Vir Biotechnology (VIR) 10-Q 19 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 15, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	VIR
Title of 12(b) Security	Common stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity Registrant Name	Vir Biotechnology, Inc.
Entity Central Index Key	0001706431
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		109,678,822
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Shell Company	false
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-39083
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-2730369
Entity Address, Address Line One	499 Illinois Street, Suite 500,
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94158
City Area Code	415
Local Phone Number	906-4324

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
CURRENT ASSETS:
Cash and cash equivalents	$ 93,698	$ 47,598
Short-term investments	226,512	50,845
Restricted cash and cash equivalents, current	8,822	10,761
Prepaid expenses and other current assets	8,688	8,579
Total current assets	337,720	117,783
Intangible assets, net	35,999	36,917
Goodwill	16,937	16,937
Property and equipment, net	15,448	12,290
Restricted cash and cash equivalents, noncurrent	2,850	1,003
Other assets	13,688	6,666
TOTAL ASSETS	422,642	191,596
CURRENT LIABILITIES:
Accounts payable	5,815	6,473
Accrued liabilities	22,953	14,534
Deferred revenue, current portion	8,822	8,761
Advanced proceeds from preferred stock financing		10,140
Contingent consideration, current portion	6,726
Total current liabilities	44,316	39,908
Deferred revenue, noncurrent	8,408	6,561
Convertible preferred stock warrant liability	4,425	1,024
Contingent consideration, noncurrent	3,343	9,250
Deferred tax liability	3,305	3,305
Other long-term liabilities	3,030	1,588
TOTAL LIABILITIES	66,827	61,636
Commitments and contingencies (Note 7)
Convertible preferred stock, $0.0001 par value; 421,450,000 shares authorized; 88,112,733 and 69,910,520 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively; aggregate liquidation preference of $675,567 and $333,058 as of September 30, 2019 and December 31, 2018, respectively	636,612	309,137
STOCKHOLDERS’ DEFICIT:
Common stock, $0.0001 par value; 558,350,000 shares authorized as of September 30, 2019 and December 31, 2018; 11,728,232 and 8,858,799 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively	1	1
Additional paid-in capital	23,869	14,672
Accumulated other comprehensive income (loss)	81	(14)
Accumulated deficit	(304,748)	(193,836)
TOTAL STOCKHOLDERS’ DEFICIT	(280,797)	(179,177)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ DEFICIT	$ 422,642	$ 191,596

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	421,450,000	421,450,000
Convertible preferred stock, shares issued	88,112,733	69,910,520
Convertible preferred stock, shares outstanding	88,112,733	69,910,520
Convertible preferred stock, liquidation	$ 675,567	$ 333,058
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	558,350,000	558,350,000
Common stock, shares issued	11,728,232	8,858,799
Common stock, shares outstanding	11,728,232	8,858,799

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenue	$ 1,403	$ 2,885	$ 7,111	$ 7,542
Operating expenses:
Research and development	39,863	29,837	95,541	78,256
General and administrative	9,220	7,394	25,790	21,182
Total operating expenses	49,083	37,231	121,331	99,438
Loss from operations	(47,680)	(34,346)	(114,220)	(91,896)
Other income (expense):
Interest income	2,012	712	6,564	1,919
Other income (expense), net	(2,659)	178	(3,251)	(14)
Total other income (expense), net	(647)	890	3,313	1,905
Loss before benefit from (provision for) income taxes	(48,327)	(33,456)	(110,907)	(89,991)
Benefit from (provision for) income taxes	13		(5)	500
Net loss	$ (48,314)	$ (33,456)	$ (110,912)	$ (89,491)
Net loss per share, basic and diluted	$ (4.60)	$ (4.16)	$ (11.53)	$ (12.20)
Weighted-average shares outstanding, basic and diluted	10,500,848	8,043,283	9,615,379	7,333,986
Grant Revenue [Member]
Revenues:
Total revenue	$ 1,166	$ 2,771	$ 6,771	$ 6,680
Contract Revenue [Member]
Revenues:
Total revenue	$ 237	$ 114	$ 340	$ 862

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Net loss	$ (48,314)	$ (33,456)	$ (110,912)	$ (89,491)
Other comprehensive income (loss):
Unrealized gains (losses) on investments, net of tax	(159)	(25)	95	(41)
Other comprehensive income (loss)	(159)	(25)	95	(41)
Comprehensive loss	$ (48,473)	$ (33,481)	$ (110,817)	$ (89,532)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017		$ 292,525
Beginning balance (in shares) at Dec. 31, 2017		65,944,430
Beginning balance (in shares) at Dec. 31, 2017						6,210,325
Beginning balance at Dec. 31, 2017	$ (68,916)					$ 1	$ 9,035		$ (77,952)
Issuance of convertible preferred stock, net of issuance cost			$ 14,269	$ 2,343
Issuance of convertible preferred stock, net of issuance cost (in Shares)			3,222,220	743,870
Vesting of restricted common stock (in shares)						1,910,597
Exercise of stock options	325						325
Exercise of stock option (in shares)						219,342
Stock-based compensation	4,101						4,101
Other comprehensive income (loss)	(41)							$ (41)
Net loss	(89,491)								(89,491)
Ending balance at Sep. 30, 2018		$ 309,137
Ending balance (in shares) at Sep. 30, 2018		69,910,520
Ending balance (in shares) at Sep. 30, 2018						8,340,264
Ending balance at Sep. 30, 2018	(154,022)					$ 1	13,461	(41)	(167,443)
Beginning balance at Jun. 30, 2018		$ 307,186
Beginning balance (in shares) at Jun. 30, 2018		69,466,076
Beginning balance (in shares) at Jun. 30, 2018						7,515,382
Beginning balance at Jun. 30, 2018	(122,301)					$ 1	11,701	(16)	(133,987)
Issuance of convertible preferred stock, net of issuance cost			$ 1,951
Issuance of convertible preferred stock, net of issuance cost (in Shares)			444,444
Vesting of restricted common stock (in shares)						615,261
Exercise of stock options	311						311
Exercise of stock option (in shares)						209,621
Stock-based compensation	1,449						1,449
Other comprehensive income (loss)	(25)							(25)
Net loss	(33,456)								(33,456)
Ending balance at Sep. 30, 2018		$ 309,137
Ending balance (in shares) at Sep. 30, 2018		69,910,520
Ending balance (in shares) at Sep. 30, 2018						8,340,264
Ending balance at Sep. 30, 2018	(154,022)					$ 1	13,461	(41)	(167,443)
Beginning balance at Dec. 31, 2018	$ 309,137	$ 309,137	$ 303,224	$ 5,913
Beginning balance (in shares) at Dec. 31, 2018	69,910,520	69,910,520
Beginning balance (in shares) at Dec. 31, 2018	8,858,799					8,858,799
Beginning balance at Dec. 31, 2018	$ (179,177)					$ 1	14,672	(14)	(193,836)
Issuance of convertible preferred stock, net of issuance cost					$ 327,475
Issuance of convertible preferred stock, net of issuance cost (in Shares)					18,202,213
Issuance of common stock in connection with a license agreement	617						617
Issuance of common stock in connection with a license agreement (in shares)						38,888
Repayment of promissory notes, net of unvested common stock	1,355						1,355
Repayment of promissory note, net of unvested common stock (in shares)						1,390,925
Vesting of restricted common stock	119						119
Vesting of restricted common stock (in shares)						733,041
Exercise of stock options	1,066						1,066
Exercise of stock option (in shares)						706,579
Stock-based compensation	6,040						6,040
Other comprehensive income (loss)	95							95
Net loss	(110,912)								(110,912)
Ending balance at Sep. 30, 2019	$ 636,612	$ 636,612	303,224	5,913	$ 327,475
Ending balance (in shares) at Sep. 30, 2019	88,112,733	88,112,733
Ending balance (in shares) at Sep. 30, 2019	11,728,232					11,728,232
Ending balance at Sep. 30, 2019	$ (280,797)					$ 1	23,869	81	(304,748)
Beginning balance at Jun. 30, 2019		$ 636,612
Beginning balance (in shares) at Jun. 30, 2019		88,112,733
Beginning balance (in shares) at Jun. 30, 2019						9,722,838
Beginning balance at Jun. 30, 2019	(236,967)					$ 1	19,226	240	(256,434)
Issuance of common stock in connection with a license agreement	617						617
Issuance of common stock in connection with a license agreement (in shares)						38,888
Repayment of promissory notes, net of unvested common stock	1,355						1,355
Repayment of promissory note, net of unvested common stock (in shares)						1,390,925
Vesting of restricted common stock	119						119
Vesting of restricted common stock (in shares)						337,075
Exercise of stock options	364						364
Exercise of stock option (in shares)						238,506
Stock-based compensation	2,188						2,188
Other comprehensive income (loss)	(159)							(159)
Net loss	(48,314)								(48,314)
Ending balance at Sep. 30, 2019	$ 636,612	$ 636,612	$ 303,224	$ 5,913	$ 327,475
Ending balance (in shares) at Sep. 30, 2019	88,112,733	88,112,733
Ending balance (in shares) at Sep. 30, 2019	11,728,232					11,728,232
Ending balance at Sep. 30, 2019	$ (280,797)					$ 1	$ 23,869	$ 81	$ (304,748)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Series A-1 Convertible Preferred Stock
Convertible preferred stock, net of issuance cost	$ 50		$ 182
Series B Convertible Preferred Stock
Convertible preferred stock, net of issuance cost		$ 165

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (110,912)	$ (89,491)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on disposal of property and equipment		198
Depreciation and amortization	2,435	1,025
Amortization of intangible assets	918	833
Amortization of premiums (accretion of discounts) on investments, net	(571)	(323)
Change in fair value of contingent consideration	819	1,850
Change in estimated fair value of convertible preferred stock warrant liability	3,401	(70)
Preferred stock issued in connection with asset acquisition		1,750
Common stock issued in connection with license agreement	617
Change in deferred income taxes		(500)
Stock-based compensation	6,040	4,101
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(109)	(3,348)
Other assets	(1,399)	(157)
Accounts payable	428	2,705
Accrued liabilities and other long-term liabilities	5,678	6,066
Deferred revenue	1,908	10,773
Net cash used in operating activities	(90,747)	(64,588)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(7,388)	(5,391)
Purchases of short-term investments	(495,934)	(105,240)
Maturities of short-term investments	320,933	35,810
Proceeds from sale of property and equipment		25
Asset acquisitions		(1,743)
Net cash used in investing activities	(182,389)	(76,539)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to initial public offering	(3,686)
Proceeds from issuance of convertible preferred stock, net of issuance costs	317,335	14,215
Proceeds received from financing obligation	1,202
Payment of principal on financing lease obligations	(38)
Proceeds from repayment of promissory notes	3,265
Proceeds from exercise of stock options	1,066	325
Net cash provided by financing activities	319,144	14,540
Net increase (decrease) in cash, cash equivalents and restricted cash and cash equivalents	46,008	(126,587)
Cash, cash equivalents and restricted cash and cash equivalents at beginning of period	59,362	188,921
Cash, cash equivalents and restricted cash and cash equivalents at end of period	105,370	62,334
NONCASH INVESTING AND FINANCING ACTIVITIES:
Property and equipment purchases included in accounts payable and accrued liabilities	200	377
Issuance costs for convertible preferred stock included in accounts payable and accrued liabilities		54
Issuance of preferred stock in connection with asset acquisition		593
Deferred issuance costs incurred and not paid	1,938
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH AND CASH EQUIVALENTS TO THE CONDENSED CONSOLIDATED BALANCE SHEETS:
Cash and cash equivalents	93,698	47,670
Restricted cash and cash equivalents, current	8,822	13,661
Restricted cash and cash equivalents, noncurrent	2,850	1,003
Cash, cash equivalents and restricted cash and cash equivalents at end of period	$ 105,370	$ 62,334

