Ardelyx (ARDX) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
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Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-36485
Entity Registrant Name	ARDELYX, INC.
Entity Central Index Key	0001437402
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1303944
Entity Address, Address Line One	34175 Ardenwood Boulevard
Entity Address, City or Town	Fremont
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94555
City Area Code	510
Local Phone Number	745-1700
Title of 12(b) Security	Common Stock, par value $0.0001
Trading Symbol	ARDX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		98,709,188
Co-Headquarter
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Entity Address, Address Line One	400 Fifth Avenue
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 84,070	$ 91,032
Short-term investments	94,142	95,452
Accounts receivable	5,783	0
Prepaid expenses and other current assets	21,381	8,202
Total current assets	205,376	194,686
Property and equipment, net	2,292	1,936
Long-term investments	0	2,114
Right-of-use assets, net	1,667	2,274
Other assets	958	552
Total assets	210,293	201,562
Current liabilities:
Accounts payable	5,378	5,626
Accrued compensation and benefits	4,348	5,672
Current portion of operating lease liability	1,412	2,117
Loan payable, current portion	16,667	4,167
Deferred revenue	2,723	4,177
Accrued expenses and other current liabilities	11,262	6,657
Total current liabilities	41,790	28,416
Operating lease liability, net of current portion	397	413
Loan payable, net of current portion	34,348	46,621
Deferred revenue, non-current	2,947	0
Total liabilities	79,482	75,450
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; no shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively.	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized; 98,688,577 and 93,599,975 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively.	10	9
Additional paid-in capital	718,728	680,872
Accumulated deficit	(587,920)	(554,765)
Accumulated other comprehensive income	(7)	(4)
Total stockholders’ equity	130,811	126,112
Total liabilities and stockholders’ equity	$ 210,293	$ 201,562

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	98,688,577	93,599,975
Common stock, shares outstanding	98,688,577	93,599,975

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Total revenues	$ 6,582	$ 1,213
Operating expenses:
Cost of revenue	1,000	0
Research and development	20,456	15,844
General and administrative	17,131	7,138
Total operating expenses	38,587	22,982
Loss from operations	(32,005)	(21,769)
Interest expense	(1,100)	(1,357)
Other income (expense), net	(49)	753
Loss before provision for income taxes	(33,154)	(22,373)
Provision for income taxes	1	0
Net loss	$ (33,155)	$ (22,373)
Net loss per share - basic (in dollars per share)	$ (0.34)	$ (0.25)
Net loss per share - diluted (in dollars per share)	$ (0.34)	$ (0.25)
Shares used in computing net loss per share - basic	97,179,241	88,880,658
Shares used in computing net loss per share - diluted	97,179,241	88,880,658
Comprehensive loss:
Net loss	$ (33,155)	$ (22,373)
Unrealized (losses) gains on available-for-sale securities	(3)	(64)
Comprehensive loss	(33,158)	(22,437)
Collaborative development revenue
Revenues:
Total revenues	1,454	1,175
Product supply revenue
Revenues:
Total revenues	126	38
Licensing revenue
Revenues:
Total revenues	$ 5,002	$ 0

CONDENSED STATEMENTS OF CHANGES

CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive (Loss) Income
Beginning balance at Dec. 31, 2019	$ 186,655	$ 9	$ 647,078	$ (460,452)	$ 20
Beginning balance (shares) at Dec. 31, 2019		88,817,741
Issuance of common stock under employee stock purchase plan	375		375
Issuance of common stock under employee stock purchase plan (shares)		75,804
Issuance of common stock upon exercise of options	$ 216		216
Issuance of common stock upon exercise of options (shares)	100,000	141,551
Stock-based compensation	$ 2,948		2,948
Unrealized (losses) gains on available-for-sale securities	(64)				(64)
Net loss	(22,373)			(22,373)
Ending balance at Mar. 31, 2020	167,757	$ 9	650,617	(482,825)	(44)
Ending balance (shares) at Mar. 31, 2020		89,035,096
Beginning balance at Dec. 31, 2020	126,112	$ 9	680,872	(554,765)	(4)
Beginning balance (shares) at Dec. 31, 2020		93,599,975
Issuance of common stock under employee stock purchase plan	478		478
Issuance of common stock under employee stock purchase plan (shares)		102,208
Issuance of common stock upon exercise of options	$ 20		20
Issuance of common stock upon exercise of options (shares)	10,500	10,507
Issuance of common stock upon vesting of restricted stock units (shares)		35,100
Issuance of common stock in at-the-market offering	$ 34,272	$ 1	34,271
Issuance of common stock in at-the-market offering (shares)		4,940,787
Stock-based compensation	3,087		3,087
Unrealized (losses) gains on available-for-sale securities	(3)				(3)
Net loss	(33,155)			(33,155)
Ending balance at Mar. 31, 2021	$ 130,811	$ 10	$ 718,728	$ (587,920)	$ (7)
Ending balance (shares) at Mar. 31, 2021		98,688,577

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net loss	$ (33,155)	$ (22,373)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	422	492
Amortization of deferred financing costs	157	112
Amortization of deferred compensation for services	77	89
Amortization of (discount) premium on investment securities	157	(138)
Non-cash lease expense	607	502
Stock-based compensation	3,087	2,948
Change in derivative liabilities	36	82
Non-cash interest associated with debt discount accretion	70	127
Changes in operating assets and liabilities:
Accounts receivable	(5,783)	0
Prepaid expenses and other assets	(13,662)	(928)
Accounts payable	(248)	(1,174)
Accrued compensation and benefits	(1,324)	(2,502)
Operating lease liabilities	(721)	(614)
Accrued and other liabilities	7,517	(394)
Deferred revenue	(1,454)	(1,175)
Net cash used in operating activities	(44,217)	(24,946)
Investing activities
Proceeds from maturities and redemptions of investments	35,370	4,000
Purchases of investments	(32,107)	(54,858)
Purchases of property and equipment	(778)	(25)
Net cash provided by (used in) investing activities	2,485	(50,883)
Financing activities
Proceeds from issuance of common stock in at-the-market offering, net of issuance costs	34,272	0
Proceeds from issuance of common stock under equity incentive and stock purchase plans	498	591
Net cash provided by financing activities	34,770	591
Net decrease in cash and cash equivalents	(6,962)	(75,238)
Cash and cash equivalents at beginning of period	91,032	181,133
Cash and cash equivalents at end of period	84,070	105,895
Supplementary disclosure of cash flow information:
Cash paid for interest	963	1,142
Cash paid for income taxes	0	2
Supplementary disclosure of non-cash activities:
Right-of-use assets obtained in exchange for lease obligations	$ 450	$ 5,810

