Adverum Biotechnologies (ADVM) 10-Q 28 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2020	May 22, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-36579
Entity Registrant Name	Adverum Biotechnologies, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-5258327
Entity Address, Address Line One	800 Saginaw Drive,
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94063
City Area Code	650
Local Phone Number	656-9323
Title of 12(b) Security	Common Stock, $0.0001 par value
Trading Symbol	ADVM
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		80,295,560
Entity Central Index Key	0001501756
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 130,162	$ 65,897
Short-term investments	166,904	100,138
Prepaid expenses and other current assets	3,382	9,835
Total current assets	300,448	175,870
Operating lease right-of-use assets	20,406	20,963
Property and equipment, net	26,727	24,884
Restricted cash	999	999
Deposit and other long-term assets	19	11
Total assets	348,599	222,727
Current liabilities:
Accounts payable	4,663	4,103
Accrued expenses and other current liabilities	8,079	11,271
Lease liability, current portion	4,025	4,034
Total current liabilities	16,767	19,408
Lease liability, net of current portion	27,753	28,214
Other non-current liabilities	126	148
Total liabilities	44,646	47,770
Stockholders’ equity:
Preferred stock	0	0
Common stock	8	7
Additional paid-in capital	712,713	560,704
Accumulated other comprehensive loss	(833)	(725)
Accumulated deficit	(407,935)	(385,029)
Total stockholders’ equity	303,953	174,957
Total liabilities and stockholders' equity	$ 348,599	$ 222,727

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating expenses:
Research and development	$ 14,751	$ 10,131
General and administrative	9,040	5,576
Total operating expenses	23,791	15,707
Operating loss	(23,791)	(15,707)
Other income, net	885	1,218
Net loss	(22,906)	(14,489)
Other comprehensive loss:
Net unrealized (loss) gain on marketable securities	(54)	3
Foreign currency translation adjustment	(54)	42
Comprehensive loss	$ (23,014)	$ (14,444)
Net loss per share — basic and diluted (in USD per share)	$ (0.31)	$ (0.23)
Weighted-average common shares used to compute net loss per share - basic and diluted (in shares)	73,797	63,125

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss)/Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		62,965,000
Beginning balance at Dec. 31, 2018	$ 201,167	$ 6	$ 522,503	$ (799)	$ (320,543)
Stock-based compensation expense	1,762		1,762
Common stock issued upon exercise of stock options (in shares)		119,000
Common stock issued upon exercise of stock options	162		162
Common stock issued upon release of restricted stock units (in shares)		397,000
Restricted stock surrendered for taxes (in shares)		(145,000)
Restricted stock surrendered for taxes	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(504)		(504)
Foreign currency translation adjustments	42			42
Unrealized gain (loss) on marketable securities, net	3			3
Net loss	(14,489)				(14,489)
Ending balance (in shares) at Mar. 31, 2019		63,336,000
Ending balance at Mar. 31, 2019	188,143	$ 6	523,923	(754)	(335,032)
Beginning balance (in shares) at Dec. 31, 2019		67,329,000
Beginning balance at Dec. 31, 2019	174,957	$ 7	560,704	(725)	(385,029)
Stock-based compensation expense	$ 3,409		3,409
Issuance of common stock, net of issuance costs of $332 (in shares)	10,925,000
Issuance of common stock, net of issuance costs of $332	$ 140,873	$ 1	140,872
Common stock issued upon exercise of stock options (in shares)	1,310,000	1,310,000
Common stock issued upon exercise of stock options	$ 9,650		9,650
Common stock issued upon exercise of warrants (in shares)	7,000
Common stock issued upon release of restricted stock units (in shares)		462,000
Restricted stock surrendered for taxes (in shares)		(155,000)
Restricted stock surrendered for taxes	$ (1,922)		(1,922)
Foreign currency translation adjustments	(54)			(54)
Unrealized gain (loss) on marketable securities, net	(54)			(54)
Net loss	(22,906)				(22,906)
Ending balance (in shares) at Mar. 31, 2020		79,878,000
Ending balance at Mar. 31, 2020	$ 303,953	$ 8	$ 712,713	$ (833)	$ (407,935)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Statement of Stockholders' Equity [Abstract]
Stock issuance costs	$ 332

