AnaptysBio (ANAB) 10-Q 6 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 04, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-37985
Entity Registrant Name	ANAPTYSBIO, INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-3828755
Entity Address, Address Line One	10421 Pacific Center Court
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	362-6295
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	ANAB
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
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 Common Stock, Shares Outstanding		27,277,115
Entity Central Index Key	0001370053
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 165,317	$ 171,017
Receivable from collaborative partners	5,000	0
Short-term investments	197,166	203,210
Prepaid expenses and other current assets	3,572	3,506
Total current assets	371,055	377,733
Property and equipment, net	1,610	1,618
Long-term investments	50,215	54,305
Other long-term assets	1,293	1,481
Restricted cash	60	60
Total assets	424,233	435,197
Current liabilities:
Accounts payable	8,571	16,237
Accrued expenses	13,781	11,052
Notes payable, current portion	0	1,375
Other current liabilities	898	871
Total current liabilities	23,250	29,535
Other long-term liabilities	419	654
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000 shares authorized and no shares, issued or outstanding at March 31, 2020 and December 31, 2019, respectively	0	0
Common stock, $0.001 par value, 500,000 shares authorized, 27,277 shares and 27,255 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	27	27
Additional paid in capital	651,680	648,669
Accumulated other comprehensive income	1,145	338
Accumulated deficit	(252,288)	(244,026)
Total stockholders’ equity	400,564	405,008
Total liabilities and stockholders’ equity	$ 424,233	$ 435,197

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	27,277,115	27,255,000
Common stock, shares outstanding (in shares)	27,277,115	27,255,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Collaboration revenue	$ 15,000	$ 0
Operating expenses:
Research and development	20,968	20,631
General and administrative	4,285	4,141
Total operating expenses	25,253	24,772
Loss from operations	(10,253)	(24,772)
Other income (expense), net:
Interest expense	0	(320)
Interest income	1,897	2,988
Other income, net	94	7
Total other income (expense), net	1,991	2,675
Loss before income taxes	(8,262)	(22,097)
Provision for income taxes	0	19
Net loss	(8,262)	(22,078)
Unrealized income on available for sale securities, net of tax of $0 and $115, respectively	807	427
Comprehensive loss	$ (7,455)	$ (21,651)
Net loss per common share:
Basic and diluted (in dollars per share)	$ (0.30)	$ (0.82)
Weighted-average number of shares outstanding:
Basic and diluted (in shares)	27,264	26,981

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Unrealized income (loss) on available for sale securities, tax	$ 0	$ 115

CONSOLIDATED STATEMENT OF STOCK

CONSOLIDATED STATEMENT OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Stockholders' Equity, Beginning Balance at Dec. 31, 2018	$ 486,365	$ 27	$ 633,251	$ (223)	$ (146,690)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2018		26,922,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	574		574
Shares issued under employee stock plans (in shares)		84,000
Stock-based compensation	2,867		2,867
Comprehensive income (loss), net	427			427
Net loss	(22,078)				(22,078)
Stockholders' Equity, Ending Balance at Mar. 31, 2019	468,155	$ 27	636,692	204	(168,768)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2019		27,006,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2019	405,008	$ 27	648,669	338	(244,026)
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2019		27,255,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans	$ 36		36
Shares issued under employee stock plans (in shares)	22,033	22,000
Stock-based compensation	$ 2,975		2,975
Comprehensive income (loss), net	807			807
Net loss	(8,262)				(8,262)
Stockholders' Equity, Ending Balance at Mar. 31, 2020	$ 400,564	$ 27	$ 651,680	$ 1,145	$ (252,288)
Stockholders' Equity, Ending Balance (in shares) at Mar. 31, 2020		27,277,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (8,262)	$ (22,078)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	140	115
Stock-based compensation	2,975	2,867
Accretion/amortization of investments, net	(8)	(1,028)
Non-cash interest expense	0	164
Changes in operating assets and liabilities:
Receivable from collaborative partners	(5,000)	0
Prepaid expenses and other assets	233	(1,215)
Accounts payable and other liabilities	(5,190)	5,076
Net cash used in operating activities	(15,112)	(16,099)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of investments	(74,013)	(79,763)
Sales and maturities of investments	84,851	89,600
Purchases of property and equipment	(87)	(180)
Net cash provided by investing activities	10,751	9,657
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, upon the exercise of stock options	36	574
Payments on notes payable	(1,375)	(1,875)
Net cash used in financing activities	(1,339)	(1,301)
Net decrease in cash, cash equivalents, and restricted cash	(5,700)	(7,743)
Cash, cash equivalents and restricted cash, beginning of period	171,077	113,656
Cash, cash equivalents and restricted cash, end of period	165,377	105,913
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Interest paid	4	172
Non-cash investing and financing activities:
Amounts accrued for property and equipment	$ 86	$ 233