Organization

Organization	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Organization	1. Vir Biotechnology, Inc. (“Vir” or the “Company”) is a clinical-stage immunology company focused on combining immunologic insights with cutting-edge technologies to treat and prevent serious infectious diseases. The Company’s approach begins with identifying the limitations of the immune system in combating a particular pathogen, the vulnerabilities of that pathogen and the reasons why previous approaches have failed. The Company then brings to bear powerful technologies that the Company believes, individually or in combination, will lead to effective therapies. Reverse Stock Split On September 16, 2019, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-4.5 reverse split (“Reverse Split”) of shares of the Company’s common and convertible preferred stock, which was effected on September 27, 2019. The par value per share and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the Reverse Split. All of the share and per share information included in the accompanying condensed consolidated financial statements has been adjusted to reflect the Reverse Split. Initial Public Offering On October 10, 2019, the Company completed its initial public offering (“IPO”) of its common stock. In connection with its IPO, the Company issued and sold 7,142,858 shares of its common stock at a price of $20.00 per share. As a result of the IPO, the Company received $127.2 million in net proceeds, after deducting underwriting discounts, commissions and estimated offering expenses. At the closing of the IPO, 88,112,733 shares of outstanding convertible preferred stock were automatically converted into 88,112,733 shares of common stock and a warrant to purchase 244,444 shares of convertible preferred stock was converted into a warrant to purchase 244,444 shares of common stock. The condensed consolidated financial statements as of September 30, 2019, including share and per share amounts, do not give effect to the IPO, the conversion of the convertible preferred stock into common stock, or the conversion of a preferred stock warrant into a warrant to purchase common stock and related reclassification into permanent equity, as the IPO and such conversions and reclassification into permanent equity were completed subsequent to September 30, 2019. Need for Additional Capital The Company has incurred net losses since inception and expects such losses to continue over the next several years. At September 30, 2019, the Company had an accumulated deficit of $304.7 million. Management expects to incur additional losses in the future to conduct research and development and recognizes the need to raise additional capital to fully implement its business plan. Prior to completing its IPO in October 2019, the Company financed its operations primarily through the sale and issuance of convertible preferred stock. The Company had $320.2 million of cash, cash equivalents and short-term investments at September 30, 2019. Based on the Company’s business plans, management believes that its cash, cash equivalents and short-term investments as of September 30, 2019, together with the proceeds received from the IPO, will be sufficient to meet its obligations for at least the next 12 months from the issuance date of these condensed consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policie	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policie	2. Basis of Presentation The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. The condensed consolidated financial statements include the accounts of Vir and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated upon consolidation. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s financial information. The condensed consolidated results of operations for the nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. Certain information and footnote disclosures typically included in the Company’s annual consolidated financial statements have been condensed or omitted. As such, t hese interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2018 included in the prospectus dated October 10, 2019 that forms a part of the Company’s Registration Statement on Form S-1 (File No. 333-233604), as filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933 , as amended (the “Securities Act”) , on October 1 1 , 2019 (the “Prospectus”) . Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expense during the reporting periods. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates . Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents and short-term investments. Cash and cash equivalents are deposited in checking and sweep accounts at a financial institution. Such deposits may, at times, exceed federally insured limits. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and short-term investments and issuers of the short-term investments to the extent recorded on the condensed consolidated balance sheets. As of September 30, 2019, the Company has no off-balance sheet concentrations of credit risk. Investments Investments include available-for-sale securities and are carried at estimated fair value. The Company’s valuations of marketable securities are generally derived from independent pricing services based on quoted prices in active markets for similar securities at period end. Generally, investments with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the consolidated balance sheet date are considered short-term investments. Unrealized gains and losses deemed temporary in nature are reported as a component of accumulated comprehensive income (loss). The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in interest income, on the condensed consolidated statements of operations. The Company’s Swiss subsidiary holds short-term structured deposits which include a feature that provides for the instrument to be settled in U.S. dollars or Swiss Francs (CHF) depending on the strike level set at the onset of the instrument compared to the U.S. dollars to CHF exchange rate at the settlement date. The Company has elected to account for these instruments using the fair value option with gains and losses recognized in earnings. Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and filing fees relating to an initial public offering, are capitalized. The Company has incurred $5.6 million in deferred offering costs relating to its IPO as of September 30, 2019. The deferred offering costs were offset against offering proceeds upon the completion of the IPO in October 2019. There were no deferred offering costs capitalized as of December 31, 2018. Convertible Preferred Stock Warrant Liability A freestanding warrant to purchase shares of Series A-1 convertible preferred stock at a future date was determined to be a freestanding instrument that was accounted for as a liability. At initial recognition, the Company recorded the convertible preferred stock warrant liability on the consolidated balance sheet at its estimated fair value. The warrant liability was subject to remeasurement at each reporting period, with changes in estimated fair value recognized as a component of other income (expense), net until the exercise of the convertible preferred stock warrant or conversion of such warrant into a warrant to purchase shares of common stock. Upon the completion of the IPO in October 2019, the warrant automatically converted into a warrant to purchase shares of common stock. Recent Accounting Pronouncements Not Yet Adopted In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-01, Financial Instrument—Overall (Subtopic 825-10) (“ASU 2016-01”), which requires entities to measure equity instruments at fair value and recognize any changes in fair value within the statement of operations. ASU 2016-01 is effective for the Company for the annual period beginning January 1, 2019, and the interim period beginning January 1, 2020. The Company is currently evaluating the impact of adopting ASU 2016-01 on the consolidated financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (“Topic 842”). Topic 842 requires lessees to recognize all leases, including operating leases, on the balance sheet as a right-of-use asset and lease liability, unless the lease is a short-term lease. In July 2018, the FASB issued supplemental adoption guidance and clarification to Topic 842 within ASU 2018-10 Codification Improvements to Topic 842, Leases and ASU 2018-11, Targeted Improvements—Leases (Topic 842). This update provides an alternative transition method that allows entities to elect to apply the standard retrospectively as of the beginning of the latest period presented versus retrospectively as of the beginning of the earliest period presented. Topic 842 is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020, with early adoption permitted. The Company currently plans to adopt the standard on January 1, 2020 and is currently evaluating the impact of adopting Topic 842 on its consolidated financial statements and disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost, which includes the Company’s financial instruments. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss methodology, which will result in more timely recognition of credit losses. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments (“ASU 2019-04”). ASU 2019-04 modified the accounting for available-for-sale debt securities, which must be individually assessed for credit losses when fair value is less than the amortized cost basis. In October 2019, the FASB affirmed a proposed ASU deferring the effective date of ASU 2016-13 for all entities except public companies that are not smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. This proposed ASU has not been finalized as of the date of this report. When finalized, the Company currently plans to adopt ASU 2016-13 effective January 1, 2023. The Company has not yet evaluated the impact of adopting this standard on the consolidated financial statements and disclosures. In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other: Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which simplifies the current requirements for testing goodwill for impairment by eliminating the second step of the two-step impairment test to measure the amount of an impairment loss. ASU 2017-04 is effective for the Company’s interim and annual reporting periods beginning after December 31, 2021. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2017-04 will have on its consolidated financial statements and related disclosures. The Company currently plans to adopt ASU 2017-04 on January 1, 2020 and does not expect the adoption of ASU 2017-04 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”). ASU 2018-14 added, removed and clarified disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 is effective for the Company for fiscal years ending after December 15, 2021. Early adoption is permitted for all entities. The Company currently plans to adopt ASU 2018-14 in fiscal 2022 and is still evaluating the effect that ASU 2018-14 may have on its notes to consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. The Company determines the fair value of financial and non-financial assets and liabilities using the fair value hierarchy, which establishes three levels of inputs that may be used to measure fair value, as follows: • Level 1: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level 2: Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3: Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The carrying amounts of the Company’s financial instruments, including accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Level 3 liabilities consist of contingent consideration and convertible preferred stock warrant liability. The estimated fair value of the contingent consideration was determined by calculating the probability-weighted milestone payments based on the assessment of the likelihood and estimated timing that certain milestones would be achieved. The fair value of the contingent consideration was estimated using discount rates between 14.6% to 17.7% as of September 30, 2019 and 16.8% to 20.3% as of December 31, 2018. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. The increase in the estimated fair value of contingent consideration is primarily due to the decrease in the derived discount rate. See Note 4 — The convertible preferred stock warrant liability is valued using the Black-Scholes option pricing model. The assumptions used to calculate the convertible preferred stock warrant liability are as follows: September 30, 2019 December 31, 2018 Exercise price $ 4.50 $ 4.50 Expected term 7.0 7.7 Expected stock price volatility 88.8 % 83.5 % Risk-free interest rate 1.6 % 2.6 % Expected dividend yield — — The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy: September 30, 2019 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value (in thousands) Assets: Money market funds (1) Level 1 $ 97,892 $ — $ — $ 97,892 U.S. government treasuries Level 2 226,354 158 — 226,512 Bank time deposits Level 2 4,000 — — 4,000 Total financial assets $ 328,246 $ 158 $ — $ 328,404 Liabilities: Convertible preferred stock warrant liability Level 3 $ 4,425 $ — $ — $ 4,425 Contingent consideration Level 3 10,069 — — 10,069 Total financial liabilities $ 14,494 $ — $ — $ 14,494 (1) Includes $11.7 million of restricted cash equivalents. December 31, 2018 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value (in thousands) Assets: Money market funds (1) Level 1 $ 43,600 $ — $ — $ 43,600 Structured deposits Level 2 1,000 — — 1,000 U.S. government treasuries Level 2 49,859 — (14 ) 49,845 Total financial assets $ 94,459 $ — $ (14 ) $ 94,445 Liabilities: Convertible preferred stock warrant liability Level 3 $ 1,024 $ — $ — $ 1,024 Contingent consideration Level 3 9,250 — — 9,250 Total financial liabilities $ 10,274 $ — $ — $ 10,274 (1) Includes $11.8 million of restricted cash equivalents. As of September 30, 2019, all of the Company’s short-term investments were in an unrealized gain position. Total unrealized gains of $0.2 million were recorded in accumulated other comprehensive income (loss) at September 30, 2019. No securities have contractual maturities of longer than one year. There were no transfers between Levels 1, 2, or 3 for any of the periods presented. The following table sets forth the changes in the estimated fair value of the Company’s Level 3 financial liabilities (in thousands): Contingent Consideration Warrant Liability Total Balance at December 31, 2018 $ 9,250 $ 1,024 $ 10,274 Changes in fair value 819 3,401 4,220 Balance at September 30, 2019 $ 10,069 $ 4,425 $ 14,494

Acquisitions

Acquisitions	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Acquisitions	4. Acquisition of TomegaVax In September 2016, the Company entered into an agreement and plan of merger (“TomegaVax Merger Agreement”) to acquire all of the equity interests of TomegaVax, Inc. (“TomegaVax”). The primary asset purchased in the acquisition was an in-process cytomegalovirus (“CMV”) vector-based vaccine platform for use in hepatitis B virus (“HBV”), human immunodeficiency virus (“HIV”), and tuberculosis (“TB”). The acquisition was accounted for as an asset purchase and the Company recorded the entire purchase price of $5.2 million in research and development expenses in 2016. In connection with the entry into the TomegaVax Merger Agreement, the Company also entered into a letter agreement with TomegaVax (the “TomegaVax Letter Agreement”), which provides for certain payments to TomegaVax’s former stockholders prior to September 2024, in each case so long as the Company is continuing to pursue the development of the TomegaVax technology. Under the terms of the TomegaVax Letter Agreement, the Company will be required to pay to the former stockholders of TomegaVax milestone payments of up to an aggregate of $30.0 million if the per share price of the Company’s publicly traded common stock, or implied price per share of the Company’s Series A-1 convertible preferred stock (or common stock upon conversion) upon a certain asset sale, merger or stock sale, is at least $45 (as adjusted in the case of any stock dividend, stock split or other similar recapitalization), with the amount of such payments determined by the share price and the stage of the Company’s clinical development at the time of the relevant event triggering the payment. The share price of the Company’s publicly traded common stock will be determined using the average of the daily volume-weighted average trading price of the Company’s common stock for each trading day during a consecutive 90-day period. The foregoing payments are payable (i) during any date after the completion of an initial public offering by the Company or any successor or affiliate controlling the TomegaVax technology, provided that no payment will be due before the first anniversary of the initial public offering, (ii) upon the sale of all assets related to the TomegaVax technology or (iii) upon a merger or stock sale of the Company or any successor or affiliate controlling the TomegaVax technology, in each case subject to certain conditions with respect to the timing of the payments. The payments under the TomegaVax Letter Agreement can be made in cash or shares of the Company’s common stock, at the discretion of the Company’s board of directors. None of the milestones have been achieved as of September 30, 2019, therefore no amounts were recognized relating to the contingent consideration during the nine months ended September 30, 2019. Acquisition of Humabs In August 2017, the Company acquired all of the outstanding equity of Humabs Biomed SA (“ The acquired developed technologies that have associated patents issued are classified as finite-lived intangible assets and are amortized on a straight-lined basis over their estimated remaining useful lives, generally between seven to 12 years. The Company also acquired indefinite-lived intangible asset consisting of in-process research and development. These assets will not be amortized until regulatory approval is obtained in a major market. At that time, the Company will determine the useful life of the asset and begin amortization. If the associated research and development effort is abandoned, the related in-process research and development assets will be written-off and an impairment charge recorded. As of September 30, 2019, there have been no such impairments. The estimated fair value of the intangible assets was determined using the replacement cost method. The excess of the purchase price over the estimated fair value of the net assets acquired was recorded as goodwill. None of the goodwill is expected to be deductible for income tax purposes. As of September 30, 2019, no goodwill impairment was identified. Acquisition of Agenovir In January 2018, the Company entered into an agreement and plan of merger (the “Agenovir Merger Agreement”) with Agenovir Corporation (“Agenovir”), pursuant to which the Company purchased all equity interests of Agenovir. The primary assets purchased in the acquisition were in-process research and development programs in human papillomavirus (“HPV”) and HBV using CRISPR/Cas9. The Company concluded that the assets acquired and liabilities assumed did not meet the definition of a business as a limited number of inputs were acquired but no substantive processes were acquired. As such, the acquisition was accounted for as an asset purchase. As purchase consideration, the Company agreed to pay cash of $11.5 million and issued an aggregate of 555,537 shares of Series A-2 convertible preferred stock, valued at $1.8 million on the transaction date, to the former Agenovir stockholders. The Company also assumed certain liabilities of $1.3 million. The estimated fair value of the Company’s Series A-2 convertible preferred stock was $3.15 per share as of the date of the transaction and was determined by management with the assistance of a third-party valuation specialist. The Company retained $2.0 million of the cash consideration as holdback to satisfy claims for indemnification, of which, $1.8 million was paid to Agenovir in April 2019. In addition to the equity, the Company incurred transaction costs of $0.7 million. The Company allocated the purchase price of $15.3 million between property and equipment of $0.8 million and in-process research and development of $14.5 million, which was expensed as research and development expenses in the accompanying condensed consolidated statement of operations for the nine months ended September 30, 2018. During a specified period following the closing of the Agenovir acquisition, the Company will be required to pay Agenovir’s former stockholders up to $45.0 million in the aggregate for the achievement of specified development and regulatory milestones for the first HBV product, and if the Company elects to progress the HPV program, the Company will owe up to $45.0 million in the aggregate for the achievement of development and regulatory milestones for the first HPV product. In addition, during a specified period following the closing of the Agenovir acquisition, if the Company successfully commercializes one or more products arising from the HBV program or the HPV program, the Company will owe milestone payments for the achievement of specified levels of worldwide annual net sales of up to $90.0 million for products arising from each program, or up to $180.0 million in the aggregate, if the Company were to commercialize products from both the HBV program and the HPV program. None of the milestones have been achieved as of September 30, 2019, therefore no amounts were recognized relating to the contingent consideration. Acquisition of Statera In February 2018, the Company entered into an agreement and plan of reorganization with Statera Health, LLC (“Statera”), pursuant to which the Company acquired all equity interests of Statera. The Company paid $0.9 million in cash and issued an aggregate of 188,333 shares of Series A-2 convertible preferred stock, valued at $0.6 million on the transaction date, to the former Statera stockholders as purchase consideration. The estimated fair value of the Company’s Series A-2 convertible preferred stock was $3.15 per share as of the date of the transaction and was determined by management with the assistance of a third-party valuation specialist. The transaction was accounted for as an asset acquisition. The Company incurred transaction costs of $0.2 million. The primary asset purchased was a cloud-based predictive analytics platform that translates clinical data into casual hypotheses of disease pathophysiology. The cloud-based predictive analytics platform was accounted for as developed technology and is classified as finite-lived intangible assets and is being amortized on a straight-lined basis over an estimated useful life of three years.