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (22,906)	$ (14,489)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	599	426
Stock-based compensation expense	3,409	1,762
Amortization of premium and accrued interest on marketable securities	(179)	(129)
Other	(48)	40
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	6,345	(91)
Other assets	(8)	(18)
Operating lease right-of-use asset	557	539
Accounts payable	2,514	(136)
Accrued expenses and other current liabilities	(3,429)	(2,363)
Lease liability	(470)	1,242
Net cash used in operating activities	(13,616)	(13,217)
Cash flows from investing activities:
Purchases of marketable securities	(127,733)	(22,454)
Maturities of marketable securities	61,200	27,385
Purchases of property and equipment	(4,210)	(2,186)
Net cash (used in) provided by investing activities	(70,743)	2,745
Cash flows from financing activities:
Proceeds from offerings of common stock, net of issuance costs	140,923	0
Proceeds from issuance of common stock pursuant to option exercises	9,650	162
Taxes paid related to net share settlement of restricted stock units	(1,922)	(504)
Repayment of loan	(27)	(28)
Net cash provided by (used in) financing activities	148,624	(370)
Net increase (decrease) in cash and cash equivalents and restricted cash	64,265	(10,842)
Cash and cash equivalents and restricted cash at beginning of period	66,896	155,948
Cash and cash equivalents and restricted cash at end of period	131,161	145,106
Supplemental schedule of noncash investing and financing information
Fixed assets in accounts payable, accrued expenses and other current liabilities	$ 3,474	$ 413

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Adverum Biotechnologies, Inc. (the “Company” or "Adverum") is a clinical-stage gene therapy company targeting unmet medical needs in ocular and rare diseases. The Company develops gene therapy product candidates designed to provide durable efficacy by inducing sustained expression of a therapeutic protein. The Company’s core capabilities include clinical development, novel vector discovery, and in-house manufacturing expertise, specifically in scalable process development, assay development, and current Good Manufacturing Practices (“cGMP”) quality control. Since the Company’s inception, it has devoted its efforts to performing research and development activities, filing patent applications, hiring personnel and raising capital to support these activities. The Company has not generated any revenue from the sale of products since its inception. The Company has experienced net losses since its inception and had an accumulated deficit of $407.9 million as of March 31, 2020. The Company expects to incur losses and have negative net cash flows from operating activities as it engages in further research and development activities. The Company believes that it has sufficient funds to continue operations into 2022. Basis of Presentation —The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three months ended March 31, 2020, are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements. The full extent to which the novel coronavirus disease ("COVID-19") pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses and manufacturing, clinical trials and research and development costs, will depend on future developments that are highly uncertain at this time. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the condensed consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. Topic 326 will become effective for the

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	Fair Value Measurements and Fair Value of Financial Instruments The authoritative guidance on the fair value hierarchy for disclosure of fair value measurements is as follows: Level 1 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, 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 fair value of Level 1 securities is determined using quoted prices in active markets for identical assets. Level 1 securities consist of highly liquid money market funds. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. government and agency securities, commercial paper, corporate bond and certificates of deposit are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. The following is a summary of the Company’s cash equivalents and short-term investments: March 31, 2020 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 18,315 $ — $ — $ 18,315 Level 2: U.S. government and agency securities 86,930 78 (3) 87,005 Commercial paper 171,736 9 (121) 171,624 Corporate bonds 9,499 1 — 9,500 Total cash equivalents and short-term investments 286,480 88 (124) 286,444 Less: cash equivalents (119,540) 15 (15) (119,540) Total short-term investments $ 166,940 $ 103 $ (139) $ 166,904 December 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 15,056 $ — $ — $ 15,056 Level 2: U.S. government and agency securities 37,974 14 (2) 37,986 Commercial paper 87,983 8 (8) 87,983 Corporate bonds 10,495 6 — 10,501 Total cash equivalents and short-term investments 151,508 28 (10) 151,526 Less: cash equivalents (51,391) — 3 (51,388) Total short-term investments $ 100,117 $ 28 $ (7) $ 100,138 one