Description of the Business

Description of the Business	3 Months Ended
	Mar. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business AnaptysBio, Inc. (“we,” “us,” “our,” or the “Company”) was incorporated in the state of Delaware in November 2005. We are a clinical stage biotechnology company developing first-in-class immunology therapeutic product candidates to patients. We are focused on emerging immune control mechanisms applicable to inflammation and immuno-oncology indications. We develop our product candidates using our proprietary antibody discovery technology platform, which is based upon a breakthrough understanding of the natural process of antibody generation, known as somatic hypermutation, or SHM, and replicates this natural process of antibody generation in vitro . We currently generate revenue from milestones achieved under our collaborative research and development arrangements. Since our inception, we have devoted our primary effort to raising capital and research and development activities. Our financial support has been provided primarily from the sale of our common and preferred stock, as well as through funds received under our collaborative research and development agreements. Going forward, as we continue our expansion, we may seek additional financing and/or strategic investments. However, there can be no assurance that any additional financing or strategic investments will be available to us on acceptable terms, if at all. If events or circumstances occur such that we do not obtain additional funding, we will most likely be required to reduce our plans and/or certain discretionary spending, which could have a material adverse effect on our ability to achieve our intended business objectives. Management believes its currently available resources will provide sufficient funds to enable the Company to meet its operating plans for at least the next twelve months. The accompanying consolidated financial statements do not include any adjustments that might be necessary if we are unable to continue as a going concern.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP, have been omitted. The accompanying unaudited consolidated financial statements include all known adjustments necessary for a fair presentation of the results of interim periods as required by U.S. GAAP. These adjustments consist primarily of normal recurring accruals and estimates that impact the carrying value of assets and liabilities. Also, certain reclassifications have been made to 2019 financial information to conform to the current year presentation of prepaid expenses and other assets on the Consolidated Statements of Cash Flows. Operating results for the three months ended March 31, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020 . Interim results are not necessarily indicative of results for a full year, particularly in light of the novel coronavirus pandemic, or COVID-19, and its impact on domestic and global economies. To limit the spread of COVID-19, governments have taken various actions including the issuance of stay-at-home orders and social distancing guidelines, causing some businesses to suspend operations and or experience a reduction in demand for many products from direct or ultimate customers. Accordingly, businesses have adjusted, reduced or suspended operating activities. The effects of the stay-at-home orders and our work-from-home policies may negatively impact productivity, disrupt our business and delay our development programs, regulatory and commercialization timelines, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on our ability to conduct our business in the ordinary course. Our future research and development expenses and general and administrative expenses may vary significantly if we experience an increased impact from COVID-19 on the costs and timing associated with the conduct of our clinical trials and other related business activities. The financial statements should be read in conjunction with our audited financial statements for the year ended December 31, 2019 , included in our Annual Form 10-K. Basis of Consolidation The accompanying consolidated financial statements include us and our wholly-owned Australian subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. We operate in one reportable segment and our functional and reporting currency is the U.S. dollar. Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international markets. Our actual results could differ from these estimates under different assumptions or conditions. Net Loss Per Common Share Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common equivalent shares outstanding for the period, as well as any dilutive effect from outstanding stock options and warrants using the treasury stock method. For each period presented, there is no difference in the number of shares used to calculate basic and diluted net loss per share. The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares): Three Months Ended (in thousands) 2020 2019 Options to purchase common stock 3,021 2,359 Accounting Pronouncements Recently Adopted In December 2019, the Financial Accounting Standards Board “FASB” issued ASU 2019-12, Income Taxes (Topic 740) intended to simplify the accounting for income taxes. The guidance removes the following exceptions: 1) exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items, 2) exception to the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment, 3) exception to the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity method investment becomes a subsidiary and 4) exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. Additionally, the guidance simplifies the accounting for income taxes by: 1) requiring that an entity recognize a franchise tax (or similar tax) that is partially based on income as an income-based tax and account for any incremental amount incurred as a non-income-based tax, 2) requiring that an entity evaluate when a step up in the tax basis of goodwill should be considered part of the business combination in which the book goodwill was originally recognized and when it should be considered a separate transaction, 3) specifying that an entity is not required to allocate the consolidated amount of current and deferred tax expense to a legal entity that is not subject to tax in its separate financial statements (although the entity may elect to do so (on an entity-by-entity basis) for a legal entity that is both not subject to tax and disregarded by the taxing authority), 4) requiring that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date and 5) making minor improvements for income tax accounting related to employee stock ownership plans and investments in qualified affordable housing projects accounted for using the equity method. The guidance will be effective for fiscal years and interim periods beginning after December 15, 2020. Different components of the guidance require retrospective, modified retrospective or prospective adoption, and early adoption is permitted. We early adopted this standard on January 1, 2020 and the adoption of the standard did not have a material impact to our consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) , which changes the accounting treatment for recognizing the impairment of financial assets. Under the new guidance, credit losses for certain types of financial instruments will be estimated based on expected losses. The new guidance also eliminates the other-than-temporary impairment model for available-for-sale (AFS) debt securities. Entities will begin to recognize credit losses on AFS debt securities as allowances rather than as reductions in the carrying value of the securities. Impairment that is not credit-related impairment will continue to be recognized in other comprehensive income and entities will no longer consider the length of time a security has been in an unrealized loss position when determining whether a credit loss exists. ASU 2016-13 becomes effective for annual and interim periods beginning after December 15, 2019. We adopted this standard prospectively on January 1, 2020 and the adoption of the standard did not have a material impact to our consolidated financial statements as credit losses are not expected to be significant based on historical trends, the financial condition of our investments and external market factors. We will continue to actively monitor the impact of the recent coronavirus (COVID-19) pandemic on expected credit losses.

Balance Sheet Accounts and Supp

Balance Sheet Accounts and Supplemental Disclosures	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Accounts and Supplemental Disclosures	Balance Sheet Accounts and Supplemental Disclosures Property and Equipment Property and equipment consist of the following: (in thousands) March 31, 2020 December 31, 2019 Laboratory equipment $ 5,018 $ 4,911 Office furniture and equipment 820 811 Leasehold improvements 575 575 Property and equipment, gross 6,413 6,297 Less: accumulated depreciation and amortization (4,803 ) (4,679 ) Total property and equipment, net $ 1,610 $ 1,618 Accrued Expenses Accrued expenses consist of the following: (in thousands) March 31, 2020 December 31, 2019 Accrued compensation and related expenses $ 1,363 $ 2,152 Accrued professional fees 494 435 Accrued research, development and manufacturing expenses 11,689 8,196 Other 235 269 Total accrued expenses $ 13,781 $ 11,052

