Intellia Therapeutics (NTLA) 10-Q 7 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 01, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	NTLA
Entity Registrant Name	INTELLIA THERAPEUTICS, INC.
Entity Central Index Key	0001652130
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		51,380,479
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-37766
Entity Tax Identification Number	36-4785571
Entity Address, Address Line One	40 Erie Street
Entity Address, Address Line Two	Suite 130
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	857
Local Phone Number	285-6200
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current Assets:
Cash and cash equivalents	$ 80,993	$ 57,226
Marketable securities	169,266	222,500
Accounts receivable	13,368	4,620
Prepaid expenses and other current assets	6,133	5,135
Total current assets	269,760	289,481
Marketable securities - noncurrent		4,746
Property and equipment, net	17,251	17,996
Operating lease right-of-use assets	24,918	19,137
Other assets	2,823	2,920
Total Assets	314,752	334,280
Current Liabilities:
Accounts payable	3,870	3,941
Accrued expenses	13,102	13,273
Current portion of operating lease liability	5,693	5,745
Current portion of deferred revenue	12,639	12,674
Total current liabilities	35,304	35,633
Deferred revenue, net of current portion	13,020	16,136
Long-term operating lease liability	18,669	12,630
Commitments and contingencies (Note 6)
Stockholders’ Equity:
Common stock, $0.0001 par value; 120,000,000 shares authorized; 50,602,875 and 50,198,044 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	5	5
Additional paid-in capital	580,065	570,493
Accumulated other comprehensive income	373	261
Accumulated deficit	(332,684)	(300,878)
Total stockholders’ equity	247,759	269,881
Total Liabilities and Stockholders’ Equity	$ 314,752	$ 334,280

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	50,602,875	50,198,044
Common stock, shares outstanding	50,602,875	50,198,044

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Collaboration revenue	$ 12,916	$ 10,433
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 34,650	$ 23,709
General and administrative	11,314	10,533
Total operating expenses	45,964	34,242
Operating loss	(33,048)	(23,809)
Interest income	1,242	1,869
Net loss	$ (31,806)	$ (21,940)
Net loss per share, basic and diluted	$ (0.63)	$ (0.49)
Weighted average shares outstanding, basic and diluted	50,491	45,234
Other comprehensive loss:
Unrealized gain on marketable securities	$ 112	$ 87
Comprehensive loss	$ (31,694)	$ (21,853)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended	71 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Mar. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (31,806)	$ (21,940)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,541	1,300
Equity-based compensation	4,157	4,592
Accretion of investment discounts	(200)	(1,422)
Changes in operating assets and liabilities:
Accounts receivable	(8,748)	3,956
Prepaid expenses and other current assets	(448)	(150)
Operating right-of-use assets	1,566	1,299
Other assets	97	84
Accounts payable	(370)	1,356
Accrued expenses	177	(2,605)
Deferred revenue	(3,151)	(6,842)
Operating lease liabilities	(1,360)	(1,081)
Net cash used in operating activities	(38,545)	(21,453)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(845)	(1,533)
Purchases of marketable securities	(31,207)	(19,272)
Maturities of marketable securities	89,500	26,500
Net cash provided by investing activities	57,448	5,695
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from common stock offerings, net of offering costs	4,528	3,639		$ 658,700
Proceeds from options exercised	336	360
Net cash provided by financing activities	4,864	3,999
Net increase (decrease) in cash and cash equivalents	23,767	(11,759)
Cash and cash equivalents, beginning of period	57,226	58,856	$ 58,856
Cash and cash equivalents, end of period	80,993	47,097	$ 57,226	$ 80,993
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Purchases of property and equipment unpaid at period end	750	$ 446
Right-of-use assets acquired under operating leases	7,347
Proceeds from at-the-market offerings unpaid at period end	$ 551

Overview and Basis of Presentat

Overview and Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Overview and Basis of Presentation	1. Overview and Basis of Presentation Intellia Therapeutics, Inc. (“Intellia” or the “Company”) is a leading genome editing company focused on developing curative therapeutics utilizing a biological tool known as CRISPR/Cas9, which stands for C lustered, R egularly I nterspaced S hort P alindromic R epeats (“CRISPR”)/CRISPR associated 9 (“Cas9”) is a technology for genome editing, the process of altering selected sequences of genomic deoxyribonucleic acid (“DNA”). transform medicine by editing disease-associated genes with a single treatment course, and that it can also be used to create novel engineered cell therapies that can replace a patient’s diseased cells or effectively target various cancers and autoimmune diseases. The Company is leveraging its leading scientific expertise, clinical development experience and intellectual property (“IP”) position to unlock a broad set of therapeutic applications for CRISPR/Cas9 genome editing and to develop a potential new class of therapeutic products. The condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K (“Annual Report”) for the year ended December 31, 2019. The unaudited condensed consolidated financial statements include the accounts of Intellia Therapeutics, Inc. and its wholly owned, controlled subsidiary, Intellia Securities Corp. All intercompany balances and transactions have been eliminated in consolidation. Comprehensive loss is comprised of net loss and gain/loss on marketable securities. The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, judgments and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates in these condensed consolidated financial statements have been made in connection with the calculation of revenues, research and development expenses and equity-based compensation expense. The Company bases its estimates on historical experience and various other assumptions that management believes to be reasonable under the circumstances at the time such estimates are made. Actual results could differ from those estimates. The Company periodically reviews its estimates in light of changes in circumstances, facts and experience. The extent of the impact of the coronavirus disease 19 (“COVID-19”) pandemic on the Company’s operational and financial performance will depend on certain developments, including the length and severity of this pandemic, as well as its effect on our employees, collaborators and vendors, all of which are uncertain and cannot be predicted. The Company cannot reasonably estimate the extent to which the disruption may materially impact its consolidated results of operations or financial position. The effects of material revisions in estimates are reflected in the condensed consolidated financial statements prospectively from the date of the change in estimate. Certain prior year amounts have been reclassified in order to conform to the current year presentation. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Liquidity Since its inception through March 31, 2020, the Company has raised an aggregate of $658.7 million to fund its operations, of which $155.5 million was through its collaboration agreements, $170.5 million was from its initial public offering and concurrent private placements, $141.0 million was from a follow-on public offering, $106.7

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies The Company’s significant accounting policies are described in Note 2, “Summary of Significant Accounting Policies” to the consolidated financial statements included in the Annual Report for the year ended December 31, 2019. There have been no material changes during the three months ended March 31, 2020, other than as noted below Recent Accounting Pronouncements – Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement . In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . Recent Accounting Pronouncements – Issued but not yet adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes .

Marketable Securities

Marketable Securities	3 Months Ended
	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Marketable Securities	3. Marketable Securities The following table summarizes the Company’s available-for-sale marketable securities as of March 31, 2020 and December 31, 2019 at net book value: March 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) Marketable securities: U.S. Treasury securities $ 101,432 $ 381 $ - $ 101,813 Financial institution debt securities 54,019 20 (27 ) 54,012 Corporate debt securities 4,942 - - 4,942 Other asset-backed securities 8,499 - - 8,499 Total $ 168,892 $ 401 $ (27 ) $ 169,266 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) Marketable securities: U.S. Treasury securities $ 159,361 $ 142 $ (1 ) $ 159,502 Financial institution debt securities 40,173 105 - 40,278 Corporate debt securities 18,966 1 - 18,967 Other asset-backed securities 8,485 14 - 8,499 Total $ 226,985 $ 262 $ (1 ) $ 227,246 The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At March 31, 2020 and December 31, 2019, the balance in the Company’s accumulated other comprehensive income was composed of activity related to the Company’s available-for-sale marketable securities. There were no material realized gains or losses in the three months ended March 31, 2020 or for the year ended December 31, 2019 and, as a result, the Company did not reclassify any amounts out of accumulated other comprehensive income during the period. The Company did not have any securities in a material unrealized loss position at March 31, 2020. The Company's available-for-sale securities that are classified as short-term marketable securities in the condensed consolidated balance sheet mature within one year or less as of the balance sheet date. Available-for-sale securities that are classified as noncurrent in the condensed consolidated balance sheet mature after one year but within five years from the balance sheet date. At March 31, 2020 and December 31, 2019, the Company did not hold any investments that matured beyond five years of the balance sheet date.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	4 . Fair Value Measurements The Company classifies fair value-based measurements using a three-level hierarchy that prioritizes the inputs used to measure fair value. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1, quoted market prices in active markets for identical assets or liabilities; Level 2, observable inputs other than quoted market prices included in Level 1, such as quoted market prices for markets that are not active or other inputs that are observable or can be corroborated by observable market data; and 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, including certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. As of March 31, 2020 and December 31, 2019, the Company’s financial assets recognized at fair value on a recurring basis consisted of the following: Fair Value as of March 31, 2020 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents $ 77,382 $ 77,382 $ - $ - Marketable securities: U.S. Treasury securities 101,813 101,813 - - Financial institution debt securities 54,012 - 54,012 - Corporate debt securities 4,942 - 4,942 - Other asset-backed securities 8,499 - 8,499 - Total marketable securities 169,266 101,813 67,453 - Total $ 246,648 $ 179,195 $ 67,453 $ - Fair Value as of December 31, 2019 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents $ 46,917 $ 46,917 $ - $ - Marketable securities: U.S. Treasury securities 159,502 159,502 - - Financial institution debt securities 40,278 - 40,278 - Corporate debt securities 18,967 - 18,967 - Other asset-backed securities 8,499 - 8,499 - Total marketable securities 227,246 159,502 67,744 - Total $ 274,163 $ 206,419 $ 67,744 $ - The Company’s financial assets, which include cash equivalents and marketable securities, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models and observable market inputs to determine value . After completing our validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of March 31, 2020 or December Other financial instruments, including accounts receivable, accounts payable and accrued expense, are carried at cost, which approximate fair value due to the short duration and term to maturity.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses	5 . Accrued Expenses Accrued expenses consisted of the following: March 31, 2020 December 31, 2019 (In thousands) Accrued research and development $ 6,324 $ 4,208 Employee compensation and benefits 3,172 6,311 Accrued legal and professional expenses 2,535 1,563 Accrued other 1,071 1,191 Total accrued expenses $ 13,102 $ 13,273

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Litigation There have been no material changes to any of the outstanding litigation, nor is the Company a party to any new litigation, since December 31, 2019. For further information please see the notes to the consolidated financial statements included in the Company’s Annual Report for the year ended December 31, 2019. License Agreements The Company is party to license agreements, which include contingent payments. These payments will become payable if and when certain development, regulatory and commercial milestones are achieved. As of March 31, 2020, the satisfaction and timing of the contingent payments is uncertain and not reasonably estimable .