Grant, License and Collaboratio

Grant, License and Collaboration Agreements	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Grant, License and Collaboration Agreements	5 . Grant, License and Collaboration Agreements The Company is a party to various grant and customer contract agreements. Descriptions of the material agreements are included below. Bill & Melinda Gates Foundation Grants Campylo/EPEC/EAEC Grant As part of the Company’s acquisition of Humabs in August 2017, the Company acquired a grant agreement with the Bill & Melinda Gates Foundation pursuant to which it was awarded a grant totaling up to $4.7 million (the “2017 Grant”). The 2017 Grant supported the Company’s discovery, characterization and selection of human monoclonal antibodies with pre-clinical efficacy against three enteric pathogens responsible for life-threatening diarrhea in neonates. The 2017 Grant expired on May 31, 2019. Payments received in advance that were related to future research activities were deferred and recognized as revenue when the donor-imposed conditions were met, which was as the research and development activities were performed. The Company recognized grant revenue of nil and $0.8 million for the three months ended September 30, 2019 and 2018, and $0.9 million and $1.5 million for the nine months ended September 30, 2019 and 2018, respectively. Human Immunodeficiency Virus (“HIV”) Grant On January 26, 2018, the Company entered into a grant agreement with the Bill & Melinda Gates Foundation pursuant to which it was awarded a grant totaling up to $12.2 million for its HIV program (the “HIV Grant”). The HIV Grant will remain in effect until June 30, 2020, unless earlier terminated by the Bill & Melinda Gates Foundation for the Company’s breach, failure to progress the funded project, in the event of the Company’s change of control, change in the Company’s tax status, or significant changes in the Company’s leadership that the Bill & Melinda Gates Foundation reasonably believes may threaten the success of the project. Payments received in advance that are related to future research activities are deferred and recognized as revenue when the donor-imposed conditions are met, which is as the research and development activities are performed. The Company recognized grant revenue of $0.5 million and $0.8 million for the three months ended September 30, 2019 and 2018, respectively, and $3.4 million and $2.8 million for the nine months ended September 30, 2019 and 2018, respectively. Tuberculosis (“TB”) Grant On March 16, 2018, the Company entered into a grant agreement with the Bill & Melinda Gates Foundation pursuant to which it was awarded a grant totaling up to $14.9 million for its TB program (the “TB Grant”). The TB Grant will remain in effect until June 30, 2020, unless earlier terminated by the Bill & Melinda Gates Foundation for the Company’s breach, failure to progress the funded project, in the event of the Company’s change of control, change in the Company’s tax status, or significant changes in the Company’s leadership that the Bill & Melinda Gates Foundation reasonably believes may threaten the success of the project. Payments received in advance that are related to future research activities are deferred and recognized as revenue when the donor-imposed conditions are met, which is as the research and development activities are performed. The Company recognized grant revenue of $0.4 million and $1.0 million for the three months ended September 30, 2019 and 2018, respectively, and $1.8 million and $1.5 million for the nine months ended September 30, 2019 and 2018, respectively. National Institutes of Health As part of the Company’s acquisition of TomegaVax in September 2016, the Company acquired grant agreements related to TomegaVax’s research effort in infectious diseases and cancer that entitled them to several awards under the Small Business Innovation Research Program from the National Institutes of Health (“NIH”). Through September 30, 2019, the Company has acquired or been awarded grants from NIH totaling $5.1 million. These grants are cost plus fixed fee agreements in which the Company is reimbursed for its direct and indirect costs. Only costs that are allowable under certain government regulations and NIH’s supplemental policy and procedure manual may be claimed for reimbursement, subject to government audit. The Company recognized grant revenue of $0.2 million for each of the three months ended September 30, 2019 and 2018, and $0.7 million and $0.9 million for the nine months ended September 30, 2019 and 2018, respectively. Brii Biosciences In May 2018, the Company entered into an option and license agreement (the “Brii Agreement”) with Brii Biosciences Limited (previously named BiiG Therapeutics Limited) (“Brii Bio Parent”) and Brii Biosciences Offshore Limited (“Brii Bio”), pursuant to which the Company granted to Brii Bio, with respect to up to four of the Company’s programs, an exclusive option to obtain exclusive rights to develop and commercialize compounds and products arising from such programs in China, Taiwan, Hong Kong and Macau (collectively, the “China Territory”) for the treatment, palliation, diagnosis, prevention or cure of acute and chronic diseases of infectious pathogen origin or hosted by pathogen infection (the “Field of Use”). The Company’s HBV small interfering ribonucleic acid (“siRNA”) program being developed under the Alnylam Agreement (described below) is included within the Brii Agreement as a program for which Brii Bio may exercise one of its options. In partial consideration for the options granted by the Company to Brii Bio, Brii Bio Parent and Brii Bio granted the Company, with respect to up to four of Brii Bio Parent’s or Brii Bio’s programs, an exclusive option to be granted exclusive rights to develop and commercialize compounds and products arising from such Brii Bio programs in the United States for the Field of Use. The number of options that the Company may exercise for a Brii Bio program is limited to the corresponding number of options that Brii Bio exercises for a Vir program. As of September 30, 2019, no license option had been exercised. As partial consideration for the Company’s entry into the Brii Agreement, upon closing of Brii Bio Parent’s Series A preferred stock financing, the Company received ordinary shares equal to 9.9% of the outstanding shares in Brii Bio Parent. As a result of Brii Bio’s right to exercise one of its options for the Company’s HBV siRNA program, under the terms of the Alnylam Agreement, as amended by a letter agreement with Alnylam, the Company will transfer to Alnylam a specified percentage of such equity consideration allocable to such program. The Company also received an option to purchase additional ordinary shares of Brii Bio Parent at a purchase price of $0.0001 per share in connection with additional Series A preferred stock issuances by Brii Bio Parent and an option to acquire shares of Brii Bio Parent’s Series B preferred stock upon the occurrence of a Series B financing at the same purchase price paid by the other Series B investors. With respect to programs for which Brii Bio exercises its options, Brii Bio will be required to pay the Company an option exercise fee for each such Vir program ranging from the mid-single-digit millions up to $20.0 million, determined based on the commercial potential of the licensed program. Brii Bio will also be required to pay regulatory milestone payments on a licensed product-by-licensed product basis ranging from the mid-single-digit millions up to $30.0 million, also determined based on the commercial potential of such program. Following commercialization, Brii Bio will be required to make sales milestone payments based on certain specified levels of aggregate annual net sales of products arising from each licensed program in the China Territory, up to an aggregate of $175.0 million per licensed program. Brii Bio also will pay royalties to the Company that range from the mid-teens to the high-twenties, as described below. Upon exercise of each option for a Brii Bio program, the Company will be required to pay to Brii Bio an option exercise fee ranging from the low tens of millions to up to $50.0 million, determined based on the commercial potential of the licensed program. The Company will be required to make regulatory milestone payments to Brii Bio on a licensed product-by-licensed product basis ranging from the low tens of millions up to $100.0 million, also determined based on the commercial potential of such program. The Company will also be required to make sales milestone payments based on certain specified levels of aggregate annual net sales of products in the United States arising from each licensed program, up to an aggregate of $175.0 million per licensed program. In addition, the Company is obligated under the Brii Agreement to pay Brii Bio tiered royalties based on net sales of products arising from the licensed programs in the United States, and Brii Bio is obligated to pay the Company tiered royalties based on net sales of products arising from the licensed programs in the China Territory. The rates of royalties payable by the Company to Brii Bio, and by Brii Bio to the Company, on net sales range from mid-teens to high-twenties. Each party’s obligations to pay royalties expires, on a product-by-product and territory-by-territory basis, on the latest of 10 years after the first commercial sale of such licensed product in the United States or China Territory, as applicable; the expiration or abandonment of licensed patent rights that cover such product in the United States or China Territory, as applicable; and the expiration of regulatory exclusivity in the United States or the China Territory, as applicable. Royalty rates are subject to specified reductions and offsets. The Brii Agreement will remain in force until expiration of all options or, if any option is exercised, expiration of all royalty payment obligations for all licensed products within such licensed program, unless terminated in its entirety or on a program-by-program basis by either party. Each party may terminate for convenience all rights and obligations with respect to any program for which it has an option, with 30 days’ written notice (if the terminating party has not exercised an option for such program) or 180 days’ notice (following the exercise of an option for such program). The Brii Agreement may also be terminated by either party for insolvency of the other party, and either party may terminate the Brii Agreement in its entirety or on a program-by-program basis for the other party’s uncured material breach on 60 days’ written notice (or 30 days’ notice following failure to make payment). The Company has determined that Brii Bio Parent and its wholly owned subsidiary Brii Bio are variable interest entities due to their reliance on future financing and having insufficient equity at risk. However, the Company does not have the power to direct activities which most significantly impact the economic success of these entities and is not considered the primary beneficiary of these entities. Therefore, the Company does not consolidate Brii Bio Parent or Brii Bio. The Company also determined that it does not exercise significant influence over Brii Bio Parent or Brii Bio. The investment in Brii Bio Parent was recorded at its initial estimated fair value of $6.6 million within other assets on the consolidated balance sheet and is subsequently accounted for under the cost method. The Company also recorded a contract liability of $6.6 million within deferred revenue, noncurrent; which represents the four options that the Company granted to Brii Bio. Revenue will be recognized when Brii Bio exercises its options or the options expire. As of September 30, 2019 and December 31, 2018, the carrying value of the investment in Brii Bio is $6.6 million, which is included in other assets on the consolidated balance sheets. The Company’s maximum exposure to loss under the Brii Agreement is represented by options to acquire licenses to develop and commercialize potential products and future milestone payments. The ultimate expense that the Company incurs under the Brii Agreement cannot be quantified at this time as the amount will vary based on the timing and outcome of research activities. Alnylam In October 2017, the Company entered into a collaboration and license agreement (the “Alnylam Agreement”) with Alnylam Pharmaceuticals, Inc. (“Alnylam”) for the development of siRNA products for the treatment of HBV and following the exercise of certain program options, the development and commercialization of siRNA therapeutic products directed to up to four other infectious disease targets selected by the Company. The technology licensed under the Alnylam Agreement forms the basis of the Company’s siRNA technology platform. Pursuant to the Alnylam Agreement, the Company obtained a worldwide, exclusive license to develop, manufacture and commercialize the HBV siRNA product candidates, including VIR-2218, for all uses and purposes other than agricultural, horticultural, forestry, aquaculture and other residential applications, such excluded fields, the Excluded Fields. In addition, Alnylam granted us an exclusive option, for each of the infectious disease siRNA programs directed to the Company’s selected targets, to obtain a worldwide, exclusive license to develop, manufacture and commercialize siRNA products directed to the target of each such program for all uses and purposes other than the Excluded Fields. On a product-by-product basis for each product arising from the HBV and, following the Company’s option exercise, the infectious disease programs, Alnylam has an exclusive option, exercisable during a specified period prior to the initiation of a Phase 3 clinical trial for each such product, to negotiate and enter into a profit-sharing agreement for such product. The Company and Alnylam are jointly responsible for funding the initial research and development activities for VIR-2218 through completion of proof of concept studies. Prior to the exercise of the Company’s option for each siRNA program directed to one of the Company’s selected infectious disease targets, Alnylam is responsible for conducting all development activities, at the Company’s expense, in accordance with an agreed upon development plan. Following the Company’s exercise of an option for a program and payment of the program option exercise fee and any outstanding program costs due to Alnylam, the Company is solely responsible, at the Company’s expense (subject to Alnylam’s exercise of a profit-sharing option), for conducting all development, manufacture and commercialization activities for products arising from each such program. If Alnylam exercises a profit-sharing option for a product, the Company will negotiate the terms of such profit-sharing agreement, which will include sharing equally with Alnylam all subsequent costs associated with the development of such product, as well as the profits and losses in connection with such product, subject to reimbursement by Alnylam of a portion of specified development costs in certain circumstances. Pursuant to the Alnylam Agreement, the Company paid Alnylam an upfront fee of $10.0 million and issued to Alnylam 1,111,111 shares of the Company’s common stock. Both the upfront fee and the estimated fair value of the common stock were recognized as research and development expenses in 2017. Additionally, the receipt of consideration from Brii Bio as discussed above triggered a requirement under the Alnylam Agreement to transfer a portion of the consideration, consisting of equity in Brii Bio, to Alnylam. Accordingly, the Company recognized a liability of $0.8 million as of December 31, 2018, and a corresponding charge to research and development expenses. The liability of $0.8 million remained outstanding as of September 30, 2019. Upon the achievement of a certain development milestone, the Company will also issue shares of the Company’s common stock equal to the lesser of (i) 1,111,111 shares or (ii) a certain number of shares based on the Company’s stock price at the time such milestone is achieved. The Company will be required to pay Alnylam up to $190.0 million in the aggregate for the achievement of specified development and regulatory milestones by the first siRNA product directed to HBV, and up to $115.0 million for the achievement of specified development and regulatory milestones by the first product directed to the target of each infectious disease siRNA program for which the Company exercised its option. Following commercialization, the Company will be required to pay to Alnylam up to $250.0 million in the aggregate for the achievement of specified levels of net sales by siRNA products directed to HBV and up to $100.0 million for the achievement of specified levels of net sales by products directed to the target of each infectious disease siRNA program for which the Company exercised its option. The Company may also be required to pay Alnylam tiered royalties at percentages ranging from the low double-digits to mid-teens on annual net sales of HBV products, and tiered royalties at percentages ranging from the high single-digits to the sub-teen double-digits on annual net sales of licensed infectious disease products, in each case subject to specified reductions and offsets. The royalties are payable on a product-by-product and country-by-country basis until the later of the expiration of all valid claims of specified patents covering such product in such country and 10 years after the first commercial sale of such product in such country. No such liabilities have been recorded as of September 30, 2019. The term of the Alnylam Agreement will continue, on a product-by-product and country-by-country basis, until expiration of all royalty payment obligations under the Alnylam Agreement. If the Company does not exercise its option for an infectious disease program directed to one of its selected targets, the Alnylam Agreement will expire upon the expiration of the applicable option period with respect to such program. However, if Alnylam exercises its profit-sharing option for any product, the term of the Alnylam Agreement will continue until the expiration of the profit-sharing arrangement for such product. The Company may terminate the Alnylam Agreement on a program-by-program basis or in its entirety for any reason on 90 days’ written notice. Either party may terminate the agreement for cause for the other party’s uncured material breach on 60 days’ written notice (or 30 days’ notice for payment breach), or if the other party challenges the validity or enforceability of any patent licensed to it under the Alnylam Agreement on 30 days’ notice. The Company incurred $7.5 million and $1.6 million of expenses under the Alnylam Agreement during the three months ended September 30, 2019 and 2018, respectively, and $10.7 million and $7.1 million during the nine months ended September 30, 2019 and 2018, respectively. Visterra In August 2017, the Company entered into a collaboration, license and option agreement (the “Visterra Agreement”) with Visterra, Inc. (“Visterra”) to license Visterra’s proprietary technology and to research, develop, and commercialize certain product candidates. Under the Visterra Agreement, the Company paid an upfront fee of $25.0 million, which was recognized as research and development expenses in 2017. The Company incurred $0.3 million and $2.6 million for the research and development activities under the Visterra Agreement during the three and nine months ended September 30, 2018. November 2019 Rockefeller University In July 2018, the Company entered into an exclusive license agreement with The Rockefeller University (“Rockefeller”), which was amended in May 2019 (the “Rockefeller Agreement”). Pursuant to the Rockefeller Agreement, Rockefeller granted the Company a worldwide exclusive license under certain patent rights, and a worldwide non-exclusive license under certain materials and know-how covering certain antibody variants relating to a specified mutation leading to enhanced antibody function and utility, to develop, manufacture and commercialize infectious disease products covered by the licensed patents, or that involve the use or incorporation of the licensed materials and know-how, in each case for all uses and purposes for infectious diseases. The Company uses technology licensed under the Rockefeller Agreement in the Company’s antibody platform and in the Company’s product candidate VIR-3434. The Company paid Rockefeller an upfront fee of $0.3 million for entry into the Rockefeller Agreement, and is required to pay annual license maintenance fees of $1.0 million, which will be creditable against royalties following commercialization. In addition, for achievement of specified development and regulatory milestone events, the Company will be required to pay up to $8.5 million with respect to the first infectious disease product for the HIV indication, up to $7.0 million with respect to each of the first four other infectious disease products with specified projected peak worldwide annual net sales, and up to $3.6 million with respect to any other infectious disease product. Following regulatory approval, the Company will be required to pay commercial success milestones of up to $40.0 million in the aggregate for the achievement of specified aggregate worldwide annual net sales of the first infectious disease product for the HIV indication and the first four infectious disease products with specified projected peak worldwide annual net sales. The Company will also be required to pay to Rockefeller a royalty at a low single-digit percentage rate on net sales of licensed products, subject to certain adjustments. The Company’s obligation to pay royalties to Rockefeller will terminate, on a product-by-product and jurisdiction-by-jurisdiction basis, upon the latest of the expiration of the last valid claim of a licensed patent in such jurisdiction, the expiration of all regulatory exclusivity in such jurisdiction or 12 years following the first commercial sale of the applicable licensed product in such jurisdiction. The Company recognized $1.0 million of annual license maintenance fee as research and development expense during the nine months ended September 30, 2019. The Rockefeller Agreement will remain in force, absent earlier termination, until the expiration of all of the Company’s obligations to pay royalties to Rockefeller in all jurisdictions. The Company has the right to terminate the Rockefeller Agreement in its entirety, or in part, for any reason on 60 days’ written notice to Rockefeller. Rockefeller may terminate the Rockefeller Agreement on 90 days’ written notice for the Company’s uncured material breach, or if the Company challenges the validity or enforceability of any of the licensed patents, or immediately in the event of the Company’s insolvency. Rockefeller may also terminate the Rockefeller Agreement if the Company ceases to carry on business with respect to the rights granted to the Company under the agreement. MedImmune In September 2018, the Company entered into a license agreement (“2018 MedImmune Agreement”) with MedImmune, LLC (“MedImmune”), pursuant to which the Company obtained a worldwide, exclusive license to develop and commercialize half-life extended versions of two specified antibodies under development by MedImmune that target influenza A and influenza B, respectively, for all uses in humans and animals. The Company is developing VIR-2482 using technology licensed under the 2018 MedImmune Agreement. In consideration for the grant of the licenses under the 2018 MedImmune Agreement, the Company made an upfront payment to MedImmune of $10.0 million. The upfront fee was recognized as research and development expenses in the third quarter of 2018. The Company will be obligated to make development, regulatory, and commercial milestone payments of up to $343.3 million in the aggregate relating to influenza A and influenza B products. MedImmune will also be entitled to receive tiered royalties based on net sales of products containing half-life extended versions of antibodies directed to influenza A and/or influenza B at percentages ranging from the mid-single-digits to sub-teen double-digits. The 2018 MedImmune Agreement will remain in force until the expiration on a country-by-country and product-by-product basis of all of the Company’s obligations to pay royalties to MedImmune. The Company may terminate the 2018 MedImmune Agreement in its entirety or on a product-by-product basis, for convenience, upon 120 days’ notice. Either party may terminate the 2018 MedImmune Agreement for cause for the other party’s uncured material breach on 60 days’ notice or immediately in the event of bankruptcy of the other party. Additionally, MedImmune may terminate the 2018 MedImmune Agreement for cause on 30 days’ written notice if the Company challenges the validity or enforceability of the patents to which the Company has obtained a license under the 2018 MedImmune Agreement. In August 2019, the Company achieved one of the specified development milestones relating to influenza A pursuant to the 2018 MedImmune Agreement. As such, the Company paid $5.0 million related to this milestone event in September 2019. The milestone payment was expensed to research and development in the three and nine months ended September 30, 2019. Xencor In August 2019, the Company entered into a patent license agreement (the “Xencor Agreement”) with Xencor, Inc., (“Xencor”). Pursuant to the Xencor Agreement, the Company obtained a non-exclusive, sublicensable (only to its affiliates and subcontractors) license to incorporate Xencor’s half-life extension Fc region-related technologies into, and to evaluate, antibodies that target influenza A and HBV, and a worldwide, non-exclusive, sublicensable license to develop and commercialize products containing such antibodies incorporating such technologies for all uses, including the treatment, palliation, diagnosis and prevention of human or animal diseases, disorders or conditions. The Company is obligated to use commercially reasonable efforts to develop and commercialize an antibody product that incorporates Xencor’s half-life extension Fc-related technologies, for each of the influenza A and HBV research programs. These technologies are used in the Company’s VIR-2482 and VIR-3434 product candidates. In consideration for the grant of the license, the Company paid Xencor an upfront fee. The upfront fee was recognized as research and development expenses in the third quarter of 2019. For each of the influenza A and HBV research programs, the Company will be required to pay Xencor development and regulatory milestone payments of up to $17.8 million in the aggregate, and commercial sales milestone payments of up to $60.0 million in the aggregate, for a total of up to $77.8 million in aggregate milestones for each program and $155.5 million in aggregate milestones for both programs. On a product-by-product basis, the Company will also be obligated to pay tiered royalties based on net sales of licensed products in the low single-digits. The royalties are payable, on a product-by-product and country-by-country basis, until the expiration of the last to expire valid claim in the licensed patents covering such product in such country. The Xencor Agreement will remain in force, on a product-by-product and country-by-country basis, until expiration of all royalty payment obligations under the Xencor Agreement. The Company may terminate the Xencor Agreement in its entirety, or on a target-by-target basis, for convenience upon 60 days’ written notice. Either party may terminate the Xencor Agreement for the other party’s uncured material breach upon 60 days’ written notice (or 30 days in the case of non-payment) or in the event of bankruptcy of the other party immediately upon written notice. Xencor may terminate the Xencor Agreement immediately upon written notice if the Company challenges, or upon 30 days’ written notice if any of the Company’s sublicensees challenge, the validity or enforceability of any patent licensed to the Company under the Xencor Agreement. In August 2019, the Company achieved one of the specified development milestones pursuant to the Xencor Agreement. As such, the Company paid $0.8 million related to the upfront fee and this milestone event in September 2019. The milestone payment was expensed to research and development in the three and nine months ended September 30, 2019.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	6 . Property and Equipment, net Property and equipment, net consists of the following: September 30, 2019 December 31, 2018 (in thousands) Lab equipment $ 10,559 $ 7,538 Computer equipment 548 518 Furniture and fixtures 1,330 943 Leasehold improvements 7,162 3,114 Construction in progress — 1,893 Property and equipment, gross 19,599 14,006 Less accumulated depreciation and amortization (4,151 ) (1,716 ) Total property and equipment, net $ 15,448 $ 12,290 Depreciation and amortization expenses was $0.9 million and $0.4 million for the three months ended September 30, 2019 and 2018, respectively, and $2.4 million and $1.0 million for the nine months ended September 30, 2019 and 2018, respectively. Sale-Leaseback Transaction In August 2019, the Company entered into a lease agreement whereby the Company sold various laboratory instruments, furniture, and other equipment for gross proceeds of $1.2 million to a bank and leased them back for a five-year Accrued Liabilities Accrued liabilities consist of the following: September 30, 2019 December 31, 2018 (in thousands) Payroll and related expenses $ 6,813 $ 6,165 Research and development expenses 11,536 5,016 Restricted stock liability 1,672 — Other professional and consulting expenses 1,199 694 Other accrued expenses 1,733 2,659 Total accrued liabilities $ 22,953 $ 14,534