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	ORGANIZATION AND BASIS OF PRESENTATION Ardelyx, Inc. (the “Company,” “we,” “us” or “our”) is a specialized biopharmaceutical company focused on discovering, developing and commercializing innovative first-in-class medicines to enhance the lives of patients with kidney and cardiorenal diseases. We operate in one business segment, which is the research, development and commercialization of biopharmaceutical products. Basis of Presentation These condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules and regulations, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted. These condensed financial statements have been prepared on the same basis as our most recent annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary to present fairly our financial position at March 31, 2021 and results of operations, changes in stockholders’ equity, and cash flows for the interim periods ended March 31, 2021 and 2020. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2020. The results for the three months ended March 31, 2021 are not necessarily indicative of results to be expected for the entire year ending December 31, 2021, or for any other interim period or future year. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes thereto. On an ongoing basis, management evaluates its estimates, including those related to recognition of revenue, clinical trial accruals, contract manufacturing accruals, the fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates. Liquidity As of March 31, 2021, we had cash, cash equivalents and marketable securities of approximately $178.2 million. We believe our current available cash, cash equivalents marketable securities will be sufficient to fund our planned expenditures and meet our obligations for at least 12 months following the filing of this Report on Form 10-Q. Failure to generate product revenue in a timely manner, or raise sufficient capital when needed, could have a negative impact on our financial condition and our ability to pursue our business strategies and could require us to significantly delay, scale back or discontinue one or more of our product development programs, commercialization efforts, or other aspects of our business plans, and our operating results and financial condition would be adversely affected. Summary of Significant Accounting Policies There have been no changes to the significant accounting policies disclosed in our most recent Annual Report on Form 10-K. Recent Accounting Pronouncements New Accounting Pronouncements - Recently Adopted We have adopted no new accounting pronouncements other than those disclosed in our most recent Annual Report on Form 10-K. Recent Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , an amendment which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. Accordingly, these financial assets will be presented at the net amount expected to be collected. The amendment also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. For smaller reporting companies the guidance is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. Management is currently assessing the impact of this standard on our financial statements.

Cash, Cash Equivalents and Shor

Cash, Cash Equivalents and Short-Term Investments	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Short-Term Investments	CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS Securities classified as cash, cash equivalents and short-term investments as of March 31, 2021 and December 31, 2020 are summarized below (in thousands): March 31, 2021 Gross Unrealized Amortized Cost Gains Losses Fair Value Cash and cash equivalents: Cash $ 2,751 $ — $ — $ 2,751 Money market funds 76,676 — — 76,676 Commercial paper 3,500 — — 3,500 Corporate bonds 1,143 — — 1,143 Total cash and cash equivalents 84,070 — — 84,070 Short-term investments Commercial paper $ 73,542 $ 3 $ (4) $ 73,541 Corporate bonds 15,308 — (6) 15,302 U.S. government-sponsored agency bonds 3,264 — — 3,264 Asset-backed securities 2,035 — — 2,035 Total short-term investments 94,149 3 (10) 94,142 Total cash equivalents and short-term investments $ 178,219 $ 3 $ (10) $ 178,212 December 31, 2020 Gross Unrealized Amortized Cost Gains Losses Fair Value Cash and cash equivalents: Cash $ 781 $ — $ — $ 781 Money market funds 88,151 — — 88,151 Commercial paper 2,100 — — 2,100 Total cash and cash equivalents 91,032 — — 91,032 Short-term investments Commercial paper $ 60,631 $ 2 $ (4) $ 60,629 Corporate bonds 24,547 3 (6) 24,544 U.S. government-sponsored agency bonds 9,277 2 — 9,279 U.S. treasury notes 1,000 — — 1,000 Total short-term investments 95,455 7 (10) 95,452 Long-term investments: Corporate bonds $ 2,115 $ (1) 2,114 Total cash equivalents and short-term investments $ 188,602 $ 7 $ (11) $ 188,598 We invest excess cash in marketable securities with high credit ratings. These securities consist primarily of money market funds, commercial paper, corporate bonds, asset-backed securities, and U.S. treasury and agency securities and are classified as “available-for-sale.” All available-for-sale securities held as of March 31, 2021 had contractual maturities of less than one year. Our available-for-sale securities are subject to a periodic impairment review. We consider a debt security to be impaired when the fair value of that security is less than its carrying cost, in which case we would further evaluate the investment to determine whether the security is other-than-temporarily impaired. When we evaluate an investment for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below cost basis, the financial condition or creditworthiness of the issuer and any changes thereto, intent to sell, and whether it is more likely than not we will be required to sell the investment before the recovery of its cost basis. If an investment is other-than-temporarily impaired, we write the investment down through the statement of operations to its fair value and establishes that value as the new cost basis for the investment. Management has determined that none of our available-for-sale securities were other-than-temporarily impaired in any of the periods presented, and as of March 31, 2021, no investment was in a continuous unrealized loss position for more than one year. As such, we believe that it is more likely than not that the investments will be held until maturity or a forecasted recovery of fair value.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1 – Valuations are based on quoted prices in active markets for identical assets or liabilities and readily accessible by us at the reporting date. Examples of assets and liabilities utilizing Level 1 inputs are certain money market funds, U.S. treasuries and trading securities with quoted prices on active markets. Level 2 – Valuations based on inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Examples of assets and liabilities utilizing Level 1 inputs are certain money market funds, U.S. treasuries and trading securities with quoted prices on active markets. Level 3 – Valuations based on unobservable inputs for which there is little or no market data, which require us to develop our own assumptions. The following table sets forth the fair value of our financial assets and liabilities that are measured or disclosed on a recurring basis by level within the fair value hierarchy (in thousands): March 31, 2021 Total Level 1 Level 2 Level 3 Assets: Money market funds $ 76,676 $ 76,676 $ — $ — Commercial paper 77,041 — 77,041 — Corporate bonds 16,445 — 16,445 — U.S. government-sponsored agency bonds 3,264 — 3,264 — Asset-backed securities 2,035 — 2,035 — Total $ 175,461 $ 76,676 $ 98,785 $ — Liabilities: Derivative liability for Exit Fee $ 1,412 $ — $ — $ 1,412 Total $ 1,412 $ — $ — $ 1,412 December 31, 2020 Total Level 1 Level 2 Level 3 Assets: Money market funds $ 88,151 $ 88,151 $ — $ — Commercial paper 62,729 — 62,729 — Corporate bonds 26,658 — 26,658 — U.S. government-sponsored agency bonds 9,279 — 9,279 — U.S. treasury notes 1,000 — 1,000 — Total $ 187,817 $ 88,151 $ 99,666 $ — Liabilities: Derivative liability for Exit Fee $ 1,376 $ — $ — $ 1,376 Total $ 1,376 $ — $ — $ 1,376 Where quoted prices are available in an active market, securities are classified as Level 1. We classify money market funds as Level 1. When quoted market prices are not available for the specific security, we estimate fair value by using benchmark yields, reported trades, broker/dealer quotes and issuer spreads. We classify U.S. government-sponsored agency bonds, U.S. treasury notes, corporate bonds, commercial paper, asset-backed securities and foreign currency derivative contracts as Level 2. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities or derivative liabilities such as the Exit Fee, as defined and discussed in Note 4, are classified as Level 3. The carrying amounts reflected in the balance sheets for cash equivalents, short-term investments, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values at both March 31, 2021 and December 31, 2020, due to their short-term nature. Fair Value of Debt The interest rate of our term loan facility approximates the rate at which we could obtain alternative financing. Therefore, the carrying amount of the term loan facility approximated its fair value at March 31, 2021 and December 31, 2020.