Collaborations

Collaborations	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaborations	7 . Collaborations To accelerate the development and commercialization of CRISPR/Cas9-based products in multiple therapeutic areas, the Company has formed, and intends to seek other opportunities to form, strategic alliances with collaborators who can augment its leadership in CRISPR/Cas9 therapeutic development. As of March 31, 2020 and 2019, the Company’s accounts receivable and contract liabilities were primarily related to the Company’s collaborations with Novartis Institutes for BioMedical Research (“Novartis”) and Regeneron Pharmaceuticals, Inc. (“Regeneron”). The following table presents changes in the Company’s accounts receivable and contract liabilities during the three months ended March 31, 2020 and 2019 (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Three Months Ended March 31, 2020 Accounts receivable $ 4,620 $ 9,765 $ (1,017 ) $ 13,368 Contract liabilities: Deferred revenue $ 28,810 $ - $ (3,151 ) $ 25,659 Balance at Beginning of Period Additions Deductions Balance at End of Period Three Months Ended March 31, 2019 Accounts receivable $ 7,547 $ 3,591 $ (7,547 ) $ 3,591 Contract liabilities: Deferred revenue $ 55,932 $ 1,000 $ (7,842 ) $ 49,090 During the three months ended March 31, 2020 and 2019, the Company recognized the following revenues as a result of changes in the contract liability balance (in thousands): Three Months Ended March 31, Revenue recognized in the period from: 2020 2019 Amounts included in the contract liability at the beginning of the period $ 3,151 $ 7,842 Costs to obtain and fulfill a contract The Company did not incur any expenses to obtain collaboration agreements and costs to fulfill those contracts do not generate or enhance resources of the Company. As such, no costs to obtain or fulfill a contract have been capitalized in any period. Regeneron Pharmaceuticals, Inc. In April 2016, the Company entered into a license and collaboration agreement with Regeneron (the “Regeneron Agreement”). The research collaboration term ends in April 2022, except that Regeneron may make a one-time payment of $25.0 million to extend the term for an additional two-year Revenue Recognition – Collaboration Revenue. Through March 31, 2020, the Company recorded a $75.0 million upfront payment under the Regeneron Agreement and $28.8 million for research and development services under the ATTR Co/Co agreement. Through March 31, 2020, the Company has recognized $78.2 million of collaboration revenue under both arrangements, including $7.9 million during the three months ended March 31, 2020 and $5.7 million during the three months ended March 31, 2019, in the condensed consolidated statements of operations and comprehensive loss. This includes $4.8 million and $2.6 million during the three months ended March 31, 2020 and 2019, respectively, representing payments due from Regeneron pursuant to the ATTR Co/Co agreement, which is accounted for under Accounting Standards Codification 808, . As of March 31, 2020, there was approximately $25.7 million of the aggregate transaction price of the Regeneron Agreement remaining to be recognized, which the Company expects to be recognized ratably through April 2022. As of March 31, 2020 and December 31, 2019, the Company had accounts receivable of $8.4 million and $3.6 million, respectively, and deferred revenue of $25.7 million and $28.8 million, respectively, related to these arrangements. Novartis Institutes for BioMedical Research In December 2014, the Company entered into a strategic collaboration agreement with Novartis (the “2014 Novartis Agreement”), primarily focused on the research of new ex vivo Revenue Recognition – Collaboration Revenue. Through March 31, 2020, excluding amounts allocated to Novartis’ purchase of the Company’s Class A-1 and Class A-2 Preferred Units, the Company had recorded a total of $62.4 million in cash and accounts receivable under the 2014 Novartis Agreement and the Novartis Amendment. Through March 31, 2020, the Company recognized $62.4 million of collaboration revenue, including a $5.0 million development milestone payment that was previously constrained during the three months ended March 31, 2020 and $4.7 million during the three months ended March 31, 2019, in the condensed consolidated statements of operations and comprehensive loss related to the 2014 Novartis Agreement and the Novartis Amendment. As of December 31, 2019, the aggregate transaction price had been recognized in full. Revenue Recognition – Milestone . During the three months ended March 31, 2020, the U.S. Food and Drug Administration (“FDA”) accepted the investigational new drug (“IND”) application submitted by Novartis for a CRISPR/Cas9-based engineered cell therapy for the treatment of sickle cell disease. As a result of meeting this milestone, the Company recognized $5.0 million as collaboration revenue within the condensed consolidated statement of operations and comprehensive loss. No other milestones under the 2014 Novartis Agreement and the Novartis Amendment were achieved during the three months ended March 31, 2020 or 2019. The Company is eligible to receive additional downstream success-based milestones and royalties. As of March 31, 2020 and December 31, 2019, the Company had accounts receivable of $5.0 million and $1.0 million, respectively, related to the 2014 Novartis Agreement and the Novartis Amendment. As of March 31, 2020 and December 31, 2019, the Company had no deferred revenue related to the 2014 Novartis Agreement and the Novartis Amendment.

Leases

Leases	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases	8 . Leases In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street (the “130 Brookline Lease”) in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year five-year January 2025 In March 2020, the Company entered into an agreement to lease approximately 39,000 square feet of office and laboratory space at 281 Albany Street in Cambridge, Massachusetts under an operating lease agreement (the “281 Albany Lease”). The 281 Albany Lease is expected to commence on October 1, 2020, and the Company’s obligation to pay rent will start on the date that is six months after the commencement date or the date on which the Company occupies the premises, whichever occurs earlier (the “Rent Commencement Date”). The initial term of the 281 Albany Lease is ten years following the Rent Commencement Date. The base rent under the 281 Albany Lease is $99.00 per square foot per year during the first year of the term, which is subject to scheduled annual increases up to $128.87 per square foot per year during the last year of the initial term, plus certain operating expenses and taxes. In addition, the landlord will contribute an aggregate of $4.4 million toward the cost of construction and tenant improvements for the premises. The Company has the option to extend the 281 Albany Lease for two successive five-year terms.

