0001370053-21-000019 | 10-K | XBRL Viewer

Cover page - USD ($)	12 Months Ended
Cover page - USD ($)	Dec. 31, 2020	Feb. 23, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 555,993,474
Entity Common Stock, Shares Outstanding		27,366,405
Documents Incorporated by Reference	Portions of the registrant’s Definitive Proxy Statement relating to the 2021 Annual Meeting of Shareholders, scheduled to be held on June 17, 2021, are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein. The Definitive Proxy Statement will be filed within 120 days of the Registrant’s fiscal year ended December 31, 2020. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.
Entity Central Index Key	0001370053
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 250,456	$ 171,017
Short-term investments	143,197	203,210
Prepaid expenses and other current assets	2,908	3,506
Total current assets	396,561	377,733
Property and equipment, net	1,783	1,618
Long-term investments	17,546	54,305
Other long-term assets	602	1,481
Restricted cash	60	60
Total assets	416,552	435,197
Current liabilities:
Accounts payable	4,217	16,237
Accrued expenses	15,262	11,052
Notes payable, current portion	0	1,375
Other current liabilities	342	871
Total current liabilities	19,821	29,535
Other long-term liabilities	0	654
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000 shares authorized and no shares, issued or outstanding at December 31, 2020 and December 31, 2019, respectively	0	0
Common stock, $0.001 par value, 500,000 shares authorized, 27,356 shares and 27,255 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively	27	27
Additional paid in capital	660,665	648,669
Accumulated other comprehensive (loss) income	(4)	338
Accumulated deficit	(263,957)	(244,026)
Total stockholders’ equity	396,731	405,008
Total liabilities and stockholders’ equity	$ 416,552	$ 435,197

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
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)	27,355,575	27,255,000
Common stock, shares outstanding (in shares)	27,355,575	27,255,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares outstanding (in shares)	0	0
Preferred stock, shares issued (in shares)	0	0

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Collaboration revenue	$ 75,000	$ 8,000	$ 5,000
Operating expenses:
Research and development	80,025	99,338	56,196
General and administrative	18,854	16,094	15,526
Total operating expenses	98,879	115,432	71,722
Loss from operations	(23,879)	(107,432)	(66,722)
Other income (expense), net:
Interest expense	0	(1,041)	(1,652)
Interest income	3,959	10,984	6,685
Other (expense) income, net	(11)	1	(159)
Total other income (expense), net	3,948	9,944	4,874
Loss before income taxes	(19,931)	(97,488)	(61,848)
Provision for income taxes	0	152	192
Net loss	(19,931)	(97,336)	(61,656)
Other comprehensive (loss) income:
Unrealized (loss) income on available for sale securities, net of tax of $0, $153, and $55, respectively	(342)	561	203
Comprehensive loss	$ (20,273)	$ (96,775)	$ (61,453)
Net loss per common share:
Basic and diluted (in dollars per share)	$ (0.73)	$ (3.60)	$ (2.50)
Weighted-average number of shares outstanding:
Basic and diluted (in shares)	27,302	27,059	24,673

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Income tax expense related to other comprehensive income	$ 0	$ 153	$ 55

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Stockholders' Equity, Beginning Balance (in shares) at Dec. 31, 2017		23,791,000
Stockholders' Equity, Beginning Balance at Dec. 31, 2017	$ 307,581	$ 24	$ 393,017	$ (426)	$ (85,034)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for public offerings, net of underwriters' fees (in shares)		2,530,000
Shares issued for public offerings, net of underwriters' fees	227,476	$ 3	227,473
Total offering costs	(145)		(145)
Shares issued under employee stock plans (in shares)		584,000
Shares issued under employee stock plans	2,869		2,869
Warrants exercised (in shares)		17,000
Warrants exercised	76		76
Stock-based compensation	9,961		9,961
Comprehensive income (loss)	203			203
Net loss	(61,656)				(61,656)
Stockholders' Equity, Ending Balance (in shares) at Dec. 31, 2018		26,922,000
Stockholders' Equity, Ending Balance at Dec. 31, 2018	486,365	$ 27	633,251	(223)	(146,690)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans (in shares)		333,000
Shares issued under employee stock plans	3,007		3,007
Stock-based compensation	12,411		12,411
Comprehensive income (loss)	561			561
Net loss	(97,336)				(97,336)
Stockholders' Equity, Ending Balance (in shares) at Dec. 31, 2019		27,255,000
Stockholders' Equity, Ending Balance at Dec. 31, 2019	$ 405,008	$ 27	648,669	338	(244,026)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under employee stock plans (in shares)	100,493	101,000
Shares issued under employee stock plans	$ 497		497
Stock-based compensation	11,499		11,499
Comprehensive income (loss)	(342)			(342)
Net loss	(19,931)				(19,931)
Stockholders' Equity, Ending Balance (in shares) at Dec. 31, 2020		27,356,000
Stockholders' Equity, Ending Balance at Dec. 31, 2020	$ 396,731	$ 27	$ 660,665	$ (4)	$ (263,957)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (19,931)	$ (97,336)	$ (61,656)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	559	514	315
Stock-based compensation	11,499	12,411	9,961
Accretion/amortization of investments, net	461	(2,633)	(1,233)
Non-cash interest expense	0	676	646
Income taxes	0	0	139
Loss on disposal of property and equipment, net of gain on lease termination	26	0	0
Changes in operating assets and liabilities:
Australian tax incentive receivable	0	174	1,427
Prepaid expenses and other assets	2,106	2,178	(5,188)
Accounts payable and other liabilities	(8,877)	14,499	7,083
Net cash used in operating activities	(14,157)	(69,517)	(48,506)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of investments	(194,927)	(251,815)	(347,537)
Sales and maturities of investments	289,971	384,051	206,149
Purchases of property and equipment	(569)	(805)	(1,063)
Net cash provided by (used in) investing activities	94,475	131,431	(142,451)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from public offerings, net of underwriters' fees	0	0	227,476
Proceeds from issuance of common stock, upon the exercise of stock options	496	3,007	2,869
Proceeds from issuance of common stock, upon the exercise of warrants	0	0	76
Payments on notes payable	(1,375)	(7,500)	(6,875)
Payments for offering costs, net	0	0	(182)
Net cash (used in) provided by financing activities	(879)	(4,493)	223,364
Net increase in cash, cash equivalents, and restricted cash	79,439	57,421	32,407
Cash, cash equivalents and restricted cash, beginning of period	171,077	113,656	81,249
Cash, cash equivalents and restricted cash, end of period	250,516	171,077	113,656
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Interest paid	4	424	1,043
Non-cash investing and financing activities:
Amounts accrued for property and equipment	$ 279	$ 41	$ 159

Description of the Business	12 Months Ended
Description of the Business	Dec. 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 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, 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 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. Our management believes our currently available resources will provide sufficient funds to enable us to meet our 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. Follow-on Public Offering On September 28, 2018, we completed an underwritten public offering of 2,530,000 shares of common stock, which included the exercise of the underwriters’ option to purchase an additional 330,000 shares of common stock. All shares were offered by us at a price to the public of $94.46 per share. The aggregate net proceeds received by us from the offering were $227.5 million, net of underwriting discounts and commissions.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP.

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 our 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 or treat it, 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.

Cash and Cash Equivalents

We consider all highly liquid investments with a maturity at date of purchase of three months or less to be cash equivalents. Cash equivalents consist primarily of money market and mutual funds with original maturities of 90 days or less.

Restricted Cash

We held restricted cash of $60,000 at December 31, 2020 and 2019, respectively, which we used to secure a letter of credit provided as security for the operating lease for our corporate headquarters.

Short-Term and Long-Term Investments

All investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Those investments with contractual maturities 12 months or greater at the balance sheet date are considered long-term investments. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss). We review our portfolio of available-for-sale debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, a loss is recognized in net income, whereas if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss).

Concentration of Credit Risk

Financial instruments that potentially subject us to a concentration of credit risk consist of cash and cash equivalents and certain investments in money market funds, certificates of deposit, agency securities, commercial obligations and U.S. Treasury securities. Bank deposits are diversified between three financial institutions and these deposits may exceed insured limits. We are exposed to credit risk in the event of default by the financial institutions holding our cash and cash equivalents and issuers of investments that are recorded on our consolidated balance sheets. We mitigate our risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits our exposure.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation. Expenditures for major additions and betterments are capitalized. Maintenance and repairs are charged to operations as incurred. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the assets, which range from three to seven years. Leasehold improvements are amortized using the straight line method over the term of the lease. Upon sale or retirement of property and equipment, the related cost and accumulated depreciation are removed from the accounts and any gain or loss is reflected in operations.

Long Lived Assets

Long-lived assets, consisting of property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable based on undiscounted cash flows. If long-lived assets are impaired, an impairment loss is recognized and is measured as the amount by which the carrying value exceeds the estimated fair value of the assets. No impairment charges were recorded during the years ended December 31, 2020, 2019, or 2018.

Leases

Our leases consist of leases for office space that are classified as operating leases. We determine if an arrangement is a lease at inception. Rent expense is recognized on a straight-line basis. When an operating lease includes rent abatements or requires fixed escalations of the minimum lease payments, the aggregate rental expense is recognized on a straight-line basis over the term of the lease. When an operating lease includes lease incentives such as leasehold improvement allowances, the lease incentive is included in the right-of-use (“ROU”) asset. For leases that have greater than a 12-month lease term, the ROU assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term. For this purpose, we consider only payments that are fixed and determinable at the time of commencement.

As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. We account for fixed lease components separately from non-lease components.

We keep leases with an initial term of 12 months or less off the balance sheet and recognize the associated lease payments in the consolidated statements of operations on a straight-line basis over the lease term.

Results and disclosure requirements for reporting periods beginning after January 1, 2019 are presented under ASC 842, while prior period amounts have not been adjusted and continue to be reported under ASC 840.

Revenue Recognition

Revenue is recognized in accordance with revenue recognition accounting guidance, which utilizes five basic steps to determine whether revenue can be recognized and to what extent: (i) identify the contract with a customer; (ii) identify the performance obligation; (iii) determine the transaction price; (iv) allocate the transaction price; and (v) determine the recognition period.

