Beam Therapeutics (BEAM) 10-Q 12 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 08, 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	BEAM
Entity Registrant Name	Beam Therapeutics Inc.
Entity Central Index Key	0001745999
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		51,485,115
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.01 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39208
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-5238376
Entity Address, Address Line One	26 Landsdowne Street
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	327-8775
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	$ 126,050	$ 37,221
Marketable securities	127,392	54,627
Prepaid expenses and other current assets	6,192	2,696
Total current assets	259,634	94,544
Property and equipment, net	24,802	24,290
Restricted cash	13,332	13,332
Operating lease right-of-use assets	22,126	18,957
Other assets	2,744	4,976
Total assets	322,638	156,099
Current liabilities:
Accounts payable	6,101	7,846
Accrued expenses and other current liabilities	8,480	7,852
Derivative liabilities	10,500	7,800
Current portion of lease liability	4,699	4,337
Current portion of equipment financing liability	1,660	1,303
Total current liabilities	31,440	29,138
Long-term lease liability	24,059	21,187
Long-term equipment financing liability	5,333	4,411
Other liabilities	412	418
Total liabilities	61,244	55,154
Commitments and contingencies (See Note 7, Leases, and Note 8, License agreements)
Stockholders’ equity (deficit):
Preferred stock, $0.01 par value; 25,000,000 and no shares authorized at March 31, 2020 and December 31, 2019, respectively, and no shares issued or outstanding at March 31, 2020 and December 31, 2019, respectively
Common stock, $0.01 par value; 250,000,000 and 205,000,000 shares authorized, 51,345,290 and 9,981,991 issued, and 49,077,350 and 7,326,185 outstanding at March 31, 2020 and December 31, 2019, respectively	491	73
Additional paid-in capital	494,749	1,851
Accumulated other comprehensive (loss) income	(344)	16
Accumulated deficit	(233,502)	(203,044)
Total stockholders’ equity (deficit)	261,394	(201,104)
Total liabilities, redeemable convertible preferred stock, and stockholders’ equity (deficit)	$ 322,638	156,099
Redeemable Convertible Preferred Stock
Current liabilities:
Redeemable convertible preferred stock		$ 302,049

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	250,000,000	205,000,000
Common stock, shares issued	51,345,290	9,981,991
Common stock, shares outstanding	49,077,350	7,326,185

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Other Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
License revenue	$ 6
Revenue, Product and Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 21,549	$ 9,179
General and administrative	6,812	3,929
Total operating expenses	28,361	13,108
Loss from operations	(28,355)	(13,108)
Other income (expense):
Change in fair value of derivative liabilities	(2,700)	(1,000)
Interest and other income, net	597	498
Total other expense	(2,103)	(502)
Net loss	(30,458)	(13,610)
Unrealized loss on marketable securities	(360)
Comprehensive loss	(30,818)	(13,610)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(30,458)	(13,610)
Accretion of redeemable convertible preferred stock to redemption value, including dividends on preferred stock	(1,277)	(2,963)
Net loss attributable to common stockholders	$ (31,735)	$ (16,573)
Net loss per common share attributable to common stockholders, basic and diluted	$ (1.03)	$ (2.86)
Weighted-average common shares used in net loss per share attributable to common stockholders, basic and diluted	30,725,077	5,795,481

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit	Redeemable Convertible Preferred Stock
Beginning Balance at Dec. 31, 2018	$ (117,406)	$ 56	$ 7,256		$ (124,718)
Beginning Balance, Shares at Dec. 31, 2018		5,565,368
Redeemable convertible preferred stock, Beginning Balance at Dec. 31, 2018						$ 251,434
Redeemable convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2018						119,308,387
Issuance of Series B redeemable convertible preferred stock, net of issuance costs of $0.1 million						$ 37,901
Issuance of Series B redeemable convertible preferred stock, net of issuance costs of $0.1 million, Shares						11,308,397
Accretion of redeemable convertible preferred stock to redemption value						$ 2,963
Accretion of redeemable convertible preferred stock to redemption value	(2,963)		(2,963)
Vesting of restricted common stock		$ 4	(4)
Vesting of restricted common stock, Shares		388,562
Issuance of common stock related to license agreement	113		113
Issuance of common stock related to license agreement, Shares		16,725
Stock-based compensation	869		869
Exercise of common stock options	7		7
Exercise of common stock options, Shares		12,502
Net loss	(13,610)				(13,610)
Redeemable convertible preferred stock, Ending Balance at Mar. 31, 2019						$ 292,298
Redeemable convertible preferred stock, Ending Balance, Shares at Mar. 31, 2019						130,616,784
Ending Balance at Mar. 31, 2019	(132,990)	$ 60	5,278		(138,328)
Ending Balance, Shares at Mar. 31, 2019		5,983,157
Beginning Balance at Dec. 31, 2019	(201,104)	$ 73	1,851	$ 16	(203,044)
Beginning Balance, Shares at Dec. 31, 2019		7,326,185
Redeemable convertible preferred stock, Beginning Balance at Dec. 31, 2019						$ 302,049
Redeemable convertible preferred stock, Beginning Balance, Shares at Dec. 31, 2019						130,616,784
Accretion of redeemable convertible preferred stock to redemption value						$ 1,277
Accretion of redeemable convertible preferred stock to redemption value	(1,277)		(1,277)
Conversion of preferred stock to common stock upon closing of initial public offering						$ (303,326)
Conversion of preferred stock to common stock upon closing of initial public offering, Shares						(130,616,784)
Conversion of preferred stock to common stock upon closing of initial public offering	303,326	$ 291	303,035
Conversion of preferred stock to common stock upon closing of initial public offering, Shares		29,127,523
Issuance of common stock from initial public offering, net of issuance costs of $18.7 million	188,323	$ 122	188,201
Issuance of common stock from initial public offering, net of issuance costs of $18.7 million, Shares		12,176,471
Vesting of restricted common stock		$ 4	(4)
Vesting of restricted common stock, Shares		387,866
Stock-based compensation	2,792		2,792
Exercise of common stock options	$ 152	$ 1	151
Exercise of common stock options, Shares	59,305	59,305
Other comprehensive loss	$ (360)			(360)
Net loss	(30,458)				(30,458)
Ending Balance at Mar. 31, 2020	$ 261,394	$ 491	$ 494,749	$ (344)	$ (233,502)
Ending Balance, Shares at Mar. 31, 2020		49,077,350

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Issuance of common stock from initial public offering, net of issuance costs	$ 18.7
Series B Redeemable Convertible Preferred Stock
Issuance of Series B redeemable convertible preferred stock, net of issuance costs		$ 0.1

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net loss	$ (30,458)	$ (13,610)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,100	735
Amortization of investment premiums	(129)
Stock-based compensation expense	2,792	869
Change in operating lease right-of-use assets	952	206
Non-cash research and development license expense	264	113
Change in fair value of derivative liabilities	2,700	1,000
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,559)	(425)
Other long-term assets	(77)	(78)
Accounts payable	(471)	(1,517)
Accrued expenses and other liabilities	378	(595)
Operating lease liabilities	(879)	(382)
Financing milestone liabilities		(12,000)
Other long-term liabilities	(6)	(173)
Net cash used in operating activities	(27,393)	(25,857)
Investing activities
Purchases of property and equipment	(3,046)	(2,354)
Purchases of marketable securities	(117,719)
Maturities of marketable securities	44,723
Purchase of long-term investment	(750)
Net cash used in investing activities	(76,792)	(2,354)
Financing activities
Proceeds from issuance of Series B Preferred Stock, net		37,901
Proceeds from initial public offering, net of underwriting discount	192,510
Payment of initial public offering costs	(958)
Proceeds from equipment financings	1,625
Repayment of equipment financings	(315)
Proceeds from exercise of stock options	152	7
Net cash provided by financing activities	193,014	37,908
Net change in cash, cash equivalents and restricted cash	88,829	9,697
Cash, cash equivalents and restricted cash—beginning of period	50,553	147,936
Cash, cash equivalents and restricted cash—end of period	139,382	157,633
Supplemental disclosure of cash flow information:
Cash paid for interest	134
Supplemental disclosure of noncash investing and financing activities:
Conversion of redeemable convertible preferred stock to common stock upon closing of the initial public offering	303,326
Property and equipment additions in accounts payable and accrued expenses	1,032	1,573
Operating lease liabilities arising from obtaining right-of-use assets	4,032
Issuance of common stock for research and development license		113
Equity issuance costs in accounts payable and accrued expenses	707
Accretion of redeemable convertible preferred stock to redemption value, including dividends on preferred stock	$ 1,277	$ 2,963

