Beam Therapeutics (BEAM) 10-Q 8 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
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		68,135,798
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	false
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	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 612,023	$ 162,171
Marketable securities	321,382	137,500
Prepaid expenses and other current assets	8,019	8,650
Total current assets	941,424	308,321
Property and equipment, net	71,533	38,513
Restricted cash	14,840	14,840
Operating lease right-of-use assets	103,169	86,859
Long-term Investments	24,538	2,577
Other assets	1,051	567
Total assets	1,156,555	451,677
Current liabilities:
Accounts payable	7,282	6,314
Accrued expenses and other current liabilities	22,965	18,463
Derivative liabilities	49,600	71,200
Current portion of deferred revenue	12,822	24
Current portion of lease liability	6,484	4,218
Current portion of equipment financing liability	2,238	2,118
Total current liabilities	101,391	102,337
Long-term lease liability	133,120	96,014
Long-term equipment financing liability	3,598	5,294
Contingent consideration liabilities	26,960	0
Long-term portion of deferred revenue	36,820	394
Other liabilities	852	2,077
Total liabilities	302,741	206,116
Commitments and contingencies (See Note 7, Leases, Note 9, License agreements and Note 10, Collaboration and license agreements)
Stockholders’ equity:
Preferred stock, $0.01 par value; 25,000,000 shares authorized, and no shares issued or outstanding at September 30, 2021 and December 31, 2020, respectively
Common stock, $0.01 par value; 250,000,000 shares authorized, 68,126,713 and 58,446,016 issued, and 67,734,484 and 57,254,178 outstanding at September 30, 2021 and December 31, 2020, respectively	677	573
Additional paid-in capital	1,556,685	642,633
Accumulated other comprehensive income (loss)	19	(9)
Accumulated deficit	(703,567)	(397,636)
Total stockholders’ equity	853,814	245,561
Total liabilities and stockholders equity	$ 1,156,555	$ 451,677

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	25,000,000	25,000,000
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	250,000,000
Common stock, shares issued	68,126,713	58,446,016
Common stock, shares outstanding	67,734,484	57,254,178

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Other Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
License and collaboration revenue	$ 763	$ 6	$ 775	$ 18
Revenue, Product and Service [Extensible List]	beam:LicenseAndCollaborationRevenueMember	beam:LicenseAndCollaborationRevenueMember	beam:LicenseAndCollaborationRevenueMember	beam:LicenseAndCollaborationRevenueMember
Operating expenses:
Research and development	$ 54,623	$ 29,825	$ 290,306	$ 70,728
General and administrative	15,774	7,502	39,450	21,251
Total operating expenses	70,397	37,327	329,756	91,979
Loss from operations	(69,634)	(37,321)	(328,981)	(91,961)
Other income (expense):
Change in fair value of derivative liabilities	35,800	2,700	(8,400)	(8,700)
Change in fair value of long-term investments	(4,892)		21,960	517
Change in fair value of contingent consideration liabilities	10,599		9,553
Interest and other income (expense), net	9	169	(63)	1,016
Total other income (expense)	41,516	2,869	23,050	(7,167)
Net loss	(28,118)	(34,452)	(305,931)	(99,128)
Unrealized gain (loss) on marketable securities	(12)	(132)	28	25
Comprehensive loss	(28,130)	(34,584)	(305,903)	(99,103)
Reconciliation of net loss to net loss attributable to common stockholders:
Net loss	(28,118)	(34,452)	(305,931)	(99,128)
Accretion of redeemable convertible preferred stock to redemption value, including dividends on preferred stock				(1,277)
Net loss attributable to common stockholders	$ (28,118)	$ (34,452)	$ (305,931)	$ (100,405)
Net loss per common share attributable to common stockholders, basic	$ (0.42)	$ (0.69)	$ (4.86)	$ (2.31)
Net loss per common share attributable to common stockholders, diluted	$ (0.42)	$ (0.69)	$ (4.86)	$ (2.31)
Weighted-average common shares used in net loss per share attributable to common stockholders, basic	66,377,611	50,087,747	62,960,219	43,438,919
Weighted-average common shares used in net loss per share attributable to common stockholders, diluted	66,377,611	50,087,747	62,960,219	43,438,919

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' (Deficit) Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Redeemable Convertible Preferred Stock
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/private placement/At-the-Market offering, net of issuance costs	188,323	$ 122	188,201
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs, 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
Other comprehensive income (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
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
Net loss	(99,128)
Ending Balance at Sep. 30, 2020	200,071	$ 504	501,698	41	(302,172)
Ending Balance, Shares at Sep. 30, 2020		50,438,740
Beginning Balance at Mar. 31, 2020	261,394	$ 491	494,749	(344)	(233,502)
Beginning Balance, Shares at Mar. 31, 2020		49,077,350
Vesting of restricted common stock		$ 4	(4)
Vesting of restricted common stock, Shares		387,870
Stock-based compensation	2,769		2,769
Exercise of common stock options	360	$ 1	359
Exercise of common stock options, Shares		180,517
Other comprehensive income (loss)	517			517
Net loss	(34,218)				(34,218)
Ending Balance at Jun. 30, 2020	230,822	$ 496	497,873	173	(267,720)
Ending Balance, Shares at Jun. 30, 2020		49,645,737
Vesting of restricted common stock		$ 4	(4)
Vesting of restricted common stock, Shares		387,867
Issuance of common stock related to license agreement	264	$ 2	262
Issuance of common stock related to license agreement, Shares		175,000
Stock-based compensation	3,012		3,012
Exercise of common stock options	557	$ 2	555
Exercise of common stock options, Shares		230,136
Other comprehensive income (loss)	(132)			(132)
Net loss	(34,452)				(34,452)
Ending Balance at Sep. 30, 2020	200,071	$ 504	501,698	41	(302,172)
Ending Balance, Shares at Sep. 30, 2020		50,438,740
Beginning Balance at Dec. 31, 2020	245,561	$ 573	642,633	(9)	(397,636)
Beginning Balance, Shares at Dec. 31, 2020		57,254,178
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs	252,005	$ 28	251,977
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs, Shares		2,795,700
Issuance of common stock to acquire Guide	120,032	$ 10	120,022
Issuance of common stock to acquire Guide, Shares		1,087,153
Vesting of restricted common stock		$ 4	(4)
Vesting of restricted common stock, Shares		398,804
Stock-based compensation	4,648		4,648
Exercise of common stock options	1,758	$ 2	1,756
Exercise of common stock options, Shares		199,284
Other comprehensive income (loss)	(15)			(15)
Net loss	(201,560)				(201,560)
Ending Balance at Mar. 31, 2021	422,429	$ 617	1,021,032	(24)	(599,196)
Ending Balance, Shares at Mar. 31, 2021		61,735,119
Beginning Balance at Dec. 31, 2020	$ 245,561	$ 573	642,633	(9)	(397,636)
Beginning Balance, Shares at Dec. 31, 2020		57,254,178
Exercise of common stock options, Shares	774,352
Net loss	$ (305,931)
Ending Balance at Sep. 30, 2021	853,814	$ 677	1,556,685	19	(703,567)
Ending Balance, Shares at Sep. 30, 2021		67,734,484
Beginning Balance at Mar. 31, 2021	422,429	$ 617	1,021,032	(24)	(599,196)
Beginning Balance, Shares at Mar. 31, 2021		61,735,119
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs	157,785	$ 18	157,767
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs, Shares		1,761,285
Vesting of restricted common stock		$ 2	(2)
Vesting of restricted common stock, Shares		200,403
Issuance of common stock for success payment liability	30,000	$ 4	29,996
Issuance of common stock for success payment liability, Shares		349,650
Stock-based compensation	10,452		10,452
Exercise of common stock options	4,083	$ 4	4,079
Exercise of common stock options, Shares		406,225
Other comprehensive income (loss)	55			55
Net loss	(76,253)				(76,253)
Ending Balance at Jun. 30, 2021	548,551	$ 645	1,223,324	31	(675,449)
Ending Balance, Shares at Jun. 30, 2021		64,452,682
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs	318,609	$ 29	318,580
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs, Shares		2,912,557
Vesting of restricted common stock		$ 2	(2)
Vesting of restricted common stock, Shares		200,402
Stock-based compensation	12,968		12,968
Exercise of common stock options	1,816	$ 1	1,815
Exercise of common stock options, Shares		168,843
Other comprehensive income (loss)	(12)			(12)
Net loss	(28,118)				(28,118)
Ending Balance at Sep. 30, 2021	$ 853,814	$ 677	$ 1,556,685	$ 19	$ (703,567)
Ending Balance, Shares at Sep. 30, 2021		67,734,484

