Reata Pharmaceuticals (RETA) 10-Q 12 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 07, 2019
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	RETA
Entity Registrant Name	REATA PHARMACEUTICALS INC
Entity Central Index Key	0001358762
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-37785
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 Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Class A Common Stock, Par Value $0.001 Per Share
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Former Address
Document Information [Line Items]
Entity Address, Address Line One	2801 Gateway Drive
Entity Address, Address Line Two	Suite 150
Entity Address, City or Town	Irving
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75063
Common Stock A
Document Information [Line Items]
Entity Common Stock Shares Outstanding		24,765,410
Common Stock B
Document Information [Line Items]
Entity Common Stock Shares Outstanding		5,506,495

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 240,149	$ 337,790
Prepaid expenses and other current assets	6,382	4,483
Total current assets	246,531	342,273
Property and equipment, net	2,859	1,445
Other assets	9,733	1,490
Total assets	259,123	345,208
Liabilities and stockholders’ (deficit) equity
Accounts payable	3,582	4,473
Accrued direct research liabilities	19,848	15,416
Other current liabilities	14,398	4,696
Current portion of long-term debt, net of debt issuance cost	5,313
Current portion of deferred revenue	31,421	31,335
Total current liabilities	74,562	55,920
Other long-term liabilities	6,198	524
Long-term debt, net of current portion and debt issuance cost	74,923	79,219
Deferred revenue, net of current portion	170,863	194,386
Total noncurrent liabilities	251,984	274,129
Commitments and contingencies
Stockholders’ (deficit) equity:
Additional paid-in capital	456,097	435,452
Accumulated deficit	(523,551)	(420,323)
Total stockholders’ (deficit) equity	(67,423)	15,159
Total liabilities and stockholders’ (deficit) equity	259,123	345,208
Common Stock A
Stockholders’ (deficit) equity:
Common stock value	25	24
Total stockholders’ (deficit) equity	25	24
Common Stock B
Stockholders’ (deficit) equity:
Common stock value	6	6
Total stockholders’ (deficit) equity	$ 6	$ 6

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 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	24,525,768	24,000,683
Common stock, shares outstanding	24,525,768	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	5,598,731	5,728,175
Common stock, shares outstanding	5,598,731	5,728,175

Unaudited Consolidated Statemen

Unaudited Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Collaboration revenue
Collaboration revenue	$ 8,242	$ 5,175	$ 23,846	$ 45,137
Expenses
Research and development	32,279	27,144	87,948	71,979
General and administrative	14,283	7,486	36,027	24,802
Depreciation	258	105	659	311
Total expenses	46,820	34,735	124,634	97,092
Other income (expense)
Investment income	1,311	1,094	4,812	1,787
Interest expense	(2,389)	(2,360)	(7,199)	(3,773)
Loss on extinguishment of debt				(1,007)
Other income (expense)			7
Total other income (expense)	(1,078)	(1,266)	(2,380)	(2,993)
Loss before taxes on income	(39,656)	(30,826)	(103,168)	(54,948)
Provision for taxes on income	38	9	60	15
Net loss	$ (39,694)	$ (30,835)	$ (103,228)	$ (54,963)
Net loss per share—basic and diluted	$ (1.32)	$ (1.07)	$ (3.44)	$ (2.03)
Weighted-average number of common shares used in net loss per share basic and diluted	30,110,391	28,704,853	30,004,211	27,022,269
License and milestone
Collaboration revenue
Collaboration revenue	$ 7,898	$ 4,766	$ 23,437	$ 44,452
Other revenue
Collaboration revenue
Collaboration revenue	$ 344	$ 409	$ 409	$ 685

