Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2018	Mar. 07, 2019	Jun. 30, 2018
Document And Entity Information
Entity Registrant Name	Corvus Pharmaceuticals, Inc.
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Central Index Key	0001626971
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Public Float			$ 156.7
Entity Common Stock, Shares Outstanding		29,326,900
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 39,196	$ 45,106
Marketable securities	75,401	44,949
Prepaid and other current assets	992	1,179
Total current assets	115,589	91,234
Property and equipment, net	2,180	2,672
Other assets	463	869
Total assets	118,232	94,775
Current liabilities:
Accounts payable	1,998	3,454
Accrued and other liabilities	5,029	5,515
Total current liabilities	7,027	8,969
Other liabilities	869	971
Total liabilities	7,896	9,940
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock: $0.0001 par value; 10,000,000 shares authorized at December 31, 2018 and December 31, 2017; 0 shares issued and outstanding at December 31, 2018 and December 31, 2017
Common stock: $0.0001 par value; 290,000,000 shares authorized at December 31, 2018 and December 31, 2017; 29,323,930 and 21,041,250 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	3	2
Additional paid-in capital	280,840	208,408
Accumulated other comprehensive loss	(34)	(41)
Accumulated deficit	(170,473)	(123,534)
Total stockholders' equity	110,336	84,835
Total liabilities and stockholders' equity	$ 118,232	$ 94,775

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	290,000,000	290,000,000
Common stock, shares issued	29,323,930	21,041,250
Common stock, shares outstanding	29,323,930	21,041,250

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research and development	$ 38,586	$ 46,305	$ 29,356
General and administrative	10,636	10,219	7,620
Total operating expenses	49,222	56,524	36,976
Loss from operations	(49,222)	(56,524)	(36,976)
Interest income and other expense, net	2,283	861	601
Net loss	$ (46,939)	$ (55,663)	$ (36,375)
Net loss per share, basic and diluted (in dollars per share)	$ (1.71)	$ (2.72)	$ (2.36)
Shares used to compute net loss per share, basic and diluted (in shares)	27,509,960	20,488,506	15,422,041
Shares used to compute pro forma net loss per share, diluted (in shares)	27,509,960	20,488,506	15,422,041
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	$ 7	$ (2)	$ 6
Comprehensive loss	$ (46,932)	$ (55,665)	$ (36,369)

CONSOLIDATED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	IPO Common Stock.	IPO Additional Paid-In Capital	IPO	At-the-market offering Common Stock.	At-the-market offering Additional Paid-In Capital	At-the-market offering	Follow On Public Offering Common Stock.	Follow On Public Offering Additional Paid-In Capital	Follow On Public Offering	Series A and Series B convertible preferred stock	Common Stock.	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Balance at Dec. 31, 2015										$ 125,780
Increase (Decrease) in Convertible Preferred Stock
Conversion of convertible preferred stock into common stock										$ (125,780)	$ 1	$ 125,779			$ 125,780
Common stock issued with conversion of preferred stock (in shares)										(14,274,741)	14,274,741
Balance at Dec. 31, 2015												440	$ (45)	$ (31,496)	(31,101)
Balance (in shares) at Dec. 31, 2015										14,274,741	1,431,615
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock	$ 1	$ 70,624	$ 70,625
Issuance of stock (in shares)	5,202,618
Common stock issued on exercise of stock options												4			4
Common stock issued on exercise of stock options (in shares)											13,454
Vesting of restricted stocks issued upon early exercise of stock options												34			34
Stock-based compensation expense												3,828			3,828
Unrealized loss on marketable securities													6		6
Net loss														(36,375)	(36,375)
Balance at Dec. 31, 2016											$ 2	200,709	(39)	(67,871)	132,801
Balance (in shares) at Dec. 31, 2016											20,922,428
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock					$ 711	$ 711
Issuance of stock (in shares)				52,569
Common stock issued on exercise of stock options												731			731
Common stock issued on exercise of stock options (in shares)											66,253
Vesting of restricted stocks issued upon early exercise of stock options												28			28
Stock-based compensation expense												6,229			6,229
Unrealized loss on marketable securities													(2)		(2)
Net loss														(55,663)	(55,663)
Balance at Dec. 31, 2017											$ 2	208,408	(41)	(123,534)	84,835
Balance (in shares) at Dec. 31, 2017											21,041,250
Increase (Decrease) in Stockholders' Deficit
Issuance of common stock							$ 1	$ 64,876	$ 64,877
Issuance of stock (in shares)							8,117,647
Common stock issued on exercise of stock options												393			393
Common stock issued on exercise of stock options (in shares)											165,033
Vesting of restricted stocks issued upon early exercise of stock options												28			28
Stock-based compensation expense												7,135			7,135
Unrealized loss on marketable securities													7		7
Net loss														(46,939)	(46,939)
Balance at Dec. 31, 2018											$ 3	$ 280,840	$ (34)	$ (170,473)	$ 110,336
Balance (in shares) at Dec. 31, 2018											29,323,930

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (46,939)	$ (55,663)	$ (36,375)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	847	842	594
Accretion related to marketable securities	(608)	(195)	648
Stock-based compensation	7,135	6,229	3,828
Changes in operating assets and liabilities:
Prepaid and other current assets	187	(44)	290
Other assets	406		(869)
Accounts payable	(1,456)	1,554	518
Accrued and other liabilities	(458)	1,499	2,814
Other long-term liabilities	(102)	(434)	695
Net cash used in operating activities	(40,988)	(46,212)	(27,857)
Cash flows from investing activities
Purchases of marketable securities	(161,861)	(88,309)	(258,281)
Sales of marketable securities			4,199
Maturities of marketable securities	132,024	173,401	213,725
Purchase of property and equipment	(355)	(266)	(2,199)
Net cash provided by (used in) investing activities	(30,192)	84,826	(42,556)
Cash flows from financing activities
Proceeds from issuance of common stock, net (includes $30,850 and $34,000 in aggregate gross proceeds from related parties for the years ended December 31, 2018 and 2016, respectively)	64,877	711	71,354
Proceeds from exercise of common stock options	393	731	4
Net cash provided by financing activities	65,270	1,442	71,358
Net increase (decrease) in cash and cash equivalents	(5,910)	40,056	945
Cash and cash equivalents at beginning of the period	45,106	5,050	4,105
Cash and cash equivalents at end of the period	39,196	$ 45,106	5,050
Supplemental disclosures of cash flow information
Purchases of property and equipment incurred but not paid	$ 84		$ 84

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The Company’s functional and reporting currency is the U.S. dollar. The accompanying consolidated financial statements have been prepared on a going-concern basis, which contemplates the realization of assets and discharge of liabilities in the normal course of business. Since its inception, the Company has incurred significant losses and negative cash flows from operations. As of December 31, 2018, the Company had an accumulated deficit of $170.5 million and cash, cash equivalents and marketable securities of $114.6 million. The Company has financed its operations primarily with the proceeds from the sale of stock. The Company will need to raise additional capital to meet its business objectives. The Company believes that its current cash, cash equivalents and marketable securities will be sufficient to fund its planned expenditures and meet its obligations through at least the next twelve months from the issuance of these financial statements.

Use of Estimates

The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from such estimates.

Initial Public Offering

On March 22, 2016, the Company’s registration statement on Form S-1 (File No. 333-208850) relating to its initial public offering (“IPO”) of its common stock was declared effective by the Securities and Exchange Commission (“SEC”) and the shares of its common stock began trading on the Nasdaq Global Market on March 23, 2016. The public offering price of the shares sold in the IPO was $15.00 per share. The IPO closed on March 29, 2016, pursuant to which the Company sold 4,700,000 shares of its common stock. On April 26, 2016, the Company sold an additional 502,618 shares of its common stock to the underwriters upon partial exercise of their over-allotment option, at the initial offering price of $15.00 per share. The Company received aggregate net proceeds of approximately $70.6 million, after underwriting discounts, commissions and offering expenses. Immediately prior to the consummation of the IPO, all outstanding shares of convertible preferred stock were converted into common stock.

Follow-on Public Offering

In March 2018, the Company completed a follow-on public offering in which the Company sold 8,117,647 shares of common stock at a price of $8.50 per share, which included 1,058,823 shares issued pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock. The aggregate net proceeds received by the Company from the offering were approximately $64.9 million, net of underwriting discounts and commissions and offering expenses payable by the Company.

Concentrations of Credit Risk and Other Risks and Uncertainties

Substantially all of the Company’s cash and cash equivalents are deposited in accounts with two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The Company maintains its cash with an accredited financial institution and accordingly, such funds are subject to minimal credit risk. The Company’s marketable securities consist of investments in U.S. government agency securities and corporate debt obligations, which can be subject to certain credit risks. However, the Company mitigates the risks by investing in high-grade instruments, limiting its exposure to any one issuer, and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any losses on its deposits of cash, cash equivalents or marketable securities.

The Company is subject to a number of risks similar to other early stage biopharmaceutical companies, including, but not limited to, the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, its reliance on third parties to conduct its clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s product candidates, its right to develop and commercialize its product candidates pursuant to the terms and conditions of the licenses granted to the Company, and protection of proprietary technology. If the Company does not successfully commercialize or partner any of its product candidates, it will be unable to generate product revenue or achieve profitability.

Segments

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision‑maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment, that of the development of and commercialization of precisely targeted oncology therapies.

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investment securities with remaining maturities at the date of purchase of three months or less to be cash equivalents.

Investments with remaining maturities, at the date of purchase, greater than three months are classified as “available-for-sale” and are carried at fair value with unrealized gains and losses, if any, included as a component of accumulated other comprehensive income (loss) in stockholders’ equity (deficit). Interest and realized gains and losses are included in interest income. Realized gains and losses are recognized based on the specific identification model.

Fair Value Measurements

Fair value accounting is applied for all financial assets and liabilities and non-financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, accounts payable and accrued liabilities, approximate fair value due to their short-term maturities.

Property and Equipment, Net

Property and equipment are stated at cost and depreciated using the straight‑line method over the estimated useful lives of the respective assets:


Laboratory equipment	5	years
Computer equipment and purchased software	3	years
Leasehold improvements	Shorter of asset's useful life or remaining term of lease

Maintenance and repairs that do not extend the life or improve the asset are expensed when incurred. When assets are retired or otherwise disposed of, the cost and accumulated depreciation or amortization are removed from the balance sheet and any resulting gain or loss is reflected in operations.

Impairment of Long‑Lived Assets

The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate positive income from operations and positive cash flow in future periods as well as the strategic significance of the assets to the Company’s business objectives. Should impairment exist, the impairment loss to be recognized is measured by the amount by which the carrying amount of the asset exceeds the projected discounted future net cash flows arising from the asset. All long-lived assets are maintained in the United States of America.

Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.

Research and Development Expenses

The Company records research and development expenses as incurred. The Company accounts for nonrefundable advance payments for goods and services that will be used in future research and development activities as expenses when the goods have been received or when the service has been performed rather than when the payment is made. Research and development expenses consist of costs incurred by the Company for the discovery and development of the Company’s product candidates and include:

employee‑related expenses, including salaries, benefits, travel and non‑cash stock‑based compensation expense;

external research and development expenses incurred under arrangements with third parties, such as contract research organizations, contract manufacturing organizations, academic and non‑profit institutions and consultants;

costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use;

license fees; and

other expenses, which include direct and allocated expenses for laboratory, facilities and other costs.

Clinical Trial Accruals

Costs for preclinical studies and clinical trial activities are recognized based on an evaluation of the vendors’ progress towards completion of specific tasks, using data such as clinical site activations, patient enrollment or information provided to the Company by its vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. The Company determines accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion, or the services completed. The Company’s estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time.

Stock‑Based Compensation

The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non‑employee service providers.

The Company accounts for stock-based employee compensation arrangements in accordance with the provisions of ASC 718, “Compensation—Stock Compensation.” For stock options granted to employees, the Company recognizes compensation expense for all stock-based awards based on the grant-date estimated fair values. The value of the award is recognized as an expense ratably over the requisite service period. The fair value of stock options is determined using the Black-Scholes option pricing model. Forfeitures are accounted for when they occur.

Stock-based compensation expense related to stock options granted to non-employees is recognized based on the fair value of the stock options, determined using the Black-Scholes option pricing model. The expense for options granted to non-employees is periodically re-measured as the underlying options vest. The awards generally vest over the time period the Company expects to receive service from the non-employee.

Income Taxes

The Company accounts for income taxes under the asset and liability method. The Company estimates actual current tax exposure together with assessing temporary differences resulting from differences in accounting for reporting purposes and tax purposes for certain items, such as accruals and allowances not currently deductible for tax purposes. These temporary differences result in deferred tax assets and liabilities, which are included in the Company’s balance sheets. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the Company’s statements of operations and comprehensive loss become deductible expenses, under applicable income tax laws or when net operating loss or credit carryforwards are utilized. Accordingly, realization of the Company’s deferred tax assets is dependent on future taxable income against which these deductions, losses and credits can be utilized.

The Company must assess the likelihood that the Company’s deferred tax assets will be recovered from future taxable income and a valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. Based on the available evidence, the Company is unable, at this time, to support the determination that it is more likely than not that its deferred tax assets will be utilized in the future. Accordingly, the Company recorded a full valuation allowance for all periods presented. The Company intends to maintain a valuation allowance until sufficient evidence exists to support its reversal.

The Company recognizes benefits of uncertain tax positions if it is more likely than not such positions will be sustained upon examination based solely on their technical merits as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. The Company is required to file income tax returns in the U.S. federal jurisdiction. The Company currently is not under examination by the Internal Revenue Service or other jurisdictions for any tax years.

On December 22, 2017, the 2017 Tax Cuts and Jobs Act (the “Tax Act”) was enacted into law and the new legislation contains several key tax provisions that affected the Comapny, including a one-time mandatory transition tax on accumulated foreign earnings and a reduction of the corporate income tax rate to 21% effective January 1, 2018. The Company is required to recognize the effect of the tax law changes in the period of enactment, such as determining the transition tax, remeasuring the Company’s U.S. deferred tax assets and liabilities as well as reassessing the net realizability of deferred tax assets and liabilities. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), which allowed the Company to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. In accordance with this guidance, the Company recorded a decrease related to the net deferred tax asset balance of $4.9 million with a corresponding net adjustment to the Company’s valuation allowance. During the year ending December 31, 2018, the Company did not record any measurement period adjustments to this amount as the Company’s accounting for the Tax Act related to deferred remeasurement was complete during the period ending December 31, 2017. The Company’s overall accounting for the impact of the 2017 Tax Act is complete as of the period ending December 31, 2018. Refer to Note 10 in these notes to the consolidated financial statements for additional information.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive loss in any period presented was unrealized gains and losses on available-for-sale marketable securities.

Net Loss per Share

Basic net loss per share is calculated by dividing the net loss by the weighted average number of common shares outstanding during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, common stock subject to repurchase and stock options are considered to be potentially dilutive securities. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers, which required an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU No. 2014-09 will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The new standard is effective January 1, 2018 for public companies. Early application is permitted as of January 1, 2017. The standard permits the use of either the retrospective or cumulative effect transition method. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net), which clarifies the implementation guidance on principal versus agent considerations in ASU No. 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, which clarifies certain aspects of identifying performance obligations and licensing implementation guidance. In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients, which relates to disclosures of remaining performance obligations, as well as other amendments to guidance on collectability, non-cash consideration and the presentation of sales and other similar taxes collected from customers. These standards have the same effective date and transition date of January 1, 2018. The Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have a material impact on its condensed consolidated financial statements as the Company is not yet generating revenues.

In February 2016, the FASB, issued “ASU 2016-02, Leases.” The standard requires entities to recognizew in the consolidated balance sheet a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. We will adopt the standard on January 1, 2019 using the modified retrospective method in the year of adoption, and electing certain transition practical expedients. We are in the process of evaluating the impact of this standard and expect it to primarily relate to our operating leases for office and laboratory space noted in “Part I. Item 2. Properties” of this Annual Report on Form 10-K, for which we will record a lease liability and corresponding right-of-use asset upon adoption. We do not expect the adoption of this standard to impact accumulated deficit on January 1, 2019.

In May 2017, the FASB issued ASU No 2017-09, Compensation—Stock Compensation (Topic 718) — Scope of Modification Accounting, to clarify when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new standard, modification is required only if the fair value, the vesting conditions, or the classification of an award as equity or liability changes as a result of the change in terms or conditions. ASU 2017-09 was effective for the Company beginning January 1, 2018 and is applied prospectively. Early adoption is permitted. The Company adopted this guidance on January 1, 2018. The adoption of this guidance did not have a material impact on its consolidated financial statements as the Company has not made any changes to the terms or conditions of its share-based payment awards.

Net Loss per Share

12 Months Ended

Dec. 31, 2018

Net Loss per Share

Net Loss per Share

3. Net Loss per Share

The following table shows the calculation of net loss per share (in thousands, except share and per share data):


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net loss - basic and diluted	$	(46,939)	$	(55,663)	$	(36,375)
Denominator:
Weighted average common shares outstanding		27,686,909		20,958,557		16,188,980
Less: weighted average common shares subject to repurchase		(176,949)		(470,051)		(766,939)
Weighted average common shares outstanding used to compute basic and diluted net loss per share		27,509,960		20,488,506		15,422,041
Net loss per share, basic and diluted	$	(1.71)	$	(2.72)	$	(2.36)

The amounts in the table below were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect:



	Year Ended December 31,
	2018	2017	2016
Common stock subject to repurchase	43,076	319,203	611,698
Outstanding options	3,778,259	3,013,394	2,350,582
Total shares of common stock equivalents	3,821,335	3,332,597	2,962,280

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Measurements

Fair Value Measurements

4. Fair Value Measurements

Financial assets and liabilities are measured and recorded at fair value. The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs:

Level 1—Quoted prices in active markets for identical assets or liabilities

Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly

Level 3—Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability

There have been no transfers of assets and liabilities between levels of hierarchy.

The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs.

The following tables present information as of December 31, 2018 and 2017 about the Company’s assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy the Company utilized to determine such fair values (in thousands):


	December 31, 2018
	Fair Value Measured Using						Total
	(Level 1)		(Level 2)		(Level 3)		Balance
Assets
Cash equivalents	$	38,698	$	—	$	—	$	38,698
Marketable securities		—		75,401		—		75,401
	$	38,698	$	75,401	$	—	$	114,099


	December 31, 2017
	Fair Value Measured Using						Total
	(Level 1)		(Level 2)		(Level 3)		Balance
Assets
Cash equivalents	$	44,555	$	—	$	—	$	44,555
Marketable securities		—		44,949		—		44,949
	$	44,555	$	44,949	$	—	$	89,504

As of December 31, 2018, marketable securities had a maximum remaining maturity of ten months.

As of December 31, 2018 and 2017, the fair value of available for sale marketable securities by type of security were as follows (in thousands):


	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
U.S. Government agency securities	$	49,124	$	—	$	(27)	$	49,097
Corporate debt obligations		26,311		—		(7)		26,304
	$	75,435	$	—	$	(34)	$	75,401


	December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
U.S. Government agency securities	$	32,311	$	—	$	(39)	$	32,272
Corporate debt obligations		12,679		—		(2)		12,677
	$	44,990	$	—	$	(41)	$	44,949