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' (Deficit) Equity (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
IPO
Stock issuance costs				$ 18.7
Private Placement
Stock issuance costs			$ 8
ATM Offering
Stock issuance costs	$ 8.6	$ 5.5

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (305,931)	$ (99,128)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,817	3,463
Amortization of investment discount (premiums)	(28)	49
In-process research and development charge	154,953
Stock-based compensation expense	28,068	8,573
Change in operating lease right-of-use assets	6,781	3,065
Non-cash research and development license expense, net		5,164
Change in fair value of derivative liabilities	8,400	8,700
Change in fair value of contingent consideration liabilities	(9,553)
Change in fair value of non-controlling equity investments	(21,960)	(517)
Other	63
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	733	(3,667)
Other long-term assets	(197)	(56)
Accounts payable	(1,341)	(134)
Accrued expenses and other liabilities	2,818	4,219
Operating lease liabilities	15,208	(3,249)
Deferred revenue	49,224
Other long-term liabilities	(153)	2,075
Net cash used in operating activities	(68,098)	(71,443)
Investing activities
Purchases of property and equipment	(33,442)	(8,232)
Purchases of marketable securities	(606,746)	(167,094)
Maturities of marketable securities	422,920	157,380
Net cash acquired from Guide	620
Purchase of long-term investment		(750)
Net cash used in investing activities	(216,648)	(18,696)
Financing activities
Proceeds from initial public offering, net of underwriting discount		192,510
Proceeds from issuance of common shares, net of commissions	737,205
Payment of equity offering costs	(8,688)	(1,717)
Proceeds from equipment financings		1,625
Repayment of equipment financings	(1,576)	(1,158)
Proceeds from exercise of stock options	7,657	1,069
Net cash provided by financing activities	734,598	192,329
Net change in cash, cash equivalents and restricted cash	449,852	102,190
Cash, cash equivalents and restricted cash—beginning of period	177,011	50,553
Cash, cash equivalents and restricted cash—end of period	626,863	152,743
Supplemental disclosure of cash flow information:
Cash paid for interest	443	422
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	7,515	2,809
Operating lease liabilities arising from obtaining right-of-use assets	24,164	5,795
Issuance of common stock for research and development license		264
Equity issuance costs in accounts payable and accrued expenses	118	342
Fair value of common shares issued to settle success payment liability	30,000
Contingent consideration liabilities assumed in asset acquisition	36,513
Fair value of equity instruments issued in connection with asset acquisition	$ 120,032
Accretion of redeemable convertible preferred stock to redemption value, including dividends on preferred stock		$ 1,277