Unaudited Consolidated Statem_2

Unaudited Consolidated Statements of Stockholders' (Deficit) Equity - 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, 2017	$ (146,973)	$ 20	$ 7	$ 190,145	$ (2)	$ (337,143)
Balance, shares at Dec. 31, 2017		19,975,340	6,166,166
Net loss	(54,963)					(54,963)
Compensation expense related to stock options	7,763			7,781		(18)
Exercise of options, value	1,498			1,498
Exercise of options, shares			106,024
Proceeds from payments of shareholder promissory notes	8			6	$ 2
Public offering of common stock, net of offering costs, value	232,847	$ 4		232,843
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		458,625	(458,625)
Adoption of new accounting guidance	(2,634)					(2,634)
Balance, value at Sep. 30, 2018	37,545	$ 24	$ 6	432,273		(394,758)
Balance, shares at Sep. 30, 2018		23,883,965	5,813,565
Balance, value at Jun. 30, 2018	(167,874)	$ 20	$ 6	196,013		(363,913)
Balance, shares at Jun. 30, 2018		20,244,675	5,961,183
Net loss	(30,835)					(30,835)
Compensation expense related to stock options	2,735			2,745		(10)
Exercise of options, value	672			672
Exercise of options, shares			41,672
Public offering of common stock, net of offering costs, value	232,847	$ 4		232,843
Public offering of common stock, net of offering costs, shares		3,450,000
Conversion of common stock Class B to Class A, shares		189,290	(189,290)
Balance, value at Sep. 30, 2018	37,545	$ 24	$ 6	432,273		(394,758)
Balance, shares at Sep. 30, 2018		23,883,965	5,813,565
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
Net loss	(103,228)					(103,228)
Compensation expense related to stock options	14,090			14,090
Exercise of options, value	$ 6,448			6,448
Exercise of options, shares	395,641		395,641
Conversion of common stock Class B to Class A, value	$ 1	$ 1
Conversion of common stock Class B to Class A, shares		525,085	(525,085)
Other shareholder transactions	107			107
Balance, value at Sep. 30, 2019	(67,423)	$ 25	$ 6	456,097		(523,551)
Balance, shares at Sep. 30, 2019		24,525,768	5,598,731
Balance, value at Jun. 30, 2019	(33,473)	$ 24	$ 6	450,354		(483,857)
Balance, shares at Jun. 30, 2019		24,466,407	5,631,527
Net loss	(39,694)					(39,694)
Compensation expense related to stock options	5,380			5,380
Exercise of options, value	363			363
Exercise of options, shares			26,565
Conversion of common stock Class B to Class A, value	1	$ 1
Conversion of common stock Class B to Class A, shares		59,361	(59,361)
Balance, value at Sep. 30, 2019	$ (67,423)	$ 25	$ 6	$ 456,097		$ (523,551)
Balance, shares at Sep. 30, 2019		24,525,768	5,598,731

Unaudited Consolidated Statem_3

Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities
Net loss	$ (103,228)	$ (54,963)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	659	311
Amortization of debt issuance costs	1,017	549
Stock-based compensation expense	14,090	7,783
Loss on extinguishment of debt		1,007
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,899)	(1,304)
Other assets	20	14
Accounts payable	(440)	2,933
Accrued direct research and other current and long-term liabilities	11,442	10,836
Deferred revenue	(23,437)	(13,452)
Net cash used in operating activities	(101,776)	(46,286)
Investing activities
Purchases of property and equipment	(2,420)	(370)
Net cash used in investing activities	(2,420)	(370)
Financing activities
Proceeds from issuance of common stock		232,846
Proceeds from long-term debt		60,000
Payments on deferred issuance costs		(2,289)
Exercise of options	6,448	1,504
Other shareholder transactions	107
Net cash provided by financing activities	6,555	292,061
Net (decrease) increase in cash and cash equivalents	(97,641)	245,405
Cash and cash equivalents at beginning of year	337,790	129,780
Cash and cash equivalents at end of period	240,149	375,185
Supplemental disclosures
Cash paid for interest	6,226	2,715
Purchases of equipment in accounts payable and other current liabilities	145	31
Accrued deferred offering cost		$ 22
Non-cash activity:
Right-of-use assets obtained in exchange for lease obligations	$ 8,262

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 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 rare forms of neurological diseases. The Company’s lead product candidates, bardoxolone methyl (bardoxolone) in CKD and omaveloxolone in neurological diseases, 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. The Company has reported top-line efficacy and safety Year 1 results from its registrational CARDINAL Phase 3 clinical trial of bardoxolone in CKD caused by Alport syndrome. Alport syndrome is a rare and serious hereditary disease with no approved therapy. The trial met its primary and key secondary Year 1 endpoints. CARDINAL demonstrated a statistically significant change in the estimated glomerular filtration rate (eGFR) relative to placebo after 48 weeks of treatment and in retained eGFR, which is the change in eGFR after 48 weeks of treatment and a four-week withdrawal period. Subject to discussions with regulatory authorities, the Company plans to proceed with the submission of regulatory filings for marketing approval in the United States and internationally. The Company has reported top-line efficacy and safety results from its registrational part 2 portion of the MOXIe Phase 2 trial of omaveloxolone in Friedreich’s ataxia (FA). FA is a rare, inherited, debilitating, and degenerative neuromuscular disorder with no approved therapy. The trial demonstrated statistically significant evidence of efficacy for its primary endpoint of change in the modified Friedreich’s Ataxia Rating Scale (mFARS) relative to placebo after 48 weeks of treatment. Subject to discussions with regulatory authorities, the Company plans to proceed with the submission of regulatory filings for marketing approval in the United States and internationally. The Company is also conducting two additional registrational trials: FALCON, studying bardoxolone in patients with autosomal dominant polycystic kidney disease (ADPKD), and CATALYST, studying bardoxolone in patients with a rare and serious form of pulmonary arterial hypertension (PAH) caused by connective tissue disease (CTD-PAH). The Company initiated enrollment of FALCON in May 2019, and the Company expects to have top-line data from CATALYST in mid-2020. 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	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019. The consolidated balance sheet at December 31, 2018, has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, refer to the annual consolidated financial statements and footnotes thereto of the Company. The Company’s significant accounting policies are described in Note 2 of Notes to Consolidated Financial Statements included in its Annual Report on Form 10-K for the year ended December 31, 2018 (2018 Annual Report on Form 10-K). During the first quarter of 201 9 , the Company adopted Accounting Standards Update (ASU) No. 201 6-02 , Leases (Topic 842). As a result of the adoption of Topic 842, the Company has updated its Lease s accounting policies. There were no other changes to its significant accounting policies from those disclosed in its 201 8 Annual Report on Form 10-K. Liquidity As of September 30, 2019, the Company had cash and cash equivalents of $240,149,000. 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, the success of which cannot be guaranteed. The Company expects its current cash and its access to additional equity or debt funding will enable it to meet its current obligations through December 31, 2020. See Note 9, Subsequent Events 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 will account 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. Recently Adopted Accounting Pronouncements The Company is an emerging growth company (EGC), as defined in the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies. The Company will remain an EGC until December 31, 2019. In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, amended by ASU 2018-11, Leases (Topic 842): Targeted Improvements As a result of implementing Topic 842, the Company recognized an operating lease right-of-use asset of $1,544,000 and an operating lease liability of $1,659,000 on January 1, 2019, with no impact on its beginning retained earnings, consolidated statements of operations, or cash flows. See Note 5, Leases In July 2018, the FASB issued ASU No. 2018-09, Codification Improvements (ASU 2018-09). This ASU provided various minor codification updates and improvements to address comments that the FASB had received regarding unclear or vague accounting guidance. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that fiscal year. The adoption of this guidance did not have a material impact on our financial position, results of operations or disclosures. In July 2019, the FASB issued ASU No. 2019-07, Codification Updates to SEC Sections . The ASU clarifies or improves the disclosure and presentation requirements of a variety of codification topics by aligning them with the SEC’s regulations, thereby eliminating redundancies and making the codification easier to apply. The guidance is effective upon issuance. the Company’s reported consolidated financial results. Recently Issued Accounting Pronouncements Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements Revenue Recognition Collaborative Arrangements