Collaboration and Licensing Agr

Collaboration and Licensing Agreements	3 Months Ended
	Mar. 31, 2021
Collaboration and Licensing Agreements
Collaboration and Licensing Agreements	COLLABORATION AND LICENSING AGREEMENTS Kyowa Kirin Co., Ltd. (“KKC”) 2019 KKC Agreement In November 2019, we entered into a research collaboration and option agreement with KKC (the “2019 KKC Agreement”) for research associated with identifying two preclinical compounds that are ready for designation as development compounds (“DCs”), with one compound inhibiting the first undisclosed target (“Program 1”), and a second inhibiting the second undisclosed target (“Program 2”). Pursuant to the 2019 KKC Agreement, upon completion of the research and designation by the research steering committee of one or more DCs, KKC has the right to execute one or more separate collaborative agreements relating to the development and commercialization of one or both DCs in certain specified territories. Under the terms of the 2019 KKC Agreement, KKC agreed to pay us a non-refundable, non-creditable upfront fee of $10.0 million, payable as follows: the first installment of $5.0 million within 30 days of November 11, 2019 (the “Effective Date”), and the second installment of $5.0 million on the first anniversary of the Effective Date, unless the 2019 KKC Agreement is earlier terminated by KKC due to material breach by us. The term of the 2019 KKC Agreement commenced on the Effective Date and ends on the earliest of: (i) 2 years following the Effective Date, (ii) the nomination of a program DC for both programs, (iii) the nomination of one program DC and the decision by the parties to cease research for the other program, or (iv) the decision by the parties to cease research for both programs. During the three months ended March 31, 2021, we recognized $1.5 million as revenue under the 2019 KKC Agreement in the accompanying condensed statement of operations and comprehensive loss. The aggregate amount of the transaction price allocated to our partially unsatisfied performance obligations as of March 31, 2021 was $2.7 million which is presented in the accompanying condensed balance sheet as deferred revenue. As of March 31, 2021, we expect to recognize the remaining transaction price allocated to our partially unsatisfied performance obligations over the remaining research terms, which is currently expected to extend through the end of 2021. There were no significant changes in estimates associated with the 2019 KKC Agreement during the three months ended March 31, 2021. 2017 KKC Agreement In November 2017, we entered into an exclusive license agreement with KKC (the “2017 KKC Agreement”), for the development, commercialization, and distribution of tenapanor in Japan for cardiorenal indications. We granted KKC an exclusive license to develop and commercialize certain sodium hydrogen exchanger 3 (“NHE3”) inhibitors including tenapanor in Japan for the treatment of cardiorenal diseases and conditions, excluding cancer. We retained the rights to tenapanor outside of Japan, and also retained the rights to tenapanor in Japan for indications other than those stated above. Pursuant to the 2017 KKC Agreement, KKC is responsible for all costs and expenses incurred in the development and commercialization of tenapanor for all licensed indications in Japan. We are responsible for supplying the tenapanor drug substance for KKC’s use in development and commercialization throughout the term of the 2017 KKC Agreement, provided that KKC may exercise an option to manufacture the tenapanor drug substance under certain conditions. We assessed these arrangements in accordance with Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606) and related amendments (“ASC 606”) and concluded that the contract counterparty, KKC, is a customer. Under the terms of the 2017 KKC Agreement, we received $30.0 million in upfront license fees, which was recognized as revenue when the agreement was executed. Based on our assessment, management determined that the license and the manufacturing supply services were its material performance obligations at the inception of the 2017 KKC Agreement, and as such, each of the performance obligations is distinct. In addition to the up-front license fee received of $30.0 million, we may be entitled to receive up to $55.0 million in total development milestones, of which $10.0 million has been recognized as revenue and $5.0 million has been received as of March 31, 2021, and approximately ¥8.5 billion for commercialization milestones, or approximately $76.5 million at the currency exchange rate on March 31, 2021, as well as reimbursement of costs plus a reasonable overhead for the supply of product and high-teen royalties on net sales throughout the term of the agreement. The variable consideration related to the remaining development milestone payments has not been included in the transaction price as these were fully constrained at March 31, 2021. During the three months ended March 31, 2021 and 2020, we recognized $5.0 million and zero, respectively, as licensing revenue upon the achievement of development milestones. The $5.0 million development milestone recognized during the three months ended March 31, 2021 related to the initiation by KKC of phase 3 clinical studies in Japan to evaluate tenapanor for hyperphosphatemia. During the three months ended March 31, 2021, we recognized $0.1 million as product supply revenue related to the manufacturing supply of tenapanor and other materials to KKC pursuant to the 2017 KKC Agreement. Similarly, for the three months ended March 31, 2020, $13.0 thousand was recognized as product supply revenue. During the three months ended March 31, 2021 we recorded a $2.9 million prepayment that is due to us from KKC for the manufacturing of tenapanor drug substance. The prepayment is reflected within prepaid and other current assets and deferred revenue, non-current on our condensed balance sheet as of March 31, 2021. Shanghai Fosun Pharmaceutical Industrial Development Co. Ltd. (“Fosun Pharma”) In December 2017, we entered into an exclusive license agreement with Fosun Pharma (the “Fosun Agreement”), for the development, commercialization and distribution of tenapanor in China for both hyperphosphatemia and IBS-C. We assessed these arrangements in accordance with ASC 606 and concluded that the contract counterparty, Fosun Pharma, is a customer. Under the terms of the Fosun Agreement, we received $12.0 million in upfront license fees which was recognized as revenue when the agreement was executed. Based on management’s assessment, we determined that the license and the manufacturing supply services represented the material performance obligations at the inception of the agreement, and as such, each of the performance obligations is distinct. We may be entitled to additional development and commercialization milestones of up to $110.0 million, as well as reimbursement of cost plus a reasonable overhead for the supply of product and tiered royalties on net sales ranging from the mid-teens to 20%. The variable consideration related to the remaining development milestone payments has not been included in the transaction price as these were fully constrained at March 31, 2021. We have recorded no revenue during the three months ended March 31, 2021 related to the Fosun Agreement. Knight Therapeutics, Inc. (“Knight“) In March 2018, we entered into an exclusive license agreement with Knight (the “Knight Agreement”), for the development, commercialization and distribution of tenapanor in Canada for hyperphosphatemia and IBS-C. We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Knight, is a customer. Based on management’s assessment, we determined that the license and the manufacturing supply services represented the material performance obligations at the inception of the agreement, and as such, each of the performance obligations is distinct. Under the terms of the agreement, we received a $2.3 million nonrefundable, one-time upfront payment in March 2018 and are eligible to receive additional development and commercialization milestone payments worth up to $17.6 million. We are also eligible to receive royalties throughout the term of the agreement, and a transfer price for manufacturing services. The variable consideration related to the remaining development milestone payments has not been included in the transaction price as they were fully constrained at March 31, 2021. AstraZeneca AB (“AstraZeneca”) In June 2015, we entered into a termination agreement with AstraZeneca (the “AstraZeneca Termination Agreement”) pursuant to which we have agreed to pay AstraZeneca (i) future royalties at a royalty rate of 10% of net sales of tenapanor or other NHE3 products by us or our licensees, and (ii) 20% of non-royalty revenue received from a new collaboration partner should we elect to license, or otherwise provide rights to develop and commercialize tenapanor or another NHE3 inhibitor, up to a maximum of $75.0 million in aggregate for (i) and (ii). As of March 31, 2021, to date in aggregate, we have recognized $11.6 million of the $75.0 million, which has been recorded as cost of revenue, and have paid AstraZeneca $10.6 million. For the three months ended March 31, 2021 we recognized and recorded as cost of revenue $1.0 million related to the AstraZeneca Termination Agreement. For the three months ended March 31, 2020 we recognized no cost of revenue related to the AstraZeneca Termination Agreement. Deferred Revenue The following tables present changes in our current and non-current deferred revenue balances during the reporting period. The current deferred revenue balance is attributable entirely to the 2019 KKC Agreement and the non-current deferred revenue balance is attributable entirely to the 2017 KKC Agreement. Deferred revenue - current Balance at December 31, 2020 $ 4,177 Decreases due to revenue recognized in the period for which cash has been received (1,454) Balance at March 31, 2021 $ 2,723 Deferred revenue - non-current Balance at December 31, 2020 $ — Increases to amounts invoiced, for which cash has not yet been received 2,947 Balance at March 31, 2021 $ 2,947