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2021
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., which we refer to herein as the “Company” or “Beam,” is a biotechnology company committed to establishing the leading, fully integrated platform for precision genetic medicines. Beam’s vision is to provide life-long cures to patients suffering from genetic diseases. The Company was incorporated on January 25, 2017 as a Delaware corporation and began operations in July 2017. Its principal offices are in Cambridge, Massachusetts. In February 2021, the Company entered into an Agreement and Plan of Merger, or the Guide Merger Agreement, to acquire Guide Therapeutics, Inc., or Guide. Pursuant to the Guide Merger Agreement, the Company paid Guide’s former stockholders and optionholders upfront consideration in an aggregate amount of $ 120.0 million, excluding customary purchase price adjustments, in shares of its common stock, based upon the volume-weighted average price of the Company’s common stock over the ten-trading day period ending on February 19, 2021. In addition, Guide’s former stockholders and optionholders are eligible to receive up to an additional $ 100.0 million in technology milestone payments and $ 220.0 million in product milestone payments, payable in the Company’s common stock. Liquidity and capital resources Since its inception, the Company has devoted substantially all of its resources to building its base editing platform and advancing development of its portfolio of programs, establishing and protecting its intellectual property, conducting research and development activities, organizing and staffing the 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 product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. In February 2020, the Company completed its initial public offering, or 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 offering expenses payable by the Company. In connection with the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock converted into 29,127,523 shares of its common stock. In October 2020, the Company issued and sold 5,750,000 shares of its common stock, including 750,000 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 23.50 per share, for aggregate gross proceeds of $ 135.1 million. The Company received approximately $ 126.6 million in net proceeds after deducting underwriting discounts and offering expenses payable by the Company. On January 16, 2021, the Company entered into a Securities Purchase Agreement with certain purchasers, pursuant to which the Company agreed to sell and issue to the purchasers, in a private placement, shares of common stock of the Company. The closing of the private placement occurred on January 21, 2021. The Company issued and sold 2,795,700 shares of its common stock at a purchase price of $ 93.00 per share for aggregate gross proceeds of $ 260.0 million, before deducting fees to the placement agents and other offering expenses payable by the Company (See Note 11, Preferred and common stock ). The Company received approximately $ 252.0 million in net proceeds after deducting fees to the placement agents and offering expenses payable by the Company. In April 2021, the Company entered into an at the market, or ATM, sales agreement, or the Sales Agreement, with Jefferies LLC, or Jefferies, pursuant to which the Company was entitled to offer and sell, from time to time at prevailing market prices, shares of the Company’s common stock having aggregate gross proceeds of up to $ 300.0 million. The Company agreed to pay Jefferies a commission of up to 3.0 % of the aggregate gross sale proceeds of any shares sold by Jefferies under the Sales Agreement. As of September 30, 2021, the Company has sold 2,908,009 shares of its common stock under the Sales Agreement at an average price of $ 103.16 per share for aggregate gross proceeds of $ 300.0 million, before deducting commissions and offering expenses payable by the Company. In July 2021, the Company and Jefferies entered into an amendment to the Sales Agreement to provide for an increase in the aggregate offering amount under the Sales Agreement, such that as of July 7, 2021, the Company may offer and sell shares of common stock having an aggregate offering price of an additional $ 500.0 million. As of September 30, 2021, the Company has sold 1,765,833 additional shares of its common stock under the amended Sales Agreement at an average price of $ 107.88 per share for aggregate gross proceeds of $ 190.5 million, before deducting commissions and offering expenses payable by the Company, resulting in an aggregate of $ 490.5 million in gross proceeds received under the Sales Agreement as of September 30, 2021. Since its inception, the Company has incurred substantial losses and had an accumulated deficit of $ 703.6 million as of September 30, 2021. 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 September 30, 2021 of $ 933.4 million will be sufficient to fund its operations for at least the next 12 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. COVID-19-related significant risks and uncertainties With the ongoing concern related to the COVID-19 pandemic during 2020 and in the first nine months of 2021, the Company has maintained and expanded its business continuity plans 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 performed critical activities that must be completed on-site, limited the number of such personnel that could be present at its faciliti es at any one time, and requested that most of its employees work remotely. In May 2020, as certain states eased restrictions, the Company established new protocols to better allow its full laboratory staff access to the Company’s facilities. These protocols included several shifts working over a seven-day-week protocol. In June 2021, as states continued to ease restrictions, the Company started to allow for all of its employees to work on-site at the Company’s facilities, with fewer restrictions, particularly for vaccinated employees. The Company expects to continue incurring additional costs to ensure it adheres to the COVID-19 guidelines instituted by the Centers for Disease Control and Prevention and 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, and its results of operations and financial condition, including 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 duration, scope and severity of the pandemic, the duration and extent of travel restrictions and social distancing in the United States and other countries, business closures and business disruptions, the effectiveness of actions taken in the United States and other countries to contain and treat the disease, periodic spikes in infection rates, new strains of the virus that cause outbreaks of COVID-19, and the broad availability of effective vaccines. 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 nine months ended September 30, 2021 , 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	9 Months Ended
	Sep. 30, 2021
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, 2020, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the Securities and Exchange Commission on March 15, 2021, or the 2020 Form 10-K. Since the date of those financial statements, there have been no material changes to Beam’s significant accounting policies except as noted below. Basis of presentation The accompanying condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP. 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. Principles of consolidation The accompanying condensed consolidated financial statements include the results of operations of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. In September 2021, the Company's wholly-owned subsidiary Blink Therapeutics Inc., or Blink, merged with and into Beam, such that Blink’s separate corporate existence ceased and Beam continued as the surviving corporation. 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, the determination of the fair value equity instruments and intangible assets acquired in an asset acquisition, 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. Cash, cash equivalents, and restricted cash Cash and cash equivalents consist of standard checking accounts, money market accounts, and all highly liquid investments with a remaining 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 and manufacturing 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 statements of cash flows (in thousands): September 30, September 30, Cash and cash equivalents $ 612,023 $ 137,903 Restricted cash 14,840 14,840 Total cash, cash equivalents, and restricted cash $ 626,863 $ 152,743 Asset acquisitions In 2018, the Company adopted ASU 2017-01 , Business Combinations , or ASU 2017-01, which clarified the definition of a business. The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes transaction costs, and the consideration is allocated to the items acquired based on a relative fair value methodology. Goodwill is not recognized in asset acquisitions. In an asset acquisition, the cost allocated to acquire in-process research and development with no alternative future use is charged to research and development expense at the acquisition date. At the time of acquisition, the Company determines if a transaction should be accounted for as a business combination or acquisition of assets. Contingent consideration liabilities The estimated fair value of contingent consideration liabilities, initially measured and recorded on the acquisition date, are considered to be a Level 3 measurement and are reviewed quarterly, or whenever events or circumstances occur that indicate a change in fair value. The contingent consideration liabilities are recorded at fair value at the end of each reporting period with changes in estimated fair values recorded in other income (expense) in the condensed consolidated statements of operations and other comprehensive loss. The estimated fair value is determined based on probability adjusted discounted cash flow models that include significant estimates and assumptions pertaining to technology and product development. Significant changes in any of the probabilities of success would result in a significantly higher or lower fair value measurement. Significant changes in the probabilities as to the periods in which milestones will be achieved would result in a significantly lower or higher fair value measurement.

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	3. P roperty and equipment, net Property and equipment consist of the following (in thousands): September 30, December 31, Lab equipment $ 24,374 $ 17,201 Leasehold improvements 12,769 12,706 Furniture and fixtures 1,081 1,078 Computer equipment 576 547 Construction in process 46,255 15,880 Total property and equipment 85,055 47,412 Less accumulated depreciation ( 13,522 ) ( 8,899 ) Property and equipment, net $ 71,533 $ 38,513 The following table summarizes depreciation expense incurred (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Depreciation expense $ 1,675 $ 1,218 $ 4,642 $ 3,463