Collaboration Agreements

Collaboration Agreements	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration Agreements	3. Collaboration Agreements AbbVie In December 2011, the Company entered into a collaboration agreement with AbbVie Inc. (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 Collaboration Agreement include payment to the Company of a nonrefundable, up-front payment of $400,000,000. The Company is also participating with AbbVie on joint steering committees. The up-front payment and the Company’s collaboration on research, development, and commercialization are accounted for as a single unit of accounting. Revenue is being recognized ratably through December 2026, which is the estimated minimum period that is needed to complete the performance obligations under the terms of the Collaboration Agreement. The Company began recognizing revenue related to the up-front payment upon execution of the Collaboration Agreement. During the three months ended September 30, 2019 and 2018, the Company recognized approximately $6,717,000, and during the nine months ended September 30, 2019 and 2018, recognized $19,931,000, as collaboration revenue. As of September 30, 2019, the Company recorded deferred revenue totaling approximately $191,714,000 of which approximately $26,720,000 is reflected as the current portion of deferred revenue. On October 9, 2019, the Company and AbbVie entered into an Amended and Restated License Agreement (the Amended AbbVie Agreement) pursuant to which the Company reacquired the development, manufacturing, and commercialization rights concerning its proprietary Nrf2 activator product platform originally licensed to AbbVie in the License Agreement, dated as of September 21, 2010, which the Company entered into with AbbVie (the License Agreement), and the Collaboration Agreement. See Note 9, Subsequent Events KKC In December 2009, the Company entered a license agreement with Kyowa Kirin Co., Ltd. (KKC) (the KKC Agreement), which granted KKC an exclusive license to develop and commercialize bardoxolone in the licensed territory. The Company received a nonrefundable, up-front license fee of $35,000,000 in 2009 and regulatory milestones totaling $45,000,000 in 2010, 2012, and 2018 and could receive additional regulatory milestones of $52,000,000 and commercial milestones of $140,000,000, as well as 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 licensed territory. 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 KK C A greement. The Company began recognizing revenue related to the up-front payment upon execution of the KKC A greement . During the three months ended September 30, 2019 and 2018 , the Company recognized approximately $ 1,181,000 and $ (2,951,000) , respectively, and during the nine months ended September 30, 2019 and 2018 , recognized $ 3,506,000 and $23,521,000 , respectively , as collaboration revenue. As of September 30, 2019 , the Company recorded deferred revenue totaling approximately $10,570,000 of which approximately $4,701,000 is reflected as the current portion of deferred revenue.