Borrowing

Borrowing	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Borrowing	BORROWING Solar Capital and Western Alliance Bank Loan Agreement On May 16, 2018, we entered into a loan and security agreement (the “Loan Agreement”), with Solar Capital Ltd. and Western Alliance Bank (collectively the “Lenders”). The Loan Agreement provides for a $50.0 million term loan facility with a maturity date of November 1, 2022 (the “Term Loan”). On October 9, 2020, we and the Lenders entered into an amendment to the Loan Agreement (“the 2020 Amendment”) to extend the date through which we are permitted to make interest-only payments on the Term Loan by twelve months to December 1, 2021. The 2020 amendment also requires that if either the FDA does not approve our New Drug Application ("NDA") for tenapanor for the control of serum phosphorus in adult patients with chronic kidney disease ("CKD") on dialysis on or before May 31, 2021 or the U.S. Food and Drug Administration ("FDA") issues a CRL with respect to our NDA Number 213931, then we are to begin principal payments on the earlier of June 1, 2021 or the first day of the month immediately following the date that the FDA issues us a CRL. On April 29, 2021, the FDA extended the Prescription Drug User Fee Act ("PDUFA") date for tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis by three months to July 29, 2021, making it unlikely that the FDA would approve our NDA for tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis on or before May 31, 2021. In May 2021, we and the Lenders entered into an additional amendment to the Loan Agreement (“the 2021 Amendment”) to extend the date by which FDA approval is required in order to continue interest-only payments through December 1, 2021. The 2021 Amendment requires that if either the FDA does not approve our NDA Number 213931 for tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis on or before July 31, 2021 or the FDA issues a complete response letter (“CRL”) for tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis, then we are to begin principal payments on the earlier of August 1, 2021 or the first day of the month immediately following the date that the FDA issues us a CRL. If principal repayments are required to begin prior to December 1, 2021 under the 2021 Amendment then the first principal repayment would include all payments that would have been due if principal repayment had begun on June 1, 2021. We paid a closing fee of 1% of the Term Loan, or $0.5 million, upon the closing of the Term Loan, and $0.1 million upon closing of the 2020 Amendment. Under the Term Loan, we are also obligated to pay a final fee equal to 4.95% of the Term Loan upon the earliest to occur of the maturity date, the acceleration of the Term Loan, the prepayment or repayment of the Term Loan or the termination of the Loan Agreement. We may voluntarily prepay the outstanding Term Loan, subject to a prepayment premium of (i) 3% of the principal amount of the Term Loan if prepaid prior to or on the first anniversary of the Closing Date, (ii) 2% of the principal amount of the Term Loan if prepaid after the first anniversary of the Closing Date through and including the second anniversary of the Closing Date, or (iii) 1% of the principal amount of the Term Loan if prepaid after the second anniversary of the Closing Date and prior to the maturity date. The Term Loan is secured by substantially all our assets, except for our intellectual property and certain other customary exclusions. Additionally, in connection with the Term Loan, we entered into the Exit Fee Agreement, as discussed in Note 6. The Loan Agreement also contains customary events of default that entitle the Lender to cause us indebtedness under the Loan Agreement to become immediately due and payable, and to exercise remedies against us and the collateral securing the Term Loan, including our cash. Upon the occurrence and for the duration of an event of default, an additional default interest rate equal to 4% per annum will apply to all amounts owed under the Loan Agreement. As of March 31, 2021, to our knowledge, there were no facts or circumstances in existence that would give rise to an event of default. As of March 31, 2021, our future payment obligations related to the Term Loan, excluding interest payments and the Exit Fee, are as follows (in thousands): Total repayment obligations $ 52,475 Less: Unamortized discount and debt issuance costs (449) Less: Unaccreted value of final fee (1,011) Loan payable 51,015 Less: Loan payable, current portion (16,667) Loan payable, net of current portion $ 34,348

Derivative Liability

Derivative Liability	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Liability	DERIVATIVE LIABILITY Exit Fee In May 2018, in connection with entering into the Loan Agreement, as defined and discussed in Note 5, we entered into an agreement pursuant to which we agreed to pay $1.5 million in cash (the “Exit Fee”) upon any change of control transaction in respect of the Company or if we obtain both (i) FDA approval of tenapanor for the control of serum phosphorus in adult patients with CKD on dialysis and (ii) FDA approval of tenapanor for the treatment of patients with irritable bowel syndrome with constipation (“IBS-C”), which was obtained on September 12, 2019 when the FDA approved IBSRELA® (tenapanor), a 50 milligram, twice daily oral pill for the treatment of IBS-C in adults (the “Exit Fee Agreement”). Notwithstanding the prepayment or termination of the Term Loan, as defined and discussed in Note 5, our obligation to pay the Exit Fee will expire on May 16, 2028. We concluded that the Exit Fee is a freestanding derivative which should be accounted for at fair value on a recurring basis. The estimated fair value of the Exit Fee is recorded as a derivative liability and included in accrued expenses and other current liabilities on the accompanying condensed balance sheets. The fair value of the derivative liability was determined using a discounted cash flow analysis and is classified as a Level 3 measurement within the fair value hierarchy since our valuation utilized significant unobservable inputs. Specifically, the key assumptions included in the calculation of the estimated fair value of the derivative liability include: (i) our estimates of both the probability and timing of a potential $1.5 million payment to Solar Capital Ltd. and Western Alliance Bank as a result of the FDA approvals and (ii) a discount rate which was derived from our estimated cost of debt, adjusted with current LIBOR (or a comparable successor rate if LIBOR no longer exists). Generally, increases or decreases in the probability of occurrence would result in a directionally similar impact in the fair value measurement of the derivative liability and it is estimated that a 10% increase (decrease), not to exceed 100%, in the probability of occurrence would result in a fair value fluctuation of no more than $0.1 million. Changes in the fair value of recurring measurements included in Level 3 of the fair value hierarchy are presented as other income (expense), net in our statements of operations and were as follows for the three months ended March 31, 2021 and 2020 (in thousands): Three Months Ended March 31, 2021 2020 Fair value of Exit Fee derivative liability at January 1 $ 1,376 $ 969 Change in estimated fair value of derivative liability 36 82 Fair value of Exit Fee derivative liability at March 31 $ 1,412 $ 1,051