Performance Obligations. We evaluate deliverables on a contract-by-contract basis to determine whether each deliverable represents a good or service that is distinct or has the same pattern of transfer as other deliverables. A deliverable is considered distinct if the customer can benefit from the good or service independently of other goods/services either in the contract or that can be obtained elsewhere, without regard to contract exclusivity, and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contact. If the deliverable is not considered distinct, we combine such deliverables and account for them as a single performance obligation. We allocate the consideration to each deliverable at the inception of the arrangement based on the transaction price.

Our performance obligations may include the following:

•License Arrangements. The performance obligations under our collaboration and license agreements generally include exclusive or nonexclusive licenses to one or more products generated using our technologies. Licenses for multiple antibodies within a single contract are generally combined as they have substantially the same pattern of transfer to the customer. Historically, our licenses have held no value to the customer, as the antibodies were in the discovery phase and required our expertise for further development. Accordingly, licenses are not considered distinct.

•Research and Development Services. The performance obligations under our collaboration and license agreements generally include research and development services we perform on behalf of or with our collaborators. As discussed within license arrangements above, our licenses have historically held no value without the research and development services we provide. As we generally only provide research and development services for internally generated antibodies that require a license to be utilized by a third party, our research and development services are not considered distinct.

•Steering Committee Meetings. The performance obligations under our collaboration and license agreements may also include our participation in a steering committees, which allows us to direct the progression of our discovery programs. As these steering committees would not occur or benefit the customer without the use of our licenses, these are not considered distinct.

We recognize consideration allocated to a performance obligation as the performance obligation is satisfied, and the determination as to whether consideration is recognized over time or at a point in time is made upon contract inception. For our collaboration agreements, this is generally over the period in which research and development services have been performed.

Transaction Price. Our collaboration and license agreements generally include both fixed and variable consideration. Fixed payments, such as those for upfront fees are included in the transaction price at contract value, while variable consideration such as reimbursement for research and development services, milestone and royalty payments are estimated and then evaluated for constraints upon inception of the contract and evaluated on a quarterly basis thereafter. Research and development services are updated for actual invoices. Given the nature of our agreements, milestones are estimated using the most likely amount and are evaluated on a quarterly basis. Upon commercialization, royalty payments will be recognized in the period incurred.

Research and Development Expenses

Research and development costs primarily include third-party clinical and preclinical research and development services such as manufacturing, laboratory and related supplies, salaries and personnel-related costs, in-licensing fees, outside services, and an allocation of information technology, and facility overhead costs.

Costs associated with research and development activities are expensed as incurred. We account for nonrefundable advance payments for goods and services that will be used in future research and development activities as expense when the service has been performed or when the goods have been received. We estimate research and development costs incurred during the period, which impacts the amount of accrued expenses and prepaid balances related to such costs as of each balance sheet date. This process involves reviewing open contracts and purchase orders, communicating with our personnel and service providers to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued expenses as of each balance sheet date based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments if necessary. The significant estimates in our accrued research and development expenses include the costs incurred for services performed by our vendors in connection with research and development activities for which we have not yet been invoiced.

Upfront and milestone payments incurred under our in-licensing agreements are expensed as acquired in-process research and development in the period in which they are incurred, provided that the technology or method has no alternative future use.

Stock-Based Compensation

We recognize stock-based compensation expense using a fair-value-based method for costs related to all share-based payments, including stock options. Stock-based compensation cost for stock options granted to our employees and directors is measured at the grant date based on the fair-value of the award which is estimated using the Black-Scholes option-pricing model, and is recognized as expense over the requisite service period on a straight-line basis. We recognize forfeitures in the period in which forfeiture occur and record stock-based compensation expense as though all awards are expected to vest.

No tax benefits for stock-based compensation have been recognized in the statements of changes in stockholders’ equity or cash flows. We have not recognized, and do not expect to recognize in the near future, any tax benefit related to stock-based compensation cost as a result of our full valuation allowance on net deferred tax assets and net operating loss carryforwards.

Income Taxes

We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax basis of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to be recovered or settled. Realization of deferred tax assets is dependent upon future taxable income. A valuation allowance is recognized if it is more likely than not that some portion or all of a deferred tax asset will not be realized based on the weight of available evidence, including expected future earnings.

We recognize an uncertain tax position in our consolidated financial statements when we conclude that a tax position is more likely than not to be sustained upon examination based solely on technical merits. Only after a tax position passes the first step of recognition will measurement be required. Under the measurement step, the tax benefit is measured as the largest amount of benefit that is more likely than not to be realized upon effective settlement. This is determined on a cumulative probability basis. The full impact of any change in recognition or measurement is reflected in the period in which such change occurs. We have elected to accrue any interest or penalties related to income taxes as part of our income tax expense.

Functional Currency of Foreign Operations

Our Australian subsidiary operates in a U.S. dollar functional currency environment. Assets and liabilities of our foreign subsidiary that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets and capital accounts, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Expenses are generally remeasured at monthly foreign currency exchange rates which approximate average rates in effect during each period. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), net, in the consolidated statements of operations.

Comprehensive Income (Loss)

Comprehensive income (loss) represents all changes in stockholders’ equity except those resulting from distributions to stockholders. Our unrealized gain and losses on available for sale investments represent the only component of other comprehensive income (loss) that is excluded from the reported net income (loss).

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.

The following table sets forth the weighted-average 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):


	Year Ended December 31,
(in thousands)		2020	2019	2018

Options to purchase common stock		2,901	2,462	2,451

Accounting Pronouncements Recently Adopted

In December 2019, the Financial Accounting Standards Board (the “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 COVID-19 pandemic on expected credit losses.

In February 2016, the FASB, issued ASU 2016-02, Leases (Topic 842), which requires that lessees recognize a ROU asset and a related lease liability on the balance sheet for all leases with a term longer than 12 months. Topic 842 was subsequently amended by ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU 2018-10, Codification Improvements to Topic 842, Leases; ASU 2018-11, Targeted Improvements; and ASU 2019-01, Leases (Topic 842): Codification Improvements. ASU 2016-02 became effective for our annual reporting period beginning January 1, 2019, including interim periods thereafter. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of

the earliest comparative period presented in the financial statements as its date of initial application. We adopted this standard on January 1, 2019 and used the effective date as our date of initial application. Upon adoption, we elected the package of transition practical expedients, which allowed us to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. We also made an accounting policy election to not recognize leases with an initial term of 12 months or less within our consolidated balance sheets and to recognize those lease payments on a straight-line basis in our consolidated statements of operations over the lease term. Adoption of the new standard resulted in the recording of operating lease ROU assets and lease liabilities of approximately $2.1 million and $2.3 million as of January 1, 2019, respectively related to our real estate leases. Adoption of this new standard did not have a material impact on our consolidated statements of operations or cash flows.

Balance Sheet Accounts and Supplemental Disclosures

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Accounts and Supplemental Disclosures

Property and Equipment

Property and equipment consist of the following:


(in thousands)	December 31, 2020		December 31, 2019
Laboratory equipment	$	5,225	$	4,911
Office furniture and equipment	976		811
Leasehold improvements	527		575
Property and equipment, gross	6,728		6,297
Less: accumulated depreciation and amortization	(4,945)		(4,679)
Total property and equipment, net	$	1,783	$	1,618

We recorded a loss of approximately $0.1 million in other income (expense), net, related to the disposal of tenant improvements and certain equipment in connection with the termination of the 10455 Building Lease. The $0.1 million loss is recorded in the consolidated statements of cash flows net of the gain from the termination of the 10455 Building Lease (see Note 11).

Accrued Expenses

Accrued expenses consist of the following:


(in thousands)	December 31, 2020		December 31, 2019
Accrued compensation and related expenses	$	3,688	$	2,152
Accrued professional fees	408		435
Accrued research and development expenses	10,936		8,196
Other	230		269
Total accrued expenses	$	15,262	$	11,052

Collaborative Research and Development Agreements

12 Months Ended

Dec. 31, 2020

Revenue Recognition [Abstract]

Collaborative Research and Development Agreements

GlaxoSmithKline Collaboration

In March 2014, we entered into a Collaboration and Exclusive License Agreement (the “GSK Agreement”) with TESARO, Inc. (“Tesaro”), an oncology-focused biopharmaceutical company now a part of GlaxoSmithKline (Tesaro and GlaxoSmithKline are hereinafter referred to, collectively, as “GSK”). Under the terms of the GSK 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 GSK. Under the terms of the GSK Agreement, GSK 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, Amendment No. 1 to the GSK Agreement was agreed by both parties to add an antibody discovery program against an undisclosed fourth 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 GSK, 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 GSK Agreement will terminate, with respect to each specific developed product, upon the later of the 12th 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 GSK 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 February 2016, Amendment No. 2 to the GSK Agreement was agreed by both parties to define the effective dates of the development programs of the GSK Agreement. 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 discovery milestones were recognized was extended through December 31, 2016 and have since been recognized in full.

We assessed these arrangements in accordance with ASC 606 and concluded that the contract counterparty, GSK, is a customer. We identified the following material promises under the GSK Agreement: (1) the licenses under certain patent rights relating to six discovery programs (four targets) and transfer of certain development and regulatory information, (2) research and development (“R&D”) services, and (3) joint steering committee meetings. We considered the research and discovery capabilities of GSK for these specific programs, GSK’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 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 joint 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.

On October 23, 2020, Amendment No. 3 to the GSK Agreement (the “Amendment”) was agreed to by both parties to permit GSK to conduct development and commercialization of Zejula, an oral, once-daily poly (ADP-ribose) polymerase (PARP) inhibitor, which has received US approval for the maintenance treatment of adult patients with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer who are in a complete or partial response to first-line platinum-based chemotherapy, and is under development for additional cancer indications. In addition, under the Amendment, we were granted increased royalties upon sales of dostarlimab, an anti-PD-1 antagonist antibody under development by GSK for multiple oncological disorders. The Amendment also provided for a one-time, non-refundable cash payment of $60.0 million that we received and recognized as revenue in the fourth quarter of 2020. GSK also agreed, starting January 1, 2021, to pay us a 1% royalty on all GSK Net Sales of Zejula. The $1.1 billion in cash milestone payments due under the GSK Agreement remain unchanged. Additionally, under the terms of the Amendment, GSK has agreed to certain diligence commitments with respect to the future development of dostarlimab, and the parties have agreed to review such commitments under regular joint review committee meetings going forward.