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	Balance Sheet Components Property and Equipment, Net Property and equipment, net consists of the following: March 31, 2020 December 31, 2019 (In thousands) Computer equipment and software $ 825 $ 752 Laboratory equipment 7,319 6,291 Furniture and fixtures 678 678 Leasehold improvements 26,263 1,602 Construction in progress 233 23,553 Total property and equipment 35,318 32,876 Less accumulated depreciation and amortization (8,591) (7,992) Property and equipment, net $ 26,727 $ 24,884 Depreciation and amortization expense related to property and equipment for the three months ended March 31, 2020 and 2019 was $0.6 million, and $0.4 million, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following: March 31, 2020 December 31, 2019 (In thousands) Employee compensation $ 2,299 $ 4,055 Accrued preclinical, clinical and process development costs 1,823 1,973 Accrued professional services 1,466 2,607 Other 2,491 2,636 Total accrued expenses and other current liabilities $ 8,079 $ 11,271

Equity Incentive Awards

Equity Incentive Awards	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Equity Incentive Awards	Equity Incentive Awards The following table summarizes the Company’s option activity and related information: Number of Weighted- Balance at December 31, 2019 8,995 $ 7.19 Options granted 1,594 15.15 Options exercised (1,310) 7.37 Options forfeited (207) 14.05 Balance at March 31, 2020 9,072 $ 8.41 Exercisable as of March 31, 2020 2,785 $ 6.89 Restricted Stock Units (“RSUs”) The following table summarizes the Company’s RSUs activity and related information: Number of Units Weighted- Outstanding at December 31, 2019 1,121 $ 4.59 Granted 104 15.75 Vested and released (462) 4.75 Forfeited (28) 8.39 Outstanding at March 31, 2020 735 $ 5.94 Stock-Based Compensation Expense The following table presents, by operating expense, the Company’s stock-based compensation expense: Three Months Ended 2020 2019 (In thousands) Research and development $ 1,248 $ 631 General and administrative 2,161 1,131 Total stock-based compensation expense $ 3,409 $ 1,762

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by giving effect to all potential dilutive common stock equivalents outstanding for the period using the treasury stock method. Outstanding stock options, RSUs, rights under the employee stock purchase plan (“ESPP”) and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: March 31, 2020 March 31, 2019 (In thousands) Stock options 9,072 7,969 Restricted stock units 735 1,729 ESPP 45 132 Warrants to purchase common stock 80 90 9,932 9,920

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsIn February 2020, the Company entered into a common stock purchase agreement with James Scopa, a member of the Board, and Anne Kenner, as Trustees for the James P. Scopa and Anne E. Kenner Family Trust (the “Trust”), pursuant to which the Trust purchased an aggregate of 10,000 shares of the Company’s common stock at a price of $13.75 per share, for an aggregate cash purchase price of $0.1 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation —The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and follow the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three months ended March 31, 2020, are not necessarily indicative of the results to be expected for the full year or any other future period. The balance sheet as of December 31, 2019 is derived from the audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete consolidated financial statements. The full extent to which the novel coronavirus disease ("COVID-19") pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses and manufacturing, clinical trials and research and development costs, will depend on future developments that are highly uncertain at this time.
Use of Estimates	Use of Estimates The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. GAAP. The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the condensed consolidated financial statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2016-13, Financial Instruments – Credit Losses: Measurement of Credit Losses on Financial Instruments (“ Topic 326 ”) and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. Topic 326 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. Topic 326 will become effective for the