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Leases	LEASESAll of our leases are operating leases and each contain customary rent escalation clauses. Certain of the leases have both lease and non-lease components. We have elected to account for each separate lease component and the non-lease components associated with that lease component as a single lease component for all classes of underlying assets. The following table provides additional details of our facility leases presented in the condensed balance sheet as of March 31, 2021 (dollars in thousands): Facilities Right of use assets $ 1,667 Current portion of lease liabilities 1,412 Operating lease liability, net of current portion 397 Total $ 1,809 Weighted-average remaining life (years) 1.60 Weighted-average discount rate 11.23 % Lease costs, which are included in operating expenses in our statements of operations, were as follows (in thousands): Three Months Ended March 31, 2021 2020 Operating lease expense $ 673 $ 648 Cash paid for operating leases $ 1,565 $ 760 The following table summarizes our undiscounted cash payment obligations for our operating lease liabilities as of March 31, 2021: Remainder of 2021 $ 1,463 Thereafter 469 Total undiscounted operating lease payments 1,932 Imputed interest expenses (123) Total operating lease liabilities 1,809 Less: Current portion of operating lease liability (1,412) Operating lease liability, net of current portion $ 397

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITYAt the Market Offerings AgreementIn July 2020, we filed a Form S-3 registration statement, which became effective in August 2020, containing (i) a base prospectus for the offering, issuance and sale by us of up to a maximum aggregate offering price of $250.0 million of our common stock, preferred stock, debt securities, warrants and/or units, from time to time in one or more offerings; and (ii) a prospectus supplement for the offering, issuance and sale by us of up to a maximum aggregate offering price of $100.0 million of our common stock that may be issued and sold, from time to time, under a sales agreement with Jefferies LLC, deemed to be “at the market offerings.” During the three months ended March 31, 2021, we sold 4.9 million shares of our common stock for aggregate gross proceeds of $35.0 million at a weighted average price of $7.09 per share under the Open Market Sales Agreement. In aggregate during the life of the Open Market Sales Agreement, and as of March 31, 2021, we have sold 8.2 million shares of our common stock for gross proceeds of $56.7 million at a weighted average sales price of approximately $6.91 per share. Pursuant to the Open Market Sales Agreement, Jefferies, as sales agent, receives a commission of up to 3.0% of the gross sales price for shares of common stock sold under the Open Market Sales Agreement.

Equity Incentive Plans

Equity Incentive Plans	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Equity Incentive Plans	EQUITY INCENTIVE PLANS Stock Option Plan During the three months ended March 31, 2021, options were granted to employees and members of the board of directors to purchase 2.8 million shares of our common stock. The weighted-average grant-date estimated fair value of options granted during the three months ended March 31, 2021 was $6.51. During the three months ended March 31, 2021, options were exercised to purchase 10.5 thousand shares of our common stock, resulting in net proceeds of approximately $0.5 million. During the three months ended March 31, 2020, options were exercised to purchase 0.1 million shares of or common stock, resulting in net proceeds of approximately $0.6 million. Restricted Stock Units During the three months ended March 31, 2021, we granted 0.9 million restricted stock units (“RSUs”) to our employees that will vest upon employees’ continued service relationship with us. During the three months ended March 31, 2020, we granted 0.9 million restricted stock units to our employees. During both the three months ended March 31, 2021 and March 31, 2020, we granted no performance-based restricted stock units ("PRSUs") to our employees. Employee Stock Purchase Plan In February 2021, we sold 0.2 million shares of our common stock under our employee stock purchase program (the "ESPP"). The shares were purchased by employees at a purchase price of $5.84 per share resulting in proceeds to us of approximately $1.4 million. Issuance of Common Stock for Services Under Our Amended and Restated Non-Employee Director Compensation Program, members of our board of directors may elect to receive shares of our stock in lieu of their cash fees. For the three months ended March 31, 2021 and 2020, we issued no shares of our common stock to members of the board of directors in accordance with the program. Stock-Based Compensation Stock-based compensation expense recognized for stock options, RSUs, PRSUs and the ESPP are recorded as operating expenses in our condensed statements of operations and comprehensive loss, as follows: Three Months Ended March 31, 2021 2020 Research and development $ 1,092 $ 1,058 General and administrative 1,995 1,890 Total $ 3,087 $ 2,948 As of March 31, 2021, our total unrecognized stock-based compensation expense, net of estimated forfeitures, and average remaining vesting period, included the following: Unrecognized Compensation Average Remaining Stock options $ 25,723 3.1 RSUs $ 6,246 3.7 ESPP $ 399 0.4

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	NET LOSS PER SHAREBasic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, less shares subject to repurchase, and excludes any dilutive effects of stock-based awards and warrants. Diluted net loss per common share is computed giving effect to all potential dilutive common shares, including common stock issuable upon exercise of stock options, and unvested restricted common stock and stock units. As we had net losses for the three months ended March 31, 2021 and 2020, all potential common shares were determined to be anti-dilutive. The following table sets forth the computation of net loss per common share: Three Months Ended March 31, 2021 2020 Numerator: Net loss $ (33,155) $ (22,373) Denominator: Weighted average common shares outstanding - basic and diluted 97,179,241 88,880,658 Net loss per share - basic and diluted $ (0.34) $ (0.25) For the three months ended March 31, 2021, the total number of securities that could potentially dilute basic net loss per share in the future that were not included in the computation of diluted net loss per share because the effect would have been antidilutive was 13.0 million. For the three months ended March 31, 2020, the total number of securities that could potentially dilute basic net loss per share in the future that were not included in the computation of diluted net loss per share because the effect would have been antidilutive was 11.9 million.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Contingencies	CONTINGENCIESFrom time to time we may be involved in claims arising in connection with our business. Based on information currently available, management believes that the amount, or range, of reasonably possible losses in connection with any pending actions against us would not be material to our financial condition or cash flows, and no contingent liabilities were accrued as of March 31, 2021 or 2020.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTS On April 29, 2021, the FDA extended the PDUFA date for our NDA for tenapanor for control of serum phosphorus in adult patients with CKD on dialysis by three months to July 29, 2021. In May 2021, we entered into an amendment to our loan and security agreement (the “Loan Agreement”), with Solar Capital Ltd. and Western Alliance Bank (collectively the “Lenders”) to extend the date by which FDA approval is required in order to continue interest-only payments through December 1, 2021. Please see Note 5. Borrowing for additional information.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation These condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules and regulations, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted. These condensed financial statements have been prepared on the same basis as our most recent annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary to present fairly our financial position at March 31, 2021 and results of operations, changes in stockholders’ equity, and cash flows for the interim periods ended March 31, 2021 and 2020. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2020. The results for the three months ended March 31, 2021 are not necessarily indicative of results to be expected for the entire year ending December 31, 2021, or for any other interim period or future year.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes thereto. On an ongoing basis, management evaluates its estimates, including those related to recognition of revenue, clinical trial accruals, contract manufacturing accruals, the fair value of assets and liabilities, income taxes and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements New Accounting Pronouncements - Recently Adopted We have adopted no new accounting pronouncements other than those disclosed in our most recent Annual Report on Form 10-K. Recent Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , an amendment which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The amendment updates the guidance for measuring and recording credit losses on financial assets measured at amortized cost by replacing the “incurred loss” model with an “expected loss” model. Accordingly, these financial assets will be presented at the net amount expected to be collected. The amendment also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income rather than reducing the carrying amount under the current, other-than-temporary-impairment model. For smaller reporting companies the guidance is effective for fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. Early adoption is permitted. Management is currently assessing the impact of this standard on our financial statements.
Fair Value Measurements	Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows: Level 1 – Valuations are based on quoted prices in active markets for identical assets or liabilities and readily accessible by us at the reporting date. Examples of assets and liabilities utilizing Level 1 inputs are certain money market funds, U.S. treasuries and trading securities with quoted prices on active markets. Level 2 – Valuations based on inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Examples of assets and liabilities utilizing Level 1 inputs are certain money market funds, U.S. treasuries and trading securities with quoted prices on active markets. Level 3 – Valuations based on unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.