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7 . Facility Leases The Company has various lease arrangements for office and laboratory space located in California, Oregon and Switzerland with contractual lease periods expiring between 2020 and 2028. In April 2019, the Company executed an amendment to the lease related to the San Francisco facility and in June 2019, the Company executed a noncancelable operating lease for the South San Francisco facility. In addition, the Company entered into a sale-leaseback transaction in August 2019. See further discussion in Note 6—Balance Sheet Components. Rent expense is recognized on a straight-line basis over the terms of the operating leases accordingly and the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. The following are the aggregate non-cancelable future minimum lease payments under operating and financing leases as of September 30, 2019 (in thousands): Year Ending December 31: Amounts 2019 (remaining three months) $ 1,105 2020 4,273 2021 4,053 2022 4,138 2023 and thereafter 8,240 Total $ 21,809 Rent expense for the three months ended September 30, 2019 and 2018 was $1.2 million and $0.9 million, respectively, and for the nine months ended September 30, 2019 and 2018 was $3.2 million and $3.1 million, respectively. Indemnification 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. 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. In addition, the Company has entered into indemnification agreements with its directors and certain officers that may require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. To date, no demands have been made upon the Company to provide indemnification under these agreements, and thus, there are no indemnification claims that the Company is aware of that could have a material effect on the Company’s consolidated balance sheets, consolidated statements of operations, or consolidated statements of cash flows.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	8 . In January 2017, the Company issued a promissory note to an executive officer and a promissory note to a director for an aggregate principal amount of $3.1 million with an interest rate of 1.97% per annum. Principal and interest under these notes were due the earlier of (i) December 31, 2025 or (ii) in an event of default. The entire principal amount was used to purchase 3,624,355 shares of restricted stock. The outstanding balance of these notes was $3.2 million as of December 31, 2018. In August 2019, in accordance with the terms of the notes, the Company received $3.3 million as repayment of the outstanding promissory notes and accrued interest. As the promissory notes were non-recourse in nature, they were accounted for as in-substance stock options. See further discussion in Note 11—Stock-Based Awards. As a result of the Brii Agreement in May 2018, the Company holds a minority equity interest in Brii Bio through its parent company, Brii Bio Parent. Additionally, the Company’s Chief Executive Officer and member of the board of directors as well as another member of the Company’s board of directors serve on Brii Bio Parent’s board of directors. In January 2019, the Company issued 18,202,213 shares of Series B convertible preferred stock to existing Series A-1 preferred stockholders. See further discussion in Note 9—Convertible Preferred Stock.