We assessed this Amendment in accordance with ASC 606 and concluded the Amendment was a contract modification to the GSK Agreement. Based on our assessment, we identified the terms of the Amendment to be interrelated to the GSK Agreement’s single performance obligation, noting completion and delivery of terms under the Amendment were satisfied by both parties with the execution of the Amendment.

As of December 31, 2020, the transaction price for the GSK Agreement and Amendment includes the upfront payment, research reimbursement revenue, one-time payment associated to Amendment No. 3, 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 year ended December 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 GSK’s 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 intellectual property license granted to GSK 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 December 31, 2020 under the GSK Agreement are as follows:

Anti-PD-1

(GSK4057190A/Dostarlimab)

Anti-TIM-3

(GSK4069889A/Cobolimab)

Anti-LAG-3

(GSK40974386)

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 $75.0 million in revenue under this agreement during the year ended December 31, 2020, of which $60.0 million is related to terms under Amendment No. 3 to the GSK Agreement that were satisfied and $15.0 million in milestone revenue related to two milestones. We recognized $8.0 million during the year ended December 31, 2019 related to two milestones. We recognized $5.0 million during the year ended December 31, 2018 related to one milestone.

Antibody Generation Agreement with Bristol-Myers Squibb

In December 2011, we entered into a license and collaboration agreement (the “BMS Agreement”) with Celgene, now a part of Bristol-Myers Squibb (Celgene and Bristol-Myers Squibb are hereinafter referred to, collectively, as “BMS”), to develop therapeutic antibodies against multiple targets. We granted BMS 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 BMS Agreement provided for an upfront payment of $6.0 million from BMS, 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, BMS, is a customer. We identified the following material promises under the BMS 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 BMS, BMS’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 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 December 31, 2020, the transaction price of the BMS Agreement 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 BMS’s 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 intellectual property license granted to BMS 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 December 31, 2020 under the BMS Agreement are as follows:


	Anti-PD-1 (CC-90006)
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 years ended December 31, 2020, 2019, and 2018.

Notes Payable	12 Months Ended
Notes Payable	Dec. 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 the Term Loans 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 due at the earlier of prepayment or the maturity date of the Term Loans. The deferred costs and the final payment fee were amortized to interest expense over the expected term of the Term A Loans using the effective interest method.

Fair Value Measurements and Available for Sale Investments

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

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 Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
At December 31, 2020
Money market funds(1)	$	188,297	$	188,297	$	—	$	—
Mutual funds(1)	57,153		57,153		—		—
U.S. Treasury securities(2)	107,697		107,697		—		—
Certificates of deposit(2)	2,436		—		2,436		—
Agency securities(2)	21,169		—		21,169		—
Commercial and corporate obligations(2)	29,441		—		29,441		—

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 December 31, 2020 and December 31, 2019 are presented below:


	December 31, 2020				December 31, 2019
(in thousands)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
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 December 31, 2020 are as follows:


(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
Agency securities(1)	$	21,169	$	1	$	(1)	$	21,169
Certificates of deposit(2)	2,427		9		—		2,436
Commercial and corporate obligations(3)	29,414		28		(1)		29,441
US Treasury securities(4)	107,530		170		(3)		107,697
Total available-for-sale investments	$	160,540	$	208	$	(5)	$	160,743

(1) Of our outstanding agency securities, $10.0 million have maturity dates of less than one year and $11.2 million have a maturity date of between one to two years as of December 31, 2020.

(2) Of our outstanding certificates of deposit, $1.1 million have a maturity date of less than one year and $1.3 million have a maturity date of between one to two years as of December 31, 2020.

(3) Of our outstanding commercial and corporate obligations, $29.4 million have maturity dates of less than one year and $0.0 million have a maturity date of between one to two years as of December 31, 2020.

(4) Of our outstanding U.S. Treasury securities, $102.7 million have maturity dates of less than one year and $5.0 million have a maturity date of between one to two years as of December 31, 2020.

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 December 31, 2019 are as follows:


(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
Agency securities(1)	$	33,543	$	80	$	—	$	33,623
Certificates of deposit(2)	5,381		47		—		5,428
Commercial and corporate obligations(3)	121,809		225		(4)		122,030
US Treasury securities(4)	96,236		200		(2)		96,434
Total available-for-sale investments	$	256,969	$	552	$	(6)	$	257,515

(1) Of our outstanding agency securities, $16.5 million have maturity dates of less than one year and $17.1 million have a maturity date of between one to two years as of December 31, 2019.

(2) Of our outstanding certificates of deposit, $4.6 million have a maturity date of less than one year and $0.8 million have a maturity date of between one to two years as of December 31, 2019.

(3) Of our outstanding commercial and corporate obligations, $111.1 million have maturity dates of less than one year and $10.9 million have a maturity date of between one to two years as of December 31, 2019.

(4) Of our outstanding U.S. Treasury securities, $70.9 million have maturity dates of less than one year and $25.5 million have a maturity date of between one to two years as of December 31, 2019.

The following tables present gross unrealized losses and fair values for those investments that were in an unrealized loss position as of December 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:


	December 31, 2020
	Less than 12 Months				12 Months or Greater				Total
(in thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Agency securities	$	4,999	$	(1)	$	—	$	—	$	4,999	$	(1)
Commercial and corporate obligations	6,503		(1)		2,399		—		8,902		(1)
US Treasury Securities	35,211		(3)		—		—		35,211		(3)
Total	$	46,713	$	(5)	$	2,399	$	—	$	49,112	$	(5)


	December 31, 2019
	Less than 12 Months				12 Months or Greater				Total
(in thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
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)

As of December 31, 2020 and 2019, unrealized losses on available-for-sale investments were not material, and accordingly, no allowance for credit losses were recorded.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stockholders' Equity

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Stockholders' Equity

Stockholders’ Equity

Common Stock

Of the 500,000,000 shares of common stock authorized, 27,355,575 shares were issued and outstanding as of December 31, 2020. Common stock reserved for future issuance upon the exercise, issuance or conversion of the respective equity instruments at December 31, 2020 are as follows:


Issued and Outstanding:
Stock options			2,920,700

Shares Reserved For:
2017 Equity Incentive Plan			2,986,101
2017 Employee Stock Purchase Plan			997,682
Total			6,904,483

Equity Incentive Plans

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

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 (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. 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 stock option award has a maximum term of 10 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 year ended December 31, 2020 is as follows:


	Shares Subject to Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020	3,039,880	$	29.40
Granted	539,825	$	19.13
Exercises	(100,493)	$	4.94
Forfeitures and cancellations	(558,512)	$	38.13
Outstanding at December 31, 2020	2,920,700	$	26.67	7.29	$	17,434
Exercisable at December 31, 2020	1,606,744	$	26.56	5.93	$	12,326

Total cash received from the exercise of stock options was approximately $0.5 million during the year ended December 31, 2020.

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:


		Year Ended December 31,

		2020			2019			2018
Risk-free interest rate		0.5	%		2.0	%		2.7	%
Expected volatility		90.2	%		77.98	%		67.7	%
Expected dividend yield		—	%		—	%		—	%
Expected term (in years)		6.25			6.25			6.25
Weighted average grant date fair value per share	$	14.51		$	21.99		$	61.41

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:


	Year Ended December 31,
(in thousands)		2020		2019		2018
Research and development		$	4,122	$	5,564	$	3,371
General and administrative		7,377		6,847		6,590
Total		$	11,499	$	12,411	$	9,961

At December 31, 2020, there was $22.9 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 2.92 years.

Australia Research and Development Tax Incentive

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Australia Research and Development Tax Incentive

Australia Research and Development Tax Incentive Our Australian subsidiary, which conducts core research and development activities on our behalf, was eligible to receive a 43.5% refundable tax incentive for qualified research and development activities during fiscal years 2019 and 2018. We were no longer eligible to receive the refundable tax incentive during fiscal year ending 2020. For the years ended December 31, 2019 and 2018, $0.0 million and $0.1 million, respectively, were recorded as a reduction to research and development expenses in the consolidated statements of operations and comprehensive loss. We received approximately $0.0 million and $0.2 million in cash during the years ended December 31, 2020 and 2019, respectively, related to the tax incentive. As of December 31, 2020, we had no remaining tax incentive receivable from the Australian government.Income Taxes

The components of loss before income tax benefit consist of the following:


	Year Ended December 31,
(in thousands)	2020		2019		2018
U.S.	$	(19,832)	$	(97,187)	$	(61,193)
Foreign	(99)		(301)		(655)
Consolidated net loss before income taxes	$	(19,931)	$	(97,488)	$	(61,848)

Significant components of our deferred tax assets and liabilities are as follows:


	December 31,
(in thousands)	2020		2019
Deferred Tax Assets:
Net operating loss carryforwards	$	57,772	$	55,722
Research and development credits	17,614		14,244
Equity compensation	5,329		4,067
Other, net	769		799
Total deferred tax assets	81,484		74,832
Deferred Tax Liabilities:
Fixed assets	(150)		(349)
Total deferred tax liabilities	(150)		(349)
Net deferred tax assets	81,334		74,483
Less: valuation allowance	(81,334)		(74,483)
Deferred tax assets, net of valuation allowance	$	—	$	—

We have recorded a full valuation allowance against our net deferred tax assets due to the uncertainty surrounding the realization of such assets. Management has determined it more likely than not that the deferred tax assets are not realizable due to our historical loss position.

At December 31, 2020, we had federal and state net operating loss carryforwards, or NOLs, of $248.4 million and $64.2 million, respectively. The federal and state NOLs generated prior to 2018 will both begin to expire in 2028, unless previously utilized. The federal NOL includes $188.4 million of net operating losses generated in 2018 and after. Federal net operating losses generated in 2018 and after carryover indefinitely and may generally be used to offset up to 80% of future taxable income. At December 31, 2020, we had federal and California research tax credit carryforwards of approximately $14.3 million and $8.9 million, respectively. The federal research tax credit carryforwards will begin to expire in 2026 and the California state credits carryforward indefinitely. We also have foreign tax losses of $3.4 million, which will carry forward indefinitely, subject to a continuity of ownership test.