Collaborative Research and Deve

Collaborative Research and Development Agreements	3 Months Ended
	Mar. 31, 2020
Revenue Recognition [Abstract]
Collaborative Research and Development Agreements	Collaborative Research and Development Agreements TESARO Collaboration In March 2014, we entered into a Collaboration and Exclusive License Agreement, or the TESARO Agreement, with TESARO, Inc. and TESARO Development, Inc., or collectively, TESARO, an oncology-focused biopharmaceutical company now a part of GlaxoSmithKline. Under the terms of the agreement, we agreed to perform certain discovery and early preclinical development of therapeutic antibodies with the goal of generating immunotherapy antibodies for subsequent preclinical, clinical, regulatory and commercial development to be performed by TESARO. Under the terms of the agreement, TESARO paid an upfront license fee of $17.0 million in March 2014 and agreed to provide funding to us for research and development services related to antibody discovery programs for three specific targets. In November 2014, we and TESARO entered into Amendment No. 1 to the Agreement to add an antibody discovery program against an undisclosed four th target for an upfront license fee of $2.0 million . For each development program, we are eligible to receive milestone payments of up to $18.0 million if certain preclinical and clinical trial events are achieved by TESARO, up to an additional $90.0 million if certain U.S. and European regulatory submissions and approvals in multiple indications are achieved, and up to an additional $165.0 million upon the achievement of specified levels of annual worldwide net sales. We will also be eligible to receive tiered single-digit royalties related to worldwide net sales of products developed under the collaboration. Unless earlier terminated by either party upon specified circumstances, the agreement will terminate, with respect to each specific developed product, upon the latter of the 12 th anniversary of the first commercial sale of the product or the expiration of the last to expire of any patent. Prior to the adoption of ASC 606, Revenue from Contracts with Customers , we determined that the upfront license fees and research funding under the agreement, as amended, should be accounted for as a single unit of accounting and that the upfront license fees should be deferred and recognized as revenue over the same period that the research and development services are performed. In December 2015, we determined that the research and development services would be extended through December 31, 2016. As a result, the period over which the unrecognized license fees and milestones were recognized was extended through December 31, 2016, and have since been recognized in full. We assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, TESARO, is a customer. We identified the following material promises under the TESARO Agreement: (1) the licenses under certain patent rights relating to six discovery programs (four targets) and transfer of certain development and regulatory information, (2) R&D services and (3) Joint Steering Committee meetings. We considered the research and discovery capabilities of TESARO for these specific programs, TESARO’s inability to sub-license, and the fact that the discovery and optimization of these antibodies is proprietary and could not, at the time of the contract inception, be provided by other vendors, to conclude that the license does not have stand-alone functionality and is therefore not distinct. Additionally, we determined that the steering committee participation would not have been provided without the R&D services and license agreement. Based on these assessments, we identified all services to be interrelated, and therefore concluded that the promises should be combined into a single performance obligation at the inception of the arrangement. As of March 31, 2020 , the transaction price includes the upfront payment, research reimbursement revenue, and milestones earned to date, which are allocated in their entirety to the single performance obligation. We earned and recognized two clinical milestones for $15.0 million during the three months ended March 31, 2020 . No other future clinical or regulatory milestones have been included in the transaction price, as all milestone amounts were subject to the revenue constraint. As part of the constraint evaluation, we considered numerous factors including the fact that the receipt of milestones is outside of our control and contingent upon success in future clinical trials, an outcome that is difficult to predict, and the licensees’ efforts. Any consideration related to sales-based milestones, including royalties, will be recognized when the related sales occur as they were determined to relate predominantly to the IP license granted to TESARO and therefore have also been excluded from the transaction price. We will re-evaluate the variable transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Milestones recognized through March 31, 2020 under the TESARO Agreement are as follows: Anti-PD-1 Anti-TIM-3 Anti-LAG-3 Milestone Event Amount Quarter Recognized Amount Quarter Recognized Amount Quarter Recognized Initiated in vivo toxicology studies using good laboratory practices (GLPs) $1.0M Q2'15 $1.0M Q4'15 $1.0M Q3'16 IND clearance from the FDA $4.0M Q1'16 $4.0M Q2'16 $4.0M Q2'17 Phase 2 clinical trial initiation $3.0M Q2'17 $3.0M Q4'17 $3.0M Q4'19 Phase 3 clinical trial initiation - first indication $5.0M Q3'18 — — — — Phase 3 clinical trial initiation - second indication $5.0M Q2'19 — — — — Filing of the first NDA - first indication $10.0M Q1'20 — — — — Filing of the first MAA - first indication $5.0M Q1'20 — — — — Milestones achieved during the discovery period were recognized as revenue pro-rata through December 31, 2016. Milestones achieved during fiscal 2017 were recognized as revenue in the period earned, while milestones after December 31, 2017 are recognized upon determination that a significant reversal of revenue would not be probable. Cash is generally received within 30 days of milestone achievement. We recognized $15.0 million and $0.0 million in revenue under this agreement during the three months ended March 31, 2020 and 2019 , respectively. Antibody Generation Agreement with Celgene Corporation In December 2011, we entered into a license and collaboration agreement with Celgene, now a part of Bristol-Myers Squibb, or the Celgene Agreement, to develop therapeutic antibodies against multiple targets. We granted Celgene the option to obtain worldwide commercial rights to antibodies generated against each of the targets under the agreement, which option was triggered on a target-by-target basis by our delivery of antibodies meeting certain pre-specified parameters pertaining to each target under the agreement. The agreement provided for an upfront payment of $6.0 million from Celgene, which we received in 2011 and recognized through 2014, milestone payments of up to $53.0 million per target, low single-digit royalties on net sales of antibodies against each target, and reimbursement of specified research and development costs. We assessed this arrangement in accordance with ASC Topic 606 and concluded that the contract counterparty, Celgene, is a customer. We identified the following material promises under the Celgene Agreement: (1) the licenses under certain patent rights relating to four targets and transfer of certain development and regulatory information, (2) R&D services, (3) a written report documenting findings and (4) Steering Committee meetings. We considered the research and discovery capabilities of Celgene, Celgene’s inability to sub-license the four targets, and the fact that the discovery and optimization of these antibodies is proprietary and could not, at the time of the contract inception, be provided by other vendors, to conclude that the license does not have stand-alone functionality and is therefore not distinct. Additionally, we determined that the report of findings and steering committee participation would not have been provided without the R&D services and license agreement. Based on these assessments, we identified all services to be interrelated, and therefore concluded that the promises should be combined into a single performance obligation at the inception the arrangement. As of March 31, 2020 , the transaction price includes the upfront payment, success fees, expense reimbursement, and milestones earned to date, which are allocated in their entirety to the single performance obligation. None of the future clinical or regulatory milestones have been included in the transaction price, as all milestone amounts were subject to the revenue constraint. As part of the constraint evaluation, we considered numerous factors, including the fact that the receipt of milestones is outside of our control and contingent upon success in future clinical trials and the licensees’ efforts. Any consideration related to sales-based milestones, including royalties, will be recognized when the related sales occur as they were determined to relate predominantly to the IP license granted to Celgene and therefore have also been excluded from the transaction price. We will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Milestones achieved through March 31, 2020 under the Celgene Agreement are as follows: Anti-PD-1 Milestone Event Amount Quarter Recognized Completion of first in vivo toxicology studies using GLPs $0.5M Q2'16 Phase 1 clinical trial initiation $1.0M Q4'16 Revenue from future contingent milestone payments will be recognized when it is more likely than not that the revenue will not be reversed in future periods. Cash is generally received within 30 days of milestone achievement. There was no revenue recognized under this agreement during the three months ended March 31, 2020 and 2019 .

Notes Payable

Notes Payable	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Notes Payable	Notes Payable On December 24, 2014, we entered into a Loan and Security Agreement, as amended from time to time, the Loan Agreement, with a bank and a financial institution whereby we may borrow up to $15.0 million in three separate draws of $5.0 million each. The Term A Loans, for an aggregate of $5.0 million , were drawn on December 24, 2014 with a fixed interest rate of 6.97% . In January 2016, the Loan Agreement was amended to combine Term B Loans and Term C Loans for a total of $10.0 million available for draw through December 31, 2016 and delay the beginning of our Term A Loans’ principal repayments from February 1, 2016 until February 1, 2017. The Term B Loans and Term C Loans became available for draw on July 1, 2016. In December 2016, we further amended the Loan Agreement to (i) allow for the Term B Loans and Term C Loans to be drawn on December 30, 2016, (ii) delay principal repayments of all Term Loans until February 1, 2018 and (iii) amend the interest rate for each Term Loan. The Term B Loans and the Term C Loans were drawn on December 30, 2016, and Term A, B and C Loans are now collectively referred to as the Term Loans. Principal repayments began in February 2018, and were paid in full, without penalty or premium on January 1, 2020. The costs incurred to issue the Term Loans were deferred and were included in the discount to the carrying value of the Term Loans in the accompanying balance sheet. The Term Loans also included a final payment fee of $0.8 million