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	9 . Prior to the IPO, under the Company’s amended and restated certificate of incorporation in effect as of September 30, 2019, the Company was authorized to issue two classes of shares: preferred stock and common stock. The preferred stock was issued in a series. In June 2018, the Amended and Restated Series A-1 and B Purchase Agreement was amended (as amended, the “Amended A&R Series A-1 and B Purchase Agreement”), pursuant to which the Company sold an aggregate of 3,222,220 shares of Series A-1 convertible preferred stock at $4.50 per share for gross proceeds of $14.5 million in three closings (the “Additional Closings”): (i) 2,777,776 shares in two closings in June 2018; and (ii) 444,444 shares in July 2018. Pursuant to the Amended A&R Series A-1 and B Purchase Agreement, after the Additional Closings, the Company was authorized to sell up to 1,111,121 additional shares of Series A-1 convertible preferred stock in one or more additional closings. In January 2019, pursuant to the Amended A&R Series A-1 and B Purchase Agreement, the Company sold an aggregate of 18,202,213 shares of Series B convertible preferred stock at $18.00 per share for gross proceeds of $327.6 million in two closings (the “Series B Closing”). The Company is authorized to sell up to 4,020,009 additional shares of Series B convertible preferred stock in one or more additional closings. At September 30, 2019, convertible preferred stock consisted of the following (in thousands, except share and per share amounts): September 30, 2019 Shares Authorized Shares Issued and Outstanding Issuance Price per Share Carrying Value Liquidation Preference Series A-1 310,350,000 67,611,100 $ 4.50 $ 303,224 $ 322,505 Series A-2 11,100,000 2,299,420 $ 2.57 5,913 10,968 Series B 100,000,000 18,202,213 $ 18.00 327,475 342,094 421,450,000 88,112,733 $ 636,612 $ 675,567 At December 31, 2018, convertible preferred stock consisted of the following (in thousands, except share and per share amounts): December 31, 2018 Shares Authorized Shares Issued and Outstanding Issuance Price per Share Carrying Value Liquidation Preference Series A-1 310,350,000 67,611,100 $ 4.50 $ 303,224 $ 322,100 Series A-2 11,100,000 2,299,420 $ 2.57 5,913 10,958 Series B 100,000,000 — — — — 421,450,000 69,910,520 $ 309,137 $ 333,058 The Company recorded its convertible preferred stock at the issuance price on the dates of issuance, net of issuance costs. Certain purchasers of Series A-1 convertible preferred stock committed to purchase a pre-determined number of shares of Series B convertible preferred stock at a purchase price of $18.00 per share. In the event that any purchaser of Series A-1 convertible preferred stock did not purchase such number of shares of Series B convertible preferred stock it agreed to purchase pursuant to the Amended A&R Series A-1 and B Purchase Agreement, other than as a result of the nonfulfillment of conditions to such purchaser’s obligation to purchase such shares, then (i) each share of Series A-1 convertible preferred stock and Series B convertible preferred stock (collectively, “Senior Preferred Stock”) originally purchased by such purchaser would have automatically converted into 5% of the number of shares of common stock that would otherwise have been issuable upon conversion of such shares if the purchaser had elected to convert the shares to common stock and (ii) with respect to any shares of common stock outstanding at the time of a Series B Closing that were issued to the purchaser upon its conversion election of Senior Preferred Stock, 95% of the shares of common stock issued upon such conversion would have been canceled by the Company for no consideration. No such conversions have taken place because the relevant purchasers of Series A-1 convertible preferred stock had purchased the number of Series B convertible preferred stock as committed pursuant to the Amended A&R Series A-1 and B Purchase Agreement. The convertible preferred stock is an equity instrument with various features, including convertibility and dividends. The Company determined that none of the features required bifurcation from the underlying shares, either because they are clearly and closely related to the underlying shares or because they do not meet the definition of a derivative. The Company did not separately account for the purchase rights of the shares of Series B convertible preferred stock described above as they were not freestanding from the associated shares of Series A-1 convertible preferred stock. The holders of the convertible preferred stock had the following rights and preferences: Dividend Rights The holders of preferred stock were entitled to receive dividends, if and when declared by the Company’s board of directors, at the rate of $0.27 per share per annum for each of Series A-1 convertible preferred stock and Series A-2 convertible preferred stock and $1.08 per share per annum for Series B convertible preferred stock, from and after the date of issuance of such shares. As of September 30, 2019, no such dividends were declared or accrued. Conversion Rights Each share of Series A-1 convertible preferred stock, Series A-2 convertible preferred stock and Series B convertible preferred stock was convertible, at the option of the holder, into one share of common stock, subject to certain adjustments for dilution, if any, resulting from future stock issuances. Each share of Series A-1 convertible preferred stock, Series A-2 convertible preferred stock and Series B convertible preferred stock automatically converted into shares of common stock at the then-effective conversion rate for such share either: (i) upon the closing of a firm-commitment underwritten public offering pursuant to an effective registration statement under the Securities Act, resulting in gross proceeds to the Company of not less than $200.0 million; or (ii) by vote or written consent of the holders of at least 60% of the then outstanding shares of Series A-1 convertible preferred stock and Series B convertible preferred stock. Additionally, in the event that any purchaser of Series A-1 convertible preferred stock did not purchase such number of shares of Series B convertible preferred stock it agreed to purchase pursuant to the Amended A&R Series A-1 and B Purchase Agreement, other than as a result of the nonfulfillment of conditions to such purchaser’s obligation to purchase such shares, then (i) each share of Senior Preferred Stock originally purchased by such purchaser automatically converted into 5% of the number of shares of common stock that would otherwise have been issuable upon conversion of such shares should the purchaser have elected to convert the shares to common stock and (ii) with respect to any shares of common stock outstanding at the time of a Series B Closing that were issued to the purchaser upon its conversion election of Senior Preferred Stock, 95% of the shares of common stock issued upon such conversion would have been canceled by the Company for no consideration. The conversion price for each series of preferred stock was subject to an adjustment in the event of stock split, stock dividend, combination or other similar recapitalization with respect to the common stock. Voting Rights Each holder of outstanding shares of preferred stock had voting rights equal to the whole number of shares of common stock into which such shares could have been converted as of the record date for determining stockholders entitled to vote on such matter. Except as provided by law or by the other provisions of the Company’s amended and restated certificate of incorporation, the holders of the Series A-1 convertible preferred stock, Series A-2 convertible preferred stock and Series B convertible preferred stock voted together with the holders of common stock as a single class. Holders of shares of Series A-1 convertible preferred stock, voting as a separate class, were entitled to elect three directors of the Company prior to the date shares of Series B convertible preferred stock were issued (the “Series B Issuance Date”) and were entitled to elect two directors of the Company after the Series B Issuance Date. The holders of shares of Series A-2 convertible preferred stock, voting as a separate class, were entitled to elect one director of the Company. The holders of shares of Series B convertible preferred stock, voting as a separate class, were entitled to elect one director of the Company. Holders of a majority of the outstanding shares of common stock and preferred stock, voting as a single class on an as-converted basis, were entitled to elect any remaining directors. Liquidation Rights In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or a deemed liquidation event, as further defined in the Company’s amended and restated certificate of incorporation, the holders of shares of Senior Preferred Stock then outstanding were entitled to be paid out of the assets of the Company available for distribution to its stockholders, on a pari passu Redemption The preferred stock was not redeemable at the option of the holder. Classification The Company has classified the convertible preferred stock as temporary equity on the consolidated balance sheets as the shares could have been redeemed upon the occurrence of certain change in control events that are outside the Company’s control, including liquidation, sale or transfer of the Company. The Company has elected not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because it was uncertain whether or when an event would occur that would obligate the Company to pay the liquidation preferences to holders of shares of convertible preferred stock. Subsequent adjustments to the carrying values to the liquidation preferences would have been made only when it became probable that such a liquidation would occur.

Convertible Preferred Stock War

Convertible Preferred Stock Warrant Liability	9 Months Ended
	Sep. 30, 2019
Convertible Preferred Stock Warrant Liability [Abstract]
Convertible Preferred Stock Warrant Liability	1 0 . In September 2016, the Company issued a warrant to purchase an aggregate of 244,444 shares of the Company’s Series A-1 convertible preferred stock with an exercise price of $4.50 per share in connection with the termination of a sponsor research agreement. The warrant was fully vested upon the issuance date and has an expiration date of September 11, 2026. The initial fair value of the warrant was calculated using the Black-Scholes pricing model and the following assumptions: volatility of 99.32%, expected term of 10 years, risk-free interest rate of 1.68%, exercise price of $4.50 and dividend rate of 0%. The fair value of the warrant was determined to be $4.4 million and $1.0 million as of September 30, 2019 and December 31, 2018, respectively.

Stock-Based Awards

Stock-Based Awards	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Awards	1 1 . 2016 Equity Incentive Plan In September 2016, the Company adopted the 2016 Equity Incentive Plan (the “2016 Plan”) for the issuance of incentive stock options (“ISO”), non-qualified stock options (“NSO”), stock appreciation rights (“SARs”), restricted stock and other stock awards, to employees, non-employee directors, and consultants under terms and provisions established by the Company’s board of directors and approved by the stockholders. Awards granted under the 2016 Plan expire no later than ten years from the date of grant. For ISO and NSO, the option price shall not be less than 100% of the estimated fair value on the date of grant. Options granted typically vest over a four-year As of September 30, 2019, there were 1,880,604 shares available for the Company to grant under the 2016 Plan. 2019 Equity Incentive Plan In September 2019, the Company’s board of directors adopted, with the approval of its stockholders, the 2019 Equity Incentive Plan (the “2019 Plan”) for the issuance of ISO, NSO, SARs, restricted stock, other stock awards and performance cash awards, to employees, non-employee directors, and consultants. The 2019 Plan became effective concurrent with the IPO. Awards granted under the 2019 Plan expire no later than ten years from the date of grant. For ISO and NSO, the option price shall not be less than 100% of the estimated fair value on the date of grant. Options granted typically vest over a four-year 2019 Employee Stock Purchase Plan In September 2019, the Company’s board of directors adopted, with the approval of its stockholders, the 2019 Employee Stock Purchase Plan (the “2019 ESPP”). The 2019 ESPP Plan became effective on the completion of the Company’s IPO. The 2019 ESPP authorizes the issuance of 1,280,000 shares of the Company’s common stock under purchase rights granted to its employees or to employees of any of the Company’s designated affiliates. The number of shares of the Company’s common stock reserved for issuance is subject to automatic increase at each calendar year pursuant to the terms of the 2019 ESPP. Stock Option Activity The following table summarizes option award activity under the 2016 Plan: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (Years) (in thousands) Outstanding at December 31, 2018 5,044,924 $ 1.50 9.13 Granted 2,331,293 7.49 Exercised (706,579 ) 1.50 Forfeited (352,694 ) 1.71 Outstanding at September 30, 2019 6,316,944 3.70 8.86 $ 97,018 Vested and expected to vest at September 30, 2019 6,316,944 3.70 8.86 97,018 Vested and exercisable at September 30, 2019 1,479,126 $ 2.35 8.54 $ 24,714 Aggregate intrinsic value represents the difference between the Company’s reassessed fair value of its common stock and the exercise price of outstanding options. During the three months ended September 30, 2019 and 2018, the estimated weighted-average grant date fair value of options granted was $7.64 and $1.82, respectively, and during the nine months ended September 30, 2019 and 2018, was $6.51 and $1.36 per share, respectively. As of September 30, 2019, the Company expects to recognize the remaining unamortized stock-based compensation expense of $16.2 million related to stock options, over an estimated weighted average period of 3.3 years. Stock Options Granted to Employees The fair value of stock options granted to employees was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Expected term of options (in years) 6.0 6.0 5.9 - 6.0 6.0 Expected stock price volatility 88.5% 87.6% 88.5% - 89.4% 87.6% - 88.1% Risk-free interest rate 1.9% 2.8% 1.9% - 2.5% 2.5% - 2.9% Expected dividend yield — — — — The valuation assumptions were determined as follows: Expected Term— The expected term represents the period that the options granted are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term) as the Company has concluded that its stock option exercise history does not provide a reasonable basis upon which to estimate expected term. Expected Volatility— The expected volatility was determined by examining the historical volatilities for industry peers and using an average of historical volatilities of these industry peers as the Company’s stock is not actively traded on any public markets during these periods. 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. Expected Dividend Rate— The expected dividend is zero as the Company has not paid nor does it anticipate paying any dividends on its profit interest units in the foreseeable future. Restricted Stock Activity The following table summarizes restricted stock activity: Number of Shares Weighted Average Fair Value at Date of Grant per Share Unvested as of December 31, 2018 4,814,733 $ 1.15 Vested (2,123,966 ) 1.01 Unvested as of September 30, 2019 2,690,767 $ 1.13 The unvested shares of restricted stock have not been included in the shares issued and outstanding. In January 2017, the Company entered into a restricted stock purchase agreement with an executive officer and a restricted stock purchase agreement with a director whereby the executive officer and the director purchased an aggregate of 3,624,355 shares of restricted stock. The consideration for the restricted stock was the issuance of promissory notes which are non-recourse in nature and are accounted for as in-substance stock options. The Company measured compensation cost for these in-substance options based on their estimated fair value on the grant date using the Black-Scholes pricing model. The Company is recognizing compensation cost over the requisite service period with an offsetting credit to additional paid-in capital. In August 2019, in accordance with the terms of the notes, the Company received $3.3 million as repayment of the outstanding promissory notes and accrued interest. The Company recognized a liability of $1.8 million for the portion of the promissory note repayment which relates to restricted common stock subject to future vesting as of September 30, 2019. The Company will reduce the restricted stock liability as the common stock vests. As of September 30, 2019, there was $1.6 million of total unrecognized compensation cost related to unvested restricted stock, all of which is expected to be recognized over a remaining weighted-average period of 1.1 years. Stock-Based Compensation Expense The following table sets forth the total stock-based compensation expense for all awards granted to employees and non-employees, including shares sold through the issuance of non-recourse promissory notes of which all the shares are considered to be options for accounting purposes in the Company’s statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) (in thousands) Research and development $ 926 $ 279 $ 1,925 $ 735 General and administrative 1,262 1,170 4,115 3,366 Total stock-based compensation $ 2,188 $ 1,449 $ 6,040 $ 4,101

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	1 2 . As the Company was in a loss position for all periods presented, basic net loss per share is the same as diluted net loss per share for all periods as the inclusion of all potential common securities outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: September 30, 2019 2018 Convertible preferred stock 88,112,733 69,910,520 Options issued and outstanding 6,316,944 4,800,440 Restricted shares subject to future vesting 2,690,767 5,151,810 Warrants to purchase convertible preferred stock 244,444 244,444 Total 97,364,888 80,107,214

Defined Benefit Pension and Oth

Defined Benefit Pension and Other Postretirement Plans	9 Months Ended
	Sep. 30, 2019
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Defined Benefit Pension and Other Postretirement Plans	1 3 . Postretirement Benefits (Pension Plans) for Humabs The Company’s subsidiary, Humabs, provides its Swiss employees with mandatory cash balance pension benefits whereby employer and employee contributions are accumulated in individual accounts with interest to retirement or withdrawal, if earlier. The benefits are financed through the Swiss Life Collective BVG Foundation with Swiss Life Asset Management through two separate plans. The expected rate of return on assets corresponds to the return on benefits expected to be provided under the insurance contract. Net periodic pension cost includes the following components (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 66 $ 65 $ 197 $ 196 Interest cost 8 5 24 17 Expected return on plan assets (6 ) (5 ) (17 ) (15 ) Net funded status $ 68 $ 65 $ 204 $ 198

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	1 4 . The Company’s income tax provision for interim periods is determined using an estimate of the Company’s annual effective tax rate, adjusted for discrete items arising in the quarter. The Company’s effective tax rate differs from the U.S. statutory tax rate primarily due to valuation allowances on our deferred tax assets in all jurisdictions as it is more likely than not that the Company’s deferred tax assets will not be realized. During the three and nine months ended September 30, 2019, the Company recorded an immaterial tax provision related to international income taxes. During the nine months ended September 30, 2018, the Company recorded a tax benefit of $0.5 million related to the reversal of deferred tax liability associated with the developed technology acquired from Statera.