- 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

License and Collaboration Agreements	12 Months Ended
License and Collaboration Agreements	Dec. 31, 2018
License And Collaboration Agreements [Abstract]
License and Collaboration Agreements	5. License and Collaboration Agreements Scripps Licensing Agreement In December 2014, the Company entered into a license agreement with The Scripps Research Institute (“Scripps”), pursuant to which it was granted a non-exclusive, world-wide license for all fields of use under Scripps’ rights in certain know-how and technology related to a mouse hybridoma clone expressing an anti-human CD73 antibody, and to progeny, mutants or unmodified derivatives of such hybridoma and any antibodies expressed by such hybridoma, from which we developed CPI-006. Scripps also granted the Company the right to grant sublicenses in conjunction with other proprietary rights the Company holds, or to others collaborating with or performing services for the Company. Under this license agreement, Scripps has agreed not to grant any additional commercial licenses with respect to such materials, other than march-in rights granted to the U.S. government. Upon execution of the agreement, the Company made a one‑time cash payment to Scripps of $10,000 in 2015 and is also obligated to pay a minimum annual fee to Scripps of $25,000. The one‑time cash payment was recorded as research and development expense as technological feasibility of the asset had not been established and there was no alternative future use. The first minimum annual fee payment is due on the first anniversary of effective date of the agreement and will be due on each subsequent anniversary of the effective date for the term of the agreement. The Company is also required to make performance‑based cash payments upon successful completion of clinical and sales milestones. The aggregate potential milestone payments are $2.6 million. The Company is also required to pay royalties on net sales of licensed products (including CPI-006) sold by it, its affiliates and its sublicensees at a rate in the low‑single digits. In addition, should the Company sublicense the rights licensed under the agreement, it has agreed to pay a percentage of sublicense revenue received at specified rates that start at double digit percentages and decrease to single digit percentages based on the elapsed time from the effective date of the agreement and the time of entry into such sublicense. To date, no milestone payments have been made. The Company’s license agreement with Scripps will terminate upon expiration of its obligation to pay royalties to Scripps under the license agreement. The Company’s license agreement with Scripps is terminable by the consent of the parties, at will by the Company upon providing 90 days written notice to Scripps, or by Scripps for certain material breaches, or if the Company undergoes a bankruptcy event. In addition, Scripps may terminate the license on a product‑by‑product basis, or the entire agreement, if the Company fails to meet specified diligence obligations related to the development and commercialization of licensed products. Scripps may also terminate the agreement after the third anniversary of the effective date of the agreement if it reasonably believes, based on reports the Company provides to Scripps, that the Company has not used commercially reasonable efforts as required under the agreement, subject to a specified notice and cure period. Vernalis Licensing Agreement In February 2015, the Company entered into a license agreement with Vernalis (R&D) Limited (“Vernalis”), which was subsequently amended as of November 5, 2015, and, pursuant to which the Company was granted an exclusive, worldwide license under certain patent rights and know-how, including a limited right to grant sublicenses, for all fields of use to develop, manufacture and commercialize products containing certain adenosine receptor antagonists, including CPI-444. Pursuant to this agreement, the Company made a one-time cash payment to Vernalis in the amount of $1.0 million, which was recorded as research and development expense as technological feasibility of the asset had not been established and there was no alternative future use. The Company is also required to make cash milestone payments to Vernalis upon the successful completion of clinical and regulatory milestones for licensed products depending on the indications for which such licensed products are developed and upon achievement of certain sales milestones. In February 2017, the Company made a milestone payment of $3.0 million to Vernalis following the expansion of a cohort of patients with renal cell cancer treated with single agent CPI-444 in the Company’s Phase 1/1b clinical trial. The aggregate potential milestone payments are approximately $220 million for all indications. The Company has also agreed to pay Vernalis tiered incremental royalties based on the annual net sales of licensed products containing CPI-444 on a product-by-product and country-by-country basis, subject to certain offsets and reductions. The tiered royalty rates for products containing CPI-444 range from the mid-single digits up to the low-double digits on a country-by-country net sales basis. The royalties on other licensed products that do not include CPI-444 also increase with the amount of net sales on a product-by-product and country-by-country basis and range from the low-single digits up to the mid-single digits on a country-by-country net sales basis. The Company is also obligated to pay to Vernalis certain sales milestones as indicated above when worldwide net sales reach specified levels over an agreed upon time period. The agreement will expire on a product‑by‑product and country‑by‑country basis upon the expiration of the Company’s payment obligations to Vernalis in respect of a particular product and country. Both parties have the right to terminate the agreement for an uncured material breach by the other party. The Company may also terminate the agreement at its convenience by providing 90 days written notice, provided that the Company has not received notice of its own default under the agreement at the time the Company exercises such termination right. Vernalis may also terminate the agreement if the Company challenges a licensed patent or undergoes a bankruptcy event. Genentech Collaboration Agreement In October 2015, the Company entered into a clinical trial collaboration agreement with Genentech to evaluate the safety, tolerability and preliminary efficacy of CPI-444 combined with Genentech’s investigational cancer immunotherapy, Tecentriq, a fully humanized monoclonal antibody targeting protein programmed cell death ligand 1(“PD-L1”), in a variety of solid tumors in a Phase 1/1b clinical trial. Pursuant to this agreement, the Company will be responsible for the conduct and cost of the relevant studies, under the supervision of a joint development committee made up of representatives of the Company and representatives of Genentech. Genentech will supply Tecentriq. As part of the agreement, the Company granted Genentech certain rights of first negotiation to participate in future clinical trials that the Company may conduct evaluating the administration of CPI-444 in combination with an anti-PD-1 or anti-PD-L1 antibody. If the Company and Genentech do not reach agreement on the terms of any such participation by Genentech within a specified time period, the Company retains the right to collaborate with third parties in such activities. The Company also granted Genentech certain rights of first negotiation should it decide to license development and commercialization rights to CPI-444. Should the Company and Genentech not reach agreement on the terms of such a license within a specified time period, it retains the right to enter into a license with another third party. The Company and Genentech each have the right to terminate the agreement for material breach by the other party. In addition, the agreement may be terminated by either party due to safety considerations, if directed by a regulatory authority or if development of CPI-444 or Tecentriq is discontinued. Further, the agreement will expire after a set period of time following the provision by the Company of the final clinical study report to Genentech. In May 2017, the Company signed a second clinical trial collaboration agreement with Genentech. Under the new agreement, CPI-444 administered in combination with Tecentriq will be evaluated in a Phase 1b/2 randomized, controlled clinical study as second-line therapy in patients with non-small cell lung cancer who are resistant and/or refractory to prior therapy with an anti-PD-(L)1 antibody. It is anticipated that the study will enroll up to 65 patients in the treatment arm. Genentech will be responsible for the conduct of the study and the parties will share the cost of the Phase 1b/2 trial, which began enrolling patients in the fourth quarter of 2017. The Company is responsible for supplying CPI-444 and retains global development and commercialization rights to CPI-444. The Company and Genentech each have the right to terminate the agreement for material breach by the other party. In addition, the agreement may be terminated by either party due to safety considerations, if directed by a regulatory authority or if development of CPI-444 or Tecentriq is discontinued.

Balance Sheet Components

12 Months Ended

Dec. 31, 2018

Balance Sheet Components

Balance Sheet Components

6. Balance Sheet Components (in thousands):


	December 31,
	2018		2017
Prepaid and Other Current Assets
Interest receivable	$	337	$	132
Prepaid research and development manufacturing expenses		75		327
Prepaid facility expenses		149		144
Prepaid insurance		166		164
Other		265		412
	$	992	$	1,179
Property and Equipment
Laboratory equipment	$	2,371	$	2,034
Computer equipment and purchased software		142		130
Leasehold improvements		2,084		2,078
		4,597		4,242
Less: accumulated depreciation and amortization		(2,417)		(1,570)
	$	2,180	$	2,672
Accrued and Other Liabilities
Accrued clinical trial related	$	2,718	$	2,870
Accrued manufacturing expense		1,077		1,056
Personnel related		649		572
Deferred rent		160		410
Accrued legal and accounting		77		224
Other accrued expenses		348		383
	$	5,029	$	5,515
Other Liabilities
Deferred rent	$	869	$	960
Shares subject to vesting		—		11
	$	869	$	971

Common Stock

12 Months Ended

Dec. 31, 2018

Common Stock

Common Stock

7. Common Stock

As of December 31, 2018, the amended and restated certificate of incorporation authorizes the Company to issue 290 million shares of common stock and 10 million shares of preferred stock.

Each share of common stock is entitled to one vote. Common stockholders are entitled to dividends if and when declared by the board of directors. As of December 31, 2018, no dividends on common stock had been declared.

On September 20, 2017, the Company entered into a sales agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $125,000,000, through an at-the-market equity offering program under which Cowen will act as its sales agent. The issuance and sale of shares of common stock by the Company pursuant to the Sales Agreement are deemed an “at-the-market” offering under the Securities Act of 1933, as amended. Cowen is entitled to compensation for its services equal to up to 3.0% of the gross proceeds of any shares of common stock sold through Cowen under the Sales Agreement. During the year ended December 31, 2018 and 2017, the Company received no proceeds and approximately $0.7 million, respectively, from the sale of shares of common stock pursuant to the Sales Agreement.

The Company has reserved shares of common stock, for issuance as follows:


	December 31,
	2018	2017	2016
Shares available for future option grants	2,486,637	2,576,535	2,475,600
Outstanding options	3,778,259	3,013,394	2,350,582
Unvested restricted common stock (founders and early exercise of stock options)	43,076	319,203	611,698
Shares reserved for employee stock purchase plan	400,000	400,000	200,000
Total	6,707,972	6,309,132	5,637,880

Stock Option Plans

12 Months Ended

Dec. 31, 2018

Stock Option Plans

Stock Option Plans

8. Stock Option Plans

In February 2014, the Company adopted the 2014 Equity Incentive Plan (the “2014 Plan”), which was subsequently amended in November 2014, July 2015 and September 2015, under which it granted incentive stock options (“ISOs”) or non-qualified stock options (“NSOs”). Terms of stock agreements, including vesting requirements, are determined by the board of directors or a committee authorized by the board of directors, subject to the provisions of the 2014 Plan. In general, awards granted by the Company vest over four years and have maximum exercise term of 10 years. The 2014 Plan provides that grants must be at an exercise price of 100% of fair market value of the Company’s common stock as determined by the board of directors on the date of the grant.

In connection with the consummation of the IPO in March 2016, the 2016 Equity Incentive Award Plan (the “2016 Plan”), became effective. Under the 2016 Plan, incentive stock options, non-statutory stock options, stock purchase rights and other stock-based awards may be granted. Terms of stock agreements, including vesting requirements, are determined by the board of directors or a committee authorized by the board of directors, subject to the provisions of the 2016 Plan. In general, awards granted by the Company vest over four years and have maximum exercise term of 10 years. The 2016 Plan provides that grants must be at an exercise price of 100% of fair market value of the Company’s common stock as determined by the board of directors on the date of the grant. In conjunction with adopting the 2016 Plan, the 2014 Plan was terminated and no further awards will be granted under the 2014 Plan. Options outstanding under the 2014 Plan as of the effective date of the 2016 Plan that are forfeited or lapse unexercised may be re-issued under the 2016 Plan, up to a maximum of 1,136,229 shares.

Activity under the Company’s stock option plans is set forth below:


		Options Outstanding
			Weighted ‑
	Shares		Average
	Available	Number of	Exercise
	for Grant	Options	Price
Balance at December 31, 2017	2,576,535	3,013,394	$	11.78
Additional shares authorized	840,000	—		—
Options granted	(1,449,250)	1,449,250		7.30
Options exercised	—	(165,033)		2.38
Options forfeited	519,352	(519,352)		12.85
Balance at December 31, 2018	2,486,637	3,778,259	$	10.32

The following table summarizes information about stock options outstanding at December 31, 2018 and 2017:


			Options Outstanding				Options Vested
			at December 31, 2018				at December 31, 2018
				Weighted				Weighted
				Average				Average	Weighted
				Remaining	Weighted			Remaining	Average
				Contractual	Average			Contractual	Exercise
Exercise Price			Number	Life (in Years)	Exercise Price		Number	Life (in Years)	Price
$0.28	-	$4.65	301,803	6.44	$	0.72	261,373	6.42	$	0.68
$5.94	-	$9.52	1,101,750	9.92	$	6.10	3,585	8.69	$	8.92
$9.60	-	$14.43	1,026,180	8.97	$	10.89	269,731	8.70	$	10.56
$15.00	-	$16.70	1,348,526	7.50	$	15.49	834,456	7.38	$	15.37
			3,778,259	8.52	$	10.32	1,369,145	7.46	$	11.60


			Options Outstanding				Options Vested
			at December 31, 2017				at December 31, 2017
				Weighted				Weighted
				Average				Average	Weighted
				Remaining	Weighted			Remaining	Average
				Contractual	Average			Contractual	Exercise
Exercise Price			Number	Life (in Years)	Exercise Price		Number	Life (in Years)	Price
$0.28	-	$4.65	535,136	7.55	$	1.46	325,397	7.53	$	1.34
$6.75	-	$10.60	701,600	9.86	$	10.44	2,688	7.87	$	6.75
$11.21	-	$16.70	1,776,658	8.57	$	15.41	596,727	8.28	$	15.23
			3,013,394	8.69	$	11.78	924,812	8.02	$	11.40

The weighted average grant date fair value of options granted for the years ended December 31, 2018, 2017 and 2016, was $5.23, $8.93 and $10.78, respectively.

