual questions. In addition, the coverage claimed in a patent application can be significantly reduced before the patent is issued, and its scope can be reinterpreted after issuance. Consequently, we do not know whether any of our product candidates will be protectable or remain protected by enforceable patents. We cannot predict whether the patent applications we are currently pursuing will issue as patents in any particular jurisdiction or whether the claims of our issued patents will provide sufficient proprietary protection from competitors. Any patents that we hold may be challenged, circumvented or invalidated by third parties. If third parties prepare and file patent applications in the United States that also claim technology or therapeutics to which we have rights, we may have to participate in interference proceedings in the U.S. Patent and Trademark Office, or USPTO, to determine priority of invention, which would result in substantial costs to us even if the eventual outcome is favorable to us.

The term of individual patents depends upon the legal term of the patents in countries in which they are obtained. In most countries, including the United States, the patent term is generally 20 years from the earliest date of filing a non-provisional patent application in the applicable country. In the United States, a patent’s term

may, in certain cases, be lengthened by patent term adjustment, which compensates a patentee for administrative delays by the USPTO in examining and granting a patent, or may be shortened if a patent is terminally disclaimed over a commonly owned patent or a patent naming a common inventor and having an earlier expiration date.

In addition, in the United States, the Hatch-Waxman Act permits a patent term extension of up to five years beyond the expiration of a U.S. patent as partial compensation for the patent term lost during the FDA regulatory review process occurring while the patent is in force. A patent extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, and only one patent applicable to each regulatory review period may be extended and only those claims covering the approved drug, a method for using it or a method for manufacturing it may be extended. Similar provisions are available in the European Union and certain other foreign jurisdictions to extend the term of a patent that covers an approved drug.

We may rely, in some circumstances, on trade secrets to protect our technology. Although we take steps to protect our proprietary information and trade secrets, including through contractual means with our employees and consultants, third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose our technology. Thus, we may not be able to meaningfully protect our trade secrets. It is our policy to require our employees, consultants, outside scientific collaboration partners, sponsored researchers and other advisors to execute confidentiality agreements upon the commencement of employment or consulting relationships with us. These agreements provide that all confidential information concerning the business or financial affairs developed or made known to the individual during the course of the individual’s relationship with us is to be kept confidential and not disclosed to third parties except in specific circumstances. In the case of employees, the agreements provide that all inventions conceived by the individual, and which are related to our current or planned

business or research and development or made during the normal working hours, on our premises or using our equipment or proprietary information, are our exclusive property.

NHE3 patents

Our NHE3 patent portfolio is wholly owned by us. This portfolio includes threefour issued U.S. patents, two issued Japanese patents, two issued Korean patents and one issued Mexican patent.patent in each of the following territories: Australia, China, the European Union, Mexico, and Israel. These issued patents cover the composition and methods of using tenapanor and are predicted, without extension or adjustment, to expire in 2029. We have related national patent applications pending in Europe, China, India, Israel and a number of other countries. Any patents issuing from these patent applications are also predicted without extension or adjustment to expire in 2029.

Additional U.S. and international patent applications are pending covering additional methods of using tenapanor, and composition of matter and methods of using compounds that we believe may be follow on compounds to tenapanor.

Other program patents

We have patent applications pending in the United States covering the composition of or methods of using tenapanor, or its backup compounds.

NaP2b Patents

We have a portfolio of patents and patent applications claiming the compositions and methods of using our proprietary NaP2b inhibitor compounds. NaP2b is an intestinal transporter of dietary phosphorus. Our portfolio is wholly owned by us and includes four issued U.S. patents and three allowed U.S. applications covering the composition of or methods of using our NaP2b inhibitor compounds. The issued patents, and if issued, the allowed applications are predicted to expire in 2031. Numerous related patents have issued in Europe, Hong Kong and Japan Any patents resulting from these patent applications, if issued, are also predicted to expire in 2031.

RDX022

We have filed a PCT application covering the compositions and methods of using RDX022.

RDX009

We have filed a provisional application coveringinternationally that cover the compositions and methods of using our TGR5 agonists.agonists, our FXR agonists and compounds in our RDX013 program.

MANUFACTURING

To date, we have relied upon third-party contract manufacturing organizations, or CMOs, to manufacture both the active pharmaceutical ingredient and final drug product dosage forms of our potential drug candidates used as clinical trial material. We expect that we will continue to rely upon CMOs for the manufacture of our clinical trial materials and for our own internal programs.commercial product requirements, when and if regulatory approval is received. Our license agreements with KHK and Fosun Pharma require us to supply active pharmaceutical ingredient and final drug product dosage forms of tenapanor for their use in the development of tenapanor in each of their respective territories, and we are further obligated to continue to supply active pharmaceutical ingredient to support their commercialization of tenapanor in each of their territories. We expect that we will use CMOs to satisfy our supply obligations to our collaboration partners.

GOVERNMENT REGULATION/FDA

The FDA and comparable regulatory authorities in state and local jurisdictions and in other countries impose substantial and burdensome requirements upon companies involved in the clinical development, manufacture, marketing and distribution of drugs. These agencies and other federal, state and local entities regulate research and development activities and the testing, manufacture, quality control, safety, effectiveness, labeling, storage, record keeping, approval, advertising and promotion, distribution, post-approval monitoring and reporting, sampling, and export and import of our product candidates.

In the United States, the FDA regulates drug products under the Federal Food, Drug, and Cosmetic Act, or FFDCA, and the FDA’s implementing regulations. If we fail to comply with applicable FDA or other requirements at any time during the drug development process, the approval process or after approval, we may become subject to administrative or judicial sanctions. These sanctions could include the FDA’s refusal to approve pending applications, license suspension or revocation, withdrawal of an approval, warning letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, civil penalties or criminal prosecution. Any FDA enforcement action could have a material adverse effect on us. FDA approval is required before any new unapproved drug or dosage form, including a new use of a previously approved drug, can be marketed in the United States.

The process required by the FDA before a drug may be marketed in the United States generally involves:

The preclinical and clinical testing and approval process requires substantial time, effort and financial resources, and we cannot be certain that any approvals for our product candidates will be granted on a timely basis, if at all. Nonclinical tests include laboratory evaluation of product chemistry, formulation, stability and toxicity, as well as animal studies to assess the characteristics and potential safety and efficacy of the product. The results of preclinical tests, together with manufacturing information, analytical data and a proposed clinical

trial protocol and other information, are submitted as part of an IND to the FDA. Some preclinical testing may continue even after the IND is submitted. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day30‑day time period, raises concerns or questions relating to the IND and places the clinical trial on a clinical hold, including concerns that human research subjects will be exposed to unreasonable health risks. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. A separate submission to an existing IND must also be made for each successive clinical trial conducted during product development.

Clinical trials involve the administration of the investigational drug to human subjects under the supervision of qualified investigators. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial, the parameters to be used in monitoring safety and the effectiveness criteria to be used. Each protocol must be submitted to the FDA as part of the IND.

An independent IRB or ethics committee for each medical center proposing to conduct a clinical trial must also review and approve a plan for any clinical trial before it can begin at that center and the IRB must monitor the clinical trial until it is completed. The FDA, the IRB, or the sponsor may suspend or discontinue a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk. Clinical testing also must satisfy extensive GCP requirements, including the requirements for informed consent.

All clinical research performed in the United States in support of an NDA must be authorized in advance by the FDA under the IND regulations and procedures described above. However, a sponsor who wishes to conduct a clinical trial outside the United States may, but need not, obtain FDA authorization to conduct the clinical trial under an IND. If a foreign clinical trial is not conducted under an IND, the sponsor may submit data from the clinical trial to the FDA in

support of an NDA so long as the clinical trial is conducted in compliance with GCP and if the FDA is able to validate the data from the study through an onsite inspection, if necessary. GCP includes review and approval by an independent ethics committee, such as an IRB, and obtaining and documenting the freely given informed consent of the subject before study initiation. If the applicant seeks approval of an NDA solely on the basis of foreign data, the FDA will only accept such data if they are applicable to the U.S. population and U.S. medical practice, the studies have been performed by clinical investigators of recognized competence, and the data may be considered valid without the need for an on-site inspection by the FDA, or if the FDA considers such an inspection to be necessary, the FDA is able to validate the data through an on-site inspection or through other appropriate means.

Clinical trials

The clinical investigation of a new drug is typically conducted in three or four phases, which may overlap or be combined, and generally proceed as follows.

Concurrent with clinical trials, companies usually complete additional preclinicalnonclinical studies and must also develop additional information about the chemistry and physical characteristics of the drug and finalize a process for manufacturing the drug in commercial quantities in accordance with GMP requirements. The manufacturing process must be capable of consistently producing quality batches of the drug candidate and, among other things, the manufacturer must develop methods for testing the identity, strength, quality and purity of the final drug product. Additionally, appropriate packaging must be selected and tested and stability studies must be conducted to demonstrate that the drug candidate does not undergo unacceptable deterioration over its shelf life.

The FDA, the IRB or the clinical trial sponsor may suspend or terminate a clinical trial at any time on various grounds, including a finding that the research subjects are being exposed to an unacceptable health risk.

Additionally, some clinical trials are overseen by an independent group of qualified experts organized by the clinical trial sponsor, known as a data safety monitoring board or committee. This group provides authorization for whether or not a trial may move forward at designated check points based on access to certain data from the study. We may also suspend or terminate a clinical trial based on evolving business objectives and/or competitive climate.

New drug applications

The results of preclinical studies and of the clinical trials, together with other detailed information, including extensive manufacturing information and information on the composition of the drug, are submitted to the FDA in the form of an NDA requesting approval to market the drug for one or more specified indications. The FDA reviews an NDA to determine, among other things, whether a drug is safe and effective for its intended use.

Under the Prescription Drug User Fee Act, the FDA has a goal of responding to standard review NDAs of new molecular entities within ten months after the 60 60‑day filing review period, or six months after the 60 60‑day filing review period for priority review NDAs, but this timeframe is often extended by FDA requests for additional information or clarification. The FDA may refer the application to an advisory committee for review, evaluation and recommendation as to whether the application should be approved. The FDA is not bound by the recommendation of an advisory committee, but it generally follows such recommendations.

Before approving an application, the FDA will inspect the facility or the facilities at which the finished drug product, and sometimes the active pharmaceutical ingredient, or API, is manufactured, and will not approve the drug unless cGMP compliance is satisfactory. The FDA may also inspect the sites at which the clinical trials were conducted to assess their compliance, and will not approve the drug unless compliance with cGCP requirements is satisfactory.

After the FDA evaluates the NDA and conducts inspections of manufacturing facilities where the drug product and/or its API will be produced, it may issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the drug with specific prescribing information for specific indications. A Complete Response Letter indicates that the review cycle of the application is complete and the application is not ready for approval. A Complete Response Letter may require additional clinical data and/or an additional pivotal Phase 3 clinical trial(s), and/or other significant, expensive and time-consuming requirements related to clinical trials, preclinical studies or manufacturing. Even if such additional information is submitted, the FDA may ultimately decide that the NDA does not satisfy the criteria for approval. The FDA could also approve the NDA with a Risk Evaluation and Mitigation Strategy, or REMS, plan to mitigate risks, which could include medication

guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling, development of adequate controls and specifications, or a commitment to conduct one or more post-market studies or clinical trials. Such post-market testing may include Phase 4 clinical trials and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization. The FDA has the authority to prevent or limit further marketing of a drug based on the results of these post-marketing programs. Once the FDA approves an NDA, or supplement thereto, the FDA may withdraw the approval if ongoing regulatory requirements are not met or if safety problems are identified after the drug reaches the market.

Drugs may be marketed only for the FDA approved indications and in accordance with the provisions of the approved labeling. Further, if there are any modifications to the drug, including changes in indications, labeling, or manufacturing processes or facilities, the applicant may be required to submit and obtain FDA approval of a new NDA or NDA supplement, which may require the applicant to develop additional data or conduct additional preclinical studies and clinical trials.

The testing and approval processes require substantial time, effort and financial resources, and each may take several years to complete. The FDA may not grant approval on a timely basis, or at all. Even if we believe a clinical trial has demonstrated safety and efficacy of one of our drug candidates for the proposed indication, the results may not be satisfactory to the FDA. Nonclinical and clinical data may be interpreted by the FDA in different ways, which could delay, limit or prevent regulatory approval. We may encounter difficulties or unanticipated costs in our efforts to secure necessary governmental approvals which could delay or preclude us from marketing drugs. The FDA may limit the indications for use or place other conditions on any approvals that could restrict the commercial application of the drugs. After approval, certain changes to the approved drug, such as adding new indications, manufacturing changes, or additional labeling claims are subject to further FDA review and approval. Depending on the nature of the change proposed, an NDA supplement must be filed and approved before the change may be implemented. For many proposed post-approval changes to an NDA, but excluding efficacy supplements to an NDA, the FDA has up to 180 days to review the application. As with new NDAs, the review process is often significantly extended by the FDA requests for additional information or clarification.

Other regulatory requirements

Any drugs manufactured or distributed by us or our collaboration partners pursuant to FDA approvals would be subject to continuing regulation by the FDA, including recordkeeping requirements and reporting of adverse experiences associated with the drug. Drug manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic announced and unannounced inspections by the FDA and certain state agencies for compliance with ongoing regulatory requirements, including cGMP, which impose certain procedural and documentation requirements upon us and our third partythird-party manufacturers. Failure to comply with the statutory and regulatory requirements can subject a manufacturer to possible legal or regulatory action, such as warning letters, suspension of manufacturing, seizure of product, injunctive action or possible civil penalties. We cannot be certain that we or our present or future third partythird-party manufacturers or suppliers will be able to comply with the cGMP regulations and other ongoing FDA regulatory requirements. If we or our present or future third partythird-party manufacturers or suppliers are not able to comply with these requirements, the FDA may, among other things, halt our clinical trials, require us to recall a drug from distribution or withdraw approval of the NDA for that drug.

The FDA closely regulates the post-approval marketing and promotion of drugs, including standards and regulations for direct-to-consumer advertising, off-label promotion, industry-sponsored scientific and educational activities and promotional activities involving the Internet. A company can make only those claims relating to safety and efficacy that are approved by the FDA. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available drugs for uses that are not described in the product’s labeling and that

differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, impose stringent restrictions on manufacturers’ communications regarding off-label use.