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2021
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, contingent consideration liabilities related to the Guide Merger Agreement, equity securities of Verve Therapeutics, Inc., or Verve, and success payment derivative liabilities pursuant to the license agreement, or the Harvard License Agreement, between President and Fellows of Harvard University, or Harvard, and the Company, and the license agreement, or the Broad License Agreement, between The Broad Institute, Inc., or Broad Institute, and the Company. The Company also holds an investment in privately issued corporate equity securities, which are accounted for as investments in equity securities. This investment does not have a readily determinable fair value and the Company values the investment based on the cost of the equity securities adjusted for observable market transactions or impairments, if any, and records any changes in value through earnings. The following table sets forth the fair value of the Company’s financial assets and liabilities by level within the fair value hierarchy at September 30, 2021 (in thousands): Carrying Fair Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 583,524 $ 583,524 $ 583,524 $ — $ — Commercial paper 28,499 28,499 — 28,499 — Marketable securities: Commercial paper 317,324 317,324 — 317,324 — Corporate notes 4,058 4,058 — 4,058 — Equity securities included in other long-term investments: Corporate equity securities 24,438 24,438 — 24,438 — Total assets $ 957,843 $ 957,843 $ 583,524 $ 374,319 $ — Liabilities Success payment liability – Harvard $ 24,700 $ 24,700 $ — $ — $ 24,700 Success payment liability – Broad Institute 24,900 24,900 — — 24,900 Contingent consideration liability – Technology 19,910 19,910 $ — $ — $ 19,910 Contingent consideration liability – Product 7,050 7,050 — — 7,050 Total liabilities $ 76,560 $ 76,560 $ — $ — $ 76,560 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, 2020 (in thousands): Carrying Fair Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 88,259 $ 88,259 $ 88,259 $ — $ — Commercial paper 60,494 60,497 — 60,497 — Corporate notes 12,314 12,308 — 12,308 — Marketable securities: Commercial paper 113,622 113,622 — 113,622 — Corporate notes 7,836 7,836 — 7,836 — U.S. Treasury securities 11,009 11,009 — 11,009 — Government securities 5,033 5,033 — 5,033 — Total assets $ 298,567 $ 298,564 $ 88,259 $ 210,305 $ — Liabilities Success payment liability – Harvard $ 35,500 $ 35,500 $ — $ — $ 35,500 Success payment liability – Broad Institute 35,700 35,700 — — 35,700 Total liabilities $ 71,200 $ 71,200 $ — $ — $ 71,200 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 and long-term investments – 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. During the nine months ended September 30, 2021, the Company held an investment in Verve consisting of shares of Verve’s common and preferred stock. Prior to Verve's initial public offering in June 2021, the Company valued such investment based on the cost of the equity securities adjusted for any observable market transactions. Following the initial public offering, the equity securities have a readily determinable fair value; however, they are subject to transfer restrictions. As of September 30, 2021 the Company owned 546,970 shares of Verve's common stock, the value of which is included in long-term investments in the condensed consolidated balance sheet. The Company recorded the investment at fair value of $ 24.4 million as of September 30, 2021, which resulted in the recognition of $ 4.9 million of other expense and $ 22.0 million of other income for the three and nine months ended September 30, 2021, respectively. Pursuant to ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities , the Company records changes in the fair value of its investments in equity securities to “Other income (expense), net” in the Company’s condensed consolidated statements of operations. Success payment liabilities – As discussed further in Note 9, License agreements , the Company is required to make payments determined based upon the achievement of specified multiples of the initial weighted average value of the Company’s redeemable convertible Series A-1 Preferred Stock and the Company's redeemable convertible Series A-2 Preferred Stock, or collectively the Series A Preferred Stock, or, subsequent to the IPO, the market value of Beam’s common stock, 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 September 30, December 31, September 30, December 31, Fair value of common stock (per share) $ 87.01 $ 81.64 $ 87.01 $ 81.64 Expected volatility 77 % 74 % 76 % 74 % Expected term (years) 0.10 - 7.75 0.35 - 8.49 0.10 - 8.61 0.35 - 9.36 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): Nine Months Ended September 30, 2021 Harvard Broad Institute Total Balance at December 31, 2020 $ 35,500 $ 35,700 $ 71,200 Payments ( 15,000 ) ( 15,000 ) ( 30,000 ) Change in fair value 4,200 4,200 8,400 Balance at September 30, 2021 $ 24,700 $ 24,900 $ 49,600 Contingent consideration liabilities – As discussed further in Note 8, Guide a cquisition , under the Guide Merger Agreement, Guide’s former stockholders and optionholders are eligible to receive up to an additional $ 100.0 million in technology milestone payments and $ 220.0 million in product milestone payments, payable in the Company’s common stock valued using the volume-weighted average price of the Company’s stock over the ten-day trading period ending two trading days prior to the date on which the applicable milestone is achieved. As these milestones are payable in the Company’s common stock, the milestone payments result in liability classification under ASC 480, Distinguishing Liabilities from Equity . These contingent consideration liabilities are carried at fair value which was estimated by applying a probability-based model, which utilized inputs based on timing of achievement that were unobservable in the market. These contingent consideration liabilities are classified within Level 3 of the fair value hierarchy. The following table reconciles the change in fair value of the contingent consideration liabilities based on level 3 inputs (in thousands): Nine Months Ended September 30, 2021 Technology Milestones Product Milestones Total Balance at February 23, 2021 (inception) $ 29,403 $ 7,110 $ 36,513 Change in fair value ( 9,493 ) ( 60 ) ( 9,553 ) Balance at September 30, 2021 $ 19,910 $ 7,050 $ 26,960 The following variables were incorporated in the calculation of the estimated fair value of the contingent consideration liabilities: Technology Milestones Product Milestones September 30, September 30, Discount Rate 7.50 % 7.50 % Probability of Achievement 10 - 50 % 2 - 15 % Projected Year of Achievement 2022 2023 - 2028

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2021
Investments Debt And Equity Securities [Abstract]
Marketable Securities	5. Marketable securities The following table summarizes the Company’s marketable securities held at September 30, 2021 (in thousands): Amortized Cost Gross Gross Fair Value Commercial paper $ 317,303 $ 26 $ ( 5 ) $ 317,324 Corporate notes 4,060 — ( 2 ) 4,058 Total $ 321,363 $ 26 $ ( 7 ) $ 321,382 The following table summarizes the Company’s marketable securities held at December 31, 2020 (in thousands): Amortized Cost Gross Gross Fair Value Commercial paper $ 113,628 $ 11 $ ( 17 ) $ 113,622 Corporate notes 7,839 2 ( 5 ) 7,836 U.S. Treasury securities 11,009 — — 11,009 Government securities 5,033 — — 5,033 Total $ 137,509 $ 13 $ ( 22 ) $ 137,500 The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. At September 30, 2021 , the balance in accumulated other comprehensive loss 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 nine months ended September 30, 2021 and 2020 and, as a result, the Company did not reclassify any amounts out of accumulated other comprehensive loss for the same periods. 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. The contractual maturity dates of all the investments are less than one year .