Options outstanding and exercisable that had vested or were expected to vest at December 31, 2018 were as follows:


				Weighted
				Average	Aggregate
		Weighted		Remaining	Intrinsic
	Number	Average		Contractual	Value
	of shares	Exercise Price		Life (years)	(in thousands)
Vested	1,369,145	$	11.60	7.46	$	804,162
Expected to vest	2,409,114	$	9.60	6.83	$	115,555

In the table above, aggregate intrinsic value represents the difference between the exercise price of the options to purchase common stock and the estimated fair value of the Company’s common stock of $3.67.

The aggregate intrinsic value of stock options exercised in the years ended December 31, 2018, 2017 and 2016, was $1.1 million, $0.3 million and $0.2 million, respectively.

The total fair value of options that vested in the year ended December 31, 2018, 2017 and 2016, was $7.1 million, $5.8 million, and $3.2 million, respectively.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2018

Stock-Based Compensation

Stock-Based Compensation

9. Stock‑Based Compensation

The Company’s results of operations include expenses relating to employee and non‑employee stock‑based awards as follows (in thousands):



	Year Ended December 31,
	2018		2017		2016
Research and development	$	2,919	$	2,692	$	1,685
General and administrative		4,216		3,537		2,143
Total	$	7,135	$	6,229	$	3,828

Valuation Assumptions

The Company estimated the fair value of employee stock options using the Black-Scholes valuation model. The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period of the awards. The fair value of employee stock options were estimated using the following assumptions for the years ended December 31, 2018, 2017 and 2016:


	Year Ended December 31,
	2018		2017		2016
Risk-free interest rate	2.8	%	2.1	%	1.6	%
Expected volatility	82.7	%	91.4	%	84.6	%
Expected term (in years)	6.0		6.0		6.0
Expected dividend yield	0	%	0	%	0	%

Risk-free Interest Rate: The Company based the risk-free interest rate over the expected term of the options based on the constant maturity rate of U.S. Treasury securities with similar maturities as of the date of the grant.

Volatility: The Company used an average historical stock price volatility of comparable public companies within the biotechnology and pharmaceutical industry that have been indentified as the Company’s industry peers.

Expected Term: The Company uses the simplified method prescribed in the ASC 718, Compensation—Stock Compensation, to calculate the expected term of options granted to employees and directors.

Expected Dividends: The Company has not paid and does not anticipate paying any dividends in the near future.

At December 31, 2018, 2017 and 2016, the unrecognized compensation expense associated with respect to options granted to employees was $15.8 million, $18.6 million and $18.5 million, respectively, and is expected to be recognized on a straight‑line basis over 2.72, 2.85, and 3.28 years, respectively.

Stock-based compensation expense related to awards to non-employees is recognized based on the then-current fair value at each measurement date over the associated service period of the award, which is generally the vesting term, on a straight line basis. The Company used the Black-Scholes valuation model to assist it in determining the fair value of stock-based awards. Stock-based compensation expense for non-employees was $52,000, $74,000 and $142,500 for the years ended December 31, 2018, 2017 and 2016, respectively.

The following assumptions were used in valuation of non-employee stock options:


	Year Ended December 31,
	2018					2017					2016
Risk-free interest rate	2.55	%	-	3.05	%	2.17	%	-	2.33	%	1.90	%	-	1.94	%
Expected volatility	83.2	%	-	95.2	%	80.3	%	-	83.0	%	92.1	%	-	92.7	%
Expected term (in years)	6.1		-	10.0		7.1		-	7.6		8.1		-	8.6
Expected dividend yield	0	%				0	%				0	%

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Taxes

Income Taxes

10. Income Taxes

The components of loss before income tax is as follows (in thousands):


	December 31,
	2018		2017		2016
Domestic	$	(47,096)	$	(28,253)	$	(11,375)
Foreign		157		(27,410)		(25,000)
	$	(46,939)	$	(55,663)	$	(36,375)

During the years ended December 31, 2018, 2017 and 2016, the Company recorded no income tax benefits for the net operating losses (NOLs) incurred due to the uncertainty of realizing a benefit from those items.

A reconciliation of the Company’s effective tax rate to the U.S. Federal statutory rate is as follows:


	December 31,
	2018		2017		2016
Federal tax benefit at statutory rate	21	%	34	%	34	%
State tax, net of Federal benefit	9	%	7	%	8	%
Foreign rate differential	—		(17)	%	(23)	%
Federal rate change impact	—		(9)	%	—
Change in valuation allowance	(41)	%	(16)	%	(19)	%
Research and development tax credits	2	%	2	%	2	%
Prior year federal true-up	10	%	(3)	%	—	%
Other	(1)	%	2	%	(2)
Effective income tax rate	0	%	0	%	0	%

The effective tax rate is different from the federal statutory tax rate primarily due to a valuation allowance against deferred tax assets as a result of the Company’s history of losses.

The principal components of the Company’s net deferred tax assets are as follows (in thousands)


	December 31,
	2018		2017		2016
Net operating loss carryforwards	$	31,533	$	15,438	$	9,339
Tax credit carryforwards		6,441		4,351		1,960
Capitalized tax assets		138		131		241
Accruals		188		183		230
Stock compensation		2,879		1,730		954
Other		58		52		67
Total deferred tax assets		41,237		21,885		12,791
Valuation allowance		(41,237)		(21,885)		(12,791)
Net deferred tax assets	$	—	$	—	$	—

The Company recorded a valuation allowance against its deferred tax assets at December 31, 2018 and 2017 because Company management believed that it was more likely than not that these assets would not be fully realized in the future. The valuation allowance increased by approximately $19.4 million and $9.1 million for the years ended December 31, 2018 and 2017, respectively. Changes in the valuation allowance for deferred tax assets relate primarily to the increase in the Company’s net operating loss carryforward.

As of December 31, 2018, the Company had federal NOL carryforwards of approximately $105.3 million and state NOL carryforwards of approximately $134.8 million which are available to reduce future taxable income. The NOLs will begin to expire in 2034, if not utilized.

As of December 31, 2018, the Company also had $4.4 million of federal and $3.7 million of state research and development tax credit carryforwards available to reduce future income taxes. The federal research and development tax credits will begin to expire 2035, if not utilized. The state research and development tax credits have no expiration date.

In general, if the Company experiences a greater than 50 percentage point aggregate change in ownership over a three-year period (a Section 382 ownership change), utilization of its pre-change NOL carryforwards are subject to an annual limitation under Section 382 of the Internal Revenue Code (California has similar laws). The annual limitation generally is determined by multiplying the value of the Company’s stock at the time of such ownership change (subject to certain adjustments) by the applicable long-term tax-exempt rate. Such limitations may result in expiration of a portion of the NOL carryforwards before utilization. The Company has not utilized any NOL carryovers through December 31, 2018. In addition, the Company’s deferred tax assets are subject to full valuation allowance, and thus no benefit for deferred tax assets have been recorded. The Company’s ability to use the remaining NOL carryforwards may be further limited if the Company experiences a Section 382 ownership change as a result of changes in stock ownership. The Company is currently performing an analysis to determine whether any of its NOL carryforwards are limited due to a change in ownership.

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code, including, but not limited to, (1) reducing the U.S. federal corporate tax rate from 35% to 21%; (2) requiring companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries; (3) generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; (4) requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations; (5) eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; (6) creating the base erosion anti-abuse tax (BEAT), a new minimum tax; (7) creating a new limitation on deductible interest expense; and (8) changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017.

The SEC staff issued SAB 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act. As of December 31, 2018, no provisional estimate has been recorded as the Company has completed its accounting under the Tax Act.

The Company’s accounting for the following elements of the Tax Act is complete:

Reduction of US federal Corporate Tax Rate: The Tax Act reduces the corporate tax rate to 21%, effective January 1, 2018. Accordingly, the Company has re-measured all deferred taxes at 21% as of December 31, 2017. Consequently, the Company has recorded a decrease related to the net deferred tax asset balance of $4.9 million, with a corresponding net adjustment to the Company's valuation allowance.

Deemed Repatriation Transition Tax: The Deemed Repatriation Transition Tax ("Transition Tax") is a tax on previously untaxed accumulated and current earnings and profits (E&P) of certain of our foreign subsidiaries. To determine the amount of the Transition Tax, the Company must determine, in addition to other factors, the amount of post-1986 E&P of the relevant subsidiaries, as well as the amount of non-U.S. income taxes paid on such earnings. The Company has a cumulative foreign E&P deficit as of December 31, 2017. As such, the Company does not have a transition tax liability in the 2017 tax year.