Hatch-Waxman Act

Section 505 of the FFDCA describes three types of marketing applications that may be submitted to the FDA to request marketing authorization for a new drug. A Section 505(b)(1) NDA is an application that contains full reports of investigations of safety and efficacy. A 505(b)(2) NDA is an application that contains full reports of investigations of safety and efficacy but where at least some of the information required for approval comes from investigations that were not conducted by or for the applicant and for which the applicant has not obtained a right of reference or use from the person by or for whom the investigations were conducted. This regulatory pathway enables the applicant to rely, in part, on the FDA’s prior findings of safety and efficacy for an existing product, or published literature, in support of its application. Section 505(j) establishes an abbreviated approval process for a generic version of approved drug products through the submission of an Abbreviated New Drug Application, or ANDA. An ANDA provides for marketing of a generic drug product that has the same active ingredients, dosage form, strength, route of administration, labeling, performance characteristics and intended use, among other things, to a previously approved product. ANDAs are termed “abbreviated” because they are generally not required to include nonclinical (animal) and clinical (human) data to establish safety and efficacy. Instead, generic applicants must scientifically demonstrate that their product is bioequivalent to, or performs in the same manner as, the innovator drug through in vitro, in vivo, or other testing. The generic version must deliver the same amount of active ingredients into a subject’s bloodstream in the same amount of time as the innovator drug and can often be substituted by pharmacists under prescriptions written for the reference listed drug. In seeking approval for a drug through an NDA, applicants are required to list with the FDA each patent with claims that cover the applicant’s drug or a method of using the drug. Upon approval of a drug, each of the patents listed in the application for the drug is then published in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, commonly known as the Orange Book. Drugs listed in the Orange Book can, in turn, be cited by potential competitors in support of approval of an ANDA or 505(b)(2) NDA.

Upon submission of an ANDA or a 505(b)(2) NDA, an applicant must certify to the FDA that (1) no patent information on the drug product that is the subject of the application has been submitted to the FDA; (2) such patent has expired; (3) the date on which such patent expires; or (4) such patent is invalid or will not be infringed upon by the manufacture, use or sale of the drug product for which the application is submitted. Generally, the ANDA or

505(b)(2) NDA cannot be approved until all listed patents have expired, except where the ANDA or 505(b)(2) NDA applicant challenges a listed patent through the last type of certification, also known as a paragraph IV certification. If the applicant does not challenge the listed patents or indicates that it is not seeking approval of a patented method of use, the ANDA or 505(b)(2) NDA application will not be approved until all of the listed patents claiming the referenced product have expired.

If the ANDA or 505(b)(2) NDA applicant has provided a Paragraph IV certification to the FDA, the applicant must send notice of the Paragraph IV certification to the NDA and patent holders once the application has been accepted for filing by the FDA. The NDA and patent holders may then initiate a patent infringement lawsuit in response to the notice of the paragraph IV certification. If the paragraph IV certification is challenged by an NDA holder or the patent owner(s) asserts a patent challenge to the paragraph IV certification, the FDA may not approve that application until the earlier of 30 months from the receipt of the notice of the paragraph IV certification, the expiration of the patent, when the infringement case concerning each such patent was favorably decided in the applicant’s favor or settled, or such shorter or longer period as may be ordered by a court. This prohibition is generally referred to as the 30‑month stay. In instances where an ANDA or 505(b)(2) NDA applicant files a paragraph IV certification, the NDA holder or patent owner(s) regularly take action to trigger the 30‑month stay, recognizing that the related patent litigation may take many months or years to resolve. Thus, approval of an ANDA or 505(b)(2) NDA could be delayed for a significant period of time depending on the patent certification the applicant makes and the reference drug sponsor’s decision to initiate patent litigation.

The Hatch-Waxman Act establishes periods of regulatory exclusivity for certain approved drug products, during which the FDA cannot approve (or in some cases accept) an ANDA or 505(b)(2) application that relies on the branded reference drug. For example, the holder of an NDA, including a 505(b)(2) NDA, may obtain five years of exclusivity upon approval of a new drug containing new chemical entities, or NCEs, that have not been previously approved by the FDA. A drug is a new chemical entity if the FDA has not previously approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the therapeutic activity of the drug substance. During the exclusivity period, the FDA may not accept for review an ANDA or a 505(b)(2) NDA submitted by another company that contains the previously approved active moiety. However, an ANDA or 505(b)(2) NDA may be submitted after four years if it contains a certification of patent invalidity or non-infringement.

The Hatch-Waxman Act also provides three years of marketing exclusivity to the holder of an NDA (including a 505(b)(2) NDA) for a particular condition of approval, or change to a marketed product, such as a new formulation for a previously approved product, if one or more new clinical studies (other than bioavailability or bioequivalence studies) was essential to the approval of the application and was conducted/sponsored by the applicant. This three-year exclusivity period protects against FDA approval of ANDAs and 505(b)(2) NDAs for the condition of the new drug’s approval. As a general matter, the three-year exclusivity does not prohibit the FDA from approving ANDAs or 505(b)(2) NDAs for generic versions of the original, unmodified drug product. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA; however, an applicant submitting a full NDA would be required to conduct or obtain a right of reference to all of the preclinical studies and adequate and well-controlled clinical trials necessary to demonstrate safety and efficacy.

Fraud and abuse laws

In the United States, the research, manufacturing, distribution, sale and promotion of drug products and medical devices are potentially subject to regulation by various federal, state and local authorities in addition to the FDA, including the Centers for Medicare & Medicaid Services, or CMS, other divisions of the U.S. Department of Health and Human Services (e.g., the Office of Inspector General), the U.S. Department of Justice, state Attorneys General, and other state and local government agencies. These laws include but are not limited to, the Anti-Kickback Statute, the federal False Claims Act, the federal Physician Payments Sunshine Payment Act, and other state and federal laws and regulations.

The Anti-Kickback Statute makes it illegal for any person, including a prescription drug manufacturer (or a party acting on its behalf) to knowingly and willfully solicit, receive, offer, or pay any remuneration that is intended to induce the referral of business, including the purchase, order, or prescription of a particular drug, for which payment may be made under a federal healthcare program, such as Medicare or Medicaid. Violations of this law are punishable

by up to five years in prison, criminal fines, administrative civil money penalties, and exclusion from participation in federal healthcare programs. In addition, the Affordable Care Act, among other things, amends the intent requirement of the federal Anti-Kickback Statute and federal criminal healthcare fraud statutes. Aa person or entity no longer needsdoes not need to have actual knowledge of the statute or specific intent to violate it.it in order to have committed a violation. Moreover, the Affordable Care Act provides that the government may assert that a claim including items or services resulting from a violation of the federal anti-kickback statuteAnti-Kickback Statute constitutes a false or fraudulent claim for purposes of the False Claims Act.

The federal False Claims Act prohibits anyone from knowingly presenting, or causing to be presented, for payment to federal programs (including Medicare and Medicaid) claims for items or services, including drugs, that are false or fraudulent, claims for items or services not provided as claimed, or claims for medically unnecessary items or services. Although we would not submit claims directly to payors, manufacturers can be held liable under these laws if they are deemed to “cause” the submission of false or fraudulent claims by, for example, providing inaccurate billing or coding information to customers or promoting a product off-label. In addition, our future activities relating to the reporting of wholesaler or estimated retail prices for our products, the reporting of prices used to calculate Medicaid rebate information and other information affecting federal, state, and third-party reimbursement for our products, and the sale and marketing of our products, are subject to scrutiny under this law. For example, pharmaceutical companies have been prosecuted under the federal False Claims Act in connection with their off-label promotion of drugs. Penalties for a False Claims Act violation include three times the actual damages sustained by the government, plus mandatory civil penalties of between $5,500$11,181 and $11,000$22,363 for each separate false claim, the potential for exclusion from participation in federal healthcare programs, and, although the federal False Claims Act is a civil statute, conduct that results in a False Claims Act violation may also implicate various federal criminal statutes. If the government were to allege that we were, or convict us of, violating these false claims laws, we could be subject to a substantial fine and may suffer a decline in our stock price. In addition, private individuals have the ability to bring actions under the federal False Claims Act and certain states have enacted laws modeled after the federal False Claims Act.

In addition to the laws described above, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, collectively known as the Affordable Care Act, also imposed new reporting requirements on drug manufacturers for payments made to physicians and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members. Failure to submit required information may result in civil monetary penalties of up to an aggregate of $150,000$165,786 per year (or up to an aggregate of $1$1.105 million per year for “knowing failures”), for all payments, transfers of value or ownership or investment interests that are not timely, accurately and completely reported in an annual submission. The period

between August 1, 2013 and December 31, 2013 was the first reporting period and manufacturers were required to report aggregate payment data by March 31, 2014, and will be required to report detailed payment data and submit legal attestation to the accuracy of such data during Phase 2 of the program (which begins in May 2014 and extends for at least 30 days). Thereafter, manufacturersManufacturers must submit reports by the 90th day of each subsequent calendar year.

Many states have also adopted laws similar to the federal laws discussed above. Some of these state prohibitions apply to the referral of patients for healthcare services reimbursed by any insurer, not just federal healthcare programs such as Medicare and Medicaid. There has also been a recent trend of increased regulation of payments made to physicians and other healthcare providers. Certain states mandate implementation of compliance programs, impose restrictions on drug manufacturers’ marketing practices and/or require the tracking and reporting of pricing and marketing information as well as gifts, compensation and other remuneration to physicians. Many of these laws contain ambiguities as to what is required to comply with such laws, which may affect our sales, marketing, and other promotional activities by imposing administrative and compliance burdens on us. In addition, given the lack of clarity with respect to these laws and their implementation, our reporting actions could be subject to the penalty provisions of the pertinent state and perhaps federal, authorities.

Because we intend to commercialize products that could be reimbursed under a federal healthcare program and other governmental healthcare programs, we plan to develop a comprehensive compliance program that establishes internal controls to facilitate adherence to the rules and program requirements to which we will or may become subject. Although compliance programs can mitigate the risk of investigation and prosecution for violations of these laws, the risks cannot be entirely eliminated. Due to the breadth of these laws, the absence of guidance in the form of regulations or court decisions, and the potential for additional legal or regulatory change in this area, it is possible that our future sales and marketing practices and/or our future relationships with physicians and other healthcare providers might be challenged under such laws. Any action against us for violation of these laws, even if we successfully defend against it, could cause us to incur significant legal expenses and divert our management’s attention from the operation of our business.

Third-party coverage and reimbursement

Sales of pharmaceutical products depend in significant part on the availability of coverage and adequate reimbursement by third-party payors, such as state and federal governments, including Medicare and Medicaid, and commercial managed care providers. In the United States, no uniform policy of coverage and reimbursement for drug products exists among third-party payors. Accordingly, decisions regarding the extent of coverage and amount of reimbursement to be provided for our product candidates, if approved, will be made on a payor by payor basis. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our product candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be obtained. Third-party payors may limit coverage to specific drug products on an approved list, or formulary, which might not include all of the FDA-approved drugs for a particular indication. A decision by a third-party payor not to cover our product candidates could reduce physician utilization of our products once approved and have a material adverse effect on our future sales, results of operations and financial condition. Moreover, a payor’s decision to provide coverage for a drug product does not imply that an adequate reimbursement rate will be approved. Adequate third-party reimbursement may not be available to enable us to maintain price levels sufficient to realize an appropriate return on our investment in product development.

In addition, in July 2010, CMS released its final rule to implement a bundled prospective payment system for the treatment of ESRD patients as required by the Medicare Improvements for Patients and Providers Act, or MIPPA. The bundled payment includes all renal dialysis services furnished for outpatient maintenance dialysis, including ESRD-related drugs and biologicals. The final rule delayed the inclusion of oral medications without intravenous equivalents in the bundled payment until January 1, 2014 and in April 2014, President Obama signed the Protecting Accessdue to Medicare Act of 2014, which further extends this implementation date tosubsequent legislative amendments, CMS provided that such inclusion will remain delayed until January 1, 2024. As a result of the recent legislation,2025. Unless additional Congressional action is taken, beginning in 2024,2025 ESRD-related drugs will be included in the bundle

and separate Medicare reimbursement will no longer be available for such drugs, as it is today under Medicare Part D. While it is too early to project the full impact that bundling may have on drugs for the phosphate binder industry,treatment of hyperphosphatemia, the impact could potentially cause dramatic price reductions for tenapanor, if approved.

Healthcare reform

In March 2010, Congress passed and President Obama signed into law, the Patient Protection and Affordable Care Act, a healthcare reform measure, often called, the Affordable Care Act. The Affordable Care Act substantially changes the way healthcare will beis financed by both governmental and private insurers, and significantly impacts the pharmaceutical industry.

The Affordable Care Act contains a number of provisions, including those governing enrollment in federal healthcare programs, reimbursement changes and fraud and abuse measures, which will impacthave impacted existing government healthcare programs and will resulthave resulted in the development of new programs, including Medicare payment for performance initiatives and improvements to the physician quality reporting system and feedback program.

Additionally, the Affordable Care Act:

Since its enactment, there have been judicial and Congressional challenges to certain aspects of the federal poverty level, thereby potentially increasing a manufacturer’s Medicaid rebate liability;

CORPORATE INFORMATION

We were incorporated in Delaware on October 17, 2007, under the name Nteryx and changed our name to Ardelyx, Inc. in June 2008. We operate in only one business segment, which is the research, development and commercialization of biopharmaceutical products. See Note 1 to our financial statements included in this Annual Report on Form 10-K.10‑K. Our principal offices are located at 34175 Ardenwood Blvd., Suite 200, Fremont, CA 94555, and our telephone number is (510) 745-1700.745‑1700. Our website address is www.ardelyx.com.

We file electronically with the Securities and Exchange Commission, or SEC, our annual reports on Form 10-K,10‑K, quarterly reports on Form 10-Q10‑Q and current reports on Form 8-K8‑K pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended. We make available on our website at www.ardelyx.com, free of charge, copies of these reports, as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. The public may read or copy any materials we file with the SEC at the SEC’s Public Reference Room at 100 F Street NE, Washington, D.C. 20549. The public may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-SEC-0330.1‑800‑SEC‑0330. The SEC maintains a website that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC. The address of that website iswww.sec.gov. www.sec.gov.

ITEM 1A. RISK FACTORS

Our business involves significant risks, some of which are described below. You should carefully consider these risks, as well as other information in this Annual Report on Form 10-K,10‑K, including our financial statements and the related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The occurrence of any of the events or developments described below could harm our business, financial condition, results of operations, cash flows, the trading price of our common stock and our growth prospects. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also impair our business operations.

Risks Related to Our Limited Operating History, Financial Condition and Capital Requirements

We have a limited operating history, have incurred significant losses since our inception and we will incur losses in the future, which makes it difficult to assess our future viability.

We are a clinical-stage biopharmaceutical company with a limited operating history. Biopharmaceutical product development is a highly speculative undertaking and involves a substantial degree of risk. To date, we have focused substantially all of our efforts on our research and development activities, including developing our clinical product candidates, tenapanor and RDX022, and developing our proprietary drug discovery and design platform. To date, we have not commercialized any products or generated any revenue from the sale of products.

We are not profitable and have incurred losses in each year since our inception in October 2007, and we do not know whether or when we will become profitable. We have only a limited operating history upon which to evaluate our business and prospects. We continue to incur significant research, development and other expenses related to our ongoing operations. As of December 31, 2015,2017, we had an accumulated deficit of $101.5$278.2 million.

We expect that our operating losses will substantially increase for the foreseeable future as we continueprepare for the potential commercialization of, and incur manufacturing and development ofcosts for, tenapanor, and RDX022. Inincluding costs associated with completing the fourth quarter of 2015, we initiated twoongoing Phase 3 clinical trials to evaluate tenapanor for the treatmentdevelopment of IBS-C, and in December 2015, we initiated a Phase 2b clinical trial evaluating tenapanor for the treatment of hyperphosphatemia in end stage renal disease patients. In addition, we expect our operating lossesESRD patients on dialysis, preparing the new drug application, or NDA, for submission to substantially increase as we incur manufacturing coststhe U.S. Food and Drug Administration, or FDA, to request marketing authorization for tenapanor for the treatment of patients with IBS-C, and RDX022, advance RDX022 into a Phase 3 clinical program which we expect to initiate in the second half of 2016, and as we continuecontinuing our discovery research, development, manufacturing and commercializationresearch activities.

Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital. Further, the net losses we incur may fluctuate significantly from quarter to quarter and year to year, such that a period-to-period comparison of our results of operations may not be a good indication of our future performance.

We have substantial net operating loss and tax credit carryforwards for Federal and California income tax purposes. Such net operating losses and tax credits carryforwards may be reduced as a result of certain intercompany restructuring transactions. In addition, the future utilization of such net operating loss and tax credit carryforwards and credits will be subject to limitations, pursuant to Internal Revenue Code Sections 382 and 383, as a result of ownership changes that have occurred previously and additional limitations may be applicable as a result of ownership changes that could occur in the future.

We have never generated any revenue from product sales and may never be profitable.

We have no products approved for sale and have never generated any revenue from product sales. Our ability to generate revenue from product sales and achieve profitability depends on our ability to successfully complete the development of and obtain the regulatory and marketing approvals necessary to commercialize tenapanor for one or more ofindications, either on our product candidates.own, or with one or more collaboration partners. We do not anticipate generating revenue from product sales for the foreseeable future. Our ability to generate future revenue from product sales or pursuant to milestone payments depends heavily on many factors, including but not limited to:

In cases where we are successful in obtaining regulatory approvals to market tenapanor for one or more of our product candidates,indications, our revenue will be dependent, in part, upon the size of the markets in the territories for which regulatory approval is granted, the accepted price for the product, the ability to get reimbursement at any price

and whether we are commercializing the product or the product is being commercialized by a collaboration partner, and in such case, whether we have royalty and/or co-promotion rights for that territory. If the number of patients suitable for our product candidatestenapanor is not as significant as we estimate, the indicationindications approved by regulatory authorities isare narrower than we expect, or the reasonably accepted population for treatment is narrowed by competition, physician choice or treatment guidelines, we may not generate significant revenue from the sale of such products,tenapanor, even if approved. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our failure to generate revenue from product

sales would likely depress our market value and could impair our ability to raise capital, expand our business, discover or develop other product candidates or continue our operations. A decline in the value of our common stock could cause our stockholders to lose all or part of their investment.

We will require substantial additional financing to achieve our goals, and a failurethe inability to obtainaccess this necessary capital when needed on acceptable terms, or at all, could force us to delay, limit, reduce or terminate our planned clinical programspre-commercialization efforts for tenapanor and RDX022, or our other product development and platform development activities.

Since our inception, most of our resources have been dedicated to our research and development activities, including developing our clinical product candidates,candidate tenapanor and RDX022, and developing our proprietary drug discovery and design platform. We believe that we will continue to expend substantial resources for the foreseeable future, including costs associated with conductingcompleting the Phase 3 clinical programsprogram for tenapanor and RDX022,for the treatment of hyperphosphatemia in ESRD patients on dialysis, research and development, conducting preclinical studies and clinical trials for our other programs, obtaining regulatory approvals, developing and maintaining scalable manufacturing processes for our product candidates and sales and marketing. Because the outcome of any clinical trial and/or regulatory approval process is highly uncertain, we cannot reasonably estimate the actual amounts necessary to successfully complete the development, regulatory approval process and commercialization or co-promotion of any of our product candidates. Our future funding requirements will depend on many factors, including, but not limited to:

Additional funds may not be available when we need them on terms that are acceptable to us, or at all. If adequate funds are not available to us on a timely basis, we may be required to delay, the clinical development of tenapanor and/or RDX022, delay, limit, reduce or terminate our research activities, preclinical and clinical trials for our other product candidates and our establishment and maintenance of sales and marketing capabilities or other activities that may be necessary to commercialize our product candidates,tenapanor, either alone or with collaboration partners. Additionally, our inability to access capital on a collaboration partner.timely basis and on terms that are acceptable to us may force us to restructure certain aspects of our business or identify and complete one or more strategic collaborations or other transactions in order to fund the development or commercialization of tenapanor or certain of our product candidates through the use of alternative structures.

Risks Related to Our Business

We are substantially dependent on the success of our lead product candidate, tenapanor, which may not be successful in further nonclinical studies or clinical trials, receive regulatory approval or be successfully commercialized.

To date, we have invested a significant amount of our efforts and financial resources in the research and development of tenapanor, which is currently our lead product candidate and one of only two product candidates in clinical trials.candidate. The clinical and commercial success of tenapanor will depend on a number of factors, including the following:

As tenapanor is a first-in-class drug, there is a higher likelihood that approval may not be attained as compared to a class of drugs with approved products. We cannotWhile tenapanor met the primary endpoint in two Phase 3 clinical studies evaluating tenapanor for the treatment of patients with IBS-C, there can be certainno assurance that our NDA that we plan to submit for this indication, once submitted, will be accepted by FDA or that we will receive marketing authorization from FDA. Although tenapanor met the primary endpoint in the first Phase 3 clinical trial for the treatment of hyperphosphatemia in ESRD patients on dialysis, there can be no assurances that the second Phase 3 trial of tenapanor in this indication will achieve the primary endpoint, or that tenapanor will be successful in non-clinical safety studies or clinical trials, or that it will receive regulatory approval.approval for this indication. Further, it may not be possible or practicable to demonstrate, or if approved, to market tenapanor on the basis of certain of the benefits we believe tenapanor possesses. For example, the reduction of serum phosphorus is currently an approvable endpoint in CKDESRD patients on dialysis, but not for the broader CKD patient population in the United States. If the number of patients in the market for tenapanor or the price that the market can bear is not as significant as we estimate, we may not generate sufficient revenue from sales of tenapanor, if approved. Accordingly, there can be no assurance that tenapanor will ever be successfully commercialized or that we will ever generate income from sales of tenapanor. If we are not successful in completing the development of, obtaining approval for, and commercializing tenapanor, or are significantly delayed in doing so, our business will be materially harmed.

Clinical drug development involves a lengthy and expensive process with an uncertain outcome, and we may encounter substantial delays in our Phase 3 clinical studies.study of tenapanor for the treatment of hyperphosphatemia. Furthermore, results of earlier studies and trials may not be predictive of future trial results.

Before obtaining marketing approval from regulatory authorities for the sale of our product candidates, we must conduct extensive clinical studies to demonstrate the safety and efficacy of the product candidates in humans. Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain. Failure can occur at any time during the clinical trial process. The results of preclinical and clinical studies of our product candidates may not be predictive of the results of later-stage clinical trials. For example, the positive results generated to date in preclinical and clinical studies for tenapanor do not ensure that the ongoing Phase 3 clinical trials for tenapanor, or future clinical trials, will demonstrate similar results. An unexpected adverse event profile, or the results of drug-drug interaction studies, may present challenges for the future development and commercialization of a product candidate for a particular condition despite receipt of positive efficacy data in a clinical study. For example,Although tenapanor met the primary endpoint in athe first Phase 2b study evaluating tenapanor3 clinical trial for the treatment of hyperphosphatemia in end stage renal disease, or ESRD patients we observedon dialysis, there can be no assurances that the study met its primary endpoint by demonstrating a statistically significant dose-related decreasesecond Phase 3 trial results of tenapanor in serum phosphate levels for tenapanor-treated patients compared to patients receiving placebo, while also observing that the rate of diarrhea and the discontinuation rate due to diarrhea at the highest doses were higher than expected based upon previous clinical trials. Product candidates in later stages of clinical trials may fail toindication will show the desired safety and efficacy despite having progressed through preclinical studies and initial clinical trials.efficacy. A number of companies in the pharmaceutical, biopharmaceutical and biotechnology industries have suffered significant setbacks in advanced clinical trials for similar indications that we are pursuing due to lack of efficacy or adverse safety profiles, notwithstanding promising results in earlier studies, and we cannot be certain that we will not face similar

setbacks. Even if our clinical trials arePhase 3 program for tenapanor for the treatment of hyperphosphatemia is completed, and despite the completion of our Phase 3 program for tenapanor for IBS-C, the results for one or both indications may not be sufficient to obtain regulatory approval for our product candidates,tenapanor, or if such regulatory approval is obtained, the content of the

label approved by regulatory authorities may materially and adversely impact our ability to commercialize the product.product for the approved indication.

We do not know whether futureour second Phase 3 clinical trialstrial for tenapanor for the treatment of hyperphosphatemia will begin on time, or whether our ongoing or future clinical trials will need to be redesigned, enroll an adequate number of patients on time or be completed on schedule, if at all. Clinical trials can be delayed or terminated for a variety of reasons, including delay or failure to:

Patient enrollment is a significant factor in the timing of clinical trials and is affected by many factors, including the size and nature of the patient population, the proximity of patients to clinical sites, the eligibility criteria for the trial, the design of the clinical trial, competing clinical trials and clinicians’ and patients’ perceptions as to the potential advantages of the drug being studied in relation to other available therapies, including any new drugs or treatments that may be approved for the indications we are investigating.

We could also encounter delays if aour Phase 3 clinical trial is suspended or terminated by us, by the IRBs of the institutions in which such trials arethe trial is being conducted, by an independent data safety monitoring board for such trial or by the FDA or other regulatory authorities. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a drug, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial.

Further, conducting clinical trials in foreign countries presents additional risks that may delay completion of clinical trials. These risks include the failure of physicians or enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes and political and economic risks relevant to such foreign countries. In addition, the FDA may determine that the clinical trial results obtained in foreign subjects do not represent the safety and efficacy of a product candidate when administered in U.S. patients and are thus not supportive of New Drug Application, or NDA, approval in the United States. Ifif there are delays in the completion of, or termination of, anythe Phase 3 clinical trial for tenapanor for the treatment of our product candidates,hyperphosphatemia, the commercial prospects of our product candidatestenapanor for such indication may be harmed, and our ability to generate revenue from product sales from any of these product candidatestenapanor for such indication will be delayed. In addition, any delays in completing the clinical trialstrial will increase costs,

slow down our product candidate development and approval process for tenapanor for hyperphosphatemia and jeopardize the ability to commence product sales and generate revenue from product sales.sales for this indication. Any of these occurrences may significantly harm our business, financial condition and prospects. In addition, many of the factors that may cause, or lead to, a delay in the commencement or completion of the Phase 3 clinical trialstrial may also ultimately lead to the denial of regulatory approval.

Even if we successfully obtain regulatory approval for tenapanor, it may never achieve market acceptance, sufficient third-party coverage or reimbursement, or commercial success, which will depend, in part, upon the degree of our product candidates.acceptance among physicians, patients, patient advocacy groups, health care payors and the medical community.

We intend to devote significant resources to the development of RDX022 whichEven if tenapanor obtains FDA or other regulatory approvals, and is ultimately commercialized for one or more indications, it may not be successfulachieve market acceptance among physicians, patients, third-party payors, patient advocacy groups, and the medical community. Market acceptance of tenapanor, in nonclinical studiesthe event that marketing approval is obtained, depends on a number of factors, including:

Any failure by us to obtain a collaboration partner for the commercialization of tenapanor in the United States for IBS-C and any failure of tenapanor to achieve market acceptance, sufficient third-party coverage or clinical trials,reimbursement, or commercial success, should it receive regulatory approval, or be successfully commercialized.would adversely affect our results of operations.

With the advancement of RDX022 into human studies in June 2015, and the expected initiation of a Phase 3 clinical program for RDX022 in the second half of 2016, we expect to invest a significant amount of our efforts and financial resources in the development of RDX022. We are pursuing a 505(b)(2) regulatory path for approval of RDX022, which, among other things allows us to rely on the FDA’s previous findings of safety and efficacy and may eliminate the need to conduct certain nonclinical and clinical studies of our product candidate. This regulatory pathway, which can accelerate development, may not be available to us if a pharmaceutically equivalent product to RDX022 were approved prior to the approval of our 505(b)(2) application.currently have no sales organization. If we are unable to rely uponestablish sales capabilities on our own or through third parties, we may not be able to commercialize tenapanor or any of our other product candidates.

We currently do not have a 505(b)(2)sales organization. In order to commercialize or co-promote tenapanor or any of our other product candidates, we must enter collaborative relationships with one or more third parties, or build internal marketing, sales, distribution, managerial and other non-technical capabilities. There can be no assurances that we will be successful in establishing collaborative relationships in a timely manner or on terms that are acceptable to us. If tenapanor receives regulatory pathwayapproval and we have not entered collaborative relationships for the approvalcommercialization of RDX022,tenapanor in the United States, we would have to establish appropriate sales organizations with technical expertise supporting distribution capabilities to commercialize the product candidate, which will be expensive and time consuming, or delay the commercial launch of tenapanor for such indication. As a company, we have no prior experience in the marketing, sale and distribution of pharmaceutical products and there are significant risks involved in

building and managing a sales organization, including our ability to secure the capital necessary to fund such efforts on acceptable terms, hire, retain, and incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, comply with regulatory requirements applicable to the marketing and sale of drug products and effectively manage a geographically dispersed sales and marketing team.

If we are unable to enter collaborative relationships a timely manner, or on acceptable terms, and/or we fail or are delayed in the development of RDX022 may be substantially delayed orour internal sales, marketing and distribution capabilities, we may choose to delay the commercialization of our products and/or the commercialization of our products could be required to abandon such development.

The clinicaladversely impacted, and commercial success of RDX022 will depend on a number of factors, including the following:

As a result of pursuing a 505(b)(2) path for RDX022, we will not evaluate the efficacy of RDX022 in patients with hyperkalemia prior to the initiation of the Phase 3 clinical program. We cannot be certain that clinical trials evaluating RDX022 will establish a safety and efficacy profile sufficient to enable RDX022 to gain approval by the FDA, or if approved, compete effectively with alternative and competing treatments. Further, it

may not be possible or practicable to demonstrate, or if approved, to market on the basis of, certain of the benefits we believe RDX022 may possess. Accordingly, there can be no assurance that RDX022 will ever be successfully commercialized or that we will ever generate revenue from sales of RDX022. If we are not successful in completing the development of, obtaining approval for, and commercializing RDX022, or are significantly delayed in doing so, our business will be materially harmed.

We may not be successful in our efforts to develop our product candidates that are at an early stage of development, including RDX009, or expand our pipeline of product candidates.candidates, as a result of numerous factors, which may include the inability to access capital necessary to fund such efforts on acceptable terms.

