Reata Pharmaceuticals (RETA) 10-K 2 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 28, 2018	Jun. 30, 2017
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	RETA
Entity Registrant Name	REATA PHARMACEUTICALS INC
Entity Central Index Key	1,358,762
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 317,047,608
Common Stock A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		19,990,929
Common Stock B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		6,164,269

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 129,780	$ 84,732
Prepaid expenses and other current assets	3,329	2,551
Total current assets	133,109	87,283
Property and equipment, net	718	819
Other assets	1,510	991
Total assets	135,337	89,093
Liabilities and stockholders’ deficit
Accounts payable	2,067	3,830
Accrued direct research liabilities	12,627	6,151
Other current liabilities	3,511	3,047
Current portion of term loan	1,229
Current portion of deferred revenue	28,183	46,603
Total current liabilities	47,617	59,631
Other long-term liabilities	53	72
Term loan, net of current portion and debt issuance costs	18,385
Deferred revenue, net of current portion	216,255	244,438
Total noncurrent liabilities	234,693	244,510
Commitments and contingencies
Stockholders’ deficit:
Additional paid-in capital	190,145	74,298
Shareholder notes receivable	(2)	(15)
Accumulated deficit	(337,143)	(289,354)
Total stockholders’ deficit	(146,973)	(215,048)
Total liabilities and stockholders’ deficit	135,337	89,093
Common Stock A
Stockholders’ deficit:
Common stock value	20	12
Total stockholders’ deficit	20	12
Common Stock B
Stockholders’ deficit:
Common stock value	7	11
Total stockholders’ deficit	$ 7	$ 11

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common Stock A
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	19,975,340	11,687,974
Common stock, shares outstanding	19,975,340	11,687,974
Common Stock B
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	6,166,166	10,656,920
Common stock, shares outstanding	6,166,166	10,656,920

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaboration revenue
License and milestone	$ 47,103	$ 49,730	$ 50,295
Other revenue	955	126	24
Total collaboration revenue	48,058	49,856	50,319
Expenses
Research and development	71,273	39,453	35,141
General and administrative	23,260	16,603	13,693
Depreciation and amortization	437	682	1,819
Total expenses	94,970	56,738	50,653
Other income (expense)
Investment income	701	214	32
Interest expense	(1,454)
Other income (expense)	(3)
Total other income (expense)	(756)	214	32
Loss before taxes on income	(47,668)	(6,668)	(302)
Provision (benefit) for taxes on income	3	(441)	1,148
Net loss	$ (47,671)	$ (6,227)	$ (1,450)
Net loss per share—basic and diluted	$ (1.99)	$ (0.31)	$ (0.09)
Weighted-average number of common shares used in net loss per share basic and diluted	23,933,309	19,816,635	15,974,974

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Total	IPO	Common Stock A	Common Stock AIPO	Common Stock B	Additional Paid-In Capital	Additional Paid-In CapitalIPO	Shareholder Notes Receivable	Total Accumulated Deficit
Balance, value at Dec. 31, 2014	$ (274,246)				$ 16	$ 7,722		$ (307)	$ (281,677)
Balance, shares at Dec. 31, 2014					15,994,959
Compensation expense related to stock option and restricted stock	1,331					1,331
Cancelation and modification of shareholder notes receivable	706					480		226
Exercise of options, value	$ 39					39
Exercise of options, shares	3,147				3,147
Vesting of prepaid restricted stock	$ 464					464
Net loss	(1,450)								(1,450)
Balance, value at Dec. 31, 2015	(273,156)				$ 16	10,036		(81)	(283,127)
Balance, shares at Dec. 31, 2015					15,998,106
Compensation expense related to stock option and restricted stock	2,367					2,367
Exercise of options, value	$ 5				$ 1	4
Exercise of options, shares	35,207				21,788
Vesting of prepaid restricted stock	$ 464					464
Proceeds from payments of shareholder promissory notes	265					199		66
Public offering of common stock, net of offering costs, value		$ 61,234		$ 6			$ 61,228
Public offering of common stock, net of offering costs, shares				6,325,000
Conversion of common stock Class B to Class A, value			$ 6		$ (6)
Conversion of common stock Class B to Class A, shares			5,362,974		(5,362,974)
Net loss	(6,227)								(6,227)
Balance, value at Dec. 31, 2016	(215,048)		$ 12		$ 11	74,298		(15)	(289,354)
Balance, shares at Dec. 31, 2016			11,687,974		10,656,920
Compensation expense related to stock option and restricted stock	6,530					6,648			(118)
Exercise of options, value	$ 660				$ 1	659
Exercise of options, shares	59,112				59,112
Proceeds from payments of shareholder promissory notes	$ 50					37		13
Public offering of common stock, net of offering costs, value	108,506		$ 3			108,503
Public offering of common stock, net of offering costs, shares			3,737,500
Conversion of common stock Class B to Class A, value			$ 5		$ (5)
Conversion of common stock Class B to Class A, shares			4,549,866		(4,549,866)
Net loss	(47,671)								(47,671)
Balance, value at Dec. 31, 2017	$ (146,973)		$ 20		$ 7	$ 190,145		$ (2)	$ (337,143)
Balance, shares at Dec. 31, 2017			19,975,340		6,166,166

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (47,671)	$ (6,227)	$ (1,450)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	437	682	1,819
Amortization of debt issuance costs	138
Stock-based compensation expense	6,530	2,367	2,075
Provision for deferred taxes on income			17,802
Loss on disposal of property and equipment			2
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(778)	(1,218)	81
Other assets	(519)	(438)	281
Accounts payable	(1,763)	299	2,754
Accrued direct research and other current liabilities	6,973	3,080	(486)
Federal income tax receivable/payable		31,926	(17,903)
Deferred revenue	(46,603)	(49,730)	(49,595)
Net cash used in operating activities	(83,256)	(19,259)	(44,620)
Investing activities
Sales/disposals of fixed assets	1	1	12
Purchases of property and equipment	(344)	(340)	(272)
Net cash used in investing activities	(343)	(339)	(260)
Financing activities
Proceeds from IPO and Follow-On Offering	108,910	64,705
Payments on deferred offering costs	(404)	(2,607)	(864)
Proceeds from long-term debt	20,000
Payments on deferred issuance costs	(524)
Exercise of options	660	4	39
Proceeds from payments of shareholder promissory notes	50	265
Payment of capital lease obligation	(45)	(45)	(45)
Net cash provided by (used in) financing activities	128,647	62,322	(870)
Net increase (decrease) in cash and cash equivalents	45,048	42,724	(45,750)
Cash and cash equivalents at beginning of year	84,732	42,008	87,758
Cash and cash equivalents at end of period	129,780	84,732	42,008
Supplemental disclosures
Cash paid for interest	1,164
Income taxes paid			1,249
Purchases of equipment in accounts payable and other current liabilities	$ 13	$ 20	187
Accrued deferred offering costs			$ 1,129