Fair Value Measurements and Ava

Fair Value Measurements and Available for Sale Investments	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements and Available for Sale Investments	Fair Value Measurements and Available for Sale Investments Fair Value Measurements Our financial instruments consist principally of cash, cash equivalents, restricted cash, short-term and long-term investments, receivables, accounts payable, and notes payable. Certain of our financial assets and liabilities have been recorded at fair value in the consolidated balance sheet in accordance with the accounting standards for fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Accounting guidance also establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard describes three levels of inputs that may be used to measure fair value: Level 1 - Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 - Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 - Unobservable inputs that are supported by little or no market activities, therefore requiring an entity to develop its own assumptions. Assets and Liabilities Measured at Fair Value on a Recurring Basis The following table summarizes our assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy: Fair Value Measurements at End of Period Using: (in thousands) Fair Quoted Market Significant Significant At March 31, 2020 Money market funds (1) $ 151,542 $ 151,542 $ — $ — Mutual funds (1) 13,883 13,883 — — U.S. Treasury securities (2) 112,933 112,933 — — Certificates of deposit (2) 5,685 — 5,685 — Agency securities (2) 41,890 — 41,890 — Commercial and corporate obligations (2) 86,873 — 86,873 — At December 31, 2019 Money market funds (1) $ 162,928 $ 162,928 $ — $ — Mutual funds (1) 7,619 7,619 — — U.S. Treasury securities (2) 96,434 96,434 — — Certificates of deposit (2) 5,428 — 5,428 — Agency securities (2) 33,623 — 33,623 — Commercial and corporate obligations (2) 122,030 — 122,030 — (1) Included in cash and cash equivalents or restricted cash in the accompanying consolidated balance sheets. (2) Included in short-term or long-term investments in the accompanying consolidated balance sheets depending on the respective maturity date. The following methods and assumptions were used to estimate the fair value of our financial instruments for which it is practicable to estimate that value: Marketable Securities. For fair values determined by Level 1 inputs, which utilize quoted prices in active markets for identical assets, the level of judgment required to estimate fair value is relatively low. For fair values determined by Level 2 inputs, which utilize quoted prices in less active markets for similar assets, the level of judgment required to estimate fair value is also considered relatively low. Fair Value of Other Financial Instruments The fair value of our other financial instruments estimated as of March 31, 2020 and December 31, 2019 are presented below: March 31, 2020 December 31, 2019 Carrying Fair Carrying Fair Notes payable $ — $ — $ 1,375 $ 1,365 The following methods and assumptions were used to estimate the fair value of our notes payable: Notes Payable —We use the income approach to value the aforementioned debt instrument. We use a present value calculation to discount principal and interest payments and the final maturity payment on these liabilities using a discounted cash flow model based on observable inputs. We discount these debt instruments based on what the current market rates would offer us as of the reporting date. Based on the assumptions used to value these liabilities at fair value, these debt instruments are categorized as Level 2 in the fair value hierarchy. The carrying amounts of certain of our financial instruments, including cash and cash equivalents, accounts payable, and accrued expenses approximate fair value due to their short-term nature. Available for Sale Investments We invest our excess cash in agency securities, debt instruments of financial institutions and corporations, commercial obligations, and U.S. Treasury securities, which we classify as available-for-sale investments. These investments are carried at fair value and are included in the tables above. The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in cash equivalents, short-term and long-term investments as of March 31, 2020 are as follows: (in thousands) Amortized Gross Gross Total Agency securities (1) $ 41,754 $ 139 $ (3 ) $ 41,890 Certificates of deposit (2) 5,639 46 — 5,685 Commercial and corporate obligations (3) 86,805 97 (29 ) 86,873 U.S. Treasury securities (4) 111,831 1,102 — 112,933 Total available-for-sale investments $ 246,029 $ 1,384 $ (32 ) $ 247,381 (1) Of our outstanding agency securities, $14.9 million have maturity dates of less than one year and $27.0 million have a maturity date of between one to two years as of March 31, 2020 . (2) Of our outstanding certificates of deposit, $5.0 million have a maturity date of less than one year and $0.7 million have a maturity date of between one to two years as of March 31, 2020 . (3) Of our outstanding commercial and corporate obligations, $82.6 million have maturity dates of less than one year and $4.3 million have a maturity date of between one to two years as of March 31, 2020 . (4) Of our outstanding U.S. Treasury securities, $94.7 million have maturity dates of less than one year and $18.2 million have a maturity date of between one to two years as of March 31, 2020 . The following tables present gross unrealized losses and fair values for those investments that were in an unrealized loss position as of March 31, 2020 and December 31, 2019 , aggregated by investment category and the length of time that individual securities have been in a continuous loss position: March 31, 2020 Less than 12 Months 12 Months or Greater Total (in thousands) Fair Value Gross Fair Value Gross Fair Value Gross Agency securities $ 1,848 $ (3 ) $ — $ — $ 1,848 $ (3 ) Commercial and corporate obligations 34,431 (29 ) — — 34,431 (29 ) Total $ 36,279 $ (32 ) $ — $ — $ 36,279 $ (32 ) December 31, 2019 Less than 12 Months 12 Months or Greater Total (in thousands) Fair Value Gross Fair Value Gross Fair Value Gross Commercial and corporate obligations $ 5,986 $ (4 ) $ — $ — $ 5,986 $ (4 ) US Treasury Securities 17,608 (2 ) — — 17,608 (2 ) Total $ 23,594 $ (6 ) $ — $ — $ 23,594 $ (6 )

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock Of the 500,000,000 shares of common stock authorized, 27,277,115 shares were issued and outstanding as of March 31, 2020 . Common stock reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at March 31, 2020 are as follows: Issued and Outstanding: Stock options 2,866,929 Shares Reserved For: 2017 Equity Incentive Plan 3,118,332 2017 Employee Stock Purchase Plan 997,682 Total 6,982,943

Equity Incentive Plans

Equity Incentive Plans	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Equity Incentive Plans	Equity Incentive Plans 2017 Equity Incentive Plan On January 12, 2017, our board of directors and stockholders approved and adopted the 2017 Equity Incentive Plan, or the 2017 Plan. The 2017 Plan became effective upon the execution and delivery of the underwriting agreement for our initial public offering on January 26, 2017, and replaced our existing 2006 Equity Incentive Plan, or the 2006 Plan. Under the 2017 Plan we may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then our employees, officers, directors or consultants. In addition, the number of shares of stock available for issuance under the 2017 Plan will be automatically increased each January 1, beginning on January 1, 2018, by 4% of the aggregate number of outstanding shares of our common stock as of the immediately preceding December 31 or such lesser number as determined by our board of directors. The 2017 Plan automatically increased by 1,090,203 shares as of January 1, 2020. Employee Stock Purchase Plan On January 12, 2017, our board of directors and stockholders approved and adopted the 2017 Employee Stock Purchase Plan or the ESPP. The ESPP became effective upon the execution and delivery of the underwriting agreement for our initial public offering on January 26, 2017. In addition, the number shares of stock available for issuance under the ESPP will be automatically increased each January 1, beginning on January 1, 2018, by 1% of the aggregate number of outstanding shares of our common stock as of the immediately preceding December 31 or such lesser number as determined by our board of directors. The ESPP automatically increased by 272,550 shares as of January 1, 2020. Stock Options Stock options granted to employees and non-employees generally vest over a four -year period while stock options granted to directors vest over a one year period. Each have a maximum term of ten years from the date of grant, subject to earlier cancellation prior to vesting upon cessation of service to us. A summary of the activity related to stock option awards during the three months ended March 31, 2020 is as follows: Shares Weighted-Average Weighted-Average Aggregate Outstanding at January 1, 2020 3,039,880 $ 29.40 Granted 115,550 $ 15.88 Exercises (22,033 ) $ 1.66 Forfeitures and cancellations (266,468 ) $ 37.14 Outstanding at March 31, 2020 2,866,929 $ 28.35 7.30 $ 6,683 Exercisable at March 31, 2020 1,423,084 $ 26.04 5.33 $ 6,565 Stock-Based Compensation Expense The estimated fair values of stock option awards granted to employees were determined on the date of grant using the Black-Scholes option valuation model with the following weighted average assumptions: Three Months Ended 2020 2019 Risk-free interest rate 1.7 % 2.5 % Expected volatility 92.0 % 68.5 % Expected dividend yield — % — % Expected term (in years) 6.25 6.25 Weighted average grant date fair value per share $ 11.25 $ 43.96 We determine the appropriate risk free interest rate, expected term for employee stock based awards, contractual term for non-employee stock based awards, and volatility assumptions. The weighted-average expected option term for employee and non-employee stock based awards reflects the application of the simplified method, which defines the life as the average of the contractual term of the options and the weighted average vesting period for all option tranches. Estimated volatility incorporates historical volatility of our stock price as well as similar entities whose share prices are publicly available. The risk free interest rate is based upon U.S. Treasury securities with remaining terms similar to the expected or contractual term of the stock based payment awards. The assumed dividend yield is based on our expectation of not paying dividends in the foreseeable future. Total non-cash stock based compensation expense for all stock awards that was recognized in the consolidated statements of operations and comprehensive loss is as follows: Three Months Ended (in thousands) 2020 2019 Research and development $ 1,146 $ 1,240 General and administrative 1,829 1,627 Total $ 2,975 $ 2,867 At March 31, 2020 , there was $27.7 million of unrecognized compensation cost related to unvested stock option awards, which is expected to be recognized over a remaining weighted average vesting period of 3.13 years