Equity-Based Compensation

Equity-Based Compensation	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity-Based Compensation	9 . Equity-Based Compensation In April 2016, the Company adopted the Amended and Restated 2015 Stock Option and Incentive Plan (the “2015 Plan”). The 2015 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units (“RSUs”) and other stock-based awards. Recipients of incentive stock options and non-qualified stock options are eligible to purchase shares of the Company’s common stock at an exercise price equal to the fair value of such stock on the grant date. Stock options granted under the 2015 Plan generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, unless they contain specific performance-based vesting provisions. The maximum term of stock options granted under the 2015 Plan is ten years. As of March 31, 2020, there were 2,556,282 shares available for future issuance. The number of shares reserved for issuance under the 2015 Plan shall be cumulatively increased by four percent of the number of shares of stock issued and outstanding on the immediately preceding December 31 or such lesser number of shares of stock as determined by the board of directors. Equity-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended March 31, 2020 2019 (In thousands) Research and development $ 2,160 $ 1,783 General and administrative 1,997 2,809 Total $ 4,157 $ 4,592 Restricted Stock Restricted stock is measured at fair value based on the quoted price of the Company’s common stock. The following table summarizes the Company’s restricted stock activity for the three months ended March 31, 2020: Number of Shares Weighted Average Grant Date Fair Value per Share Unvested restricted stock as of December 31, 2019 71,875 $ 22.88 Granted 181,020 15.05 Vested - - Cancelled (4,410 ) 15.05 Unvested restricted stock as of March 31, 2020 248,485 $ 17.31 As of March 31, 2020, there was $2.6 In January 2020, the Company granted 181,020 RSUs to certain employees that include a performance condition in addition to a service condition. The RSUs vest over a period of three years and are subject to accelerated vesting based on the Company’s programs achieving certain development milestones before December 1, 2022. To date, the Company has not accelerated the vesting of the RSUs. The grant date fair value of the RSUs is $15.05. Stock Options The weighted average grant date fair value of options, estimated as of the grant date using the Black-Scholes option pricing model, was $7.96 Three Months Ended March 31, 2020 2019 Risk-free interest rate 1.0% 2.6% Expected life of options 6.0 years 6.0 years Expected volatility of underlying stock 66.7% 69.2% Expected dividend yield 0.0% 0.0% Risk-free Interest Rate. The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant with maturities approximately equal to the option’s expected term. Expected Dividend Yield. The expected dividend yield assumption is based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends. Expected Volatility. The expected volatility was derived from a blend of average historical stock volatilities of several peer companies within the Company’s industry and the Company’s historical volatility, both over a period equivalent to the expected term of the stock option grants. Expected Term. The expected term represents the period that stock option awards are expected to be outstanding. For option grants that are considered to be “plain vanilla,” the Company determines the expected term using the simplified method. The simplified method deems the term to be the average of the time-to-vesting and the contractual life of the options. The Company uses the simplified method because it does not have sufficient historical option exercise data to provide a reasonable basis upon which to estimate the expected term . The Company uses the market closing price of its common stock as reported on the Nasdaq Global Select Market to determine the fair value of the shares of common stock underlying stock options. The following is a summary of stock option activity for the three months ended March 31, 2020: Number of Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (In years) (In thousands) Outstanding at December 31, 2019 5,365,971 $ 15.67 Granted 2,103,480 13.31 Exercised (53,579 ) 6.28 Forfeited (172,777 ) 16.23 Outstanding at March 31, 2020 7,243,095 $ 15.04 8.22 $ 5,134 Exercisable at March 31, 2020 2,847,849 $ 14.35 6.76 $ 5,134 As of March 31, 2020, there was $39.3 Of the unvested stock options outstanding as of March 31, 2020, 213,750 obtaining certain scientific, financial and regulatory milestones through 2020 are not included in computing the diluted loss per share because the performance criteria had not been met as of the end of the reporting period

Loss Per Share

Loss Per Share	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Loss Per Share	10 . Loss Per Share The Company calculates basic loss per share by dividing net loss for each respective period by the weighted average number of common shares outstanding for each respective period. The Company computes diluted loss per share after giving consideration to the dilutive effect of stock options and unvested restricted stock that are outstanding during the period, except where such securities would be anti-dilutive. Basic and diluted loss per share was calculated as follows: Three Months Ended March 31, 2020 2019 (In thousands, except per share data) Net loss $ (31,806 ) $ (21,940 ) Weighted average shares outstanding, basic and diluted 50,491 45,234 Net loss per share, basic and diluted $ (0.63 ) $ (0.49 ) The following common stock equivalents were excluded from the calculation of diluted loss per share because their inclusion would have been anti-dilutive: Three Months Ended March 31, 2020 2019 (In thousands) Unvested restricted stock 248 79 Stock options 7,243 5,331 7,491 5,410

Stockholders_ Equity

Stockholders’ Equity	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Stockholders’ Equity	11 . Stockholders’ Equity The following tables present changes in stockholders’ equity for the three months ended March 31, 2020 and 2019 (in thousands, except share data): Additional Accumulated Other Total Common Paid-In Comprehensive Accumulated Stockholders’ Shares Amount Capital (Loss) Income Deficit Equity Balance at December 31, 2019 50,198,044 $ 5 $ 570,493 $ 261 $ (300,878 ) $ 269,881 Issuance of common stock through at-the-market offerings, net of issuance costs of $48 351,252 - 5,079 - - 5,079 Exercise of stock options 53,579 - 336 - - 336 Equity-based compensation - - 4,157 - - 4,157 Other comprehensive gain - - - 112 - 112 Net loss - - - - (31,806 ) (31,806 ) Balance at March 31, 2020 50,602,875 $ 5 $ 580,065 $ 373 $ (332,684 ) $ 247,759 Additional Accumulated Other Total Common Paid-In Comprehensive Accumulated Stockholders’ Shares Amount Capital (Loss) Income Deficit Equity Balance at December 31, 2018 45,224,480 $ 5 $ 478,968 $ (28 ) $ (201,025 ) $ 277,920 Retroactive adjustment to beginning accumulated deficit for adoption of ASC 842 - - - - (320 ) (320 ) Issuance of common stock through at-the-market offerings, net of issuance costs of $120 223,818 - 3,639 - - 3,639 Exercise of stock options 30,800 - 360 - - 360 Equity-based compensation - - 4,592 - - 4,592 Other comprehensive gain - - - 87 - 87 Net loss - - - - (21,940 ) (21,940 ) Balance at March 31, 2019 45,479,098 $ 5 $ 487,559 $ 59 $ (223,285 ) $ 264,338 At-the-Market Offering Programs On October 12, 2018, the Company filed a Registration Statement on Form S-3 (the “2018 Shelf”) with the SEC in relation to the registration of common stock, preferred stock, warrants and units of any combination thereof for the purposes of selling, from time to time, its common stock, convertible securities or other equity securities in one or more offerings. The Company also simultaneously entered into an Open Market Sale Agreement (the “2018 Sales Agreement”) with Jefferies LLC, (the “Sales Agent”), to provide for the offering, issuance and sale by the Company of up to an aggregate amount of $100.0 million of its common stock from time to time in “at-the-market” offerings under the 2018 Shelf and subject to the limitations thereof. The Company paid to the Sales Agent cash commissions of 3.0% of the gross proceeds of sales of common stock under the 2018 Sales Agreement. I the sales. During the year ended December 31, 2019, the Company issued an additional 4,231,348 shares of its common stock, in a series of sales, at an average price of $16.57 per share, in accordance with the 2018 Sales Agreement, for aggregate net proceeds of $67.8 million, after payment of cash commissions to the Sales Agent and approximately $0.2 million related to legal, accounting and other fees in connection with the sales. . On August 23, 2019, the Company filed a Registration Statement on Form S-3, as amended (the “2019 Shelf”) with the SEC in relation to the registration of common stock, preferred stock, warrants and units of any combination thereof. The Company also simultaneously entered into an Open Market Sale Agreement (the “2019 Sales Agreement”) with the Sales Agent, to provide for the offering, issuance and sale by the Company of up to an aggregate amount of $150.0 million of its common stock from time to time in “at-the-market” offerings under the 2019 Shelf and subject to the limitations thereof. The Company agreed to pay to the Sales Agent cash commissions of 3.0% of the gross proceeds of sales of common stock under the 2019 Sales Agreement. During the year ended December 31, 2019, the Company issued 287,231 16.48 4.4 approximately $0.2 million . $15.05 per approximately $0.1 million related to legal, accounting and other fees in connection with the sales. recorded as a current asset offerings with trade dates in March 2020 that were settled by April 2, 2020. As of March 31, 2020, $140.0 million in shares of common stock remain eligible for sale under the 2019 Sales