Summary of Significant Accoun_2

Summary of Significant Accounting Policie (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. The condensed consolidated financial statements include the accounts of Vir and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated upon consolidation. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s financial information. The condensed consolidated results of operations for the nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. Certain information and footnote disclosures typically included in the Company’s annual consolidated financial statements have been condensed or omitted. As such, t hese interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements as of and for the year ended December 31, 2018 included in the prospectus dated October 10, 2019 that forms a part of the Company’s Registration Statement on Form S-1 (File No. 333-233604), as filed with the SEC pursuant to Rule 424(b) under the Securities Act of 1933 , as amended (the “Securities Act”) , on October 1 1 , 2019 (the “Prospectus”) .
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expense during the reporting periods. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates .
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents and short-term investments. Cash and cash equivalents are deposited in checking and sweep accounts at a financial institution. Such deposits may, at times, exceed federally insured limits. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and short-term investments and issuers of the short-term investments to the extent recorded on the condensed consolidated balance sheets. As of September 30, 2019, the Company has no off-balance sheet concentrations of credit risk.
Investments	Investments Investments include available-for-sale securities and are carried at estimated fair value. The Company’s valuations of marketable securities are generally derived from independent pricing services based on quoted prices in active markets for similar securities at period end. Generally, investments with original maturities beyond three months at the date of purchase and which mature at, or less than 12 months from, the consolidated balance sheet date are considered short-term investments. Unrealized gains and losses deemed temporary in nature are reported as a component of accumulated comprehensive income (loss). The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity, which is included in interest income, on the condensed consolidated statements of operations. The Company’s Swiss subsidiary holds short-term structured deposits which include a feature that provides for the instrument to be settled in U.S. dollars or Swiss Francs (CHF) depending on the strike level set at the onset of the instrument compared to the U.S. dollars to CHF exchange rate at the settlement date. The Company has elected to account for these instruments using the fair value option with gains and losses recognized in earnings.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of legal, accounting and filing fees relating to an initial public offering, are capitalized. The Company has incurred $5.6 million in deferred offering costs relating to its IPO as of September 30, 2019. The deferred offering costs were offset against offering proceeds upon the completion of the IPO in October 2019. There were no deferred offering costs capitalized as of December 31, 2018.
Convertible Preferred Stock Warrant Liability	Convertible Preferred Stock Warrant Liability A freestanding warrant to purchase shares of Series A-1 convertible preferred stock at a future date was determined to be a freestanding instrument that was accounted for as a liability. At initial recognition, the Company recorded the convertible preferred stock warrant liability on the consolidated balance sheet at its estimated fair value. The warrant liability was subject to remeasurement at each reporting period, with changes in estimated fair value recognized as a component of other income (expense), net until the exercise of the convertible preferred stock warrant or conversion of such warrant into a warrant to purchase shares of common stock. Upon the completion of the IPO in October 2019, the warrant automatically converted into a warrant to purchase shares of common stock.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In January 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-01, Financial Instrument—Overall (Subtopic 825-10) (“ASU 2016-01”), which requires entities to measure equity instruments at fair value and recognize any changes in fair value within the statement of operations. ASU 2016-01 is effective for the Company for the annual period beginning January 1, 2019, and the interim period beginning January 1, 2020. The Company is currently evaluating the impact of adopting ASU 2016-01 on the consolidated financial statements and disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (“Topic 842”). Topic 842 requires lessees to recognize all leases, including operating leases, on the balance sheet as a right-of-use asset and lease liability, unless the lease is a short-term lease. In July 2018, the FASB issued supplemental adoption guidance and clarification to Topic 842 within ASU 2018-10 Codification Improvements to Topic 842, Leases and ASU 2018-11, Targeted Improvements—Leases (Topic 842). This update provides an alternative transition method that allows entities to elect to apply the standard retrospectively as of the beginning of the latest period presented versus retrospectively as of the beginning of the earliest period presented. Topic 842 is effective for the Company for fiscal years beginning after December 15, 2019, and interim periods within fiscal years beginning after December 15, 2020, with early adoption permitted. The Company currently plans to adopt the standard on January 1, 2020 and is currently evaluating the impact of adopting Topic 842 on its consolidated financial statements and disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost, which includes the Company’s financial instruments. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss methodology, which will result in more timely recognition of credit losses. In April 2019, the FASB issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments (“ASU 2019-04”). ASU 2019-04 modified the accounting for available-for-sale debt securities, which must be individually assessed for credit losses when fair value is less than the amortized cost basis. In October 2019, the FASB affirmed a proposed ASU deferring the effective date of ASU 2016-13 for all entities except public companies that are not smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. This proposed ASU has not been finalized as of the date of this report. When finalized, the Company currently plans to adopt ASU 2016-13 effective January 1, 2023. The Company has not yet evaluated the impact of adopting this standard on the consolidated financial statements and disclosures. In January 2017, the FASB issued ASU No. 2017-04, Intangibles—Goodwill and Other: Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which simplifies the current requirements for testing goodwill for impairment by eliminating the second step of the two-step impairment test to measure the amount of an impairment loss. ASU 2017-04 is effective for the Company’s interim and annual reporting periods beginning after December 31, 2021. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2017-04 will have on its consolidated financial statements and related disclosures. The Company currently plans to adopt ASU 2017-04 on January 1, 2020 and does not expect the adoption of ASU 2017-04 to have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-14, Compensation—Retirement Benefits—Defined Benefit Plans—General (Subtopic 715-20): Disclosure Framework—Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”). ASU 2018-14 added, removed and clarified disclosure requirements related to defined benefit pension and other postretirement plans. ASU 2018-14 is effective for the Company for fiscal years ending after December 15, 2021. Early adoption is permitted for all entities. The Company currently plans to adopt ASU 2018-14 in fiscal 2022 and is still evaluating the effect that ASU 2018-14 may have on its notes to consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy: September 30, 2019 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value (in thousands) Assets: Money market funds (1) Level 1 $ 97,892 $ — $ — $ 97,892 U.S. government treasuries Level 2 226,354 158 — 226,512 Bank time deposits Level 2 4,000 — — 4,000 Total financial assets $ 328,246 $ 158 $ — $ 328,404 Liabilities: Convertible preferred stock warrant liability Level 3 $ 4,425 $ — $ — $ 4,425 Contingent consideration Level 3 10,069 — — 10,069 Total financial liabilities $ 14,494 $ — $ — $ 14,494 (1) Includes $11.7 million of restricted cash equivalents. December 31, 2018 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value (in thousands) Assets: Money market funds (1) Level 1 $ 43,600 $ — $ — $ 43,600 Structured deposits Level 2 1,000 — — 1,000 U.S. government treasuries Level 2 49,859 — (14 ) 49,845 Total financial assets $ 94,459 $ — $ (14 ) $ 94,445 Liabilities: Convertible preferred stock warrant liability Level 3 $ 1,024 $ — $ — $ 1,024 Contingent consideration Level 3 9,250 — — 9,250 Total financial liabilities $ 10,274 $ — $ — $ 10,274 (1) Includes $11.8 million of restricted cash equivalents.
Summary of Changes in Estimated Fair Value of Financial Liabilities	The following table sets forth the changes in the estimated fair value of the Company’s Level 3 financial liabilities (in thousands): Contingent Consideration Warrant Liability Total Balance at December 31, 2018 $ 9,250 $ 1,024 $ 10,274 Changes in fair value 819 3,401 4,220 Balance at September 30, 2019 $ 10,069 $ 4,425 $ 14,494
Convertible Preferred Stock Warrant Liability
Assumptions Used to Calculate Convertible Preferred Stock Warrant Liability and Stock Options	The convertible preferred stock warrant liability is valued using the Black-Scholes option pricing model. The assumptions used to calculate the convertible preferred stock warrant liability are as follows: September 30, 2019 December 31, 2018 Exercise price $ 4.50 $ 4.50 Expected term 7.0 7.7 Expected stock price volatility 88.8 % 83.5 % Risk-free interest rate 1.6 % 2.6 % Expected dividend yield — —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Property Plant and Equipment Net	Property and equipment, net consists of the following: September 30, 2019 December 31, 2018 (in thousands) Lab equipment $ 10,559 $ 7,538 Computer equipment 548 518 Furniture and fixtures 1,330 943 Leasehold improvements 7,162 3,114 Construction in progress — 1,893 Property and equipment, gross 19,599 14,006 Less accumulated depreciation and amortization (4,151 ) (1,716 ) Total property and equipment, net $ 15,448 $ 12,290
Schedule of Accrued Liabilities	Accrued liabilities consist of the following: September 30, 2019 December 31, 2018 (in thousands) Payroll and related expenses $ 6,813 $ 6,165 Research and development expenses 11,536 5,016 Restricted stock liability 1,672 — Other professional and consulting expenses 1,199 694 Other accrued expenses 1,733 2,659 Total accrued liabilities $ 22,953 $ 14,534

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Aggregate Non-cancelable Future Minimum Lease Payments Under Operating and Financing Leases	The following are the aggregate non-cancelable future minimum lease payments under operating and financing leases as of September 30, 2019 (in thousands): Year Ending December 31: Amounts 2019 (remaining three months) $ 1,105 2020 4,273 2021 4,053 2022 4,138 2023 and thereafter 8,240 Total $ 21,809

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Summary of Convertible Preferred Stock	At September 30, 2019, convertible preferred stock consisted of the following (in thousands, except share and per share amounts): September 30, 2019 Shares Authorized Shares Issued and Outstanding Issuance Price per Share Carrying Value Liquidation Preference Series A-1 310,350,000 67,611,100 $ 4.50 $ 303,224 $ 322,505 Series A-2 11,100,000 2,299,420 $ 2.57 5,913 10,968 Series B 100,000,000 18,202,213 $ 18.00 327,475 342,094 421,450,000 88,112,733 $ 636,612 $ 675,567 At December 31, 2018, convertible preferred stock consisted of the following (in thousands, except share and per share amounts): December 31, 2018 Shares Authorized Shares Issued and Outstanding Issuance Price per Share Carrying Value Liquidation Preference Series A-1 310,350,000 67,611,100 $ 4.50 $ 303,224 $ 322,100 Series A-2 11,100,000 2,299,420 $ 2.57 5,913 10,958 Series B 100,000,000 — — — — 421,450,000 69,910,520 $ 309,137 $ 333,058

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	9 Months Ended
	Sep. 30, 2019
Summary of Stock Option Activity	The following table summarizes option award activity under the 2016 Plan: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (Years) (in thousands) Outstanding at December 31, 2018 5,044,924 $ 1.50 9.13 Granted 2,331,293 7.49 Exercised (706,579 ) 1.50 Forfeited (352,694 ) 1.71 Outstanding at September 30, 2019 6,316,944 3.70 8.86 $ 97,018 Vested and expected to vest at September 30, 2019 6,316,944 3.70 8.86 97,018 Vested and exercisable at September 30, 2019 1,479,126 $ 2.35 8.54 $ 24,714
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity: Number of Shares Weighted Average Fair Value at Date of Grant per Share Unvested as of December 31, 2018 4,814,733 $ 1.15 Vested (2,123,966 ) 1.01 Unvested as of September 30, 2019 2,690,767 $ 1.13
Summary of Stock-based Compensation Expense	The following table sets forth the total stock-based compensation expense for all awards granted to employees and non-employees, including shares sold through the issuance of non-recourse promissory notes of which all the shares are considered to be options for accounting purposes in the Company’s statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) (in thousands) Research and development $ 926 $ 279 $ 1,925 $ 735 General and administrative 1,262 1,170 4,115 3,366 Total stock-based compensation $ 2,188 $ 1,449 $ 6,040 $ 4,101
Stock Option
Assumptions Used to Calculate Convertible Preferred Stock Warrant Liability and Stock Options	The fair value of stock options granted to employees was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Expected term of options (in years) 6.0 6.0 5.9 - 6.0 6.0 Expected stock price volatility 88.5% 87.6% 88.5% - 89.4% 87.6% - 88.1% Risk-free interest rate 1.9% 2.8% 1.9% - 2.5% 2.5% - 2.9% Expected dividend yield — — — —

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations	Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: September 30, 2019 2018 Convertible preferred stock 88,112,733 69,910,520 Options issued and outstanding 6,316,944 4,800,440 Restricted shares subject to future vesting 2,690,767 5,151,810 Warrants to purchase convertible preferred stock 244,444 244,444 Total 97,364,888 80,107,214