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases We have two non-cancellable office leases with remaining lease terms of approximately 1.5 years , each of which are classified as operating leases. Both leases expire in 2021. Only one of our leases has remaining renewal options, which includes three options to renew for one additional year. The exercise of lease renewal options is at our sole discretion, which we currently do not anticipate exercising and as such were not recognized as part of our ROU asset and lease liabilities. Our lease payments are fixed, and we recognize lease expense for these leases on a straight-line basis over the lease term. Operating lease ROU assets and lease liabilities are recorded based on the present value of the future minimum lease payments over the lease term at commencement date. As our leases do not provide an implicit rate, we used our incremental borrowing rate based on the information available at effective date of adoption in determining the present value of future payments. The weighted-average discount rate used was 8.59% . Our balance sheet includes our ROU assets and lease liabilities as follows (in thousands): Leases Classification on the Balance Sheet March 31, 2020 December 31, 2019 Operating ROU assets Other long-term assets $ 1,213 $ 1,402 Operating lease liabilities Other current liabilities 898 871 Operating lease liabilities Other long-term liabilities 419 654 The following costs are included in our cash flow statement (in thousands): Three Months Ended Leases Classification on the Cash Flow 2020 2019 Operating lease cost Operating $ 220 $ 220 Cash paid for amounts included in the measurement of lease liabilities Operating 239 231 At March 31, 2020 , the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows (in thousands): Years Ending December 31, 2020 $ 729 2021 676 2022 — 2023 — 2024 — Thereafter — Total minimum payments required 1,405 Less imputed interest (88 ) Total $ 1,317 Shareholder Lawsuit On March 25, 2020, a putative shareholder class action complaint was filed in the United States District Court for the Southern District of California against us and three of our current or former officers. The complaint purports to assert claims under Section 10(b) of the Exchange Act, Exchange Act Rule 10b-5, and Section 20(a) of the Exchange Act, on behalf of persons and entities who acquired our common stock between October 10, 2017 and November 7, 2019, or the Class Period. The complaint alleges that, during the Class Period, the defendants made material misrepresentations or omissions regarding our etokimab drug that artificially inflated our stock price. The plaintiff seeks, among other things, damages in an unspecified amount, as well as costs and expenses. We believe that the claims in the action are without merit.

Subsequent Event (Notes)

Subsequent Event (Notes)	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On May 4, 2020, we entered into a lease agreement, or Lease Agreement, with Wateridge Property Owner, LP, with respect to facilities in the building at 10770 Wateridge Circle, San Diego, California 92121. Under the Lease Agreement, we agreed to lease approximately 45,000 square feet of space in the 10770 Wateridge Circle Building for a term of 124 months , beginning on March 1, 2021 (or on such later date as described in the Lease Agreement). The terms of the Lease Agreement provide us with an option to extend the term of the lease for an additional five years , as well as a one-time option we have to terminate the lease after seven years with the payment of a termination fee. The monthly base rent will be $4.20 per rentable square foot, and will be increased by 3%

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP, have been omitted. The accompanying unaudited consolidated financial statements include all known adjustments necessary for a fair presentation of the results of interim periods as required by U.S. GAAP. These adjustments consist primarily of normal recurring accruals and estimates that impact the carrying value of assets and liabilities. Also, certain reclassifications have been made to 2019 financial information to conform to the current year presentation of prepaid expenses and other assets on the Consolidated Statements of Cash Flows. Operating results for the three months ended March 31, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020 . Interim results are not necessarily indicative of results for a full year, particularly in light of the novel coronavirus pandemic, or COVID-19, and its impact on domestic and global economies. To limit the spread of COVID-19, governments have taken various actions including the issuance of stay-at-home orders and social distancing guidelines, causing some businesses to suspend operations and or experience a reduction in demand for many products from direct or ultimate customers. Accordingly, businesses have adjusted, reduced or suspended operating activities. The effects of the stay-at-home orders and our work-from-home policies may negatively impact productivity, disrupt our business and delay our development programs, regulatory and commercialization timelines, the magnitude of which will depend, in part, on the length and severity of the restrictions and other limitations on our ability to conduct our business in the ordinary course. Our future research and development expenses and general and administrative expenses may vary significantly if we experience an increased impact from COVID-19 on the costs and timing associated with the conduct of our clinical trials and other related business activities. The financial statements should be read in conjunction with our audited financial statements for the year ended December 31, 2019 , included in our Annual Form 10-K.
Basis of Consolidation	Basis of Consolidation The accompanying consolidated financial statements include us and our wholly-owned Australian subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. We operate in one
Use of Estimates	Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. The full extent to which the COVID-19 pandemic will directly or indirectly impact our business, results of operations and financial condition, including expenses, reserves and allowances, manufacturing, clinical trials, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain it or treat COVID-19, as well as the economic impact on local, regional, national and international markets. Our actual results could differ from these estimates under different assumptions or conditions.
Net Loss Per Common Share	Net Loss Per Common Share Basic net loss per common share is computed by dividing net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common equivalent shares outstanding for the period, as well as any dilutive effect from outstanding stock options and warrants using the treasury stock method. For each period presented, there is no difference in the number of shares used to calculate basic and diluted net loss per share.
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In December 2019, the Financial Accounting Standards Board “FASB” issued ASU 2019-12, Income Taxes (Topic 740) intended to simplify the accounting for income taxes. The guidance removes the following exceptions: 1) exception to the incremental approach for intraperiod tax allocation when there is a loss from continuing operations and income or a gain from other items, 2) exception to the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment, 3) exception to the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity method investment becomes a subsidiary and 4) exception to the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. Additionally, the guidance simplifies the accounting for income taxes by: 1) requiring that an entity recognize a franchise tax (or similar tax) that is partially based on income as an income-based tax and account for any incremental amount incurred as a non-income-based tax, 2) requiring that an entity evaluate when a step up in the tax basis of goodwill should be considered part of the business combination in which the book goodwill was originally recognized and when it should be considered a separate transaction, 3) specifying that an entity is not required to allocate the consolidated amount of current and deferred tax expense to a legal entity that is not subject to tax in its separate financial statements (although the entity may elect to do so (on an entity-by-entity basis) for a legal entity that is both not subject to tax and disregarded by the taxing authority), 4) requiring that an entity reflect the effect of an enacted change in tax laws or rates in the annual effective tax rate computation in the interim period that includes the enactment date and 5) making minor improvements for income tax accounting related to employee stock ownership plans and investments in qualified affordable housing projects accounted for using the equity method. The guidance will be effective for fiscal years and interim periods beginning after December 15, 2020. Different components of the guidance require retrospective, modified retrospective or prospective adoption, and early adoption is permitted. We early adopted this standard on January 1, 2020 and the adoption of the standard did not have a material impact to our consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) , which changes the accounting treatment for recognizing the impairment of financial assets. Under the new guidance, credit losses for certain types of financial instruments will be estimated based on expected losses. The new guidance also eliminates the other-than-temporary impairment model for available-for-sale (AFS) debt securities. Entities will begin to recognize credit losses on AFS debt securities as allowances rather than as reductions in the carrying value of the securities. Impairment that is not credit-related impairment will continue to be recognized in other comprehensive income and entities will no longer consider the length of time a security has been in an unrealized loss position when determining whether a credit loss exists. ASU 2016-13 becomes effective for annual and interim periods beginning after December 15, 2019. We adopted this standard prospectively on January 1, 2020 and the adoption of the standard did not have a material impact to our consolidated financial statements as credit losses are not expected to be significant based on historical trends, the financial condition of our investments and external market factors. We will continue to actively monitor the impact of the recent coronavirus (COVID-19) pandemic on expected credit losses.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Schedule of Outstanding Potentially Dilutive Securities Excluded in the Calculation of Diluted Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in common stock equivalent shares): Three Months Ended (in thousands) 2020 2019 Options to purchase common stock 3,021 2,359