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	1 2 . Related Party Transactions Research Material Supplier In the ordinary course of business, the Company may purchase materials or supplies from entities that are associated with a party that meets the criteria of a related party of the Company. These transactions are reviewed quarterly and to date have not been material to the Company’s condensed consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Recent Accounting Pronouncements - Adopted	Recent Accounting Pronouncements – Adopted In August 2018, the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement . In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments .
Recent Accounting Pronouncements – Issued but not yet adopted	Recent Accounting Pronouncements – Issued but not yet adopted In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes .

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Summary of Available-for-sale Marketable Securities	The following table summarizes the Company’s available-for-sale marketable securities as of March 31, 2020 and December 31, 2019 at net book value: March 31, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) Marketable securities: U.S. Treasury securities $ 101,432 $ 381 $ - $ 101,813 Financial institution debt securities 54,019 20 (27 ) 54,012 Corporate debt securities 4,942 - - 4,942 Other asset-backed securities 8,499 - - 8,499 Total $ 168,892 $ 401 $ (27 ) $ 169,266 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value (In thousands) Marketable securities: U.S. Treasury securities $ 159,361 $ 142 $ (1 ) $ 159,502 Financial institution debt securities 40,173 105 - 40,278 Corporate debt securities 18,966 1 - 18,967 Other asset-backed securities 8,485 14 - 8,499 Total $ 226,985 $ 262 $ (1 ) $ 227,246

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Summary of Financial Assets Recognized at Fair Value on Recurring Basis	As of March 31, 2020 and December 31, 2019, the Company’s financial assets recognized at fair value on a recurring basis consisted of the following: Fair Value as of March 31, 2020 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents $ 77,382 $ 77,382 $ - $ - Marketable securities: U.S. Treasury securities 101,813 101,813 - - Financial institution debt securities 54,012 - 54,012 - Corporate debt securities 4,942 - 4,942 - Other asset-backed securities 8,499 - 8,499 - Total marketable securities 169,266 101,813 67,453 - Total $ 246,648 $ 179,195 $ 67,453 $ - Fair Value as of December 31, 2019 Total Level 1 Level 2 Level 3 (In thousands) Cash equivalents $ 46,917 $ 46,917 $ - $ - Marketable securities: U.S. Treasury securities 159,502 159,502 - - Financial institution debt securities 40,278 - 40,278 - Corporate debt securities 18,967 - 18,967 - Other asset-backed securities 8,499 - 8,499 - Total marketable securities 227,246 159,502 67,744 - Total $ 274,163 $ 206,419 $ 67,744 $ -

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following: March 31, 2020 December 31, 2019 (In thousands) Accrued research and development $ 6,324 $ 4,208 Employee compensation and benefits 3,172 6,311 Accrued legal and professional expenses 2,535 1,563 Accrued other 1,071 1,191 Total accrued expenses $ 13,102 $ 13,273

Collaborations (Tables)

Collaborations (Tables)	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Changes in Accounts Receivable and Contract Liabilities	The following table presents changes in the Company’s accounts receivable and contract liabilities during the three months ended March 31, 2020 and 2019 (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Three Months Ended March 31, 2020 Accounts receivable $ 4,620 $ 9,765 $ (1,017 ) $ 13,368 Contract liabilities: Deferred revenue $ 28,810 $ - $ (3,151 ) $ 25,659 Balance at Beginning of Period Additions Deductions Balance at End of Period Three Months Ended March 31, 2019 Accounts receivable $ 7,547 $ 3,591 $ (7,547 ) $ 3,591 Contract liabilities: Deferred revenue $ 55,932 $ 1,000 $ (7,842 ) $ 49,090
Summary of Revenues Recognized Resulting From Changes in Contract Liability Balance	During the three months ended March 31, 2020 and 2019, the Company recognized the following revenues as a result of changes in the contract liability balance (in thousands): Three Months Ended March 31, Revenue recognized in the period from: 2020 2019 Amounts included in the contract liability at the beginning of the period $ 3,151 $ 7,842

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Equity-Based Compensation Expense	Equity-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows Three Months Ended March 31, 2020 2019 (In thousands) Research and development $ 2,160 $ 1,783 General and administrative 1,997 2,809 Total $ 4,157 $ 4,592
Summary of Restricted Stock Activity	The following table summarizes the Company’s restricted stock activity for the three months ended March 31, 2020: Number of Shares Weighted Average Grant Date Fair Value per Share Unvested restricted stock as of December 31, 2019 71,875 $ 22.88 Granted 181,020 15.05 Vested - - Cancelled (4,410 ) 15.05 Unvested restricted stock as of March 31, 2020 248,485 $ 17.31
Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted	Key assumptions used to apply this pricing model were as follows: Three Months Ended March 31, 2020 2019 Risk-free interest rate 1.0% 2.6% Expected life of options 6.0 years 6.0 years Expected volatility of underlying stock 66.7% 69.2% Expected dividend yield 0.0% 0.0%
Summary of Stock Option Activity	The following is a summary of stock option activity for the three months ended March 31, 2020 Number of Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (In years) (In thousands) Outstanding at December 31, 2019 5,365,971 $ 15.67 Granted 2,103,480 13.31 Exercised (53,579 ) 6.28 Forfeited (172,777 ) 16.23 Outstanding at March 31, 2020 7,243,095 $ 15.04 8.22 $ 5,134 Exercisable at March 31, 2020 2,847,849 $ 14.35 6.76 $ 5,134

Loss Per Share (Tables)

Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss Per Share	Basic and diluted loss per share was calculated as follows: Three Months Ended March 31, 2020 2019 (In thousands, except per share data) Net loss $ (31,806 ) $ (21,940 ) Weighted average shares outstanding, basic and diluted 50,491 45,234 Net loss per share, basic and diluted $ (0.63 ) $ (0.49 )
Potential Dilutive Securities Excluded from Computation of Diluted Net Loss Per Common Share	The following common stock equivalents were excluded from the calculation of diluted loss per share because their inclusion would have been anti-dilutive: Three Months Ended March 31, 2020 2019 (In thousands) Unvested restricted stock 248 79 Stock options 7,243 5,331 7,491 5,410

Stockholders_ Equity (Tables)

Stockholders’ Equity (Tables)	3 Months Ended
	Mar. 31, 2020
Equity [Abstract]
Schedule of Changes in Stockholders’ Equity	The following tables present changes in stockholders’ equity for the three months ended March 31, 2020 and 2019 (in thousands, except share data): Additional Accumulated Other Total Common Paid-In Comprehensive Accumulated Stockholders’ Shares Amount Capital (Loss) Income Deficit Equity Balance at December 31, 2019 50,198,044 $ 5 $ 570,493 $ 261 $ (300,878 ) $ 269,881 Issuance of common stock through at-the-market offerings, net of issuance costs of $48 351,252 - 5,079 - - 5,079 Exercise of stock options 53,579 - 336 - - 336 Equity-based compensation - - 4,157 - - 4,157 Other comprehensive gain - - - 112 - 112 Net loss - - - - (31,806 ) (31,806 ) Balance at March 31, 2020 50,602,875 $ 5 $ 580,065 $ 373 $ (332,684 ) $ 247,759 Additional Accumulated Other Total Common Paid-In Comprehensive Accumulated Stockholders’ Shares Amount Capital (Loss) Income Deficit Equity Balance at December 31, 2018 45,224,480 $ 5 $ 478,968 $ (28 ) $ (201,025 ) $ 277,920 Retroactive adjustment to beginning accumulated deficit for adoption of ASC 842 - - - - (320 ) (320 ) Issuance of common stock through at-the-market offerings, net of issuance costs of $120 223,818 - 3,639 - - 3,639 Exercise of stock options 30,800 - 360 - - 360 Equity-based compensation - - 4,592 - - 4,592 Other comprehensive gain - - - 87 - 87 Net loss - - - - (21,940 ) (21,940 ) Balance at March 31, 2019 45,479,098 $ 5 $ 487,559 $ 59 $ (223,285 ) $ 264,338

Overview and Basis of Present_2

Overview and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		71 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from common stock offering	$ 4,528	$ 3,639	$ 658,700
Proceeds from issuance of convertible preferred stock			85,000
Collaborative Arrangement [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from common stock offering			155,500
Initial Public Offering and Concurrent Private Placements [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from common stock offering			170,500
Follow-on public Offering [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from common stock offering			141,000
At-the-market Offering [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from common stock offering			$ 106,700

Marketable Securities - Summary

Marketable Securities - Summary of Available -for-sale Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Amortized Cost	$ 168,892	$ 226,985
Gross Unrealized Gains	401	262
Gross Unrealized Losses	(27)	(1)
Estimated Fair Value	169,266	227,246
U.S. Treasury Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	101,432	159,361
Gross Unrealized Gains	381	142
Gross Unrealized Losses		(1)
Estimated Fair Value	101,813	159,502
Financial Institution Debt Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	54,019	40,173
Gross Unrealized Gains	20	105
Gross Unrealized Losses	(27)
Estimated Fair Value	54,012	40,278
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	4,942	18,966
Gross Unrealized Gains		1
Estimated Fair Value	4,942	18,967
Other Asset Backed Securities [Member]
Marketable Securities [Line Items]
Amortized Cost	8,499	8,485
Gross Unrealized Gains		14
Estimated Fair Value	$ 8,499	$ 8,499

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Realized gains or losses on marketable securities	$ 0	$ 0
Investments that matured beyond five years	$ 0	$ 0
Minimum [Member]
Marketable Securities [Line Items]
Available-for-sales Securities, non-current, maturity period	1 year
Maximum [Member]
Marketable Securities [Line Items]
Available-for-sales Securities, non-current, maturity period	5 years

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Recognized at Fair Value on Recurring Basis (Detail) - Fair Value on Recurring Basis [Member] - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 77,382	$ 46,917
Marketable securities:
Marketable securities	169,266	227,246
Total	246,648	274,163
U.S. Treasury Securities [Member]
Marketable securities:
Marketable securities	101,813	159,502
Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	54,012	40,278
Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	4,942	18,967
Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	8,499	8,499
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	77,382	46,917
Marketable securities:
Marketable securities	101,813	159,502
Total	179,195	206,419
Level 1 [Member] | U.S. Treasury Securities [Member]
Marketable securities:
Marketable securities	101,813	159,502
Level 2 [Member]
Marketable securities:
Marketable securities	67,453	67,744
Total	67,453	67,744
Level 2 [Member] | Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	54,012	40,278
Level 2 [Member] | Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	4,942	18,967
Level 2 [Member] | Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	$ 8,499	$ 8,499

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued research and development	$ 6,324	$ 4,208
Employee compensation and benefits	3,172	6,311
Accrued legal and professional expenses	2,535	1,563
Accrued other	1,071	1,191
Total accrued expenses	$ 13,102	$ 13,273

Collaborations - Summary of Cha

Collaborations - Summary of Changes in Accounts Receivable and Contract Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounts receivable:
Accounts receivable, Balance at Beginning of Period	$ 4,620	$ 7,547
Accounts receivable, Additions	9,765	3,591
Accounts receivable, Deductions	(1,017)	(7,547)
Accounts receivable, Balance at End of Period	13,368	3,591
Contract liabilities:
Deferred revenue, Balance at Beginning of Period	28,810	55,932
Deferred revenue, Additions		1,000
Deferred revenue, Deductions	(3,151)	(7,842)
Deferred revenue, Balance at End of Period	$ 25,659	$ 49,090