Cash, Cash Equivalents and Sh_2

Cash, Cash Equivalents and Short-Term Investments (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Schedule of Securities Classified as Cash, Cash Equivalents and Investments	Securities classified as cash, cash equivalents and short-term investments as of March 31, 2021 and December 31, 2020 are summarized below (in thousands): March 31, 2021 Gross Unrealized Amortized Cost Gains Losses Fair Value Cash and cash equivalents: Cash $ 2,751 $ — $ — $ 2,751 Money market funds 76,676 — — 76,676 Commercial paper 3,500 — — 3,500 Corporate bonds 1,143 — — 1,143 Total cash and cash equivalents 84,070 — — 84,070 Short-term investments Commercial paper $ 73,542 $ 3 $ (4) $ 73,541 Corporate bonds 15,308 — (6) 15,302 U.S. government-sponsored agency bonds 3,264 — — 3,264 Asset-backed securities 2,035 — — 2,035 Total short-term investments 94,149 3 (10) 94,142 Total cash equivalents and short-term investments $ 178,219 $ 3 $ (10) $ 178,212 December 31, 2020 Gross Unrealized Amortized Cost Gains Losses Fair Value Cash and cash equivalents: Cash $ 781 $ — $ — $ 781 Money market funds 88,151 — — 88,151 Commercial paper 2,100 — — 2,100 Total cash and cash equivalents 91,032 — — 91,032 Short-term investments Commercial paper $ 60,631 $ 2 $ (4) $ 60,629 Corporate bonds 24,547 3 (6) 24,544 U.S. government-sponsored agency bonds 9,277 2 — 9,279 U.S. treasury notes 1,000 — — 1,000 Total short-term investments 95,455 7 (10) 95,452 Long-term investments: Corporate bonds $ 2,115 $ (1) 2,114 Total cash equivalents and short-term investments $ 188,602 $ 7 $ (11) $ 188,598

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Value of Financial Assets and Liabilities Measured or Disclosed on a Recurring Basis	The following table sets forth the fair value of our financial assets and liabilities that are measured or disclosed on a recurring basis by level within the fair value hierarchy (in thousands): March 31, 2021 Total Level 1 Level 2 Level 3 Assets: Money market funds $ 76,676 $ 76,676 $ — $ — Commercial paper 77,041 — 77,041 — Corporate bonds 16,445 — 16,445 — U.S. government-sponsored agency bonds 3,264 — 3,264 — Asset-backed securities 2,035 — 2,035 — Total $ 175,461 $ 76,676 $ 98,785 $ — Liabilities: Derivative liability for Exit Fee $ 1,412 $ — $ — $ 1,412 Total $ 1,412 $ — $ — $ 1,412 December 31, 2020 Total Level 1 Level 2 Level 3 Assets: Money market funds $ 88,151 $ 88,151 $ — $ — Commercial paper 62,729 — 62,729 — Corporate bonds 26,658 — 26,658 — U.S. government-sponsored agency bonds 9,279 — 9,279 — U.S. treasury notes 1,000 — 1,000 — Total $ 187,817 $ 88,151 $ 99,666 $ — Liabilities: Derivative liability for Exit Fee $ 1,376 $ — $ — $ 1,376 Total $ 1,376 $ — $ — $ 1,376

Collaboration and Licensing A_2

Collaboration and Licensing Agreements (Tables)	3 Months Ended
	Mar. 31, 2021
Collaboration and Licensing Agreements
Schedule of Changes in Deferred Revenue	The following tables present changes in our current and non-current deferred revenue balances during the reporting period. The current deferred revenue balance is attributable entirely to the 2019 KKC Agreement and the non-current deferred revenue balance is attributable entirely to the 2017 KKC Agreement. Deferred revenue - current Balance at December 31, 2020 $ 4,177 Decreases due to revenue recognized in the period for which cash has been received (1,454) Balance at March 31, 2021 $ 2,723 Deferred revenue - non-current Balance at December 31, 2020 $ — Increases to amounts invoiced, for which cash has not yet been received 2,947 Balance at March 31, 2021 $ 2,947

Borrowing (Tables)

Borrowing (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Future Debt Payment Obligations	As of March 31, 2021, our future payment obligations related to the Term Loan, excluding interest payments and the Exit Fee, are as follows (in thousands): Total repayment obligations $ 52,475 Less: Unamortized discount and debt issuance costs (449) Less: Unaccreted value of final fee (1,011) Loan payable 51,015 Less: Loan payable, current portion (16,667) Loan payable, net of current portion $ 34,348

Derivative Liability (Tables)

Derivative Liability (Tables)	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Changes in Fair Value of Derivative Liability	Changes in the fair value of recurring measurements included in Level 3 of the fair value hierarchy are presented as other income (expense), net in our statements of operations and were as follows for the three months ended March 31, 2021 and 2020 (in thousands): Three Months Ended March 31, 2021 2020 Fair value of Exit Fee derivative liability at January 1 $ 1,376 $ 969 Change in estimated fair value of derivative liability 36 82 Fair value of Exit Fee derivative liability at March 31 $ 1,412 $ 1,051

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases [Abstract]
Summary of Additional Details of Leases	The following table provides additional details of our facility leases presented in the condensed balance sheet as of March 31, 2021 (dollars in thousands): Facilities Right of use assets $ 1,667 Current portion of lease liabilities 1,412 Operating lease liability, net of current portion 397 Total $ 1,809 Weighted-average remaining life (years) 1.60 Weighted-average discount rate 11.23 %
Summary of Lease Costs	Lease costs, which are included in operating expenses in our statements of operations, were as follows (in thousands): Three Months Ended March 31, 2021 2020 Operating lease expense $ 673 $ 648 Cash paid for operating leases $ 1,565 $ 760
Summary of Undiscounted Cash Payment Obligations for Operating Lease Liabilities	The following table summarizes our undiscounted cash payment obligations for our operating lease liabilities as of March 31, 2021: Remainder of 2021 $ 1,463 Thereafter 469 Total undiscounted operating lease payments 1,932 Imputed interest expenses (123) Total operating lease liabilities 1,809 Less: Current portion of operating lease liability (1,412) Operating lease liability, net of current portion $ 397

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense Recognized	Stock-based compensation expense recognized for stock options, RSUs, PRSUs and the ESPP are recorded as operating expenses in our condensed statements of operations and comprehensive loss, as follows: Three Months Ended March 31, 2021 2020 Research and development $ 1,092 $ 1,058 General and administrative 1,995 1,890 Total $ 3,087 $ 2,948
Summary of Total Unrecognized Stock-Based Compensation Expense, Net of Estimated Forfeitures	As of March 31, 2021, our total unrecognized stock-based compensation expense, net of estimated forfeitures, and average remaining vesting period, included the following: Unrecognized Compensation Average Remaining Stock options $ 25,723 3.1 RSUs $ 6,246 3.7 ESPP $ 399 0.4