Term Loan

Term Loan	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Term Loan	4. Term Loan On June 14, 2018, the Company entered into an Amended and Restated Loan and Security Agreement (the Restated Loan Agreement) with Oxford Finance LLC and Silicon Valley Bank (collectively, the Lenders), which amended and restated the Loan and Security Agreement entered into among Reata and the Lenders on March 31, 2017, as amended on November 3, 2017 (the Loan Agreement). Under the Restated Loan Agreement, the Term A Loan was increased to $80,000,000, and the Term B Loan availability was increased to $45,000,000, available to be drawn within 30 days, but no later than December 31, 2019, after the achievement of one of two milestones. If the Company is entitled to draw the Term B Loan but does not draw the Term B Loan by December 31, 2019, the Company is obligated to pay a non-utilization fee of $450,000. All outstanding Term Loans will mature on June 1, 2023. Under the Term A Loan, the Company will make interest-only payments for 24 months through June 1, 2020; however, if the Company draws the Term B Loan, the Company will make interest-only payments for 36 months through June 1, 2021. The interest-only payment period will be followed by 36 equal monthly payments, or 24 equal monthly payments if the Company draws the Term B Loan, of principal and interest payments. The Term Loans will bear interest at a floating per annum rate calculated as 7.79% plus the greater of the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue or 1.91%, with a minimum rate of 9.7% and maximum rate of 12.29%. 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 the 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. 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 4.0% 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. As of September 30, 2019, the Term A Loan has an effective interest rate of 10.71% before debt issuance costs and final exit fee and 13.26% including debt issuance costs and final exit fee. The Company was in compliance with all covenants under the Restated Loan Agreement as of September 30, 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 Restated Loan Agreement are secured by substantially all of its current and future assets, including its owned intellectual property. Term A Loan and unamortized issuance cost balance are as follows: As of September 30, 2019 As of December 31, 2018 (in thousands) Current portion of long-term debt 1 $ 6,667 $ — Less current portion of unamortized issuance cost 1,354 — Total current portion of long-term debt, net of debt issuance cost 5,313 — Principal Amount 80,000 80,000 Exit Fee 5,200 5,200 Less long-term unamortized issuance cost 3,610 5,981 Less current portion of long-term debt 6,667 $ — Total long-term debt, net of current portion and debt issuance cost $ 74,923 $ 79,219 1 Current portion of principal payments reflects the interest-only payment period under the Term A Loan. If the Company draws the Term B Loan, the interest-only period will extend through June 1, 2021, and the current portion will be $0 until July 1, 2020. The future principal payments by fiscal year for the Company’s Term A Loan: As of September 30, 2019 (in thousands) 2019 (remaining three months) $ — 2020 15,555 2021 26,667 2022 26,667 2023 11,111 $ 80,000 On October 9, 2019, the Company entered into the First Amendment to Amended and Restated Loan and Security Agreement (the Amendment) with the Lenders, which amended the Restated Loan Agreement. See Note 9, Subsequent Events

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	5. Leases The Company has offices located in Irving, Texas, where it leases approximately 34,890 square feet of office and laboratory space, and in Plano, Texas, where it leases approximately 122,000 square feet of office space. The Company’s leases have remaining contractual terms of up to approximately 33 months, which includes the options to extend the leases for up to one year. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. At September 30, 2019, the weighted average incremental borrowing rate and the weighted average remaining lease term for the operating leases held by the Company were 8.3% and 2.5 years, respectively. During the nine months ended September 30, 2019, cash paid for amounts included for the measurement of lease liabilities was $1,667,000. During the three and nine months ended September 30, 2019 the Company recorded operating lease expense of $911,000 and $2,489,000, respectively. 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 in 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 September 30, 2019 (in thousands) Non-current right-of-use assets Other assets $ 8,262 Current lease liabilities Other current liabilities 2,941 Non-current lease liabilities Other long-term liabilities 6,198 Maturities of lease liabilities by fiscal year for the Company’s operating leases: As of September 30, 2019 (in thousands) 2019 (remaining three months) $ 718 2020 3,999 2021 4,090 2022 1,178 Total lease payments 9,985 Less: Imputed interest (846 ) Present value of lease liabilities $ 9,139 On October 15, 2019, the Company entered into a lease agreement, relating to the lease of approximately 327,400 square feet of office and laboratory space located in Plano, Texas (Lease Agreement). See Note 9, Subsequent Events.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes The Company’s effective tax rate varies with the statutory rate due primarily to the impact of nondeductible stock-based compensation and the changes in valuation allowance related to certain deferred tax assets generated or utilized in the applicable period. The Company’s deferred tax assets have been fully offset by a valuation allowance at September 30, 2019, and the Company expects to maintain this valuation allowance until there is sufficient evidence that future earnings can be achieved, which is uncertain at this time. The IRS examination team has completed its examination of the Company’s 2013, 2014, and 2015 U.S. tax returns 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 believes that it has accurately reported all amounts in its tax returns and has submitted an administrative protest with the IRS contesting the examination team’s proposed adjustments. The Company intends to vigorously defend its reported positions and believes the ultimate resolution of the adjustments proposed by the IRS examination team will not have a material adverse effect on its consolidated financial statements.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	7. Stock-Based Compensation Stock Options The following table summarizes stock-based compensation expense reflected in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) Research and development $ 1,885 $ 988 $ 5,235 $ 2,924 General and administrative 3,495 1,757 8,855 4,859 $ 5,380 $ 2,745 $ 14,090 $ 7,783 The following table summarizes stock option activity as of September 30, 2019, and changes during the nine months ended September 30, 2019, under the Second Amended and Restated Long Term Incentive Plan and standalone option agreements: Number of Options Weighted-Average Exercise Price Outstanding at January 1, 2019 3,320,571 21.20 Granted 1,624,133 64.94 Exercised (395,641 ) 16.30 Forfeited (276,306 ) 34.42 Outstanding at September 30, 2019 4,272,757 37.51 Exercisable at September 30, 2019 1,743,886 22.56 The total intrinsic value of all outstanding options and exercisable options at September 30, 2019 was $184,473,000 and $100,782,000, respectively. Restricted Stock Units (RSUs) As of September 30, 2019, the Company granted 50,000 RSUs under a Restricted Stock Unit Agreement. As the awards granted are performance-based, there was $3,635,000 of unrecognized compensation expense related to these RSUs. Number Performance Based RSUs Weighted-Average Grant Date Fair Value Outstanding at January 1, 2019 — — Granted 50,000 72.70 Vested — — Forfeited — — Outstanding at September 30, 2019 50,000 72.70