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Summary of Cash Equivalents and Short-term Investments	The following is a summary of the Company’s cash equivalents and short-term investments: March 31, 2020 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 18,315 $ — $ — $ 18,315 Level 2: U.S. government and agency securities 86,930 78 (3) 87,005 Commercial paper 171,736 9 (121) 171,624 Corporate bonds 9,499 1 — 9,500 Total cash equivalents and short-term investments 286,480 88 (124) 286,444 Less: cash equivalents (119,540) 15 (15) (119,540) Total short-term investments $ 166,940 $ 103 $ (139) $ 166,904 December 31, 2019 Amortized Cost Basis Unrealized Gains Unrealized Estimated Fair Value (In thousands) Level 1: Money market funds $ 15,056 $ — $ — $ 15,056 Level 2: U.S. government and agency securities 37,974 14 (2) 37,986 Commercial paper 87,983 8 (8) 87,983 Corporate bonds 10,495 6 — 10,501 Total cash equivalents and short-term investments 151,508 28 (10) 151,526 Less: cash equivalents (51,391) — 3 (51,388) Total short-term investments $ 100,117 $ 28 $ (7) $ 100,138

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following: March 31, 2020 December 31, 2019 (In thousands) Computer equipment and software $ 825 $ 752 Laboratory equipment 7,319 6,291 Furniture and fixtures 678 678 Leasehold improvements 26,263 1,602 Construction in progress 233 23,553 Total property and equipment 35,318 32,876 Less accumulated depreciation and amortization (8,591) (7,992) Property and equipment, net $ 26,727 $ 24,884
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following: March 31, 2020 December 31, 2019 (In thousands) Employee compensation $ 2,299 $ 4,055 Accrued preclinical, clinical and process development costs 1,823 1,973 Accrued professional services 1,466 2,607 Other 2,491 2,636 Total accrued expenses and other current liabilities $ 8,079 $ 11,271

Equity Incentive Awards (Tables

Equity Incentive Awards (Tables)	3 Months Ended
	Mar. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Stock Options Activity	The following table summarizes the Company’s option activity and related information: Number of Weighted- Balance at December 31, 2019 8,995 $ 7.19 Options granted 1,594 15.15 Options exercised (1,310) 7.37 Options forfeited (207) 14.05 Balance at March 31, 2020 9,072 $ 8.41 Exercisable as of March 31, 2020 2,785 $ 6.89
Summary of Restricted Stock Units Activity	The following table summarizes the Company’s RSUs activity and related information: Number of Units Weighted- Outstanding at December 31, 2019 1,121 $ 4.59 Granted 104 15.75 Vested and released (462) 4.75 Forfeited (28) 8.39 Outstanding at March 31, 2020 735 $ 5.94
Stock-Based Compensation Expense	The following table presents, by operating expense, the Company’s stock-based compensation expense: Three Months Ended 2020 2019 (In thousands) Research and development $ 1,248 $ 631 General and administrative 2,161 1,131 Total stock-based compensation expense $ 3,409 $ 1,762

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following common stock equivalents outstanding at the end of the periods presented were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: March 31, 2020 March 31, 2019 (In thousands) Stock options 9,072 7,969 Restricted stock units 735 1,729 ESPP 45 132 Warrants to purchase common stock 80 90 9,932 9,920