A key element of our strategy is to expandhas been focused on the expansion of our pipeline of product candidates utilizing our proprietary drug discovery and design platform and to advance such product candidates through clinical development. In December 2015,2016, we selectedfiled an IND to commence clinical development of RDX8940 in the United States. In August 2017, we completed a comprehensive strategic review of our operations, assessing several core areas, to optimally position the company to advance towards delivering on multiple significant opportunities with our late-stage portfolio and execute on our strategic objectives. This review resulted in the prioritization of resources to focus on the upcoming milestones for the late-stage programs, a delay in the development candidate for our RDX009 program. This product candidate,of a number of earlier-stage programs, including RDX8940, and a reduction in workforce. RDX8940 and those product candidates that are in the discovery and lead identification stages of preclinical development will require substantial preclinical and clinical development, testing and regulatory approval prior to commercialization. In particular, tenapanorcommercialization, and RDX022 arewe may not be able to access the capital necessary to fund such efforts on acceptable terms. Our inability to access capital in a timely manner or on acceptable terms to fund our onlyearly stage product candidates in clinical trials and allmay force us to consider certain restructuring activities to enable the funding of our other product candidates are inthose early assets through the preclinical stage with significant research and development required before we could begin clinical studies. Ofuse of alternative structures. In addition, of the large number of drugs in development, only a small percentage of such drugs successfully complete the FDA regulatory approval process and are commercialized. Accordingly, even if we are able to continue to fund our research and early stage development programs, there can be no assurance that any product candidates will reach the clinic or be successfully developed or commercialized.

Research programs to identify product candidates require substantial technical, financial and human resources, whether or not any product candidates are ultimately identified. Although our research and development efforts to date have resulted in several development programs, we may not be able to develop product candidates that are safe, effective and well-tolerated. Our research programs may initially show promise in identifying potential product candidates, and we may select candidates for development, yet we may fail to yieldadvance product candidates forto clinical development or commercialization for many reasons, including the following:

Even if we are successful in continuing to expand our pipeline, through our own research and development efforts, or by pursuing in-licensing or acquisition of product candidates, the potential product candidates that we identify or for which we identify or acquire rights may not be suitable for clinical development, including as a result of being shown to have harmful side effects or other characteristics that indicate that they are unlikely to receive marketing approval and achieve market acceptance. If we do not successfully develop and commercialize a product pipeline, we may not be able to generate revenue from product sales in future periods or ever achieve profitability.

Our proprietary drug discovery and design platform, and, in particular, APECCS, is a new approach to the discovery, design and development of new product candidates and may not result in any products of commercial value.

We have developed a proprietary drug discovery and design platform to enable the identification, screening, testing, design and development of new product candidates, and have developed APECCS as a component of this of this platform. We utilize APECCS in the design of our small molecules and to identify new and potentially novel targets in the GI tract. However, there can be no assurance that APECCS will be able to identify new targets in the GI tract or that any of these potential targets or other aspects of our proprietary drug discovery and design platform will yield product candidates that could enter clinical development and, ultimately, be commercially valuable.

Although we expect to continue to enhance the capabilities of our APECCS system by advancing the cell culture and screening process and/or acquiring new technologies to broaden the scope of APECCS, we may not be successful in any of our enhancement and development efforts. In addition, we may not be able to enter into agreements on suitable terms to utilize technologies required to exploit certain capabilities of APECCS, and in such case, we may be forced to limit our use or further development of APECCS, or to modify APECCS for continued use. It may not be possible to modify APECCS in manner that avoids the utilization of certain technologies, without materially and adversely affecting the performance of APECCS or without incurring substantial cost and delay in advancement of the system. In addition, we may not be successful in developing the conditions necessary to grow multiple segments of intestine or from multiple species, or otherwise develop assays or cell cultures necessary to expand these capabilities. If our enhancement or development efforts are unsuccessful, or if we are forced to limit our use or further development of APECCS due to the inability to enter into agreements on suitable terms to permit the utilization of technologies required to exploit APECCS, we may not be able to advance our drug discovery capabilities as quickly as we expect or identify as many potential drugable targets as we desire.

We rely on third parties to conduct some of our preclinical and nonclinical studies and all of our clinical trials. If these third parties do not successfully carry out their contractual duties or meet expected deadlines, we may be unable to obtain regulatory approval for or commercialize our product candidates.

We do not have the ability to independently conduct clinical trials and, in some cases, preclinical or nonclinical studies. We rely on medical institutions, clinical investigators, contract laboratories, and other third parties, such as CROs, to conduct clinical trials on our product candidates. The third parties with whom we contract for execution of the clinical trials play a significant role in the conduct of these trials and the subsequent collection and analysis of data. However, these third parties are not our employees, and except for contractual duties and obligations, we control only certain aspects of their activities and have limited ability to control the amount or timing of resources that they devote to our programs. Although we rely, and will continue to rely, on these third parties to conduct some of our preclinical and nonclinical studies and all of our clinical trials, we remain responsible for ensuring that each of our studies and clinical trials is conducted in accordance with the applicable protocol, legal, regulatory and scientific standards and our reliance on third parties does not relieve us of our regulatory responsibilities. We, and these third parties are required to comply with current good laboratory practices, or GLPs for preclinical and nonclinical studies, and good clinical practices, or GCPs, for clinical studies. GLPs and GCPs are regulations and guidelines enforced by the FDA, the Competent Authorities of the Member States of the European Economic Area, or EEA, and comparable foreign regulatory authorities for all of our products in preclinicalnonclinical and clinical development, respectively. Regulatory authorities enforce GCPs through periodic inspections of trial sponsors, principal investigators and trial sites. If we or any of our third partythird-party contractors fail to comply with applicable regulatory requirements, including GCPs, the clinical data generated in our clinical trials may be deemed unreliable and the FDA, the European Medicines Agency, or EMA, or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. There can be no assurance that upon inspection by a given regulatory authority, such regulatory authority will determine that any of our clinical trials comply with GCP regulations. In addition, our clinical trials must be conducted with product produced under current good manufacturing practices or cGMP regulations. Our failure to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process.

Any failure by our product candidates that obtain regulatory approval to achieve market acceptance or commercial success would adversely affect our results of operations.

Our product candidates may cause undesirable side effects or have other properties that could delay our clinical trials, or delay or prevent regulatory approval, limit the commercial profile of an approved label, or result in significant negative consequences following regulatory approval, if any. If tenapanor or any of our other product candidates receives marketing approval and we or others later identify undesirable side effects caused by the product candidate, the ability to market the product candidates could be compromised.

Undesirable side effects caused by our product candidates could cause us or regulatory authorities to interrupt, delay or halt clinical trials, result in the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities or limit the commercial profile of an approved label. To date, patients treated with tenapanor have experienced drug-related side effects including diarrhea, nausea, vomiting, flatulence, abdominal discomfort, abdominal pain, abdominal distention and changes in electrolytes, and in the a Phase 2b clinical trial evaluating tenapanor for the treatment of hyperphosphatemia in ESRD patients, we observed that the rate of diarrhea and the discontinuation rate due to diarrhea at the highest doses was higher than expected based upon the results of previous clinical trials.electrolytes. In the event that trials conducted by us with tenapanor or trials we conduct with our other product candidates, reveal an unacceptable severity and prevalence of these or other side effects, such trials could be suspended or terminated and the FDA or comparable foreign regulatory authorities could order us to cease further development of or deny approval of tenapanor, or any such other product candidate, for any or all targeted indications. Additionally, despite a positive efficacy profile, the prevalence and/or severity of these or other side effects could cause us to cease further development of a product candidate for a

particular indication, or entirely. The drug-related side effects could affect patient recruitment or the ability of enrolled patients to complete the trial or result in potential product liability claims. Any of these occurrences may harm our business, financial condition and prospects significantly.

In addition, in the event that any of our product candidates receives regulatory approval and we or others later identify undesirable side effects caused by one of our products, a number of potentially significant negative consequences could occur, including:

Any of the foregoing events could prevent us,  or a collaboration partner, from achieving or maintaining market acceptance of a particular product candidate, if approved, and could result in the loss of significant revenue to us, which would materially and adversely affect our results of operations and business.

We face substantial competition and our competitors may discover, develop or commercialize products faster or more successfully than us.

The biotechnology and pharmaceutical industries are highly competitive, and we face significant competition from companies in the biotechnology, pharmaceutical and other related markets that are researching and marketing products designed to address diseases that we are currently developing products to treat. If approved for marketing by the FDA or other regulatory agencies, tenapanor, and RDX022, as well as our other product candidates, would compete against existing treatments.

For example, tenapanor will, if approved, compete directly with phosphate binders for the treatment of hyperphosphatemia in ESRD patients on dialysis. The various types of phosphate binders commercialized in the United States include the following:

The hydrochloride form of sevelamer, hydrochloride (Renagel)Renagel, was launched in the United States by Genzyme Corporation in 1998 prior to its acquisition by Sanofi, and the carbonate form, Renvela, was launched in 2008. Sanofi booked €802 million ($0.98 billion) in worldwide sales of sevelamer during 2017. Generic sevelamer carbonate (Renvela), which were launched by Genzyme. Synthon announced the successful completion of a Phase 3 multicenter, randomized, double-blind, multiple-dose, crossover trialhas been approved in certain jurisdictions in Europe to compare safetysince 2015 and demonstrate equivalence of serum phosphate control of Synthon sevelamer carbonate tablets to Renvela tablets in chronic kidney disease patients on hemodialysis in April 2014. Currently, several pharmaceutical companies are distributing Synthon manufactured sevelamer carbonate tablets in multiple European countries including, but not limited to, the United Kingdom, Spain, Sweden and Denmark.U.S. market since June 2017. In addition to the currently marketed phosphate binders, Keryx has received FDA approval for ferric citrate (Auryxia), an iron-based binder, that is also approved in Japan and we are aware of at least two other binders in development, including fermagate (Alpharen), an iron-based binder in Phase 23 being developed by Opko Health. Additionally, RDX022, if approved, will compete directly with KayexalateHealth, Inc., and its generic equivalents, known as sodium polystyrene sulfonate, on the marketPT20, an iron-based binder in the United States. In addition, Relypsa just recently commercially launched patiromer (Veltassa) for the treatment of hyperkalemia, and a new drug application, or NDA, was submitted in June 2015, for a sodium zirconium cyclosilicate-based oral potassium binderPhase 3 being developed for the treatment of hyperkalemia by AstraZeneca after its acquisition of ZS Pharma in December 2015.Shield Therapeutics.

Numerous treatments exist for constipation and the constipation component of IBS-C, many of which are over-the-counter. These include psyllium husk (such as Metamucil), methylcellulose (such as Citrucel), calcium polycarbophil (such as FiberCon), lactulose (such as Cephulac), polyethylene glycol (such as MiraLax), sennosides (such as Exlax), bisacodyl (such as Ducolax), docusate sodium (such as Colace), magnesium hydroxide (such as Milk of Magnesia), saline enemas (such as Fleet) and sorbitol. These agents are generally inexpensive and work well to temporarily relieve temporary constipation.

We are also aware of twothree prescription drugs currently on the U.S. market that are approved to treat IBS-C,products marketed for IBS-C: (i) Linzess (linaclotide), which was developedmarketed by Ironwood Pharmaceuticals and is approved for IBS-C and chronic constipation in both the United States and in Europe, andAllergan, (ii) Amitiza (lubiprostone), which was first approved in the United States in 2006 and is currently marketed by Takeda and Sucampo, a wholly-owned subsidiary of Mallinckrodt, and Takeda for treatment of chronic idiopathic constipation, or CIC, IBS-C and opioid induced constipation, or OIC. Additionally,(iii) Trulance (plecanatide), marketed by Synergy filed an NDA for Plecanatide for the treatment of CIC in January 2016, and is currently conducting two Phase 3 clinical trials of Plecanatide for the treatment of IBS-C.Pharmaceuticals.

It is possible that our competitors will develop and market drugs or other treatments that are less expensive and more effective than our product candidates, or that will render our product candidates obsolete. It is also possible that our competitors will commercialize competing drugs or treatments before we, or our collaboration partners, can launch any products developed from our product candidates. We also anticipate that we will face increased competition in the future as new companies enter into our target markets.

Many of our competitors have materially greater name recognition and financial, manufacturing, marketing, research and drug development resources than we do. Additional mergers and acquisitions in the biotechnology and pharmaceutical industries may result in even more resources being concentrated in our competitors. Large pharmaceutical companies in particular have extensive expertise in preclinical and clinical testing and in obtaining regulatory approvals for drugs. In addition, academic institutions, government agencies, and other public and private organizations conducting research may seek patent protection with respect to potentially competitive products or technologies. These organizations may also establish exclusive collaboration partnerships or licensing relationships with our competitors.

We may experience difficulties in managing our current activities and growth given our level of managerial, operational, financial and other resources.

On August 7, 2017, our Board of Directors approved a restructuring plan, pursuant to which we reduced our workforce by 29%, resulting in 75 remaining employees. We will need to manage our operations and clinical trials, and continue our development and pre-commercial activities for our product candidates with this reduced workforce. Our management and personnel, and systems currently have no sales organization. in place may not be adequate to support our current activities or future growth. Our need to effectively execute our business strategy requires that we:

If we are unable to establish sales capabilities onmaintain or expand our own or through third parties, we may not be able to commercialize tenapanor and RDX022, or any of our other product candidates.

We currently do not have a sales organization. In order to promote tenapanor and RDX022, either alone, or with a collaboration partner, and in order to commercialize or co-promote any of our other product candidates, we must build our marketing, sales, distribution, managerial, operational, financial and other non-technical capabilities or make arrangements with third partiesresources to perform these services,the extent required to manage our development and we may not be successful in doing so. In order to commercialize tenapanor or RDX022 outside of the United States, we expect to enter into collaborative relationships with one or more third parties. Additionally, in order to commercialize tenapanor for IBS-C, we expect to enter into a collaborative relationship with one or more third parties in the United States to address the primary care market. There can be no assurances that wepre-commercialization activities, our business will be successful in establishing such relationships in a timely manner or on terms that are acceptable to us. If one or more of our product candidates receives regulatory approval, we expect to establish a specialty sales organization with technical expertise and supporting distribution capabilities to commercialize our product candidates, which will be expensive and time consuming. As a company, we have no prior experience in the marketing, sale and distribution of pharmaceutical products and there are significant risks involved in building and managing a sales organization, including our ability to hire, retain, and incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, comply with regulatory requirements applicable to the marketing and sale of drug products and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities wouldmaterially adversely impact the commercialization of these products.affected.

We may choose to collaborate with third parties that have direct sales forces and established distribution systems, either to augment our own sales force and distribution systems or in lieu of our own sales force and distribution systems. If we are unable to enter into such arrangements on acceptable terms or at all, we may not be able to successfully commercialize our product candidates.

We rely completely on third parties to manufacture our preclinicalnonclinical and clinical drug supplies, and we intend to rely on third parties to produce commercial supplies of any approved product candidate.tenapanor, if approved. Our business would be harmed if those third parties fail to obtain approval of the FDA, Competent Authorities of the Member States of the EEA or comparable regulatory authorities, fail to provide us with sufficient quantities of drug product, or fail to do so at acceptable quality levels or prices.

We do not currently have, nor do we plan to acquire, the infrastructure or capability internally to manufacture tenapanor or any of other our preclinical and clinicalproduct candidates on a commercial scale, or to manufacture our drug supplies for use in the conduct of our preclinicalnonclinical and clinical studies, and we lack the resources and the capability to manufacture any of our product candidates on a clinical or commercial scale.studies. The facilities used by our contract manufacturers to manufacture any drug products must be approved by the FDA pursuant to inspections that will be conducted after an NDA is submitted to the FDA. We do not control the manufacturing process of our product candidates, and we are completely dependent on our contract manufacturing partners for compliance with the regulatory requirements, known as cGMPs, for manufacture of both active drug substances and finished drug products.