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	8. Net Loss per Share The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands, except share and per share data) Numerator Net loss $ (39,694 ) $ (30,835 ) $ (103,228 ) $ (54,963 ) Denominator Weighted-average number of common shares used in net loss per share – basic 30,110,391 28,704,853 30,004,211 27,022,269 Dilutive potential common shares — — — — Weighted-average number of common shares used in net loss per share – diluted 30,110,391 28,704,853 30,004,211 27,022,269 Net loss per share – basic $ (1.32 ) $ (1.07 ) $ (3.44 ) $ (2.03 ) Net loss per share – diluted $ (1.32 ) $ (1.07 ) $ (3.44 ) $ (2.03 ) 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 4,272,757 and 3,337,262 shares for the nine months ended September 30, 2019 and 2018, respectively.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	9. Subsequent Events On October 9, 2019, the Company and AbbVie entered into the Amended AbbVie Amended AbbVie Amended AbbVie On October 9, 2019, the Company entered into the Amendment availability period was increased from within 30 days to 60 days after the achievement of the one of two milestones. As one of the milestones was achieved on October 14, 2019, the availability period will end on December 13, 2019 Under the Restated Loan Agreement, the Company has significantly increased its current obligations, but the Company believes that its current cash, along with its access to additional equity or debt funding, will enable the Company to meet its current obligations through December 31, 2020. On October 15, 2019, the Company entered into the Lease Agreement, relating to the lease of approximately 327,400 square feet of office and laboratory space located in Plano, Texas. The term of the Lease is estimated to commence mid-2022, when construction is completed, and continue for 16 years, with up to 10 years of extension at the Company’s option. The initial annual base rent will be determined based on the project cost, subject to an initial annual cap of approximately $13,344,000, which may increase in certain circumstances. Beginning in the third lease year, the base rent will increase 1.95% per annum each year. In addition to the annual base rent, the Company will pay for taxes, insurance, utilities, operating expenses, assessments under private covenants, maintenance and repairs, certain capital repairs and replacements, and building management fees.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the year ending December 31, 2019. The consolidated balance sheet at December 31, 2018, has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by U.S. GAAP for complete financial statements. For further information, refer to the annual consolidated financial statements and footnotes thereto of the Company. The Company’s significant accounting policies are described in Note 2 of Notes to Consolidated Financial Statements included in its Annual Report on Form 10-K for the year ended December 31, 2018 (2018 Annual Report on Form 10-K). During the first quarter of 201 9 , the Company adopted Accounting Standards Update (ASU) No. 201 6-02 , Leases (Topic 842). As a result of the adoption of Topic 842, the Company has updated its Lease s accounting policies. There were no other changes to its significant accounting policies from those disclosed in its 201 8 Annual Report on Form 10-K.
Liquidity	Liquidity As of September 30, 2019, the Company had cash and cash equivalents of $240,149,000. 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, the success of which cannot be guaranteed. The Company expects its current cash and its access to additional equity or debt funding will enable it to meet its current obligations through December 31, 2020. See Note 9, Subsequent Events
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 will account 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.
Recent Accounting Pronouncements	Recently Adopted Accounting Pronouncements The Company is an emerging growth company (EGC), as defined in the JOBS Act. Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected not to avail itself of this exemption from new or revised accounting standards, and, therefore, will be subject to the same new or revised accounting standards as public companies that are not emerging growth companies. The Company will remain an EGC until December 31, 2019. In February 2016, the Financial Accounting Standards Board (FASB) issued Topic 842, amended by ASU 2018-11, Leases (Topic 842): Targeted Improvements As a result of implementing Topic 842, the Company recognized an operating lease right-of-use asset of $1,544,000 and an operating lease liability of $1,659,000 on January 1, 2019, with no impact on its beginning retained earnings, consolidated statements of operations, or cash flows. See Note 5, Leases In July 2018, the FASB issued ASU No. 2018-09, Codification Improvements (ASU 2018-09). This ASU provided various minor codification updates and improvements to address comments that the FASB had received regarding unclear or vague accounting guidance. The guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that fiscal year. The adoption of this guidance did not have a material impact on our financial position, results of operations or disclosures. In July 2019, the FASB issued ASU No. 2019-07, Codification Updates to SEC Sections . The ASU clarifies or improves the disclosure and presentation requirements of a variety of codification topics by aligning them with the SEC’s regulations, thereby eliminating redundancies and making the codification easier to apply. The guidance is effective upon issuance. the Company’s reported consolidated financial results. Recently Issued Accounting Pronouncements Not Yet Adopted In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements Revenue Recognition Collaborative Arrangements