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 407,935	$ 385,029

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Summary of Cash Equivalents and Short-term Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	$ 166,940	$ 100,117
Unrealized Gains	103	28
Unrealized Losses	(139)	(7)
Estimated Fair Value	166,904	100,138
Less: Cash Equivalents, Amortized Cost Basis	(119,540)	(51,391)
Less: Cash equivalents, unrealized gains	15	0
Less: Cash equivalents, unrealized losses	(15)	(3)
Less: Cash Equivalents, Estimated Fair Value	(119,540)	(51,388)
Money market funds | Quoted Prices in Active Markets (Level 1)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	18,315	15,056
Unrealized Gains	0	0
Unrealized Losses	0	0
Estimated Fair Value	18,315	15,056
U.S. government and agency securities | Significant Other Observable Inputs (Level 2)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	86,930	37,974
Unrealized Gains	78	14
Unrealized Losses	(3)	(2)
Estimated Fair Value	87,005	37,986
Commercial paper | Significant Other Observable Inputs (Level 2)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	171,736	87,983
Unrealized Gains	9	8
Unrealized Losses	(121)	(8)
Estimated Fair Value	171,624	87,983
Corporate Bonds | Significant Other Observable Inputs (Level 2)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	9,499	10,495
Unrealized Gains	1	6
Unrealized Losses	0	0
Estimated Fair Value	9,500	10,501
Total Cash Equivalents and Short-term Investments
Debt Securities, Available-for-sale [Line Items]
Amortized Cost Basis	286,480	151,508
Unrealized Gains	88	28
Unrealized Losses	(124)	(10)
Estimated Fair Value	$ 286,444	$ 151,526

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Detail)	Mar. 31, 2020USD ($)
Debt Securities, Available-for-sale [Line Items]
Marketable securities	$ 20,300,000
Other than temporary impaired investments	$ 0
Minimum
Debt Securities, Available-for-sale [Line Items]
Marketable securities term	1 year
Maximum
Debt Securities, Available-for-sale [Line Items]
Marketable securities term	2 years

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 35,318	$ 32,876
Less accumulated depreciation and amortization	(8,591)	(7,992)
Property and equipment, net	26,727	24,884
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	825	752
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	7,319	6,291
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	678	678
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	26,263	1,602
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 233	$ 23,553

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 599	$ 426

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Accrued professional services	$ 1,466	$ 2,607
Employee compensation	2,299	4,055
Accrued preclinical, clinical and process development costs	1,823	1,973
Other	2,491	2,636
Total accrued expenses and other current liabilities	$ 8,079	$ 11,271

Equity Incentive Awards - Summa

Equity Incentive Awards - Summary of Stock Options Activity (Detail) shares in Thousands	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Options Outstanding [Roll Forward]
Beginning balance (in shares) | shares	8,995
Options granted (in shares) | shares	1,594
Options exercised (in shares) | shares	(1,310)
Options forfeited (in shares) | shares	(207)
Ending balance (in shares) | shares	9,072
Exercisable (in shares) | shares	2,785
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in USD per share) | $ / shares	$ 7.19
Options granted (in USD per share) | $ / shares	15.15
Options exercised (in USD per share) | $ / shares	7.37
Options forfeited (in USD per share) | $ / shares	14.05
Ending balance (in USD per share) | $ / shares	8.41
Exercisable (in USD per share) | $ / shares	$ 6.89

Equity Incentive Awards - Sum_2

Equity Incentive Awards - Summary of Restricted Stock Units Activity (Detail) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance (in shares) | shares	1,121
Granted (in shares) | shares	104
Vested and released (in shares) | shares	(462)
Forfeited (in shares) | shares	(28)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (in USD per share)	$ 4.59
Granted (in USD per share)	15.75
Vested and released (in USD per share)	4.75
Forfeited (in USD per share)	8.39
Ending balance (in USD per share)	$ 5.94

Equity Incentive Awards - Stock

Equity Incentive Awards - Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 3,409	$ 1,762
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,248	631
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 2,161	$ 1,131

Net Loss per Share - Additional

Net Loss per Share - Additional Information (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	9,932	9,920
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	9,072	7,969
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	735	1,729
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	45	132
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from net loss per share (in shares)	80	90

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Feb. 29, 2020	Mar. 31, 2020
Related Party Transaction [Line Items]
Issuance of common stock		10,925,000
Common Stock | Trust
Related Party Transaction [Line Items]
Issuance of common stock	10,000
Share price	$ 13.75
Cash purchase price	$ 0.1