If our contract manufacturers cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA or others, they will not be able to secure and/or maintain regulatory approval for their manufacturing facilities. In addition, we have no control over the ability of our contract manufacturers to maintain adequate quality control, quality assurance and qualified personnel. If the FDA or a comparable foreign regulatory authority does not approve these facilities for the manufacture of our product candidates or if it withdraws any

such approval in the future, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain regulatory approval for or market our product candidates, if approved.

We rely on our manufacturers to purchase from third-party suppliers the materials necessary to produce our product candidates for our clinical studies. There are a limited number of suppliers for raw materials that we use to manufacture our drugs, and there may be a need to identify alternate suppliers to prevent a possible disruption of the manufacture of the materials necessary to produce our product candidates for our clinical studies, and, if approved, ultimately for commercial sale. We do not have any control over the process or timing of the acquisition of these raw materials by our manufacturers. Although we generally do not begin a clinical study unless we believe we have on hand, or will be able to manufacture, a sufficient supply of a product candidate to complete such study, any significant delay or discontinuity in the supply of a product candidate, or the raw material components thereof, for an ongoing clinical study due to the need to replace a third-party manufacturer could considerably delay completion of our clinical studies, product testing, and potential regulatory approval of our product candidates, which could harm our business and results of operations.

Third-party payor coverage and reimbursement status of newly-approved products is uncertain. Failure to obtain or maintain adequate coverage and reimbursement for our products, if approved, could limit our ability to market those products and decrease our ability to generate revenue.

The pricing, coverage and reimbursement of our product candidates, if approved, must be adequate to support a commercial infrastructure. The availability and adequacy of coverage and reimbursement by governmental and private payors are essential for most patients to be able to afford treatments such as ours, assuming approval. Sales of our product candidates will depend substantially, both domestically and abroad, on the extent to which the costs of our product candidates will be paid for by health maintenance, managed care, pharmacy benefit, and similar healthcare management organizations, or reimbursed by government authorities, private health insurers, and other third-party payors. If coverage and reimbursement are not available, or are available only to limited levels, we may not be able to successfully commercialize our product candidates. Even if coverage is provided, the approved reimbursement amount may not be high enough to allow us to establish or maintain pricing sufficient to realize a return on our investment.

There is significant uncertainty related to the insurance coverage and reimbursement of newly approved products. In the United States, the principal decisions about coverage and reimbursement for new drugs are typically made by the Centers for Medicare & Medicaid Services, or CMS, an agency within the U.S.

Department of Health and Human Services responsible for administering the Medicare program, as CMS decides whether and to what extent a new drug will be covered and reimbursed under Medicare. Private payors tend to follow the coverage reimbursement policies established by CMS to a substantial degree. It is difficult to predict what CMS will decide with respect to reimbursement for products such as ours.

In July 2010, CMS released its final rule to implement a bundled prospective payment system for the treatment of ESRD patients as required by the Medicare Improvements for Patients and Providers Act, or MIPPA. The bundled payment covers a bundle of items and services routinely required for dialysis treatments furnished to Medicare beneficiaries in Medicare-certified ESRD facilities or at their home, including the cost of certain routine drugs. The final rule delayed the inclusion of oral medications without intravenous equivalents in the bundled payment until January 1, 2014 and in April 2014, President Obama signed the Protecting Access to Medicare Act of 2014, which further extendsextended this implementation date to January 1, 2024. Additionally, section 204 of the Stephen Beck, Jr., Achieving a Better Life Experience Act of 2014, or ABLE, provides that payment for oral-only ESRD drugs cannot be made under the ESRD Prospective Payment System prior to January 1, 2025. As a result of the recent legislation, beginning in 2024,2025, ESRD-related drugs willmay be included in the bundle and separate Medicare reimbursement will no longer be available for such drugs, as it is today under Medicare Part D. While it is too early to project the full impact that bundling may have on the industry, the impact could potentially cause dramatic price reductions for tenapanor, and RDX022, if approved. We may be unable to sell tenapanor, and/or RDX022, if approved, to dialysis providers on a profitable basis if third-party payors reduce their current levels of payment, or if our costs of production increase faster than increases in reimbursement levels.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in Europe, Canada, Japan, China and other countries has and will continue to put pressure on the pricing and usage of our product candidates. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medicinal products, but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the United States, the reimbursement for our products may be reduced compared with the United States and may be insufficient to generate commercially reasonable revenue and profits.

Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newnewly approved products approved and, as a result, these caps may not cover or provide adequate payment for our product candidates. We expect to experience pricing pressures in connection with the sale of any of our product candidates due to the trend toward managed healthcare, the increasing influence of health maintenance organizations, and additional legislative changes. The downward pressure on healthcare costs in general, particularly prescription drugs and surgical procedures and other treatments, has become very intense. As a result, increasingly high barriers are being erected to the entry of new products.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our product candidates.

We face an inherent risk of product liability as a result of the clinical testing of our product candidates and will face an even greater risk if we commercialize any products. For example, we may be sued if any product we develop allegedly causes injury or is found to be otherwise unsuitable during product testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the product, negligence, strict liability, and a breach of warranties. Claims could also be asserted under state consumer protection acts. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our product candidates. Even successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

Our inability to obtain and maintain sufficient product liability insurance at an acceptable cost and scope of coverage to protect against potential product liability claims could prevent or inhibit the commercialization of any

products we develop. We currently carry product liability insurance covering use in our clinical trials in the amount of $10.0 million in the aggregate. Although we maintain such insurance, any claim that may be brought against us could result in a court judgment or settlement in an amount that is not covered, in whole or in part, by our insurance or that is in excess of the limits of our insurance coverage. Our insurance policies also have various exclusions and deductibles, and we may be subject to a product liability claim for which we have no coverage. We will have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay such amounts. Moreover, in the future, we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against losses.

We are highly dependent on the services of our President and Chief Executive Officer, Michael Raab, our Executive Vice President and Chief ScientificOperating Officer, Jeremy Caldwell, Ph.D.,Reginald Seeto, MBBS, and our Senior Vice President of DrugChief Development Officer, David Rosenbaum, Ph.D. If we are not able to retain these members of our management team, or recruit additional management, clinical and scientific personnel, our business will suffer.

Our success depends in part on our continued ability to attract, retain and motivate highly qualified personnel. In particular, we are highly dependent upon Michael Raab, our President and Chief Executive Officer, Jeremy Caldwell, Ph.D.,Reginald Seeto, MBBS, our Chief ScientificOperating Officer and David Rosenbaum, Ph.D., our Senior Vice President of Drug Development.Chief Development Officer. The loss of services of any of these individuals could delay or impair the successful development of our product pipeline, completion of our planned clinical trials or the commercialization of our product candidates. Although we have entered into employment agreements with our senior management team, including Mr. Raab and Drs. CaldwellSeeto and Rosenbaum, these agreements are terminable at will with or without notice and, therefore, we may not be able to retain their services as expected. Although we have not historically experienced unique difficulties attracting and retaining qualified employees, we could experience such problems in the future. For example, competition for qualified personnel in the biotechnology and pharmaceuticals field is intense due to the limited number of individuals who possess the skills and experience required by our industry. In addition to the competition for personnel, the San Francisco Bay area in particular is characterized by a high cost of living. As such, we could have difficulty attracting experienced personnel to our company and may be required to expend significant financial resources in our employee recruitment and retention efforts.

We will need to continue to increase the sizeOur internal computer systems, or those of our organization, and weCROs or other contractors or consultants, may experience difficulties in managing growth.

We will need to continue to expand our clinical, managerial, operational, finance and other resources in order to manage our operations, preclinical and clinical trials, research and development activities, regulatory filings, manufacturing and supply activities, and any marketing and commercialization activities. Our management, personnel, systems and facilities currently in place may not be adequate to support this future growth. Our need to effectively execute our growth strategy requires that we:

If we are not able to attract, retain and motivate necessary personnel to accomplish our business objectives, we may experience constraints that will significantly impede the achievement of our development objectives, our ability to raise additional capital and our ability to implement our business strategy.

Significant disruptions of information technology systemsfail or breaches ofsuffer data security breaches, which could adversely affect our business.

Our business is increasingly dependent on critical, complex and interdependent information technology systems to support business processes as well as internal and external communications. TheDespite the implementation of security measures, the size and complexity of our internal computer systems, and those of our CROs and other contractors, make them vulnerable to breakdown, malicious intrusiondamage from computer viruses, unauthorized access, natural disasters, terrorism, war and computer viruses. We have developed systemstelecommunication and processes that are designed to protect our information and prevent data loss and other security breaches, including systems and processes designed to reduce the impact of a security breach; however, such measures cannot provide absolute security, andelectrical failures. While we have taken,not experienced any such system failure, accident or security breach to date, if such an event were to occur and will take, additional security measures to protect against any future intrusion. Any failure to protect against breakdowns, malicious intrusions and computer viruses maycause interruptions in our operations, it could result in a material disruption of our programs. For example, the impairmentloss of productionclinical trial data from completed or ongoing clinical trials for any of our product candidates could result in delays in our regulatory approval efforts and key business processes.significantly increase our costs to recover or reproduce the data. In addition, our systems are potentially vulnerable to data security breaches, whether by employees or others, which may expose sensitive data to unauthorized persons. Such data security breaches could lead to the loss of trade secrets or other intellectual property, or could lead to the public exposure of personal information of our employees, clinical trial patients, customers, and others. Such disruptions and breaches of security could expose us to liability and have a material adverse effect on the operating results and financial condition of our business.

We incur significant costs as a result of operating as a public company, and our management will devote substantial time to new compliance initiatives. We may fail to comply with the rules that apply to public companies, including Section 404 of the Sarbanes-Oxley Act of 2002, which could result in sanctions or other penalties that would harm our business.

We incur significant legal, accounting and other expenses as a public company, including costs resulting from public company reporting obligations under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and regulations regarding corporate governance practices. The listing requirements of The NASDAQNasdaq Global Market require that we satisfy certain corporate governance requirements relating to director independence, distributing annual and

interim reports, stockholder meetings, approvals and voting, soliciting proxies, conflicts of interest and a code of conduct. Our management and other personnel will need to devote a substantial amount of time to ensure that we comply with all of these requirements. Moreover, the reporting requirements, rules and regulations will increase our legal and financial compliance costs and will make some activities more time consuming and costly. Any changes we make to comply with these obligations may not be sufficient to allow us to satisfy our obligations as a public company on a timely basis, or at all. These reporting requirements, rules and regulations, coupled with the increase in potential litigation exposure associated with being a public company, could also make it more difficult for us to attract and retain qualified persons to serve on our board of directors or board committees or to serve as executive officers, or to obtain certain types of insurance, including directors’ and officers’ insurance, on acceptable terms.

In addition, we are in the process of implementing an enterprise resource planning, or ERP, system for our company. An ERP system is intended to combine and streamline the management of our financial, accounting, human resources, sales and marketing and other functions, enabling us to manage operations and track

performance more effectively. However, an ERP system will require us to complete many processes and procedures for the effective use of the system or to run our business using the system, which may result in substantial costs. Additionally, during the conversion process, we may be limited in our ability to convert any business that we acquire to the ERP. Any disruptions or difficulties in implementing or using an ERP system could adversely affect our controls and harm our business, including our ability to forecast or make sales and collect our receivables. Moreover, such disruption or difficulties could result in unanticipated costs and diversion of management attention.

We are subject to Section 404 of The Sarbanes-Oxley Act of 2002, or Section 404, and the related rules of the Securities and Exchange Commission, or SEC, which generally require our management and independent registered public accounting firm to report on the effectiveness of our internal control over financial reporting. Section 404 requires an annual management assessment of the effectiveness of our internal control over financial reporting. However, for so long as we remain an emerging growth company as defined in the Jumpstart Our Business Startups Act of 2012, or JOBS Act, we intend to take advantage of certain exemptions from various reporting requirements that are applicable to public companies that are emerging growth companies, including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404. Once we are no longer an emerging growth company or, if prior to such date, we opt to no longer take advantage of the applicable exemption, we will be required to include an opinion from our independent registered public accounting firm on the effectiveness of our internal controls over financial reporting. We will remain an emerging growth company until the earlier of (1) the last day of the fiscal year following the fifth anniversary of the completion of our IPO (December 31, 2019), (2) the last day of the fiscal year in which we have total annual gross revenue of at least $1.0 billion, or (3) the last day of the fiscal year in which we are deemed to be a large accelerated filer, which means the market value of our common stock that is held by non-affiliates exceeds $700 million as of the prior June 30^th,30th, and (4) the date on which we have issued more than $1.0 billion in non-convertible debt during the prior three-year period.

During the course of our review and testing of our internal controls, we may identify deficiencies and be unable to remediate them before we must provide the required reports. Furthermore, if we have a material weakness in our internal controls over financial reporting, we may not detect errors on a timely basis and our financial statements may be materially misstated. We or our independent registered public accounting firm may not be able to conclude on an ongoing basis that we have effective internal control over financial reporting, which could harm our operating results, cause investors to lose confidence in our reported financial information and cause the trading price of our stock to fall. In addition, as a public company we are required to file accurate and timely quarterly and annual reports with the SEC under the Exchange Act. Any failure to report our financial results on an accurate and timely basis could result in sanctions, lawsuits, delisting of our shares from The NASDAQNasdaq Global Market or other adverse consequences that would materially harm our business.

We have formed in the past, and may form collaboration partnerships in the future, collaboration partnerships, joint ventures and/or licensing arrangements, and we may not realize the benefits of such collaborations.

We mayhave current collaboration partnerships for the commercialization of tenapanor in certain foreign countries, and we currently expect to form additional collaboration partnerships, create joint ventures or enter into additional licensing arrangements with third parties in the United States and abroad that we believe will complement or augment our existing business. In particular, we have formed collaboration partnerships with Kyowa Hakko Kirin Co., Ltd. for commercialization of tenapanor for hyperphosphatemia in Japan and with Shanghai Fosun Pharmaceutical Industrial Development Co. Ltd. for commercialization of tenapanor for hyperphosphatemia and IBS-C in China and related territories. We also expect to form one or more additional collaboration partnerships in connection with the commercialization of tenapanor, outside of the United States, and in the United States for IBS-C to address the primary care market, if approved. We face significant competition in seeking appropriate collaboration partners, and the negotiation process to secure appropriate terms is time-consuming and complex. Any delays in identifying suitable additional collaboration partners and entering into agreements to develop our product candidates could also delay the commercialization of our product candidates, which may reduce their competitiveness even if they reach the market. Moreover, we may not be successful in our efforts to establish such aadditional collaboration partnershippartnerships for tenapanor for IBS-C commercialization or for any future product candidates and programs on terms that

are acceptable to us, or at all. ThisWith respect to tenapanor, this may be because third parties may not view tenapanor for the treatment of IBS-C as having sufficient potential to be successfully commercialized. If we are unable to establish a collaboration partnership for the commercialization of IBS-C in the United States, the commercialization of tenapanor for IBS-C, if approved, could be materially and adversely impacted, which could have a material adverse effect on our business, results of operations, financial condition and prospects. Additionally, we may not be successful in our efforts to establish collaboration partnerships for our other product candidates because our product candidates and programs may be deemed to be at too early of a stage of development for collaborative effort, our research and development pipeline may be viewed as insufficient, and/or third parties may not view oursuch other product candidates and programs as having sufficient potential for commercialization, including the likelihood of an adequate safety and efficacy profile. Even if we are successful in entering into a collaboration partnership or license arrangement, thereThere is no guarantee that our current collaboration partnerships or any such arrangements we enter into in the collaboration

partnershipfuture will be successful, or that any future collaboration partner will commit sufficient resources to the development, regulatory approval, and commercialization effort for such products, or that such alliances will result in us achieving revenues that justify such transactions.