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	1. Description of Business Reata Pharmaceuticals, Inc. (the Company) is a clinical stage biopharmaceutical company focused on identifying, developing, and commercializing therapeutics to address serious and life-threatening diseases with few or no approved therapies by targeting molecular pathways that regulate cellular metabolism and inflammation. The Company is currently conducting three registrational trials with our lead product candidates, bardoxolone methyl and omaveloxolone, which activate the transcription factor Nrf2 to restore mitochondrial function, reduce oxidative stress, and resolve inflammation. The Company’s lead registrational programs are evaluating its product candidates for the treatment of a rare form of chronic kidney disease (CKD) caused by Alport syndrome, a rare form of degenerative neuromuscular disease called Friedreich’s ataxia (FA), and a rare and severe form of pulmonary arterial hypertension associated with connective tissue disease (CTD-PAH). The Company is developing bardoxolone methyl for the treatment of patients with CKD caused by Alport syndrome and four additional rare forms of CKD. CKD is characterized by a progressive worsening in the rate at which the kidney filters waste products from the blood, called the glomerular filtration rate (GFR). When GFR gets too low, The Company is developing omaveloxolone for the treatment of patients with FA, an inherited, debilitating, and degenerative neuromuscular disorder, caused by mutations in the gene for frataxin, a mitochondrial protein. Patients with FA are typically dependent on wheelchair use 10 to 15 years after disease onset, and their median age of death is in the mid-30s. There are no currently approved therapies for the treatment of FA. Omaveloxolone is being studied in the registrational part 2 of its MOXIe trial. In part 1 of MOXIe, at the optimal dose level, omaveloxolone demonstrated a statistically significant improvement in modified Friedreich’s Ataxia Rating Scale (mFARS) scores of 3.8 points (p=0.0001) versus baseline and a placebo-corrected improvement in mFARS scores of 2.3 points (p=0.06). The Company expects to have top-line data from the MOXIe trial in the second half of 2019. If successful, the Company believes the results from the MOXIe clinical trial, together with other data from the omaveloxolone program, will be sufficient to form the basis of an NDA submission to the FDA seeking approval for omaveloxolone in the United States . The Company is studying bardoxolone methyl in CTD-PAH, which is a serious and progressive disease that leads to heart failure and death. CTD-PAH patients are less responsive to existing vasodilator therapies than I-PAH patients and have a worse prognosis. Bardoxolone methyl is being studied for the treatment of CTD-PAH in the Phase 3 CATALYST trial. The Company initiated CATALYST following review of data from its Phase 2 clinical trial, LARIAT, which demonstrated a statistically significant, mean time averaged increase in 6MWD at 16 weeks in CTD-PAH patients compared to baseline. The Company currently expects to have top-line data from the CATALYST trial in the second half of 2018. However, the trial is designed to enroll between 130 and 200 . In addition to its three registrational programs, the Company is currently conducting a battery of additional clinical and preclinical programs in serious and life-threatening diseases that may provide expansion opportunities for our drug candidates. The Company plans to evaluate data from these earlier stage programs to determine which indications to advance into later stage trials. The Company’s consolidated financial statements include the accounts of all majority-owned subsidiaries. Accordingly, the Company’s share of net earnings and losses from these subsidiaries is included in the consolidated statements of operations. Intercompany profits, transactions, and balances have been eliminated in consolidation. On May 25, 2016, the Company’s registration statement on Form S-1 (File No. 333-208843) relating to its initial public offering (IPO), of its common stock was declared effective by the U.S. Securities and Exchange Commission (SEC). The shares began trading on The NASDAQ Global Market on May 26, 2016. The public offering price of the shares sold in the offering was $11.00 per share. The IPO closed on June 1, 2016 for 6,325,000 shares of its Class A common stock, which included 825,000 shares of its Class A common stock issued pursuant to the over-allotment option granted to the underwriters. The Company received total proceeds from the offering of $60.9 million, net of underwriting discounts and commissions and offering expenses. On August 1, 2017, the Company closed a follow-on underwritten public offering of 3,737,500 shares of its Class A common stock, which included 487,500 shares of its Class A common stock issued pursuant to an option granted to the underwriters, for gross proceeds of $115.9 million. The Company received total proceeds from the offering of $108.5 million, after deducting underwriting discounts and commissions and offering expenses. On November 9, 2017, the Company entered into an at-the-market equity offering sales agreement with Stifel, Nicolaus & Company, Incorporated, that established a program pursuant to which it may offer and sell up to $50,000,000 of its Class A common stock from time to time in at-the-market transactions. As of the filing date of this Form 10-Q, no shares have been sold under this program.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Revenue Recognition The Company has license agreements with AbbVie Inc. (AbbVie) (the AbbVie License Agreement) and Kyowa Hakko Kirin Co., Ltd. (KHK) (the KHK Agreement), under which AbbVie and KHK were granted exclusive licenses to develop and commercialize bardoxolone methyl in the Territory (as defined in the KHK Agreement) and the Licensed Territory (as defined in the AbbVie License Agreement). The terms of the agreements include payments to the Company of nonrefundable, up-front license fees; milestone payments; and royalties on product sales. The Company has a collaboration agreement with AbbVie (the AbbVie Collaboration Agreement) that provides for exclusive licenses to collaborate in the research, development, and worldwide commercialization of targeted Nrf2 activators and to participate on respective joint steering committees. The terms of the agreements include a nonrefundable, up-front payment. The Company recognizes revenue of nonrefundable, up-front license fees and other payments when persuasive evidence that an arrangement exists, services have been rendered or delivery has occurred, the price is fixed and determinable, collection is reasonably assured, and there are no further performance obligations under the agreement. The AbbVie License Agreement, the AbbVie Collaboration Agreement, and the KHK Agreement are all multiple-element arrangements. Multiple-element arrangements are analyzed to determine whether the various performance obligations, or elements, can be separated or whether they must be accounted for as a single unit of accounting. For arrangements entered into prior to January 1, 2011, the following criteria were required to be met in order to separate the elements of the arrangement into different units of accounting: 1. The delivered item or items have value to the customer on a stand-alone basis. 2. There is objective and reliable evidence of fair value of the undelivered item or items. 3. If the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item or items is considered probable and substantially in the control of the vendor. Both the AbbVie License Agreement and the KHK Agreement were executed prior to January 1, 2011, and contained both delivered and undelivered elements in the arrangements. The Company views the key elements of these arrangements as being the exclusive licenses to AbbVie and KHK and participation on joint steering committees. The Company’s involvement in the joint steering committees established under each of these agreements was assessed to determine whether the involvement is an obligation or a right to participate. Based on this assessment, the Company concluded that involvement in the joint steering committees was a substantive deliverable of the arrangement. The Company concluded that objective and reliable evidence of the fair value of the undelivered element of these arrangements (participation on joint steering committees) did not exist; therefore, the Company is accounting for these arrangements as a single unit of accounting. The Company is recognizing revenue associated with the nonrefundable, up-front license fees received under the AbbVie License Agreement and the KHK Agreement ratably over the expected term of the joint steering committee performance obligations, which the Company estimates will be delivered through December 2021 and November 2017 for the KHK Agreement and the AbbVie License Agreement, respectively. The Company continues to participate in regular meetings for the joint steering committee established under the KHK Agreement. At this time, the Company believes its participation in this committee continues to be a substantive performance obligation of the agreements and has concluded that no changes in the estimated revenue recognition periods are warranted. Deferred revenue arises from the excess of cash received over cumulative revenue recognized over the terms of the Company’s continuing obligations. Both the AbbVie License Agreement and the KHK Agreement contain certain clinical development, regulatory, and sales milestones. The Company evaluated each of these milestones at inception of the respective arrangements and concluded that they were substantive milestones, and accordingly, the Company will recognize payments related to the achievement of such milestones, if any, when milestones or net sales levels are achieved and collection is reasonably assured. Factors considered in this determination included scientific and regulatory risks that must be overcome to achieve each milestone, the level of effort and investment required to achieve each milestone, and the monetary value attributed to each milestone. In October 2009, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2009-13, Multiple-Deliverable Revenue Arrangements Revenue Recognition • The License Grants, including various exclusive, co-exclusive, and non-exclusive license grants to AbbVie by the Company related to the Company’s molecules and to jointly discovered new molecules and to the Company by AbbVie related to jointly discovered new molecules; • The Research and Exploratory Development Collaboration, including substantive participation in the Joint Research and Development Incubator Committee established by the agreement; and • The Collaboration Agreement to jointly develop and commercialize second-generation Nrf2 activators, including participation in the Joint Executive Committee, Joint Development Committees, and Joint Marketing Committees established by the agreement. The Company evaluated the deliverables within the AbbVie Collaboration Agreement and concluded that the only delivered element of the arrangement, the License Grants, does not have value to AbbVie on a stand-alone basis. Accordingly, the Company concluded that the various elements of the arrangement cannot be separated into different units of accounting. Therefore, the Company is recognizing revenue associated with the nonrefundable, up-front payment over the estimated 15-year term necessary to execute the joint research, development, and commercialization terms under the agreement. The Company follows ASC 605-28, Revenue Recognition—Milestone Method In June 2013, the Company entered into a research collaboration with a disease advocacy organization. Under the agreement, the Company may be provided milestone payments to fund research and development activities estimated over a two-year period. The Company recorded collaboration revenue totaling $500,000, $0 and $700,000 related to milestone payments during the years ended December 31, 2017, 2016, and 2015, respectively. Cash and Cash Equivalents The Company considers all investments in highly liquid financial instruments with a maturity of three months or less when purchased to be cash equivalents. Investments qualifying as cash equivalents primarily consist of money market funds. The carrying amount of cash equivalents approximates fair value. Investment income consists primarily of interest income on our cash and cash equivalents, which include money market funds. Research and Development Costs All research and development costs are expensed as incurred, including costs for drug supplies used in research and development or clinical studies, property and equipment acquired specifically for a finite research and development project, and nonrefundable deposits incurred at the initiation of research and development activities. Research and development costs consist principally of costs related to clinical studies managed directly by the Company and through contract research organizations, manufacture of clinical drug products for clinical studies, preclinical study costs, discovery research expenses, facilities costs, salaries, and related expenses. AbbVie is not currently participating in the development of bardoxolone methyl for the treatment of CKD caused by Alport syndrome, CTD-PAH, PH-ILD, or other rare kidney diseases, and the Company is therefore incurring all costs for this program. AbbVie has the right to opt-in to these programs at any time during development. Upon opting-in, AbbVie would be required to pay an agreed upon amount of all development costs accumulated up to the point of exercising their opt-in right. All development costs incurred after AbbVie’s opt-in would be split equally. With respect to its omaveloxolone programs and its collaboration agreement with AbbVie, the Company was responsible for a certain initial amount in early development costs before AbbVie began sharing development costs equally. As of April 2016, the Company had incurred all of these initial costs, after which payments from AbbVie with respect to research and development costs incurred by the Company were recorded as a reduction in research and development expenses. The Company’s expenses were reduced $1,434,000 for AbbVie’s share of research and development costs for the twelve months ended December 31, 2016. In September 2016, the Company and AbbVie mutually agreed that the Company would continue unilateral development of omaveloxolone. Therefore, AbbVie no longer co-funds the exploratory development costs of this program, but retains the right to opt back in at certain points in development. Depending upon what point, if any, In December 2017, the Company and KHK entered into the Third Supplement to the KHK Agreement, which allows the Company to begin a portion of the CARDINAL registrational trial in Japan, for which KHK will reimburse costs incurred up to $3,000,000. The Company deemed that this was not a material modification to the KHK Agreement because no payment terms or deliverables were changed. The Company’s expenses were reduced by $515,000 for KHK’s share of the study costs for twelve months ended December 31, 2017. The Company bases its expense accruals related to clinical trials on its estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and contract research organizations that conduct and manage clinical trials on its behalf. The financial terms of these agreements vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing costs, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the Company does not identify costs that it has begun to incur or if the Company underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates. To date, the Company has not experienced significant changes in its estimates of accrued research and development expenses after a reporting period. However, due to the nature of estimates, the Company cannot assure that it will not make changes to its estimates in the future as the Company becomes aware of additional information about the status or conduct of its clinical trials and other research activities. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the following estimated useful lives: Computer equipment 2–5 years Software 3 years Laboratory equipment 5–7 years Office furniture 5 years Office equipment 5 years Leasehold improvements are amortized on the straight-line method over the shorter of the lease term or the estimated useful life of the equipment or improvement. Such amortization is included in depreciation and amortization expense in the consolidated statements of operations. Impairment of Long-Lived Assets The Company periodically evaluates its long-lived assets for potential impairment in accordance with ASC Topic 360, Property, Plant and Equipment Licenses and Patents License and sublicense costs are expensed as incurred and are classified as research and development expenses. Costs associated with filing, prosecuting, enforcing, and maintaining patent rights are expensed as incurred and are classified as general and administrative expenses. Income Taxes The Company accounts for income taxes and the related accounts under the liability method. Deferred tax assets and liabilities are determined based on differences between the financial statement and tax bases of assets and liabilities, and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The measurement of a deferred tax asset is reduced, if necessary, by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes Stock-Based Compensation The Company accounts for its stock-based compensation in accordance with ASC 718 Compensation—Stock Compensation • Expected term—The expected term represents the period that the stock-based awards are expected to be outstanding and is based on the average period the stock options are expected to be outstanding and was based on our historical information of the options exercise patterns and post-vesting termination behavior. • Expected volatility—Since the Company does not have sufficient trading history to estimate the volatility of its common stock, the expected volatility was estimated based on its own historical volatility since its IPO and the average volatility for comparable publicly traded biopharmaceutical companies. When selecting comparable publicly traded biopharmaceutical companies on which the Company based its expected stock price volatility, the Company selected companies with comparable characteristics to the Company, including enterprise value, risk profiles, position within the industry, and historical share price information sufficient to meet the expected life of the stock-based awards. • Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option. • Expected dividend—The Company has no plans to pay dividends on its common stock. Therefore, the company used an expected dividend yield of zero. In addition to the assumptions used in the Black-Scholes option-pricing model, the Company will continue to use judgment in evaluating the expected volatility, and expected terms utilized for its stock-based compensation calculations on a prospective basis. The Company accounts for forfeitures of share-based awards when they occur. Options to purchase shares of the Company’s common stock, and restricted common stock with certain repurchase rights, have been granted or sold to nonemployees at fair value, in connection with research and consulting services provided to the Company, and to employees at fair value, in connection with Stock Purchase and Restriction Agreements. Equity awards generally vest over terms of four or five years. For awards to employees, stock-based compensation expense is recorded ratably through the vesting period for each option award or tranche of restricted stock. Risks and Uncertainties The Company has experienced losses and negative operating cash flows for many years since inception and has no marketed drug or other products. The Company’s ability to generate future revenue depends upon the results of its development programs, whose success cannot be guaranteed. The Company may need to raise additional equity capital in the future in order to fund its operations. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, and filing fees relate to the follow-on offering and IPO, are capitalized. Deferred offering costs totaling $404,000 and $3,471,000 were offset against proceeds from the follow-on offering and IPO, respectively. The Company had $0 in capitalized deferred offering costs as of December 31, 2017 and 2016. Debt Issuance Costs The Company defers costs related to debt issuance and amortizes these costs to interest expense over the term of the debt, using the effective interest method. Debt issuance costs are presented in the balance sheet as a deduction from the carrying amount of the debt liability. Net Income (Loss) per Share Basic and diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include unvested restricted stock, and options to purchase common stock, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. For periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. Fair Value of Financial Instruments Assets and liabilities that are carried at fair value are to be classified and disclosed in one of the following three categories: Level 1: Observable quoted market prices in active markets for identical assets or liabilities; Level 2: Observable inputs other than Level 1, such as quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability; and. Level 3: Unobservable inputs for the asset or liability that are significant to the fair value of the assets or liabilities. At December 31, 2017 and 2016, the Company had no assets or liabilities that are required to be carried at fair value. The book values of the Company’s cash and cash equivalents and other working capital financial assets and liabilities approximate their fair values due to their short term nature. The fair values of the Company’s shareholder notes receivable were immaterial. Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources and includes all components of net income (loss) and other comprehensive income (loss). The other comprehensive income (loss) for the years ended December 31, 2017, 2016, and 2015 were immaterial. Recent Accounting Pronouncements The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue Recognition The new standard is effective for interim and annual periods beginning after December 15, 2017, with early application for interim and annual periods beginning after December 15, 2016, permitted, and allows two methods of adoption: the full retrospective method, which requires the standard to be applied to each prior period presented, or the modified retrospective method, which requires the cumulative effect of adoption to be recognized as an adjustment to opening retained earnings in the period of adoption. The Company is finalizing its assessment of the impact of this guidance on its consolidated results of operations and financial position and disclosures. The Company will apply the modified retrospective method upon adoption of this standard effective January 1, 2018 and expects to recognize a decrease of approximately $2,634,000 to retained earnings. In February 2016, the FASB issued ASU No. 2016-02, Leases Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments In January 2017, the FASB issued ASU No. 2017-03, Accounting Changes and Error Corrections and Investments—Equity Method and Joint Ventures Revenue from Contracts with Customers Leases Financial Instruments—Credit Losses Measurement of Credit Losses on Financial Instruments In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration Agreements	3. Collaboration Agreements AbbVie In December 2011, the Company entered into the AbbVie Collaboration Agreement to jointly research, develop, and commercialize the Company’s portfolio of second and later generation oral Nrf2 activators. The terms of the agreement include payment to the Company of a nonrefundable, up-front payment of $400,000,000. The Company is also participating with AbbVie on joint steering committees. The up-front payment and the Company’s collaboration on research, development, and commercialization are accounted for as a single unit of accounting. Revenue is being recognized ratably through December 2026, which is the estimated minimum period that is needed to complete the deliverables under the terms of the AbbVie Collaboration Agreement. The Company began recognizing revenue related to the up-front payment upon execution of the agreement and, accordingly, recognized approximately $26,647,000, $26,720,000, and $26,647,000 as collaboration revenue during the years ended December 31, 2017, 2016, and 2015, respectively. As of December 31, 2017 and 2016, the Company recorded deferred revenue totaling approximately $238,292,000 and $264,939,000, respectively, of which approximately $26,647,000 and $26,647,000, respectively, is reflected as the current portion of deferred revenue. In September 2010, the Company entered into the AbbVie License Agreement for an exclusive license to develop and commercialize bardoxolone methyl in the Licensee Territory (as defined in the AbbVie License Agreement). The terms of the agreement include payment to the Company of a nonrefundable, up-front license fee of $150,000,000 and additional development and commercial milestone payments. As of December 31, 2017, the Company has received $150,000,000 related to clinical development milestone payments from AbbVie and has the potential in the future to achieve another $50,000,000 from one remaining non-substantive commercial milestone. The AbbVie License Agreement includes additional potential milestones for new compounds other than bardoxolone methyl in cardiovascular and metabolic programs, none of which is planned at this time. The Company also has the potential to achieve tiered royalties ranging from 15 percent to the high 20 percent range, depending on the amount of annual net sales, on net sales by AbbVie in the Licensee Territory. Under certain terminations, the Company may be obligated to pay reverse royalties on net sales in the terminated territory. The up-front license fee and the Company’s participation on joint steering committees were accounted for as a single unit of accounting, and accordingly, revenue was recognized ratably through November 2017, which was the term of the joint steering committees. The Company began recognizing revenue related to the up-front license fee upon transfer of the license of bardoxolone methyl to AbbVie, which occurred in November 2010 and, accordingly, recognized approximately $18,420,000, $21,470,000, and $21,412,000 in collaboration revenue during the years ended December 31, 2017, 2016, and 2015, respectively. As of December 31, 2017 and 2016, the Company recorded deferred revenue totaling approximately $0 and $18,420,000 respectively, of which approximately $0 and $18,420,000, respectively, is reflected as the current portion of deferred revenue. KHK In December 2009, the Company entered into the KHK Agreement for an exclusive license to develop and commercialize bardoxolone methyl in the KHK Licensed Territory. The terms of the agreement include payment to the Company of a nonrefundable, up-front license fee of $35,000,000 and additional development and commercial milestone payments. As of December 31, 2017, the Company received $5,000,000 related to regulatory development milestone payments and $10,000,000 related to clinical development milestone payments from KHK and has the potential in the future to achieve another $82,000,000 from eight non-substantive regulatory milestones and $140,000,000 from four non-substantive commercial milestones. The Company also has the potential to achieve tiered royalties ranging from the low teens to the low 20 percent range, depending on the country of sale and the amount of annual net sales, on net sales by KHK in the KHK Licensee Territory. The Company is participating on a joint steering committee with KHK to oversee the development and commercialization activities related to bardoxolone methyl. Any future milestones and royalties received are subject to mid to lower single digit percent declining tiered commissions to certain consultants as compensation for negotiations of the KHK Agreement. The up-front license fee and the Company’s participation on the joint steering committee are accounted for as a single unit of accounting, and accordingly, revenue was initially being recognized ratably through March 2014, which was the Company’s estimate of its substantive performance obligation period related to the joint steering committee. During 2014, the Company agreed to a change to KHK’s timeline to develop and commercialize bardoxolone methyl, which modified the Company’s estimate of its substantive performance obligation period related to the joint steering committee to December 2021. The Company deemed that this was not a material modification to the KHK Agreement because no payment terms or deliverables were changed and has adjusted its revenue recognition prospectively as of October 2014. The Company began recognizing revenue related to the up-front payment upon transfer of the license and technical knowledge of bardoxolone methyl to KHK, which occurred in December 2009, and, accordingly, recognized approximately $1,536,000, $1,540,000, and $1,536,000 as collaboration revenue during the years ended December 31, 2017, 2016, and 2015, respectively. As of December 31, 2017 and 2016, the Company recorded deferred revenue totaling approximately $6,146,000 and $7,682,000, respectively, of which approximately $1,536,000 and $1,536,000 respectively, is reflected as the current portion of deferred revenue. Under ASU 2014-09, variable consideration must be included in the transaction price when it is determined that it is probable that a significant reversal in the revenue recognized will not occur. We expect to recognize $30,000,000 in deferred revenue related to a milestone from KHK during 2018, which we will ratably recognize in revenue over our estimated performance obligation period ending December 2021. Under the KHK Agreement, the Company will provide KHK with a sufficient supply of bardoxolone methyl to support its development and commercialization efforts. Products provided during development will be charged to KHK at the Company’s direct cost without markup for profit. The Company will report amounts received from these product transactions, net of direct costs incurred, as a component of collaboration revenue. The Company expects the net profit or loss on these product transactions will not be material. Products during commercialization will be charged to KHK with a markup and will be reported as product sales revenue.

Term Loan

Term Loan	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Term Loan	4 . Term Loan On March 31, 2017, the Company entered into a loan and security agreement (Loan Agreement) with Oxford Finance LLC and Silicon Valley Bank (collectively, the Lenders), under which the Lenders agreed to lend the Company up to $35,000,000, issuable in two separate term loans of $20,000,000 (Term A Loan) and $15,000,000 (Term B Loan). On March 31, 2017, the Company borrowed $20,000,000 from the Term A Loan. On November 3, 2017, the Company amended the Loan Agreement (Amended Loan Agreement) to increase the Term B Loan amount to either $20,000,000 or $25,000,000, which extends the interest only period from six to twelve months if the Term B Loan is drawn. The Company may, at its sole discretion, borrow $20,000,000 under Term B Loan by June 29, 2018. The Company may borrow an additional $5,000,000 under the Term B Loan, for a total of $25,000,000, upon the achievement of one of two milestones by the earlier of 90 days after the achievement of a milestone or June 29, 2018. The Company paid an amendment fee of $250,000 on November 8, 2017, upon the execution of the Amended Loan Agreement. If the Company does not draw the Term B Loan by June 29, 2018, the Company would pay an unused line fee of $1,000,000. All outstanding Term Loans will mature on March 1, 2022. Under the Term A Loan, the Company will make interest-only payments for 18 months through October 1, 2018; however, if the Company draws the Term B Loan, the Company will make interest-only payments for 30 months through October 1, 2019. The interest-only payment period will be followed by 41 equal monthly payments, or 29 equal monthly payments if the Company draws the Term B Loan, of principal and interest payments. The Term Loans will bear interest at a floating per annum rate calculated as 7.40% plus the greater of the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue or 0.75%, with a minimum rate of 8.15% and maximum rate of 10.15%. The Company has the option to prepay all, but not less than all, of the borrowed amounts, provided that the Company will be obligated to pay a prepayment fee equal to (a) 3.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made prior to the first anniversary of the applicable funding date of the Term Loan, (b) 2.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made by the second anniversary of the applicable funding date of the Term Loan, or (c) 1.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the second anniversary of the applicable funding date of the Term Loan. The Company will also be required to make a final exit fee payment of 2.95% of the principal balance of all Term Loans outstanding, payable on the earliest of the prepayment of the Term Loans, acceleration of any Term Loan, or at maturity of the Term Loans. The Company may use the proceeds from the Term Loans for working capital and to fund its general business requirements. The Company’s obligations under the Loan Agreement are secured by a first priority security interest in substantially all of its current and future assets, other than its owned intellectual property. The Company has also agreed not to encumber its intellectual property assets, except as permitted by the Loan Agreement. As of December 31, 2017, the Company had $20,000,000 outstanding under the Term A Loan, which was recorded at its initial carrying value of $20,000,000, less discount and debt issuance costs totaling approximately $524,000. In connection with the Term A Loan, the discount and debt issuance costs were recorded as a reduction to debt on its balance sheet and are being accreted to interest expense over the life of the Term A Loan. Additionally, the final exit fee of approximately $590,000 is being accrued over the life of the Term A Loan through interest expense. The Term A Loan has a current effective interest rate of 11.1%. The Company is in compliance with all covenants under the Loan Agreement as of December 31, 2017. The future principal payments for the Company’s Term A Loan as of December 31, 2017 are as follows (in thousands): 2018 $ 975 2019 $ 5,854 2020 $ 5,854 2021 $ 5,854 2022 $ 1,463 $ 20,000

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment consisted of the following as of December 31(in thousands): 2017 2016 Computer equipment and software $ 1,831 $ 2,928 Laboratory equipment 4,654 4,530 Office furniture 1,282 1,273 Office and other equipment 286 273 Leasehold improvements 4,959 4,976 13,012 13,980 Less accumulated depreciation and amortization (12,294 ) (13,161 ) Property and equipment, net $ 718 $ 819

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes The provision for taxes on income consists of the following at December 31 (in thousands): 2017 2016 2015 Current $ 3 $ (441 ) $ (16,654 ) Deferred — — 17,802 Total provision for taxes on income $ 3 $ (441 ) $ 1,148 The following table reconciles the Company’s effective income tax rate from continuing operations to the federal statutory tax rate of 35%: 2017 2016 2015 U.S. federal income taxes 35 % 35 % 35 % Stock-based compensation — (2 ) (80 ) Change in valuation allowance 48 (25 ) (310 ) 2017 Tax Act (111 ) — — Federal tax credits 28 — — Other — (1 ) (25 ) Recorded federal income tax benefit (provision) 0 % 7 % (380 )% The Tax Cuts and Jobs Act of 2017 (the 2017 Tax Act), which was signed into law on December 22, 2017, has resulted in significant changes to the U.S. corporate income tax system. These changes include a federal statutory rate reduction from 35% to 21% and the elimination or reduction in the deductibility of certain credits and limitations, such as tax credits related to designated orphan drugs, net operating losses, interest expense, and executive compensation. The federal statutory rate reduction takes effect on January 1, 2018. As a result of the reduction of federal corporate income tax rates, the Company has estimated a material reduction of $53,113,000 to its deferred tax assets. However, consistent with 2016, its deferred tax assets continue to be fully offset by a valuation allowance in 2017 as the Company cannot currently conclude that it is more likely than not that the remaining deferred tax assets will be utilized. Consequently, although the future potential benefit from its deferred tax assets has been materially reduced by the reduction of federal corporate income tax rates, there was no effect on its 2017 Consolidated Statement of Operations. On December 22, 2017, Staff Accounting Bulletin No. 118 (SAB 118) was issued to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the 2017 Tax Act. In accordance with SAB 118, the Company continues to evaluate the impact of the 2017 Tax Act, which may impact its current conclusions. Any subsequent adjustment to those amounts will be recorded to current tax expense in the third quarter of 2018 when the analysis is complete. Deferred tax assets and liabilities reflect the net effects of net operating loss and tax credit carryovers and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s net deferred tax assets as of December 31 are as follows (in thousands): 2017 2016 Deferred tax assets: Deferred revenue $ 51,332 $ 101,864 Net operating loss 25,601 19,159 Federal tax credits 20,928 — Stock-based compensation 2,118 1,362 Depreciation 318 608 Other 301 392 Subtotal 100,598 123,385 Less: Valuation allowance (100,598 ) (123,385 ) Net deferred tax asset $ — $ — Deferred tax assets are regularly reviewed for recoverability and valuation allowances are established based on historical and projected future taxable losses and the expected timing of the reversals of existing temporary differences. Additionally, as a result of the 2017 Tax Act, the Company’s net deferred tax assets have been re-measured at the reduced federal statutory rate as of December 31, 2017. The Company cannot currently conclude that it is more likely than not that the remaining deferred tax assets will be utilized. Therefore, the Company’s deferred tax assets have been fully offset by a valuation allowance in 2017. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income (including reversals of deferred tax liabilities) during the periods in which those temporary differences will become deductible. The valuation allowance decreased by $22,788,000 in 2017 and increased by $1,685,000 in 2016. As of December 31, 2017, the Company had accumulated net operating losses of approximately $121,911,000 of which $315,000 are subject to an annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (Section 382). Approximately $434,000 of the net operating loss carryforwards expire between fiscal years 2023 and 2024, with the remaining $121,477,000 expiring in fiscal year 2037. As of December 31, 2017, the Company has federal orphan drug tax credit and research and development tax credit carryforwards of $20,805,000 and $123,000, respectively. These credits expire beginning in 2024. As of December 31, 2017, there were no unrecognized tax benefits that, if recognized, would have an impact on the Company’s effective tax rate. The Company currently has a full valuation allowance against its deferred tax assets. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months. The Internal Revenue Service (IRS) completed an examination of the Company’s U.S. income tax returns for 2009, 2011, and 2012, with no significant adjustments, and has commenced an examination of the Company’s U.S. income tax returns for 2013, 2014, and 2015. As of February 28, 2018, the Company has not been notified of any significant proposed adjustments by the IRS. All other tax years remain open to federal tax examination. The Company will classify interest and penalties related to unrecognized tax benefits as part of the income tax provision.

Patents

Patents	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Patents	7. Patents Business intellectual property protection is critical to the Company’s ability to successfully commercialize its product innovations. The potential for litigation regarding the Company’s intellectual property rights always exists and may be initiated by third parties attempting to abridge the Company’s rights, as well as by the Company in protecting its rights. There were no patent matters outstanding at December 31, 2017, 2016, or 2015.

Licenses

Licenses	12 Months Ended
	Dec. 31, 2017
License Agreements [Abstract]
Licenses	8 . Licenses The proprietary rights and technical information covered by various patent and patent applications, which are discussed in more detail below, have been licensed by the Company from third parties, including stockholders. These licenses will continue for the life of the respective patent or until terminated by either party. Certain agreements call for the payment of royalties on product sales over the life of the patents. The term of all agreements is through the useful lives of the licensed patents or for a period of 15 to 20 years for technology rights, for which there are no applicable patent rights. Bardoxolone Methyl and Nrf2 Activators In July 2004, the Company entered into an exclusive technology and patent license agreement (the 2004 CDDO License Agreement) with two academic institutions for certain patents and patent applications, known as the CDDO Patents. The Company has the right to sublicense these patents. In the event of a sublicense, the terms of the contract require the Company to pay the licensors sublicense fees based on a percentage of total compensation received that varies depending on the phase of development of a drug candidate as of the time of the sublicense. The Company agreed to pay a royalty on net sales of any products developed as a result of the license, an annual license fee, and various milestone fees, and issued shares of its common stock as consideration for the license. In January 2009, the Company filed a patent application claiming the use of bardoxolone methyl and related compounds in treating CKD, endothelial dysfunction, cardiovascular disease, and related disorders. Several of the original inventors of these compounds at an academic institution were named as co-inventors on this application, along with several company employees. Consequently, the Company and the academic institution are co-owners of this patent application. In December 2009, the Company entered into an agreement with the academic institution (the 2009 Method of Use License Agreement) that provides the Company with an exclusive worldwide license to the academic institution’s rights in these applications and any resulting patents. The Company agreed to pay a limited super-royalty on product sales that occur during the effective term of the original patents (as discussed above), a royalty on product sales that occur after the effective term of the original patents, a sublicense fee, an annual license fee, and various milestone fees. Other Technologies In September 2014, the Company entered into two exclusive technology and patent license agreements with the University of Kansas for certain patents and patent applications related to small molecule modulators of heat shock proteins. The Company has the right to sublicense these patents. In the event of a sublicense, the terms of the contract require the Company to pay the licensors sublicense fees based on a percentage of total compensation received that varies depending on the phase of development of a drug candidate as of the time of the sublicense. The Company paid non-refundable license issue fees and agreed to pay royalties on net sales of any products developed as a result of the licenses, annual license fees, various milestone fees, including reimbursement of sunk-in patent expenses, and fees for sponsored research performed by the University of Kansas as consideration for the licenses.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock	9. Common Stock The Company records all issued shares of common stock at fair value on the dates of issuance. Reserved Shares At December 31, 2017, common stock reserved for issuance is as follows: Outstanding common stock options under the 2007 Long Term Incentive Plan 3,220,350 Outstanding common stock options under standalone option agreements 31,346 Common stock available for future grant under the 2007 Long Term Incentive Plan 107,322 Total common shares reserved for future issuance 3,359,018

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Convertible Preferred Stock	10. Convertible Preferred Stock As of December 31, 2017 and 2016, there were no shares of convertible preferred stock issued and outstanding. On January 4, 2016, the Company filed its Tenth Amended and Restated Certificate of Incorporation, which removed all previous designations and authorized 100,000,000 undesignated shares of convertible preferred stock.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	11. Stock-Based Compensation The 2007 Long Term Incentive Plan (the 2007 LTIP) provides for awards of restricted stock, both nonstatutory stock options and incentive stock options within the meaning of Section 422 of the Internal Revenue Code of 1986, as amended, and other incentive awards and rights to purchase shares of the Company’s common stock. A total of 107,322 shares of common stock have been reserved for issuance under the 2007. As of December 31, 2017, no shares of restricted stock are outstanding under the 2007 LTIP, and options to purchase 3,251,696 shares have been granted and are outstanding under the 2007 LTIP. These options vest over the stated periods through 2022. Additional detail on stock compensation costs can be found below. Stock Options Stock options are granted to employees at exercise prices equal to the estimated fair market value of the Company’s stock at the dates of grant. Stock options under the 2007 LTIP generally vest over four or five years and have a term of ten years. Compensation cost is recognized over the vesting period of the options using the straight-line attribution method. The Company accounts for forfeitures when they occur. The following table summarizes stock-based compensation expense reflected in the consolidated statements of operations (in thousands): Years Ended December 31 2017 2016 2015 Research and development $ 2,409 $ 1,121 $ 671 General and administrative 4,121 1,246 1,404 $ 6,530 $ 2,367 $ 2,075 The following table summarizes stock option activity as of December 31, 2017, and changes during the years ended December 31, 2017 under the 2007 LTIP and standalone option agreements: Number of Options Weighted- Average Exercise Price Outstanding at January 1, 2017 2,311,146 17.18 Granted 1,044,848 25.00 Exercised (59,112 ) 11.14 Forfeited (45,120 ) 14.68 Expired (66 ) 25.21 Outstanding at December 31, 2017 3,251,696 19.83 Exercisable at December 31, 2017 939,137 17.12 At December 31, 2017, 3,251,696 stock options are fully vested or are expected to vest and have a weighted-average outstanding term of 8.56 years and a weighted-average exercise price of $19.83. Exercisable stock options have a weighted-average outstanding term of 7.08 years. Restricted Stock Restricted and unvested stock has occasionally, in the past, been sold or granted to employees of the Company under the 2007 LTIP and the Amended and Restated 2002 Stock Option and Incentive Plan (the 2002 Plan), which was the predecessor equity incentive plan to the 2007 LTIP. The fair value of restricted stock is determined based on the estimated fair value of the Company’s common stock at the date of grant. Restricted stock generally vests straight-line over a period of four or five years, provided the employee remains in the service of the Company. Compensation cost is recognized on a straight-line basis over the vesting period. Shares of restricted and unvested stock purchased by employees are released from their restriction at each vesting date; however, these shares remain pledged to the Company and are nontransferable until the related shareholder note receivable has been paid. The shareholder notes receivable related to the restricted stock sold to employees are usually due in full one year after the final release date of the stock. At December 31, 2017 and 2016, a total of 1,193,780 shares of restricted stock had been issued through the 2007 LTIP and the 2002 Plan. At December 31, 2017 and 2016, no shares of restricted stock are outstanding. The fair value of restricted stock vested in fiscal 2017 and 2016 was $0 and $356,000, respectively. Fair Value Estimates The Company’s determination of the fair value of stock-based payment awards on the date of grant using the Black-Scholes option pricing model is affected by many factors, including the stock price and a number of highly complex and subjective variables. These variables include, but are not limited to, the Company’s stock price volatility over the expected term of the awards, and estimates of the expected option term. The weighted-average assumptions used in the Black-Scholes option pricing model were as follows: Years Ended December 31 2017 2016 2015 Dividend yield — % — % — % Volatility 75.14 % 72.77 % 74.93 % Risk-free interest rate 2.19 % 1.76 % 1.71 % Expected term of options (in years) 6.37 6.74 7.28 Expected volatility is based on the Company’s own historical volatility since its IPO and benchmarked public companies during fiscal years 2017, 2016 and 2015. The risk-free interest rate, ranging from 1.82% to 2.21% during the year ended December 31, 2017, is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected life of the options. The expected term of options represents the weighted-average period of time that options granted are expected to be outstanding based on historical data. The total intrinsic value (the difference between market value and exercise prices of in-the-money options) of all outstanding options at December 31, 2017, 2016, and 2015, was $28,613,000, $12,951,000 and $6,360,000, respectively. The total intrinsic value of exercisable options at December 31, 2017, 2016, and 2015, was $11,469,000, $3,841,000 and $3,586,000, respectively. In 2017, 2016 and 2015, 59,112, 35,207 and 3,147 options were exercised, respectively. As of December 31, 2017, total unrecognized compensation expense of $31,579,000 related to equity awards is expected to be recognized over a weighted average of 3.63 years.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies Lease Commitments The Company leases certain office and laboratory space under a non-cancelable operating lease. On November 9, 2017, the Company amended the lease agreement to extend its lease term by 24 months for an expiration date of October 2020. Rent is expensed on a straight-line basis, and an accrued rent liability of approximately $72,000 and $120,000 is recorded in other accrued liabilities on the accompanying consolidated balance sheets at December 31, 2017 and 2016, respectively. Future minimum lease payments under non-cancelable operating leases are as follows at December 31, 2017 (in thousands): 2018 $ 613 2019 631 2020 538 Thereafter — $ 1,782 For the years ended December 31, 2017, 2016, and 2015, the Company recorded total rent expense of approximately $512,000, $463,000 and $523,000, respectively. Indemnifications ASC 460, Guarantees, As permitted under Delaware law and in accordance with the Company’s bylaws, officers and directors are indemnified for certain events or occurrences, subject to certain limits, while the officer or director is or was serving in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company has obtained director and officer insurance that limits its exposure and may enable recoverability of a portion of any future amounts paid. The Company believes the fair value for these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations as of December 31, 2017. The Company has certain agreements with licensors, licensees, and collaborators that contain indemnification provisions. In such provisions, the Company typically agrees to indemnify the licensor, licensee, and collaborator against certain types of third-party claims. The Company accrues for known indemnification issues when a loss is probable and can be reasonably estimated. There were no accruals for expenses related to indemnification issues for any period presented.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related-Party Transactions	13. Related-Party Transactions The Company paid approximately $0, $306,000, and $806,000, to certain stockholders and primarily academic institutions, for sponsored research in 2017, 2016, and 2015, respectively. These amounts are recorded in research and development expense in the accompanying consolidated statements of operations. On September 23, 2015, the Company’s Board of Directors resolved to forgive a board director’s promissory note principal and accrued interest, totaling $1,056,000, effective October 19, 2015. The value of the 25% recourse portion of the note and related accumulated interest was $264,000. The value of the 75% nonrecourse portion of the note required calculation based on the incremental value of the stock award prior to the forgiveness compared to subsequent to the forgiveness. The fair value of the Company’s stock, as determined by the board of directors, at this time was $25.52, and this value was utilized in calculating the value of the nonrecourse portion of the note which totaled $272,000. The total of $536,000 was charged to stock-based compensation expense as of December 31, 2015.

Net (Loss) Income per Share

Net (Loss) Income per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net (Loss) Income per Share	14. Net (Loss) Income per Share The computation of basic and diluted net (loss) income per share attributable to common stockholders the Company for the years ended December 31 is summarized in the following table: 2017 2016 2015 Numerator Net loss (in thousands) $ (47,671 ) $ (6,227 ) $ (1,450 ) Denominator Weighted-average number of common shares used in net loss per share – basic 23,933,309 19,816,635 15,974,974 Dilutive potential common shares — — — Weighted-average number of common shares used in net loss per share – diluted 23,933,309 19,816,635 15,974,974 Net loss per share – basic (1.99 ) (0.31 ) (0.09 ) Net loss per share – diluted (1.99 ) (0.31 ) (0.09 ) The number of weighted average options that were not included in the diluted earnings per share calculation because the effect would have been anti-dilutive represented 3,251,696, 2,311,146, and 550,675 shares for the years ended 2017, 2016, and 2015, respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data	15. Selected Quarterly Financial Data The following table contains quarterly financial information for 2017 and 2016. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period (in thousands except per share data). 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 12,732 $ 12,806 $ 12,557 $ 9,963 Total expenses 19,906 24,000 24,575 26,489 Total other income (expense) 76 (395 ) (289 ) (148 ) Provision for taxes on income - 2 1 - Net loss (7,098 ) (11,591 ) (12,308 ) (16,674 ) Net loss per share – basic and diluted (0.32 ) (0.52 ) (0.50 ) (0.64 ) 2016 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 12,438 $ 12,366 $ 12,551 $ 12,501 Total expenses 12,701 13,791 13,509 16,737 Total other income 23 28 62 101 (Benefit) provision for taxes on income 18 (461 ) 1 1 Net loss (258 ) (936 ) (897 ) (4,136 ) Net loss per share – basic and diluted (0.02 ) (0.05 ) (0.04 ) (0.19 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events The Company has evaluated events and transactions occurring subsequent to December 31, 2017, but prior to the issuance of the consolidated financial statements, for recognition or disclosure in its consolidated financial statements. During this period, there were no subsequent events requiring either recognition in the consolidated financial statements or nonrecognized subsequent events requiring disclosure.

Summary of Significant Accoun23

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition The Company has license agreements with AbbVie Inc. (AbbVie) (the AbbVie License Agreement) and Kyowa Hakko Kirin Co., Ltd. (KHK) (the KHK Agreement), under which AbbVie and KHK were granted exclusive licenses to develop and commercialize bardoxolone methyl in the Territory (as defined in the KHK Agreement) and the Licensed Territory (as defined in the AbbVie License Agreement). The terms of the agreements include payments to the Company of nonrefundable, up-front license fees; milestone payments; and royalties on product sales. The Company has a collaboration agreement with AbbVie (the AbbVie Collaboration Agreement) that provides for exclusive licenses to collaborate in the research, development, and worldwide commercialization of targeted Nrf2 activators and to participate on respective joint steering committees. The terms of the agreements include a nonrefundable, up-front payment. The Company recognizes revenue of nonrefundable, up-front license fees and other payments when persuasive evidence that an arrangement exists, services have been rendered or delivery has occurred, the price is fixed and determinable, collection is reasonably assured, and there are no further performance obligations under the agreement. The AbbVie License Agreement, the AbbVie Collaboration Agreement, and the KHK Agreement are all multiple-element arrangements. Multiple-element arrangements are analyzed to determine whether the various performance obligations, or elements, can be separated or whether they must be accounted for as a single unit of accounting. For arrangements entered into prior to January 1, 2011, the following criteria were required to be met in order to separate the elements of the arrangement into different units of accounting: 1. The delivered item or items have value to the customer on a stand-alone basis. 2. There is objective and reliable evidence of fair value of the undelivered item or items. 3. If the arrangement includes a general right of return relative to the delivered item, delivery or performance of the undelivered item or items is considered probable and substantially in the control of the vendor. Both the AbbVie License Agreement and the KHK Agreement were executed prior to January 1, 2011, and contained both delivered and undelivered elements in the arrangements. The Company views the key elements of these arrangements as being the exclusive licenses to AbbVie and KHK and participation on joint steering committees. The Company’s involvement in the joint steering committees established under each of these agreements was assessed to determine whether the involvement is an obligation or a right to participate. Based on this assessment, the Company concluded that involvement in the joint steering committees was a substantive deliverable of the arrangement. The Company concluded that objective and reliable evidence of the fair value of the undelivered element of these arrangements (participation on joint steering committees) did not exist; therefore, the Company is accounting for these arrangements as a single unit of accounting. The Company is recognizing revenue associated with the nonrefundable, up-front license fees received under the AbbVie License Agreement and the KHK Agreement ratably over the expected term of the joint steering committee performance obligations, which the Company estimates will be delivered through December 2021 and November 2017 for the KHK Agreement and the AbbVie License Agreement, respectively. The Company continues to participate in regular meetings for the joint steering committee established under the KHK Agreement. At this time, the Company believes its participation in this committee continues to be a substantive performance obligation of the agreements and has concluded that no changes in the estimated revenue recognition periods are warranted. Deferred revenue arises from the excess of cash received over cumulative revenue recognized over the terms of the Company’s continuing obligations. Both the AbbVie License Agreement and the KHK Agreement contain certain clinical development, regulatory, and sales milestones. The Company evaluated each of these milestones at inception of the respective arrangements and concluded that they were substantive milestones, and accordingly, the Company will recognize payments related to the achievement of such milestones, if any, when milestones or net sales levels are achieved and collection is reasonably assured. Factors considered in this determination included scientific and regulatory risks that must be overcome to achieve each milestone, the level of effort and investment required to achieve each milestone, and the monetary value attributed to each milestone. In October 2009, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2009-13, Multiple-Deliverable Revenue Arrangements Revenue Recognition • The License Grants, including various exclusive, co-exclusive, and non-exclusive license grants to AbbVie by the Company related to the Company’s molecules and to jointly discovered new molecules and to the Company by AbbVie related to jointly discovered new molecules; • The Research and Exploratory Development Collaboration, including substantive participation in the Joint Research and Development Incubator Committee established by the agreement; and • The Collaboration Agreement to jointly develop and commercialize second-generation Nrf2 activators, including participation in the Joint Executive Committee, Joint Development Committees, and Joint Marketing Committees established by the agreement. The Company evaluated the deliverables within the AbbVie Collaboration Agreement and concluded that the only delivered element of the arrangement, the License Grants, does not have value to AbbVie on a stand-alone basis. Accordingly, the Company concluded that the various elements of the arrangement cannot be separated into different units of accounting. Therefore, the Company is recognizing revenue associated with the nonrefundable, up-front payment over the estimated 15-year term necessary to execute the joint research, development, and commercialization terms under the agreement. The Company follows ASC 605-28, Revenue Recognition—Milestone Method In June 2013, the Company entered into a research collaboration with a disease advocacy organization. Under the agreement, the Company may be provided milestone payments to fund research and development activities estimated over a two-year period. The Company recorded collaboration revenue totaling $500,000, $0 and $700,000 related to milestone payments during the years ended December 31, 2017, 2016, and 2015, respectively.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all investments in highly liquid financial instruments with a maturity of three months or less when purchased to be cash equivalents. Investments qualifying as cash equivalents primarily consist of money market funds. The carrying amount of cash equivalents approximates fair value. Investment income consists primarily of interest income on our cash and cash equivalents, which include money market funds.
Research and Development Costs	Research and Development Costs All research and development costs are expensed as incurred, including costs for drug supplies used in research and development or clinical studies, property and equipment acquired specifically for a finite research and development project, and nonrefundable deposits incurred at the initiation of research and development activities. Research and development costs consist principally of costs related to clinical studies managed directly by the Company and through contract research organizations, manufacture of clinical drug products for clinical studies, preclinical study costs, discovery research expenses, facilities costs, salaries, and related expenses. AbbVie is not currently participating in the development of bardoxolone methyl for the treatment of CKD caused by Alport syndrome, CTD-PAH, PH-ILD, or other rare kidney diseases, and the Company is therefore incurring all costs for this program. AbbVie has the right to opt-in to these programs at any time during development. Upon opting-in, AbbVie would be required to pay an agreed upon amount of all development costs accumulated up to the point of exercising their opt-in right. All development costs incurred after AbbVie’s opt-in would be split equally. With respect to its omaveloxolone programs and its collaboration agreement with AbbVie, the Company was responsible for a certain initial amount in early development costs before AbbVie began sharing development costs equally. As of April 2016, the Company had incurred all of these initial costs, after which payments from AbbVie with respect to research and development costs incurred by the Company were recorded as a reduction in research and development expenses. The Company’s expenses were reduced $1,434,000 for AbbVie’s share of research and development costs for the twelve months ended December 31, 2016. In September 2016, the Company and AbbVie mutually agreed that the Company would continue unilateral development of omaveloxolone. Therefore, AbbVie no longer co-funds the exploratory development costs of this program, but retains the right to opt back in at certain points in development. Depending upon what point, if any, In December 2017, the Company and KHK entered into the Third Supplement to the KHK Agreement, which allows the Company to begin a portion of the CARDINAL registrational trial in Japan, for which KHK will reimburse costs incurred up to $3,000,000. The Company deemed that this was not a material modification to the KHK Agreement because no payment terms or deliverables were changed. The Company’s expenses were reduced by $515,000 for KHK’s share of the study costs for twelve months ended December 31, 2017. The Company bases its expense accruals related to clinical trials on its estimates of the services received and efforts expended pursuant to contracts with multiple research institutions and contract research organizations that conduct and manage clinical trials on its behalf. The financial terms of these agreements vary from contract to contract and may result in uneven payment flows. Payments under some of these contracts depend on factors such as the successful enrollment of patients and the completion of clinical trial milestones. In accruing costs, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the Company does not identify costs that it has begun to incur or if the Company underestimates or overestimates the level of services performed or the costs of these services, its actual expenses could differ from its estimates. To date, the Company has not experienced significant changes in its estimates of accrued research and development expenses after a reporting period. However, due to the nature of estimates, the Company cannot assure that it will not make changes to its estimates in the future as the Company becomes aware of additional information about the status or conduct of its clinical trials and other research activities.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the following estimated useful lives: Computer equipment 2–5 years Software 3 years Laboratory equipment 5–7 years Office furniture 5 years Office equipment 5 years Leasehold improvements are amortized on the straight-line method over the shorter of the lease term or the estimated useful life of the equipment or improvement. Such amortization is included in depreciation and amortization expense in the consolidated statements of operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company periodically evaluates its long-lived assets for potential impairment in accordance with ASC Topic 360, Property, Plant and Equipment
Licenses and Patents	Licenses and Patents License and sublicense costs are expensed as incurred and are classified as research and development expenses. Costs associated with filing, prosecuting, enforcing, and maintaining patent rights are expensed as incurred and are classified as general and administrative expenses.
Income Taxes	Income Taxes The Company accounts for income taxes and the related accounts under the liability method. Deferred tax assets and liabilities are determined based on differences between the financial statement and tax bases of assets and liabilities, and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The measurement of a deferred tax asset is reduced, if necessary, by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes
Stock-Based Compensation	Stock-Based Compensation The Company accounts for its stock-based compensation in accordance with ASC 718 Compensation—Stock Compensation • Expected term—The expected term represents the period that the stock-based awards are expected to be outstanding and is based on the average period the stock options are expected to be outstanding and was based on our historical information of the options exercise patterns and post-vesting termination behavior. • Expected volatility—Since the Company does not have sufficient trading history to estimate the volatility of its common stock, the expected volatility was estimated based on its own historical volatility since its IPO and the average volatility for comparable publicly traded biopharmaceutical companies. When selecting comparable publicly traded biopharmaceutical companies on which the Company based its expected stock price volatility, the Company selected companies with comparable characteristics to the Company, including enterprise value, risk profiles, position within the industry, and historical share price information sufficient to meet the expected life of the stock-based awards. • Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option. • Expected dividend—The Company has no plans to pay dividends on its common stock. Therefore, the company used an expected dividend yield of zero. In addition to the assumptions used in the Black-Scholes option-pricing model, the Company will continue to use judgment in evaluating the expected volatility, and expected terms utilized for its stock-based compensation calculations on a prospective basis. The Company accounts for forfeitures of share-based awards when they occur. Options to purchase shares of the Company’s common stock, and restricted common stock with certain repurchase rights, have been granted or sold to nonemployees at fair value, in connection with research and consulting services provided to the Company, and to employees at fair value, in connection with Stock Purchase and Restriction Agreements. Equity awards generally vest over terms of four or five years. For awards to employees, stock-based compensation expense is recorded ratably through the vesting period for each option award or tranche of restricted stock.
Risks and Uncertainties	Risks and Uncertainties The Company has experienced losses and negative operating cash flows for many years since inception and has no marketed drug or other products. The Company’s ability to generate future revenue depends upon the results of its development programs, whose success cannot be guaranteed. The Company may need to raise additional equity capital in the future in order to fund its operations.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting, and filing fees relate to the follow-on offering and IPO, are capitalized. Deferred offering costs totaling $404,000 and $3,471,000 were offset against proceeds from the follow-on offering and IPO, respectively. The Company had $0 in capitalized deferred offering costs as of December 31, 2017 and 2016. Debt Issuance Costs The Company defers costs related to debt issuance and amortizes these costs to interest expense over the term of the debt, using the effective interest method. Debt issuance costs are presented in the balance sheet as a deduction from the carrying amount of the debt liability.
Net Income (Loss) per Share	Net Income (Loss) per Share Basic and diluted net income (loss) per common share is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include unvested restricted stock, and options to purchase common stock, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. For periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Assets and liabilities that are carried at fair value are to be classified and disclosed in one of the following three categories: Level 1: Observable quoted market prices in active markets for identical assets or liabilities; Level 2: Observable inputs other than Level 1, such as quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability; and. Level 3: Unobservable inputs for the asset or liability that are significant to the fair value of the assets or liabilities. At December 31, 2017 and 2016, the Company had no assets or liabilities that are required to be carried at fair value. The book values of the Company’s cash and cash equivalents and other working capital financial assets and liabilities approximate their fair values due to their short term nature. The fair values of the Company’s shareholder notes receivable were immaterial.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances from non-owner sources and includes all components of net income (loss) and other comprehensive income (loss). The other comprehensive income (loss) for the years ended December 31, 2017, 2016, and 2015 were immaterial.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act of 2012 (the JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue Recognition The new standard is effective for interim and annual periods beginning after December 15, 2017, with early application for interim and annual periods beginning after December 15, 2016, permitted, and allows two methods of adoption: the full retrospective method, which requires the standard to be applied to each prior period presented, or the modified retrospective method, which requires the cumulative effect of adoption to be recognized as an adjustment to opening retained earnings in the period of adoption. The Company is finalizing its assessment of the impact of this guidance on its consolidated results of operations and financial position and disclosures. The Company will apply the modified retrospective method upon adoption of this standard effective January 1, 2018 and expects to recognize a decrease of approximately $2,634,000 to retained earnings. In February 2016, the FASB issued ASU No. 2016-02, Leases Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments In January 2017, the FASB issued ASU No. 2017-03, Accounting Changes and Error Corrections and Investments—Equity Method and Joint Ventures Revenue from Contracts with Customers Leases Financial Instruments—Credit Losses Measurement of Credit Losses on Financial Instruments In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Depreciation Property and Equipment	Depreciation is computed using the straight-line method over the following estimated useful lives: Computer equipment 2–5 years Software 3 years Laboratory equipment 5–7 years Office furniture 5 years Office equipment 5 years

Term Loan (Tables)

Term Loan (Tables)	12 Months Ended
	Dec. 31, 2017
Term Loan A
Schedule of Future Principal Payments for Term A Loan	The future principal payments for the Company’s Term A Loan as of December 31, 2017 are as follows (in thousands): 2018 $ 975 2019 $ 5,854 2020 $ 5,854 2021 $ 5,854 2022 $ 1,463 $ 20,000

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment consisted of the following as of December 31(in thousands): 2017 2016 Computer equipment and software $ 1,831 $ 2,928 Laboratory equipment 4,654 4,530 Office furniture 1,282 1,273 Office and other equipment 286 273 Leasehold improvements 4,959 4,976 13,012 13,980 Less accumulated depreciation and amortization (12,294 ) (13,161 ) Property and equipment, net $ 718 $ 819

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Summary of Provision for Taxes on Income	The provision for taxes on income consists of the following at December 31 (in thousands): 2017 2016 2015 Current $ 3 $ (441 ) $ (16,654 ) Deferred — — 17,802 Total provision for taxes on income $ 3 $ (441 ) $ 1,148
Reconciliation of Effective Income Tax Rate from Continuing Operations to Federal statutory Tax Rate of 35%	The following table reconciles the Company’s effective income tax rate from continuing operations to the federal statutory tax rate of 35%: 2017 2016 2015 U.S. federal income taxes 35 % 35 % 35 % Stock-based compensation — (2 ) (80 ) Change in valuation allowance 48 (25 ) (310 ) 2017 Tax Act (111 ) — — Federal tax credits 28 — — Other — (1 ) (25 ) Recorded federal income tax benefit (provision) 0 % 7 % (380 )%
Significant Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets as of December 31 are as follows (in thousands): 2017 2016 Deferred tax assets: Deferred revenue $ 51,332 $ 101,864 Net operating loss 25,601 19,159 Federal tax credits 20,928 — Stock-based compensation 2,118 1,362 Depreciation 318 608 Other 301 392 Subtotal 100,598 123,385 Less: Valuation allowance (100,598 ) (123,385 ) Net deferred tax asset $ — $ —

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock Reserved For Issuance	At December 31, 2017, common stock reserved for issuance is as follows: Outstanding common stock options under the 2007 Long Term Incentive Plan 3,220,350 Outstanding common stock options under standalone option agreements 31,346 Common stock available for future grant under the 2007 Long Term Incentive Plan 107,322 Total common shares reserved for future issuance 3,359,018

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Based Compensation Expense	The following table summarizes stock-based compensation expense reflected in the consolidated statements of operations (in thousands): Years Ended December 31 2017 2016 2015 Research and development $ 2,409 $ 1,121 $ 671 General and administrative 4,121 1,246 1,404 $ 6,530 $ 2,367 $ 2,075
Summary of Stock Option Activity	The following table summarizes stock option activity as of December 31, 2017, and changes during the years ended December 31, 2017 under the 2007 LTIP and standalone option agreements: Number of Options Weighted- Average Exercise Price Outstanding at January 1, 2017 2,311,146 17.18 Granted 1,044,848 25.00 Exercised (59,112 ) 11.14 Forfeited (45,120 ) 14.68 Expired (66 ) 25.21 Outstanding at December 31, 2017 3,251,696 19.83 Exercisable at December 31, 2017 939,137 17.12
Weighted Average Assumptions in Black-Scholes Pricing Model	The weighted-average assumptions used in the Black-Scholes option pricing model were as follows: Years Ended December 31 2017 2016 2015 Dividend yield — % — % — % Volatility 75.14 % 72.77 % 74.93 % Risk-free interest rate 2.19 % 1.76 % 1.71 % Expected term of options (in years) 6.37 6.74 7.28

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Under Non Cancelable Operating Leases	Future minimum lease payments under non-cancelable operating leases are as follows at December 31, 2017 (in thousands): 2018 $ 613 2019 631 2020 538 Thereafter — $ 1,782

Net (Loss) Income per Share (Ta

Net (Loss) Income per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net (Loss) Income per Share	The computation of basic and diluted net (loss) income per share attributable to common stockholders the Company for the years ended December 31 is summarized in the following table: 2017 2016 2015 Numerator Net loss (in thousands) $ (47,671 ) $ (6,227 ) $ (1,450 ) Denominator Weighted-average number of common shares used in net loss per share – basic 23,933,309 19,816,635 15,974,974 Dilutive potential common shares — — — Weighted-average number of common shares used in net loss per share – diluted 23,933,309 19,816,635 15,974,974 Net loss per share – basic (1.99 ) (0.31 ) (0.09 ) Net loss per share – diluted (1.99 ) (0.31 ) (0.09 )

Selected Quarterly Financial 32

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data	The following table contains quarterly financial information for 2017 and 2016. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period (in thousands except per share data). 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 12,732 $ 12,806 $ 12,557 $ 9,963 Total expenses 19,906 24,000 24,575 26,489 Total other income (expense) 76 (395 ) (289 ) (148 ) Provision for taxes on income - 2 1 - Net loss (7,098 ) (11,591 ) (12,308 ) (16,674 ) Net loss per share – basic and diluted (0.32 ) (0.52 ) (0.50 ) (0.64 ) 2016 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 12,438 $ 12,366 $ 12,551 $ 12,501 Total expenses 12,701 13,791 13,509 16,737 Total other income 23 28 62 101 (Benefit) provision for taxes on income 18 (461 ) 1 1 Net loss (258 ) (936 ) (897 ) (4,136 ) Net loss per share – basic and diluted (0.02 ) (0.05 ) (0.04 ) (0.19 )

Description of Business - Addit

Description of Business - Additional Information (Details)	Nov. 09, 2017USD ($)shares	Aug. 01, 2017USD ($)shares	May 25, 2016USD ($)$ / sharesshares	Dec. 31, 2017USD ($)Patientshares	Dec. 31, 2016USD ($)shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from issuance of common stock from initial public offering | $			$ 60,900,000	$ 108,910,000	$ 64,705,000
Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock				3,737,500
IPO
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance price (in dollars per share) | $ / shares			$ 11
IPO | Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock			6,325,000		6,325,000
Over-Allotment Option | Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock			825,000
Over-Allotment Option | Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock		487,500
Gross proceeds from issuance of common stock from over-allotment option granted to the underwriters | $		$ 115,900,000
Total proceeds from issuance of common stock from follow-on underwritten public offering | $		$ 108,500,000
Follow-on Underwritten Public Offering | Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock		3,737,500
At-the-Market Equity Offering Sales Agreement | Common Stock A
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock	0
Maximum common stock value that may be offered and sold | $	$ 50,000,000
C A R D I N A L
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of patients to be enrolled in study | Patient				150
CATALYST | Minimum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of patients to be enrolled in study | Patient				130
CATALYST | Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of patients to be enrolled in study | Patient				200

Summary of Significant Accoun34

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Jan. 01, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Up-front payment estimated term									15 years
Milestone payment period									2 years
Collaboration revenue									$ 500,000	$ 0	$ 700,000
Reduction in research and development expense										1,434,000
Reimbursement of costs incurred									955,000	126,000	24,000
Asset impairment charges									0	0	0
Deferred offering costs		$ 404,000			$ 3,471,000				404,000	3,471,000
Capitalized deferred offering costs		0			0				0	0
Assets, fair value		0			0				0	0
Liabilities, fair value		0			0				0	0
Provision (benefit) for taxes on income			$ 1,000	$ 2,000	$ 1,000	$ 1,000	$ (461,000)	$ 18,000	3,000	$ (441,000)	$ 1,148,000
Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Expected recognition of decrease to retained earnings		(2,634,000)							$ (2,634,000)
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Cumulative effect of change adjustment to retained earnings	$ 118,000
Provision (benefit) for taxes on income	$ (115,000)
Maximum
Significant Accounting Policies [Line Items]
Equity vesting terms									5 years
Minimum
Significant Accounting Policies [Line Items]
Equity vesting terms									4 years
KHK Agreement | License Agreement Terms | Clinical Development Milestones
Significant Accounting Policies [Line Items]
Collaboration revenue									$ 10,000,000
Reduction in research and development expense									$ 515,000
KHK Agreement | License Agreement Terms | Clinical Development Milestones | Maximum
Significant Accounting Policies [Line Items]
Reimbursement of costs incurred		$ 3,000,000

Summary of Estimated Useful Liv

Summary of Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Computer equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Computer equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Laboratory equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Laboratory equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Office furniture
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details)	1 Months Ended			12 Months Ended
	Dec. 31, 2011USD ($)	Sep. 30, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2017USD ($)Milestone	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, current				$ 28,183,000	$ 46,603,000
Collaboration revenue, milestone payments received				500,000	0	$ 700,000
AbbVie | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue recognized				18,420,000	21,470,000	21,412,000
Deferred revenue				0	18,420,000
Deferred revenue, current				0	18,420,000
AbbVie | Up-front Payment Arrangement | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received		$ 150,000,000
AbbVie | Clinical Development Milestones | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue, milestone payments received				150,000,000
AbbVie | Commercial Milestones | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue, potential milestone payments				50,000,000
AbbVie | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue recognized				26,647,000	26,720,000	26,647,000
Deferred revenue				238,292,000	264,939,000
Deferred revenue, current				26,647,000	26,647,000
AbbVie | Collaborative Arrangement | Up-front Payment Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front collaboration payment received	$ 400,000,000
KHK Agreement | Accounting Standards Update 2014-09
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue expected to be recognized as of December 31, 2018				$ 30,000,000
Revenue, Performance Obligation, Description of Timing				Under ASU 2014-09, variable consideration must be included in the transaction price when it is determined that it is probable that a significant reversal in the revenue recognized will not occur. We expect to recognize $30,000,000 in deferred revenue related to a milestone from KHK during 2018, which we will ratably recognize in revenue over our estimated performance obligation period ending December 2021.
KHK Agreement | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue recognized				$ 1,536,000	1,540,000	$ 1,536,000
Deferred revenue				6,146,000	7,682,000
Deferred revenue, current				1,536,000	$ 1,536,000
KHK Agreement | Up-front Payment Arrangement | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received			$ 35,000,000
KHK Agreement | Clinical Development Milestones | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue, milestone payments received				10,000,000
KHK Agreement | Commercial Milestones | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue, potential milestone payments				$ 140,000,000
Number of non-substantive milestones | Milestone				4
KHK Agreement | Regulatory Development Milestone | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue, milestone payments received				$ 5,000,000
Collaboration revenue, potential milestone payments				$ 82,000,000
Number of non-substantive milestones | Milestone				8

Term Loan - Additional Informat

Term Loan - Additional Information (Details)	Nov. 09, 2017USD ($)	Nov. 08, 2017USD ($)	Nov. 03, 2017USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2017USD ($)TermLoan	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Proceeds from long-term debt						$ 20,000,000
Term Loan A
Debt Instrument [Line Items]
Debt instrument, carrying value						$ 20,000,000
Loan And Security Agreement
Debt Instrument [Line Items]
Number of term loans | TermLoan					2
Debt instrument, prepayment terms						The Company has the option to prepay all, but not less than all, of the borrowed amounts, provided that the Company will be obligated to pay a prepayment fee equal to (a) 3.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made prior to the first anniversary of the applicable funding date of the Term Loan, (b) 2.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made by the second anniversary of the applicable funding date of the Term Loan, or (c) 1.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the second anniversary of the applicable funding date of the Term Loan.
Debt instrument final exit fee payment percentage						2.95%
Loan And Security Agreement | Loan Prepayment Prior To First Anniversary [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						3.00%
Loan And Security Agreement | Loan Prepayment By Second Anniversary [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						2.00%
Loan And Security Agreement | Loan Prepayment After Second Anniversary [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						1.00%
Loan And Security Agreement | Term Loans
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 35,000,000	$ 35,000,000
Debt instrument, payment terms						All outstanding Term Loans will mature on March 1, 2022. Under the Term A Loan, the Company will make interest-only payments for 18 months through October 1, 2018; however, if the Company draws the Term B Loan, the Company will make interest-only payments for 30 months through October 1, 2019. The interest-only payment period will be followed by 41 equal monthly payments, or 29 equal monthly payments if the Company draws the Term B Loan, of principal and interest payments.
Debt instrument, maturity date						Mar. 1, 2022
Debt instrument, interest rate terms						The Term Loans will bear interest at a floating per annum rate calculated as 7.40% plus the greater of the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue or 0.75%, with a minimum rate of 8.15% and maximum rate of 10.15%.
Debt instrument, annual interest rate						7.40%
Debt instrument, basis spread on variable rate						0.75%
Loan And Security Agreement | Term Loans | Minimum
Debt Instrument [Line Items]
Debt instrument, annual interest rate						8.15%
Loan And Security Agreement | Term Loans | Maximum
Debt Instrument [Line Items]
Debt instrument, annual interest rate						10.15%
Loan And Security Agreement | Term Loan A
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 20,000,000
Proceeds from long-term debt				20,000,000
Debt instrument, interest only payments period						18 months through October 1, 2018
Debt instrument, carrying value						$ 20,000,000
Debt instrument, debt issuance costs						$ 524,000
Debt instrument, effective interest rate						11.10%
Debt instrument, final exit fee accrued						$ 590,000
Loan And Security Agreement | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 15,000,000	$ 15,000,000
Debt instrument, interest only payments period						30 months through October 1, 2019
Amended Loan Agreement | Term Loan B
Debt Instrument [Line Items]
Debt instrument, interest only period			6 months
Period to borrow funds after achievement of milestone	90 days
Debt instrument, possible borrowing date	Jun. 29, 2018
Payment of amendment fee		$ 250,000
Payment of unused line fee	$ 1,000,000
Amended Loan Agreement | Term Loan B | Sole Discretion
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 20,000,000
Amended Loan Agreement | Term Loan B | Achievement of One of Two Milestones
Debt Instrument [Line Items]
Maximum borrowing capacity			25,000,000
Amended Loan Agreement | Term Loan B | Scenario Two
Debt Instrument [Line Items]
Additional borrowing capacity			$ 5,000,000
Amended Loan Agreement | Term Loan B | If Term B Loan is Drawn
Debt Instrument [Line Items]
Debt instrument, interest only period			12 months