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2021
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): September 30, December 31, Employee compensation and related benefits $ 5,841 $ 7,591 Research costs 4,987 2,423 Professional fees 3,733 1,948 Process development and manufacturing costs 3,285 2,272 Other 5,119 4,229 Total $ 22,965 $ 18,463

Leases

Leases	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Leases	7. Leases Operating leases The Company’s operating leases are as follows:  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 is not reasonably certain of exercise.  An October 2018 lease for laboratory space, which commenced in April 2019 and was amended in March 2020 and April 2020 . The amended lease commenced in April 2020 and terminates in December 2025 . The amended lease is subject to fixed-rate rent escalations and provided an option to extend the lease for two additional two-year periods through December 31, 2029, which are not reasonably certain of being exercised. Upon commencement of the March 2020 amendment, the Company recorded an operating lease right-of-use, or ROU, asset and a lease liability of $ 4.2 million. Upon commencement of the April 2020 amendment, the Company recorded an operating lease ROU asset and a lease liability of $ 1.8 million.  Leases in June 2019 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.  An April 2019 lease for office and laboratory space to be built. Pursuant to the terms of the original lease agreement, the first phase of the lease commenced in October 2020 ( rent payments for the first phase beginning in August 2021 ) and the second phase of the lease com menced in January 2021 (rent payments for the second phase are expected to begin at the earliest in the first half of 2022). 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 five years each, which are not reasonably certain of exercise. The Company determined that it is the accounting owner of all tenant improvements. 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 September 30, 2021 and December 31, 2020 . Upon commencement of the first phase of this lease in October 2020, the Company recorded an operating lease ROU asset of $ 66.8 million and a lease liability of $ 68.8 million and upon commencement of the second phase of this lease in Ja nuary 2021, the Company recorded an operating lease ROU asset of $ 22.0 million and a corresponding lease liability of $ 23.0 million. Subsequently, during the second quarter of 2021, the Company amended the rent commencement dates of the first and second phases of this lease. Pursuant to the terms of the amendment, the lease will terminate on February 28, 2034 , which is 12 years from the amended second phase commencement date. As a result, the Company recorded an increase in the ROU asset of $ 0.5 million and an increase in lease liability of $ 0.5 million . The following table summarizes operating lease costs (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Operating lease costs $ 4,557 $ 1,644 13,660 4,946 Variable lease costs 588 249 1,162 786 Short-term lease costs 383 — 761 — Total $ 5,528 $ 1,893 $ 15,583 $ 5,732 The following table summarizes the lease term and discount rate for operating leases: September 30, December 31, Weighted-average remaining lease term (years) 11.4 11.5 Weighted-average discount rate 7.1 % 7.4 % The following table summarizes the lease costs for amounts included in the measurement of lease liabilities (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Operating cash flows used for operating leases $ 3,058 $ 2,014 $ 7,053 $ 5,132 Operating lease liabilities arising from obtaining ROU assets — — 24,164 5,795 At September 30, 2021, 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 2021 $ 4,159 2022 16,616 2023 17,262 2024 17,787 2025 18,260 Thereafter 132,835 Undiscounted lease payments 206,919 Less: imputed interest ( 67,315 ) Total operating lease liabilities $ 139,604 In August 2020, the Company entered into a lease agreement with Alexandria Real Estate Equities, Inc., or the Landlord, to build a 100,000 square foot manufacturing facility in Research Triangle Park, North Carolina intended to support a broad range of clinical programs. The lease has a term of 15 years following the commencement date and provides the Company the option to extend the lease term for two five-year terms. It is subject to fixed rate escalation increases and also provides up to $ 20.0 million for reimbursement of tenant improvements. As the lease had not commenced as of September 30, 2021 , the Company has not recorded an operating lease ROU asset or lease liability for this lease in the accompanying condensed consolidated balance sheets. The lease payments are subject to adjustment following the determination of the total project costs of the landlord. The initial estimate of the minimum amount of undiscounted lease payments due under this lease is $ 81.1 million. The Company anticipates that the facility will be operational in the first quarter of 2023. The tabular disclosure of minimum lease payments above does not include payments due under this lease. In August 2021, the Company executed a lease amendment to its April 2019 lease for office and laboratory space in Cambridge, Massachusetts to occupy additional space. The term of this lease will run concurrent with the term of the April 2019 lease. The initial estimate of the minimum amount of undiscounted lease payments due under this lease is $ 11.1 million. As the lease had not commenced as of September 30, 2021, the Company has not recorded an operating lease ROU asset or lease liability for this lease in the accompanying condensed consolidated balance sheets and the tabular disclosure of minimum lease payments above does not include the payments under this lease. In October 2021, the Company executed a lease for additional office and laboratory space at an existing facility. The term of this lease will run through December 31, 2025. The Company took access to part of this space in October 2021 and will record an operating lease ROU asset and lease liability during the fourth quarter of 2021. The initial estimate of the minimum amount of undiscounted lease payments due under this segment of the lease is $ 1.9 million. As part of this lease, the Company will take access to the remainder of this space in January 2022 and will record an operating lease ROU asset and lease liability during the first quarter of 2022. The initial estimate of the minimum amount of undiscounted lease payments due under this lease is $ 2.6 million. The tabular disclosure of minimum lease payments above does not include the payments under this segment of the lease.

Guide Acquisition

Guide Acquisition	9 Months Ended
	Sep. 30, 2021
Business Combinations [Abstract]
Guide Acquisition	8. Guide acquisition On February 23, 2021 , the Company entered into the Guide Merger Agreement. Under the Guide Merger Agreement, the Company paid Guide’s former stockholders and optionholders upfront consideration in an aggregate amount of $ 120.0 million, excluding customary purchase price adjustments and closing costs, in shares of the Company’s common stock, based upon the volume-weighted average price of the Company’s stock over the ten trading day period ending on February 19, 2021. Pursuant to the Guide Merger Agreement, Beam acquired all of the issued and outstanding shares of Guide. The Company issued a total of 1,087,153 shares of its common stock valued at $ 120.0 million in connection with the upfront payment to Guide’s former stockholders and optionholders. The Guide transaction resulted in the acquisition of certain know-how and intellectual property assets related to Guide’s proprietary in vivo LNP screening technology and its library of lipids and lipid nanoparticle formulations identified using the screening technology. Management determined that the acquired assets do not meet the definition of a business pursuant to ASC 805, Business Combinations , as substantially all of the fair value of the acquired assets is concentrated into one identifiable asset, the LNP screening technology and associated lipid library. As of the date of closing of the transactions contemplated by the Guide Merger Agreement, or the Guide Merger Agreement Date, the asset acquired had no alternative future use and had not reached a stage of technological feasibility. As a result, all share-based and cash payment obligations have been recorded as research and development expense in the accompanying condensed consolidated statements of operations and other comprehensive loss in the amount of $ 155.0 million. The total transaction price was allocated to the assets acquired and liabilities assumed on a relative fair value basis. In addition, Guide’s former stockholders and optionholders are eligible to receive up to an additional $ 100.0 million in technology milestone payments and $ 220.0 million in product milestone payments, payable in the Company’s common stock valued using the volume-weighted average price of the Company’s stock over the ten-day trading period ending two trading days prior to the date on which the applicable milestone is received. The Company determined that all future technology and product milestone payments are classified as contingent consideration liabilities under ASC 480 and therefore the Company recorded a liability for these milestones as of the Guide Merger Agreement Date at fair value of $ 36.5 million. These contingent consideration liabilities will be remeasured at fair value each financial reporting period, with the resulting impact reflected in the Company’s condensed consolidated statements of operations and other comprehensive loss, presented within other income (expense). The transaction price was determined and allocated as follows (in thousands): Transaction price Fair value of equity instruments issued $ 120,032 Technology and product contingent consideration liabilities 36,513 Transaction costs 2,531 Total transaction price $ 159,076 Transaction price allocated In-process research and development $ 154,953 Cash acquired 3,151 Prepaid expenses and other assets 264 Property and equipment 1,835 Assembled workforce 300 Other liabilities assumed ( 1,427 ) Total transaction price $ 159,076