Global Intangible Low Taxed Income ("GILTI"): The Tax Act creates a new requirement that certain income (i.e., GILTI) earned by a controlled foreign corporations ("CFCs") must be included currently in the gross income of the CFCs' U.S. shareholder. GILTI is the excess of the shareholder’s “net CFC tested income” over the net deemed tangible income return, which is currently defined as the excess of (1) 10 % of the aggregate of the U.S. shareholder’s pro rata share of the qualified business asset investment of each CFC with respect to which it is a U.S. shareholder over (2) the amount of certain interest expense taken into account in the determination of net CFC-tested income. The Company is allowed to make an accounting policy election of either recognizing deferred taxes for temporary differences expected to reverse as GILTI in future years or recognizing such taxes as a current period expense when incurred. GILTI does not have a material impact on our 2018 financial statements

As of December 31, 2018, the Company had unrecognized tax benefits (“UTBs”) of approximately $1.8 million. All of the deferred tax assets associated with these UTBs are fully offset by a valuation allowance. The following table summarizes the activity related to UTBs:


	December 31,
	2018		2017		2016
Unrecognized tax benefits beginning of the period	$	1,219	$	604	$	135
Decrease related to the prior year		—		(51)		—
Increase related to the prior year		—		–		6
Increased related to the current year		585		666		463
Unrecognized tax benefits, end of the period	$	1,804	$	1,219	$	604

The Company follows the provisions of ASC 740, Accounting for Income Taxes, and the accounting guidance related to accounting for uncertainty in income taxes. The Company determines its uncertain tax positions based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be sustained upon examination by the relevant income tax authorities. The Company will recognize both accrued interest and penalties related to unrecognized benefits in income tax expense. The Company currently has no federal or state tax examinations in progress nor has it had any federal or state tax examinations since its inception. As a result of the Company's net operating loss carryforwards, all of its tax years are subject to federal and state tax examination.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies

Commitments and Contingencies

11. Commitments and Contingencies

Facility Lease

In January 2015, the Company signed an initial operating lease, effective February 1, 2015 for 8,138 square feet of office and laboratory space with a one‑year term. Between January 2015 and October 2018, the Company entered into a series of lease amendments to increase the amount of leased space to 27,280 square feet and extend the expiration of the lease to February 2023. The lease agreement includes annual rent escalations. Under the lease and subsequent amendments, the landlord provided approximately $1.9 million in free rent and lease incentives. The Company records rent expense on a straight-line basis over the effective term of the lease, including any free rent periods and incentives. The lease requires the Company to pay additional amounts for operating and maintenance expenses. Rent expense related to the facilities lease for the years ended years ended December 31, 2018, 2017 and 2016 was approximately $748,000, $734,000 and $584,000, respectively. As of December 31, 2018, future minimum lease payments under the facility lease were as follows (in thousands):


Year Ended December 31 (in thousands)
2019	$	1,110
2020		1,142
2021		1,251
2022		1,296
2023		109
Total	$	4,908

In August 2015 the Company entered into an agreement for a line of credit of $0.1 million for the purpose of issuing its landlord a letter of credit of $0.1 million as a security deposit under its facility lease. The Company pledged money market funds and marketable securities as collateral for the line of credit. Pursuant to the Company’s license agreements with each of Vernalis and Scripps, it has obligations to make future milestone and royalty payments to these parties, respectively. However, because these amounts are contingent, they have not been included on the Company’s balance sheet. For further discussion of the Vernalis and Scripps licensing agreements, see Note 5.

Indemnifications

In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third‑party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. There have been no claims to date and the Company has a directors and officers insurance policy that may enable it to recover a portion of any amounts paid for future claims.

Legal Proceedings

The Company is not a party to any material legal proceedings.

Related Party Transaction

12 Months Ended

Dec. 31, 2018

Related Party Transaction

Related Party Transaction

12. Related Party Transactions

In 2017, the Company purchased $461,000 of research services from a vendor during the normal course of business, where a Corvus director is also a member of the vendor's board of directors.

In March 2016, the Company completed its initial public offering of its common stock pursuant to which the Company sold 4,700,000 shares of its common stock. In April 2016, the Company sold an additional 502,618 shares of its common stock to the underwriters upon partial exercise of their over-allotment option, at the initial offering price of $15.00 per share. The Company received aggregate net proceeds of approximately $70.6 million, after underwriting discounts, commissions and offering expenses.

The following aggregate number of shares of common stock were sold to our owners of more than 5% of our common stock, directors, or executive officers during the 2018 and 2016 underwritten public offerings:


	2018 Public Offering				2016 Initial Public Offering
	Number of		Aggregate		Number of		Aggregate
		Shares of	Purchase			Shares of	Purchase
	Common Stock		Price		Common Stock		Price
Owners of More Than 5% of Our Common Stock
FMR LLC		1,176,470	$	9,999,995		850,000	$	12,750,000
Orbimed Advisors LLC (1)		588,235		4,999,998		550,000		8,250,000
Novo Holdings A/S (2)		1,176,470		9,999,995		666,666		9,999,990
Adams Street Partners (3)		588,235		4,999,998		200,000		3,000,000
Board of Directors
Richard A. Miller, M.D.		100,000		850,000		—		—

(1)

Peter Thompson, M.D., a member of our Board of Directors since November 2014, is a Private Equity Partner for OrbiMed Advisors, LLC.

(2)

Peter Moldt, Ph.D., a Partner at Novo Ventures (US) Inc., which provide certain consultancy services to Novo Holdings A/S, served as a member of our Board of Directors from January 2015 to January 2019.

(3)

Elisha P. (Terry) Gould III, a member of our Board of Directors since November 2014, is a Partner at Adams Street Partners, LLC.

Quarterly Selected Financial Data (unaudited)

12 Months Ended

Dec. 31, 2018

Quarterly Selected Financial Data (unaudited)

Quarterly Selected Financial Data (unaudited)

13. Quarterly Selected Financial Data (unaudited)


	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
(in thousands, except per share amounts)	2018		2018		2018		2018
Operating expenses	$	11,171	$	11,149	$	12,258	$	14,644
Net loss		(10,509)		(10,498)		(11,631)		(14,301)
Net loss per share, basic and diluted	$	(0.36)	$	(0.36)	$	(0.40)	$	(0.63)


	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
(in thousands, except per share amounts)	2017		2017		2017		2017
Operating expenses	$	12,189	$	12,944	$	15,174	$	16,217
Net loss		(11,929)		(12,717)		(14,981)		(16,036)
Net loss per share, basic and diluted	$	(0.58)	$	(0.62)	$	(0.73)	$	(0.79)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Summary of Significant Accounting Policies

Basis of Presentation

Use of Estimates

Initial Public Offering

Follow-on Public Offering

Concentrations of Credit Risk and Other Risks and Uncertainties

Segments

Cash and Cash Equivalents and Marketable Securities

Cash, Cash Equivalents and Marketable Securities

The Company considers all highly liquid investment securities with remaining maturities at the date of purchase of three months or less to be cash equivalents.

Fair Value Measurements

Property and Equipment, Net

Property and equipment are stated at cost and depreciated using the straight‑line method over the estimated useful lives of the respective assets:


Laboratory equipment	5	years
Computer equipment and purchased software	3	years
Leasehold improvements	Shorter of asset's useful life or remaining term of lease

Impairment of Long-Lived Assets

Impairment of Long‑Lived Assets

Consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. Intercompany balances and transactions have been eliminated in consolidation.

Research and Development Expenses

employee‑related expenses, including salaries, benefits, travel and non‑cash stock‑based compensation expense;

costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use;

license fees; and

other expenses, which include direct and allocated expenses for laboratory, facilities and other costs.

Clinical Trial Accruals

Stock-Based Compensation

Stock‑Based Compensation

The Company maintains incentive plans under which incentive stock options and nonqualified stock options may be granted to employees and non‑employee service providers.

Income Taxes

Comprehensive Loss

Net Loss per Share

Recent Accounting Pronouncements

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2018

Net Loss per Share

Schedule of net loss per share, basic and diluted


	Year Ended December 31,
	2018		2017		2016
Numerator:
Net loss - basic and diluted	$	(46,939)	$	(55,663)	$	(36,375)
Denominator:
Weighted average common shares outstanding		27,686,909		20,958,557		16,188,980
Less: weighted average common shares subject to repurchase		(176,949)		(470,051)		(766,939)
Weighted average common shares outstanding used to compute basic and diluted net loss per share		27,509,960		20,488,506		15,422,041
Net loss per share, basic and diluted	$	(1.71)	$	(2.72)	$	(2.36)

Schedule of antidilutive securities excluded from calculation of diluted net loss per share



	Year Ended December 31,
	2018	2017	2016
Common stock subject to repurchase	43,076	319,203	611,698
Outstanding options	3,778,259	3,013,394	2,350,582
Total shares of common stock equivalents	3,821,335	3,332,597	2,962,280

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Measurements

Schedule of fair value of assets measured at fair value on a recurring basis, by level of fair value hierarchy


	December 31, 2018
	Fair Value Measured Using						Total
	(Level 1)		(Level 2)		(Level 3)		Balance
Assets
Cash equivalents	$	38,698	$	—	$	—	$	38,698
Marketable securities		—		75,401		—		75,401
	$	38,698	$	75,401	$	—	$	114,099


	December 31, 2017
	Fair Value Measured Using						Total
	(Level 1)		(Level 2)		(Level 3)		Balance
Assets
Cash equivalents	$	44,555	$	—	$	—	$	44,555
Marketable securities		—		44,949		—		44,949
	$	44,555	$	44,949	$	—	$	89,504

Schedule of fair value of available for sale marketable securities

As of December 31, 2018 and 2017, the fair value of available for sale marketable securities by type of security were as follows (in thousands):


	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
U.S. Government agency securities	$	49,124	$	—	$	(27)	$	49,097
Corporate debt obligations		26,311		—		(7)		26,304
	$	75,435	$	—	$	(34)	$	75,401


	December 31, 2017
			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
U.S. Government agency securities	$	32,311	$	—	$	(39)	$	32,272
Corporate debt obligations		12,679		—		(2)		12,677
	$	44,990	$	—	$	(41)	$	44,949

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2018

Balance Sheet Components

Schedule of balance sheet components

Balance Sheet Components (in thousands):


	December 31,
	2018		2017
Prepaid and Other Current Assets
Interest receivable	$	337	$	132
Prepaid research and development manufacturing expenses		75		327
Prepaid facility expenses		149		144
Prepaid insurance		166		164
Other		265		412
	$	992	$	1,179
Property and Equipment
Laboratory equipment	$	2,371	$	2,034
Computer equipment and purchased software		142		130
Leasehold improvements		2,084		2,078
		4,597		4,242
Less: accumulated depreciation and amortization		(2,417)		(1,570)
	$	2,180	$	2,672
Accrued and Other Liabilities
Accrued clinical trial related	$	2,718	$	2,870
Accrued manufacturing expense		1,077		1,056
Personnel related		649		572
Deferred rent		160		410
Accrued legal and accounting		77		224
Other accrued expenses		348		383
	$	5,029	$	5,515
Other Liabilities
Deferred rent	$	869	$	960
Shares subject to vesting		—		11
	$	869	$	971

Common Stock (Tables)

12 Months Ended

Dec. 31, 2018

Common Stock

Schedule of shares of common stock reserved for issuance


	December 31,
	2018	2017	2016
Shares available for future option grants	2,486,637	2,576,535	2,475,600
Outstanding options	3,778,259	3,013,394	2,350,582
Unvested restricted common stock (founders and early exercise of stock options)	43,076	319,203	611,698
Shares reserved for employee stock purchase plan	400,000	400,000	200,000
Total	6,707,972	6,309,132	5,637,880

Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2018

Stock Option Plans

Summary of stock option activity


		Options Outstanding
			Weighted ‑
	Shares		Average
	Available	Number of	Exercise
	for Grant	Options	Price
Balance at December 31, 2017	2,576,535	3,013,394	$	11.78
Additional shares authorized	840,000	—		—
Options granted	(1,449,250)	1,449,250		7.30
Options exercised	—	(165,033)		2.38
Options forfeited	519,352	(519,352)		12.85
Balance at December 31, 2018	2,486,637	3,778,259	$	10.32