Balance Sheet Accounts and Su_2

Balance Sheet Accounts and Supplemental Disclosures (Tables)	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Property and Equipment	Property and equipment consist of the following: (in thousands) March 31, 2020 December 31, 2019 Laboratory equipment $ 5,018 $ 4,911 Office furniture and equipment 820 811 Leasehold improvements 575 575 Property and equipment, gross 6,413 6,297 Less: accumulated depreciation and amortization (4,803 ) (4,679 ) Total property and equipment, net $ 1,610 $ 1,618
Schedule of Accrued Expenses	Accrued expenses consist of the following: (in thousands) March 31, 2020 December 31, 2019 Accrued compensation and related expenses $ 1,363 $ 2,152 Accrued professional fees 494 435 Accrued research, development and manufacturing expenses 11,689 8,196 Other 235 269 Total accrued expenses $ 13,781 $ 11,052

Collaborative Research and De_2

Collaborative Research and Development Agreements (Tables)	3 Months Ended
	Mar. 31, 2020
Revenue Recognition [Abstract]
Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions	Milestones recognized through March 31, 2020 under the TESARO Agreement are as follows: Anti-PD-1 Anti-TIM-3 Anti-LAG-3 Milestone Event Amount Quarter Recognized Amount Quarter Recognized Amount Quarter Recognized Initiated in vivo toxicology studies using good laboratory practices (GLPs) $1.0M Q2'15 $1.0M Q4'15 $1.0M Q3'16 IND clearance from the FDA $4.0M Q1'16 $4.0M Q2'16 $4.0M Q2'17 Phase 2 clinical trial initiation $3.0M Q2'17 $3.0M Q4'17 $3.0M Q4'19 Phase 3 clinical trial initiation - first indication $5.0M Q3'18 — — — — Phase 3 clinical trial initiation - second indication $5.0M Q2'19 — — — — Filing of the first NDA - first indication $10.0M Q1'20 — — — — Filing of the first MAA - first indication $5.0M Q1'20 — — — — Milestones achieved through March 31, 2020 under the Celgene Agreement are as follows: Anti-PD-1 Milestone Event Amount Quarter Recognized Completion of first in vivo toxicology studies using GLPs $0.5M Q2'16 Phase 1 clinical trial initiation $1.0M Q4'16

Fair Value Measurements and A_2

Fair Value Measurements and Available for Sale Investments (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities that Require Fair Value Measurements on a Recurring Basis	The following table summarizes our assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy: Fair Value Measurements at End of Period Using: (in thousands) Fair Quoted Market Significant Significant At March 31, 2020 Money market funds (1) $ 151,542 $ 151,542 $ — $ — Mutual funds (1) 13,883 13,883 — — U.S. Treasury securities (2) 112,933 112,933 — — Certificates of deposit (2) 5,685 — 5,685 — Agency securities (2) 41,890 — 41,890 — Commercial and corporate obligations (2) 86,873 — 86,873 — At December 31, 2019 Money market funds (1) $ 162,928 $ 162,928 $ — $ — Mutual funds (1) 7,619 7,619 — — U.S. Treasury securities (2) 96,434 96,434 — — Certificates of deposit (2) 5,428 — 5,428 — Agency securities (2) 33,623 — 33,623 — Commercial and corporate obligations (2) 122,030 — 122,030 — (1) Included in cash and cash equivalents or restricted cash in the accompanying consolidated balance sheets. (2) Included in short-term or long-term investments in the accompanying consolidated balance sheets depending on the respective maturity date.
Fair Value of Other Financial Instruments	The fair value of our other financial instruments estimated as of March 31, 2020 and December 31, 2019 are presented below: March 31, 2020 December 31, 2019 Carrying Fair Carrying Fair Notes payable $ — $ — $ 1,375 $ 1,365
Available-for-sale Investments	The aggregate market value, cost basis, and gross unrealized gains and losses of available-for-sale investments by security type, classified in cash equivalents, short-term and long-term investments as of March 31, 2020 are as follows: (in thousands) Amortized Gross Gross Total Agency securities (1) $ 41,754 $ 139 $ (3 ) $ 41,890 Certificates of deposit (2) 5,639 46 — 5,685 Commercial and corporate obligations (3) 86,805 97 (29 ) 86,873 U.S. Treasury securities (4) 111,831 1,102 — 112,933 Total available-for-sale investments $ 246,029 $ 1,384 $ (32 ) $ 247,381 (1) Of our outstanding agency securities, $14.9 million have maturity dates of less than one year and $27.0 million have a maturity date of between one to two years as of March 31, 2020 . (2) Of our outstanding certificates of deposit, $5.0 million have a maturity date of less than one year and $0.7 million have a maturity date of between one to two years as of March 31, 2020 . (3) Of our outstanding commercial and corporate obligations, $82.6 million have maturity dates of less than one year and $4.3 million have a maturity date of between one to two years as of March 31, 2020 . (4) Of our outstanding U.S. Treasury securities, $94.7 million have maturity dates of less than one year and $18.2 million have a maturity date of between one to two years as of March 31, 2020 .
Schedule of Unrealized Loss and Fair Values in a Loss Position	The following tables present gross unrealized losses and fair values for those investments that were in an unrealized loss position as of March 31, 2020 and December 31, 2019 , aggregated by investment category and the length of time that individual securities have been in a continuous loss position: March 31, 2020 Less than 12 Months 12 Months or Greater Total (in thousands) Fair Value Gross Fair Value Gross Fair Value Gross Agency securities $ 1,848 $ (3 ) $ — $ — $ 1,848 $ (3 ) Commercial and corporate obligations 34,431 (29 ) — — 34,431 (29 ) Total $ 36,279 $ (32 ) $ — $ — $ 36,279 $ (32 ) December 31, 2019 Less than 12 Months 12 Months or Greater Total (in thousands) Fair Value Gross Fair Value Gross Fair Value Gross Commercial and corporate obligations $ 5,986 $ (4 ) $ — $ — $ 5,986 $ (4 ) US Treasury Securities 17,608 (2 ) — — 17,608 (2 ) Total $ 23,594 $ (6 ) $ — $ — $ 23,594 $ (6 )

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at March 31, 2020 are as follows: Issued and Outstanding: Stock options 2,866,929 Shares Reserved For: 2017 Equity Incentive Plan 3,118,332 2017 Employee Stock Purchase Plan 997,682 Total 6,982,943