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License Agreements	9. 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 Stock at specified valuation dates. The success payments range from $ 5.0 million to a maximum of $ 105.0 million and have valuation multiples that range from 5 times to 40 times the initial weighted average value of the Series A Preferred Stock. Subsequent to the Company’s February 2020 IPO, the amount of success payments is based on market value of Beam’s common stock. 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 twelfth 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 calculation of any amounts owed to Harvard on each rolling 90-day period, commencing one year after the Company’s IPO , with the first success payment becoming due in May 2021 . The following table summarizes the Company’s success payment liability for Harvard (in thousands): September 30, December 31, Harvard success payment liability $ 24,700 $ 35,500 The following table summarizes the expense resulting from the change in the fair value of the success payment liability for Harvard (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Change in fair value of Harvard success payment liability $ ( 17,900 ) $ ( 1,400 ) $ 4,200 $ 4,300 In May 2021, the first success payment measurement occurred and amounts due to Harvard were calculated to be $ 15.0 million. The Company elected to make the payment in shares of the Company’s common stock and issued 174,825 shares of the Company’s common stock to settle this liability on June 10, 2021. 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 September 30, 2021 , 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 nine months ended September 30, 2021. As of September 30, 2021 , no success payments were due to Harvard. 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 Series A Preferred Stock at specified valuation dates. The success payments range from $ 5.0 million to a maximum of $ 105.0 million and have valuation multiples that range from 5 times to 40 times the initial weighted average value of the Series A Preferred Stock. Subsequent to the Company’s February 2020 IPO, the amount of success payments is based on market value of Beam’s common stock. 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 calculation of any amounts owed to Broad Institute on each rolling 90-day period, commencing one year after the Company’s IPO, with the first success payment becoming due in May 2021 . The following table summarizes the Company’s success payment liability for Broad Institute (in thousands): September 30, December 31, Broad Institute success payment liability $ 24,900 $ 35,700 The following table summarizes the expense resulting from the change in the fair value of the success payment liability for Broad Institute (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Change in fair value of Broad Institute success payment liability $ ( 17,900 ) $ ( 1,300 ) $ 4,200 $ 4,400 In May 2021, the first success payment measurement occurred and amounts due to Broad Institute were calculated to be $ 15.0 million. The Company elected to make the payment in shares of the Company’s common stock and issued 174,825 shares of the Company’s common stock to settle this liability on June 10, 2021. 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 September 30, 2021 , 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 nine months ended September 30, 2021. As of September 30, 2021 , no success payments were due to Broad Institute. Editas license agreement In May 2018, the Company entered into a license agreement, or the Editas License Agreement, with Editas Medicine, Inc., or Editas. Pursuant to the Editas License Agreement, Editas granted to the Company licenses and options to acquire licenses to certain intellectual property rights owned or controlled by Editas, for specified uses. 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. As of September 30, 2021 , the Company determined that it owed a regulatory milestone payment to Editas under the License Agreement and recognized $ 0.1 million of expense for the three and nine months ended September 30, 2021. Bio Palette license agreement In March 2019, the Company entered into a license agreement, or the Bio Palette License Agreement, with Bio Palette Co., Ltd., or Bio Palette, pursuant to which the Company 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. In addition, the Company granted Bio Palette an exclusive (even as to the Company) 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. Unless earlier terminated, the Bio Palette License Agreement will expire on a licensed product-by-licensed product and country-by-country basis upon the expiration of the applicable royalty term for each such licensed product and country. Upon the issuance of a certain Bio Palette patent in the United States in June 2020, the Company made a milestone payment of $ 2.0 million and, in July 2020, issued to Bio Palette 175,000 shares of its common stock valued at $ 0.3 million. The fair value of the common stock issued to Bio Palette under the Bio Palette License Agreement was measured at the inception of arrangement and expensed when the issuance of shares became probable. Management concluded that the licenses acquired from each transaction above did not meet the accounting definition of a business as inputs, but no processes or outputs were acquired with the licenses, and the licensed technology had not achieved technological feasibility. As the inputs that were acquired along with the licenses do not constitute a “business,” the transactions have been accounted as asset acquisitions. As of the date of each license agreement, the assets acquired had no alternative future use and the assets had not reached a stage of technological feasibility. As a result, all share-based and cash payment obligations have been recorded as research and development expense in the accompanying condensed consolidated statements of operations and other comprehensive loss.