Term Loan (Tables)

Term Loan (Tables) - Term Loan A	9 Months Ended
	Sep. 30, 2019
Debt Instrument [Line Items]
Schedule of Term Loan and Unamortized Issuance Cost Balance	Term A Loan and unamortized issuance cost balance are as follows: As of September 30, 2019 As of December 31, 2018 (in thousands) Current portion of long-term debt 1 $ 6,667 $ — Less current portion of unamortized issuance cost 1,354 — Total current portion of long-term debt, net of debt issuance cost 5,313 — Principal Amount 80,000 80,000 Exit Fee 5,200 5,200 Less long-term unamortized issuance cost 3,610 5,981 Less current portion of long-term debt 6,667 $ — Total long-term debt, net of current portion and debt issuance cost $ 74,923 $ 79,219 1 Current portion of principal payments reflects the interest-only payment period under the Term A Loan. If the Company draws the Term B Loan, the interest-only period will extend through June 1, 2021, and the current portion will be $0 until July 1, 2020.
Schedule of Future Principal Payments by Fiscal Year for Term A Loan	The future principal payments by fiscal year for the Company’s Term A Loan: As of September 30, 2019 (in thousands) 2019 (remaining three months) $ — 2020 15,555 2021 26,667 2022 26,667 2023 11,111 $ 80,000

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2019 (in thousands) Non-current right-of-use assets Other assets $ 8,262 Current lease liabilities Other current liabilities 2,941 Non-current lease liabilities Other long-term liabilities 6,198
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities by fiscal year for the Company’s operating leases: As of September 30, 2019 (in thousands) 2019 (remaining three months) $ 718 2020 3,999 2021 4,090 2022 1,178 Total lease payments 9,985 Less: Imputed interest (846 ) Present value of lease liabilities $ 9,139

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Based Compensation Expense	The following table summarizes stock-based compensation expense reflected in the consolidated statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) Research and development $ 1,885 $ 988 $ 5,235 $ 2,924 General and administrative 3,495 1,757 8,855 4,859 $ 5,380 $ 2,745 $ 14,090 $ 7,783
Summary of Stock Option Activity	The following table summarizes stock option activity as of September 30, 2019, and changes during the nine months ended September 30, 2019, under the Second Amended and Restated Long Term Incentive Plan and standalone option agreements: Number of Options Weighted-Average Exercise Price Outstanding at January 1, 2019 3,320,571 21.20 Granted 1,624,133 64.94 Exercised (395,641 ) 16.30 Forfeited (276,306 ) 34.42 Outstanding at September 30, 2019 4,272,757 37.51 Exercisable at September 30, 2019 1,743,886 22.56
Summary of Restricted Stock Units	Number Performance Based RSUs Weighted-Average Grant Date Fair Value Outstanding at January 1, 2019 — — Granted 50,000 72.70 Vested — — Forfeited — — Outstanding at September 30, 2019 50,000 72.70

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of basic and diluted net loss per share attributable to common stockholders: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands, except share and per share data) Numerator Net loss $ (39,694 ) $ (30,835 ) $ (103,228 ) $ (54,963 ) Denominator Weighted-average number of common shares used in net loss per share – basic 30,110,391 28,704,853 30,004,211 27,022,269 Dilutive potential common shares — — — — Weighted-average number of common shares used in net loss per share – diluted 30,110,391 28,704,853 30,004,211 27,022,269 Net loss per share – basic $ (1.32 ) $ (1.07 ) $ (3.44 ) $ (2.03 ) Net loss per share – diluted $ (1.32 ) $ (1.07 ) $ (3.44 ) $ (2.03 )

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Operating lease, right-of-use asset	$ 8,262,000	$ 1,544,000
Operating lease, liability	9,139,000	$ 1,659,000
Cash and cash equivalents	$ 240,149,000		$ 337,790,000	$ 375,185,000	$ 129,780,000

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Dec. 31, 2011	Dec. 31, 2009	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue			$ 8,242,000	$ 5,175,000	$ 23,846,000	$ 45,137,000
Deferred revenue, current			31,421,000		$ 31,421,000		$ 31,335,000
AbbVie | Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Up-front collaboration payment received	$ 400,000,000
Deferred revenue, expected timing of recognition					2026-12
Collaboration revenue			6,717,000	6,717,000	$ 19,931,000	19,931,000
Deferred revenue			191,714,000		191,714,000
Deferred revenue, current			26,720,000		$ 26,720,000
KKC Agreement | License Agreement Terms
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, expected timing of recognition					2021-12
Collaboration revenue			1,181,000	$ (2,951,000)	$ 3,506,000	$ 23,521,000
Deferred revenue			10,570,000		10,570,000
Deferred revenue, current			4,701,000		4,701,000
Upfront license fee received		$ 35,000,000
Collaboration revenue, total milestone payments received in 2010, 2012, 2018					45,000,000
Collaboration revenue, potential milestone payments			52,000,000		52,000,000
Collaboration revenue, additional potential commercial milestone payments			$ 140,000,000		$ 140,000,000