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Net Loss Per Common Share	The following table sets forth the computation of net loss per common share: Three Months Ended March 31, 2021 2020 Numerator: Net loss $ (33,155) $ (22,373) Denominator: Weighted average common shares outstanding - basic and diluted 97,179,241 88,880,658 Net loss per share - basic and diluted $ (0.34) $ (0.25)

Organization and Basis of Pre_3

Organization and Basis of Presentation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of segments | segment	1
Cash, cash equivalents and marketable securities | $	$ 178,219

Cash, Cash Equivalents and Sh_3

Cash, Cash Equivalents and Short-Term Investments - Securities Classified as Cash, Cash Equivalents and Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	$ 84,070	$ 91,032
Cash and cash equivalents, Fair Value	84,070	91,032
Short-term investments
Short-term investments, Amortized Cost	94,149	95,455
Short-term investments, Gross Unrealized Gains	3	7
Short-term investments, Gross Unrealized Losses	(10)	(10)
Short-term investments, Fair Value	94,142	95,452
Long-term investments:
Total cash equivalents and short-term investments, Amortized Cost	178,219
Total cash equivalents and short-term investments, Gross Unrealized Gains	3
Total cash equivalents and short-term investments, Gross Unrealized Losses	(10)
Total cash equivalents and short-term investments, Fair Value	178,212
Total cash equivalents and investments, Amortized Cost		188,602
Total cash equivalents and investments, Gross Unrealized Gains		7
Total cash equivalents and investments, Gross Unrealized Losses		(11)
Total cash equivalents and investments, Fair Value		188,598
Cash
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	2,751	781
Cash and cash equivalents, Fair Value	2,751	781
Money market funds
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	76,676	88,151
Cash and cash equivalents, Fair Value	76,676	88,151
Commercial paper
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	3,500	2,100
Cash and cash equivalents, Fair Value	3,500	2,100
Corporate bonds
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	1,143
Cash and cash equivalents, Fair Value	1,143
Commercial paper
Short-term investments
Short-term investments, Amortized Cost	73,542	60,631
Short-term investments, Gross Unrealized Gains	3	2
Short-term investments, Gross Unrealized Losses	(4)	(4)
Short-term investments, Fair Value	73,541	60,629
Corporate bonds
Short-term investments
Short-term investments, Amortized Cost	15,308	24,547
Short-term investments, Gross Unrealized Gains	0	3
Short-term investments, Gross Unrealized Losses	(6)	(6)
Short-term investments, Fair Value	15,302	24,544
Long-term investments:
Long-term investments, Amortized Cost		2,115
Long-term investments, Gross Unrealized Gains
Long-term investments, Gross Unrealized Losses		(1)
Long-term investments, Fair Value		2,114
U.S. government-sponsored agency bonds
Short-term investments
Short-term investments, Amortized Cost	3,264	9,277
Short-term investments, Gross Unrealized Gains	0	2
Short-term investments, Gross Unrealized Losses	0	0
Short-term investments, Fair Value	3,264	9,279
Asset-backed securities
Short-term investments
Short-term investments, Amortized Cost	2,035
Short-term investments, Gross Unrealized Gains	0
Short-term investments, Gross Unrealized Losses	0
Short-term investments, Fair Value	$ 2,035
U.S. treasury notes
Short-term investments
Short-term investments, Amortized Cost		1,000
Short-term investments, Gross Unrealized Gains		0
Short-term investments, Gross Unrealized Losses		0
Short-term investments, Fair Value		$ 1,000

Cash, Cash Equivalents and Sh_4

Cash, Cash Equivalents and Short-Term Investments - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash and Cash Equivalents [Abstract]
Other-than-temporary impairment	$ 0	$ 0
Investment in continuous unrealized loss position for more than one year	$ 0

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Assets, fair value	$ 175,461	$ 187,817
Liabilities:
Liabilities, fair value	1,412	1,376
Derivative liability for Exit Fee
Liabilities:
Liabilities, fair value	1,412	1,376
Money market funds
Assets:
Assets, fair value	76,676	88,151
Commercial paper
Assets:
Assets, fair value	77,041	62,729
Corporate bonds
Assets:
Assets, fair value	16,445	26,658
U.S. government-sponsored agency bonds
Assets:
Assets, fair value	3,264	9,279
Asset-backed securities
Assets:
Assets, fair value	2,035
U.S. treasury notes
Assets:
Assets, fair value		1,000
Level 1
Assets:
Assets, fair value	76,676	88,151
Liabilities:
Liabilities, fair value	0	0
Level 1 | Derivative liability for Exit Fee
Liabilities:
Liabilities, fair value	0	0
Level 1 | Money market funds
Assets:
Assets, fair value	76,676	88,151
Level 1 | Commercial paper
Assets:
Assets, fair value	0	0
Level 1 | Corporate bonds
Assets:
Assets, fair value	0	0
Level 1 | U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0	0
Level 1 | Asset-backed securities
Assets:
Assets, fair value	0
Level 1 | U.S. treasury notes
Assets:
Assets, fair value		0
Level 2
Assets:
Assets, fair value	98,785	99,666
Liabilities:
Liabilities, fair value	0	0
Level 2 | Derivative liability for Exit Fee
Liabilities:
Liabilities, fair value	0	0
Level 2 | Money market funds
Assets:
Assets, fair value	0	0
Level 2 | Commercial paper
Assets:
Assets, fair value	77,041	62,729
Level 2 | Corporate bonds
Assets:
Assets, fair value	16,445	26,658
Level 2 | U.S. government-sponsored agency bonds
Assets:
Assets, fair value	3,264	9,279
Level 2 | Asset-backed securities
Assets:
Assets, fair value	2,035
Level 2 | U.S. treasury notes
Assets:
Assets, fair value		1,000
Level 3
Assets:
Assets, fair value	0	0
Liabilities:
Liabilities, fair value	1,412	1,376
Level 3 | Derivative liability for Exit Fee
Liabilities:
Liabilities, fair value	1,412	1,376
Level 3 | Money market funds
Assets:
Assets, fair value	0	0
Level 3 | Commercial paper
Assets:
Assets, fair value	0	0
Level 3 | Corporate bonds
Assets:
Assets, fair value	0	0
Level 3 | U.S. government-sponsored agency bonds
Assets:
Assets, fair value	0	0
Level 3 | Asset-backed securities
Assets:
Assets, fair value	$ 0
Level 3 | U.S. treasury notes
Assets:
Assets, fair value		$ 0