The above NOL carryforward and the federal and state research tax credit carryforwards may be subject to an annual limitation under section 382 and 383 of the Internal Revenue Code of 1986, as amended (the “Code”), and similar state provisions if we experience one or more ownership changes which would limit the amount of NOL and tax credit carryforwards that can be utilized to offset future taxable income and tax, respectively. In general, an ownership change as defined by Section 382 and 383, results from transactions increasing ownership of certain stockholders or public groups in the stock of the corporation by more than 50 percentage points over a three-year period. In September 2015, we completed a Section 382 analysis through December 31, 2014 and determined that there was an ownership change in 2007 that may limit the utilization of approximately $5.3 million and $5.4 million in federal and state NOLs, respectively, and $0.2 million in both federal and state research tax credits. We extended the analysis period of the study through December 31, 2018, noting an ownership change in 2017 which may limit the use of our net operating losses. Our use of federal NOL carryforward could be limited further by the provisions of Section 382 of the U.S. Internal Revenue Code of 1986, as amended, depending upon the timing and amount of additional equity securities that we have issued or will issue. State NOL carryforwards may be similarly limited. If a change in ownership were to have occurred, NOL and tax credits carryforwards could be eliminated or restricted. If eliminated the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by ownership changes, if any, will not impact our effective tax rate.

The following is a reconciliation of the expected statutory federal income tax provision to our actual income tax provision:


	Year Ended December 31,
(in thousands)	2020		2019		2018
Expected income tax benefit at federal statutory tax rate	$	(4,186)	$	(20,473)	$	(12,988)
State income taxes, net of federal benefit	(21)		(377)		(166)
Permanent items	18		34		17
Equity compensation (1)	871		(1,122)		(6,693)
Research and development expenditure	—		—		63
Refundable AMT credit	—		—		(139)
Return to provision adjustment	(11)		(661)		60
Rate differential	40		(53)		155
Research credits	(3,389)		(4,405)		(4,393)

Change in the valuation allowance	6,678		26,905		23,892
Income tax benefit	$	—	$	(152)	$	(192)

(1) Includes non-deductible stock-based compensation and excess tax benefits from stock-based compensation. During 2020, our tax provision includes $0.0 of excess tax benefits associated with the exercise of non-qualified stock options and $0.2 associated with the disqualifying dispositions of incentive stock options. During 2019, our tax provision includes $1.1 million of excess tax benefits associated with the exercise of non-qualified stock options and $0.3 million associated with the disqualifying dispositions of incentive stock options. During 2018, our tax provision includes $4.9 million of excess tax benefits associated with the exercise of non-qualified stock options and $2.2 million associated with the disqualifying dispositions of incentive stock options.

We recognize a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Income tax positions must meet a more likely than not recognition at the effective date to be recognized. At December 31, 2020 and 2019, we had no unrecognized tax benefits that, if recognized and realized, would affect the effective tax rate due to the valuation allowance against deferred tax assets. The following table summarizes the activity related to our unrecognized tax benefits:


	Year Ended December 31,
(in thousands)	2020		2019
Balance at the beginning of the year	$	3,146	$	1,812
Increase related to prior year tax positions	—		168
Increase related to current year tax positions	898		1,166
Balance at the end of the year	$	4,044	$	3,146

If recognized, these amounts would not affect our effective tax rate, since they would be offset by an equal corresponding adjustment in the deferred tax asset valuation allowance. We do not anticipate there will be a significant change in unrecognized tax benefits within the next 12 months.

Our policy is to recognize interest and penalties related to income tax matters in the provision for income taxes. At December 31, 2020 and 2019, there were no interest or penalties on uncertain tax benefits.

We file income tax returns in the United States, California and Australia. Due to our losses incurred, we are essentially subject to income tax examination by tax authorities from inception to date.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Employee Benefit Plan	12 Months Ended
Employee Benefit Plan	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit PlanWe have a defined contribution 401(k) plan available to eligible employees. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under U.S. federal tax regulations. During 2020 and 2019, we elected to match 50% of an employee’s contributions up to 6% of the employees’ eligible salary with a maximum annual match limit of $6,000. For the years ended December 31, 2020, and 2019, we incurred approximately $0.5 million and $0.3 million, respectively of costs related to the 401(k) plan. There were no employer contributions to the plan during the year ended December 31, 2018.

- Definition

The entire disclosure for retirement benefits.

+ References

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+ Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Operating Leases

On November 11, 2020, we entered into an agreement to terminate our sublease (the “Sublease Termination”) with Trex Enterprises Corporation, with respect to facilities in the building at 10455 Pacific Center Court in San Diego, California (the “10455 Building”). The terms of the original sublease with Trex provided for a November 12, 2021 lease expiration. Under the Sublease Termination, we agreed to terminate the sublease agreement on December 15, 2020 with no associated penalty. We recorded a non-cash gain of approximately $0.1 million as other income (expense), in connection with the write-off of the lease liability and corresponding ROU asset. As of December 31, 2020, there was no lease liability and corresponding ROU asset related to the 10455 Building Lease.

As of December 31, 2020, we still maintain the non-cancellable office lease for our facilities at 10421 Pacific Center Court in San Diego, California, which expires on August 31, 2021. Our lease payments are fixed, and we recognize lease expense for 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	December 31, 2020		December 31, 2019
Operating ROU assets	Other long-term assets	$	344	$	1,402
Operating lease liabilities	Other current liabilities	342		871
Operating lease liabilities	Other long-term liabilities	—		654

The following costs are included in our cash flow statement (in thousands):


Leases	Classification on the Cash Flow	Year Ended December 31, 2020		Year Ended December 31, 2019
Operating lease cost	Operating	$	865	$	879
Cash paid for amounts included in the measurement of lease liabilities	Operating	938		937

Rent expense was $0.7 million during the year ended December 31, 2018 under ASC 840.

At December 31, 2020, the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows:


Years Ending December 31, (in thousands)
2021	$	352
2022	—
2023	—
2024	—
2025	—
Thereafter	—
Total minimum payments required	$	352
Less: Imputed interest	(10)
Present value of lease liabilities	$	342

On May 4, 2020, we entered into a lease agreement (the “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 for a term of 124 months, beginning on April 1, 2021 or at the completion of leasehold improvements. The Lease liability and corresponding ROU asset will be recorded at lease commencement date, which we anticipate to be April 1, 2021. 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 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% annually. Under the Lease Agreement, we are also responsible for our pro rata share of real estate taxes, building insurance, maintenance, direct expenses, and utilities. As of December 31, 2020, we have recorded $0.2 million in prepaid rent and $0.3 million as a security deposit in accordance with the terms of the Lease Agreement.

At December 31, 2020, the future minimum annual obligations for the Lease Agreement in excess of one year are as follows (in thousands):


Years Ending December 31,
2021	$	568
2022	2,328
2023	2,397
2024	2,469
2025	2,543
Thereafter	15,420
Total minimum payments required	$	25,725

License Agreements

We have certain obligations under licensing agreements with third parties that are contingent upon achieving various development, regulatory and commercial milestones. Pursuant to these license agreements, we are required to make milestone payments if certain development, regulatory and commercial sales milestones are achieved. Also, pursuant to the terms of each of these license agreements, when and if commercial sales of a product commence, we will pay royalties to our licensors on net sales of the respective products.

Certain of the licensing agreements require guaranteed minimum annual payments. Terms of the licensing agreements generally range from the remaining life of the patent up to 19 years and, in some cases, may be subject to earlier termination by either party upon specified circumstances.

Total expense incurred under all collaborative licensing agreements for upfront, milestone and royalty payments were $0.2 million, $0.5 million and $0.3 million during the years ended December 31, 2020, 2019 and 2018, respectively. Total cash paid under these agreements was $0.3 million, $0.1 million, and $0.2 million during the years ended December 31, 2020, 2019, and 2018, respectively.

Future minimum annual obligations under all such license agreements will be $0.2 million in aggregate during 2021, and thereafter. These obligations are payable through ten years from the first commercial sale, if any, or expiration of the last patent to expire, the dates of which are not determinable at this time.

Other Commitments and Contingencies

We have entered into agreements with certain vendors for the provision of goods and services, which includes manufacturing services with contract manufacturing organizations and development services with contract research organizations. These agreements may include certain provisions for purchase obligations and termination obligations that could require payments for the cancellation of committed purchase obligations or for early termination of the agreements. The amount of the cancellation or termination payments vary and are based on the timing of the cancellation or termination and the specific terms of the agreement.

Guarantees and Indemnifications

We enter into standard indemnification arrangements in the ordinary course of business. Pursuant to certain of these arrangements, we indemnify, hold harmless, and agree to reimburse the indemnified parties for losses suffered or incurred by the indemnified party for third-party claims in connection with our breach of the agreement, our negligence or willful misconduct in connection with the agreement, or any trade secret, copyright, patent or other intellectual property infringement claim with respect to our technology. The term of these indemnification arrangements is generally perpetual. The maximum potential amount of future payments we could be required to make under these agreements is not determinable because it involves claims that may be made against us in the future, but have not yet been made.

We indemnify our officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving in such capacity, as permitted under Delaware law, in accordance with our certificate of incorporation and bylaws, and pursuant to agreements providing for indemnification entered into with our officers and directors. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity.

The maximum amount of potential future indemnification of directors and officers is unlimited; however, we currently hold director and officer liability insurance. This insurance allows the transfer of risk associated with our exposure and may enable us to recover a portion of any future amounts paid.

We believe that the fair value of these indemnification obligations is minimal. Accordingly, we have not recognized any liabilities relating to these obligations for any period presented.

Letter of Credit

At December 31, 2020 and 2019, we were contingently liable for a standby letter of credit issued by a commercial bank for $60,000 for security on our lease. A restricted cash account with these amounts was held as cash collateral for the letter of credit.

Litigation

On March 25, 2020, a putative securities class action was filed in the United States District Court for the Southern District of California naming the Company and certain of its current or former officers as defendants. The complaint purports to assert claims under Section 10(b) of the 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 (the “Class Period”). An amended complaint was filed on September 30, 2020 alleging that, during the Class Period, the defendants made material misrepresentations or omissions regarding our etokimab product candidate 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 plaintiff’s allegations are without merit and intend to vigorously defend against the claims. Because the Company is in the early stages of this litigation matter, we are unable to estimate a reasonably possible loss or range of loss, if any, that may result from these matters. On September 1, 2020, a related shareholder derivative complaint was filed based on allegations substantially similar to those in the class action, and asserting claims against current or former officers and directors for contribution under Sections 10(b) and 21D of the Exchange Act, breach of fiduciary duty, unjust enrichment and corporate waste. On January 28, 2021, this derivative action was voluntarily dismissed without prejudice.