Collaborations - Summary of Rev

Collaborations - Summary of Revenues Recognized Resulting From Changes in Contract Liability Balance (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue From Contract With Customer [Abstract]
Amounts included in the contract liability at the beginning of the period	$ 3,151	$ 7,842

Collaborations - Additional Inf

Collaborations - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 13, 2019	Jul. 31, 2018	Apr. 30, 2016	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue				$ 12,916	$ 10,433
Deferred revenue				25,659	49,090	$ 25,659	$ 25,659	$ 28,810	$ 55,932
Regeneron Pharmaceuticals Inc. [Member] | Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
One time collaboration payment			$ 25,000
Collaboration term extension period			2 years
Payment of royalty percentage on net product sales	25.00%	50.00%
Deferred revenue additions						75,000
Collaboration revenue				$ 7,900	5,700	78,200
Aggregate transaction price remaining to be recognized, period				Through March 31, 2020
Payments due				$ 4,800	2,600
Aggregate transaction price remaining to be recognized				25,700		25,700	25,700
Accounts receivable				8,400		8,400	8,400	3,600
Deferred revenue				$ 25,700		25,700	25,700	28,800
Regeneron Pharmaceuticals Inc. [Member] | Regeneron Agreement [Member] | Research and Development Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue						28,800
Novartis [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Strategic collaboration agreement amended date				2018-12
Novartis [Member] | Regeneron Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue				$ 5,000
Deferred revenue				0		0	0	0
Accounts receivable				5,000		$ 5,000	5,000	$ 1,000
Novartis [Member] | Novartis Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue additions							62,400
Collaboration revenue				$ 5,000	$ 4,700		$ 62,400
Aggregate transaction price remaining to be recognized, period				Through March 31, 2020

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	1 Months Ended		3 Months Ended
	Apr. 30, 2019	Oct. 31, 2014USD ($)	Mar. 31, 2020USD ($)ft²USD_per_sqft	Dec. 31, 2019USD ($)
Lessee Lease Description [Line Items]
Operating lease right-of-use assets			$ 24,918	$ 19,137
130 Brookline Street [Member]
Lessee Lease Description [Line Items]
Operating lease, description			In October 2014, the Company entered into an agreement to lease office and laboratory space at 130 Brookline Street (the “130 Brookline Lease”) in Cambridge, Massachusetts under an operating lease agreement with a term through January 2020, with an option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025.
Operating lease expiration		2020-01
Lessee operating lease extended expiration date	Jan. 31, 2025
Operating lease, existence of option to extend		true
Operating lease, options to extend			option to extend the term of the lease for an additional five-year period. In April 2019, the Company executed an amendment to the lease to extend the term of the lease for the additional five-year period, through January 2025.
Operating lease, renewal term	5 years	5 years
130 Brookline Street [Member] | Second Amendment [Member]
Lessee Lease Description [Line Items]
Operating lease, description			In March 2020, the Company entered into a second amendment to the 130 Brookline Lease (the “Second Amendment”). The Second Amendment amends certain terms of the Company’s existing lease, dated October 21, 2014, as amended on April 5, 2019. The Second Amendment extends the term of the 130 Brookline Lease by approximately six years through January 31, 2031.
Lessee operating lease extended expiration date			Jan. 31, 2031
Operating lease, existence of option to extend			true
Operating lease, options to extend			an option to extend the lease for two consecutive five-year terms
Operating lease, renewal term			6 years
Operating lease right-of-use assets			$ 7,300
Operating lease, liability			$ 7,300
130 Brookline Street [Member] | Other Assets [Member]
Lessee Lease Description [Line Items]
Lease security deposit		$ 300
Albany Lease [Member]
Lessee Lease Description [Line Items]
Area of space leased | ft²			39,000
Operating lease, description			In March 2020, the Company entered into an agreement to lease approximately 39,000 square feet of office and laboratory space at 281 Albany Street in Cambridge, Massachusetts under an operating lease agreement (the “281 Albany Lease”). The 281 Albany Lease is expected to commence on October 1, 2020, and the Company’s obligation to pay rent will start on the date that is six months after the commencement date or the date on which the Company occupies the premises, whichever occurs earlier (the “Rent Commencement Date”).
Expected commencement date			Oct. 1, 2020
Term of lease			10 years
Base rent per square foot for first year | USD_per_sqft			99
Base rent per square foot for last year | USD_per_sqft			128.87
Amount receivable on cost of construction and tenant improvement			$ 4,400
Operating lease, existence of option to extend			true
Operating lease, options to extend			The Company has the option to extend the 281 Albany Lease for two successive five-year terms.

Equity-Based Compensation - Add

Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation expense related to restricted stock		$ 2.6
Potential dilutive securities excluded from computation of diluted net loss per common share		7,491,000	5,410,000
Number of Shares, Granted		181,020
Weighted Average Grant Date Fair Value per Share, Granted		$ 15.05
Weighted average grant date fair value per share		$ 7.96	$ 8.94
Total intrinsic value of stock options exercised		$ 0.3	$ 0.1
Unrecognized compensation cost related to stock options		$ 39.3
Stock options outstanding		7,243,095		5,365,971
Vesting description		that vest upon obtaining certain scientific, financial and regulatory milestones through 2020
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unrecognized compensation costs		2 years 7 months 6 days
Performance Based RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share		71,875
RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period	3 years
Number of Shares, Granted	181,020
Weighted Average Grant Date Fair Value per Share, Granted	$ 15.05
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of unrecognized compensation costs		2 years 9 months 18 days
Performance Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share		173,750
Stock options outstanding		213,750
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining vesting period		3 years
Description of stock options granted under the Plan		Stock options granted under the 2015 Plan generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, unless they contain specific performance-based vesting provisions. The maximum term of stock options granted under the 2015 Plan is ten years.
Shares available for future issuance		2,556,282
Percentage of cumulative increase in number of shares for future issuance		4.00%
2015 Plan [Member] | First Anniversary of Original Vesting Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vest percentage on the first anniversary		25.00%
Maximum [Member] | 2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term of stock options granted		10 years

Equity-Based Compensation - Sch

Equity-Based Compensation - Schedule of Equity-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 4,157	$ 4,592
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	2,160	1,783
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Equity-based compensation expense	$ 1,997	$ 2,809