Term Loan - Additional Informat

Term Loan - Additional Information (Details) - Amended and Restated Loan and Security Agreement - USD ($)	9 Months Ended
	Sep. 30, 2019	Jun. 14, 2018
Debt Instrument [Line Items]
Debt instrument, prepayment terms	The Company has the option to prepay all, but not less than all, of the borrowed amounts, provided that the Company will be obligated to pay a prepayment fee equal to (a) 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 the 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.
Loan Prepayment After First Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage	4.00%
Loan Prepayment After Second Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage	3.00%
Loan Prepayment After Third Anniversary
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage	1.50%
Term Loan A
Debt Instrument [Line Items]
Debt instrument, interest only payments period	24 months through June 1, 2020
Debt instrument final exit fee payment percentage	6.50%
Debt instrument, effective interest rate before debt issuance costs and final exit fee	10.71%
Debt instrument, effective interest rate including debt issuance costs and final exit fee	13.26%
Term Loan A | Achievement of One of Two Milestones
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 80,000,000
Term Loan B
Debt Instrument [Line Items]
Period to borrow funds after achievement of milestone	30 days
Debt instrument, possible borrowing date	Dec. 31, 2019
Payment of unused line fee	$ 450,000
Debt instrument, interest only payments period	36 months through June 1, 2021
Debt instrument final exit fee payment percentage	4.00%
Term Loan B | Achievement of One of Two Milestones
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 45,000,000
Term Loans
Debt Instrument [Line Items]
Debt instrument, payment terms	All outstanding Term Loans will mature on June 1, 2023.  Under the Term A Loan, the Company will make interest-only payments for 24 months through June 1, 2020; however, if the Company draws the Term B Loan, the Company will make interest-only payments for 36 months through June 1, 2021.  The interest-only payment period will be followed by 36 equal monthly payments, or 24 equal monthly payments if the Company draws the Term B Loan, 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 U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue or 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%
Term Loans | Minimum
Debt Instrument [Line Items]
Debt instrument, annual interest rate	9.70%
Term Loans | Maximum
Debt Instrument [Line Items]
Debt instrument, annual interest rate	12.29%

Term Loan - Schedule of Term Lo

Term Loan - Schedule of Term Loan and Unamortized Issuance Cost Balance (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total current portion of long-term debt, net of debt issuance cost	$ 5,313
Total long-term debt, net of current portion and debt issuance cost	74,923	$ 79,219
Term Loan A
Debt Instrument [Line Items]
Current portion of long-term debt	6,667
Less current portion of unamortized issuance cost	1,354
Total current portion of long-term debt, net of debt issuance cost	5,313
Principal Amount	80,000	80,000
Exit Fee	5,200	5,200
Less long-term unamortized issuance cost	3,610	5,981
Less current portion of long-term debt	6,667
Total long-term debt, net of current portion and debt issuance cost	$ 74,923	$ 79,219

Term Loan - Schedule of Term _2

Term Loan - Schedule of Term Loan and Unamortized Issuance Cost Balance (Parenthetical) (Details) - Term Loan - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jun. 30, 2020
Debt Instrument [Line Items]
Debt instrument, interest only payments period	the interest-only period will extend through June 1, 2021
Forecast
Debt Instrument [Line Items]
Current portion of long-term debt		$ 0

Term Loan - Schedule of Future

Term Loan - Schedule of Future Principal Payments by Fiscal Year for Term A Loan (Details) - Term Loan A - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
2019 (remaining three months)	$ 0
2020	15,555
2021	26,667
2022	26,667
2023	11,111
Term Loan	$ 80,000	$ 80,000

Leases - Additional Information

Leases - Additional Information (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)ft²	Sep. 30, 2019USD ($)ft²	Oct. 15, 2019ft²
Lessee Lease Description [Line Items]
Contractual term	33 months	33 months
Weighted-average remaining lease term	2 years 6 months	2 years 6 months
Cash paid for amounts included in the measurement of lease liabilities | $		$ 1,667,000
Operating lease, expense | $	$ 911,000	$ 2,489,000
Weighted average incremental borrowing rate	8.30%	8.30%
Office And Laboratory Space
Lessee Lease Description [Line Items]
Area of real estate property	34,890	34,890
Office And Laboratory Space | Subsequent Event
Lessee Lease Description [Line Items]
Area of real estate property			327,400
Contractual term			16 years
Office Space
Lessee Lease Description [Line Items]
Area of real estate property	122,000	122,000