From time to time, we may be involved in legal proceedings arising in the ordinary course of our business. We investigate these claims as they arise and accrue estimates for resolution of legal and other contingencies when losses are probable and estimable. Regardless of outcome, litigation can have an adverse impact on us due to defense and settlement costs, diversion of management resources, negative publicity and reputational harm, and other factors.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

The components of loss before income tax benefit consist of the following:


	Year Ended December 31,
(in thousands)	2020		2019		2018
U.S.	$	(19,832)	$	(97,187)	$	(61,193)
Foreign	(99)		(301)		(655)
Consolidated net loss before income taxes	$	(19,931)	$	(97,488)	$	(61,848)

Significant components of our deferred tax assets and liabilities are as follows:


	December 31,
(in thousands)	2020		2019
Deferred Tax Assets:
Net operating loss carryforwards	$	57,772	$	55,722
Research and development credits	17,614		14,244
Equity compensation	5,329		4,067
Other, net	769		799
Total deferred tax assets	81,484		74,832
Deferred Tax Liabilities:
Fixed assets	(150)		(349)
Total deferred tax liabilities	(150)		(349)
Net deferred tax assets	81,334		74,483
Less: valuation allowance	(81,334)		(74,483)
Deferred tax assets, net of valuation allowance	$	—	$	—

The following is a reconciliation of the expected statutory federal income tax provision to our actual income tax provision:


	Year Ended December 31,
(in thousands)	2020		2019		2018
Expected income tax benefit at federal statutory tax rate	$	(4,186)	$	(20,473)	$	(12,988)
State income taxes, net of federal benefit	(21)		(377)		(166)
Permanent items	18		34		17
Equity compensation (1)	871		(1,122)		(6,693)
Research and development expenditure	—		—		63
Refundable AMT credit	—		—		(139)
Return to provision adjustment	(11)		(661)		60
Rate differential	40		(53)		155
Research credits	(3,389)		(4,405)		(4,393)

Change in the valuation allowance	6,678		26,905		23,892
Income tax benefit	$	—	$	(152)	$	(192)


	Year Ended December 31,
(in thousands)	2020		2019
Balance at the beginning of the year	$	3,146	$	1,812
Increase related to prior year tax positions	—		168
Increase related to current year tax positions	898		1,166
Balance at the end of the year	$	4,044	$	3,146

We file income tax returns in the United States, California and Australia. Due to our losses incurred, we are essentially subject to income tax examination by tax authorities from inception to date.

- Definition

+ References + Details

Subsequent Event	12 Months Ended
Subsequent Event	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event A second BLA submitted by GSK was accepted by the FDA during the first quarter of 2021 for dostarlimab in pan-deficient mismatch repair tumors (“PdMMRT”),” triggering a milestone payment to us of $10.0 million.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or U.S. GAAP.
Basis of Consolidation	Basis of ConsolidationThe 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	Use of Estimates The preparation of the accompanying consolidated financial statements in conformity with U.S. GAAP requires our 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 or treat it, 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.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with a maturity at date of purchase of three months or less to be cash equivalents. Cash equivalents consist primarily of money market and mutual funds with original maturities of 90 days or less.
Short Term and Long Term Investments	Short-Term and Long-Term InvestmentsAll investments have been classified as “available-for-sale” and are carried at fair value as determined based upon quoted market prices or pricing models for similar securities at period end. Investments with contractual maturities less than 12 months at the balance sheet date are considered short-term investments. Those investments with contractual maturities 12 months or greater at the balance sheet date are considered long-term investments. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss). We review our portfolio of available-for-sale debt securities, using both quantitative and qualitative factors, to determine if declines in fair value below cost have resulted from a credit-related loss or other factors. If the decline in fair value is due to credit-related factors, a loss is recognized in net income, whereas if the decline in fair value is not due to credit-related factors, the loss is recorded in other comprehensive income (loss).
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject us to a concentration of credit risk consist of cash and cash equivalents and certain investments in money market funds, certificates of deposit, agency securities, commercial obligations and U.S. Treasury securities. Bank deposits are diversified between three financial institutions and these deposits may exceed insured limits. We are exposed to credit risk in the event of default by the financial institutions holding our cash and cash equivalents and issuers of investments that are recorded on our consolidated balance sheets. We mitigate our risk by investing in high-grade instruments and limiting the concentration in any one issuer, which limits our exposure.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Expenditures for major additions and betterments are capitalized. Maintenance and repairs are charged to operations as incurred. Depreciation and amortization are calculated using the straight-line method over the estimated useful lives of the assets, which range from three to seven years. Leasehold improvements are amortized using the straight line method over the term of the lease. Upon sale or retirement of property and equipment, the related cost and accumulated depreciation are removed from the accounts and any gain or loss is reflected in operations.
Long Lived Assets	Long Lived Assets Long-lived assets, consisting of property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable based on undiscounted cash flows. If long-lived assets are impaired, an impairment loss is recognized and is measured as the amount by which the carrying value exceeds the estimated fair value of the assets.
Leases	Leases Our leases consist of leases for office space that are classified as operating leases. We determine if an arrangement is a lease at inception. Rent expense is recognized on a straight-line basis. When an operating lease includes rent abatements or requires fixed escalations of the minimum lease payments, the aggregate rental expense is recognized on a straight-line basis over the term of the lease. When an operating lease includes lease incentives such as leasehold improvement allowances, the lease incentive is included in the right-of-use (“ROU”) asset. For leases that have greater than a 12-month lease term, the ROU assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term. For this purpose, we consider only payments that are fixed and determinable at the time of commencement. As our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. We account for fixed lease components separately from non-lease components.We keep leases with an initial term of 12 months or less off the balance sheet and recognize the associated lease payments in the consolidated statements of operations on a straight-line basis over the lease term.
Revenue Recognition	Revenue Recognition Revenue is recognized in accordance with revenue recognition accounting guidance, which utilizes five basic steps to determine whether revenue can be recognized and to what extent: (i) identify the contract with a customer; (ii) identify the performance obligation; (iii) determine the transaction price; (iv) allocate the transaction price; and (v) determine the recognition period. Performance Obligations. We evaluate deliverables on a contract-by-contract basis to determine whether each deliverable represents a good or service that is distinct or has the same pattern of transfer as other deliverables. A deliverable is considered distinct if the customer can benefit from the good or service independently of other goods/services either in the contract or that can be obtained elsewhere, without regard to contract exclusivity, and the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contact. If the deliverable is not considered distinct, we combine such deliverables and account for them as a single performance obligation. We allocate the consideration to each deliverable at the inception of the arrangement based on the transaction price. Our performance obligations may include the following: •License Arrangements. The performance obligations under our collaboration and license agreements generally include exclusive or nonexclusive licenses to one or more products generated using our technologies. Licenses for multiple antibodies within a single contract are generally combined as they have substantially the same pattern of transfer to the customer. Historically, our licenses have held no value to the customer, as the antibodies were in the discovery phase and required our expertise for further development. Accordingly, licenses are not considered distinct. •Research and Development Services. The performance obligations under our collaboration and license agreements generally include research and development services we perform on behalf of or with our collaborators. As discussed within license arrangements above, our licenses have historically held no value without the research and development services we provide. As we generally only provide research and development services for internally generated antibodies that require a license to be utilized by a third party, our research and development services are not considered distinct. •Steering Committee Meetings. The performance obligations under our collaboration and license agreements may also include our participation in a steering committees, which allows us to direct the progression of our discovery programs. As these steering committees would not occur or benefit the customer without the use of our licenses, these are not considered distinct. We recognize consideration allocated to a performance obligation as the performance obligation is satisfied, and the determination as to whether consideration is recognized over time or at a point in time is made upon contract inception. For our collaboration agreements, this is generally over the period in which research and development services have been performed. Transaction Price. Our collaboration and license agreements generally include both fixed and variable consideration. Fixed payments, such as those for upfront fees are included in the transaction price at contract value, while variable consideration such as reimbursement for research and development services, milestone and royalty payments are estimated and then evaluated for constraints upon inception of the contract and evaluated on a quarterly basis thereafter. Research and development services are updated for actual invoices. Given the nature of our agreements, milestones are estimated using the most likely amount and are evaluated on a quarterly basis. Upon commercialization, royalty payments will be recognized in the period incurred.
Research and Development Expenses	Research and Development Expenses Research and development costs primarily include third-party clinical and preclinical research and development services such as manufacturing, laboratory and related supplies, salaries and personnel-related costs, in-licensing fees, outside services, and an allocation of information technology, and facility overhead costs. Costs associated with research and development activities are expensed as incurred. We account for nonrefundable advance payments for goods and services that will be used in future research and development activities as expense when the service has been performed or when the goods have been received. We estimate research and development costs incurred during the period, which impacts the amount of accrued expenses and prepaid balances related to such costs as of each balance sheet date. This process involves reviewing open contracts and purchase orders, communicating with our personnel and service providers to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued expenses as of each balance sheet date based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments if necessary. The significant estimates in our accrued research and development expenses include the costs incurred for services performed by our vendors in connection with research and development activities for which we have not yet been invoiced. Upfront and milestone payments incurred under our in-licensing agreements are expensed as acquired in-process research and development in the period in which they are incurred, provided that the technology or method has no alternative future use.
Share-Based Compensation	Stock-Based Compensation We recognize stock-based compensation expense using a fair-value-based method for costs related to all share-based payments, including stock options. Stock-based compensation cost for stock options granted to our employees and directors is measured at the grant date based on the fair-value of the award which is estimated using the Black-Scholes option-pricing model, and is recognized as expense over the requisite service period on a straight-line basis. We recognize forfeitures in the period in which forfeiture occur and record stock-based compensation expense as though all awards are expected to vest. No tax benefits for stock-based compensation have been recognized in the statements of changes in stockholders’ equity or cash flows. We have not recognized, and do not expect to recognize in the near future, any tax benefit related to stock-based compensation cost as a result of our full valuation allowance on net deferred tax assets and net operating loss carryforwards.
Income Taxes	Income Taxes We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax basis of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to be recovered or settled. Realization of deferred tax assets is dependent upon future taxable income. A valuation allowance is recognized if it is more likely than not that some portion or all of a deferred tax asset will not be realized based on the weight of available evidence, including expected future earnings. We recognize an uncertain tax position in our consolidated financial statements when we conclude that a tax position is more likely than not to be sustained upon examination based solely on technical merits. Only after a tax position passes the first step of recognition will measurement be required. Under the measurement step, the tax benefit is measured as the largest amount of benefit that is more likely than not to be realized upon effective settlement. This is determined on a cumulative probability basis. The full impact of any change in recognition or measurement is reflected in the period in which such change occurs. We have elected to accrue any interest or penalties related to income taxes as part of our income tax expense.
Foreign Currency of Foreign Operations	Functional Currency of Foreign Operations Our Australian subsidiary operates in a U.S. dollar functional currency environment. Assets and liabilities of our foreign subsidiary that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets and capital accounts, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Expenses are generally remeasured at monthly foreign currency exchange rates which approximate average rates in effect during each period. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), net, in the consolidated statements of operations.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) represents all changes in stockholders’ equity except those resulting from distributions to stockholders. Our unrealized gain and losses on available for sale investments represent the only component of other comprehensive income (loss) that is excluded from the reported net income (loss).
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.
Accounting Pronouncements Recently Adopted	Accounting Pronouncements Recently Adopted In December 2019, the Financial Accounting Standards Board (the “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 COVID-19 pandemic on expected credit losses. In February 2016, the FASB, issued ASU 2016-02, Leases (Topic 842), which requires that lessees recognize a ROU asset and a related lease liability on the balance sheet for all leases with a term longer than 12 months. Topic 842 was subsequently amended by ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842; ASU 2018-10, Codification Improvements to Topic 842, Leases; ASU 2018-11, Targeted Improvements; and ASU 2019-01, Leases (Topic 842): Codification Improvements. ASU 2016-02 became effective for our annual reporting period beginning January 1, 2019, including interim periods thereafter. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. We adopted this standard on January 1, 2019 and used the effective date as our date of initial application. Upon adoption, we elected the package of transition practical expedients, which allowed us to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. We also made an accounting policy election to not recognize leases with an initial term of 12 months or less within our consolidated balance sheets and to recognize those lease payments on a straight-line basis in our consolidated statements of operations over the lease term. Adoption of the new standard resulted in the recording of operating lease ROU assets and lease liabilities of approximately $2.1 million and $2.3 million as of January 1, 2019, respectively related to our real estate leases. Adoption of this new standard did not have a material impact on our consolidated statements of operations or cash flows.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Outstanding Potentially Dilutive Securities Excluded in the Calculation of Diluted Net Loss Per Share