Defined Benefit Pension and O_2

Defined Benefit Pension and Other Postretirement Plans (Tables)	9 Months Ended
	Sep. 30, 2019
Defined Benefit Plans And Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Net Periodic Pension Cost	Net periodic pension cost includes the following components (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Service cost $ 66 $ 65 $ 197 $ 196 Interest cost 8 5 24 17 Expected return on plan assets (6 ) (5 ) (17 ) (15 ) Net funded status $ 68 $ 65 $ 204 $ 198

Organization - Additional Infor

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands	Oct. 10, 2019USD ($)$ / sharesshares	Sep. 16, 2019	Sep. 30, 2019USD ($)shares	Jun. 30, 2019shares	Dec. 31, 2018USD ($)shares	Sep. 30, 2018shares	Jun. 30, 2018shares	Dec. 31, 2017shares	Sep. 30, 2016shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse stock split, conversion ratio		0.222222222
Reverse stock split, description			On September 16, 2019, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-4.5 reverse split (“Reverse Split”) of shares of the Company’s common and convertible preferred stock, which was effected on September 27, 2019.
Outstanding convertible preferred stock (in shares)			88,112,733		69,910,520
Accumulated deficit | $			$ (304,748)		$ (193,836)
Cash and cash equivalents and marketable securities | $			$ 320,200
Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Outstanding convertible preferred stock (in shares)			88,112,733	88,112,733	69,910,520	69,910,520	69,466,076	65,944,430
Series A-1 Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Warrant to purchase of convertible preferred stock									244,444
Subsequent Event
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net proceeds after deducting underwriting discounts, commissions and estimated offering expenses | $	$ 127,200
Subsequent Event | Common Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Warrant to purchase of convertible preferred stock	244,444
IPO | Subsequent Event
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Issuance of common stock, shares	7,142,858
Common stock price per share | $ / shares	$ 20
Outstanding convertible preferred stock (in shares)	88,112,733
IPO | Subsequent Event | Common Stock | Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of convertible preferred stock converted to shares of common stock (in shares)	88,112,733
IPO | Subsequent Event | Common Stock | Warrant to Purchase Convertible Preferred Stock
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of convertible preferred stock converted to shares of common stock (in shares)	244,444

Summary of Significant Accoun_3

Summary of Significant Accounting Policie - Additional Information (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
IPO
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs	$ 5,600,000	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2019USD ($)	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total unrealized gains recorded in accumulated other comprehensive income (loss)	$ 200,000
Fair value assets transferred from level 1 to level 2	0
Fair value assets transferred from level 2 to level 1	0
Fair value liabilities transferred from level 1 to level 2	0
Fair value liabilities transferred from level 2 to level 1	0
Fair value assets transferred into level 3	0
Fair value assets transferred out of level 3	0
Fair value liabilities transferred into level 3	0
Fair value liabilities transferred out of level 3	$ 0
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities contractual term	1 year
Measurement Input Risk Free Interest Rate | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration estimated discount rates	0.146	0.168
Measurement Input Risk Free Interest Rate | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration estimated discount rates	0.177	0.203

Fair Value Measurements - Assum

Fair Value Measurements - Assumptions Used to Calculate Convertible Preferred Stock Warrant Liability (Details)	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2016
Exercise Price
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability			4.50
Expected Stock Price Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability			0.9932
Measurement Input Risk Free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability			0.0168
Measurement Input, Expected Dividend Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability			0
Convertible Preferred Stock Warrant Liability | Black-Scholes Option Pricing Model | Exercise Price
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability	4.50	4.50
Convertible Preferred Stock Warrant Liability | Black-Scholes Option Pricing Model | Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability	7	7.7
Convertible Preferred Stock Warrant Liability | Black-Scholes Option Pricing Model | Expected Stock Price Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability	0.888	0.835
Convertible Preferred Stock Warrant Liability | Black-Scholes Option Pricing Model | Measurement Input Risk Free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Warrant liability	0.016	0.026

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis by Level Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Sep. 30, 2019		Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets, Amortized Cost	$ 328,246		$ 94,459
Financial Assets, Gross Unrealized Holding Gains	158
Financial Assets, Gross Unrealized Holding Losses			(14)
Financial Assets, Aggregate Fair Value	328,404		94,445
Financial Liabilities, Amortized Cost	14,494		10,274
Financial Liabilities, Aggregate Fair Value	14,494		10,274
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets, Amortized Cost	97,892	[1]	43,600	[2]
Financial Assets, Aggregate Fair Value	97,892	[1]	43,600	[2]
Level 2 | U.S. Government Treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets, Amortized Cost	226,354		49,859
Financial Assets, Gross Unrealized Holding Gains	158
Financial Assets, Gross Unrealized Holding Losses			(14)
Financial Assets, Aggregate Fair Value	226,512		49,845
Level 2 | Bank Time Deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets, Amortized Cost	4,000
Financial Assets, Aggregate Fair Value	4,000
Level 2 | Structured Deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Assets, Amortized Cost			1,000
Financial Assets, Aggregate Fair Value			1,000
Level 3 | Convertible Preferred Stock Warrant Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Liabilities, Amortized Cost	4,425		1,024
Financial Liabilities, Aggregate Fair Value	4,425		1,024
Level 3 | Contingent Consideration
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial Liabilities, Amortized Cost	10,069		9,250
Financial Liabilities, Aggregate Fair Value	$ 10,069		$ 9,250
[1]	Includes $11.7 million of restricted cash equivalents.
[2]	Includes $11.8 million of restricted cash equivalents.

Fair Value Measurements - Fin_2

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis by Level Within Fair Value Hierarchy (Details) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Restricted cash equivalents	$ 11.7	$ 11.8

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Estimated Fair Value of Financial Liabilities (Details) - Level 3 $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2018	$ 10,274
Changes in fair value	4,220
Balance at September 30, 2019	14,494
Contingent Consideration
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2018	9,250
Changes in fair value	819
Balance at September 30, 2019	10,069
Warrant Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2018	1,024
Changes in fair value	3,401
Balance at September 30, 2019	$ 4,425

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details)	1 Months Ended					9 Months Ended
	Apr. 30, 2019USD ($)	Feb. 28, 2019USD ($)$ / sharesshares	Jan. 31, 2018USD ($)$ / sharesshares	Aug. 31, 2017USD ($)shares	Sep. 30, 2016USD ($)	Sep. 30, 2019USD ($)Milestone	Sep. 30, 2018USD ($)
TomegaVax
Business Acquisition [Line Items]
Business acquisition purchase price					$ 5,200,000
TomegaVax | TomegaVax Letter Agreement
Business Acquisition [Line Items]
Milestone payments aggregate amount payable, maximum					$ 30,000,000
Milestone payments related terms						the Company will be required to pay to the former stockholders of TomegaVax milestone payments of up to an aggregate of $30.0 million if the per share price of the Company’s publicly traded common stock, or implied price per share of the Company’s Series A-1 convertible preferred stock (or common stock upon conversion) upon a certain asset sale, merger or stock sale, is at least $45 (as adjusted in the case of any stock dividend, stock split or other similar recapitalization), with the amount of such payments determined by the share price and the stage of the Company’s clinical development at the time of the relevant event triggering the payment.
Contingent consideration recognized						$ 0
Humabs
Business Acquisition [Line Items]
Business acquisition purchase price				$ 42,300,000
Contingent consideration recognized				6,300,000
Business acquisition, cash consideration paid				$ 30,000,000
Business acquisition, shares issued | shares				1,666,656
Business acquisition, shares issued value				$ 2,500,000
Net working capital consideration				3,600,000
Impairment of intangible assets, excluding goodwill						0
Goodwill expected to be deductible for income tax purposes						0
Goodwill impairment						$ 0
Humabs | Developed Technologies | Minimum
Business Acquisition [Line Items]
Estimated remaining useful lives						7 years
Humabs | Developed Technologies | Maximum
Business Acquisition [Line Items]
Estimated remaining useful lives						12 years
Humabs | HBV product
Business Acquisition [Line Items]
Additional consideration payable upon achievement of specified milestone events				135,000,000
Humabs | Another Product
Business Acquisition [Line Items]
Additional consideration payable upon achievement of specified milestone events				$ 105,000,000
Agenovir
Business Acquisition [Line Items]
Business acquisition purchase price							$ 15,300,000
Milestone payments aggregate amount payable, maximum			$ 180,000,000
Contingent consideration recognized						$ 0
Business acquisition, cash consideration paid			11,500,000
Business acquisition, liabilities			1,300,000
Holdback value to satisfy claims for indemnification			2,000,000
Holdback amount paid	$ 1,800,000
Business acquisition, transaction costs			700,000
Sales milestone payments for achievement of specified levels of annual net sales of each program maximum			90,000,000
Number of milestones achieved | Milestone						0
Agenovir | HPV Program
Business Acquisition [Line Items]
Milestone payments aggregate amount payable, maximum			$ 45,000,000
Agenovir | Property and Equipment
Business Acquisition [Line Items]
Business acquisitions, purchase price allocation							800,000
Agenovir | Series A-2 Convertible Preferred Stock
Business Acquisition [Line Items]
Business acquisition, shares issued | shares			555,537
Business acquisition, shares issued value			$ 1,800,000
Share price per share | $ / shares			$ 3.15
Agenovir | In-Process Research and Development
Business Acquisition [Line Items]
Business acquisitions, purchase price allocation							$ 14,500,000
Agenovir | HBV product
Business Acquisition [Line Items]
Milestone payments aggregate amount payable, maximum			$ 45,000,000
Statera
Business Acquisition [Line Items]
Business acquisition, cash consideration paid		$ 900,000
Business acquisition, transaction costs		$ 200,000
Statera | Series A-2 Convertible Preferred Stock
Business Acquisition [Line Items]
Business acquisition, shares issued | shares		188,333
Business acquisition, shares issued value		$ 600,000
Share price per share | $ / shares		$ 3.15
Statera | Developed Technologies
Business Acquisition [Line Items]
Estimated remaining useful lives		3 years

Grant, License and Collaborat_2

Grant, License and Collaboration Agreements - Additional Information (Details) - USD ($)

1 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2019

Aug. 31, 2019

Sep. 30, 2018

Jul. 31, 2018

May 31, 2018

Oct. 31, 2017

Aug. 31, 2017

Sep. 30, 2019

Sep. 30, 2018

Sep. 30, 2019

Sep. 30, 2018

Dec. 31, 2018

Mar. 16, 2018

Jan. 26, 2018

Bill & Melinda Gates Foundation | Grant Revenue [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue from grants

$ 0

$ 800,000

$ 900,000

$ 1,500,000

National Institutes of Health

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Grant awarded amount

$ 5,100,000

5,100,000

5,100,000

National Institutes of Health | Grant Revenue [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue from grants

200,000

200,000

700,000

900,000

2017 Grant | Bill & Melinda Gates Foundation

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Grant agreement expiration date

May 31, 2019

2017 Grant | Bill & Melinda Gates Foundation | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Grant awarded amount

$ 4,700,000

Human Immunodeficiency Virus (“HIV”) Grant | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Grant awarded amount

$ 12,200,000

Human Immunodeficiency Virus (“HIV”) Grant | Bill & Melinda Gates Foundation | Grant Revenue [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue from grants

500,000

800,000

3,400,000

2,800,000

Tuberculosis (“TB”) Grant | Grant Revenue [Member]

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue from grants

400,000

1,000,000

1,800,000

1,500,000

Tuberculosis (“TB”) Grant | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Grant awarded amount

$ 14,900,000

Brii Agreement

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Written notice period for not exercising an option

30 days

Written notice period for exercise an option

180 days

Written notice period for uncured material breach

60 days

Written notice period for failure to make payment

30 days

Brii Agreement | Brii Bio Parent

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Percentage of ordinary share equal to outstanding share

9.90%

Share purchase price per share

$ 0.0001

Brii Agreement | Brii Bio Parent | Other Assets

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Estimated fair value of investments

$ 6,600,000

Brii Agreement | Brii Bio | Other Assets

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Contract liability

6,600,000

Carrying value of investment

6,600,000

6,600,000

6,600,000

$ 6,600,000

Brii Agreement | Brii Bio | Maximum

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Option exercise fee ranging from mid-single-digit

20,000,000

Option exercise fee of ranging from low tens

50,000,000

Brii Agreement | Brii Bio | Maximum | China Territory

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Sales milestone receivable

175,000,000

Brii Agreement | Brii Bio | Maximum | United States

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Sale milestone payments

175,000,000

Brii Agreement | Brii Bio | Maximum | Licensed Product-By-Licensed Product

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Milestone payment on basis ranging from mid-single-digit

30,000,000

Milestone payment on basis of ranging from low tens

$ 100,000,000

Alnylam Agreement | Alnylam

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Written notice period for exercise an option

90 days

Written notice period for uncured material breach

60 days

Written notice period for failure to make payment

30 days

Upfront fee paid

$ 10,000,000

Issuance of common stock, shares

1,111,111

Recognized liability

$ 800,000

Written notice period for licensed program other party challenges validity or enforceability of patent license.