Collaboration and License Agree

Collaboration and License Agreements	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	10. Collaboration and license agreements Apellis Pharmaceuticals On June 30, 2021, the Company entered into a master research and collaboration agreement, or the Apellis Agreement, with Apellis Pharmaceuticals, Inc., or Apellis, focused on the use of certain of the Company’s base editing technology to discover new treatments for complement system-driven diseases. Under the terms of the Apellis Agreement, the Company will apply certain of its base editing technology and conduct preclinical research on up to six base editing programs that target specific genes within the complement system in various organs, including the eye, liver, and brain. Apellis will have exclusive rights to license each of the six programs (each an “Opt-In Right”) and will assume responsibility for subsequent development. The Company may elect to enter into a 50-50 U.S. co-development and co-commercialization agreement with Apellis with respect to one program licensed under the collaboration. The collaboration will be managed on an overall basis by an Alliance Steering Committee, or ASC, formed by an equal number of representatives from the Company and Apellis. As part of the collaboration, the Company is eligible to receive a total of $ 75.0 million in upfront and near-term milestones from Apellis, which is comprised of $ 50.0 million received upon signing and an additional $ 25.0 million payment on June 30, 2022, the one-year anniversary of the signing date of the Apellis Agreement, or the First Anniversary Payment. Following any exercise of an Opt-In Right for any of the six programs, the Company will be eligible to receive development, regulatory, and sales milestones from Apellis, as well as royalty payments on sales. The collaboration has an initial term of five years and may be extended up to two years on a per year and program-by-program basis. During the collaboration term, Apellis may, subject to certain limitations, substitute a specific complement gene and/or organ for any of the initial base editing programs. Apellis may terminate the Apellis Agreement for convenience on any or all of the programs by providing prior written notice. The Company received the $ 50.0 million in upfront payment from Apellis in July 2021. The Company accounts for the Apellis Agreement under ASC 606, Revenue from Contracts with Customers , or ASC 606, as it includes a customer-vendor relationship as defined under ASC 606 and meets the criteria to be considered a contract. The overall transaction price as of the inception of the contract was determined to be $ 75.0 million, which is composed of the upfront payment of $ 50.0 million and the First Anniversary Payment of $ 25.0 million. The Company will re-evaluate the transaction price in each reporting period. The $ 25.0 million for the First Anniversary Payment represents both a contract asset and a contract liability and the Company has presented these amounts net in accordance with ASC 606 guidance for contract assets and liabilities. The Company concluded that each of the six base editing programs combined with the research and development service, licenses, substitution rights and governance participation were material promises that were both capable of being distinct and were distinct within the context of the Apellis Agreement and represented separate performance obligations. Therefore, the Company did no t recognize any upfront revenue related to the license. The Company further concluded that the Opt-In Rights and option to extend the collaboration term did not grant Apellis a material right. The Company determined that the term of the contract is five years , as this is the period during which both parties have enforceable rights. The selling price of each performance obligation was determined based on the Company’s estimated standalone selling price, or the ESSP. The Company developed the ESSP for all of the performance obligations included in the Apellis Agreement with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company allocated the stand alone selling price to the performance obligations based on the relative standalone selling price method. The Company recognizes revenue for each performance obligation as it is satisfied over the five-year term using an input method. For the three and nine months ended September 30, 2021, the Company recognized $ 0.8 million of revenue related to the Apellis Agreement. As of September 30, 2021, there is $ 12.8 million and $ 36.4 million of current and non-current deferred revenue liability, respectively, related to the Apellis Agreement. Prime Medicine In September 2019, the Company entered into a collaboration and license agreement, or the Prime Agreement, with Prime Medicine Inc., or Prime Medicine, to research and develop a novel gene editing technology developed by one of the Company’s founders. Under the terms of the agreement, the Company granted Prime Medicine a non-exclusive license to certain of its clustered regulatory interspaced short palindromic repeats, or CRISPR, technology (including Cas12b), delivery technology and certain other technology controlled by the Company to develop and commercialize gene editing products for the treatment of human diseases. The Company is required to use commercially reasonable efforts 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. The Company had an obligation to issue $ 5.0 million in shares of its common stock to Prime Medicine, and Prime Medicine had an obligation to issue 5,000,000 shares of its common stock to the Company, should the Company elect to extend the collaboration beyond one year . In September 2020, the Company elected to continue the collaboration and, in October 2020, issued 200,307 shares of its common stock to Prime Medicine. The Company recognized $ 5.0 million as research and development expense for the three and nine months ended September 30, 2020 as a result of its decision to extend its collaboration with Prime Medicine. Additionally, in October 2020, the Company received 5,000,000 shares of Prime Medicine’s common stock and recognized $ 0.1 million as an offset to research and development expense for the year ended December 31, 2020. Additionally, the Company provided immaterial interim management and startup services to Prime Medicine through March 2021. As of September 30, 2021, the Company determined that future milestones and royalties under the Prime Agreement were not probable of recognition. Verve In April 2019, the Company entered into a collaboration and license agreement with Verve, or the Verve Agreement, to investigate gene editing strategies to modify genes associated with an increased risk of coronary diseases. Under the terms of the Verve 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 September 30, 2021 , the Company determined that milestones and royalties under the Verve Agreement were not probable of recognition.

Preferred and Common Stock

Preferred and Common Stock	9 Months Ended
	Sep. 30, 2021
Stockholders Equity [Abstract]
Preferred and Common Stock	11. Preferred and common stock In January 2020, the Company authorized the designation of 25,000,000 shares of preferred stock and increased its authorized common stock to 250,000,000 shares, each with a par value of $ 0.01 per share. 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 offering expenses payable by the Company. In connection with the IPO, all outstanding shares of the Company’s redeemable convertible preferred stock converted into 29,127,523 shares of the Company’s common stock. In October 2020, the Company issued and sold 5,750,000 shares of its common stock, including 750,000 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 23.50 per share, for aggregate gross proceeds of $ 135.1 million. The Company received approximately $ 126.6 million in net proceeds after deducting underwriting discounts and offering expenses payable by the Company. In October 2020, due to its election to continue the Prime Agreement, the Company issued 200,307 shares of its common stock to Prime Medicine. In January 2021, the Company issued and sold 2,795,700 shares of its common stock in a private placement at an offering price of $ 93.00 per share for aggregate gross proceeds of $ 260.0 million. The Company received $ 252.0 million in net proceeds after deducting fees to the placement agents and offering expenses payable by the Company. In April 2021, the Company entered into the Sales Agreement, with Jefferies, pursuant to which the Company was entitled to offer and sell, from time to time at prevailing market prices, shares of the Company’s common stock having aggregate gross proceeds of up to $ 300.0 million. The Company agreed to pay Jefferies a commission of up to 3.0 % of the aggregate gross sale proceeds of any shares sold by Jefferies under the Sales Agreement. As of September 30, 2021, the Company has sold 2,908,009 shares of its common stock under the Sales Agreement at an average price of $ 103.16 per share for aggregate gross proceeds of $ 300.0 million, before deducting commissions and offering expenses payable by the Company. In July 2021, the Company and Jefferies entered into an amendment to the Sales Agreement to provide for an increase in the aggregate offering amount under the Sales Agreement, such that as of July 7, 2021, the Company may offer and sell shares of common stock having an aggregate offering price of an additional $ 500.0 million. As of September 30, 2021, the Company has sold 1,765,833 additional shares of its common stock under the amended Sales Agreement at an average price of $ 107.88 per share for aggregate gross proceeds of $ 190.5 million, before deducting commissions and offering expenses payable by the Company, resulting in an aggregate of $ 490.5 million in gross proceeds received under the Sales Agreement as of September 30, 2021. In May 2021, the first success payment measurements under each of the Harvard License Agreement and Broad Institute License Agreement occurred and success payments to Harvard and Broad Institute were calculated to be $ 15.0 million and $ 15.0 million, respectively. The Company elected to make each payment in shares of the Company’s common stock and issued 174,825 shares of the Company’s common stock to each of Harvard and Broad Institute to settle these liabilities in June 2021. The holders of the Company’s common stock are entitled to one vote for each share of common stock. Subject to the payment in full of all preferential dividends to which the holders of the Company’s preferred stock are entitled, the holders of the Company’s common stock shall be entitled to receive ratably dividends out of funds legally available. In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the Company, after the payment or provision for payment of all debts and liabilities of the Company and all preferential amounts to which the holders of Company’s preferred stock are entitled with respect to the distribution of assets in liquidation, the holders of common stock shall be entitled to share ratably in the remaining assets of the Company available for distribution.