Collaboration and Licensing A_3

Collaboration and Licensing Agreements - Narrative (Details) ¥ in Billions	1 Months Ended					3 Months Ended		41 Months Ended	70 Months Ended
	Nov. 30, 2019USD ($)item	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 30, 2017USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2021USD ($)	Nov. 30, 2017JPY (¥)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						$ 6,582,000	$ 1,213,000
Cost of revenue						1,000,000	0
Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						5,002,000	0
Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						126,000	38,000
2019 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized						1,454,000
2019 KKC Agreement | KKC
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fees	$ 10,000,000
First installment of upfront license fees	$ 5,000,000
Term of payment of license fee, first installment	30 days
Second installment of upfront license fees	$ 5,000,000
Term of agreement	2 years
Revenue recognized						1,500,000
Deferred revenue						2,700,000		$ 2,700,000	$ 2,700,000
2019 KKC Agreement | KKC | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of separate collaborative agreements | item	1
2017 KKC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Prepayment due						2,947,000
2017 KKC Agreement | Licensing revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						5,000,000	0	10,000,000
2017 KKC Agreement | Product supply revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						100,000
2017 KKC Agreement | Other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue							13,000
2017 KKC Agreement | KKC
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fees				$ 30,000,000
Potential development milestones				55,000,000
Development milestones received								$ 5,000,000
Potential commercialization milestones				$ 76,500,000						¥ 8.5
Fosun Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue						0
Fosun Agreement | Fosun Pharma
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received			$ 12,000,000
Potential development and commercialization milestones						$ 110,000,000
Threshold percentage of net sales for tiered royalties						20.00%
Knight Agreement | Knight
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment received		$ 2,300,000
Potential development and commercialization milestones		$ 17,600,000
AstraZeneca Termination Agreement | AstraZeneca
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalty revenue					10.00%
Percentage of non-royalty revenue					20.00%
Maximum potential payment per agreement					$ 75,000,000
Cost of revenue						$ 1,000,000	$ 0		11,600,000
Payments made per agreement									$ 10,600,000

Collaboration and Licensing A_4

Collaboration and Licensing Agreements - Deferred Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Current deferred revenue
Beginning balance	$ 4,177
Ending balance	2,723
Non-current deferred revenue
Beginning balance	0
Ending balance	2,947
2019 KKC Agreement
Current deferred revenue
Beginning balance	4,177
Decreases due to revenue recognized in the period for which cash has been received	(1,454)
Ending balance	2,723
2017 KKC Agreement
Non-current deferred revenue
Beginning balance	0
Increases to amounts invoiced, for which cash has not yet been received	2,947
Ending balance	$ 2,947

Borrowing - Narrative (Details)

Borrowing - Narrative (Details) - Term Loan - USD ($)	Oct. 09, 2020	May 16, 2018
Debt Instrument [Line Items]
Term loan face amount		$ 50,000,000
Interest-only payment extension term (in months)	12 months
Closing fee (percent)		1.00%
Closing fee	$ 100,000	$ 500,000
Final fee due upon maturity, acceleration, prepayment, or termination (percent)	4.95%
Additional default interest rate	4.00%
Prior to first anniversary of closing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)	3.00%
After first anniversary through second anniversary of closing date
Debt Instrument [Line Items]
Prepayment premium (as a percent)	2.00%
After second anniversary to maturity date
Debt Instrument [Line Items]
Prepayment premium (as a percent)	1.00%

Borrowing - Future Payment Obli

Borrowing - Future Payment Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Future payment obligations
Total repayment obligations	$ 52,475
Less: Unamortized discount and debt issuance costs	(449)
Less: Unaccreted value of final fee	(1,011)
Loan payable	51,015
Loan payable, current portion	(16,667)	$ (4,167)
Loan payable, net of current portion	$ 34,348	$ 46,621

Derivative Liability - Narrativ

Derivative Liability - Narrative (Details) - Exit Fee derivative - USD ($) $ in Millions	Mar. 31, 2021	May 31, 2018
Derivative [Line Items]
Agreed amount for exit fee upon change of control or regulatory approval	$ 1.5	$ 1.5
Level 3
Derivative [Line Items]
Fair value analysis, percentage change in probability of occurrence	10.00%
Fair value analysis, effect on fair value based on 10% change in probability of occurrence	$ 0.1

Derivative Liability - Changes

Derivative Liability - Changes in Fair Value (Details) - Exit Fee derivative liability - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Change in Fair Value of Derivative Liability
Fair value of Exit Fee derivative liability, beginning	$ 1,376	$ 969
Change in estimated fair value of derivative liability	36	82
Fair value of Exit Fee derivative liability, ending	$ 1,412	$ 1,051

Leases - Additional Lease Infor

Leases - Additional Lease Information (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Right-of-use assets and lease liabilities
Right-of-use assets	$ 1,667	$ 2,274
Current portion of lease liabilities	1,412	2,117
Operating lease liability, net of current portion	397	$ 413
Total operating lease liabilities	$ 1,809
Additional details
Weighted-average remaining life (years)	1 year 7 months 6 days
Weighted-average discount rate	11.23%

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease costs
Operating lease expense	$ 673	$ 648
Cash paid for operating leases	$ 1,565	$ 760

Leases - Undiscounted Cash Paym

Leases - Undiscounted Cash Payment Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Undiscounted cash payment obligations
Remainder of 2021	$ 1,463
Thereafter	469
Total undiscounted operating lease payments	1,932
Imputed interest expenses	(123)
Total operating lease liabilities	1,809
Current portion of operating lease liability	(1,412)	$ (2,117)
Operating lease liability, net of current portion	$ 397	$ 413

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		9 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Jul. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock in at-the-market offering, net of issuance costs	$ 34,272,000	$ 0
Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price				$ 250,000,000
At-the-market offering
Subsidiary, Sale of Stock [Line Items]
Issuance of common stock in at-the-market offering (shares)	4.9		8.2
Proceeds from issuance of common stock in at-the-market offering, net of issuance costs	$ 35,000,000		$ 56,700,000
Weighted-average sales price per share	$ 7.09		$ 6.91
Commission on sale of stock per agreement (percent)	3.00%
At-the-market offering | Common stock
Subsidiary, Sale of Stock [Line Items]
Maximum aggregate offering price				$ 100,000,000

Equity Incentive Plans - Narrat

Equity Incentive Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options granted		2,800,000
Weighted-average grant-date estimated fair value of options granted (in dollars per share)		$ 6.51
Number of options exercised		10,500	100,000
Net proceeds from options exercised		$ 500	$ 600
Proceeds from ESPP		$ 478	$ 375
Board of directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock for services (shares)		0	0
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued under ESPP	200,000
Purchase price (in dollars per share)	$ 5.84
Proceeds from ESPP	$ 1,400
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards granted (in shares)		900,000	900,000
PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of awards granted (in shares)		0	0

Equity Incentive Plans - Stock-

Equity Incentive Plans - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock-based Compensation [Line Items]
Stock-based compensation expense	$ 3,087	$ 2,948
Research and development
Stock-based Compensation [Line Items]
Stock-based compensation expense	1,092	1,058
General and administrative
Stock-based Compensation [Line Items]
Stock-based compensation expense	$ 1,995	$ 1,890

Equity Incentive Plans - Unreco

Equity Incentive Plans - Unrecognized Stock-Based Compensation (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 25,723
Average Remaining Vesting Period (Years)	3 years 1 month 6 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 6,246
Average Remaining Vesting Period (Years)	3 years 8 months 12 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation Expense	$ 399
Average Remaining Vesting Period (Years)	4 months 24 days

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss	$ (33,155)	$ (22,373)
Denominator:
Weighted average common shares outstanding - basic	97,179,241	88,880,658
Weighted average common shares outstanding - diluted	97,179,241	88,880,658
Net loss per share - basic (in dollars per share)	$ (0.34)	$ (0.25)
Net loss per share - diluted (in dollars per share)	$ (0.34)	$ (0.25)

Net Loss Per Share - Narrative

Net Loss Per Share - Narrative (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Anti-dilutive securities not included in computation of diluted net loss per share	13	11.9

Contingencies (Details)

Contingencies (Details) - USD ($)	Mar. 31, 2021	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingent liabilities	$ 0	$ 0