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the business and basis of presentation Organization Beam Therapeutics Inc. (the “Company” or “Beam”) is a research stage biotechnology company committed to creating a new class of precision genetic medicines, based on the Company’s proprietary base editing technology, with a vision of providing life-long cures to patients suffering from serious diseases. The Company was incorporated in January 2017 as a Delaware corporation and began operations in July 2017. Its principal offices are in Cambridge, Massachusetts. Liquidity and capital resources Since its inception, the Company has devoted substantially all of our resources to building our base editing platform and advancing development of our portfolio of programs, establishing and protecting our intellectual property, conducting research and development activities, organizing and staffing our company, business planning, raising capital and providing general and administrative support for these operations. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. In connection with the Company’s initial public offering, or IPO, the Company’s board of directors approved a one-for-4.4843 reverse stock split of its issued and outstanding common stock and stock options and a proportional adjustment to the existing conversion ratios for the Company’s redeemable convertible preferred stock effective as of January 24, 2020. Accordingly, all common stock shares, per share amounts, and additional paid in capital amounts for all periods presented in the accompanying financial statements have been retroactively adjusted, where applicable, to reflect the reverse stock split and adjustment to the preferred stock conversion ratios. In February 2020, the Company completed its IPO in which the Company issued and sold 12,176,471 shares of its common stock, including 1,588,235 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $17.00 per share, for aggregate gross proceeds of $207.0 million. The Company received approximately $188.3 million in net proceeds after deducting underwriting discounts and estimated offering expenses payable by the Company. In connection with the IPO, all outstanding shares of redeemable convertible preferred stock converted into 29,127,523 shares of the Company’s common stock. Since its inception, the Company has incurred substantial losses and had an accumulated deficit of $233.5 million as of March 31, 2020. The Company expects to generate operating losses and negative operating cash flows for the foreseeable future. The Company expects that its cash, cash equivalents, and marketable securities as of March 31, 2020 of $253.4 million will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these financial statements. The Company will need additional financing to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed would have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability, and it may never do so. Basis of presentation The accompanying condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP, and pursuant to the rules and regulations of the Securities and Exchange Commission, or SEC. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited financial statements. In the opinion of the Company’s management, the accompanying unaudited interim condensed consolidated financial statements contain all adjustments that are necessary to present fairly the Company’s financial position as of March 31, 2020, the results of its operations and other comprehensive loss, redeemable convertible preferred stock and stockholders’ equity (deficit), and cash flows for the three months ended March 31, 2020 and 2019. Such adjustments are of a normal and recurring nature. The results for the three months ended March 31, 2020 are not necessarily indicative of the results for the year ending December 31, 2020, or for any future period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2019, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 30, 2020. Consolidation The accompanying condensed consolidated financial statements include the accounts of Beam Therapeutics Inc. and its wholly owned subsidiaries, Blink Therapeutics Inc., or Blink, which is a Delaware subsidiary that holds certain intellectual property related to RNA base editing, and Beam Therapeutics Securities Corporation, which is a Massachusetts subsidiary created to buy, sell and hold securities. All intercompany transactions and balances have been eliminated in consolidation. COVID-19-related significant risks and uncertainties With the global spread of the ongoing coronavirus disease of 2019, or COVID-19, pandemic in the first and second quarters of 2020, the Company has implemented business continuity plans designed to address and mitigate the impact of the COVID-19 pandemic on its business. In March 2020, to protect the health of its employees, and their families and communities, the Company restricted access to its offices to personnel who must perform critical activities that must be completed on-site, limited the number of such personnel that can be present at its facilities at any one time, and requested that most of its employees work remotely. In May 2020, as restrictions are eased and the number of remote employees are reduced, the Company expects to incur additional costs to provide a safe working environment to its onsite employees. The extent to which the COVID-19 pandemic impacts the Company’s business, its corporate development objectives, results of operations and financial condition, and the value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, social distancing and business closure requirements, and the effectiveness of actions taken globally to contain and treat the disease. Disruptions to the global economy, disruption of global healthcare systems, and other significant impacts of the COVID-19 pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. While the COVID-19 pandemic did not significantly impact the Company’s business or results of operations during the first quarter of 2020, the length and extent of the pandemic, its consequences, and containment efforts will determine the future impact on the Company’s operations and financial condition.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. S ummary of significant accounting policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2019, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 30, 2020. Since the date of those financial statements, there have been no changes to Beam’s significant accounting policies. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. Actual results could differ from these estimates. The COVID-19 pandemic may have an impact on the development timelines of the Company’s pre-clinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements. Cash, cash equivalents, and restricted cash Cash and cash equivalents consist of standard checking accounts, money market accounts, and all highly liquid investments with an original maturity of three months or less at the date of purchase. Restricted cash represents collateral provided for letters of credit issued as security deposits in connection with the Company’s leases of its corporate facilities. The following table reconciles cash, cash equivalents, and restricted cash reported within the Company’s condensed consolidated balance sheets to the total of the amounts shown in the condensed consolidated statement of cash flows (in thousands): March 31, 2020 March 31, 2019 Cash and cash equivalents $ 126,050 $ 156,138 Restricted cash 13,332 1,495 Total cash, cash equivalents, and restricted cash $ 139,382 $ 157,633 Recent accounting pronouncements In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements Revenue from Contracts with Customers

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Property and Equipment, Net	3. P roperty and equipment, net Property and equipment consist of the following (in thousands): March 31, 2020 December 31, 2019 Leasehold improvements $ 12,670 $ 12,653 Lab equipment 13,573 12,029 Furniture and fixtures 1,040 1,040 Computer equipment 547 547 Construction in process 2,236 2,185 Total property and equipment 30,066 28,454 Less accumulated depreciation (5,264 ) (4,164 ) Property and equipment, net $ 24,802 $ 24,290 Depreciation expense for the three months ended March 31, 2020 and 2019 was $1.1 million, and $0.7 million, respectively.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	4. f air Value of financial instruments The Company’s financial instruments that are measured at fair value on a recurring basis consist of cash equivalents, marketable securities, and success payment derivative liabilities pursuant to the license agreement between Harvard University, or Harvard, and the Company, or the Harvard License Agreement, and the license agreement between Broad Institute of MIT and Harvard, or Broad Institute, and Blink, or the Broad License Agreement. ASC 820, Fair Value Measurements and Disclosures • Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities. • Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, directly or indirectly, for substantially the full term of the asset or liability. • Level 3 – Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy at March 31, 2020 (in thousands): Carrying amount Fair value Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 70,322 $ 70,322 $ 70,322 $ — $ — Commercial paper 37,255 37,255 — 37,255 — Corporate notes 17,306 17,306 — 17,306 — Marketable securities: Commercial paper 72,971 72,971 — 72,971 — Corporate notes 54,421 54,421 — 54,421 — Total assets $ 252,275 $ 252,275 $ 70,322 $ 181,953 $ — Liabilities Success payment liability – Harvard $ 5,200 $ 5,200 $ — $ — $ 5,200 Success payment liability – Broad Institute 5,300 5,300 — — 5,300 Total liabilities $ 10,500 $ 10,500 $ — $ — $ 10,500 The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy at December 31, 2019 (in thousands): Carrying amount Fair value Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 6,172 $ 6,172 $ 6,172 $ — $ — Commercial paper 3,986 3,986 — 3,986 — Marketable securities: Commercial paper 36,889 36,889 — 36,889 — Corporate notes 17,738 17,738 — 17,738 — Total assets $ 64,785 $ 64,785 $ 6,172 $ 58,613 $ — Liabilities Success payment liability – Harvard $ 3,900 $ 3,900 $ — $ — $ 3,900 Success payment liability – Broad Institute 3,900 3,900 — — 3,900 Total liabilities $ 7,800 $ 7,800 $ — $ — $ 7,800 Cash equivalents – Money market funds included within cash equivalents are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in active markets. Commercial paper and corporate notes are classified within Level 2 of the fair value hierarchy because pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. Marketable securities – The Company measures its marketable securities at fair value on a recurring basis and classify those instruments within Level 2 of the fair value hierarchy. Marketable securities are classified within Level 2 of the fair value hierarchy because pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined using models or other valuation methodologies. Success Payment Liabilities – As discussed further in Note 8, License Agreements , the Company is required to make success payments determined based upon the achievement of specified multiples of the initial weighted average value of the Company’s Series A Preferred at specified valuation dates. The Company’s liability for success payments under the Harvard License Agreement and Broad License Agreement are carried at fair value. To determine the estimated fair value of the success payment liability, the Company uses a Monte Carlo simulation methodology, which models the future movement of stock prices based on several key variables. The following variables were incorporated in the calculation of the estimated fair value of the Harvard and Broad Institute success payment liabilities: Harvard Broad Institute March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Fair value of Series A Preferred (per share) (1) $ — $ 3.60 $ — $ 3.60 Fair value of common stock (per share) 18.00 — 18.00 — Expected volatility 73 % 72 % 73 % 72 % Expected term (years) 1.10-9.25 0.10-8.01 1.10-10.11 0.10-8.01 (1) The effect of the Company’s one-for-4.4843 reverse stock split in January 2020 only applied to its common stock and did not impact its redeemable convertible preferred stock. As such, the Series A Preferred fair value per share as of December 31, 2019 does not show the effect of the reverse stock split. If adjusted for the effect of the reverse stock split, the fair value per share of Series A Preferred would be $16.14 on December 31, 2019. Upon completion of the Company’s IPO, all outstanding shares of redeemable convertible preferred stock converted into shares of the Company’s common stock. At December 31, 2019, the fair value of the Series A Preferred was determined by management with the assistance of an independent third-party specialist. At March 31, 2020, the fair value of the common stock was the market value of the Company’s common stock. The computation of expected volatility was estimated using available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption. In addition, the Company incorporated the estimated number, timing, and probability of valuation measurement dates in the calculation of the success payment liability. The following table reconciles the change in the fair value of success payment liabilities based on Level 3 inputs (in thousands): Three Months Ended March 31, 2020 Harvard Broad Institute Total Balance at December 31, 2019 $ 3,900 $ 3,900 $ 7,800 Changes in fair value 1,300 1,400 2,700 Balance at March 31, 2020 $ 5,200 $ 5,300 $ 10,500