Leases - Summary of Supplementa

Leases - Summary of Supplemental Balance Sheet Information Related to Operating Leases (Details) - USD ($)	Sep. 30, 2019	Jan. 01, 2019
Assets And Liabilities Lessee [Abstract]
Non-current right-of-use assets	$ 8,262,000	$ 1,544,000
Current lease liabilities	2,941,000
Non-current lease liabilities	$ 6,198,000

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($)	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
2019 (remaining three months)	$ 718,000
2020	3,999,000
2021	4,090,000
2022	1,178,000
Total lease payments	9,985,000
Less: Imputed interest	(846,000)
Operating lease, liability	$ 9,139,000	$ 1,659,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019
Internal Revenue Service (IRS)
Income Tax Disclosure [Line Items]
Examination of U.S. income tax returns, year	2013 2014 2015

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 5,380	$ 2,745	$ 14,090	$ 7,783
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,885	988	5,235	2,924
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 3,495	$ 1,757	$ 8,855	$ 4,859

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activity (Details) - $ / shares	9 Months Ended
	Sep. 30, 2019
Number of Options, Abstract
Number of Options, Outstanding - Beginning balance	3,320,571
Number of Options, Granted	1,624,133
Number of Options, Exercised	(395,641)
Number of Options, Forfeited	(276,306)
Number of Options, Outstanding - Ending balance	4,272,757
Number of Options, Exercisable	1,743,886
Weighted Average Exercise Price, Abstract
Weighted-Average Exercise Price, Outstanding - Beginning balance	$ 21.20
Weighted-Average Exercise Price, Granted	64.94
Weighted-Average Exercise Price, Exercised	16.30
Weighted-Average Exercise Price, Forfeited	34.42
Weighted-Average Exercise Price, Outstanding - Ending balance	37.51
Weighted-Average Exercise Price, Exercisable	$ 22.56

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019USD ($)shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of outstanding options	$ 184,473,000
Total intrinsic value of exercisable options	$ 100,782,000
Restricted Stock Unit (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units granted | shares	50,000
Unrecognized compensation expense	$ 3,635,000

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Units (Details) - Restricted Stock Unit (RSUs)	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Number Performance Based RSUs, Abstract
Number Performance Based RSUs, Granted | shares	50,000
Number Performance Based RSUs – Ending balance | shares	50,000
Weighted-Average Grant Date Fair Value, Abstract
Weighted-Average Grant Date Fair Value, Granted | $ / shares	$ 72.70
Weighted-Average Grant Date Fair Value - Ending balance | $ / shares	$ 72.70

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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator
Net loss	$ (39,694)	$ (30,835)	$ (103,228)	$ (54,963)
Denominator
Weighted-average number of common shares used in net loss per share – basic	30,110,391	28,704,853	30,004,211	27,022,269
Weighted-average number of common shares used in net loss per share – diluted	30,110,391	28,704,853	30,004,211	27,022,269
Net loss per share – basic	$ (1.32)	$ (1.07)	$ (3.44)	$ (2.03)
Net loss per share – diluted	$ (1.32)	$ (1.07)	$ (3.44)	$ (2.03)

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Weighted average anti-dilutive shares excludes from computation of earnings per share	4,272,757	3,337,262

Subsequent Events - Additional

Subsequent Events - Additional Information (Details)	Nov. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 08, 2019USD ($)	Oct. 15, 2019USD ($)ft²	Oct. 09, 2019USD ($)	Sep. 30, 2019ft²
Subsequent Event [Line Items]
Contractual term						33 months
Office And Laboratory Space
Subsequent Event [Line Items]
Area of real estate property | ft²						34,890
Amended and Restated Loan and Security Agreement | Term Loan B
Subsequent Event [Line Items]
Period to borrow funds after achievement of milestone						30 days
Subsequent Event | Office And Laboratory Space
Subsequent Event [Line Items]
Area of real estate property | ft²				327,400
Contractual term				16 years
Extension lease term				10 years
Lessee lease commence date and options to extend				The term of the Lease is estimated to commence mid-2022, when construction is completed, and continue for 16 years, with up to 10 years of extension at the Company’s option.
Operating lease, existence of option to extend				true
Initial annual base rent expense				$ 13,344,000
Percentage of increase in base rent per annum after two years				1.95%
Subsequent Event | Amended and Restated Loan and Security Agreement | Term Loan B
Subsequent Event [Line Items]
Current borrowing capacity					$ 45,000,000
Maximum borrowing capacity					$ 75,000,000
Period to borrow funds after achievement of milestone					60 days
AbbVie | Forecast
Subsequent Event [Line Items]
Cash outflows from acquisitions	$ 105,000,000	$ 150,000,000	$ 75,000,000
Cash outflow from acquisition after prepayments	$ 80,000,000
AbbVie | Subsequent Event
Subsequent Event [Line Items]
Cash outflows from acquisitions					$ 330,000,000
Cash proceeds from equity offering					200,000,000
Prepayment for acquisition after equity offering					$ 25,000,000