Summary of information about stock options outstanding


			Options Outstanding				Options Vested
			at December 31, 2018				at December 31, 2018
				Weighted				Weighted
				Average				Average	Weighted
				Remaining	Weighted			Remaining	Average
				Contractual	Average			Contractual	Exercise
Exercise Price			Number	Life (in Years)	Exercise Price		Number	Life (in Years)	Price
$0.28	-	$4.65	301,803	6.44	$	0.72	261,373	6.42	$	0.68
$5.94	-	$9.52	1,101,750	9.92	$	6.10	3,585	8.69	$	8.92
$9.60	-	$14.43	1,026,180	8.97	$	10.89	269,731	8.70	$	10.56
$15.00	-	$16.70	1,348,526	7.50	$	15.49	834,456	7.38	$	15.37
			3,778,259	8.52	$	10.32	1,369,145	7.46	$	11.60


			Options Outstanding				Options Vested
			at December 31, 2017				at December 31, 2017
				Weighted				Weighted
				Average				Average	Weighted
				Remaining	Weighted			Remaining	Average
				Contractual	Average			Contractual	Exercise
Exercise Price			Number	Life (in Years)	Exercise Price		Number	Life (in Years)	Price
$0.28	-	$4.65	535,136	7.55	$	1.46	325,397	7.53	$	1.34
$6.75	-	$10.60	701,600	9.86	$	10.44	2,688	7.87	$	6.75
$11.21	-	$16.70	1,776,658	8.57	$	15.41	596,727	8.28	$	15.23
			3,013,394	8.69	$	11.78	924,812	8.02	$	11.40

Schedule of options outstanding and exercisable that had vested or were expected to vest


				Weighted
				Average	Aggregate
		Weighted		Remaining	Intrinsic
	Number	Average		Contractual	Value
	of shares	Exercise Price		Life (years)	(in thousands)
Vested	1,369,145	$	11.60	7.46	$	804,162
Expected to vest	2,409,114	$	9.60	6.83	$	115,555

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of expenses relating to employee and non-employee stock-based awards

The Company’s results of operations include expenses relating to employee and non‑employee stock‑based awards as follows (in thousands):



	Year Ended December 31,
	2018		2017		2016
Research and development	$	2,919	$	2,692	$	1,685
General and administrative		4,216		3,537		2,143
Total	$	7,135	$	6,229	$	3,828

Non-employee stock options

Schedule of fair value of share-based awards to employees was estimated using Black Scholes model


	Year Ended December 31,
	2018					2017					2016
Risk-free interest rate	2.55	%	-	3.05	%	2.17	%	-	2.33	%	1.90	%	-	1.94	%
Expected volatility	83.2	%	-	95.2	%	80.3	%	-	83.0	%	92.1	%	-	92.7	%
Expected term (in years)	6.1		-	10.0		7.1		-	7.6		8.1		-	8.6
Expected dividend yield	0	%				0	%				0	%

Employee stock options

Schedule of fair value of share-based awards to employees was estimated using Black Scholes model


	Year Ended December 31,
	2018		2017		2016
Risk-free interest rate	2.8	%	2.1	%	1.6	%
Expected volatility	82.7	%	91.4	%	84.6	%
Expected term (in years)	6.0		6.0		6.0
Expected dividend yield	0	%	0	%	0	%

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Taxes

Schedule of components of loss before income tax

The components of loss before income tax is as follows (in thousands):


	December 31,
	2018		2017		2016
Domestic	$	(47,096)	$	(28,253)	$	(11,375)
Foreign		157		(27,410)		(25,000)
	$	(46,939)	$	(55,663)	$	(36,375)

Schedule of reconciliation of the effective tax rate to the U.S. Federal statutory rate


	December 31,
	2018		2017		2016
Federal tax benefit at statutory rate	21	%	34	%	34	%
State tax, net of Federal benefit	9	%	7	%	8	%
Foreign rate differential	—		(17)	%	(23)	%
Federal rate change impact	—		(9)	%	—
Change in valuation allowance	(41)	%	(16)	%	(19)	%
Research and development tax credits	2	%	2	%	2	%
Prior year federal true-up	10	%	(3)	%	—	%
Other	(1)	%	2	%	(2)
Effective income tax rate	0	%	0	%	0	%

Schedule of principal components of the net deferred tax assets

The principal components of the Company’s net deferred tax assets are as follows (in thousands)


	December 31,
	2018		2017		2016
Net operating loss carryforwards	$	31,533	$	15,438	$	9,339
Tax credit carryforwards		6,441		4,351		1,960
Capitalized tax assets		138		131		241
Accruals		188		183		230
Stock compensation		2,879		1,730		954
Other		58		52		67
Total deferred tax assets		41,237		21,885		12,791
Valuation allowance		(41,237)		(21,885)		(12,791)
Net deferred tax assets	$	—	$	—	$	—

Schedule of unrecognized tax benefits activity


	December 31,
	2018		2017		2016
Unrecognized tax benefits beginning of the period	$	1,219	$	604	$	135
Decrease related to the prior year		—		(51)		—
Increase related to the prior year		—		–		6
Increased related to the current year		585		666		463
Unrecognized tax benefits, end of the period	$	1,804	$	1,219	$	604

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies

Schedule of future minimum lease payments under the facility lease

As of December 31, 2018, future minimum lease payments under the facility lease were as follows (in thousands):


Year Ended December 31 (in thousands)
2019	$	1,110
2020		1,142
2021		1,251
2022		1,296
2023		109
Total	$	4,908

Related Party Transaction (Tables)

12 Months Ended

Dec. 31, 2018

Related Party Transaction

Schedule of common stock sold to related parties


	2018 Public Offering				2016 Initial Public Offering
	Number of		Aggregate		Number of		Aggregate
		Shares of	Purchase			Shares of	Purchase
	Common Stock		Price		Common Stock		Price
Owners of More Than 5% of Our Common Stock
FMR LLC		1,176,470	$	9,999,995		850,000	$	12,750,000
Orbimed Advisors LLC (1)		588,235		4,999,998		550,000		8,250,000
Novo Holdings A/S (2)		1,176,470		9,999,995		666,666		9,999,990
Adams Street Partners (3)		588,235		4,999,998		200,000		3,000,000
Board of Directors
Richard A. Miller, M.D.		100,000		850,000		—		—

(1)

Peter Thompson, M.D., a member of our Board of Directors since November 2014, is a Private Equity Partner for OrbiMed Advisors, LLC.

(2)

(3)

Elisha P. (Terry) Gould III, a member of our Board of Directors since November 2014, is a Partner at Adams Street Partners, LLC.

Quarterly Selected Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Selected Financial Data (unaudited)

Quarterly Selected Financial Data (unaudited)


	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
(in thousands, except per share amounts)	2018		2018		2018		2018
Operating expenses	$	11,171	$	11,149	$	12,258	$	14,644
Net loss		(10,509)		(10,498)		(11,631)		(14,301)
Net loss per share, basic and diluted	$	(0.36)	$	(0.36)	$	(0.40)	$	(0.63)


	Quarter Ended
	December 31,		September 30,		June 30,		March 31,
(in thousands, except per share amounts)	2017		2017		2017		2017
Operating expenses	$	12,189	$	12,944	$	15,174	$	16,217
Net loss		(11,929)		(12,717)		(14,981)		(16,036)
Net loss per share, basic and diluted	$	(0.58)	$	(0.62)	$	(0.73)	$	(0.79)

Summary of Significant Accounting Policies - Basis of Presentation, Credit Risk and Income Taxes (Details) $ / shares in Units, $ in Thousands			1 Months Ended				12 Months Ended
	Apr. 26, 2016 $ / shares shares	Mar. 29, 2016 $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Apr. 30, 2016 USD ($) shares	Apr. 26, 2016 USD ($) $ / shares	Mar. 31, 2016 $ / shares shares	Dec. 31, 2018 USD ($) segment item	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accumulated deficit							$ (170,473)	$ (123,534)
Cash, cash equivalents and marketable securities							114,600
Public Offerings
Proceeds from sale of stock							$ 64,877	$ 711	$ 71,354
Concentrations of Credit Risk and Other Risks and Uncertainties
Number of financial institutions used for cash and cash equivalent deposits \| item							2
Segments
Number of operating segments \| segment							1
IPO
Public Offerings
Share offering price \| $ / shares		$ 15.00				$ 15.00
Issuance of stock (in shares) \| shares		4,700,000				4,700,000
Net proceeds from IPO				$ 70,600	$ 70,600
Over-Allotment Option
Public Offerings
Share offering price \| $ / shares	$ 15.00				$ 15.00
Issuance of stock (in shares) \| shares	502,618		1,058,823	502,618
Follow On Public Offering
Public Offerings
Share offering price \| $ / shares			$ 8.50
Issuance of stock (in shares) \| shares			8,117,647
Proceeds from sale of stock			$ 64,900

Summary of Significant Accounting Policies - Income Taxes (Details) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2018	Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effect of Tax Cut and Jobs Act
Corporate income tax rate (as a percent)	21.00%	35.00%	21.00%	34.00%	34.00%
Net tax benefit related to change in net deferred tax assets				$ (4.9)
Amount of adjustment to the valuation allowance to offset decrease in net deferred tax asset				$ (4.9)

Net Loss per Share - Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss - basic and diluted	$ (10,509)	$ (10,498)	$ (11,631)	$ (14,301)	$ (11,929)	$ (12,717)	$ (14,981)	$ (16,036)	$ (46,939)	$ (55,663)	$ (36,375)
Denominator:
Weighted average common shares outstanding									27,686,909	20,958,557	16,188,980
Less: weighted average common shares subject to repurchase									(176,949)	(470,051)	(766,939)
Weighted average common shares outstanding used to compute basic and diluted net loss per share									27,509,960	20,488,506	15,422,041
Net loss per share, basic and diluted (in dollars per share)	$ (0.36)	$ (0.36)	$ (0.40)	$ (0.63)	$ (0.58)	$ (0.62)	$ (0.73)	$ (0.79)	$ (1.71)	$ (2.72)	$ (2.36)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss per Share - Anti-Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Excluded from the calculation of diluted net loss per share, due to anti-dilutive effect
Shares of common stock equivalents	3,821,335	3,332,597	2,962,280
Common stock subject to repurchase
Excluded from the calculation of diluted net loss per share, due to anti-dilutive effect
Shares of common stock equivalents	43,076	319,203	611,698
Outstanding options
Excluded from the calculation of diluted net loss per share, due to anti-dilutive effect
Shares of common stock equivalents	3,778,259	3,013,394	2,350,582