Marketable Securities

Marketable Securities	3 Months Ended
	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Marketable Securities	5. Marketable securities The following table summarizes the Company’s marketable securities held at March 31, 2020 (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 72,976 $ 9 $ (14 ) $ 72,971 Corporate notes 54,760 — (339 ) 54,421 Total $ 127,736 $ 9 $ (353 ) $ 127,392 The following table summarizes the Company’s marketable securities held at December 31, 2019 (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 36,875 $ 14 $ — $ 36,889 Corporate notes 17,736 2 — 17,738 Total $ 54,611 $ 16 $ — $ 54,627 The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. At March 31, 2020, the balance in accumulated other comprehensive (loss) income was comprised solely of activity related to marketable securities. There were no realized gains or losses recognized on the sale or maturity of marketable securities for the three months ended March 31, 2020 and 2019 and, as a result, the Company did not reclassify any amounts out of accumulated other comprehensive (loss) income for the same period. The Company held 26 debt securities in an unrealized loss position at March 31, 2020. The aggregate fair value of securities held by the Company in an unrealized loss position for less than 12 months at March 31, 2020 was $73.1 million, and there were no securities held by the Company in an unrealized loss position for more than 12 months. The Company holds debt securities of companies with high credit quality and has determined that there was no material change in the credit risk of any of its debt securities, and as of March 31, 2020 the Company did not intend to sell, and was more than likely not required to sell, the debt securities in a loss position before recovery of their amortized cost bases. As a result, the Company determined it did not hold any investments with any other-than-temporary impairment as of March 31, 2020. The contractual maturity date of all the investments are less than one year.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2020 December 31, 2019 Research costs (1) $ 4,285 $ 1,548 Employee compensation and related benefits 1,253 3,531 Professional fees 1,760 1,541 Other 1,182 1,232 Total $ 8,480 $ 7,852 (1) In March 2020, the Company determined that a patent under its license agreement with Bio Palette Co., Ltd., or Bio Palette, became probable of issuance and recognized $2.3 million of research and development expense during the three months ended March 31, 2020. Refer to Note 8, License Agreements

Leases

Leases	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Leases	7. Leases Operating leases The Company’s operating leases are as follow: • A February 2018 lease for 38,203 square feet of office and laboratory space, which commenced in March 2018 and terminates in September 2028. The lease is subject to fixed-rate rent escalations and provided for $6.1 million in tenant improvements and a term extension option, which was not probable of exercise. • An October 2018 lease for laboratory space, which commenced in April 2019 and was amended in March 2020. The amended lease commenced in March 2020 and terminates in March 2023. The amended lease is subject to fixed-rate rent escalations and provides an option to extend the lease for an additional year through March 31, 2024, which was determined by the Company to be reasonably certain of being exercised. Upon commencement, the Company recorded an operating lease right-of-use, or ROU, asset and a lease liability of $4.2 million. • Leases in June and July 2019 for office and laboratory space, both of which commenced in October 2019 and terminate in December 2021. The leases are subject to fixed-rate rent escalations. The following table summarizes operating lease costs as well as sublease income (in thousands): Three Months Ended March 31, 2020 2019 Operating lease costs $ 1,598 $ 708 Variable lease costs 288 159 Short-term lease costs — 50 Sublease income — (9 ) Total $ 1,886 $ 908 The following table summarizes the lease term and discount rate: March 31, 2020 December 31, 2019 Weighted-average remaining lease term (years) Operating leases 6.8 years 7.4 years Weighted-average discount rate Operating leases 9.7 % 9.8 % The following table summarizes the cash paid for amounts included in the measurement of lease liabilities (in thousands): Three Months Ended March 31, 2020 2019 Operating cash flows used for operating leases $ 1,525 $ 748 Operating lease liabilities arising from obtaining right-of-use assets 4,032 — At March 31, 2020, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Remainder of 2020 $ 5,487 2021 6,538 2022 4,777 2023 4,912 2024 3,808 2025 3,585 Thereafter 10,411 Undiscounted lease payments 39,518 Less: imputed interest (10,760 ) Total operating lease liabilities $ 28,758 In addition to the leases discussed above, the Company is party to an April 2019 lease for office and laboratory space to be built, with the lease for the first phase expected to commence at the earliest in late 2021 and the second phase expected to commence at the earliest in first half of 2023. The lease will terminate 12 years from the second phase commencement date. The lease is subject to fixed-rate rent escalations and provides for $23.4 million in tenant improvements and the option to extend the lease for two terms of 5 years each. Upon executing the lease, the Company made a security deposit of $11.8 million in the form of a letter of credit, which is included in restricted cash as of March 31, 2020. As the lease had not commenced, the Company has not recorded an operating lease ROU asset or lease liability for this lease in the accompanying condensed consolidated balance sheets. The minimum amount of anticipated undiscounted lease payments due under the MIT lease is $168.7 million. Further, the tabular disclosure of minimum lease payments above does not include payments due under this lease. Financing obligations In July 2019 and October 2019, the Company sold certain equipment to a leasing company. Contemporaneous with the closing of the sale, the Company entered into a lease agreement with the leasing company with a term of four years pursuant to which the Company leased back the equipment. Further, in February 2020, the Company sold additional equipment to the leasing company for a total of $1.6 million and, concurrently, entered into a lease agreement with the leasing company to lease back the equipment for an annual rent of $0.5 million over a term of four years. The equipment leases are being accounted for as financings as the lease terms are for substantially all the remaining economic life of the underlying equipment. Management concluded that control, including the significant risks and rewards of ownership, did not effectively transfer to the buyer-lessor at the inception of the sale and leaseback transactions. As a result, the transactions are accounted for as failed sale and leasebacks and result in the recognition of financing liabilities. The future minimum payments related to the equipment financing obligations at March 31, 2020, for each of the years ending December 31 were as follows (in thousands): Remainder of 2020 $ 1,651 2021 2,200 2022 2,200 2023 1,549 2024 70 Total 7,670 Less: amounts representing interest at 8.56% (1,212 ) Plus: residual values 535 Financing obligations $ 6,993 Total paydown of principal and interest expense related to the equipment financing obligations were $0.3 million and $0.1 million, respectively for the three months ended March 31, 2020.