We may engage in strategic transactions that could impact our liquidity, increase our expenses and present significant distractions to our management.

We intend tomay consider strategic transactions, such as acquisitions of companies, asset purchases, and or in-licensing of products, product candidates or technologies. In addition, if we are unable to access capital on a timely basis and on terms that are acceptable to us, we may be forced to restructure certain aspects of our business or identify and complete one or more strategic collaborations or other transactions in order to fund the development or commercialization of tenapanor or certain of our product candidates through the use of alternative structures. Additional potential transactions that we may consider include a variety of different business arrangements, including spin-offs, spin outs, collaboration partnerships, joint ventures, restructurings, divestitures, business combinations and investments. Any such transaction may require us to incur non-recurring or other charges, may increase our near- and long-term expenditures and may pose significant integration challenges or disrupt our management or business, which could adversely affect our operations and financial results. For example, these transactions may entail numerous operational and financial risks, including:

Accordingly, although there can be no assurance that we will undertake or successfully complete any transactions of the nature described above, any transactions that we do complete may be subject to the foregoing or other risks and could have a material adverse effect on our business, results of operations, financial condition and prospects.

If we seek and obtain approval to commercialize our product candidates outside of the United States, or otherwise engage in business outside of the United States, a variety of risks associated with international operations could materially adversely affect our business.

WeIn addition to Japan and China, we or our collaboration partners may decide to seek marketing approval for certain of our product candidates outside the United States or otherwise engage in business outside the United States, including entering into contractual agreements with third-parties. We expect that we will be subject to additional risks related to entering into these international business markets and relationships, including:

Our business involves the use of hazardous materials and we and third-parties with whom we contract must comply with environmental laws and regulations, which can be expensive and restrict how we do business.

Our research and development activities involve the controlled storage, use and disposal of hazardous materials, including the components of our product candidates and other hazardous compounds. We and manufacturers and suppliers with whom we may contract are subject to laws and regulations governing the use, manufacture, storage, handling and disposal of these hazardous materials. In some cases, these hazardous materials and various wastes resulting from their use are stored at our and our manufacturers’ facilities pending their use and disposal. We cannot eliminate the risk of contamination, which could cause an interruption of our commercialization efforts, research and

development efforts and business operations, environmental damage resulting in costly clean-up and liabilities under applicable laws and regulations governing the use, storage, handling and disposal of these materials and specified waste products. We cannot guarantee that that the safety procedures utilized by third-party manufacturers and suppliers with whom we may contract will comply with the standards prescribed by laws and regulations or will eliminate the risk of accidental contamination or injury from these materials. In such an event, we may be held liable for any resulting damages and such liability could exceed our resources and state or federal or other applicable authorities may curtail our use of certain materials and/or interrupt our business operations. Furthermore, environmental laws and regulations are complex, change frequently and have tended to become more stringent. We cannot predict the impact of such changes and cannot be certain of our future compliance. We do not currently carry biological or hazardous waste insurance coverage.

Our internal computer systems, or those of our CROs or other contractors or consultants, may fail or suffer security breaches, which could result in a material disruption of our product development programs.

Despite the implementation of security measures, our internal computer systems and those of our CROs and other contractors and consultants are vulnerable to damage from computer viruses, unauthorized access, natural disasters, terrorism, war and telecommunication and electrical failures. While we have not experienced any such system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our programs. For example, the loss of clinical trial data from completed or ongoing clinical trials for any of our product candidates could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach results in a loss of or damage to our data or applications, or inappropriate disclosure of confidential or proprietary information, we could incur liability and the further development of our product candidates could be delayed.

We may be adversely affected by the current global economic environment.

Our ability to attract and retain collaboration partners or customers, invest in and grow our business and meet our financial obligations depends on our operating and financial performance, which, in turn, is subject to numerous factors, including the prevailing economic conditions and financial, business and other factors beyond our control, such as the rate of unemployment, the number of uninsured persons in the United States, presidential elections, other political influences and inflationary pressures. Our results of operations could be adversely affected by general conditions in the global economy and in the global financial markets. The recent2008 global financial crisis caused extreme volatility and disruptions in the capital and credit markets. We cannot anticipate all the ways in which the current global economic climate and global financial market conditions could adversely impact our business.business in the future.

We are exposed to risks associated with reduced profitability and the potential financial instability of our collaboration partners or customers, many of which may be adversely affected by volatile conditions in the financial markets. For example, unemployment and underemployment, and the resultant loss of insurance, may decrease the demand for healthcare services and pharmaceuticals. If fewer patients are seeking medical care because they do not have insurance coverage, our collaboration partners or customers may experience reductions in revenues, profitability and/or cash flow that could lead them to reduce their support of our programs or financing activities. If collaboration partners or customers are not successful in generating sufficient revenue or are precluded from securing financing, they may not be able to pay, or may delay payment of, accounts receivable that are owed to us. In addition, the volatility in the financial markets could cause significant fluctuations in the interest rate and currency markets. We currently do not hedge for these risks. The foregoing events, in turn, could adversely affect our financial condition and liquidity. In addition, if economic challenges in the United States result in widespread and prolonged unemployment, either regionally or on a national basis, prior to the effectiveness ofor if certain provisions of the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, collectively known as the Affordable Care Act, are repealed, a substantial number of people may become uninsured or underinsured. To the extent economic challenges result in fewer individuals pursuing or being able to afford our product candidates once commercialized, our business, results of operations, financial condition and cash flows could be adversely affected.

We may be adversely affected by earthquakes or other natural disasters and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Our corporate headquarters and other facilities are located in the San Francisco Bay Area, which in the past has experienced severe earthquakes. We do not carry earthquake insurance. Earthquakes or other natural disasters could severely disrupt our operations, and have a material adverse effect on our business, results of operations, financial condition and prospects.

If a natural disaster, power outage or other event occurred that prevented us from using all or a significant portion of our headquarters, that damaged critical infrastructure, such as our enterprise financial systems or manufacturing resource planning and enterprise quality systems, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible for us to continue our business for a substantial period of time. The disaster recovery and business continuity plans we have in place currently are limited and are unlikely to prove adequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our

disaster recovery and business continuity plans, which, particularly when taken together with our lack of earthquake insurance, could have a material adverse effect on our business.

Risks Related to Government Regulation

The regulatory approval processes of the FDA and comparable foreign authorities are lengthy, time consuming and inherently unpredictable. If we are ultimately unable to obtain regulatory approval for our product candidates, our business will be substantially harmed.

The research, testing, manufacturing, labeling, approval, selling, import, export, marketing and distribution of drug products are subject to extensive regulation by the FDA and other regulatory authorities in the United

States and other countries, which regulations differ from country to country. Neither we nor any of our collaboration partners is permitted to market any drug product in the United States until we receive marketing approval from the FDA. We have not submitted an application or obtained marketing approval for any of our product candidates anywhere in the world. Obtaining regulatory approval of a NDA can be a lengthy, expensive and uncertain process. In addition, failure to comply with FDA and other applicable United States and foreign regulatory requirements may subject us to administrative or judicially imposed sanctions or other actions, including:

Prior to obtaining approval to commercialize a drug candidate in the United States or abroad, we or our collaboration partners must demonstrate with substantial evidence from well-controlled clinical trials, and to the satisfaction of the FDA or other foreign regulatory agencies, that such drug candidates are safe and effective for their intended uses. The number of nonclinical studies and clinical trials that will be required for FDA approval varies depending on the drug candidate, the disease or condition that the drug candidate is designed to address, and the regulations applicable to any particular drug candidate. Results from nonclinical studies and clinical trials can be interpreted in different ways. Even if we believe the nonclinical or clinical data for our drug candidates are promising, such data may not be sufficient to support approval by the FDA and other regulatory authorities. Administering drug candidates to humans may produce undesirable side effects, which could interrupt, delay or halt clinical trials and result in the FDA or other regulatory authorities denying approval of a drug candidate for any or all targeted indications.

The time required to obtain approval by the FDA and comparable foreign authorities is unpredictable, typically takes many years following the commencement of clinical studies, and depends upon numerous factors. The FDA and comparable foreign authorities have substantial discretion in the approval process and we may encounter matters with the FDA or such comparable authorities that requires us to expend additional time and resources and delay or prevent the approval of our product candidates. For example, the FDA may require us to conduct additional studies or trials for drug product either prior to or post-approval, such as additional drug-drug interaction studies or safety or efficacy studies or trials, or it may object to elements of our clinical development program such as the number of subjects in our current clinical trials from the United States. In addition, approval policies, regulations or the type and amount of clinical data

necessary to gain approval may change during the course of a product candidate’s clinical development and may vary among jurisdictions, which may cause delays in the approval or result in a decision not to approve an application for regulatory approval. Despite the time and expense exerted, failure can occur at any stage.

Applications for our product candidates could fail to receive regulatory approval for many reasons, including but not limited to the following:

This lengthy approval process, as well as the unpredictability of the results of clinical studies, may result in our failure and/or that of our collaboration partners to obtain regulatory approval to market any of our product candidates, which would significantly harm our business, results of operations, and prospects. Additionally, if the FDA requires that we conduct additional clinical studies, places limitations in our label, delays approval to market our product candidates or limits the use of our products, our business and results of operations may be harmed.

In addition, even if we were to obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications than we request, may not approve the price we intend to charge for our products, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Any of the foregoing scenarios could materially harm the commercial prospects for our product candidates.

Even if we receive regulatory approval for a product candidate, we will be subject to ongoing regulatory obligations and continued regulatory review, which may result in significant additional expense. Additionally, any product candidates, if approved, could be subject to labeling and other restrictions and market withdrawal, and we may be subject to penalties if we fail to comply with regulatory requirements or experience unanticipated problems with our products.

Even if a drug is approved by the FDA or foreign regulatory authorities, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion and recordkeeping for the product will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and

other post-marketing information and reports, registration, as well as continued compliance with cGMPs and GCPsGCP regulations for any clinical trials that we conduct post-approval. As such, we and our third partythird-party contract manufacturers will be subject to continual review and periodic inspections to assess compliance with regulatory requirements. Accordingly, we and others with whom we work must continue to expend time, money, and effort in all areas of regulatory compliance, including manufacturing, production, and quality control. Regulatory authorities may also impose significant restrictions on a product’s indicated uses or marketing or impose ongoing requirements for potentially costly post-marketing studies. Furthermore, any new legislation addressing drug safety issues could result in delays or increased costs to assure compliance.

We will also be required to report certain adverse reactions and production problems, if any, to the FDA, and to comply with requirements concerning advertising and promotion for our products. Promotional communications with respect to prescription drugs are subject to a variety of legal and regulatory restrictions and must be consistent with the information in the product’s approved label. As such, we may not promote our products for indications or uses for which they do not have FDA approval.

Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in, among other things:

Any government investigation of alleged violations of law could require us to expend significant time and resources in response, and could generate negative publicity. Any failure to comply with ongoing regulatory requirements may significantly and adversely affect our ability to commercialize our product candidates. If regulatory sanctions are applied or if regulatory approval is withdrawn, the value of our company and our operating results will be adversely affected.

In addition, the FDA’s policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product candidates. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may lose any marketing approval that we may have obtained, which would adversely affect our business, prospects and ability to achieve or sustain profitability.

We also cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the United States or abroad. For example, certain policies of the Trump administration may impact our business and industry. Namely, the Trump administration has taken several executive actions, including the issuance of a number of Executive Orders, that could impose significant burdens on, or otherwise materially delay, the FDA’s ability to engage in routine regulatory and oversight activities such as

implementing statutes through rulemaking, issuance of guidance, and review and approval of marketing applications. It is difficult to predict how these Executive Orders will be implemented, and the extent to which they will impact the FDA’s ability to exercise its regulatory authority. If these executive actions impose constraints on FDA’s ability to engage in oversight and implementation activities in the normal course, our business may be negatively impacted.

We and our contract manufacturers are subject to significant regulation with respect to manufacturing our product candidates. The manufacturing facilities on which we rely may not continue to meet regulatory requirements or may not be able to meet supply demands.

All entities involved in the preparation of product candidates for clinical studies or commercial sale, including our existing contract manufacturers for our product candidates are subject to extensive regulation. Components of a finished therapeutic product approved for commercial sale or used in late-stage clinical studies must be manufactured in accordance with cGMP.cGMP regulations. These regulations govern manufacturing processes and procedures (including record keeping) and the implementation and operation of quality systems to control and assure the quality of investigational products and products approved for sale. Poor control of production processes can lead to the introduction of contaminants or to inadvertent changes in the properties or stability of our product candidates that may not be detectable in final product testing. We or our contract manufacturers must supply all necessary documentation in support of an NDA or comparable regulatory filing on a timely basis and must adhere to cGMP regulations enforced by the FDA and other regulatory agencies through their facilities inspection programs. The facilities and quality systems of some or all of our third-party contractors must pass a pre-approval inspection for compliance with the applicable regulations as a condition of regulatory approval of our product candidates. In addition, the regulatory authorities may, at any time, audit or inspect a manufacturing facility involved with the preparation of our product candidates or our other potential products or the associated quality systems for compliance with the regulations applicable to the activities being conducted. Although we oversee the contract manufacturers, we cannot control the manufacturing process of, and are completely dependent on, our contract manufacturing partners for compliance with the regulatory requirements. If these facilities do not pass a pre-approval plant inspection, regulatory approval of the products may not be granted or may be substantially delayed until any violations are corrected to the satisfaction of the regulatory authority, if ever. In addition, we have no control over the ability of our contract manufacturers to maintain adequate quality control, quality assurance and qualified personnel.

The regulatory authorities also may, at any time following approval of a product for sale, audit the manufacturing facilities of our third-party contractors. If any such inspection or audit identifies a failure to comply with applicable regulations or if a violation of our product specifications or applicable regulations occurs independent of such an inspection or audit, we or the relevant regulatory authority may require remedial measures that may be costly and/or time consuming for us or a third party to implement, and that may include the temporary or permanent suspension of a clinical study or commercial sales or the temporary or permanent suspension of production or closure of a facility. Any such remedial measures imposed upon us or third parties with whom we contract could materially harm our business.