Fair Value Measurements - Recurring (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Assets
Maximum remaining maturity of marketable securities	10 months
Level 1
Transfer between levels
Transfer of assets from level 1 to 2	$ 0	$ 0
Transfer of liabilities from level 1 to 2	0	0
Level 2
Transfer between levels
Transfer of assets from level 2 to 1	0	0
Transfer of liabilities from level 2 to 1	0	0
Level 3
Transfer between levels
Transfer of assets into level 3	0	0
Transfer of assets out of level 3	0	0
Transfer of liabilities into level 3	0	0
Transfer of liabilities out of level 3	0	0
Recurring
Assets
Cash equivalents	38,698	44,555
Marketable securities	75,401	44,949
Total Assets	114,099	89,504
Recurring \| Level 1
Assets
Cash equivalents	38,698	44,555
Total Assets	38,698	44,555
Recurring \| Level 2
Assets
Marketable securities	75,401	44,949
Total Assets	$ 75,401	$ 44,949

Fair Value Measurements - Available For Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair value of available for sale marketable securities
Amortized Cost	$ 75,435	$ 44,990
Gross Unrealized Losses	(34)	(41)
Fair Value	75,401	44,949
U.S. Government agency securities
Fair value of available for sale marketable securities
Amortized Cost	49,124	32,311
Gross Unrealized Losses	(27)	(39)
Fair Value	49,097	32,272
Corporate debt obligations
Fair value of available for sale marketable securities
Amortized Cost	26,311	12,679
Gross Unrealized Losses	(7)	(2)
Fair Value	$ 26,304	$ 12,677

License and Collaboration Agreements (Details)	1 Months Ended		12 Months Ended
License and Collaboration Agreements (Details)	May 31, 2017 item	Feb. 28, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2018 USD ($)	Feb. 28, 2017 USD ($)
Licensing Agreement \| Scripps Research Institute
License and Collaboration Agreements
Minimum annual fee			$ 25,000
Aggregate potential milestone payments			$ 2,600,000
Milestone payments made				$ 0
Period of written notice to terminate			90 days
Licensing Agreement \| Scripps Research Institute \| Research and development
License and Collaboration Agreements
One-time cash payment			$ 10,000
Licensing Agreement \| Vernalis (R&D) Limited
License and Collaboration Agreements
Milestone payments made					$ 3,000,000
Period of written notice to terminate		90 days
Licensing Agreement \| Vernalis (R&D) Limited \| Minimum
License and Collaboration Agreements
Aggregate potential milestone payments		$ 220,000,000
Licensing Agreement \| Vernalis (R&D) Limited \| Research and development
License and Collaboration Agreements
One-time cash payment		$ 1,000,000
Clinical Trial Collaboration Agreement \| Genentech \| Maximum
License and Collaboration Agreements
Maximum number of patients in treatment arm under collaboration agreement \| item	65

Balance Sheet Components - Prepaid and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Prepaid and Other Current Assets
Interest receivable	$ 337	$ 132
Prepaid research and development manufacturing expenses	75	327
Prepaid facility expenses	149	144
Prepaid insurance	166	164
Other	265	412
Total of prepaid and other current assets	$ 992	$ 1,179

Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property and Equipment
Property and equipment, gross	$ 4,597	$ 4,242
Less: accumulated depreciation and amortization	(2,417)	(1,570)
Property and equipment, net	2,180	2,672
Laboratory equipment
Property and Equipment
Property and equipment, gross	2,371	2,034
Computer equipment and purchased software
Property and Equipment
Property and equipment, gross	142	130
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 2,084	$ 2,078

Balance Sheet Components - Accrued and Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued and Other Liabilities
Accrued clinical trial related	$ 2,718	$ 2,870
Accrued manufacturing expense	1,077	1,056
Personnel related	649	572
Deferred rent	160	410
Accrued legal and accounting	77	224
Other accrued expenses	348	383
Total of accrued and other liabilities	$ 5,029	$ 5,515

Balance Sheet Components - Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Other Liabilities
Deferred rent	$ 869	$ 960
Shares subject to vesting		11
Total of other liabilities	$ 869	$ 971

Common Stock (Details)		12 Months Ended
Common Stock (Details)	Sep. 20, 2017 USD ($)	Dec. 31, 2018 USD ($) Vote shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Common Stock
Common stock, shares authorized for issuance		290,000,000	290,000,000
Preferred stock, shares authorized for issuance		10,000,000	10,000,000
Number of votes per share of common stock \| Vote		1
Dividends on common stock \| $		$ 0
Proceeds from sale of stock \| $		$ 64,877,000	$ 711,000	$ 71,354,000
Shares of common stock reserved for issuance, on an as-converted basis
Shares available for future option grants		2,486,637	2,576,535	2,475,600
Outstanding options		3,778,259	3,013,394	2,350,582
Unvested restricted common stock (founders and early exercise of stock options)		43,076	319,203	611,698
Shares reserved for employee stock purchase plan		400,000	400,000	200,000
Total		6,707,972	6,309,132	5,637,880
At-the-market offering
Common Stock
Proceeds from sale of stock \| $		$ 0	$ 700,000
At-the-market offering \| Cowen
Common Stock
Potential gross proceeds \| $	$ 125,000,000
Stock issuance costs, as a percent of gross proceeds	3.00%

Stock Option Plans - Stock Option Activity (Details) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Mar. 29, 2016 item	Mar. 31, 2016 shares	Feb. 28, 2014	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) shares
Shares Available for Grant
Beginning balance				2,576,535	2,475,600
Exercised \| $				$ 393	$ 731	$ 4
Ending balance				2,486,637	2,576,535	2,475,600
Number of Options
Beginning balance				3,013,394	2,350,582
Ending balance				3,778,259	3,013,394	2,350,582
2014 Plan
Stock Option Plans
Vesting period			4 years
Maximum exercise term			10 years
Exercise price of common stock of its fair value (as a percent)			100.00%
Number of awards to be granted in future \| item	0
Maximum number of options that may be re-issued under the 2016 plan		1,136,229
2016 Plan
Stock Option Plans
Vesting period		4 years
Maximum exercise term		10 years
Exercise price of common stock of its fair value (as a percent)		100.00%
Shares Available for Grant
Beginning balance				2,576,535
Additional shares authorized				840,000
Granted				(1,449,250)
Forfeited				519,352
Ending balance				2,486,637	2,576,535
Number of Options
Beginning balance				3,013,394
Granted				1,449,250
Exercised					(165,033)
Forfeited				(519,352)
Ending balance				3,778,259	3,013,394
Weighted-Average Exercise Price
Beginning balance (in dollars per share) \| $ / shares				$ 11.78
Granted (in dollars per share) \| $ / shares				7.30
Exercised (in dollars per share) \| $ / shares					$ 2.38
Forfeited (in dollars per share) \| $ / shares				12.85
Ending balance (in dollars per share) \| $ / shares				$ 10.32	$ 11.78

Stock Option Plan - Exercise Price Range (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Information about stock options outstanding
Options Outstanding, Number	3,778,259	3,013,394
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 6 months 7 days	8 years 8 months 9 days
Weighted average exercise price of options outstanding (in dollars per share)	$ 10.32	$ 11.78
Options Vested, Number	1,369,145	924,812
Options Vested, Weighted Average Remaining Contractual Life	7 years 5 months 16 days	8 years 7 days
Weighted average exercise price of options vested (in dollars per share)	$ 11.60	$ 11.40
Weighted average grant date fair value of options granted (in dollars per share)	5.23	8.93	$ 10.78
$0.28 - $4.65
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)	0.28	0.28
Exercise Price, high end of range (in dollars per share)	$ 4.65	$ 4.65
Options Outstanding, Number	301,803	535,136
Options Outstanding, Weighted Average Remaining Contractual Life	6 years 5 months 9 days	7 years 6 months 18 days
Weighted average exercise price of options outstanding (in dollars per share)	$ 0.72	$ 1.46
Options Vested, Number	261,373	325,397
Options Vested, Weighted Average Remaining Contractual Life	6 years 5 months 1 day	7 years 6 months 11 days
Weighted average exercise price of options vested (in dollars per share)	$ 0.68	$ 1.34
$6.75 - $10.60
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)		6.75
Exercise Price, high end of range (in dollars per share)		$ 10.60
Options Outstanding, Number		701,600
Options Outstanding, Weighted Average Remaining Contractual Life		9 years 10 months 10 days
Weighted average exercise price of options outstanding (in dollars per share)		$ 10.44
Options Vested, Number		2,688
Options Vested, Weighted Average Remaining Contractual Life		7 years 10 months 13 days
Weighted average exercise price of options vested (in dollars per share)		$ 6.75
$11.21 - $16.70
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)		11.21
Exercise Price, high end of range (in dollars per share)		$ 16.70
Options Outstanding, Number		1,776,658
Options Outstanding, Weighted Average Remaining Contractual Life		8 years 6 months 26 days
Weighted average exercise price of options outstanding (in dollars per share)		$ 15.41
Options Vested, Number		596,727
Options Vested, Weighted Average Remaining Contractual Life		8 years 3 months 11 days
Weighted average exercise price of options vested (in dollars per share)		$ 15.23
$5.94 - $9.52
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)	5.94
Exercise Price, high end of range (in dollars per share)	$ 9.52
Options Outstanding, Number	1,101,750
Options Outstanding, Weighted Average Remaining Contractual Life	9 years 11 months 1 day
Weighted average exercise price of options outstanding (in dollars per share)	$ 6.10
Options Vested, Number	3,585
Options Vested, Weighted Average Remaining Contractual Life	8 years 8 months 9 days
Weighted average exercise price of options vested (in dollars per share)	$ 8.92
$9.60 - $14.43
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)	9.60
Exercise Price, high end of range (in dollars per share)	$ 14.43
Options Outstanding, Number	1,026,180
Options Outstanding, Weighted Average Remaining Contractual Life	8 years 11 months 19 days
Weighted average exercise price of options outstanding (in dollars per share)	$ 10.89
Options Vested, Number	269,731
Options Vested, Weighted Average Remaining Contractual Life	8 years 8 months 12 days
Weighted average exercise price of options vested (in dollars per share)	$ 10.56
$15.00 - $16.70
Information about stock options outstanding
Exercise Price, low end of range (in dollars per share)	15.00
Exercise Price, high end of range (in dollars per share)	$ 16.70
Options Outstanding, Number	1,348,526
Options Outstanding, Weighted Average Remaining Contractual Life	7 years 6 months
Weighted average exercise price of options outstanding (in dollars per share)	$ 15.49
Options Vested, Number	834,456
Options Vested, Weighted Average Remaining Contractual Life	7 years 4 months 17 days
Weighted average exercise price of options vested (in dollars per share)	$ 15.37