License Agreements

License Agreements	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License Agreements	8. License agreements Harvard license agreement Under the terms of the Harvard License Agreement, Harvard is entitled to receive success payments, determined based upon the achievement of specified multiples of the initial weighted average value of the Company’s Series A Preferred at specified valuation dates. The Company is required to make success payments to Harvard during a period of time, or the Harvard Success Payment Period, which has been determined to be the later of (1) the ninth anniversary of the Harvard License Agreement or (2) the earlier of (a) the 12th anniversary of the Harvard License Agreement and (b) the third anniversary of the first date on which a licensed product receives regulatory approval in the United States. During the Harvard Success Payment Period, the Company will perform a valuation on each rolling 90-day period, commencing one year after the Company’s IPO. As of March 31, 2020 and December 31, 2019, the Company has recorded $5.2 million and $3.9 million, respectively, for the estimated fair value of the success fee derivative liability. During the three months ended March 31, 2020 and 2019, the Company recorded $1.3 million and $0.5 million, respectively, of other expense related to the remeasurement of the liability. As of March 31, 2020, no success payments were paid or due to Harvard. In addition, Harvard was entitled to receive financing milestone payments, which were paid by the Company during the three months ended March 31, 2019. The annual maintenance fee under the Harvard License Agreement is recorded as research and development expense. Patent prosecution costs are recognized as expense in the period incurred. As of March 31, 2020, the Company determined that product development and regulatory approval milestones and royalties under the Harvard License Agreement were not probable and, as such, no amounts were recognized for the three months ended March 31, 2020. Broad license agreement Under the terms of the Broad License Agreement, Broad Institute is entitled to receive success payments, determined based upon the achievement of specified multiples of the initial weighted average value of the Blink Series A Preferred at specified valuation dates. The Company is required to make success payments to Broad Institute during a period of time, or the Broad Success Payment Period, During the Broad Success Payment Period, the Company will perform a valuation . In addition, Broad Institute was entitled to receive financing milestone payments, which were paid by the Company during the year ended December 31, 2019. The annual maintenance fee under the Broad License Agreement is recorded as research and development expense. Patent prosecution costs are recognized as expense in the period incurred. As of March 31, 2020, the Company determined that product development and regulatory approval milestones and royalties under the Broad License Agreement were not probable and, as such, no amounts were recognized for the three months ended March 31, 2020. Editas license agreement In May 2018, the Company entered into a license agreement, or the Editas License Agreement, with Editas Medicine, Inc., or Editas, for certain intellectual property rights owned or controlled by Editas, for specified uses. Under the Editas License Agreement, Editas granted to the Company a worldwide, exclusive, sublicensable, license (subject to certain exceptions and conditions) under certain intellectual property controlled by Editas for the use of base editing therapies for the treatment of any field of human diseases and conditions, subject to certain exceptions, or the Beam Field, and the licenses granted or to be granted under the Editas License Agreement, or the Editas Development and Commercialization License). Additionally, Editas granted to the Company a royalty-free, non-exclusive license under certain intellectual property owned or controlled by Editas to perform research activities in the Beam Field. Editas provided the Company with an exclusive option to obtain an Editas Development and Commercialization License to three additional groups of intellectual property owned or controlled by Editas, on a group by group basis, during the specified option period, subject to certain exceptions. Pursuant to the Editas License Agreement, the Company will use commercially reasonable efforts to develop a product that includes the rights licensed to the Company within a specified period of time and to commercialize any such products that have received regulatory approval in certain specified countries. The annual maintenance fees under the Editas License Agreement are recorded as research and development expense. Annual patent costs are expensed as incurred. In addition, the Company is required to make certain development, regulatory and commercial milestone payments to Editas upon the achievement of specified milestones. The triggering of these milestone payments was not probable and, as such, no amounts were recognized for the three months ended March 31, 2020. Bio Palette In March 2019, the Company entered into a license agreement with Bio Palette pursuant to which Beam received an exclusive (even as to Bio Palette), sublicensable license under certain patent rights related to base editing owned or controlled by Bio Palette to exploit products for the treatment of human disease throughout the world, but excluding products in the microbiome field in Asia, or the Bio Palette License Agreement. In addition, the Company granted Bio Palette an exclusive (even as to Beam) license under certain patent rights related to base editing and gene editing owned or controlled by the Company to exploit products in the microbiome field in Asia. Each party to the agreement retains non-exclusive rights to develop and manufacture products in the microbiome field worldwide for the sole purpose of exploiting those products in its own territory. Each party agrees to certain coordination obligations in the microbiome field if either party determines not to exploit their rights in such field. Upon the execution of the Bio Palette License Agreement, the Company paid Bio Palette an upfront fee of $0.5 million and issued to Bio Palette 16,725 shares of its common stock valued at $0.1 million, which were recorded as research and development expense for the three months ended March 31, 2019. Upon the issuance of a certain Bio Palette patent in the United States, the Company will pay a milestone payment of $2.0 million and will issue to Bio Palette 39,025 shares of its common stock valued at $0.3 million. As of March 31, 2020, the Company determined that the patent was probable of issuance and has recognized $2.3 million as research and development expense for the three months ended March 31, 2020.

Collaboration and License Agree

Collaboration and License Agreements	3 Months Ended
	Mar. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	9. Collaboration and license agreements Prime Medicine In September 2019, the Company entered into a Collaboration and License Agreement with Prime Medicine, Inc., or Prime Medicine, to research and develop a novel gene editing technology developed by one of Beam’s founders. Under the terms of the agreement, the Company granted Prime Medicine a non-exclusive license to certain of its CRISPR technology (including Cas12b), delivery technology and certain other technology controlled by Beam to develop and commercialize gene editing products for the treatment of human diseases. The Company is not currently using the intellectual property licensed from Prime Medicine in any of its current programs, but it is required to use commercially reasonable effort to develop new product candidates using the intellectual property licensed from Prime Medicine. Additionally, each party granted to the other party certain exclusive and non-exclusive licenses to certain technology developed after the effective date of the agreement and controlled by the granting party or jointly owned by the parties. Each party has an obligation to assign rights in certain technology developed under the collaboration to the other party. As of March 31, 2020, the Company determined that milestones and royalties under the agreement were not probable of recognition. Verve In April 2019, Beam entered into a Collaboration and License Agreement with Verve Therapeutics, Inc., or Verve, to investigate gene editing strategies to modify genes associated with an increased risk of coronary diseases. Under the terms of the agreement, the Company granted Verve an exclusive license to certain base editor technology and certain delivery technology, and improvements and Verve granted Beam a non-exclusive license under certain know-how and patents controlled by Verve, an interest in joint collaboration technology and an exclusive license (except as to Verve) under certain delivery technology. As of March 31, 2020, the Company determined that milestones and royalties under the agreement were not probable of recognition.

Preferred and Common Stock

Preferred and Common Stock	3 Months Ended
	Mar. 31, 2020
Stockholders Equity [Abstract]
Preferred and Common Stock	10. Preferred and common stock During the three months ended March 31, 2020, the Company authorized preferred stock issuable of 25,000,000 shares and increased its authorized common stock issuable to 250,000,000 shares, both with a $0.01 par value per share. The Company’s board of directors approved a one-for-4.4843 reverse stock split of its common stock and stock options and a proportional adjustment to the existing conversion ratios for the Company’s redeemable convertible preferred stock effective as of January 24, 2020. Accordingly, all common stock shares, per share amounts, and additional paid-in capital amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse stock split. In February 2020, the Company completed its IPO in which the Company issued and sold 12,176,471 shares of its common stock, including 1,588,235 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $17.00 per share, for aggregate gross proceeds of $207.0 million. The Company received approximately $188.3 million in net proceeds after deducting underwriting discounts and estimated offering expenses payable by the Company. In connection with the IPO, all outstanding shares of Preferred Stock converted into 29,127,523 shares of the Company’s common stock.