	Year Ended December 31,
(in thousands)		2020	2019	2018

Options to purchase common stock		2,901	2,462	2,451

Balance Sheet Accounts and Supplemental Disclosures (Tables)

12 Months Ended

Dec. 31, 2020

Balance Sheet Related Disclosures [Abstract]

Property and Equipment

Property and equipment consist of the following:


(in thousands)	December 31, 2020		December 31, 2019
Laboratory equipment	$	5,225	$	4,911
Office furniture and equipment	976		811
Leasehold improvements	527		575
Property and equipment, gross	6,728		6,297
Less: accumulated depreciation and amortization	(4,945)		(4,679)
Total property and equipment, net	$	1,783	$	1,618

Schedule of Accrued Expenses

Accrued expenses consist of the following:


(in thousands)	December 31, 2020		December 31, 2019
Accrued compensation and related expenses	$	3,688	$	2,152
Accrued professional fees	408		435
Accrued research and development expenses	10,936		8,196
Other	230		269
Total accrued expenses	$	15,262	$	11,052

Collaborative Research and Development Agreements (Tables)

12 Months Ended

Dec. 31, 2020

Revenue Recognition [Abstract]

Schedule of Milestones Achieved

Milestones recognized through December 31, 2020 under the GSK Agreement are as follows:

Anti-PD-1

(GSK4057190A/Dostarlimab)

Anti-TIM-3

(GSK4069889A/Cobolimab)

Anti-LAG-3

(GSK40974386)

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 December 31, 2020 under the BMS Agreement are as follows:


	Anti-PD-1 (CC-90006)
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 Available for Sale Investments (Tables)

12 Months Ended

Dec. 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 Value		Quoted Market Prices for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
At December 31, 2020
Money market funds(1)	$	188,297	$	188,297	$	—	$	—
Mutual funds(1)	57,153		57,153		—		—
U.S. Treasury securities(2)	107,697		107,697		—		—
Certificates of deposit(2)	2,436		—		2,436		—
Agency securities(2)	21,169		—		21,169		—
Commercial and corporate obligations(2)	29,441		—		29,441		—

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 December 31, 2020 and December 31, 2019 are presented below:


	December 31, 2020				December 31, 2019
(in thousands)	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Notes payable	$	—	$	—	$	1,375	$	1,365

Available-for-sale Investments


(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
Agency securities(1)	$	21,169	$	1	$	(1)	$	21,169
Certificates of deposit(2)	2,427		9		—		2,436
Commercial and corporate obligations(3)	29,414		28		(1)		29,441
US Treasury securities(4)	107,530		170		(3)		107,697
Total available-for-sale investments	$	160,540	$	208	$	(5)	$	160,743

(1) Of our outstanding agency securities, $10.0 million have maturity dates of less than one year and $11.2 million have a maturity date of between one to two years as of December 31, 2020.

(2) Of our outstanding certificates of deposit, $1.1 million have a maturity date of less than one year and $1.3 million have a maturity date of between one to two years as of December 31, 2020.

(4) Of our outstanding U.S. Treasury securities, $102.7 million have maturity dates of less than one year and $5.0 million have a maturity date of between one to two years as of December 31, 2020.


(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Total Fair Value
Agency securities(1)	$	33,543	$	80	$	—	$	33,623
Certificates of deposit(2)	5,381		47		—		5,428
Commercial and corporate obligations(3)	121,809		225		(4)		122,030
US Treasury securities(4)	96,236		200		(2)		96,434
Total available-for-sale investments	$	256,969	$	552	$	(6)	$	257,515

(1) Of our outstanding agency securities, $16.5 million have maturity dates of less than one year and $17.1 million have a maturity date of between one to two years as of December 31, 2019.

(2) Of our outstanding certificates of deposit, $4.6 million have a maturity date of less than one year and $0.8 million have a maturity date of between one to two years as of December 31, 2019.

(4) Of our outstanding U.S. Treasury securities, $70.9 million have maturity dates of less than one year and $25.5 million have a maturity date of between one to two years as of December 31, 2019.

Schedule of Unrealized Loss and Fair Values in a Loss Position


	December 31, 2020
	Less than 12 Months				12 Months or Greater				Total
(in thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
Agency securities	$	4,999	$	(1)	$	—	$	—	$	4,999	$	(1)
Commercial and corporate obligations	6,503		(1)		2,399		—		8,902		(1)
US Treasury Securities	35,211		(3)		—		—		35,211		(3)
Total	$	46,713	$	(5)	$	2,399	$	—	$	49,112	$	(5)


	December 31, 2019
	Less than 12 Months				12 Months or Greater				Total
(in thousands)	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
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)

12 Months Ended

Dec. 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 December 31, 2020 are as follows:


Issued and Outstanding:
Stock options			2,920,700

Shares Reserved For:
2017 Equity Incentive Plan			2,986,101
2017 Employee Stock Purchase Plan			997,682
Total			6,904,483

Equity Incentive Plans (Tables)

12 Months Ended

Dec. 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 year ended December 31, 2020 is as follows:


	Shares Subject to Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020	3,039,880	$	29.40
Granted	539,825	$	19.13
Exercises	(100,493)	$	4.94
Forfeitures and cancellations	(558,512)	$	38.13
Outstanding at December 31, 2020	2,920,700	$	26.67	7.29	$	17,434
Exercisable at December 31, 2020	1,606,744	$	26.56	5.93	$	12,326

Summary of Weighted Average Assumptions in Stock Option Valuations


		Year Ended December 31,

		2020			2019			2018
Risk-free interest rate		0.5	%		2.0	%		2.7	%
Expected volatility		90.2	%		77.98	%		67.7	%
Expected dividend yield		—	%		—	%		—	%
Expected term (in years)		6.25			6.25			6.25
Weighted average grant date fair value per share	$	14.51		$	21.99		$	61.41

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:


	Year Ended December 31,
(in thousands)		2020		2019		2018
Research and development		$	4,122	$	5,564	$	3,371
General and administrative		7,377		6,847		6,590
Total		$	11,499	$	12,411	$	9,961

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Schedule of ROU Assets and Lease Liabilities

Our balance sheet includes our ROU assets and lease liabilities as follows (in thousands):


Leases	Classification on the Balance Sheet	December 31, 2020		December 31, 2019
Operating ROU assets	Other long-term assets	$	344	$	1,402
Operating lease liabilities	Other current liabilities	342		871
Operating lease liabilities	Other long-term liabilities	—		654

Costs in Cash Flow Statement

The following costs are included in our cash flow statement (in thousands):


Leases	Classification on the Cash Flow	Year Ended December 31, 2020		Year Ended December 31, 2019
Operating lease cost	Operating	$	865	$	879
Cash paid for amounts included in the measurement of lease liabilities	Operating	938		937

Schedule of Future Minimum Annual Obligations

At December 31, 2020, the future minimum annual obligations under non-cancellable operating lease commitments in excess of one year are as follows:


Years Ending December 31, (in thousands)
2021	$	352
2022	—
2023	—
2024	—
2025	—
Thereafter	—
Total minimum payments required	$	352
Less: Imputed interest	(10)
Present value of lease liabilities	$	342

At December 31, 2020, the future minimum annual obligations for the Lease Agreement in excess of one year are as follows (in thousands):


Years Ending December 31,
2021	$	568
2022	2,328
2023	2,397
2024	2,469
2025	2,543
Thereafter	15,420
Total minimum payments required	$	25,725