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Activity Related to Stock Option Awards	A summary of the activity related to stock option awards during the three months ended March 31, 2020 is as follows: Shares Weighted-Average Weighted-Average Aggregate Outstanding at January 1, 2020 3,039,880 $ 29.40 Granted 115,550 $ 15.88 Exercises (22,033 ) $ 1.66 Forfeitures and cancellations (266,468 ) $ 37.14 Outstanding at March 31, 2020 2,866,929 $ 28.35 7.30 $ 6,683 Exercisable at March 31, 2020 1,423,084 $ 26.04 5.33 $ 6,565
Summary of Weighted Average Assumptions in Stock Option Valuations	The estimated fair values of stock option awards granted to employees were determined on the date of grant using the Black-Scholes option valuation model with the following weighted average assumptions: Three Months Ended 2020 2019 Risk-free interest rate 1.7 % 2.5 % Expected volatility 92.0 % 68.5 % Expected dividend yield — % — % Expected term (in years) 6.25 6.25 Weighted average grant date fair value per share $ 11.25 $ 43.96
Summary of Non-cash Stock-based Compensation Expense	Total non-cash stock based compensation expense for all stock awards that was recognized in the consolidated statements of operations and comprehensive loss is as follows: Three Months Ended (in thousands) 2020 2019 Research and development $ 1,146 $ 1,240 General and administrative 1,829 1,627 Total $ 2,975 $ 2,867

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Classification on the Balance Sheet	Our balance sheet includes our ROU assets and lease liabilities as follows (in thousands): Leases Classification on the Balance Sheet March 31, 2020 December 31, 2019 Operating ROU assets Other long-term assets $ 1,213 $ 1,402 Operating lease liabilities Other current liabilities 898 871 Operating lease liabilities Other long-term liabilities 419 654
Costs Included in Cash Flow Statement	The following costs are included in our cash flow statement (in thousands): Three Months Ended Leases Classification on the Cash Flow 2020 2019 Operating lease cost Operating $ 220 $ 220 Cash paid for amounts included in the measurement of lease liabilities Operating 239 231
Schedule of Future Minimum Annual Obligations	At March 31, 2020 , the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows (in thousands): Years Ending December 31, 2020 $ 729 2021 676 2022 — 2023 — 2024 — Thereafter — Total minimum payments required 1,405 Less imputed interest (88 ) Total $ 1,317

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020segment
Accounting Policies [Abstract]
Number of reportable segments	1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share (in shares)	3,021	2,359

Balance Sheet Accounts and Su_3

Balance Sheet Accounts and Supplemental Disclosures - Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,413	$ 6,297
Less: accumulated depreciation and amortization	(4,803)	(4,679)
Total property and equipment, net	1,610	1,618
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	5,018	4,911
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	820	811
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 575	$ 575

Balance Sheet Accounts and Su_4

Balance Sheet Accounts and Supplemental Disclosures - Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and related expenses	$ 1,363	$ 2,152
Accrued professional fees	494	435
Accrued research, development and manufacturing expenses	11,689	8,196
Other	235	269
Total accrued expenses	$ 13,781	$ 11,052

Collaborative Research and De_3

Collaborative Research and Development Agreements (Details)

1 Months Ended

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6 Months Ended

12 Months Ended

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Sep. 30, 2018USD ($)

Dec. 31, 2017USD ($)

Jun. 30, 2017USD ($)

Dec. 31, 2016USD ($)

Sep. 30, 2016USD ($)

Jun. 30, 2016USD ($)

Mar. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Jun. 30, 2015USD ($)

Jun. 30, 2019USD ($)

Dec. 31, 2011USD ($)

Deferred Revenue Arrangement [Line Items]

Collaboration revenue

$ 15,000,000

$ 0

TESARO | Collaborative Research And Development Agreement

Deferred Revenue Arrangement [Line Items]

Upfront license fee received

$ 2,000,000

$ 17,000,000

Number of outstanding research and development targets | target

4

3

Milestone payments, contingent upon preclinical and clinical trial events (up to)

$ 18,000,000

Milestone payments, contingent upon certain U.S. and European regulatory submissions and approvals (up to)

90,000,000

Milestone payments, contingent upon achievement of specified levels of worldwide sales (up to)

$ 165,000,000

Agreement term following first commercial sale or expiration of the last to expire patent (in years)

12 years

Number of milestones achieved during period | milestone

2

Collaboration revenue

$ 15,000,000

0

TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 1,000,000

TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-TIM-3 (TSR022/Cobolimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 1,000,000

TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-LAG-3 (TSR033/Encelimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 1,000,000

TESARO | IND clearance from the FDA | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 4,000,000

TESARO | IND clearance from the FDA | Anti-TIM-3 (TSR022/Cobolimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 4,000,000

TESARO | IND clearance from the FDA | Anti-LAG-3 (TSR033/Encelimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 4,000,000

TESARO | Phase 2 clinical trial initiation | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 3,000,000

TESARO | Phase 2 clinical trial initiation | Anti-TIM-3 (TSR022/Cobolimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 3,000,000

TESARO | Phase 2 clinical trial initiation | Anti-LAG-3 (TSR033/Encelimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 3,000,000

TESARO | Phase 3 clinical trial initiation | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

15,000,000

$ 5,000,000

TESARO | Phase 3 clinical trial initiation - second indication [Domain] | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

$ 5,000,000

TESARO | Filing of the first NDA - first indication | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

10,000,000

TESARO | Filing of the first MAA - first indication | Anti-PD-1 (TSR042/Dostarlimab)

Deferred Revenue Arrangement [Line Items]

Milestones achieved, amount

5,000,000

Celgene Corporation | Collaborative Research And Development Agreement

Deferred Revenue Arrangement [Line Items]

Upfront license fee received

$ 6,000,000

Collaboration revenue

$ 0

$ 0

Maximum milestone payments per target

$ 53,000,000

Celgene Corporation | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-PD-1 (CC-90006)

Deferred Revenue Arrangement [Line Items]

Milestone Event

$ 500,000

Celgene Corporation | Phase 1 clinical trial initiation | Anti-PD-1 (CC-90006)

Deferred Revenue Arrangement [Line Items]

Milestone Event

$ 1,000,000

Notes Payable (Details)

Notes Payable (Details) - Notes Payable to Banks	Dec. 24, 2014USD ($)installment	Jan. 31, 2016USD ($)
Debt Instrument [Line Items]
Aggregate borrowing capacity	$ 5,000,000
Loan and Security Agreement (LSA)
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity	$ 15,000,000
Number of loan installments (in installments) | installment	3
Final payment fee		$ 800,000
Term A Loans
Debt Instrument [Line Items]
Aggregate draw on term loan	$ 5,000,000
Fixed interest rate (as a percent)	6.97%
Term B and Term C Loans
Debt Instrument [Line Items]
Aggregate borrowing capacity		$ 10,000,000

Fair Value Measurements and A_3

Fair Value Measurements and Available for Sale Investments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	$ 247,381
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,933
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	5,685
Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	41,890
Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	86,873
Fair Value, Measurements, Recurring | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,933	$ 96,434
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	5,685	5,428
Fair Value, Measurements, Recurring | Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	41,890	33,623
Fair Value, Measurements, Recurring | Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	86,873	122,030
Fair Value, Measurements, Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	151,542	162,928
Fair Value, Measurements, Recurring | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	13,883	7,619
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	112,933	96,434
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	151,542	162,928
Fair Value, Measurements, Recurring | Quoted Market Prices for Identical Assets (Level 1) | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	13,883	7,619
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	5,685	5,428
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	41,890	33,623
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	86,873	122,030
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities, debt securities	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value	$ 0	$ 0