Stock Option and Grant Plan

Stock Option and Grant Plan	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option and Grant Plan	11. Stock option and grant plan Stock option and grant plan The 2017 Stock Option and Grant Plan adopted by the board of directors in June 2017 and amended in February and May 2019, provides for the grant of qualified incentive stock options and nonqualified stock options, restricted stock or other awards to the Company’s employees, officers, directors, advisors, and outside consultants for the issuance or purchase of shares of the Company’s common stock. In February 2020, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Equity Incentive Plan, or the 2019 Plan, and, subsequent to the IPO, all equity-based awards will be granted under the 2019 Plan. The 2019 Plan provides for grant of qualified and nonqualified stock options, stock appreciation rights, restricted and unrestricted stock and stock units, performance awards, and other share-based awards to the Company’s employees, officers, directors, advisors, and outside consultants. As of March 31, 2020, the Company had 8,431,743 shares reserved and 2,768,145 shares available for future issuance under the 2019 Plan. Stock-based compensation expense recorded as research and development and general and administrative expenses in the condensed consolidated statements of operations and other comprehensive loss is as follows (in thousands): Three Months Ended March 31, 2020 2019 Research and development $ 1,773 $ 507 General and administrative 1,019 362 Total stock-based compensation expense $ 2,792 $ 869 Stock options A summary of option activity under the Company’s equity award plans: Number of options Weighted average exercise price Outstanding at December 31, 2019 4,791,047 $ 4.72 Granted 949,640 17.15 Exercised (59,305 ) 2.56 Forfeitures (17,784 ) 8.56 Outstanding at March 31, 2020 5,663,598 6.72 Exercisable as of March 31, 2020 1,097,819 1.66 The weighted-average grant date fair value per share of options granted in the three months ended March 31, 2020 was $12.06. As of March 31, 2020, there was $24.8 million of unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.66 years. Restricted stock The following summarizes the Company’s restricted stock activity: Shares Weighted- average grant date fair value Unvested as of December 31, 2019 2,655,806 $ 2.73 Issued — — Vested (387,866 ) 2.25 Unvested as of March 31, 2020 2,267,940 $ 2.81 At March 31, 2020, there was approximately $6.4 million of unrecognized stock-based compensation expense related to restricted stock that is expected to vest. These costs are expected to be recognized over a weighted-average remaining vesting period of 1.6 years.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	12. Net loss per share attributable to common stockholders As noted above, for periods in which the Company reports a net loss attributable to common stockholders, potentially dilutive securities have been excluded from the computation of diluted net loss per share as their effects would be anti-dilutive. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect: Three Months Ended March 31, 2020 2019 Redeemable convertible preferred stock — 29,127,543 Unvested restricted stock 2,267,940 3,826,370 Outstanding options to purchase common stock 5,663,598 3,165,049 Total 7,931,538 36,118,962 The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts): Three Months Ended March 31, 2020 2019 Numerator: Net loss attributable to common stockholders $ (31,735 ) $ (16,573 ) Denominator: Weighted average number of common shares, basic and diluted 30,725,077 5,795,481 Net loss per common share attributable to common stockholders, basic and diluted $ (1.03 ) $ (2.86 )

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	13. Income taxes During the three months ended March 31, 2020 and 2019, the Company recorded a full valuation allowance on federal and state deferred tax assets since management does not forecast the Company to be in a taxable position in the near future.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	14. Related party transactions For the three months ended March 31, 2020 and 2019, the Company made payments of $0.1 million and $0.1 million, respectively, to its three founder shareholders for scientific consulting and other expenses. The Company has entered into collaboration and license agreements with Prime Medicine and Verve. The Company and Prime Medicine have a common founder and several common board members. The Company and Verve have a common board member. During the three months ended March 31, 2020 and 2019, the Company purchased shares of Verve series A preferred stock valued at $0.8 million and $0.4 million, respectively.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	15. S ubsequent events The Company evaluated all subsequent events through May 12, 2020, the date that these condensed consolidated financial statements were issued to determine if such events should be reflected in these condensed consolidated financial statements. Lease amendment In April 2020, the Company entered into a third amendment of its March 2020 amended lease agreement for laboratory space in Cambridge, Massachusetts. The amended lease commenced in April 2020 and will expire on December 31, 2025. The lease provides an option to extend the lease for two additional two-year periods through December 31, 2029, which were not determined by the Company to be reasonably certain of being exercised. As the commencement date of the leases has not occurred at March 31, 2020, no operating lease ROU asset or lease liability has been recorded in the accompanying condensed consolidated balance sheets for this amendment. The incremental increase in total amount of undiscounted lease payments as a result of the amended lease is approximately $1.1 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Use of Estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis. Actual results could differ from these estimates. The COVID-19 pandemic may have an impact on the development timelines of the Company’s pre-clinical programs. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgment. As of the date of issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgments or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements.
Cash, Cash Equivalents, and Restricted Cash	Cash, cash equivalents, and restricted cash Cash and cash equivalents consist of standard checking accounts, money market accounts, and all highly liquid investments with an original maturity of three months or less at the date of purchase. Restricted cash represents collateral provided for letters of credit issued as security deposits in connection with the Company’s leases of its corporate facilities. The following table reconciles cash, cash equivalents, and restricted cash reported within the Company’s condensed consolidated balance sheets to the total of the amounts shown in the condensed consolidated statement of cash flows (in thousands): March 31, 2020 March 31, 2019 Cash and cash equivalents $ 126,050 $ 156,138 Restricted cash 13,332 1,495 Total cash, cash equivalents, and restricted cash $ 139,382 $ 157,633
Recent Accounting Pronouncements	Recent accounting pronouncements In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements Revenue from Contracts with Customers

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents, and Restricted Cash	The following table reconciles cash, cash equivalents, and restricted cash reported within the Company’s condensed consolidated balance sheets to the total of the amounts shown in the condensed consolidated statement of cash flows (in thousands): March 31, 2020 March 31, 2019 Cash and cash equivalents $ 126,050 $ 156,138 Restricted cash 13,332 1,495 Total cash, cash equivalents, and restricted cash $ 139,382 $ 157,633

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): March 31, 2020 December 31, 2019 Leasehold improvements $ 12,670 $ 12,653 Lab equipment 13,573 12,029 Furniture and fixtures 1,040 1,040 Computer equipment 547 547 Construction in process 2,236 2,185 Total property and equipment 30,066 28,454 Less accumulated depreciation (5,264 ) (4,164 ) Property and equipment, net $ 24,802 $ 24,290

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Assets and Liabilities	The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy at March 31, 2020 (in thousands): Carrying amount Fair value Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 70,322 $ 70,322 $ 70,322 $ — $ — Commercial paper 37,255 37,255 — 37,255 — Corporate notes 17,306 17,306 — 17,306 — Marketable securities: Commercial paper 72,971 72,971 — 72,971 — Corporate notes 54,421 54,421 — 54,421 — Total assets $ 252,275 $ 252,275 $ 70,322 $ 181,953 $ — Liabilities Success payment liability – Harvard $ 5,200 $ 5,200 $ — $ — $ 5,200 Success payment liability – Broad Institute 5,300 5,300 — — 5,300 Total liabilities $ 10,500 $ 10,500 $ — $ — $ 10,500 The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy at December 31, 2019 (in thousands): Carrying amount Fair value Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 6,172 $ 6,172 $ 6,172 $ — $ — Commercial paper 3,986 3,986 — 3,986 — Marketable securities: Commercial paper 36,889 36,889 — 36,889 — Corporate notes 17,738 17,738 — 17,738 — Total assets $ 64,785 $ 64,785 $ 6,172 $ 58,613 $ — Liabilities Success payment liability – Harvard $ 3,900 $ 3,900 $ — $ — $ 3,900 Success payment liability – Broad Institute 3,900 3,900 — — 3,900 Total liabilities $ 7,800 $ 7,800 $ — $ — $ 7,800
Schedule of Calculation of Estimated Fair Value of Success Payment Liabilities	The following variables were incorporated in the calculation of the estimated fair value of the Harvard and Broad Institute success payment liabilities: Harvard Broad Institute March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Fair value of Series A Preferred (per share) (1) $ — $ 3.60 $ — $ 3.60 Fair value of common stock (per share) 18.00 — 18.00 — Expected volatility 73 % 72 % 73 % 72 % Expected term (years) 1.10-9.25 0.10-8.01 1.10-10.11 0.10-8.01 (1) The effect of the Company’s one-for-4.4843 reverse stock split in January 2020 only applied to its common stock and did not impact its redeemable convertible preferred stock. As such, the Series A Preferred fair value per share as of December 31, 2019 does not show the effect of the reverse stock split. If adjusted for the effect of the reverse stock split, the fair value per share of Series A Preferred would be $16.14 on December 31, 2019. Upon completion of the Company’s IPO, all outstanding shares of redeemable convertible preferred stock converted into shares of the Company’s common stock.
Schedule of Change in Fair Value of Success Payment Liabilities Based on Level 3 Inputs	The following table reconciles the change in the fair value of success payment liabilities based on Level 3 inputs (in thousands): Three Months Ended March 31, 2020 Harvard Broad Institute Total Balance at December 31, 2019 $ 3,900 $ 3,900 $ 7,800 Changes in fair value 1,300 1,400 2,700 Balance at March 31, 2020 $ 5,200 $ 5,300 $ 10,500