Stock Option Plan - Vested or Expected to Vest (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Options outstanding and exercisable
Vested, Number of Shares (in shares)	1,369,145
Vested, Weighted Average Exercise Price (in dollars per share)	$ 11.60
Vested, Weighted Average Remaining Contractual Life	7 years 5 months 16 days
Vested, Aggregate Intrinsic Value	$ 804,162
Expected to vest, Number of Shares (in shares)	2,409,114
Expected to vest, Weighted Average Exercise Price (in dollars per share)	$ 9.60
Expected to vest, Weighted Average Remaining Contractual Life	6 years 9 months 29 days
Expected to vest, Aggregate Intrinsic Value	$ 115,555
Fair value of common stock (in dollars per share)	$ 3.67
Aggregate intrinsic value of stock options exercised	$ 1,100	$ 300	$ 200
Fair value of options vested	$ 7,100	$ 5,800	$ 3,200

Stock-Based Compensation - Expense Allocation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-based compensation
Stock-based compensation expense	$ 7,135	$ 6,229	$ 3,828
Research and development
Stock-based compensation
Stock-based compensation expense	2,919	2,692	1,685
General and administrative
Stock-based compensation
Stock-based compensation expense	$ 4,216	$ 3,537	$ 2,143

Stock Based Compensation -Valuation Assumptions Employees (Details) - Employee stock options - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Weighted-average assumptions used to estimate fair value of share-based awards
Risk-free interest rate	2.80%	2.10%	1.60%
Expected volatility	82.70%	91.40%	84.60%
Expected term (in years)	6 years	6 years	6 years
Expected dividend yield	0.00%	0.00%	0.00%
Unrecognized compensation expense	$ 15.8	$ 18.6	$ 18.5
Expected period for recognizing compensation expense	2 years 8 months 19 days	2 years 10 months 6 days	3 years 3 months 11 days

Stock Based Compensation -Valuation Assumptions Non-Employees (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Option Plans
Stock-based compensation expense	$ 7,135,000	$ 6,229,000	$ 3,828,000
Non-employee stock options
Stock Option Plans
Stock-based compensation expense	$ 52,000	$ 74,000	$ 142,500
Weighted-average assumptions used to estimate fair value of share-based awards
Risk-free interest rate, minimum	2.55%	2.17%	1.90%
Risk-free interest rate, maximum	3.05%	2.33%	1.94%
Expected Volatility, minimum	83.20%	80.30%	92.10%
Expected Volatility, maximum	95.20%	83.00%	92.70%
Expected dividend yield	0.00%	0.00%	0.00%
Non-employee stock options \| Minimum
Weighted-average assumptions used to estimate fair value of share-based awards
Expected term (in years)	6 years 1 month 6 days	7 years 1 month 6 days	8 years 1 month 6 days
Non-employee stock options \| Maximum
Weighted-average assumptions used to estimate fair value of share-based awards
Expected term (in years)	10 years	7 years 7 months 6 days	8 years 7 months 6 days

Income Taxes - Components of loss before income tax and Income tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Income tax benefits	$ 0	$ 0	$ 0
Components of loss before income tax
Domestic	(47,096)	(28,253)	(11,375)
Foreign	157	(27,410)	(25,000)
Total	$ (46,939)	$ (55,663)	$ (36,375)

Income Taxes - Reconciliation of effective tax rate (Details)			12 Months Ended
	Jan. 01, 2018	Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of the effective tax rate to the U.S. Federal statutory rate
Federal tax benefit at statutory rate	21.00%	35.00%	21.00%	34.00%	34.00%
State tax, net of Federal benefit			9.00%	7.00%	8.00%
Foreign rate differential				(17.00%)	(23.00%)
Federal rate change impact				(9.00%)
Change in valuation allowance			(41.00%)	(16.00%)	(19.00%)
Research and development tax credits			2.00%	2.00%	2.00%
Prior year federal true-up			10.00%	(3.00%)
Other			(1.00%)	2.00%	(2.00%)
Effective income tax rate			0.00%	0.00%	0.00%

Income Taxes - Deferred tax assets net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carryforwards	$ 31,533	$ 15,438	$ 9,339
Tax credit carryforwards	6,441	4,351	1,960
Capitalized tax assets	138	131	241
Accruals	188	183	230
Stock compensation	2,879	1,730	954
Other	58	52	67
Total deferred tax assets	41,237	21,885	12,791
Valuation allowance	(41,237)	(21,885)	(12,791)
Net deferred tax assets	0	0	$ 0
Increase in valuation allowance	$ 19,400	$ 9,100

Income Taxes - Operating loss carryforwards (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Net operating loss carryforwards
NOL utilized	$ 0.0
Tax benefits from deferred tax assets after valuation allowance	0.0
Federal
Net operating loss carryforwards
NOL carryforwards	105.3
State
Net operating loss carryforwards
NOL carryforwards	$ 134.8

Income Taxes - Tax credit carry forwards (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Tax credit carryforwards
Common stock, shares issued	29,323,930	21,041,250
Research and development credits \| Federal
Tax credit carryforwards
Research and development tax credit carryforwards	$ 4.4
Research and development credits \| State
Tax credit carryforwards
Research and development tax credit carryforwards	$ 3.7

Income Taxes - Tax Cut and Jobs Act (Details) - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2018	Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effect of Tax Cut and Jobs Act
Corporate income tax rate (as a percent)	21.00%	35.00%	21.00%	34.00%	34.00%
Net tax benefit related to change in net deferred tax assets				$ (4.9)
Amount of adjustment to the valuation allowance to offset decrease in net deferred tax asset				$ (4.9)
Provisional estimate of taxes due to Tax Act			$ 0.0

Income Taxes - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of unrecognized tax benefits
Unrecognized tax benefits beginning of the period	$ 1,219	$ 604	$ 135
Decrease related to the prior year		(51)
Increase related to the prior year			6
Increased related to the current year	585	666	463
Unrecognized tax benefits, end of the period	$ 1,804	$ 1,219	$ 604

Commitments and Contingencies (Details)	12 Months Ended
Commitments and Contingencies (Details)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 31, 2018 ft²	Jan. 31, 2015 ft²
Commitments and Contingencies
Area of leased facility \| ft²				27,280	8,138
Lease term					1 year
Landlord Provided Free Rent And Lease Incentives	$ 1,900,000
Rent expense	748,000	$ 734,000	$ 584,000
Future minimum lease payments
2019	1,110,000
2020	1,142,000
2021	1,251,000
2022	1,296,000
2023	109,000
Total	$ 4,908,000

Commitments and Contingencies - Line of Credit (Details) $ in Millions	Aug. 31, 2015 USD ($)
Line of credit
Security deposit	$ 0.1
Secured debt
Line of credit
Line of credit	$ 0.1

Related Party Transaction (Details) - USD ($)			1 Months Ended				12 Months Ended
Related Party Transaction (Details) - USD ($)	Apr. 26, 2016	Mar. 29, 2016	Mar. 31, 2018	Apr. 30, 2016	Apr. 26, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Public Offerings
Proceeds from sale of stock							$ 64,877,000	$ 711,000	$ 71,354,000
Director
Related Party Transaction
Purchase of research services								$ 461,000
IPO
Public Offerings
Share offering price		$ 15.00				$ 15.00
Number of Share of Common Stock issued		4,700,000				4,700,000
Net proceeds from IPO				$ 70,600,000	$ 70,600,000
IPO \| FMR LLC
Public Offerings
Number of Share of Common Stock issued						850,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price						$ 12,750,000
IPO \| Orbimed Advisors LLC
Public Offerings
Number of Share of Common Stock issued						550,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price						$ 8,250,000
IPO \| Novo Holdings A/S
Public Offerings
Number of Share of Common Stock issued						666,666
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price						$ 9,999,990
IPO \| Adams Street Partners
Public Offerings
Number of Share of Common Stock issued						200,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price						$ 3,000,000
Over-Allotment Option
Public Offerings
Share offering price	$ 15.00				$ 15.00
Number of Share of Common Stock issued	502,618		1,058,823	502,618
Follow On Public Offering
Public Offerings
Share offering price			$ 8.50
Number of Share of Common Stock issued			8,117,647
Proceeds from sale of stock			$ 64,900,000
Follow On Public Offering \| FMR LLC
Public Offerings
Number of Share of Common Stock issued			1,176,470
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price			$ 9,999,995
Follow On Public Offering \| Orbimed Advisors LLC
Public Offerings
Number of Share of Common Stock issued			588,235
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price			$ 4,999,998
Follow On Public Offering \| Novo Holdings A/S
Public Offerings
Number of Share of Common Stock issued			1,176,470
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price			$ 9,999,995
Follow On Public Offering \| Adams Street Partners
Public Offerings
Number of Share of Common Stock issued			588,235
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price			$ 4,999,998
Follow On Public Offering \| Director
Public Offerings
Number of Share of Common Stock issued			100,000
Owners of More Than 5% of Our Common Stock or Board of Directors
Aggregate Purchase Price			$ 850,000

Quarterly Selected Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Selected Financial Data (unaudited)
Operating Expenses	$ 11,171	$ 11,149	$ 12,258	$ 14,644	$ 12,189	$ 12,944	$ 15,174	$ 16,217	$ 49,222	$ 56,524	$ 36,976
Net loss	$ (10,509)	$ (10,498)	$ (11,631)	$ (14,301)	$ (11,929)	$ (12,717)	$ (14,981)	$ (16,036)	$ (46,939)	$ (55,663)	$ (36,375)
Net loss per share, basic and diluted (in dollars per share)	$ (0.36)	$ (0.36)	$ (0.40)	$ (0.63)	$ (0.58)	$ (0.62)	$ (0.73)	$ (0.79)	$ (1.71)	$ (2.72)	$ (2.36)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF CASH FLOW (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2016
CONSOLIDATED STATEMENTS OF CASH FLOWS
Proceeds from issuance of common stock, net, from related parties	$ 30,850	$ 34,000

Organization	12 Months Ended
Organization	Dec. 31, 2018
Organization
Organization	1. Organization Corvus Pharmaceuticals, Inc. (“Corvus” or the “Company”) was incorporated in Delaware on January 27, 2014 and commenced operations in November 2014. Corvus is a clinical stage biopharmaceutical company focused on the development and commercialization of precisely targeted oncology therapies. The Company’s operations are located in Burlingame, California. The Company has four insignificant subsidiaries.

Organization (Details)	12 Months Ended
Organization (Details)	Dec. 31, 2018 subsidiary
Organization
Number of insignificant subsidiaries	4

Summary of Significant Accounting Policies - Property and Equipment, Net (Details)	12 Months Ended
	Dec. 31, 2018
Laboratory equipment
Property and Equipment, Net
Estimated Useful lives	5 years
Computer equipment and purchased software
Property and Equipment, Net
Estimated Useful lives	3 years