If we or any of our third-party manufacturers fail to maintain regulatory compliance, the FDA or other applicable regulatory authority can impose regulatory sanctions including, among other things, refusal to approve a pending application for a new drug product, withdrawal of an approval, or suspension of production. As a result, our business, financial condition, and results of operations may be materially harmed.

Additionally, if supply from one approved manufacturer is interrupted, an alternative manufacturer would need to be qualified through an NDA, a supplemental NDA or equivalent foreign regulatory filing, which could result in further delay. The regulatory agencies may also require additional studies if a new manufacturer is relied upon for commercial production. Switching manufacturers may involve substantial costs and is likely to result in a delay in our desired clinical and commercial timelines.

These factors could cause us to incur higher costs and could cause the delay or termination of clinical studies, regulatory submissions, required approvals, or commercialization of our product candidates. Furthermore, if our suppliers fail to meet contractual requirements and we are unable to secure one or more replacement suppliers capable of production at a substantially equivalent cost, our clinical studies may be delayed or we could lose potential revenue.

If we fail to comply or are found to have failed to comply with FDA and other regulations related to the promotion of our products for unapproved uses, we could be subject to criminal penalties, substantial fines or other sanctions and damage awards.

The regulations relating to the promotion of products for unapproved uses are complex and subject to substantial interpretation by the FDA and other government agencies. If tenapanor RDX022 or our other product candidates receive marketing approval, we and our collaboratingcollaboration partners, if any, will be restricted from marketing the product outside of its approved labeling, also referred to as off-label promotion. However, physicians may nevertheless prescribe an approved product to their patients in a manner that is inconsistent with the approved label, which is an off-label use. We intend to implement compliance and training programs designed to ensure that our sales and marketing practices comply with applicable regulations regarding off-label promotion. Notwithstanding these programs, the FDA or other government agencies may allege or find that our practices constitute prohibited promotion of our product candidates for unapproved uses. We also cannot be sure that our employees will comply with company policies and applicable regulations regarding the promotion of products for unapproved uses.

Over the past several years, a significant number of pharmaceutical and biotechnology companies have been the target of inquiries and investigations by various federal and state regulatory, investigative, prosecutorial and administrative entities in connection with the promotion of products for unapproved uses and other sales practices, including the Department of Justice and various U.S. Attorneys’ Offices, the Office of Inspector General of the Department of Health and Human Services, the FDA, the Federal Trade Commission and various state Attorneys General offices. These investigations have alleged violations of various federal and state laws and regulations, including claims asserting antitrust violations, violations of the Food, Drug and Cosmetic Act, the False Claims Act, the Prescription Drug Marketing Act, anti-kickback laws, and other alleged violations in connection with the promotion of products for unapproved uses, pricing and Medicare and/or Medicaid reimbursement. Many of these investigations originate as “qui tam” actions under the False Claims Act. Under the False Claims Act, any individual can bring a claim on behalf of the government alleging that a person or

entity has presented a false claim, or caused a false claim to be submitted, to the government for payment. The person bringing a qui tam suit is entitled to a share of any recovery or settlement. Qui tam suits, also commonly referred to as “whistleblower suits,” are often brought by current or former employees. In a qui tam suit, the government must decide whether to intervene and prosecute the case. If it declines, the individual may pursue the case alone.

If the FDA or any other governmental agency initiates an enforcement action against us or if we are the subject of a qui tam suit and it is determined that we violated prohibitions relating to the promotion of products for unapproved uses, we could be subject to substantial civil or criminal fines or damage awards and other sanctions such as consent decrees and corporate integrity agreements pursuant to which our activities would be subject to ongoing scrutiny and monitoring to ensure compliance with applicable laws and regulations. Any such fines, awards or other sanctions would have an adverse effect on our revenue, business, financial prospects and reputation.

If approved, tenapanor RDX022 and our other product candidates may cause or contribute to adverse medical events that we are required to report to regulatory agencies and if we fail to do so we could be subject to sanctions that would materially harm our business.

Some participants in clinical studies of tenapanor have reported adverse effects after being treated with tenapanor, including diarrhea, nausea, flatulence, abdominal discomfort, abdominal pain, abdominal distention and changes in electrolytes and in the Phase 2b evaluating tenapanor for the treatment of hyperphosphatemia in ESRD patients, we observed that the rate of diarrhea and the discontinuation rate due to diarrhea at the highest doses was higher than expected based upon the results of previous clinical trials.electrolytes. If we are successful in commercializing any products, FDA and foreign regulatory agency regulations require that we report certain information about adverse medical events if those products may have caused or contributed to those adverse events. The timing of our obligation to report would be triggered by the date we become aware of the adverse event as well as the nature of the event. We may fail to report adverse events we become aware of within the prescribed timeframe. We may also fail to appreciate that we have become aware of a reportable adverse event, especially if it is not reported to us as an adverse event or if it is an adverse event that is unexpected or removed in time from the use of our products. If we fail to comply with our reporting obligations, the FDA or a foreign regulatory agency could take action, including criminal prosecution, the imposition of civil monetary penalties, seizure of our products or delay in approval or clearance of future products.

Our employees, independent contractors, principal investigators, CROs, collaboration partners, consultants and vendors may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements.

We are exposed to the risk that our employees, independent contractors, principal investigators, CROs, collaboration partners, consultants and vendors may engage in fraudulent conduct or other illegal activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or unauthorized activities that violate: (1) FDA regulations, including those laws that require the reporting of true, complete and accurate information to the FDA; (2) manufacturing standards; (3) federal and state healthcare fraud and abuse laws and regulations; or (4) laws that require the reporting of true and accurate financial information and data. Specifically, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. These activities also include the improper use of information obtained in the course of clinical trials, which could result in regulatory sanctions and serious harm to our reputation. It is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to be in compliancecomply with such laws or regulations. Additionally, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions

could have a significant impact on our business, including the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, disgorgements, possible exclusion from participation in Medicare, Medicaid and other federal healthcare programs, individual imprisonment, other sanctions, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations, any of which could adversely affect our ability to operate our business and our results of operations.

Failure to obtain regulatory approvals in foreign jurisdictions would prevent us from marketing our products internationally.

In order to market any product in the EEA (which is composed of the 28 Member States of the European Union plus Norway, Iceland and Liechtenstein), and many other foreign jurisdictions, separate regulatory approvals are required. In the EEA, medicinal products can only be commercialized after obtaining a Marketing Authorization, or MA. Before granting the MA, the EMA or the competent authorities of the Member States of the EEA make an assessment of the risk-benefit balance of the product on the basis of scientific criteria concerning its quality, safety and efficacy.

The approval procedures vary among countries and can involve additional clinical testing, and the time required to obtain approval may differ from that required to obtain FDA approval. Clinical trials conducted in one country may not be accepted by regulatory authorities in other countries. Approval by the FDA does not ensure approval by regulatory authorities in other countries, and approval by one or more foreign regulatory authorities does not ensure approval by regulatory authorities in other foreign countries or by the FDA. However, a failure or delay in obtaining regulatory approval in one country may have a negative effect on the regulatory process in others. The foreign regulatory approval process may include all of the risks associated with obtaining FDA approval. We may not be able to file for regulatory approvals or to do so on a timely basis, and even if we do file we may not receive necessary approvals to commercialize our products in any market.

We and our collaboration partners if any, may be subject to healthcare laws, regulation and enforcement; our failure or the failure of any such collaboration partners to comply with these laws could have a material adverse effect on our results of operations and financial conditions.

Although we do not currently have any products on the market, once we begin commercializing our products, we and our collaboration partners if any, may be subject to additional healthcare statutory and regulatory requirements and

enforcement by the federal government and the states and foreign governments in which we conduct our business. The laws that may affect our ability to operate as a commercial organization include:

Because of the breadth of these laws and the narrowness of the statutory exceptions and safe harbors available, it is possible that some of our business activities could be subject to challenge under one or more of such laws. The risk of our being found in violation of these laws is increased by the fact that many of them have not been fully interpreted by the regulatory authorities or the courts, and their provisions are open to a variety of interpretations. Further, the Affordable Care Act, among other things, amends the intent requirement of the federal anti-kickback and criminal health care fraud statutes. A person or entity no longer needs to have actual knowledge of this statute or specific intent to violate it. In addition, the Affordable Care Act provides that the government may assert that a claim including items or services resulting from a violation of the federal anti-kickback statuteAnti-Kickback Statute constitutes a false or fraudulent claim for purposes of the false claims statutes. Any action against us for violation of these laws, even if we successfully defend

against it, could cause us to incur significant legal expenses and divert our management’s attention from the operation of our business. If our operations are found to be in violation of any of the laws described above or any other governmental laws and regulations that apply to us, we may be subject to penalties, including civil and criminal penalties, damages, fines, the curtailment or restructuring of our operations, the exclusion from participation in federal and state healthcare programs and imprisonment, any of which could adversely affect our ability to market our products and adversely impact our financial results.

Legislative or regulatory healthcare reforms in the United States may make it more difficult and costly for us to obtain regulatory clearance or approval of our product candidates and to produce, market and distribute our products after clearance or approval is obtained.

From time to time, legislation is drafted and introduced in Congress that could significantly change the statutory provisions governing the regulatory clearance or approval, manufacture, and marketing of regulated products or the reimbursement thereof. In addition, FDA regulations and guidance are often revised or reinterpreted by the FDA in ways that may significantly affect our business and our products. Any new regulations or revisions or reinterpretations of existing regulations may impose additional costs or lengthen review times of our product candidates. We cannot determine what effect changes in regulations, statutes, legal interpretation or policies, when and if promulgated, enacted or adopted may have on our business in the future. Such changes could, among other things, require:

Each of these would likely entail substantial time and cost and could materially harm our business and our financial results. In addition, delays in receipt of or failure to receive regulatory clearances or approvals for any future products would harm our business, financial condition and results of operations.

In addition, the full impact of recent healthcare reform and other changes in the healthcare industry and in healthcare spending is currently unknown, and may adversely affect our business model. In the United States, the Affordable Care Act was enacted in 2010 with a goal of reducing the cost of healthcare and substantially changing the way healthcare is financed by both government and private insurers. The Affordable Care Act, among other things, increased the minimum Medicaid rebates owed by manufacturers under the Medicaid Drug Rebate Program and extended the rebate program to individuals enrolled in Medicaid managed care organizations, established annual fees and taxes on manufacturers of certain branded prescription drugs, and created a new Medicare Part D coverage gap discount program, in which manufacturers must agree to offer 50% point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D.

In addition, other legislative changes have been proposed and adopted in the United States since the Affordable Care Act was enacted. On August 2, 2011, the Budget Control Act of 2011 created measures for spending reductions by Congress. A Joint Select Committee on Deficit Reduction, tasked with recommending a targeted deficit reduction of at least $1.2 trillion for the years 2013 through 2021, was unable to reach required goals, thereby triggering the legislation’s automatic reduction to several government programs. This included aggregate reductions of Medicare payments to providers of 2% per fiscal year, which went into effect on April 1, 2013. On January 2, 2013, the ATRA was signed into law, which, among other things, further reduced Medicare payments to several providers, including hospitals.

It is likelyWe currently expect that federal and state legislatures within the United States and foreign governments will continue to consider changes to existing healthcare legislation. Welegislation, and we currently expect that the current Presidential Administration and U.S. Congress will seek to modify, or repeal all, or certain provisions of, the Affordable Care Act. There is still uncertainty with respect to any regulatory changes, and such regulatory changes could have an impact on coverage and reimbursement for healthcare items and services covered by plans that were otherwise authorized by the Affordable Care Act. However, we cannot predict the reform initiatives that may be adopted in the future or whether initiatives that have been adopted will be repealed or modified. The continuing efforts of the government, insurance companies, managed care organizations and other payors of healthcare services to contain or reduce costs of healthcare may adversely affect the demand for any drug products for which we may obtain regulatory approval, our ability to set a price that we believe is fair for our products, our ability to obtain coverage and reimbursement approval for a product, our ability to generate revenues and achieve or maintain profitability, and the level of taxes that we are required to pay.

Other legislative changes have been proposed and adopted in the United States since the Affordable Care Act was enacted. These new laws, among other things, included aggregate reductions of Medicare payments to providers of 2% per fiscal year that will remain in effect through 2025 unless additional action is taken by Congress, additional specific reductions in Medicare payments to several types of providers, including hospitals, imaging centers and cancer treatment centers, and an increase in the statute of limitations period for the government to recover overpayments to providers from three to five years. Additionally, individual states have become increasingly active in passing legislation and implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access, and to encourage importation from other countries and bulk purchasing. Recently, there has also been heightened governmental scrutiny over the manner in which drug manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries and proposed bills designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drug products.

Risks Related to Intellectual Property

We may become subject to claims alleging infringement of third parties’ patents or proprietary rights and/or claims seeking to invalidate our patents, which would be costly, time consuming and, if successfully asserted against us, delay or prevent the development and commercialization of tenapanor RDX022 or our other product candidates, or prevent or delay the continued use of our drug discovery and development platform, including APECCS.

There have been many lawsuits and other proceedings asserting infringement or misappropriation of patents and other intellectual property rights in the pharmaceutical and biotechnology industries. There can be no assurances that we will not be subject to claims alleging that the manufacture, use or sale of tenapanor RDX022 or any other product candidates, or that the use of our drug discovery and development platform, including APECCS, infringes existing or future third-party patents, or that such claims, if any, will not be successful. Because patent applications can take many years to issue and may be confidential for 18 months or more after filing, and because pending patent claims can be revised before issuance, there may be applications now pending which may later result in issued patents that may be infringed by the manufacture, use or sale of tenapanor RDX022 or other product candidates or by the use of APECCS. Moreover, we may face patent infringement claims from non-practicing

entities that have no relevant product revenue and against whom our own patent portfolio may thus have no deterrent effect. We may be unaware of one or more issued patents that would be infringed by the manufacture, sale or use of tenapanor RDX022 or our other product candidates, or by the use of APECCS.

We may be subject to third-party patent infringement claims in the future against us or our that would cause us to incur substantial expenses and, if successful against us, could cause us to pay substantial damages, including treble damages and attorney’s fees if we are found to be willfully infringing a third party’s patents. We may be required to indemnify future collaboration partners against such claims. We are not aware of any threatened or pending claims related to these matters, but in the future litigation may be necessary to defend against such claims. If a patent infringement suit were brought against us we could be forced to stop or delay research, development, manufacturing or sales of the product or product candidate that is the subject of the suit. In addition, if a patent infringement suit were brought against us regarding the use of APECCS, we could be forced to stop our use of APECCS or modify our processes to avoid infringement, which may not be possible at a reasonable cost, if at all, and which could result in substantial delay in our use of APECCS for the discovery of new product candidates or potential targets. As a result of patent infringement claims, or in order to avoid potential claims, we may choose to seek, or be required to seek, a license from the third party and would most likely be required to pay license fees or royalties or both. These licenses may not be available on acceptable terms, or at all. Even if we were able to obtain a license, we may be unable to maintain such licenses and the rights may be nonexclusive, which would give our competitors access to the same intellectual property. Ultimately, we could be prevented from commercializing a product, or forced to redesign it, or to cease our use of APECCS or some other aspect of our business operations if, as a result of actual or threatened patent infringement claims, we are unable to enter into licenses on acceptable terms.terms, or unable to maintain such licenses when granted. Even if we are successful in defending against such claims, such litigation can be expensive and time consuming to litigate and would divert management’s attention from our core business. Any of these events could harm our business significantly.