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2020
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities Held	The following table summarizes the Company’s marketable securities held at March 31, 2020 (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 72,976 $ 9 $ (14 ) $ 72,971 Corporate notes 54,760 — (339 ) 54,421 Total $ 127,736 $ 9 $ (353 ) $ 127,392 The following table summarizes the Company’s marketable securities held at December 31, 2019 (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Commercial paper $ 36,875 $ 14 $ — $ 36,889 Corporate notes 17,736 2 — 17,738 Total $ 54,611 $ 16 $ — $ 54,627

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): March 31, 2020 December 31, 2019 Research costs (1) $ 4,285 $ 1,548 Employee compensation and related benefits 1,253 3,531 Professional fees 1,760 1,541 Other 1,182 1,232 Total $ 8,480 $ 7,852 (1) In March 2020, the Company determined that a patent under its license agreement with Bio Palette Co., Ltd., or Bio Palette, became probable of issuance and recognized $2.3 million of research and development expense during the three months ended March 31, 2020. Refer to Note 8, License Agreements

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2020
Leases [Abstract]
Summary of Operating Lease Costs	The following table summarizes operating lease costs as well as sublease income (in thousands): Three Months Ended March 31, 2020 2019 Operating lease costs $ 1,598 $ 708 Variable lease costs 288 159 Short-term lease costs — 50 Sublease income — (9 ) Total $ 1,886 $ 908
Summary of Lease Term and Discount Rate	The following table summarizes the lease term and discount rate: March 31, 2020 December 31, 2019 Weighted-average remaining lease term (years) Operating leases 6.8 years 7.4 years Weighted-average discount rate Operating leases 9.7 % 9.8 %
Summary of Cash Paid for Amounts Included in Measurement of Lease Liabilities	The following table summarizes the cash paid for amounts included in the measurement of lease liabilities (in thousands): Three Months Ended March 31, 2020 2019 Operating cash flows used for operating leases $ 1,525 $ 748 Operating lease liabilities arising from obtaining right-of-use assets 4,032 —
Summary of Future Minimum Lease Payments of Operating Leases	At March 31, 2020, the future minimum lease payments for the Company’s operating leases for each of the years ending December 31 were as follows (in thousands): Remainder of 2020 $ 5,487 2021 6,538 2022 4,777 2023 4,912 2024 3,808 2025 3,585 Thereafter 10,411 Undiscounted lease payments 39,518 Less: imputed interest (10,760 ) Total operating lease liabilities $ 28,758
Summary of Future Minimum Payments Related to Equipment Financing Obligations	The future minimum payments related to the equipment financing obligations at March 31, 2020, for each of the years ending December 31 were as follows (in thousands): Remainder of 2020 $ 1,651 2021 2,200 2022 2,200 2023 1,549 2024 70 Total 7,670 Less: amounts representing interest at 8.56% (1,212 ) Plus: residual values 535 Financing obligations $ 6,993

Stock Option and Grant Plan (Ta

Stock Option and Grant Plan (Tables)	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-based Compensation Expense	Stock-based compensation expense recorded as research and development and general and administrative expenses in the condensed consolidated statements of operations and other comprehensive loss is as follows (in thousands): Three Months Ended March 31, 2020 2019 Research and development $ 1,773 $ 507 General and administrative 1,019 362 Total stock-based compensation expense $ 2,792 $ 869
Summary of Option Activity Under Equity Award Plans	A summary of option activity under the Company’s equity award plans: Number of options Weighted average exercise price Outstanding at December 31, 2019 4,791,047 $ 4.72 Granted 949,640 17.15 Exercised (59,305 ) 2.56 Forfeitures (17,784 ) 8.56 Outstanding at March 31, 2020 5,663,598 6.72 Exercisable as of March 31, 2020 1,097,819 1.66
Summary of Restricted Stock Activity	The following summarizes the Company’s restricted stock activity: Shares Weighted- average grant date fair value Unvested as of December 31, 2019 2,655,806 $ 2.73 Issued — — Vested (387,866 ) 2.25 Unvested as of March 31, 2020 2,267,940 $ 2.81

Net Loss per Share Attributab_2

Net Loss per Share Attributable to Common Stockholders (Tables)	3 Months Ended
	Mar. 31, 2020
Earnings Per Share [Abstract]
Schedule of Potential Common Shares Excluded from Computation of Diluted Net Loss per Share	The Company excluded the following potential common shares, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect: Three Months Ended March 31, 2020 2019 Redeemable convertible preferred stock — 29,127,543 Unvested restricted stock 2,267,940 3,826,370 Outstanding options to purchase common stock 5,663,598 3,165,049 Total 7,931,538 36,118,962
Summary of Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts): Three Months Ended March 31, 2020 2019 Numerator: Net loss attributable to common stockholders $ (31,735 ) $ (16,573 ) Denominator: Weighted average number of common shares, basic and diluted 30,725,077 5,795,481 Net loss per common share attributable to common stockholders, basic and diluted $ (1.03 ) $ (2.86 )

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) $ / shares in Units, $ in Thousands	Jan. 24, 2020	Feb. 29, 2020USD ($)$ / sharesshares	Jan. 31, 2020	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Nature Of Business And Basis Of Presentation [Line Items]
Reverse stock split ratio	0.223		4.4843
Reverse stock split				one-for-4.4843
Gross proceeds from sale of common stock				$ 192,510
Accumulated deficit				233,502	$ 203,044
Cash, cash equivalents, and marketable securities				$ 253,400
IPO
Nature Of Business And Basis Of Presentation [Line Items]
Shares issued and sold | shares		12,176,471
Public offering price per share | $ / shares		$ 17
Gross proceeds from sale of common stock		$ 207,000
Net proceeds from sale of common stock		$ 188,300
Shares issued upon conversion of preferred stock | shares		29,127,523
Underwriters’ Option
Nature Of Business And Basis Of Presentation [Line Items]
Shares issued and sold | shares		1,588,235

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 126,050	$ 37,221	$ 156,138
Restricted cash	13,332	13,332	1,495
Total cash, cash equivalents, and restricted cash	$ 139,382	$ 50,553	$ 157,633	$ 147,936

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 30,066	$ 28,454
Less accumulated depreciation	(5,264)	(4,164)
Property and equipment, net	24,802	24,290
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	12,670	12,653
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	13,573	12,029
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,040	1,040
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	547	547
Construction in Process
Property Plant And Equipment [Line Items]
Total property and equipment	$ 2,236	$ 2,185

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information - (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation expense	$ 1,100	$ 735

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Harvard
Liabilities
Success payment liability	$ 5,200	$ 3,900
Broad Institute
Liabilities
Success payment liability	5,300	3,900
Recurring | Carrying Amount
Assets
Total assets	252,275	64,785
Liabilities
Total liabilities	10,500	7,800
Recurring | Carrying Amount | Money Market Funds
Assets
Cash equivalents	70,322	6,172
Recurring | Carrying Amount | Commercial Paper
Assets
Cash equivalents	37,255	3,986
Marketable securities	72,971	36,889
Recurring | Carrying Amount | Corporate Notes
Assets
Cash equivalents	17,306
Marketable securities	54,421	17,738
Recurring | Fair Value
Assets
Total assets	252,275	64,785
Liabilities
Total liabilities	10,500	7,800
Recurring | Fair Value | Level 1
Assets
Total assets	70,322	6,172
Recurring | Fair Value | Level 2
Assets
Total assets	181,953	58,613
Recurring | Fair Value | Level 3
Liabilities
Total liabilities	10,500	7,800
Recurring | Fair Value | Money Market Funds
Assets
Cash equivalents	70,322	6,172
Recurring | Fair Value | Money Market Funds | Level 1
Assets
Cash equivalents	70,322	6,172
Recurring | Fair Value | Commercial Paper
Assets
Cash equivalents	37,255	3,986
Marketable securities	72,971	36,889
Recurring | Fair Value | Commercial Paper | Level 2
Assets
Cash equivalents	37,255	3,986
Marketable securities	72,971	36,889
Recurring | Fair Value | Corporate Notes
Assets
Cash equivalents	17,306
Marketable securities	54,421	17,738
Recurring | Fair Value | Corporate Notes | Level 2
Assets
Cash equivalents	17,306
Marketable securities	54,421	17,738
Recurring | Harvard | Carrying Amount
Liabilities
Success payment liability	5,200	3,900
Recurring | Harvard | Fair Value
Liabilities
Success payment liability	5,200	3,900
Recurring | Harvard | Fair Value | Level 3
Liabilities
Success payment liability	5,200	3,900
Recurring | Broad Institute | Carrying Amount
Liabilities
Success payment liability	5,300	3,900
Recurring | Broad Institute | Fair Value
Liabilities
Success payment liability	5,300	3,900
Recurring | Broad Institute | Fair Value | Level 3
Liabilities
Success payment liability	$ 5,300	$ 3,900