Equity-Based Compensation - Sum

Equity-Based Compensation - Summary of Restricted Stock Activity (Detail)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested, Beginning balance | shares	71,875
Number of Shares, Granted | shares	181,020
Number of Shares, Cancelled | shares	(4,410)
Number of Shares, Unvested, Ending balance | shares	248,485
Weighted Average Grant Date Fair Value per Share, Unvested, Beginning balance | $ / shares	$ 22.88
Weighted Average Grant Date Fair Value per Share, Granted | $ / shares	15.05
Weighted Average Grant Date Fair Value per Share, Cancelled | $ / shares	15.05
Weighted Average Grant Date Fair Value per Share, Unvested, Ending balance | $ / shares	$ 17.31

Equity-Based Compensation - S_2

Equity-Based Compensation - Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted (Detail)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	1.00%	2.60%
Expected life of options	6 years	6 years
Expected volatility of underlying stock	66.70%	69.20%
Expected dividend yield	0.00%	0.00%

Equity-Based Compensation - S_3

Equity-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding, Beginning Balance | shares	5,365,971
Number of options, Granted | shares	2,103,480
Number of options, Exercised | shares	(53,579)
Number of options, Forfeited | shares	(172,777)
Number of Options, Outstanding, Ending Balance | shares	7,243,095
Number of Options, Exercisable | shares	2,847,849
Weighted Average Exercise Price per Share, Outstanding, Beginning Balance | $ / shares	$ 15.67
Weighted Average Exercise Price per Share, Granted | $ / shares	13.31
Weighted Average Exercise Price per Share, Exercised | $ / shares	6.28
Weighted Average Exercise Price per Share, Forfeited | $ / shares	16.23
Weighted Average Exercise Price per Share, Outstanding, Ending Balance | $ / shares	15.04
Weighted Average Exercise Price per Share, Exercisable | $ / shares	$ 14.35
Weighted Average Remaining Contractual Term, Outstanding	8 years 2 months 19 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 9 months 3 days
Aggregate Intrinsic Value, Outstanding | $	$ 5,134
Aggregate Intrinsic Value, Exercisable | $	$ 5,134

Loss Per Share - Schedule of Ba

Loss Per Share - Schedule of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net loss	$ (31,806)	$ (21,940)
Weighted average shares outstanding, basic and diluted	50,491	45,234
Net loss per share, basic and diluted	$ (0.63)	$ (0.49)

Loss Per Share - Potential Dilu

Loss Per Share - Potential Dilutive Securities Excluded from Computation of Diluted Net Loss Per Common Share (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]
Potential dilutive securities excluded from computation of diluted net loss per common share	7,491	5,410
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	248	79
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	7,243	5,331

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Changes in Stockholders Equity (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Class Of Stock [Line Items]
Beginning balance	$ 269,881	$ 277,920	$ 277,920
Beginning balance, shares	50,198,044
Issuance of common stock through at-the-market offerings, net of issuance costs	$ 5,079	3,639
Exercise of stock options	$ 336	360
Exercise of stock options, shares	53,579
Equity-based compensation	$ 4,157	4,592
Other comprehensive gain	112	87
Net loss	(31,806)	(21,940)
Ending balance	$ 247,759	264,338	$ 269,881
Ending balance, shares	50,602,875		50,198,044
ASC 842 [Member]
Class Of Stock [Line Items]
Retroactive adjustment to beginning accumulated deficit foradoption of ASC 842		(320)
Common Stock [Member]
Class Of Stock [Line Items]
Beginning balance	$ 5	$ 5	$ 5
Beginning balance, shares	50,198,044	45,224,480	45,224,480
Issuance of common stock through at-the-market offering, net of issuance costs, shares	351,252	223,818
Exercise of stock options, shares	53,579	30,800
Ending balance	$ 5	$ 5	$ 5
Ending balance, shares	50,602,875	45,479,098	50,198,044
Additional Paid-In Capital [Member]
Class Of Stock [Line Items]
Beginning balance	$ 570,493	$ 478,968	$ 478,968
Issuance of common stock through at-the-market offerings, net of issuance costs	5,079	3,639
Exercise of stock options	336	360
Equity-based compensation	4,157	4,592
Ending balance	580,065	487,559	570,493
Accumulated Other Comprehensive (Loss) Income [Member]
Class Of Stock [Line Items]
Beginning balance	261	(28)	(28)
Other comprehensive gain	112	87
Ending balance	373	59	261
Accumulated Deficit [Member]
Class Of Stock [Line Items]
Beginning balance	(300,878)	(201,025)	(201,025)
Net loss	(31,806)	(21,940)
Ending balance	$ (332,684)	(223,285)	$ (300,878)
Accumulated Deficit [Member] | ASC 842 [Member]
Class Of Stock [Line Items]
Retroactive adjustment to beginning accumulated deficit foradoption of ASC 842		$ (320)

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Changes in Stockholders Equity (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity [Abstract]
Stock issuance cost,net	$ 48	$ 120

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 23, 2019	Oct. 12, 2018	Nov. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Mar. 31, 2020
Class Of Stock [Line Items]
Proceeds from common stock offering				$ 4,528	$ 3,639		$ 658,700
2018 Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering			$ 28,500			$ 67,800
Percentage of gross proceeds from common stock as sales agent cash commission		3.00%
Number of common stock issued upon conversion of shares			1,659,300			4,231,348
Common stock price per share			$ 18			$ 16.57
2018 Sales Agreement [Member] | General and Administrative Expenses [Member]
Class Of Stock [Line Items]
Legal accounting and other fees			$ 400			$ 200
2018 Sales Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering		$ 100,000
2019 Sales Agreement [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering				$ 5,100		$ 4,400
Percentage of gross proceeds from common stock as sales agent cash commission				3.00%
Number of common stock issued upon conversion of shares				351,252		287,231
Common stock price per share				$ 15.05		$ 16.48	$ 15.05
Proceeds from common stock offering				$ 140,000			$ 140,000
2019 Sales Agreement [Member] | Current Assets [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering				500
2019 Sales Agreement [Member] | General and Administrative Expenses [Member]
Class Of Stock [Line Items]
Legal accounting and other fees				$ 100		$ 200
2019 Sales Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Proceeds from common stock offering	$ 150,000