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Components of Income/(Loss) before Income Tax Provision (Benefit)

The components of loss before income tax benefit consist of the following:


	Year Ended December 31,
(in thousands)	2020		2019		2018
U.S.	$	(19,832)	$	(97,187)	$	(61,193)
Foreign	(99)		(301)		(655)
Consolidated net loss before income taxes	$	(19,931)	$	(97,488)	$	(61,848)

Schedule of Components of Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities are as follows:


	December 31,
(in thousands)	2020		2019
Deferred Tax Assets:
Net operating loss carryforwards	$	57,772	$	55,722
Research and development credits	17,614		14,244
Equity compensation	5,329		4,067
Other, net	769		799
Total deferred tax assets	81,484		74,832
Deferred Tax Liabilities:
Fixed assets	(150)		(349)
Total deferred tax liabilities	(150)		(349)
Net deferred tax assets	81,334		74,483
Less: valuation allowance	(81,334)		(74,483)
Deferred tax assets, net of valuation allowance	$	—	$	—

Reconciliation of Expected Statutory Federal Income Tax Provision and Actual Income Tax Provision

The following is a reconciliation of the expected statutory federal income tax provision to our actual income tax provision:


	Year Ended December 31,
(in thousands)	2020		2019		2018
Expected income tax benefit at federal statutory tax rate	$	(4,186)	$	(20,473)	$	(12,988)
State income taxes, net of federal benefit	(21)		(377)		(166)
Permanent items	18		34		17
Equity compensation (1)	871		(1,122)		(6,693)
Research and development expenditure	—		—		63
Refundable AMT credit	—		—		(139)
Return to provision adjustment	(11)		(661)		60
Rate differential	40		(53)		155
Research credits	(3,389)		(4,405)		(4,393)

Change in the valuation allowance	6,678		26,905		23,892
Income tax benefit	$	—	$	(152)	$	(192)

Schedule of Activity Related to Unrecognized Tax Benefits

The following table summarizes the activity related to our unrecognized tax benefits:


	Year Ended December 31,
(in thousands)	2020		2019
Balance at the beginning of the year	$	3,146	$	1,812
Increase related to prior year tax positions	—		168
Increase related to current year tax positions	898		1,166
Balance at the end of the year	$	4,044	$	3,146

Description of the Business (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Sep. 28, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Warrant or Right [Line Items]
Common shares issued (in shares)	2,530,000
Share price (in dollars per share)	$ 94.46
Proceeds, net of underwriters' fees	$ 227,500	$ 0	$ 0	$ 227,476
Underwriters' option
Class of Warrant or Right [Line Items]
Common shares issued (in shares)	330,000

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) segment bank	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
Number of reportable segments \| segment	1
Restricted cash	$ 60,000	$ 60,000
Number of banks utilized for diversification of funds (in banks) \| bank	3
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-lived asset impairment charges	$ 0	0	$ 0
Operating ROU assets	344,000	$ 1,402,000		$ 2,100,000
Present value of lease liabilities	$ 342,000			$ 2,300,000
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, useful life	3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, useful life	7 years

Summary of Significant Accounting Policies - Summary of Potentially Dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Options to purchase common stock (in shares)	2,901	2,462	2,451

Balance Sheet Accounts and Supplemental Disclosures - Property and Equipment (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 15, 2020	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 6,728	$ 6,297
Less: accumulated depreciation and amortization		(4,945)	(4,679)
Total property and equipment, net		1,783	1,618
Loss on disposal of tenant improvements and certain equipment	$ 100	100
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross		5,225	4,911
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross		976	811
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross		$ 527	$ 575

Balance Sheet Accounts and Supplemental Disclosures - Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and related expenses	$ 3,688	$ 2,152
Accrued professional fees	408	435
Accrued research and development expenses	10,936	8,196
Other	230	269
Total accrued expenses	$ 15,262	$ 11,052

Collaborative Research and Development Agreements (Details)		1 Months Ended		3 Months Ended													12 Months Ended
	Jan. 01, 2021	Nov. 30, 2014 USD ($) target	Mar. 31, 2014 USD ($) target	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2020 USD ($) milestone	Dec. 31, 2019 USD ($) milestone	Dec. 31, 2018 USD ($) milestone	Dec. 31, 2011 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue																	$ 75,000,000	$ 8,000,000	$ 5,000,000
TESARO
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue																	$ 75,000,000.0	$ 8,000,000.0	$ 5,000,000.0
TESARO \| Collaborative Research and Development Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fee received		$ 2,000,000.0	$ 17,000,000.0
Number of outstanding research and development targets \| target		4	3
Milestone payments, contingent upon preclinical and clinical trial events (up to)		$ 18,000,000.0
Milestone payments, contingent upon certain U.S. and European regulatory submissions and approvals (up to)		90,000,000.0
Milestone payments, contingent upon achievement of specified levels of worldwide sales (up to)		$ 165,000,000.0
Agreement term following first commercial sale or expiration of the last to expire patent		12 years
Number of milestones achieved during period \| milestone																	2	2	1
TESARO \| Collaboration And Exclusive License Agreement \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognition multiple deliverable arrangements upfront fee receivable				$ 60,000,000.0													$ 60,000,000.0
Milestones achieved during period, amount																	1,100,000,000
TESARO \| Collaboration And Exclusive License Agreement \| Anti-PD-1 (GSK4057190A/Dostarlimab) \| Subsequent event
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty percent on net sales	1.00%
TESARO \| Completion of first in vivo toxicology studies using GLPs \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount																$ 1,000,000.0
TESARO \| Completion of first in vivo toxicology studies using GLPs \| Anti-TIM-3 (GSK4069889A/Cobolimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount															$ 1,000,000.0
TESARO \| Completion of first in vivo toxicology studies using GLPs \| Anti-LAG-3 (GSK40974386)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount												$ 1,000,000.0
TESARO \| IND clearance from the FDA \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount														$ 4,000,000.0
TESARO \| IND clearance from the FDA \| Anti-TIM-3 (GSK4069889A/Cobolimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount													$ 4,000,000.0
TESARO \| IND clearance from the FDA \| Anti-LAG-3 (GSK40974386)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount										$ 4,000,000.0
TESARO \| Phase 2 clinical trial initiation \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount										$ 3,000,000.0
TESARO \| Phase 2 clinical trial initiation \| Anti-TIM-3 (GSK4069889A/Cobolimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount									$ 3,000,000.0
TESARO \| Phase 2 clinical trial initiation \| Anti-LAG-3 (GSK40974386)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount						$ 3,000,000.0
TESARO \| Phase 3 clinical trial initiation - first indication \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount								$ 5,000,000.0									15,000,000.0
TESARO \| Phase 3 clinical trial initiation - second indication \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount							$ 5,000,000.0
TESARO \| Filing of the first NDA - first indication \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount					$ 10,000,000.0
TESARO \| Filing of the first MAA - first indication \| Anti-PD-1 (GSK4057190A/Dostarlimab)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestones achieved during period, amount					$ 5,000,000.0
BMS \| Collaborative Research and Development Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront license fee received																				$ 6,000,000.0
Collaboration revenue																	$ 0	$ 0	$ 0
Maximum milestone payments per target																				$ 53,000,000.0
BMS \| Completion of first in vivo toxicology studies using GLPs \| Anti-PD-1 (CC-90006)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment earned													$ 500,000
BMS \| Phase 1 clinical trial initiation \| Anti-PD-1 (CC-90006)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payment earned											$ 1,000,000.0

Notes Payable (Details) - Notes Payable to Banks	Dec. 24, 2014 USD ($) installment	Jan. 31, 2016 USD ($)
Debt Instrument [Line Items]
Aggregate borrowing capacity	$ 5,000,000.0
Loan and Security Agreement (LSA)
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity	$ 15,000,000.0
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	$ 5,000,000.0
Fixed interest rate	6.97%
Term B and Term C Loans
Debt Instrument [Line Items]
Aggregate borrowing capacity		$ 10,000,000.0

Fair Value Measurements and Available for Sale Investments - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	$ 160,743	$ 257,515
US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	107,697	96,434
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	2,436	5,428
Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	21,169	33,623
Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	29,441	122,030
Fair Value, Measurements, Recurring \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	107,697	96,434
Fair Value, Measurements, Recurring \| Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	2,436	5,428
Fair Value, Measurements, Recurring \| Agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	21,169	33,623
Fair Value, Measurements, Recurring \| Commercial and corporate obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	29,441	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	188,297	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	57,153	7,619
Fair Value, Measurements, Recurring \| Quoted Market Prices for Identical Assets (Level 1) \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	107,697	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]
Total Fair Value	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]
Total Fair Value	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]
Total Fair Value	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	188,297	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	57,153	7,619
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	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]
Total Fair Value	2,436	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]
Total Fair Value	21,169	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]
Total Fair Value	29,441	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) \| US Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Fair Value	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]
Total Fair Value	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]
Total Fair Value	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]
Total Fair Value	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 Available for Sale Investments - Fair Value of Other Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 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 Available for Sale Investments - Available-for-sale Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 160,540	$ 256,969
Gross Unrealized Gains	208	552
Gross Unrealized Losses	(5)	(6)
Total Fair Value	160,743	257,515
Short-term investments	143,197	203,210
Long-term investments	17,546	54,305
Agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	21,169	33,543
Gross Unrealized Gains	1	80
Gross Unrealized Losses	(1)	0
Total Fair Value	21,169	33,623
Short-term investments	10,000	16,500
Long-term investments	$ 11,200	$ 17,100
Agency securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	1 year	1 year
Agency securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	2 years	2 years
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,427	$ 5,381
Gross Unrealized Gains	9	47
Gross Unrealized Losses	0	0
Total Fair Value	2,436	5,428
Short-term investments	1,100	4,600
Long-term investments	$ 1,300	$ 800
Certificates of deposit \| Minimum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	1 year	1 year
Certificates of deposit \| Maximum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	2 years	2 years
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 29,414	$ 121,809
Gross Unrealized Gains	28	225
Gross Unrealized Losses	(1)	(4)
Total Fair Value	29,441	122,030
Short-term investments	29,400	111,100
Long-term investments	$ 0	$ 10,900
Commercial and corporate obligations \| Minimum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	1 year	1 year
Commercial and corporate obligations \| Maximum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	2 years	2 years
US Treasury Securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 107,530	$ 96,236
Gross Unrealized Gains	170	200
Gross Unrealized Losses	(3)	(2)
Total Fair Value	107,697	96,434
Short-term investments	102,700	70,900
Long-term investments	$ 5,000	$ 25,500
US Treasury Securities \| Minimum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	1 year	1 year
US Treasury Securities \| Maximum
Debt Securities, Available-for-sale [Line Items]
Remaining maturity	2 years	2 years