In addition to infringement claims against us, if third parties prepare and file patent applications in the United States that also claim technology similar or identical to ours, we may have to participate in interference or derivation proceedings in the United States Patent and Trademark Office, or the USPTO, to determine which party is entitled to a patent on the disputed invention. We may also become involved in similar opposition proceedings in the European Patent Office or similar offices in other jurisdictions regarding our intellectual property rights with respect to our products and technology. Since patent applications are confidential for a period of time after filing, we cannot be certain that we were the first to file any patent application related to our product candidates.

If our intellectual property related to our product candidates is not adequate or if we are not able to protect our trade secrets or our confidential information, we may not be able to compete effectively in our market.

We rely upon a combination of patents, trade secret protection and confidentiality agreements to protect the intellectual property related to our product candidates, our drug discovery and development platform and our development programs. Any disclosure to or misappropriation by third parties of our confidential or proprietary information could enable competitors to quickly duplicate or surpass our technological achievements, thus eroding our competitive position in our market.

The strength of patents in the biotechnology and pharmaceutical field involves complex legal and scientific questions and can be uncertain. The patent applications that we own or license may fail to result in issued patents in the United States or in foreign countries. Additionally, our research and development efforts may result in product candidates for which patent protection is limited or not available. Even if patents do successfully issue, third parties may challenge the validity, enforceability or scope thereof, which may result in such patents being narrowed, invalidated or held unenforceable. For example, U.S. patents can be challenged by any person before the new USPTO Patent Trial and Appeals Board at any time before one year after that person is served an infringement complaint based on the patents. Patents granted by the European Patent Office may be similarly opposed by any person within nine months from the publication of the grant. Similar proceedings are available in other jurisdictions, and in the United States, Europe and other jurisdictions third parties can raise questions of

validity with a patent office even before a patent has granted. Furthermore, even if they are unchallenged, our patents and patent applications may not adequately protect our intellectual property or prevent others from designing around our claims. For example, a third party may develop a competitive product that provides therapeutic benefits similar to one or more of our product candidates but has a sufficiently different composition to fall outside the scope of our patent protection. If the breadth or strength of protection provided by the patents and patent applications we hold or pursue with respect to our product candidates is successfully challenged, then our ability to commercialize such product candidates could be negatively affected, and we may face unexpected competition that could have a material adverse impact on our business. Further, if we encounter delays in our clinical trials, the period of time during which we or our collaboration partners could market tenapanor or other product candidates under patent protection would be reduced.

Even where laws provide protection, costly and time-consuming litigation could be necessary to enforce and determine the scope of our proprietary rights, and the outcome of such litigation would be uncertain. If we or one of our collaboration partners were to initiate legal proceedings against a third party to enforce a patent covering the product candidate, the defendant could counterclaim that our patent is invalid and/or unenforceable. In patent litigation in the United States, defendant counterclaims alleging invalidity and/or unenforceability are commonplace. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, including lack of novelty, obviousness or non-enablement. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the USPTO, or made a misleading statement, during prosecution. The outcome following legal assertions of invalidity and unenforceability is unpredictable. With respect to validity, for example, we cannot be certain that there is no invalidating prior art, of which we and the patent examiner were unaware during prosecution. If a defendant were to prevail on a legal assertion of invalidity and/or unenforceability against our intellectual property related to a product candidate, we would lose at least part, and perhaps all, of the patent protection on such product candidate. Such a loss of patent protection would have a material adverse impact on our business. Moreover, our competitors could counterclaim that we infringe their intellectual property, and some of our competitors have substantially greater intellectual property portfolios than we do.

We also rely on trade secret protection and confidentiality agreements to protect proprietary know-how that may not be patentable, processes for which patents may be difficult to obtain and/or enforce and any other elements of our drug discovery and development processes that involve proprietary know-how, information or technology that is not covered by patents. Although we require all of our employees, consultants, advisors and any third parties who have access to our proprietary know-how, information or technology, to assign their inventions to us, and endeavor to execute confidentiality agreements with all such parties, we cannot be certain that we have executed such agreements with all parties who may have helped to develop our intellectual property or who had access to our proprietary information, nor can we be certain that our agreements will not be breached by such consultants, advisors or third parties, or by our former employees. The breach of such agreements by individuals or entities who are actively involved in the discovery and design of our potential drug candidates, or in the development of our discovery and design platform, including APECCS, could require us to pursue legal action to protect our trade secrets and confidential information, which would be expensive, and the outcome of which would be unpredictable. If we are not successful in prohibiting the continued breach of such agreements, our business could be negatively impacted. We cannot guarantee that our trade secrets and other confidential proprietary information will not be disclosed or that competitors will not otherwise gain access to our trade secrets or independently develop substantially equivalent information and techniques.

Further, the laws of some foreign countries do not protect proprietary rights to the same extent or in the same manner as the laws of the United States. As a result, we may encounter significant problems in protecting and defending our intellectual property both in the United States and abroad. If we are unable to prevent material disclosure of the intellectual property related to our technologies to third parties, we will not be able to establish or maintain a competitive advantage in our market, which could materially adversely affect our business, results of operations and financial condition.

If we do not obtain patent term extension in the United States under the Hatch-Waxman Act and in foreign countries under similar legislation, thereby potentially extending the term of marketing exclusivity for our product candidates, our business may be materially harmed.

Depending upon the timing, duration and specifics of FDA marketing approval of our product candidates, if any, one of the U.S. patents covering each of such approved product(s) or the use thereof may be eligible for up to five years of patent term restoration under the Hatch-Waxman Act. The Hatch-Waxman Act allows a maximum of one patent to be extended per FDA approved product. Patent term extension also may be available in certain foreign countries upon regulatory approval of our product candidates. Nevertheless, we may not be granted patent term extension either in the United States or in any foreign country because of, for example, failing to apply within applicable deadlines, failing to apply prior to expiration of relevant patents or otherwise failing to satisfy applicable requirements. Moreover, the term of extension, as well as the scope of patent protection during any such extension, afforded by the governmental authority could be less than we request.

If we are unable to obtain patent term extension or restoration, or the term of any such extension is less than we request, the period during which we will have the right to exclusively market our product will be shortened and our competitors may obtain approval of competing products following our patent expiration, and our revenue could be reduced, possibly materially.

Changes in U.S. patent law could diminish the value of patents in general, thereby impairing our ability to protect our products.

As is the case with other biopharmaceutical companies, our success is heavily dependent on intellectual property, particularly patents. Obtaining and enforcing patents in the biopharmaceutical industry involve both technological and legal complexity.

Therefore, obtaining and enforcing biopharmaceutical patents is costly, time consuming and inherently uncertain. In addition, the United States has recently enacted and is currently implementing wide-ranging patent reform legislation, including the Leahy-Smith America Invents Act signed into law on September 16, 2011. That Act includes a number of significant changes to U.S. patent law. These include provisions that affect the way patent applications are prosecuted and new venues and opportunities for competitors to challenge patent portfolios. Because of that Act, the

U.S. patent system is now a “first to file” system, which may make it more difficult to obtain patent protection for inventions and increase the uncertainties and costs surrounding the prosecution of our or our collaboration partners’ patent applications and the enforcement or defense of our or our collaboration partners’ issued patents, all of which could materially adversely affect our business, results of operations and financial condition.

The United States Supreme Court has ruled on several patent cases in recent years, either narrowing the scope of patent protection available in certain circumstances or weakening the rights of patent owners in certain situations. In addition to increasing uncertainty with regard to our ability to obtain patents in the future, this combination of events has created uncertainty with respect to the value of patents once obtained. Depending on future actions by the U.S. Congress, the federal courts, and the USPTO, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce our existing patents and patents that we might obtain in the future.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The USPTO and various foreign patent agencies require compliance with a number of procedural, documentary, fee payment and other provisions to maintain patent applications and issued patents. Noncompliance with these requirements can result in abandonment or lapse of a patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. In such an event, competitors might be able to enter the market earlier than would otherwise have been the case.

We may not be able to enforce our intellectual property rights throughout the world.

The laws of some foreign countries do not protect intellectual property rights to the same extent as the laws of the United States. Many companies have encountered significant problems in protecting and defending intellectual property rights in certain foreign jurisdictions. The legal systems of some countries, particularly developing countries, do not favor the enforcement of patents and other intellectual property protection, especially those relating to life sciences. This could make it difficult for us to stop the infringement of our patents or the misappropriation of our other intellectual property rights. For example, many foreign countries have compulsory licensing laws under which a patent owner must grant licenses to third parties.

Proceedings to enforce our patent rights in foreign jurisdictions, whether or not successful, could result in substantial costs and divert our efforts and attention from other aspects of our business. Furthermore, while we intend to protect our intellectual property rights in our expected significant markets, we cannot ensure that we will be able to initiate or maintain similar efforts in all jurisdictions in which we may wish to market our products. Accordingly, our efforts to protect our intellectual property rights in such countries may be inadequate. In addition, changes in the law and legal decisions by courts in the United States and foreign countries may affect our ability to obtain and enforce adequate intellectual property protection for our technology.

We may be subject to claims that we or our employees have misappropriated the intellectual property, including know-how or trade secrets, of a third party, or claiming ownership of what we regard as our own intellectual property.

Many of our employees, consultants and contractors were previously employed at or engaged by other biotechnology or pharmaceutical companies, including our competitors or potential competitors. Some of these employees, consultants and contractors, executed proprietary rights, non-disclosure and non-competition agreements in connection with such previous employment. Although we try to ensure that our employees, consultants and contractors do not use the intellectual property and other proprietary information or know-how or trade secrets of others in their work for us, and do not perform work for us that is in conflict with their obligations to another employer or any other entity, we may be subject to claims that we or these employees, consultants and contractors have used or disclosed such intellectual property, including know-how, trade secrets or other proprietary information. In addition, an employee, advisor or consultant who performs work for us may have obligations to a third party that are in conflict with their obligations to us, and as a result such third party may claim an ownership interest in the intellectual property arising out of work performed for us. We are not aware of any threatened or pending claims related to these matters, but in the

future litigation may be necessary to defend against such claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel, or access to consultants and contractors. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to management.

In addition, while we typically require our employees, consultants and contractors who may be involved in the development of intellectual property to execute agreements assigning such intellectual property to us, we may be unsuccessful in executing such an agreement with each party who in fact develops intellectual property that we regard as our own, which may result in claims by or against us related to the ownership of such intellectual property. If we fail in prosecuting or defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights. Even if we are successful in prosecuting or defending against such claims, litigation could result in substantial costs and be a distraction to our management and scientific personnel.

Risks Related to Our Common Stock

Our stock price may be volatile and our stockholders may not be able to resell shares of our common stock at or above the price they paid.

The trading price of our common stock is highly volatile and could be subject to wide fluctuations in response to various factors, some of which are beyond our control. These factors include those discussed in this “Risk Factors” section and others such as:

In addition, the stock markets in general, and the markets for pharmaceutical, biopharmaceutical and biotechnology stocks in particular, have experienced extreme volatility that may have been unrelated to the operating performance of the issuer. These broad market fluctuations may adversely affect the trading price or liquidity of our common stock. In the past, when the market price of a stock has been volatile, holders of that stock have sometimes instituted securities class action litigation against the issuer. If any of our stockholders were to bring such a lawsuit against us, we could incur substantial costs defending the lawsuit and the attention

of our management would be diverted from the operation of our business, which could seriously harm our financial position. Any adverse determination in litigation could also subject us to significant liabilities.

One of our principal stockholders ownowns a significant percentage of our stock and, together with our other principal stockholders and management, will be able to exert significant control over matters subject to stockholder approval.

As of December 31, 2015,2017, entities affiliated with New Enterprise Associates, or NEA, a venture capital fund associated with one of our directors, collectively beneficially holdowned approximately 39.65%29.6% of our common stock, and NEA together with our executive officers and directors beneficially owned approximately 34.5% of our capital stock, including outstanding restricted stock units that will vest within 60 days of December 31, 2017, and warrants and stock options exercisable for shares of our common stock and together our executive officers, directors, and affiliated stockholders beneficially owned approximately 42.39%within 60 days of our capital stock, including warrants exercisable for shares of our common stock.December 31, 2017. Therefore, these stockholders may be able to determine all matters requiring stockholder approval, and the entities affiliated with New Enterprise AssociatesNEA alone will have significant ability to influence decisions through their ownership position. For example, these stockholders may be able to influence or control elections of directors, amendments ofto our organizational documents, or approval of any merger, sale of assets, or other major corporate transaction. This may prevent or discourage unsolicited acquisition proposals or offers for our common stock that certain stockholders may feel are in their best interest as one of our stockholders.

If we sell shares of our common stock in future financings, stockholders may experience immediate dilution and, as a result, our stock price may decline.

We may from time to time issue additional shares of common stock at a discount from the current trading price of our common stock. As a result, our stockholders would experience immediate dilution upon the purchase of any shares of our common stock sold at such discount. In addition, as opportunities present themselves, we may enter into financing or similar arrangements in the future, including the issuance of debt securities, preferred stock or common stock. If we issue common stock or securities convertible into common stock, our common stockholders would experience additional dilution and, as a result, our stock price may decline.

Sales of a substantial number of shares of our common stock in the public market could cause our stock price to fall.

If our existing stockholders sell, or indicate an intention to sell, substantial amounts of our common stock in the public market, the trading price of our common stock could decline. As of December 31, 2015,2017, we had 25,964,88647,534,979 shares of common stock outstanding. Of those shares, approximately 10.514.4 million were held by current directors, executive officers and other affiliates, or may otherwise be subject to Rule 144 under the Securities Act of 1933, or the Securities Act.

In addition, asAs of December 31, 2015,2017, approximately 1.30.7 million shares of common stock that are subject toissuable upon vesting of outstanding restricted stock units and approximately 4.0 million shares of common stock issuable upon exercise of outstanding options were eligible for sale in the public market to the extent permitted by the provisions of variousthe applicable vesting schedules, and Rule 144 and Rule 701 under the Securities Act. In addition, as of December 31, 2017, approximately 2.2 million shares that are subject toof common stock issuable upon exercise of outstanding warrants arewere eligible for sale in the public market. If these additional shares of common stock are issued and sold, or if it is perceived that they will be sold, in the public market, the trading price of our common stock could decline.

TheAs of December 31, 2017, the holders of approximately 9.05.6 million shares of our outstanding common stock as of December 31, 2015, are entitled to rights with respect to the registration of their shares under the Securities Act. Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act, except for shares purchased by affiliates. Any sales of securities by these stockholders could have a material adverse effect on the trading price of our common stock.

Provisions in our charter documents and under Delaware law could discourage a takeover that stockholders may consider favorable and may lead to entrenchment of management.

Our amended and restated certificate of incorporation and amended and restated bylaws contain provisions that could significantly reduce the value of our shares to a potential acquirer or delay or prevent changes in control or changes in our management without the consent of our board of directors. The provisions in our charter documents include the following: