Reata Pharmaceuticals (RETA) 10-K 19 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 13, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	RETA
Entity Registrant Name	Reata Pharmaceuticals, Inc.
Entity Central Index Key	0001358762
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,955,969,284
Title of 12(b) Security	Class A Common Stock, Par Value $0.001 Per Share
Security Exchange Name	NASDAQ
Entity File Number	001-37785
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	11-3651945
Entity Address, Address Line One	5320 Legacy Drive
Entity Address, City or Town	Plano
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75024
City Area Code	972
Local Phone Number	865-2219
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the Registrant’s Definitive Proxy Statement relating to the Annual Meeting of Stockholders, scheduled to be held on June 10, 2020, are incorporated by reference into Part III of this Report.
Common Stock A
Document Information [Line Items]
Entity Common Stock Shares Outstanding		27,911,518
Common Stock B
Document Information [Line Items]
Entity Common Stock Shares Outstanding		5,317,695

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 664,324	$ 337,790
Prepaid expenses and other current assets	4,952	4,483
Total current assets	669,276	342,273
Property and equipment, net	2,996	1,445
Other assets	10,148	1,490
Total assets	682,420	345,208
Liabilities and stockholders’ equity (deficit)
Accounts payable	1,908	4,473
Accrued direct research liabilities	23,774	15,416
Other current liabilities	11,631	4,696
Current portion of payable to collaborators	150,000
Current portion of deferred revenue	4,701	31,335
Total current liabilities	192,014	55,920
Other long-term liabilities	6,982	524
Term loan, net of current portion and debt issuance costs	155,017	79,219
Payable to collaborators, net of current portion	66,862
Deferred revenue, net of current portion	4,688	194,386
Total noncurrent liabilities	233,549	274,129
Commitments and contingencies
Stockholders’ equity (deficit):
Additional paid-in capital	967,317	435,452
Accumulated deficit	(710,493)	(420,323)
Total stockholders’ equity	256,857	15,159
Total liabilities and stockholders’ equity	682,420	345,208
Common Stock A
Stockholders’ equity (deficit):
Common stock value	28	24
Total stockholders’ equity	28	24
Common Stock B
Stockholders’ equity (deficit):
Common stock value	5	6
Total stockholders’ equity	$ 5	$ 6

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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	27,878,550	24,000,683
Common stock, shares outstanding	27,878,550	24,000,683
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	5,318,157	5,728,175
Common stock, shares outstanding	5,318,157	5,728,175

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaboration revenue
Collaboration revenue	$ 26,517	$ 53,589	$ 48,058
Expenses
Research and development	128,109	97,288	71,273
Reacquired license rights	124,398
General and administrative	58,298	32,748	23,260
Depreciation	932	431	437
Total expenses	311,737	130,467	94,970
Other income (expense), net	(4,942)	(3,642)	(756)
Loss before taxes on income	(290,162)	(80,520)	(47,668)
Provision for taxes on income	8	26	3
Net loss	$ (290,170)	$ (80,546)	$ (47,671)
Net loss per share—basic and diluted	$ (9.54)	$ (2.91)	$ (1.99)
Weighted-average number of common shares used in net loss per share basic and diluted	30,414,203	27,701,783	23,933,309
License and milestone
Collaboration revenue
Collaboration revenue	$ 25,276	$ 52,351	$ 47,103
Other revenue
Collaboration revenue
Collaboration revenue	$ 1,241	$ 1,238	$ 955

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock A	Common Stock B	Additional Paid-In Capital	Shareholder Notes Receivable	Total Accumulated Deficit
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 options	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
Compensation expense related to stock options	10,550			10,550
Exercise of options, value	$ 1,885			1,885
Exercise of options, shares	137,352		137,352
Proceeds from payments of shareholder promissory notes	$ 8			6	$ 2
Public offering of common stock, net of offering costs, value	232,869	$ 3		232,866
Public offering of common stock, net of offering costs, shares		3,450,000
Conversion of common stock Class B to Class A, value		$ 1	$ (1)
Conversion of common stock Class B to Class A, shares		575,343	(575,343)
Adoption of new accounting guidance	(2,634)					(2,634)
Net loss	(80,546)					(80,546)
Balance, value at Dec. 31, 2018	15,159	$ 24	$ 6	435,452		(420,323)
Balance, shares at Dec. 31, 2018		24,000,683	5,728,175
Compensation expense related to stock options	26,381			26,381
Exercise of options, value	$ 13,445			13,445
Exercise of options, shares	707,849		707,849
Public offering of common stock, net of offering costs, value	$ 491,935	$ 3		491,932
Public offering of common stock, net of offering costs, shares		2,760,000
Conversion of common stock Class B to Class A, value		$ 1	$ (1)
Conversion of common stock Class B to Class A, shares		1,117,867	(1,117,867)
Other shareholder transactions	107			107
Net loss	(290,170)					(290,170)
Balance, value at Dec. 31, 2019	$ 256,857	$ 28	$ 5	$ 967,317		$ (710,493)
Balance, shares at Dec. 31, 2019		27,878,550	5,318,157

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (290,170)	$ (80,546)	$ (47,671)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	932	431	437
Amortization of debt issuance costs	1,374	888	138
Stock-based compensation expense	26,381	10,550	6,530
Loss on extinguishment of debt		1,007
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(469)	(1,154)	(778)
Other assets	410	20	(519)
Accounts payable	(2,114)	1,955	(1,763)
Accrued direct research and other current and long-term liabilities	11,975	4,417	6,973
Payable to collaborators	216,862
Deferred revenue	(216,332)	(21,351)	(46,603)
Net cash used in operating activities	(251,151)	(83,783)	(83,256)
Investing activities
Sales/disposals of fixed assets			1
Purchases of property and equipment	(2,673)	(679)	(344)
Net cash used in investing activities	(2,673)	(679)	(343)
Financing activities
Proceeds from issuance of common stock	492,453	233,496	108,910
Payments on deferred offering costs	(71)	(627)	(404)
Proceeds from long-term debt	75,000	60,000	20,000
Payments on deferred issuance costs	(576)	(2,290)	(524)
Exercise of options	13,445	1,885	660
Other shareholder transactions	107	8	5
Net cash provided by financing activities	580,358	292,472	128,647
Net increase in cash and cash equivalents	326,534	208,010	45,048
Cash and cash equivalents at beginning of year	337,790	129,780	84,732
Cash and cash equivalents at end of period	664,324	337,790	129,780
Supplemental disclosures
Cash paid for interest	8,207	4,741	1,164
Purchases of equipment in accounts payable and other current liabilities	302	$ 492	$ 13
Accrued deferred offering cost	447
Non-cash activity:
Right-of-use assets obtained in exchange for lease obligations	$ 9,068

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	1. Description of Business The Company’s mission is to identify, develop, and commercialize innovative therapies that change patients’ lives for the better. The Company focuses on small-molecule therapeutics with novel mechanisms of action for the treatment of severe, life-threatening diseases with few or no approved therapies. The Company’s lead programs are in rare forms of chronic kidney disease (CKD) and a rare neurological disease. The Company recently announced positive topline data from registrational studies for both of its lead product candidates, bardoxolone in patients with CKD caused by Alport syndrome, and omaveloxolone in patients with a neurological disorder called FA. Both bardoxolone and omaveloxolone activate the transcription factor Nrf2 to normalize mitochondrial function, restore redox balance, and resolve inflammation. Because mitochondrial dysfunction, oxidative stress, and inflammation are features of many diseases, the Company believes bardoxolone and omaveloxolone have many potential clinical applications. Reata possesses exclusive, worldwide rights to develop, manufacture and commercialize bardoxolone, omaveloxolone, and our next-generation Nrf2 activators, excluding certain Asian markets for bardoxolone in certain indications which are licensed to KKC. 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.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Revenue Recognition The Company’s revenue to date has been generated primarily from licensing fees received under its collaborative licensing agreements with AbbVie Inc. (AbbVie) and Kyowa Kirin Co., Ltd. (KKC) and reimbursements for expenses from KKC. The terms of the agreements include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones, and royalties on net product sales. Under Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when or as the performance obligation is satisfied. Licenses of intellectual property: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price, which is then allocated to each performance obligation. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration, and other revenues and earnings in the period of adjustment and in future periods through the end of the performance obligation period. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and, if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded when the customer obtains control of the goods, which is upon delivery. For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements C ash 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. Acquired License Rights All acquired license and sublicense costs that are in-process research and development (the IPR&D), which were acquired directly in a transaction other than a business combination that does not have an alternative future use are expensed as incurred. For a complete discussion of accounting for reacquisition of license rights in 2019, see Note 3, Collaboration Agreements 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, 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 (CROs), manufacture of clinical drug products for clinical studies, preclinical study costs, discovery research expenses, facilities costs, salaries, and related expenses. In December 2017, the Company and KKC entered into the Third Supplement to the KKC Agreement, which allows the Company to begin a portion of the registrational CARDINAL trial in Japan, for which KKC has reimbursed costs incurred of $3.0 million as of December 31, 2019. The Company deemed that this was not a material modification to the KKC Agreement because no payment terms or deliverables were changed. The Company’s expenses were reduced by $0.5 million, $2.0 million, and $0.5 million for KKC’s share of the study costs for twelve months ended December 31, 2019, 2018, and 2017, respectively. 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 CROs 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. Included within total accrued direct research liabilities is $17.40 million, which was accrued but unbilled, as of December 31, 2019. 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 Manufacturing equipment 10 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 Accounting Standards Codification (ASC) Topic 360, Property, Plant and Equipment Patents 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 United States 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. Stock option and restricted stock awards have been granted or sold at fair value to nonemployees, in connection with research and consulting services provided to the Company, and to employees, in connection with Stock Purchase and Restriction Agreements. Equity awards generally vest over terms of four or five years. For employees, stock-based compensation expense is recorded ratably through the vesting period for each stock option or tranche of restricted stock award. For option awards with performance conditions, the Company evaluates the probability of the number of shares that are expected to vest and adjusts compensation expense to reflect the number of shares expected to vest and the cumulative vesting period met to date. 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. 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 units 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. Leases At the inception of an arrangement, the Company determines if an arrangement is, or contains, a lease based on the unique facts and circumstances present in that arrangement. Lease assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the obligation to make lease payments arising from the lease. These assets and liabilities are initially recognized at the lease commencement date based on the present value of lease payments over the lease term calculated using its incremental borrowing rate based on the information available at commencement unless the implicit rate is readily determinable. Lease assets also include upfront lease payments, lease incentives paid, and direct costs incurred and exclude lease incentives received. The lease term used to calculate the lease assets and related lease liabilities includes the options to extend or terminate the lease when it is reasonably certain that the Company will exercise those options. Lease expense for operating leases is recognized on a straight-line basis over the expected lease term as an operating expense while the expense for finance leases is recognized as depreciation expense over the expected lease term unless there is a transfer of title or purchase option reasonably certain of exercise. The Company accounts for each lease component separately from the nonlease components. The depreciable life of lease assets and leasehold improvements is limited by the expected lease term unless there is a transfer of title or purchase option reasonably certain of its exercise. Leases with an initial term of 12 months or less are not recorded on the balance sheet, and the expenses for these short-term leases and operating leases are recognized on a straight-line basis over the lease term 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, 2019, 2018, and 2017 were immaterial. Recent Accounting Pronouncements Adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, amended by ASU 2018-11, Leases Leases Recently Issued Accounting Pronouncements Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements Revenue from Contracts with Customers he Company is finalizing the impact of the guidance on its consolidated financial statements and does not anticipate that this guidance will have a material impact .

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration Agreements	3. Collaboration Agreements AbbVie In September 2010, the Company entered into a license agreement with AbbVie (the AbbVie License Agreement) for an exclusive license to develop and commercialize bardoxolone in the Licensee Territory (as defined in the AbbVie License Agreement), in exchange for nonrefundable up-front license fee of $150.0 million and additional development and commercial milestone payments. As of December 31, 2019, the Company has received $150.0 million up-front license payment and $150.0 million related to regulatory development milestone payments from AbbVie. The up-front license fee, milestone payments, 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 to AbbVie, which occurred in November 2010 and, accordingly, recognized approximately $0 million, $0 million, and $18.4 million in collaboration revenue during the years ended December 31, 2019, 2018, and 2017, respectively. As of November 2017, the deferred revenue has been fully recognized. The agreement was amended in October 2019, see discussion below. In December 2011, the Company entered into a collaboration agreement with AbbVie (the 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 $400.0 million. The Company was also participating with AbbVie on joint steering committees. Revenue was initially being recognized ratably through December 2026 , which was the estimated minimum period needed to complete the deliverables under the terms of the Collaboration Agreement. The agreement was amended in October 2019, see discussion below. The Company recognized approximately $20.6 million , $26.6 million , and $26.6 million as collaboration revenue during the years ended December 31, 2019, 2018, and 2017 , respectively. As of December 31, 2019 and 2018 , the Company recorded deferred revenue totaling approximately $0 million and $211.6 million , respectively, of which approximately $0 million and $26.6 million , respectively, is reflected as the current portion of deferred revenue. In October 2019, the Company and AbbVie entered into an Amended and Restated License Agreement (the Reacquisition Agreement), under which the Company reacquired the development, manufacturing, and commercialization rights provided in the AbbVie License Agreement and the Collaboration Agreement. Under the Reacquisition Agreement, the AbbVie License Agreement and the Collaboration Agreement were amended, resulting in AbbVie granting its exclusive sublicenses back to the Company, such that the Company reacquired the worldwide rights to bardoxolone, excluding certain Asian countries previously licensed to KKC, and the worldwide rights to omaveloxolone and certain next-generation Nrf2 activators. By reacquiring its rights, the Company was relieved from its performance obligations under the AbbVie License Agreement and the Collaboration Agreement. In exchange for such rights, the Company agreed to pay AbbVie $330.0 million, of which $100.0 million was paid as of December 31, 2019, $150.0 million will be payable on June 30, 2020, and $80.0 million will be payable on November 30, 2021. Additionally, the Company will pay AbbVie an escalating, low single-digit royalty on worldwide net sales, on a product-by-product basis, of omaveloxolone and certain next-generation Nrf2 activators. After the $330.0 million has been paid to AbbVie, the licenses granted to AbbVie and the sublicenses granted to the Company with respect to omaveloxolone and certain next-generation Nrf2 activators, will be terminated, with all rights reverting to the Company, and, if (or when) 18 months has elapsed since the execution of the Agreement, the licenses granted to AbbVie and the sublicenses granted to the Company with respect to bardoxolone, also will be terminated, with all rights reverting to the Company. Following the execution of the Reacquisition Agreement, the Company recorded current portion of payable to collaborators of $250.0 million and payable to collaborators, net of current portion of $80.0 million, at its present value of $65.5 million, with the remaining $14.5 million considered as imputed interest, using the effective interest rate of 9.8%, in accordance with ASC 835-30, Interest—Imputation As of December 31, 2019, the Company paid AbbVie $100.0 million, reducing its current portion of payable to collaborators to $150.0 million, and recognized $1.4 million in interest expense, which increased the payable to collaborators, net of current portion, to $66.9 million. KKC In December 2009, the Company entered into the KKC Agreement for an exclusive license to develop and commercialize bardoxolone in the KKC Licensed Territory. The terms of the agreement include payment to the Company of a nonrefundable, up-front license fee of $35.0 million and additional development and commercial milestone payments. As of December 31, 2019, the Company received $45.0 million related to regulatory development milestone payments from KKC and has the potential in the future to achieve another $52.0 million from six regulatory milestones and $140.0 million from four 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 KKC in the KKC Licensee Territory. The Company is participating on a joint steering committee with KKC to oversee the development and commercialization activities related to bardoxolone. 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 KKC Agreement. The up-front payment and regulatory milestones are accounted for as a single unit of accounting. Revenue is being recognized ratably through December 2021, which is the estimated minimum period that is needed to complete the deliverables under the terms of the KKC Agreement. The Company began recognizing revenue related to the up-front payment upon transfer of the license and technical knowledge of bardoxolone to KKC, which occurred in December 2009, and, accordingly, recognized approximately $4.7 million, $24.7 million, and $1.5 million as collaboration revenue during the years ended December 31, 2019, 2018, and 2017, respectively. As of December 31, 2019 and 2018, the Company recorded deferred revenue totaling approximately $9.4 million and $14.1 million, respectively, of which approximately $4.7 million and $4.7 million respectively, is reflected as the current portion of deferred revenue.

Other Income (Expense), Net

Other Income (Expense), Net	12 Months Ended
	Dec. 31, 2019
Other Income And Expenses [Abstract]
Other Income (Expense), Net	4. Other Income (Expense), Net Years Ended December 31 2019 2018 2017 Other income (expense), net Investment income $ 6,248 $ 3,541 $ 701 Interest expense (11,197 ) (6,176 ) (1,454 ) Loss on extinguishment of debt — (1,007 ) — Other income (expense) 7 — (3 ) Total other income (expense), net $ (4,942 ) $ (3,642 ) $ (756 ) Investment Income Interest income consists primarily of interest generated from our cash and cash equivalents. Interest Expense Interest expense consists primarily of interest on our borrowing activities under our loan agreements and the imputed interest from amount due to AbbVie under the Reacquisition Agreement. Loss on extinguishment of debt In June 2018, the Company borrowed the remaining $60.0 million available under the Restated Loan Agreement and recorded a loss on extinguishment as a result of the debt modification of $1.0 million, which consisted primarily of lender fees and unamortized debt issuance costs. Other income (expense) Other income (expense) consists primarily of gains and losses on foreign currency exchange and sales of assets.

Term Loan

Term Loan	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Term Loan	5. 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 $35.0 million, issuable in two separate term loans of $20.0 million (Term A Loan) and $15.0 million (Term B Loan, and together with the Term A Loan, the Term Loans). On March 31, 2017, the Company borrowed $20.0 million from the Term A Loan. On November 3, 2017, the Company amended the Loan Agreement (Amended Loan Agreement) and increased the Term B Loan amount to either $20.0 million or $25.0 million, which extended the interest only period from six to twelve months if the Term B Loan is drawn. The Company paid an amendment fee of $0.3 million on November 8, 2017, upon the execution of the Amended Loan Agreement. On June 14, 2018, the Company entered into an Amended and Restated Loan and Security Agreement (the Restated Loan Agreement). Under the Restated Loan Agreement, the Term A Loan was increased from $20.0 million to $80.0 million and the Term B Loan availability was increased to $45.0 million, which became available on October 14, 2019. On June 14, 2018, the Company borrowed the remaining $60.0 million available under the Term A Loan and recorded a loss on extinguishment as a result of the debt modification of $1.0 million, which consisted primarily of lender fees and unamortized debt issuance costs. On October 9, 2019, the Company entered into the First Amendment to Amend and Restated Loan and Security Agreement (the Amended Restated Loan Agreement). Under the Amended Restated Loan Agreement, the Term B Loan availability was increased from $45.0 million to $75.0 million. On December 20, 2019, the Company borrowed $75.0 million under the Term B Loan. All outstanding Term Loans will mature on June 1, 2023. The Company will make interest-only payments for 36 months through June 1, 2021. The interest-only payment period will be followed by 24 equal monthly payments of principal and interest payments. The Term Loans will bear interest at a floating per annum rate calculated as 7.79% plus the greater of the 30-day United States 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 1.91%, with a minimum rate of 9.7% and maximum rate of 12.29%. Under the Term A Loan, 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) the aggregate amount of interest that the Company would have paid through the maturity date if prepayment is made on or before the first anniversary of the applicable funding date of the Term Loan, (b) 4.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the first anniversary date and on or before the second anniversary of the applicable funding date, (c) 3.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after second anniversary date and on or before the third anniversary of the applicable funding date, or (d) 1.5% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the third anniversary date and on or before the fourth anniversary of the applicable funding date. Under the Term B Loan, the Company will be obligated to pay a prepayment fee equal to (a) 4.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made on or before the first anniversary of the applicable funding date of the Term Loan, (b) 3.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after the first anniversary date and on or before the second anniversary of the applicable funding date, (c) 1.50% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after second anniversary date and on or before the third anniversary of the applicable funding date, and (d) 0.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after the third anniversary date of the funding date and prior to the maturity date. The Company will also be required to make a final exit fee payment of 6.5% of the principal balance of the Term A Loan and 2.0% of the Term B Loan, payable on the earliest of the prepayment of the Term Loans, acceleration of any Term Loan, or at maturity of the Term Loans. The Term Loans have a current effective interest rate of 10.29% before debt issuance costs and final exit fee and 12.17% including debt issuance costs and final exit fee. The Company is in compliance with all covenants under the Amended Restated Loan Agreement as of December 31, 2019. 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 Amended Restated Loan Agreement are secured by substantially all of its current and future assets, including its owned intellectual property. Term A and B Loan and unamortized issuance cost balance as of December 31(in thousands): 2019 2018 Principal Amount $ 155,000 $ 80,000 Exit Fee 6,700 5,200 Less unamortized issuance cost 6,683 5,981 Total long-term debt, net of debt issuance cost $ 155,017 $ 79,219 The future principal payments by fiscal year for the Company’s Term A and B Loans: As of December 31, 2019 (in thousands) 2020 $ — 2021 45,208 2022 77,500 2023 32,292 $ 155,000

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment	6. Property and Equipment Property and equipment consisted of the following as of December 31(in thousands): 2019 2018 Computer equipment and software $ 3,031 $ 2,414 Laboratory equipment 5,049 5,025 Office furniture 1,993 1,331 Office and other equipment 418 286 Leasehold improvements 5,656 5,103 Manufacturing equipment 118 — 16,265 14,159 Less accumulated depreciation and amortization 13,269 12,714 Property and equipment, net $ 2,996 $ 1,445

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	7. Leases The Company headquarters is located in Plano, Texas, where it leases approximately 122,000 square feet of office space. The Company leases additional office space located in Irving, Texas, where it leases approximately 34,890 square feet of office and laboratory space. On December 12, 2019, the Company amended its operating lease agreements for the Irving and Plano offices to extend the lease terms through October 31, 2022 with an option to renew up to six months and through April 30, 2022 with four successive three-month On October 15, 2019, the Company and TC Legacy Land Venture, LLC entered into a lease agreement (the 2019 Lease Agreement) of a single-tenant and build-to-suit building of approximately 327,400 square feet of office and laboratory space located in Plano, Texas with an initial lease term of 16 years. At the Company’s option, it may renew the lease for two consecutive five-year renewal periods or one ten-year renewal period. The Company does not have control of the space or the construction prior to completion of construction. Therefore, no right-of-use or lease liabilities were recorded in connection with the 2019 Lease Agreement as of December 31, 2019. At December 31, 2019, the weighted average incremental borrowing rate and the weighted average remaining lease term for the operating leases held by the Company were 9.6% and 2.8 years, respectively. During the year ended December 31, 2019, cash paid for amounts included for the measurement of lease liabilities was $2.4 million and the Company recorded operating lease expense of $3.4 million. The Company has elected to net the amortization of the right-of-use assets and the reduction of the lease liabilities principal in accrued direct research and other current and long-term liabilities on the consolidated statements of cash flows. Supplemental balance sheet information related to the Company’s operating leases is as follows: Balance Sheet Classification As of December 31, 2019 (in thousands) Non-current right-of-use assets Other assets $ 9,068 Current lease liabilities Other current liabilities $ 3,156 Non-current lease liabilities Other long-term liabilities $ 6,982 Maturities of lease liabilities by fiscal year for the Company’s operating leases: As of December 31, 2019 (in thousands) 2020 $ 3,994 2021 4,142 2022 3,500 Total lease payments 11,636 Less: Imputed interest 1,498 Present value of lease liabilities $ 10,138 For the year ended December 31, 2019, 2018, and 2017, the Company recorded total rent expense of approximately $3.4 million, $0.6 million, and $0.5 million respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The provision and benefits for taxes on income are immaterial to the financials as of December 31, 2019, 2018, and 2017. The following table reconciles the Company’s effective income tax rate from continuing operations to the federal statutory tax rate of 21%: 2019 2018 2017 U.S. federal income taxes 21 % 21 % 35 % Stock-based compensation 5 1 — Change in valuation allowance (34 ) (34 ) 48 2017 Tax Act — — (111 ) Federal and state tax credits 8 12 28 Recorded federal income tax benefit (provision) 0 % 0 % 0 % 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 United States corporate income tax system. These changes included a federal statutory rate reduction from 35% to 21% and the elimination or reduction in the deductibility of certain credits and limitations, such as Credits related to designated orphan drugs, net operating losses, interest expense, and executive compensation. The federal statutory rate reduction took effect on January 1, 2018. As a result of the reduction of federal corporate income tax rates, the Company recorded a reduction of $53.1 million at December 31, 2017 to its deferred tax assets. The Company’s deferred tax assets were fully offset by a valuation allowance in 2018 as the Company cannot currently conclude that it is more likely than not that the remaining deferred tax assets will be utilized. 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): 2019 2018 Deferred tax assets: Deferred revenue $ 1,976 $ 47,432 Net operating loss 96,194 45,011 Federal and state tax credits 54,559 30,739 Intellectual property 67,384 — Stock-based compensation 7,741 4,072 Other 2,684 641 Deferred tax assets before valuation allowance 230,538 127,895 Less: Valuation allowance (226,261 ) (127,752 ) Net deferred income tax assets 4,277 143 Deferred tax liabilities: Deferred purchase price (1,972 ) — Right-of-use assets (1,908 ) — Other (397 ) (143 ) Net deferred tax assets (liabilities) $ — $ — 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. 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 continue to be fully offset by a valuation allowance in 2019. 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 increased by $98.5 million and $27.2 million in 2019 and 2018, respectively. As of December 31, 2019, the Company had federal accumulated net operating losses of approximately $457.2 million of which $0.3 million are subject to an annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended (Section 382). Approximately $120.4 million of the net operating loss carryforwards expire between fiscal years 2023 and 2037. Under the 2017 Tax Act, the remaining $336.8 million will be carried forward indefinitely but is limited to 80% of our taxable income. As of December 31, 2019, the Company has federal orphan drug tax credit and federal and state research and development tax credit carryforwards of $45.6 million and $8.9 million, which expire between fiscal years 2024 and 2039. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease within the next 12 months. The IRS completed an examination of the Company’s United States income tax returns for 2013, 2014, and 2015 and proposed adjustments with respect to certain items that were reported by the Company for the 2013 tax year. In June 2018, the Company received the Revenue Agent Report from the IRS. The Company submitted an administrative protest with the IRS, contesting the examination team’s proposed adjustments. The issue was appealed with the IRS and resolved with no adjustment during the current year. The IRS has completed an examination of the Company’s U.S. income tax returns for 2009, 2011, 2012, 2013, 2014, and 2015, with no significant adjustments. 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, 2019
Commitments And Contingencies Disclosure [Abstract]
Patents	9. 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

Licenses

Licenses	12 Months Ended
	Dec. 31, 2019
License Agreements [Abstract]
Licenses	10. 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 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 July 2012, the Company amended the 2004 CDDO License Agreement, which provides, among other terms, that the Company will pay to the licensors a low single-digit royalty on net sales of certain Nrf2 activator compounds under the Collaboration Agreement, including omaveloxolone, that are claimed in certain patents and patent applications that are wholly owned by or assigned to the Company as identified in the Collaboration Agreement. In January 2009, the Company filed a patent application claiming the use of bardoxolone 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. In February 2019, the Company paid a milestone fee of $0.1 million related to achievement of a milestone under the agreement. 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.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Convertible Preferred Stock	11. Convertible Preferred Stock Under our Tenth Amended and Restated Certificate of Incorporation, The Company has 100,000,000 undesignated shares of convertible preferred stock. As of December 31, 2019 and 2018, there were no shares of convertible preferred stock issued and outstanding.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	12. Stock-Based Compensation The Second Amended and Restated Long Term Incentive Plan (the LTIP Plan) Reserved Shares At December 31, 2019, common stock reserved for issuance is as follows: Outstanding common stock options under the LTIP Plan 4,023,276 Outstanding common stock options under standalone option agreements 15,673 Issued and unvested restricted stock units under the LTIP Plan 50,000 Common stock available for future grant under the LTIP Plan 2,385,592 Total common shares reserved for future issuance 6,474,541 As of December 31, 2019, 50,000 shares of restricted stock units and options to purchase 4,038,949 shares have been granted and are outstanding under the Plan and standalone option agreements. Additional detail on stock compensation costs can be found below. Restricted Stock Units (RSUs) RSUs, including performance-based awards, were granted to key employees of the Company under the LTIP Plan. The fair value of these RSUs were determined based on the estimated fair value of the Company’s common stock at the date of grant and the vesting is subject to the satisfaction of service requirements or the satisfaction of achieving certain performance targets. The following table summarizes RSUs as of December 31, 2019, under the LTIP Plan agreements: Number Performance Based RSUs Weighted-Average Grant Date Fair Value Outstanding at January 1, 2019 — $ — Granted 50,000 72.70 Vested — — Forfeited — — Outstanding at December 31, 2019 50,000 $ 72.70 The Company recognizes stock-based compensation expense for the performance-based awards for awards when achievement of the underlying performance-based targets become probable, which have typically been in the same period as when the targets are achieved. As of the grant date and December 31, 2019, the fair value of RSUs granted in 2019 is approximately $3.6 million, of which the Company has not recognized any compensation expense. Stock Options Stock Options, including serviced-based and performance-based awards, were granted under the LTIP Plan. The Company measures stock awards at fair value on the date of grant. Stock options granted with service-based vesting conditions are recorded as an expense using the straight-line method. In the case of performance-based options, we recognize stock-based compensation expense related to these awards when achievement of the underlying research and development performance-based targets become probable, which have typically been in the same period as when the targets are achieved. The Company accounts for forfeitures when they occur. The following table summarizes time-based and performance-based stock compensation expense reflected in the consolidated statements of operations (in thousands): Years Ended December 31 2019 2018 2017 Research and development $ 8,692 $ 3,943 $ 2,409 General and administrative 17,689 6,607 4,121 $ 26,381 $ 10,550 $ 6,530 At December 31, 2019, 50,000 performance-based stock options were both outstanding and unvested, and the total unrecognized stock-based compensation expense related to those awards was $2.3 million. The following table summarizes stock option activity as of December 31, 2019, and changes during the years ended December 31, 2019, under the LTIP Plan and standalone option agreements: Number of Options Weighted- Average Price Outstanding at January 1, 2019 3,320,571 $ 21.20 Granted 1,702,533 69.76 Exercised (707,849 ) 18.99 Forfeited (276,306 ) 34.42 Outstanding at December 31, 2019 4,038,949 $ 41.24 Exercisable at December 31, 2019 1,701,135 $ 25.12 At December 31, 2019, 4,038,949 stock options are fully vested or are expected to vest and have a weighted-average outstanding term of 7.92 years and a weighted-average exercise price of $41.24. Exercisable stock options have a weighted-average outstanding term of 7.01 years. 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 2019 2018 2017 Dividend yield — % — % — % Volatility 73.73 % 72.77 % 75.14 % Risk-free interest rate 2.18 % 2.79 % 2.19 % Expected term of options (in years) 6.23 6.35 6.37 Weighted average grant date fair value $ 69.76 $ 38.14 $ 25.00 Expected volatility is based on the Company’s own historical volatility since its IPO and benchmarked public companies during fiscal years 2019, 2018 and 2017. The risk-free interest rate, ranging from 1.35% to 2.67% The total intrinsic value (the difference between market value and exercise prices of in-the-money options) of all outstanding options at December 31, 2019, 2018, and 2017, was $659.3 million, $115.8 million, and $28.6 million, respectively. The total intrinsic value of exercisable options at December 31, 2019, 2018, and 2017, was $305.0 million, $56.9 million, and $11.5 million, respectively. In 2019, 2018, and 2017, 707,849, 137,352, and 59,112 options were exercised, respectively. The total intrinsic value of options exercised was $79.4

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and Contingencies 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, 2019. 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.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss per Share	14. Net Loss per Share The computation of basic and diluted net loss income per share attributable to common stockholders of the Company for the years ended December 31 is summarized in the following table: 2019 2018 2017 Numerator Net loss (in thousands) $ (290,170 ) $ (80,546 ) $ (47,671 ) Denominator Weighted-average number of common shares used in net loss per share – basic 30,414,203 27,701,783 23,933,309 Dilutive potential common shares — — — Weighted-average number of common shares used in net loss per share – diluted 30,414,203 27,701,783 23,933,309 Net loss per share – basic $ (9.54 ) $ (2.91 ) $ (1.99 ) Net loss per share – diluted $ (9.54 ) $ (2.91 ) $ (1.99 ) 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 4,088,949, 3,320,571, and 3,251,696 shares for the years ended 2019, 2018, and 2017, respectively.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2019
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data	15. Selected Quarterly Financial Data The following table contains quarterly financial information for 2019 and 2018. 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). 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 7,770 $ 7,833 $ 8,242 $ 2,672 Total expenses (1) 36,322 41,492 46,820 187,103 Total other income (expense) (600 ) (701 ) (1,078 ) (2,563 ) Provision for taxes on income 2 20 38 (52 ) Net loss $ (29,154 ) $ (34,380 ) $ (39,694 ) $ (186,942 ) Net loss per share – basic and diluted $ (0.98 ) $ (1.14 ) $ (1.32 ) $ (5.91 ) ( 1) 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 32,392 $ 7,571 $ 5,175 $ 8,451 Total expenses 28,136 34,223 34,735 33,373 Total other income (expense) (174 ) (1,553 ) (1,266 ) (649 ) Provision for taxes on income — 6 9 11 Net income (loss) $ 4,082 $ (28,211 ) $ (30,835 ) $ (25,582 ) Net income (loss) per share – basic $ 0.16 $ (1.08 ) $ (1.07 ) $ (0.86 ) Net income (loss) per share – diluted $ 0.15 $ (1.08 ) $ (1.07 ) $ (0.86 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events On January 2, 2020, the Company granted an aggregate of 841,765 options to purchase shares of common stock to employees with a grant price of $207.20.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition The Company’s revenue to date has been generated primarily from licensing fees received under its collaborative licensing agreements with AbbVie Inc. (AbbVie) and Kyowa Kirin Co., Ltd. (KKC) and reimbursements for expenses from KKC. The terms of the agreements include non-refundable upfront fees, funding of research and development activities, payments based upon achievement of milestones, and royalties on net product sales. Under Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when or as the performance obligation is satisfied. Licenses of intellectual property: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer, and the customer can use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by the Company) is included in the transaction price, which is then allocated to each performance obligation. Milestone payments that are not within the control of the Company, such as approvals from regulators, are not considered probable of being achieved until those approvals are received. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration, and other revenues and earnings in the period of adjustment and in future periods through the end of the performance obligation period. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and where the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (a) when the related sales occur, or (b) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Manufacturing Supply Services: Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the licensee and, if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the customer exercises these options, any additional payments are recorded when the customer obtains control of the goods, which is upon delivery. For a complete discussion of accounting for collaborative licensing agreements, see Note 3, Collaboration Agreements
Cash and Cash Equivalents	C ash 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.
Acquired License Rights	Acquired License Rights All acquired license and sublicense costs that are in-process research and development (the IPR&D), which were acquired directly in a transaction other than a business combination that does not have an alternative future use are expensed as incurred. For a complete discussion of accounting for reacquisition of license rights in 2019, see Note 3, Collaboration Agreements
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, 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 (CROs), manufacture of clinical drug products for clinical studies, preclinical study costs, discovery research expenses, facilities costs, salaries, and related expenses. In December 2017, the Company and KKC entered into the Third Supplement to the KKC Agreement, which allows the Company to begin a portion of the registrational CARDINAL trial in Japan, for which KKC has reimbursed costs incurred of $3.0 million as of December 31, 2019. The Company deemed that this was not a material modification to the KKC Agreement because no payment terms or deliverables were changed. The Company’s expenses were reduced by $0.5 million, $2.0 million, and $0.5 million for KKC’s share of the study costs for twelve months ended December 31, 2019, 2018, and 2017, respectively. 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 CROs 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. Included within total accrued direct research liabilities is $17.40 million, which was accrued but unbilled, as of December 31, 2019. 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 Manufacturing equipment 10 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 Accounting Standards Codification (ASC) Topic 360, Property, Plant and Equipment
Patents	Patents 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 United States 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. Stock option and restricted stock awards have been granted or sold at fair value to nonemployees, in connection with research and consulting services provided to the Company, and to employees, in connection with Stock Purchase and Restriction Agreements. Equity awards generally vest over terms of four or five years. For employees, stock-based compensation expense is recorded ratably through the vesting period for each stock option or tranche of restricted stock award. For option awards with performance conditions, the Company evaluates the probability of the number of shares that are expected to vest and adjusts compensation expense to reflect the number of shares expected to vest and the cumulative vesting period met to date.
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.
Debt Issuance Costs	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 units 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.
Leases	Leases At the inception of an arrangement, the Company determines if an arrangement is, or contains, a lease based on the unique facts and circumstances present in that arrangement. Lease assets represent the Company’s right to use an underlying asset for the lease term, and lease liabilities represent the obligation to make lease payments arising from the lease. These assets and liabilities are initially recognized at the lease commencement date based on the present value of lease payments over the lease term calculated using its incremental borrowing rate based on the information available at commencement unless the implicit rate is readily determinable. Lease assets also include upfront lease payments, lease incentives paid, and direct costs incurred and exclude lease incentives received. The lease term used to calculate the lease assets and related lease liabilities includes the options to extend or terminate the lease when it is reasonably certain that the Company will exercise those options. Lease expense for operating leases is recognized on a straight-line basis over the expected lease term as an operating expense while the expense for finance leases is recognized as depreciation expense over the expected lease term unless there is a transfer of title or purchase option reasonably certain of exercise. The Company accounts for each lease component separately from the nonlease components. The depreciable life of lease assets and leasehold improvements is limited by the expected lease term unless there is a transfer of title or purchase option reasonably certain of its exercise. Leases with an initial term of 12 months or less are not recorded on the balance sheet, and the expenses for these short-term leases and operating leases are recognized on a straight-line basis over the lease term
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, 2019, 2018, and 2017 were immaterial.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Adopted In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, amended by ASU 2018-11, Leases Leases Recently Issued Accounting Pronouncements Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements Revenue from Contracts with Customers he Company is finalizing the impact of the guidance on its consolidated financial statements and does not anticipate that this guidance will have a material impact .

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
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 Manufacturing equipment 10 years

Other Income (Expense), Net (Ta

Other Income (Expense), Net (Tables)	12 Months Ended
	Dec. 31, 2019
Other Income And Expenses [Abstract]
Summary of Other Income (Expense), Net	Years Ended December 31 2019 2018 2017 Other income (expense), net Investment income $ 6,248 $ 3,541 $ 701 Interest expense (11,197 ) (6,176 ) (1,454 ) Loss on extinguishment of debt — (1,007 ) — Other income (expense) 7 — (3 ) Total other income (expense), net $ (4,942 ) $ (3,642 ) $ (756 )

Term Loan (Tables)

Term Loan (Tables) - Term Loans	12 Months Ended
	Dec. 31, 2019
Debt Instrument [Line Items]
Schedule of Term Loans And Unamortized Issuance Cost Balance	Term A and B Loan and unamortized issuance cost balance as of December 31(in thousands): 2019 2018 Principal Amount $ 155,000 $ 80,000 Exit Fee 6,700 5,200 Less unamortized issuance cost 6,683 5,981 Total long-term debt, net of debt issuance cost $ 155,017 $ 79,219
Schedule of Future Principal Payments for Term Loans	The future principal payments by fiscal year for the Company’s Term A and B Loans: As of December 31, 2019 (in thousands) 2020 $ — 2021 45,208 2022 77,500 2023 32,292 $ 155,000

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment consisted of the following as of December 31(in thousands): 2019 2018 Computer equipment and software $ 3,031 $ 2,414 Laboratory equipment 5,049 5,025 Office furniture 1,993 1,331 Office and other equipment 418 286 Leasehold improvements 5,656 5,103 Manufacturing equipment 118 — 16,265 14,159 Less accumulated depreciation and amortization 13,269 12,714 Property and equipment, net $ 2,996 $ 1,445

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Summary of Supplemental Balance Sheet Information Related to Operating Leases	Supplemental balance sheet information related to the Company’s operating leases is as follows: Balance Sheet Classification As of December 31, 2019 (in thousands) Non-current right-of-use assets Other assets $ 9,068 Current lease liabilities Other current liabilities $ 3,156 Non-current lease liabilities Other long-term liabilities $ 6,982
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities by fiscal year for the Company’s operating leases: As of December 31, 2019 (in thousands) 2020 $ 3,994 2021 4,142 2022 3,500 Total lease payments 11,636 Less: Imputed interest 1,498 Present value of lease liabilities $ 10,138

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Reconciliation of Effective Income Tax Rate from Continuing Operations to Federal Statutory Tax Rate	The following table reconciles the Company’s effective income tax rate from continuing operations to the federal statutory tax rate of 21%: 2019 2018 2017 U.S. federal income taxes 21 % 21 % 35 % Stock-based compensation 5 1 — Change in valuation allowance (34 ) (34 ) 48 2017 Tax Act — — (111 ) Federal and state tax credits 8 12 28 Recorded federal income tax benefit (provision) 0 % 0 % 0 %
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): 2019 2018 Deferred tax assets: Deferred revenue $ 1,976 $ 47,432 Net operating loss 96,194 45,011 Federal and state tax credits 54,559 30,739 Intellectual property 67,384 — Stock-based compensation 7,741 4,072 Other 2,684 641 Deferred tax assets before valuation allowance 230,538 127,895 Less: Valuation allowance (226,261 ) (127,752 ) Net deferred income tax assets 4,277 143 Deferred tax liabilities: Deferred purchase price (1,972 ) — Right-of-use assets (1,908 ) — Other (397 ) (143 ) Net deferred tax assets (liabilities) $ — $ —

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Common Stock Reserved for Issuance	At December 31, 2019, common stock reserved for issuance is as follows: Outstanding common stock options under the LTIP Plan 4,023,276 Outstanding common stock options under standalone option agreements 15,673 Issued and unvested restricted stock units under the LTIP Plan 50,000 Common stock available for future grant under the LTIP Plan 2,385,592 Total common shares reserved for future issuance 6,474,541
Summary of Restricted Stock Units	The following table summarizes RSUs as of December 31, 2019, under the LTIP Plan agreements: Number Performance Based RSUs Weighted-Average Grant Date Fair Value Outstanding at January 1, 2019 — $ — Granted 50,000 72.70 Vested — — Forfeited — — Outstanding at December 31, 2019 50,000 $ 72.70
Summary of Time Based and Performance-Based Stock Compensation Expense	The following table summarizes time-based and performance-based stock compensation expense reflected in the consolidated statements of operations (in thousands): Years Ended December 31 2019 2018 2017 Research and development $ 8,692 $ 3,943 $ 2,409 General and administrative 17,689 6,607 4,121 $ 26,381 $ 10,550 $ 6,530
Summary of Stock Option Activity	The following table summarizes stock option activity as of December 31, 2019, and changes during the years ended December 31, 2019, under the LTIP Plan and standalone option agreements: Number of Options Weighted- Average Price Outstanding at January 1, 2019 3,320,571 $ 21.20 Granted 1,702,533 69.76 Exercised (707,849 ) 18.99 Forfeited (276,306 ) 34.42 Outstanding at December 31, 2019 4,038,949 $ 41.24 Exercisable at December 31, 2019 1,701,135 $ 25.12
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 2019 2018 2017 Dividend yield — % — % — % Volatility 73.73 % 72.77 % 75.14 % Risk-free interest rate 2.18 % 2.79 % 2.19 % Expected term of options (in years) 6.23 6.35 6.37 Weighted average grant date fair value $ 69.76 $ 38.14 $ 25.00

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2019
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 of the Company for the years ended December 31 is summarized in the following table: 2019 2018 2017 Numerator Net loss (in thousands) $ (290,170 ) $ (80,546 ) $ (47,671 ) Denominator Weighted-average number of common shares used in net loss per share – basic 30,414,203 27,701,783 23,933,309 Dilutive potential common shares — — — Weighted-average number of common shares used in net loss per share – diluted 30,414,203 27,701,783 23,933,309 Net loss per share – basic $ (9.54 ) $ (2.91 ) $ (1.99 ) Net loss per share – diluted $ (9.54 ) $ (2.91 ) $ (1.99 )

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2019
Selected Quarterly Financial Information [Abstract]
Selected Quarterly Financial Data	The following table contains quarterly financial information for 2019 and 2018. 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). 2019 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 7,770 $ 7,833 $ 8,242 $ 2,672 Total expenses (1) 36,322 41,492 46,820 187,103 Total other income (expense) (600 ) (701 ) (1,078 ) (2,563 ) Provision for taxes on income 2 20 38 (52 ) Net loss $ (29,154 ) $ (34,380 ) $ (39,694 ) $ (186,942 ) Net loss per share – basic and diluted $ (0.98 ) $ (1.14 ) $ (1.32 ) $ (5.91 ) ( 1) 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total collaboration revenue $ 32,392 $ 7,571 $ 5,175 $ 8,451 Total expenses 28,136 34,223 34,735 33,373 Total other income (expense) (174 ) (1,553 ) (1,266 ) (649 ) Provision for taxes on income — 6 9 11 Net income (loss) $ 4,082 $ (28,211 ) $ (30,835 ) $ (25,582 ) Net income (loss) per share – basic $ 0.16 $ (1.08 ) $ (1.07 ) $ (0.86 ) Net income (loss) per share – diluted $ 0.15 $ (1.08 ) $ (1.07 ) $ (0.86 )

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Asset impairment charges	$ 0	$ 0	$ 0
Operating lease right-of-use asset	9,068,000			$ 1,500,000
Operating lease liability	$ 10,138,000			$ 1,700,000
Minimum
Significant Accounting Policies [Line Items]
Equity vesting terms	4 years
Maximum
Significant Accounting Policies [Line Items]
Equity vesting terms	5 years
Collaborative Arrangement
Significant Accounting Policies [Line Items]
Unbilled research and development expense accrued	$ 17,400,000
KKC | License Agreement Terms
Significant Accounting Policies [Line Items]
Reduction in research and development expense	500,000	$ 2,000,000	$ 500,000
KKC | Clinical Development Milestones | License Agreement Terms
Significant Accounting Policies [Line Items]
Reduction in research and development expense	$ 3,000,000

Summary of Estimated Useful Liv

Summary of Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
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
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	10 years

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) $ in Thousands	Oct. 31, 2019USD ($)	Dec. 31, 2011USD ($)	Sep. 30, 2010USD ($)	Dec. 31, 2009USD ($)	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)Milestone	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 30, 2021USD ($)	Jun. 30, 2020USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue					$ 2,672	$ 8,242	$ 7,833	$ 7,770	$ 8,451	$ 5,175	$ 7,571	$ 32,392	$ 26,517	$ 53,589	$ 48,058
Deferred revenue, current					4,701				31,335				4,701	31,335
Payable to collaborators	$ 65,500				100,000								100,000
Current portion of payable to collaborators	250,000				150,000								150,000
Payable to collaborators, net of current portion	80,000				66,862								66,862
Reacquired license rights													124,398
AbbVie
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payable to collaborators	330,000				100,000								100,000
Reacquired license rights					124,400
AbbVie | Forecast
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payable to collaborators																$ 80,000	$ 150,000
AbbVie | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue													$ 20,600	26,600	26,600
Deferred revenue, expected timing of recognition													2026-12
Deferred revenue					0				211,600				$ 0	211,600
Deferred revenue, current					0				26,600				0	26,600
Up-front collaboration payment received		$ 400,000
AbbVie | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received			$ 150,000
Collaboration revenue, milestone payments received													150,000
Collaboration revenue, milestone payments received													150,000
Collaboration revenue													0	0	18,400
Collaboration revenue, milestone payments received													150,000
Reacquisition Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 191,100
Percentage of effective interest rate	9.80%
Imputed interest	$ 14,500
Reacquired license rights	124,400
Reacquired license rights value discount	$ 14,500
Interest expense													1,400
KKC Agreement | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee received				$ 35,000
Collaboration revenue, milestone payments received													45,000
Collaboration revenue													$ 4,700	24,700	$ 1,500
Deferred revenue, expected timing of recognition													2021-12
Deferred revenue					9,400				14,100				$ 9,400	14,100
Deferred revenue, current					4,700				$ 4,700				4,700	$ 4,700
Collaboration revenue, milestone payments received													45,000
Collaboration revenue, potential milestone payments					52,000								$ 52,000
Number of regulatory development milestones | Milestone													6
Collaboration revenue, additional potential commercial milestone payments					$ 140,000								$ 140,000
Number of commercial milestones | Milestone													4

Other Income (Expense), Net - S

Other Income (Expense), Net - Summary of Other Income (Expense), Net (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other income (expense), net
Investment income									$ 6,248	$ 3,541	$ 701
Interest expense									(11,197)	(6,176)	(1,454)
Loss on extinguishment of debt										(1,007)
Other income (expense)									7		(3)
Total other income (expense), net	$ (2,563)	$ (1,078)	$ (701)	$ (600)	$ (649)	$ (1,266)	$ (1,553)	$ (174)	$ (4,942)	$ (3,642)	$ (756)

Other Income (Expense), Net - A

Other Income (Expense), Net - Additional Information (Details) - USD ($) $ in Thousands	Jun. 14, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Other Nonoperating Income Expense [Line Items]
Proceeds from long-term debt		$ 75,000	$ 60,000	$ 20,000
Loss on extinguishment of debt			$ 1,007
Amended and Restated Loan and Security Agreement
Schedule Of Other Nonoperating Income Expense [Line Items]
Loss on extinguishment of debt	$ 1,000
Amended and Restated Loan and Security Agreement | Term Loan A
Schedule Of Other Nonoperating Income Expense [Line Items]
Proceeds from long-term debt	$ 60,000

Term Loan - Additional Informat

Term Loan - Additional Information (Details)	Dec. 20, 2019USD ($)	Jun. 14, 2018USD ($)	Nov. 08, 2017USD ($)	Nov. 03, 2017USD ($)	Mar. 31, 2017USD ($)TermLoan	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Oct. 09, 2019USD ($)
Debt Instrument [Line Items]
Proceeds from long-term debt						$ 75,000,000	$ 60,000,000	$ 20,000,000
Loss on extinguishment of debt							$ 1,007,000
Debt instrument, effective interest rate before debt issuance costs and final exit fee						10.29%
Debt instrument, effective interest rate including debt issuance costs and final exit fee						12.17%
Loan And Security Agreement
Debt Instrument [Line Items]
Number of term loans | TermLoan					2
Loan And Security Agreement | Term Loans
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 35,000,000
Loan And Security Agreement | Term Loan A
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 20,000,000	20,000,000
Proceeds from long-term debt					20,000,000
Loan And Security Agreement | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 15,000,000
Amended Loan Agreement | Term Loan B
Debt Instrument [Line Items]
Debt instrument, interest only period				6 months
Payment of amendment fee			$ 300,000
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 | If Term B Loan is Drawn
Debt Instrument [Line Items]
Debt instrument, interest only period				12 months
Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Loss on extinguishment of debt		$ 1,000,000
Amended and Restated Loan and Security Agreement | Term Loans
Debt Instrument [Line Items]
Debt instrument, payment terms						All outstanding Term Loans will mature on June 1, 2023.  The Company will make interest-only payments for 36 months through June 1, 2021.  The interest-only payment period will be followed by 24 equal monthly payments of principal and interest payments.
Debt instrument, maturity date						Jun. 1, 2023
Debt instrument, interest rate terms						The Term Loans will bear interest at a floating per annum rate calculated as 7.79% plus the greater of the 30-day United States 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 1.91%, with a minimum rate of 9.7% and maximum rate of 12.29%.
Debt instrument, annual interest rate						7.79%
Debt instrument, basis spread on variable rate						1.91%
Amended and Restated Loan and Security Agreement | Term Loans | Minimum
Debt Instrument [Line Items]
Debt instrument, annual interest rate						9.70%
Amended and Restated Loan and Security Agreement | Term Loans | Maximum
Debt Instrument [Line Items]
Debt instrument, annual interest rate						12.29%
Amended and Restated Loan and Security Agreement | Term Loan A
Debt Instrument [Line Items]
Maximum borrowing capacity		80,000,000
Proceeds from long-term debt		60,000,000
Debt instrument, prepayment terms						Under the Term A Loan, 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) the aggregate amount of interest that the Company would have paid through the maturity date if prepayment is made on or before the first anniversary of the applicable funding date of the Term Loan, (b) 4.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the first anniversary date and on or before the second anniversary of the applicable funding date, (c) 3.0% of the outstanding principal balance of the applicable Term Loan if prepayment is made after second anniversary date and on or before the third anniversary of the applicable funding date, or (d) 1.5% of the outstanding principal balance of the applicable Term Loan if prepayment is made after the third anniversary date and on or before the fourth anniversary of the applicable funding date
Debt instrument final exit fee payment percentage						6.50%
Amended and Restated Loan and Security Agreement | Term Loan A | Loan Prepayment After First Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						4.00%
Amended and Restated Loan and Security Agreement | Term Loan A | Loan Prepayment After Second Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						3.00%
Amended and Restated Loan and Security Agreement | Term Loan A | Loan Prepayment After Third Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						1.50%
Amended and Restated Loan and Security Agreement | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 45,000,000
Debt instrument, possible borrowing date						Oct. 14, 2019
Current borrowing capacity									$ 45,000,000
Debt instrument, interest only payments period						36 months through June 1, 2021
Debt instrument, prepayment terms						Under the Term B Loan, the Company will be obligated to pay a prepayment fee equal to (a) 4.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made on or before the first anniversary of the applicable funding date of the Term Loan, (b) 3.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after the first anniversary date and on or before the second anniversary of the applicable funding date, (c) 1.50% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after second anniversary date and on or before the third anniversary of the applicable funding date, and (d) 0.0% of the outstanding principal balance of the applicable Term B Loan if prepayment is made after the third anniversary date of the funding date and prior to the maturity date
Debt instrument final exit fee payment percentage						2.00%
Amended and Restated Loan and Security Agreement | Term Loan B | Loan Prepayment After First Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						3.00%
Amended and Restated Loan and Security Agreement | Term Loan B | Loan Prepayment After Second Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						1.50%
Amended and Restated Loan and Security Agreement | Term Loan B | Loan Prepayment After Third Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						0.00%
Amended and Restated Loan and Security Agreement | Term Loan B | Loan Prepayment After First Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage						4.00%
Amended Restated Loan Agreement | Term Loan B
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 75,000,000
Proceeds from long-term debt	$ 75,000,000

Term Loan - Schedule of Term Lo

Term Loan - Schedule of Term Loans and Unamortized Issuance Cost Balance (Details) - Term Loans - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal Amount	$ 155,000	$ 80,000
Exit Fee	6,700	5,200
Less unamortized issuance cost	6,683	5,981
Total long-term debt, net of debt issuance cost	$ 155,017	$ 79,219

Term Loan - Schedule of Future

Term Loan - Schedule of Future Principal Payments for Term Loans (Details) - Term Loans - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
2020	$ 0
2021	45,208
2022	77,500
2023	32,292
Term Loan	$ 155,000	$ 80,000

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	$ 16,265	$ 14,159
Less accumulated depreciation and amortization	13,269	12,714
Property and equipment, net	2,996	1,445
Computer equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	3,031	2,414
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	5,049	5,025
Office furniture
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	1,993	1,331
Office equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	418	286
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	5,656	$ 5,103
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross, Total	$ 118

Leases - Additional Information

Leases - Additional Information (Details)	Oct. 15, 2019USD ($)ft²	Dec. 31, 2019USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Jan. 01, 2019USD ($)
Lessee Lease Description [Line Items]
Operating lease right-of-use asset		$ 9,068,000			$ 1,500,000
Operating lease liability		$ 10,138,000			$ 1,700,000
Weighted-average remaining lease term		2 years 9 months 18 days
Weighted average incremental borrowing rate		9.60%
Cash paid for amounts included in the measurement of lease liabilities		$ 2,400,000
Operating lease, expense		3,400,000
Total rent expense		$ 3,400,000	$ 600,000	$ 500,000
Irving, Texas
Lessee Lease Description [Line Items]
Operating lease, existence of option to extend		true
Operating lease, option to extend		extend the lease terms through October 31, 2022
Lease expiration date		Oct. 31, 2022
Irving, Texas | Maximum
Lessee Lease Description [Line Items]
Operating lease, renewal Term		6 months
Irving, Texas | Office And Laboratory Space
Lessee Lease Description [Line Items]
Area of real estate property | ft²		34,890
Plano, Texas
Lessee Lease Description [Line Items]
Operating lease, existence of option to extend		true
Operating lease, option to extend		through April 30, 2022
Lease expiration date		Apr. 30, 2022
Operating lease, renewal Term		3 months
Plano, Texas | Office And Laboratory Space | 2019 Lease Agreement
Lessee Lease Description [Line Items]
Area of real estate property | ft²	327,400
Lease initial term	16 years
Lessor, operating lease, existence of option to extend	true
Renewal lease term, option one	two consecutive five-year renewal periods
Renewal lease term, option two	one ten-year renewal period
Operating lease right-of-use asset	$ 0
Operating lease liability	$ 0
Plano, Texas | Office Space
Lessee Lease Description [Line Items]
Area of real estate property | ft²		122,000

Leases - Summary of Supplementa

Leases - Summary of Supplemental Balance Sheet Information Related to Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Assets And Liabilities Lessee [Abstract]
Non-current right-of-use assets	$ 9,068	$ 1,500
Current lease liabilities	3,156
Non-current lease liabilities	$ 6,982

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Leases [Abstract]
2020	$ 3,994
2021	4,142
2022	3,500
Total lease payments	11,636
Less: Imputed interest	1,498
Present value of lease liabilities	$ 10,138	$ 1,700

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Federal statutory tax rate		21.00%	21.00%	35.00%
Reduction in deferred tax assets	$ 53.1
Increase in valuation allowance		$ 98.5	$ 27.2
Federal accumulated net operating losses		457.2
Federal accumulated net operating losses, annual limitation		$ 0.3
Operating loss carry forwards limit percentage		80.00%
Federal research and development tax credit carryforwards		$ 8.9
Federal orphan drug tax credit carryforwards		$ 45.6
Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Examination of U.S. income tax returns, year		2013 2014 2015
Examination of U.S. income tax returns, completed year		2009 2011 2012 2013 2014 2015
Between Fiscal Year 2023 and 2038
Income Tax Disclosure [Line Items]
Federal accumulated net operating losses		$ 120.4
Fiscal Year After 2038
Income Tax Disclosure [Line Items]
Federal accumulated net operating losses		$ 336.8
Earliest Tax Year
Income Tax Disclosure [Line Items]
Tax credit carryforwards expiration year		2024
Latest Tax Year
Income Tax Disclosure [Line Items]
Tax credit carryforwards expiration year		2039

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Effective Income Tax Rate from Continuing Operations to Federal Statutory Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal income taxes	21.00%	21.00%	35.00%
Stock-based compensation	5.00%	1.00%
Change in valuation allowance	(34.00%)	(34.00%)	48.00%
2017 Tax Act			(111.00%)
Federal and state tax credits	8.00%	12.00%	28.00%
Recorded federal income tax benefit (provision)	0.00%	0.00%	0.00%

Income Taxes - Significant Comp

Income Taxes - Significant Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Deferred revenue	$ 1,976	$ 47,432
Net operating loss	96,194	45,011
Federal and state tax credits	54,559	30,739
Intellectual property	67,384
Stock-based compensation	7,741	4,072
Other	2,684	641
Deferred tax assets before valuation allowance	230,538	127,895
Less: Valuation allowance	(226,261)	(127,752)
Net deferred income tax assets	4,277	143
Deferred tax liabilities:
Deferred purchase price	(1,972)
Right-of-use assets	(1,908)
Other	(397)	(143)
Net deferred tax assets (liabilities)	$ 0	$ 0

Patents - Additional Informatio

Patents - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Loss Contingency [Abstract]
Patent matters outstanding	0	0	0

Licenses - Additional Informati

Licenses - Additional Information (Details) - USD ($) $ in Millions	Feb. 28, 2019	Dec. 31, 2019
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.
2009 Method of Use License Agreement
License Agreements [Line Items]
Milestone fee paid	$ 0.1
Minimum
License Agreements [Line Items]
Term of agreements		15 years
Maximum
License Agreements [Line Items]
Term of agreements		20 years

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Undesignated Preferred Stock
Class of Stock [Line Items]
Convertible preferred stock	100,000,000
Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options to purchase shares outstanding	4,038,949	3,320,571
Unrecognized compensation expense	$ 72,400
Stock options , vested or expected to vest	4,038,949
Stock Option, Weighted-average exercise price	$ 41.24
Exercisable Stock, Weighted-average outstanding	7 years 3 days
Risk free interest rate, Minimum	1.35%
Risk free interest rate, Maximum	2.67%
Total intrinsic value of outstanding options	$ 659,300	$ 115,800	$ 28,600
Total intrinsic value of exercisable options	$ 305,000	$ 56,900	$ 11,500
Exercise of options, shares	707,849	137,352	59,112
Total intrinsic value of options exercised	$ 79,400	$ 4,500	$ 900
Exercise of options	$ 13,445	$ 1,885	$ 660
Unrecognized compensation expense, recognition period	3 years 2 months 4 days
Restricted Stock Unit (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of RSU’s granted	$ 3,600
Performance-based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance-based stock options outstanding and unvested	50,000
Unrecognized compensation expense	$ 2,300
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average years, vested and expected to vest	7 years 11 months 1 day
LTIP Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock available for future grant	2,385,592
LTIP Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock outstanding	50,000

Stock-Based Compensation - Comm

Stock-Based Compensation - Common Stock Reserved for Issuance (Details)	Dec. 31, 2019shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance	6,474,541
Outstanding common stock options under the LTIP Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance	4,023,276
Outstanding common stock options under standalone option agreements
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance	15,673
Issued and unvested restricted stock units under the LTIP Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance	50,000
Common stock available for future grant under the LTIP Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance	2,385,592

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Stock Units (Details)	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value - Beginning balance	$ 38.14
Weighted-Average Grant Date Fair Value - Ending balance	$ 69.76
Restricted Stock Unit (RSUs)
Number Performance Based RSUs
Number Performance Based RSUs, Granted | shares	50,000
Number Performance Based RSUs – Ending balance | shares	50,000
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Granted	$ 72.70
Weighted-Average Grant Date Fair Value - Ending balance	$ 72.70

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Time Based and Performance-Based Stock Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 26,381	$ 10,550	$ 6,530
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	8,692	3,943	2,409
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 17,689	$ 6,607	$ 4,121

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Options, Abstract
Number of Options, Outstanding - Beginning balance	3,320,571
Number of Options, Granted	1,702,533
Number of Options, Exercised	(707,849)	(137,352)	(59,112)
Number of Options, Forfeited	(276,306)
Number of Options, Outstanding - Ending balance	4,038,949	3,320,571
Number of Options, Exercisable	1,701,135
Weighted Average Price, Abstract
Weighted-Average Price, Outstanding - Beginning balance	$ 21.20
Weighted-Average Price, Granted	69.76
Weighted-Average Price, Exercised	18.99
Weighted-Average Price, Forfeited	34.42
Weighted-Average Price, Outstanding - Ending balance	41.24	$ 21.20
Weighted-Average Price, Exercisable	$ 25.12

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted Average Assumptions in Black-Scholes Pricing Model (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Dividend yield	0.00%	0.00%	0.00%
Volatility	73.73%	72.77%	75.14%
Risk-free interest rate	2.18%	2.79%	2.19%
Expected term of options (in years)	6 years 2 months 23 days	6 years 4 months 6 days	6 years 4 months 13 days
Weighted average grant date fair value	$ 69.76	$ 38.14	$ 25

Net Loss per Share - Computatio

Net Loss 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, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator
Net loss	$ (186,942)	$ (39,694)	$ (34,380)	$ (29,154)	$ (25,582)	$ (30,835)	$ (28,211)	$ 4,082	$ (290,170)	$ (80,546)	$ (47,671)
Denominator
Weighted-average number of common shares used in net loss per share – basic									30,414,203	27,701,783	23,933,309
Weighted-average number of common shares used in net loss per share – diluted									30,414,203	27,701,783	23,933,309
Net loss per share – basic									$ (9.54)	$ (2.91)	$ (1.99)
Net loss per share – diluted									$ (9.54)	$ (2.91)	$ (1.99)

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Weighted average anti-dilutive shares excludes from computation of earnings per share	4,088,949	3,320,571	3,251,696

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Total collaboration revenue	$ 2,672		$ 8,242		$ 7,833		$ 7,770		$ 8,451	$ 5,175	$ 7,571	$ 32,392	$ 26,517	$ 53,589	$ 48,058
Total expenses	187,103	[1]	46,820	[1]	41,492	[1]	36,322	[1]	33,373	34,735	34,223	28,136	311,737	130,467	94,970
Total other income (expense)	(2,563)		(1,078)		(701)		(600)		(649)	(1,266)	(1,553)	(174)	(4,942)	(3,642)	(756)
Provision for taxes on income	(52)		38		20		2		11	9	6		8	26	3
Net loss	$ (186,942)		$ (39,694)		$ (34,380)		$ (29,154)		$ (25,582)	$ (30,835)	$ (28,211)	$ 4,082	$ (290,170)	$ (80,546)	$ (47,671)
Net loss per share—basic and diluted	$ (5.91)		$ (1.32)		$ (1.14)		$ (0.98)						$ (9.54)	$ (2.91)	$ (1.99)
Net income (loss) per share – basic									$ (0.86)	$ (1.07)	$ (1.08)	$ 0.16
Net income (loss) per share – diluted									$ (0.86)	$ (1.07)	$ (1.08)	$ 0.15
[1]	Total expenses in the fourth quarter includes $124.4 million for the reacquired license rights from AbbVie.

Selected Quarterly Financial _4

Selected Quarterly Financial Data (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reacquired license rights		$ 124,398
AbbVie
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reacquired license rights	$ 124,400

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - $ / shares	Jan. 02, 2020	Dec. 31, 2019
Subsequent Event [Line Items]
Number of aggregate options granted		1,702,533
Weighted-Average Price, Granted		$ 69.76
Subsequent Event
Subsequent Event [Line Items]
Number of aggregate options granted	841,765
Weighted-Average Price, Granted	$ 207.20