Fair Value of Financial Instr_4

Fair Value of Financial Instruments -Schedule of Calculation of Estimated Fair Value of Success Payment Liabilities (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Fair Value of Series A Preferred Stock | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input		3.60
Fair Value of Series A Preferred Stock | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input		3.60
Fair Value of Common Stock | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	18
Fair Value of Common Stock | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	18
Expected Volatility | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	73	72
Expected Volatility | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, measurement input	73	72
Expected Term (years) | Harvard | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	1 year 1 month 6 days	1 month 6 days
Expected Term (years) | Harvard | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	9 years 3 months	8 years 3 days
Expected Term (years) | Broad Institute | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	1 year 1 month 6 days	1 month 6 days
Expected Term (years) | Broad Institute | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	10 years 1 month 9 days	8 years 3 days

Fair Value of Financial Instr_5

Fair Value of Financial Instruments -Schedule of Calculation of Estimated Fair Value of Success Payment Liabilities (Parenthetical) (Details)	Jan. 24, 2020	Jan. 31, 2020	Dec. 31, 2019$ / shares
Fair Value Disclosures [Abstract]
Reverse stock split ratio	0.223	4.4843
Fair value of preferred stock price per share after adjusted reverse stock split			$ 16.14

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Schedule of Change in Fair Value of Success Payment Liabilities Based on Level 3 Inputs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2019	$ 7,800
Changes in fair value	2,700
Balance at March 31, 2020	10,500
Harvard
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2019	3,900
Changes in fair value	1,300
Balance at March 31, 2020	5,200
Broad Institute
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at December 31, 2019	3,900
Changes in fair value	1,400
Balance at March 31, 2020	$ 5,300

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities Held (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Held To Maturity Securities [Line Items]
Marketable securities held, Amortized Cost	$ 127,736	$ 54,611
Marketable securities held, Gross Unrealized Gains	9	16
Marketable securities held, Gross Unrealized Losses	(353)
Marketable securities held, Fair Value	127,392	54,627
Commercial Paper
Schedule Of Held To Maturity Securities [Line Items]
Marketable securities held, Amortized Cost	72,976	36,875
Marketable securities held, Gross Unrealized Gains	9	14
Marketable securities held, Gross Unrealized Losses	(14)
Marketable securities held, Fair Value	72,971	36,889
Corporate Notes
Schedule Of Held To Maturity Securities [Line Items]
Marketable securities held, Amortized Cost	54,760	17,736
Marketable securities held, Gross Unrealized Gains		2
Marketable securities held, Gross Unrealized Losses	(339)
Marketable securities held, Fair Value	$ 54,421	$ 17,738

Marketable Securities - Additio

Marketable Securities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020USD ($)Security	Mar. 31, 2019USD ($)
Investments Debt And Equity Securities [Abstract]
Realized gains or losses recognized on sale or maturity of marketable securities	$ 0	$ 0
Number of unrealized loss position held in debt securities | Security	26
Fair value of securities held unrealized loss position for less than 12 months	$ 73,100,000
Debt securities held by unrealized loss position for more than 12 months	$ 0

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Research costs	$ 4,285	$ 1,548
Employee compensation and related benefits	1,253	3,531
Professional fees	1,760	1,541
Other	1,182	1,232
Total	$ 8,480	$ 7,852

Accrued Expenses and Other Cu_4

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Parenthetical) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expenses	$ 21,549	$ 9,179
Bio Palette License Agreement | Bio Palette Patent
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expenses	$ 2,300

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	1 Months Ended			2 Months Ended	3 Months Ended
	Feb. 29, 2020USD ($)	Oct. 31, 2018	Feb. 28, 2018USD ($)ft²	Jul. 31, 2019	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 31, 2019	Apr. 01, 2019USD ($)
Lessee Lease Description [Line Items]
Operating lease right-of-use asset					$ 22,126	$ 18,957
Lease liability					$ 28,758
Lessee, operating lease, lease not yet commenced, description					Lease for the first phase expected to commence at the earliest in late 2021 and the second phase expected to commence at the earliest in first half of 2023.
Lessee, operating lease, lease not yet commenced, existence of option to terminate					true
Lessee, operating lease, lease not yet commenced, expiration term					12 years
Lessee, operating lease, lease not yet commenced tenant improvement					$ 23,400
Lessee, operating lease, lease not yet commenced, existence of option to extend					true
Lessee, operating lease, lease not yet commenced, option to extend					Option to extend the lease for two terms of 5 years each.
Lessee, operating lease, lease not yet commenced, security deposit					$ 11,800
Lessee, operating lease, lease not yet commenced anticipated undiscounted lease payments due					$ 168,700
Office and Laboratory Space
Lessee Lease Description [Line Items]
Square feet of office and laboratory space | ft²			38,203
Operating lease, commencement month and year			2018-03	2019-10
Operating lease, termination month and year			2028-09	2021-12
Tenant improvements			$ 6,100
Laboratory Space
Lessee Lease Description [Line Items]
Operating lease, commencement month and year		2019-04
Operating lease, termination month and year		2023-03
Operating lease, amendment month and year		2020-03
Operating lease, option to extend					The amended lease is subject to fixed-rate rent escalations and provides an option to extend the lease for an additional year through March 31, 2024, which was determined by the Company to be reasonably certain of being exercised.
Operating lease, existence of option to extend		true
Operating lease right-of-use asset								$ 4,200
Lease liability								$ 4,200
Equipment
Lessee Lease Description [Line Items]
Financing obligations, leased back description					In July 2019 and October 2019, the Company sold certain equipment to a leasing company. Contemporaneous with the closing of the sale, the Company entered into a lease agreement with the leasing company with a term of four years pursuant to which the Company leased back the equipment.
Financing obligations, leased back equipment term of contract	4 years						4 years
Financing obligations, additional equipment sold	$ 1,600
Financing obligations, lease back equipment annual rent	$ 500
Paydown of principal					$ 300
Interest expense					$ 100

Leases - Summary of Operating L

Leases - Summary of Operating Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Operating lease costs	$ 1,598	$ 708
Variable lease costs	288	159
Short-term lease costs		50
Sublease income		(9)
Total	$ 1,886	$ 908

Leases - Summary of Lease Term

Leases - Summary of Lease Term and Discount Rate (Details)	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating leases, Weighted-average remaining lease term (years)	6 years 9 months 18 days	7 years 4 months 24 days
Operating leases, Weighted-average discount rate	9.70%	9.80%

Leases - Summary of Cash Paid f

Leases - Summary of Cash Paid for Amounts Included in Measurement of Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Operating cash flows used for operating leases	$ 1,525	$ 748
Operating lease liabilities arising from obtaining right-of-use assets	$ 4,032

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments of Operating Leases (Details) $ in Thousands	Mar. 31, 2020USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2020	$ 5,487
2021	6,538
2022	4,777
2023	4,912
2024	3,808
2025	3,585
Thereafter	10,411
Undiscounted lease payments	39,518
Less: imputed interest	(10,760)
Total operating lease liabilities	$ 28,758

Leases - Summary of Future Mi_2

Leases - Summary of Future Minimum Payments Related to Equipment Financing Obligations (Details) - Equipment $ in Thousands	Mar. 31, 2020USD ($)
Finance Lease Liability Payments [Line Items]
Remainder of 2020	$ 1,651
2021	2,200
2022	2,200
2023	1,549
2024	70
Total	7,670
Less: amounts representing interest at 8.56%	(1,212)
Plus: residual values	535
Financing obligations	$ 6,993