30 days

Expenses incurred under agreement

7,500,000

1,600,000

10,700,000

7,100,000

Alnylam Agreement | Alnylam | First siRNA product

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

$ 190,000,000

Alnylam Agreement | Alnylam | Each Infectious Disease siRNA

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

115,000,000

Alnylam Agreement | Alnylam | Commercialization

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

100,000,000

Maximum aggregate milestone payment for achievement of specified development and regulatory

$ 250,000,000

Visterra Agreement | Visterra

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Expenses incurred under agreement

$ 0

0

Agreement termination, date

Nov. 30, 2019

Visterra Agreement | Visterra | Research and Development Expenses

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Upfront fee paid

25,000,000

Expenses incurred under agreement

$ 300,000

$ 2,600,000

Rockefeller Agreement | Rockefeller

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Upfront fee paid

$ 300,000

Maximum aggregate milestone payment for achievement of specified development and regulatory

40,000,000

Rockefeller Agreement | Rockefeller | Research and Development Expenses

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Annual license maintenance fees

$ 1,000,000

Rockefeller Agreement | Rockefeller | Commercialization

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Payment of annual license maintenance fees

1,000,000

Rockefeller Agreement | Rockefeller | First Infectious Disease Product

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

8,500,000

Rockefeller Agreement | Rockefeller | First Four Other Infectious Disease Products

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

7,000,000

Rockefeller Agreement | Rockefeller | Any Other Infectious Disease Product

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum milestone payment for achievement of specified development and regulatory

$ 3,600,000

2018 MedImmune Agreement | MedImmune

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

License agreement upfront payment

$ 10,000,000

2018 MedImmune Agreement | MedImmune | Influenza A and Influenza B

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Development, regulatory, and commercial milestone payments maximum amount

$ 343,300,000

2018 MedImmune Agreement | MedImmune | Influenza A

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Specified development milestones payment

5,000,000

Xencor Agreement | Xencor

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Written notice period for uncured material breach

60 days

Written notice period for failure to make payment

30 days

Specified development milestones payment

$ 800,000

Written notice period for termination of licensed program

60 days

Written notice period for termination of licensed program based on challenge

30 days

Xencor Agreement | Xencor | Influenza A Research Programs

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum aggregate development and regulatory milestone payments

$ 17,800,000

Maximum aggregate commercial sales milestone payments

60,000,000

Maximum aggregate milestone payments

77,800,000

Xencor Agreement | Xencor | HBV Research Programs

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum aggregate milestone payments

77,800,000

Xencor Agreement | Xencor | Influenza A and HBV Research Programs

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Maximum aggregate milestone payments

$ 155,500,000

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property Plant and Equipment Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 19,599	$ 14,006
Less accumulated depreciation and amortization	(4,151)	(1,716)
Total property and equipment, net	15,448	12,290
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	10,559	7,538
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	548	518
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,330	943
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,162	3,114
Construction In Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 1,893

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expenses		$ 900	$ 400	$ 2,435	$ 1,025
Proceeds from sale of property, plant, and equipment gross	$ 1,200				$ 25
Lease, term of contract	5 years
Current portion of finance lease obligation		200		200
Long-term portion of finance lease obligation		$ 900		$ 900

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Payroll and related expenses	$ 6,813	$ 6,165
Research and development expenses	11,536	5,016
Restricted stock liability	1,672
Other professional and consulting expenses	1,199	694
Other accrued expenses	1,733	2,659
Total accrued liabilities	$ 22,953	$ 14,534

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Lease arrangement, contractual expiration period, beginning year			2020
Lease arrangement, contractual expiration period, ending year			2028
Rent expense	$ 1.2	$ 0.9	$ 3.2	$ 3.1

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Aggregate Non-cancelable Future Minimum Lease Payments Under Operating and Financing Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019 (remaining three months)	$ 1,105
2020	4,273
2021	4,053
2022	4,138
2023 and thereafter	8,240
Total	$ 21,809

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended
	Aug. 31, 2019	Sep. 30, 2019	Jan. 31, 2019	Dec. 31, 2018	Jan. 31, 2017
Related Party Transaction [Line Items]
Preferred stock shares issued		88,112,733		69,910,520
Series B Convertible Preferred Stock
Related Party Transaction [Line Items]
Preferred stock shares issued			18,202,213
Promissory Note
Related Party Transaction [Line Items]
Outstanding balance of notes				$ 3,200,000
Purchase of restricted stock		3,624,355
Repayment of outstanding promissory notes and accrued interest received	$ 3,300,000
Promissory Note | Executive Officer And Director
Related Party Transaction [Line Items]
Outstanding balance of notes					$ 3,100,000
Interest rate					1.97%

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	1 Months Ended			3 Months Ended	9 Months Ended
	Jan. 31, 2019USD ($)$ / sharesshares	Jul. 31, 2018shares	Jun. 30, 2018USD ($)$ / sharesshares	Sep. 30, 2018shares	Sep. 30, 2019USD ($)Director$ / sharesshares	Sep. 30, 2018USD ($)shares	Dec. 31, 2018$ / shares
Temporary Equity [Line Items]
Gross proceeds from sale of convertible preferred stock | $					$ 317,335,000	$ 14,215,000
Dividends declared and accrued | $					$ 0
Convertible preferred stock, terms of conversion					Each share of Series A-1 convertible preferred stock, Series A-2 convertible preferred stock and Series B convertible preferred stock was convertible, at the option of the holder, into one share of common stock, subject to certain adjustments for dilution, if any, resulting from future stock issuances.
Minimum
Temporary Equity [Line Items]
Gross proceeds from sale of convertible preferred stock | $					$ 200,000,000
Percentage of convertible preferred stockholders vote for conversion					60.00%
Series A-1 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares sold			3,222,220	444,444		3,222,220
Convertible preferred stock, shares sold, price per share | $ / shares			$ 4.50		$ 4.50		$ 4.50
Gross proceeds from sale of convertible preferred stock | $			$ 14,500,000
Convertible preferred stock, additional shares authorized			1,111,121
Dividends entitled to be received by preferred stockholders | $ / shares					$ 0.27
Number of directors entitled to elect by convertible preferred stockholders before Series B issuance | Director					3
Number of directors entitled to elect by convertible preferred stockholders after Series B issuance | Director					2
Series A-1 Convertible Preferred Stock | Two Closings
Temporary Equity [Line Items]
Convertible preferred stock, shares sold			2,777,776
Series A-1 Convertible Preferred Stock | Third Closing
Temporary Equity [Line Items]
Convertible preferred stock, shares sold		444,444
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares sold	18,202,213				18,202,213
Convertible preferred stock, shares sold, price per share | $ / shares	$ 18				$ 18
Gross proceeds from sale of convertible preferred stock | $	$ 327,600,000
Convertible preferred stock, additional shares authorized	4,020,009
Dividends entitled to be received by preferred stockholders | $ / shares					$ 1.08
Number of directors entitled to elect by convertible preferred stockholders | Director					1
Senior Preferred Stock
Temporary Equity [Line Items]
Percentage of preferred stock converted into common stock					5.00%
Percentage of common stock canceled upon conversion of preferred stock					95.00%
Series A-2 Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares sold						743,870
Convertible preferred stock, shares sold, price per share | $ / shares					$ 2.57		$ 2.57
Dividends entitled to be received by preferred stockholders | $ / shares					$ 0.27
Number of directors entitled to elect by convertible preferred stockholders | Director					1

Convertible Preferred Stock - S

Convertible Preferred Stock - Summary of Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2019	Jan. 31, 2019	Dec. 31, 2018	Jun. 30, 2018
Temporary Equity [Line Items]
Shares Authorized	421,450,000		421,450,000
Shares Issued and Outstanding	88,112,733		69,910,520
Carrying Value	$ 636,612		$ 309,137
Liquidation Preference	$ 675,567		$ 333,058
Series A-1
Temporary Equity [Line Items]
Shares Authorized	310,350,000		310,350,000
Shares Issued and Outstanding	67,611,100		67,611,100
Issuance Price per Share	$ 4.50		$ 4.50	$ 4.50
Carrying Value	$ 303,224		$ 303,224
Liquidation Preference	$ 322,505		$ 322,100
Series A-2
Temporary Equity [Line Items]
Shares Authorized	11,100,000		11,100,000
Shares Issued and Outstanding	2,299,420		2,299,420
Issuance Price per Share	$ 2.57		$ 2.57
Carrying Value	$ 5,913		$ 5,913
Liquidation Preference	$ 10,968		$ 10,958
Series B
Temporary Equity [Line Items]
Shares Authorized	100,000,000		100,000,000
Shares Issued and Outstanding	18,202,213
Issuance Price per Share	$ 18	$ 18
Carrying Value	$ 327,475
Liquidation Preference	$ 342,094

Convertible Preferred Stock W_2

Convertible Preferred Stock Warrant Liability - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended
	Sep. 30, 2016$ / sharesshares	Oct. 10, 2019shares	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Class Of Warrant Or Right [Line Items]
Warrant, expiration date	Sep. 11, 2026
Warrants, expected term	10 years
Fair value of warrant at issuance | $			$ 4,425	$ 1,024
Series A-1 Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrant to purchase of convertible preferred stock	244,444
Warrants issued, exercise price | $ / shares	$ 4.50
Subsequent Event | Common Stock
Class Of Warrant Or Right [Line Items]
Warrant to purchase of convertible preferred stock		244,444
Volatility
Class Of Warrant Or Right [Line Items]
Warrants, measurement input	0.9932
Risk Free Interest Rate
Class Of Warrant Or Right [Line Items]
Warrants, measurement input	0.0168
Exercise Price
Class Of Warrant Or Right [Line Items]
Warrants, measurement input	4.50
Dividend Rate
Class Of Warrant Or Right [Line Items]
Warrants, measurement input	0

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended				3 Months Ended		9 Months Ended
	Sep. 30, 2019	Aug. 31, 2019	Jan. 31, 2017	Sep. 30, 2016	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restricted Stock Purchase Agreement | Executive Officer And Director
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of restricted stock			3,624,355
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value of options granted					$ 7.64	$ 1.82	$ 6.51	$ 1.36
Unamortized stock-based compensation expense related to stock option	$ 16.2				$ 16.2		$ 16.2
Estimated weighted average period							3 years 3 months 18 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated weighted average period							1 year 1 month 6 days
Repayment of outstanding promissory notes and accrued interest received		$ 3.3
Restricted stock liability recognized for portion of promissory note repayment	1.8				1.8		$ 1.8
Unrecognized compensation cost related to unvested restricted stock	$ 1.6				$ 1.6		$ 1.6
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of restricted stock					337,075	615,261	733,041	1,910,597
2016 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period				4 years
Shares available for grant	1,880,604				1,880,604		1,880,604
2016 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of awards from issuance date				10 years
Percentage of estimated fair value of options on the date of grant				100.00%
2019 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options vesting period	4 years
Shares reserved for issuance under the plan	5,800,000				5,800,000		5,800,000
2019 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of awards from issuance date	10 years
Percentage of estimated fair value of options on the date of grant	100.00%
2019 Employee Stock Purchase Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized to issue under purchase rights granted	1,280,000				1,280,000		1,280,000

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock Option Award Activity (Details) - Stock Option - 2016 Equity Incentive Plan $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)$ / sharesshares	Dec. 31, 2018$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options,Outstanding, Beginning Balance | shares	5,044,924
Number of Options,Granted | shares	2,331,293
Number of Options,Exercised | shares	(706,579)
Number of Options,Forfeited | shares	(352,694)
Number of Options,Outstanding, Ending Balance | shares	6,316,944	5,044,924
Number of Options,Vested and expected to vest | shares	6,316,944
Number of Options,Vested and exercisable | shares	1,479,126
Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 1.50
Weighted Average Exercise Price, Granted | $ / shares	7.49
Weighted Average Exercise Price, Exercised | $ / shares	1.50
Weighted Average Exercise Price, Forfeited | $ / shares	1.71
Weighted Average Exercise Price, Ending Balance | $ / shares	3.70	$ 1.50
Weighted Average Exercise Price,Vested and expected to vest | $ / shares	3.70
Weighted Average Exercise Price,Vested and exercisable | $ / shares	$ 2.35
Weighted Average Remaining Contractual Term	8 years 10 months 9 days	9 years 1 month 17 days
Weighted Average Remaining Contractual Term,Vested and expected to vest	8 years 10 months 9 days
Weighted Average Exercise Price,Vested and exercisable	8 years 6 months 14 days
Aggregate Intrinsic Value, Balance | $	$ 97,018
Aggregate Intrinsic Value, Vested and expected to vest | $	97,018
Aggregate Intrinsic Value, Vested and exercisable | $	$ 24,714

Stock-Based Awards - Summary _2

Stock-Based Awards - Summary of Assumptions Used for Estimating the Fair Value of Stock Options Granted (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (in years)	6 years	6 years		6 years
Expected stock price volatility	88.50%	87.60%
Expected stock price volatility,minimum			88.50%	87.60%
Expected stock price volatility,maximum			89.40%	88.10%
Risk-free interest rate	1.90%	2.80%
Risk-free interest rate, minimum			1.90%	2.50%
Risk-free interest rate, maximum			2.50%	2.90%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (in years)			5 years 10 months 24 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term of options (in years)			6 years

Stock-Based Awards - Summary _3

Stock-Based Awards - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2019$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvested, Beginning Balance | shares	4,814,733
Number of Shares, Vested | shares	(2,123,966)
Number of Shares, Unvested, Ending Balance | shares	2,690,767
Weighted Average Fair Value at Date of Grant Per Share, Beginning Balance | $ / shares	$ 1.15
Weighted Average Fair Value at Date of Grant Per Share, Vested | $ / shares	1.01
Weighted Average Fair Value at Date of Grant Per Share, Ending Balance | $ / shares	$ 1.13

Stock-Based Awards - Summary _4

Stock-Based Awards - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 2,188	$ 1,449	$ 6,040	$ 4,101
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	926	279	1,925	735
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 1,262	$ 1,170	$ 4,115	$ 3,366

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Potentially Dilutive Securities Not Included in Diluted Per Share Calculations (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	97,364,888	80,107,214
Convertible preferred stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	88,112,733	69,910,520
Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	6,316,944	4,800,440
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	2,690,767	5,151,810
Warrants to purchase convertible preferred stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	244,444	244,444

Defined Benefit Pension and O_3

Defined Benefit Pension and Other Postretirement Plans - Schedule of Net Periodic Pension Cost (Details) - Pension Plan - Humabs - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 66	$ 65	$ 197	$ 196
Interest cost	8	5	24	17
Expected return on plan assets	(6)	(5)	(17)	(15)
Net funded status	$ 68	$ 65	$ 204	$ 198

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018
Income Taxes [Line Items]
Income tax benefit	$ 13	$ (5)	$ 500
Statera | Developed Technologies
Income Taxes [Line Items]
Income tax benefit			$ 500