Term Loan - Schedule of Future

Term Loan - Schedule of Future Principal Payments for Term A Loan (Details) - Term Loan A $ in Thousands	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
2,018	$ 975
2,019	5,854
2,020	5,854
2,021	5,854
2,022	1,463
Long-term Debt	$ 20,000

Summary of Property and Equipme

Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	$ 13,012	$ 13,980
Less accumulated depreciation and amortization	(12,294)	(13,161)
Property and equipment, net	718	819
Computer equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	1,831	2,928
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	4,654	4,530
Office furniture
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	1,282	1,273
Office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	286	273
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	$ 4,959	$ 4,976

Summary of Provision for Taxes

Summary of Provision for Taxes on Income (Details) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current							$ 3	$ (441)	$ (16,654)
Deferred									17,802
Total provision for taxes on income	$ 1	$ 2	$ 1	$ 1	$ (461)	$ 18	$ 3	$ (441)	$ 1,148

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Federal statutory tax rate		35.00%	35.00%	35.00%
Estimated reduction in deferred tax assets		$ 53,113,000
(Decrease) Increase in valuation allowance		(22,788,000)	$ 1,685,000
Accumulated net operating losses		121,911,000
Accumulated net operating losses, annual limitation		315,000
Federal research and development tax credit carryforwards		123,000
Federal orphan drug tax credit carryforwards		20,805,000
Unrecognized tax benefits, if recognized, would impact effective tax rate		0
Between Fiscal Year 2023 and 2024
Income Tax Disclosure [Line Items]
Accumulated net operating losses		434,000
Fiscal Year 2037
Income Tax Disclosure [Line Items]
Accumulated net operating losses		$ 121,477,000
Tax Year 2009 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Income tax examination year, audit by IRS completed		2,009
Tax Year 2011 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Income tax examination year, audit by IRS completed		2,011
Tax Year 2012 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Income tax examination year, audit by IRS completed		2,012
Tax Year 2013 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Examination of U.S. income tax returns, year		2,013
Tax Year 2014 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Examination of U.S. income tax returns, year		2,014
Tax Year 2015 | Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Examination of U.S. income tax returns, year		2,015
Scenario Forecast
Income Tax Disclosure [Line Items]
Federal statutory tax rate	21.00%

Reconciliation of Effective Inc

Reconciliation of Effective Income Tax Rate from Continuing Operations to Federal statutory Tax Rate of 35% (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. federal income taxes	35.00%	35.00%	35.00%
Stock-based compensation		(2.00%)	(80.00%)
Change in valuation allowance	48.00%	(25.00%)	(310.00%)
2017 Tax Act	(111.00%)
Federal tax credits	28.00%
Other		(1.00%)	(25.00%)
Recorded federal income tax benefit (provision)	(0.00%)	7.00%	(380.00%)

Significant Components of Net D

Significant Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Deferred revenue	$ 51,332	$ 101,864
Net operating loss	25,601	19,159
Federal tax credits	20,928
Stock-based compensation	2,118	1,362
Depreciation	318	608
Other	301	392
Subtotal	100,598	123,385
Less: Valuation allowance	$ (100,598)	$ (123,385)

Patents (Details)

Patents (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingency [Abstract]
Patent matters outstanding	0	0	0

Licenses- Additional Informatio

Licenses- Additional Information (Details)	12 Months Ended
	Dec. 31, 2017
License Agreements [Line Items]
Term of agreements	The term of all agreements is through the useful lives of the licensed patents or for a period of 15 to 20 years for technology rights, for which there are no applicable patent rights.
Minimum
License Agreements [Line Items]
Term of agreements	15 years
Maximum
License Agreements [Line Items]
Term of agreements	20 years

Common Stock (Details)

Common Stock (Details)	Dec. 31, 2017shares
Common shares reserved for future issuance	3,359,018
Outstanding common stock options under the 2007 Long Term Incentive Plan
Common shares reserved for future issuance	3,220,350
Outstanding common stock options under standalone option agreements
Common shares reserved for future issuance	31,346
Common stock available for future grant under the 2007 Long Term Incentive Plan
Common shares reserved for future issuance	107,322

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - shares	Dec. 31, 2017	Dec. 31, 2016	Jan. 04, 2016
Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Undesignated Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock			100,000,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Common Stock Reserved for Issuance	3,359,018
Options to purchase shares outstanding	3,251,696	2,311,146
Stock options , vested or expected to vest	3,251,696
Stock Option, Weighted-average exercise price	$ 19.83
Exercisable Stock, Weighted-average outstanding	7 years 29 days
Risk free interest rate, Minimum	1.82%
Risk free interest rate, Maximum	2.21%
Total intrinsic value of outstanding options	$ 28,613,000	$ 12,951,000	$ 6,360,000
Total intrinsic value of exercisable options	$ 11,469,000	$ 3,841,000	$ 3,586,000
Exercise of options, shares	59,112	35,207	3,147
Unrecognized compensation expense	$ 31,579,000
Unrecognized compensation expense, recognition period	3 years 7 months 17 days
Minimum
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity vesting terms	4 years
Maximum
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity vesting terms	5 years
Restricted Stock
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares of restricted stock outstanding	0	0
Fair value of vested restricted stock	$ 0	$ 356,000
Stock Options
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted-average years, vested and expected to vest	8 years 6 months 21 days
2007 LTIP
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Common Stock Reserved for Issuance	107,322
Stock options grant expirations periods	10 years
2007 LTIP | Minimum
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity vesting terms	4 years
2007 LTIP | Maximum
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity vesting terms	5 years
2007 LTIP | Restricted Stock
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares of restricted stock outstanding	0
Shares of restricted stock issued to date	1,193,780	1,193,780
2002 Plan | Restricted Stock
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares of restricted stock issued to date	1,193,780	1,193,780

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$ 6,530	$ 2,367	$ 2,075
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	2,409	1,121	671
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$ 4,121	$ 1,246	$ 1,404

Stock-Based Compensation - Su50

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options, Abstract
Number of Options, Outstanding - Beginning balance	2,311,146
Number of Options, Granted	1,044,848
Number of Options, Exercised	(59,112)	(35,207)	(3,147)
Number of Options, Forfeited	(45,120)
Number of Options, Expired	(66)
Number of Options, Outstanding - Ending balance	3,251,696	2,311,146
Number of Options, Exercisable	939,137
Weighted Average Exercise Price, Abstract
Weighted-Average Exercise Price, Outstanding - Beginning balance	$ 17.18
Weighted-Average Exercise Price, Granted	25
Weighted-Average Exercise Price, Exercised	11.14
Weighted-Average Exercise Price, Forfeited	14.68
Weighted-Average Exercise Price, Expired	25.21
Weighted-Average Exercise Price, Outstanding - Ending balance	19.83	$ 17.18
Weighted-Average Exercise Price, Exercisable	$ 17.12

Weighted Average Assumption in

Weighted Average Assumption in Black-Scholes Pricing Model (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Dividend yield	0.00%	0.00%	0.00%
Volatility	75.14%	72.77%	74.93%
Risk-free interest rate	2.19%	1.76%	1.71%
Expected term of options (in years)	6 years 4 months 13 days	6 years 8 months 26 days	7 years 3 months 10 days

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Details) - USD ($)	Nov. 09, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Other accrued liabilities		$ 72,000	$ 120,000
Rent expense		$ 512,000	$ 463,000	$ 523,000
Lease Agreement | Executive Offices
Loss Contingencies [Line Items]
Extension of lease term	24 months
Lease expiration date	2020-10

Commitment and Contingencies 53

Commitment and Contingencies - Future Minimum Lease Payments Under Non Cancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,018	$ 613
2,019	631
2,020	538
Thereafter	0
Operating Leases, Future Minimum Payments Due, Total	$ 1,782

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 19, 2015
Related Party Transaction [Line Items]
Stock-based compensation expense	$ 6,530,000	$ 2,367,000	$ 2,075,000
Promissory Note | Director
Related Party Transaction [Line Items]
Notes receivable forgiven				$ 1,056,000
Recourse portion of note, percentage				25.00%
Recourse portion of promissory note and related accumulated interest				$ 264,000
Non-recourse portion of note, percentage				75.00%
Fair value of stock				$ 25.52
Nonrecourse portion of promissory note and related accumulated interest				$ 272,000
Stock-based compensation expense			536,000
Research and development
Related Party Transaction [Line Items]
Stock-based compensation expense	2,409,000	1,121,000	671,000
Stockholders | Research and development
Related Party Transaction [Line Items]
Payments made to stockholders	$ 0	$ 306,000	$ 806,000

Net (Loss) Income per Share - C

Net (Loss) Income per Share - Computation of Basic and Diluted Net (Loss) Income per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Net loss	$ (16,674)	$ (12,308)	$ (11,591)	$ (7,098)	$ (4,136)	$ (897)	$ (936)	$ (258)	$ (47,671)	$ (6,227)	$ (1,450)
Denominator
Weighted-average number of common shares used in net loss per share – basic									23,933,309	19,816,635	15,974,974
Weighted-average number of common shares used in net loss per share – diluted									23,933,309	19,816,635	15,974,974
Net loss per share – basic									$ (1.99)	$ (0.31)	$ (0.09)
Net loss per share – diluted									$ (1.99)	$ (0.31)	$ (0.09)

Net (Loss) Income per Share - A

Net (Loss) Income per Share - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Weighted average anti-dilutive shares excludes from computation of earnings per share	3,251,696	2,311,146	550,675

Selected Quarterly Financial 57

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Total collaboration revenue	$ 9,963	$ 12,557	$ 12,806	$ 12,732	$ 12,501	$ 12,551	$ 12,366	$ 12,438	$ 48,058	$ 49,856	$ 50,319
Total expenses	26,489	24,575	24,000	19,906	16,737	13,509	13,791	12,701	94,970	56,738	50,653
Total other income (expense)	(148)	(289)	(395)	76	101	62	28	23	(756)	214	32
Provision (benefit) for taxes on income		1	2		1	1	(461)	18	3	(441)	1,148
Net loss	$ (16,674)	$ (12,308)	$ (11,591)	$ (7,098)	$ (4,136)	$ (897)	$ (936)	$ (258)	$ (47,671)	$ (6,227)	$ (1,450)
Net loss per share—basic and diluted	$ (0.64)	$ (0.50)	$ (0.52)	$ (0.32)	$ (0.19)	$ (0.04)	$ (0.05)	$ (0.02)	$ (1.99)	$ (0.31)	$ (0.09)