Leases - Summary of Future Mi_3

Leases - Summary of Future Minimum Payments Related to Equipment Financing Obligations (Parenthetical) (Details)	Mar. 31, 2020
Equipment
Finance Lease Liability Payments [Line Items]
Finance lease liability payments interest percentage	8.56%

License Agreements - Harvard Li

License Agreements - Harvard License Agreement - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expenses from remeasurement of derivative liability	$ (2,700,000)	$ (1,000,000)
Harvard
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement description	The Company is required to make success payments to Harvard during a period of time, or the Harvard Success Payment Period, which has been determined to be the later of (1) the ninth anniversary of the Harvard License Agreement or (2) the earlier of (a) the 12th anniversary of the Harvard License Agreement and (b) the third anniversary of the first date on which a licensed product receives regulatory approval in the United States. During the Harvard Success Payment Period, the Company will perform a valuation on each rolling 90-day period, commencing one year after the Company’s IPO.
Fair value of success fee derivative liability	$ 5,200,000		$ 3,900,000
Expenses from remeasurement of derivative liability	1,300,000	$ 500,000
Success payments paid or due	0
Product development, regulatory approval milestones and royalties recognized	$ 0

License Agreements - Broad Lice

License Agreements - Broad License Agreement - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expenses from remeasurement of derivative liability	$ (2,700,000)	$ (1,000,000)
Broad License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement description	The Company is required to make success payments to Broad Institute during a period of time, or the Broad Success Payment Period, which has been determined to be the earliest of (1) the twelfth anniversary of the Broad License Agreement, or (2) the third anniversary of the first date on which a licensed product receives regulatory approval in the United States. During the Broad Success Payment Period, the Company will perform a valuation on each rolling 90-day period, commencing one year after the Company’s IPO.
Fair value of success fee derivative liability	$ 5,300,000		$ 3,900,000
Expenses from remeasurement of derivative liability	1,400,000	$ 500,000
Success payments paid or due	0
Product development, regulatory approval milestones and royalties recognized	$ 0

License Agreements - Editas Lic

License Agreements - Editas License Agreement - Additional Information (Details)	3 Months Ended
	Mar. 31, 2020USD ($)
Editas License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development, regulatory and commercial milestone payments	$ 0

License Agreements - Bio Palett

License Agreements - Bio Palette - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment shares issued		51,345,290		9,981,991
Milestone payment value of stock issued		$ 491		$ 73
Research and development expenses		$ 21,549	$ 9,179
Bio Palette License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee paid	$ 500
Milestone payment shares issued		16,725
Milestone payment value of stock issued		$ 100
Bio Palette License Agreement | Bio Palette Patent
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment shares issued		39,025
Milestone payment value of stock issued		$ 300
Milestone payment paid		2,000
Research and development expenses		$ 2,300

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Details) $ / shares in Units, $ in Thousands	Jan. 24, 2020	Feb. 29, 2020USD ($)$ / sharesshares	Jan. 31, 2020	Mar. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019$ / sharesshares
Class Of Stock [Line Items]
Preferred stock, shares authorized				25,000,000	0
Preferred stock, par value per share | $ / shares				$ 0.01	$ 0.01
Common stock, shares authorized				250,000,000	205,000,000
Common stock, par value per share | $ / shares				$ 0.01	$ 0.01
Reverse stock split ratio	0.223		4.4843
Reverse stock split				one-for-4.4843
Gross proceeds from sale of common stock | $				$ 192,510
IPO
Class Of Stock [Line Items]
Shares issued and sold		12,176,471
Public offering price per share | $ / shares		$ 17
Gross proceeds from sale of common stock | $		$ 207,000
Net proceeds from sale of common stock | $		$ 188,300
Shares issued upon conversion of preferred stock		29,127,523
Underwriters’ Option
Class Of Stock [Line Items]
Shares issued and sold		1,588,235

Stock Option and Grant Plan - A

Stock Option and Grant Plan - Additional Information (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value per share of options granted | $ / shares	$ 12.06
Unrecognized compensation cost related to unvested stock options | $	$ 24.8
Unvested Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, expected to recognize over a weighted-average period	2 years 7 months 28 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, expected to recognize over a weighted-average period	1 year 7 months 6 days
Unrecognized stock-based compensation expense, expected to vest | $	$ 6.4
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for future issuance | shares	8,431,743
Number of shares available for future issuance | shares	2,768,145

Stock Option and Grant Plan - S

Stock Option and Grant Plan - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,792	$ 869
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,773	507
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,019	$ 362

Stock Option and Grant Plan -_2

Stock Option and Grant Plan - Summary of Option Activity Under Equity Award Plans (Details)	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Number of options
Outstanding at December 31, 2019 | shares	4,791,047
Granted | shares	949,640
Exercised | shares	(59,305)
Forfeitures | shares	(17,784)
Outstanding at March 31, 2020 | shares	5,663,598
Exercisable as of March 31, 2020 | shares	1,097,819
Weighted average exercise price
Outstanding at December 31, 2019 | $ / shares	$ 4.72
Granted | $ / shares	17.15
Exercised | $ / shares	2.56
Forfeitures | $ / shares	8.56
Outstanding at March 31, 2020 | $ / shares	6.72
Exercisable as of March 31, 2020 | $ / shares	$ 1.66

Stock Option and Grant Plan -_3

Stock Option and Grant Plan - Summary of Restricted Stock Activity (Details) - Restricted Stock	3 Months Ended
	Mar. 31, 2020$ / sharesshares
Shares
Unvested as of December 31, 2019 | shares	2,655,806
Vested | shares	(387,866)
Unvested as of March 31, 2020 | shares	2,267,940
Weighted-average grant date fair value
Unvested as of December 31, 2019 | $ / shares	$ 2.73
Vested | $ / shares	2.25
Unvested as of March 31, 2020 | $ / shares	$ 2.81

Net Loss per Share Attributab_3

Net Loss per Share Attributable to Common Stockholders - Schedule of Potential Common Shares Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share	7,931,538	36,118,962
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share		29,127,543
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share	2,267,940	3,826,370
Unvested Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share	5,663,598	3,165,049

Net Loss per Share Attributab_4

Net Loss per Share Attributable to Common Stockholders - Summary of Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (31,735)	$ (16,573)
Denominator:
Weighted average number of common shares, basic and diluted	30,725,077	5,795,481
Net loss per common share attributable to common stockholders, basic and diluted	$ (1.03)	$ (2.86)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)Founder	Mar. 31, 2019USD ($)
Related Party Transaction [Line Items]
Number of founder shareholders | Founder	3
Founder Shareholders | Scientific Consulting and Other Expenses
Related Party Transaction [Line Items]
Payments made to related parties	$ 0.1	$ 0.1
Verve Therapeutics, Inc. | Series A Preferred Stock Shares
Related Party Transaction [Line Items]
Purchased shares from related party	$ 0.8	$ 0.4

Subsequent Events - Additional

Subsequent Events - Additional Information (Details)	1 Months Ended		3 Months Ended
	Apr. 30, 2020USD ($)Option	Oct. 31, 2018	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Apr. 01, 2019USD ($)
Subsequent Event [Line Items]
Operating lease, right-of-use asset			$ 22,126,000	$ 18,957,000
Operating lease, liability			28,758,000
Operating lease, undiscounted lease payments			$ 10,760,000
Laboratory Space
Subsequent Event [Line Items]
Operating lease, commencement month and year		2019-04
Operating lease, option to extend			The amended lease is subject to fixed-rate rent escalations and provides an option to extend the lease for an additional year through March 31, 2024, which was determined by the Company to be reasonably certain of being exercised.
Operating lease, existence of option to extend		true
Operating lease, right-of-use asset					$ 4,200,000
Operating lease, liability					$ 4,200,000
Laboratory Space | March 2020 Amended Lease Agreement
Subsequent Event [Line Items]
Operating lease, option to extend			The lease provides an option to extend the lease for two additional two-year periods through December 31, 2029, which were not determined by the Company to be reasonably certain of being exercised.
Subsequent Event | Laboratory Space | March 2020 Amended Lease Agreement
Subsequent Event [Line Items]
Operating lease, commencement month and year	2020-04
Operating lease, expiration date	Dec. 31, 2025
Operating lease, existence of option to extend	true
Operating lease, number of renewal options | Option	2
Operating lease, option to extend term	2 years
Operating lease, expiration date	Dec. 31, 2029
Operating lease, right-of-use asset	$ 0
Operating lease, liability	0
Operating lease, undiscounted lease payments	$ 1,100,000