Fair Value Measurements and A_4

Fair Value Measurements and Available for Sale Investments - Fair Value of Other Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	$ 0	$ 1,375
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Notes payable	$ 0	$ 1,365

Fair Value Measurements and A_5

Fair Value Measurements and Available for Sale Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 246,029
Gross Unrealized Gains	1,384
Gross Unrealized Losses	(32)
Total Fair Value	247,381
Short-term investments	197,166	$ 203,210
Long-term investments	50,215	$ 54,305
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	41,754
Gross Unrealized Gains	139
Gross Unrealized Losses	(3)
Total Fair Value	41,890
Short-term investments	14,900
Long-term investments	$ 27,000
Agency securities | Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Agency securities | Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 5,639
Gross Unrealized Gains	46
Gross Unrealized Losses	0
Total Fair Value	5,685
Short-term investments	5,000
Long-term investments	$ 700
Certificates of deposit | Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Certificates of deposit | Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 86,805
Gross Unrealized Gains	97
Gross Unrealized Losses	(29)
Total Fair Value	86,873
Short-term investments	82,600
Long-term investments	$ 4,300
Commercial and corporate obligations | Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
Commercial and corporate obligations | Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 111,831
Gross Unrealized Gains	1,102
Gross Unrealized Losses	0
Total Fair Value	112,933
Short-term investments	94,700
Long-term investments	$ 18,200
U.S. Treasury securities | Minimum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	1 year
U.S. Treasury securities | Maximum
Debt Securities, Available-for-sale [Line Items]
Investments outstanding, maturity date range (in years)	2 years

Fair Value Measurements and A_6

Fair Value Measurements and Available for Sale Investments - Schedule of Unrealized Loss and Fair Values in a Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	$ 36,279	$ 23,594
Less than 12 Months, Gross Unrealized Losses	(32)	(6)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Gross Unrealized Losses	0	0
Fair Value	36,279	23,594
Gross Unrealized Losses	(32)	(6)
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	1,848
Less than 12 Months, Gross Unrealized Losses	(3)
12 Months or Greater, Fair Value	0
12 Months or Greater, Gross Unrealized Losses	0
Fair Value	1,848
Gross Unrealized Losses	(3)
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	34,431	5,986
Less than 12 Months, Gross Unrealized Losses	(29)	(4)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Gross Unrealized Losses	0	0
Fair Value	34,431	5,986
Gross Unrealized Losses	$ (29)	(4)
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value		17,608
Less than 12 Months, Gross Unrealized Losses		(2)
12 Months or Greater, Fair Value		0
12 Months or Greater, Gross Unrealized Losses		0
Fair Value		17,608
Gross Unrealized Losses		$ (2)

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	27,277,115	27,255,000
Common stock, shares outstanding (in shares)	27,277,115	27,255,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Issued and Outstanding:
Stock options issued and outstanding (in shares)	2,866,929	3,039,880
Common stock, shares reserved for issuance (in shares)	6,982,943
2017 Equity Incentive Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	3,118,332
2017 Employee Stock Purchase Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	997,682

Equity Incentive Plans - Narrat

Equity Incentive Plans - Narrative (Details) - USD ($) $ in Millions	Jan. 01, 2019	Jan. 01, 2018	Jan. 26, 2017	Mar. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				$ 27.7
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				4 years
Award expiration period (in years)				10 years
Options to purchase common stock | Director Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)				1 year
Award expiration period (in years)				10 years
Employee and nonemployee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period remaining for amortization of unrecognized compensation cost (in years)				3 years 1 month 17 days
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in number of shares available for issuance			4.00%
Capital shares reserved for future issuance, increase (in shares)	1,090,203
2017 Employee Stock Purchase Plan | Employee stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in number of shares available for issuance		1.00%
Capital shares reserved for future issuance, increase (in shares)	272,550

Equity Incentive Plans - Option

Equity Incentive Plans - Option Activity (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Shares Subject to Options
Stock options outstanding, beginning balance (in shares) | shares	3,039,880
Granted (in shares) | shares	115,550
Exercises (in shares) | shares	(22,033)
Forfeitures and cancellations (in shares) | shares	(266,468)
Stock options outstanding, ending balance (in shares) | shares	2,866,929
Stock options exercisable, ending balance (in shares) | shares	1,423,084
Weighted-Average Exercise Price per Share
Stock options outstanding, beginning balance (in dollars per share) | $ / shares	$ 29.40
Granted (in dollars per share) | $ / shares	15.88
Exercises (in dollars per share) | $ / shares	1.66
Forfeitures and cancellations (in dollars per share) | $ / shares	37.14
Stock options outstanding, ending balance (in dollars per share) | $ / shares	28.35
Stock options exercisable, ending balance (in dollars per share) | $ / shares	$ 26.04
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted average remaining contractual term, options outstanding (in years)	7 years 3 months 18 days
Weighted average remaining contractual term, options exercisable (in years)	5 years 3 months 29 days
Aggregate intrinsic value, options outstanding | $	$ 6,683
Aggregate intrinsic value, options exercisable | $	$ 6,565

Equity Incentive Plans - Opti_2

Equity Incentive Plans - Option Fair Value Assumptions (Details) - Options to purchase common stock - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.70%	2.50%
Expected volatility	92.00%	68.50%
Expected dividend yield	0.00%	0.00%
Expected term (in years)	6 years 3 months	6 years 3 months
Weighted average grant date fair value per share (in dollars per share)	$ 11.25	$ 43.96

Equity Incentive Plans - Alloca

Equity Incentive Plans - Allocation of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,975	$ 2,867
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,146	1,240
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,829	$ 1,627

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020leaserenewal_option
Operating Leased Assets [Line Items]
Non-cancellable office leases | lease	2
Operating lease, term of contract	1 year 6 months
Weighted-average discount rate	8.59%
One office lease
Operating Leased Assets [Line Items]
Number of one year renewal options | renewal_option	3

Commitments and Contingencies_2

Commitments and Contingencies - Classification on the Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating ROU assets, Other long-term assets	$ 1,213	$ 1,402
Operating lease liabilities, Other current liabilities	898	871
Operating lease liabilities, Other long-term liabilities	$ 419	$ 654

Commitments and Contingencies_3

Commitments and Contingencies - Costs Included in Cash Flow Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 220	$ 220
Cash paid for amounts included in the measurement of lease liabilities	$ 239	$ 231

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Future Minimum Annual Obligations (Details) $ in Thousands	Mar. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2020	$ 729
2021	676
2022	0
2023	0
2024	0
Thereafter	0
Total minimum payments required	1,405
Less imputed interest	(88)
Total	$ 1,317

Subsequent Event (Details)

Subsequent Event (Details) - Subsequent event ft² in Thousands	May 04, 2020ft²$ / ft²
Subsequent Event [Line Items]
Area of leased property (sqft) | ft²	45
Lease term	124 months
Lease renewal term	5 years
Lease termination term	7 years
Monthly base rate (usd per sqft) | $ / ft²	4.20
Increase in annual rent	3.00%