Fair Value Measurements and Available for Sale Investments - Schedule of Unrealized Loss and Fair Values in a Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	$ 46,713	$ 23,594
Less than 12 Months, Gross Unrealized Losses	(5)	(6)
12 Months or Greater, Fair Value	2,399	0
12 Months or Greater, Gross Unrealized Losses	0	0
Fair Value	49,112	23,594
Gross Unrealized Losses	(5)	(6)
Agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	4,999
Less than 12 Months, Gross Unrealized Losses	(1)
12 Months or Greater, Fair Value	0
12 Months or Greater, Gross Unrealized Losses	0
Fair Value	4,999
Gross Unrealized Losses	(1)
Commercial and corporate obligations
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	6,503	5,986
Less than 12 Months, Gross Unrealized Losses	(1)	(4)
12 Months or Greater, Fair Value	2,399	0
12 Months or Greater, Gross Unrealized Losses	0	0
Fair Value	8,902	5,986
Gross Unrealized Losses	(1)	(4)
US Treasury Securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	35,211	17,608
Less than 12 Months, Gross Unrealized Losses	(3)	(2)
12 Months or Greater, Fair Value	0	0
12 Months or Greater, Gross Unrealized Losses	0	0
Fair Value	35,211	17,608
Gross Unrealized Losses	$ (3)	$ (2)

Fair Value Measurements and Available for Sale Investments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Unrealized losses on available-for-sale	$ 0	$ 0
Allowance for credit losses	$ 0	$ 0

Stockholders' Equity - Additional Information (Details) - shares	Dec. 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)	27,355,575	27,255,000
Common stock, shares outstanding (in shares)	27,355,575	27,255,000

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Issued and Outstanding:
Stock options (in shares)	2,920,700	3,039,880
Common stock, shares reserved for issuance (in shares)	6,904,483
2017 Equity Incentive Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	2,986,101
2017 Employee Stock Purchase Plan
Issued and Outstanding:
Shares reserved for future award grants (in shares)	997,682

Equity Incentive Plans - Narrative (Details) - USD ($) $ in Thousands				12 Months Ended
	Jan. 01, 2020	Jan. 01, 2018	Jan. 26, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of common stock, upon the exercise of stock options				$ 496	$ 3,007	$ 2,869
Unrecognized compensation cost				$ 22,900
Employee and Nonemployee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Award expiration period				10 years
Weighted average period remaining for amortization of unrecognized compensation cost				2 years 11 months 1 day
Options \| Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				1 year
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 Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares
Shares Subject to Options
Stock options outstanding, beginning balance (in shares) \| shares	3,039,880
Granted (in shares) \| shares	539,825
Exercises (in shares) \| shares	(100,493)
Forfeitures and cancellations (in shares) \| shares	(558,512)
Stock options outstanding, ending balance (in shares) \| shares	2,920,700
Stock options exercisable, ending balance (in shares) \| shares	1,606,744
Weighted-Average Exercise Price per Share
Stock options outstanding, beginning balance (in dollars per share) \| $ / shares	$ 29.40
Granted (in dollars per share) \| $ / shares	19.13
Exercises (in dollars per share) \| $ / shares	4.94
Forfeitures and cancellations (in dollars per share) \| $ / shares	38.13
Stock options outstanding, ending balance (in dollars per share) \| $ / shares	26.67
Stock options exercisable, ending balance (in dollars per share) \| $ / shares	$ 26.56
Weighted-Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted average remaining contractual term, options outstanding	7 years 3 months 14 days
Weighted average remaining contractual term, options exercisable	5 years 11 months 4 days
Aggregate intrinsic value, options outstanding \| $	$ 17,434
Aggregate intrinsic value, options exercisable \| $	$ 12,326

Equity Incentive Plans - Option Fair Value Assumptions (Details) - Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.50%	2.00%	2.70%
Expected volatility	90.20%	77.98%	67.70%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	6 years 3 months	6 years 3 months	6 years 3 months
Weighted average grant date fair value per share (in dollars per share)	$ 14.51	$ 21.99	$ 61.41

Equity Incentive Plans - Allocation of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 11,499	$ 12,411	$ 9,961
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	4,122	5,564	3,371
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 7,377	$ 6,847	$ 6,590

Australia Research and Development Tax Incentive (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Tax Credit Carryforward [Line Items]
Research and development tax incentive credit received during the period	$ 0.0	$ 200,000
Australian tax incentive receivable	$ 0
Australian Taxation Office \| Subsidiaries
Tax Credit Carryforward [Line Items]
Refundable tax incentive for qualified research and development activities	43.50%	43.50%	43.50%
Research and development		$ 0.0	$ 100,000

Employee Benefit Plan (Details) - USD ($)	12 Months Ended
Employee Benefit Plan (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Employer match, percent of contributions	50.00%
Employer match, percent of employees' gross pay	6.00%
Employer match, maximum contributions	$ 6,000
Employer contributions to the plan	$ 500,000	$ 300,000	$ 0

Commitments and Contingencies - Narrative (Details) ft² in Thousands			12 Months Ended
	Dec. 15, 2020 USD ($)	May 04, 2020 ft² $ / ft²	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Finite-Lived Intangible Assets [Line Items]
Loss on disposal of tenant improvements and certain equipment	$ 100,000		$ 100,000
Operating lease, weighted average discount rate, percent			8.59%
Operating leases, rent expense					$ 700,000
Prepaid rent			$ 200,000
Security deposit			$ 300,000
Licensing agreement, remaining life			19 years
License costs			$ 200,000	$ 500,000	300,000
Cash payments under licensing agreements			300,000	100,000	$ 200,000
Future minimum annual cash obligations, next 12 months			200,000
Future minimum annual cash obligations, thereafter			$ 200,000
License agreement, obligation payable period			10 years
Standby Letters of Credit
Finite-Lived Intangible Assets [Line Items]
Letters of credit outstanding			$ 60,000	$ 60,000
Lease Agreement
Finite-Lived Intangible Assets [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%

Commitments and Contingencies - Schedule of ROU Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating ROU assets	$ 344	$ 1,402	$ 2,100
Operating lease liabilities	342	871
Operating lease liabilities	$ 0	$ 654
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent

Commitments and Contingencies - Costs in Cash Flow Statement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 865	$ 879
Cash paid for amounts included in the measurement of lease liabilities	$ 938	$ 937

Commitments and Contingencies - Schedule of Future Minimum Annual Obligations under Operating Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2019
Finite-Lived Intangible Assets [Line Items]
2021	$ 352
2022	0
2023	0
2024	0
2025	0
Thereafter	0
Total minimum payments required	352
Less: Imputed interest	(10)
Present value of lease liabilities	342	$ 2,300
Lease Agreement
Finite-Lived Intangible Assets [Line Items]
2021	568
2022	2,328
2023	2,397
2024	2,469
2025	2,543
Thereafter	15,420
Total minimum payments required	$ 25,725

Income Taxes - Components of income/(loss) before income tax provision (benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
U.S.	$ (19,832)	$ (97,187)	$ (61,193)
Foreign	(99)	(301)	(655)
Loss before income taxes	$ (19,931)	$ (97,488)	$ (61,848)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=68072869&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(15))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Income Taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Tax Assets:
Net operating loss carryforwards	$ 57,772	$ 55,722
Research and development credits	17,614	14,244
Equity compensation	5,329	4,067
Other, net	769	799
Total deferred tax assets	81,484	74,832
Deferred Tax Liabilities:
Fixed assets	(150)	(349)
Total deferred tax liabilities	(150)	(349)
Net deferred tax assets	81,334	74,483
Less: valuation allowance	(81,334)	(74,483)
Deferred tax assets, net of valuation allowance	$ 0	$ 0

Income Taxes - Additional information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits that if recognized and realized would affect the effective tax rate	$ 0	$ 0
Interest or penalties on uncertain tax benefits	0	$ 0
Federal tax authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	248,400,000
Net operating loss carryforward, utilization limitation				$ 5,300,000
Federal tax authority \| 2018 and after
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards			$ 188,400,000
Federal tax authority \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research tax credit carryforwards	14,300,000
Tax credit carryforward, utilization limitation				200,000
State tax authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	64,200,000
Net operating loss carryforward, utilization limitation				5,400,000
State tax authority \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research tax credit carryforwards	8,900,000
Tax credit carryforward, utilization limitation				$ 200,000
Foreign tax authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 3,400,000

Income Taxes - Reconciliation of income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected income tax benefit at federal statutory tax rate	$ (4,186)	$ (20,473)	$ (12,988)
State income taxes, net of federal benefit	(21)	(377)	(166)
Permanent items	18	34	17
Equity compensation	871	(1,122)	(6,693)
Research and development expenditure	0	0	63
Refundable AMT credit	0	0	(139)
Return to provision adjustment	(11)	(661)	60
Rate differential	40	(53)	155
Research credits	(3,389)	(4,405)	(4,393)
Change in the valuation allowance	6,678	26,905	23,892
Income tax benefit	0	(152)	(192)
Excess tax benefits associated with the exercise of non-qualified stock options	0	1,100	4,900
Disqualifying dispositions of incentive stock options	$ 200	$ 300	$ 2,200

Income Taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning of the year	$ 3,146	$ 1,812
Increase related to prior year tax positions	0	168
Increase related to current year tax positions	898	1,166
Balance at the end of the year	$ 4,044	$ 3,146

Subsequent Event (Details) $ in Millions	3 Months Ended
Subsequent Event (Details) $ in Millions	Mar. 31, 2021 USD ($)
Forecast \| TESARO \| Anti-PD-1 (GSK4057190A/Dostarlimab) \| Completion of first in vivo toxicology studies using GLPs
Subsequent Event [Line Items]
Milestone payment earned	$ 10.0