Stock Option and Grant Plan

Stock Option and Grant Plan	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option and Grant Plan	12. Stock option and grant plan Stock option and grant plan The Beam Therapeutics Inc. 2017 Stock Option and Grant Plan adopted by the Company’s board of directors in June 2017 and amended in each of February 2019 and May 2019 provided for the grant of qualified incentive stock options and nonqualified stock options, restricted stock awards, restricted stock units, 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 October 2019, 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 are granted under the 2019 Plan. The 2019 Plan provides for the 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 September 30, 2021, the Company had 9,019,805 shares reserved including 1,985,950 shares available for future issuance pursuant to 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 Nine Months Ended 2021 2020 2021 2020 Research and development $ 7,554 $ 1,999 $ 17,049 $ 5,577 General and administrative 5,414 1,013 11,019 2,996 Total stock-based compensation expense $ 12,968 $ 3,012 $ 28,068 $ 8,573 Stock options The following table provides a summary of option activity under the Company’s equity award plans: Number Weighted Outstanding at December 31, 2020 5,336,441 $ 9.70 Granted 1,638,143 88.57 Exercised ( 774,352 ) 9.89 Forfeitures ( 60,982 ) 28.53 Outstanding at September 30, 2021 6,139,250 30.53 Exercisable as of September 30, 2021 2,008,588 $ 9.57 The weighted-average grant date fair value per share of options granted in the nine months ended September 30, 2021 was $ 58.85 . As of September 30, 2021, there was $ 107.3 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.4 years. Restricted stock The Company issues shares of restricted common stock, including both restricted stock units and restricted stock awards. Restricted common stock issued generally vests over a period of two to four years . The following table summarizes the Company’s restricted stock activity: Shares Weighted- Unvested as of December 31, 2020 1,275,338 $ 10.95 Issued 819,830 88.13 Vested ( 799,609 ) 4.61 Cancelled ( 8,725 ) 80.04 Unvested as of September 30, 2021 1,286,834 $ 63.59 At September 30, 2021, there was approximately $ 74.5 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 period of approximately 2.7 years. In February 2020, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Employee Stock Purchase Plan, or ESPP, which was approved by the Company’s stockholders. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee directors, are eligible to purchase common stock of the Company at a reduced rate during offering periods. The ESPP permits participants to purchase common stock using funds contributed through payroll deductions, subject to a calendar year limit of $ 25,000 and at a purchase price of 85 % of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period. The first offering period commenced on October 1, 2021 . As of September 30, 2021 , the Company had 1,049,460 shares available for issuance under the ESPP.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	13. 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: As of September 30, 2021 2020 Unvested restricted stock 1,286,834 1,492,203 Outstanding options to purchase common stock 6,139,250 5,633,485 Total 7,426,084 7,125,688 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 September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ ( 28,118 ) $ ( 34,452 ) $ ( 305,931 ) $ ( 100,405 ) Denominator: Weighted average number of common shares, basic and diluted 66,377,611 50,087,747 62,960,219 43,438,919 Net loss per common share attributable to common stockholders, basic and diluted $ ( 0.42 ) $ ( 0.69 ) $ ( 4.86 ) $ ( 2.31 )

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	14. Income taxes During the three and nine months ended September 30, 2021 and 2020 , 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	9 Months Ended
	Sep. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	15. Related party transactions Founders The Company made payments of $ 0.1 million and $ 0.3 million to its three founder shareholders for scientific consulting and other expenses for the three and nine months ended September 30, 2021, respectively. Verve The Company and Verve are parties to the Verve Agreement and have a common board member. Prior to Verve’s initial public offering in June 2021, the Company owned both common and preferred shares of Verve and valued such investment based on the cost of the equity securities adjusted for any observable market transactions. Following the initial public offering, the equity securities have a readily determinable fair value; however, they are subject to transfer restrictions. Following the initial public offering, the Company owned 546,970 shares of Verve's common stock, the value of which is included in long-term investments in the condensed consolidated balance sheet. The Company recorded the investment at fair value as of September 30, 2021, which resulted in the recognition of $ 4.9 million of other expense and $ 22.0 million of other income for the three and nine months ended September 30, 2021, respectively. The value of this investment as of September 30, 2021 is $ 24.4 million. During the nine months ended September 30, 2020 , the Company purchased shares of Verve's series A preferred stock valued at $ 0.8 million and recognized gains of $ 0.5 million, which is recorded in other income, on its investment in Verve stock. The Company purchased certain materials from Verve amounting to $ 0.2 million, which are recorded as research and development expenses within the accompanying condensed consolidated statements of operations and other comprehensive loss, for the nine months ended September 30, 2021 . The Company purchased certain materials from Verve amounting to $ 0.3 million for the nine months ended September 30, 2020 . The Company also sold certain materials to Verve amounting to $ 0.2 million for the nine months ended September 30, 2020. In October 2021, the Company entered into an agreement pursuant to which Verve will sublease 12,000 square feet of Beam's existing office and laboratory space for a term of one year beginning in December 2021 . Verve is expected to pay approximately $ 1.4 million in rental payments over the term of the sublease, as well as its proportionate costs for the landlord’s operating expense, insurance, property taxes, and utilities. Prime Medicine The Company and Prime Medicine are parties to the Prime Agreement and have a common founder and a common board member. Additionally, in September 2019, in connection with the Prime Agreement, the Company executed a letter agreement, as amended, to provide certain interim management and startup services to Prime Medicine through March 2021. Prime Medicine was obligated to reimburse the Company’s out-of-pocket costs incurred in connection with performing these services and, beginning in October 2020 and ending in March 2021, paid the Company a $ 30,000 monthly service fee. For the nine months ended September 30, 2021 , the Company recognized $ 0.1 million for performing such services in interest and other income (expense), net, within the accompanying consolidated statements of operations and other comprehensive loss.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent events Sana Biotechnology In October 2021, the Company entered into an option and license agreement with Sana Biotechnology, Inc., or Sana, to provide Sana with non-exclusive commercial rights to the Company’s CRISPR Cas12b nuclease system for certain ex vivo engineered cell therapy programs. The agreement excludes any rights to base editing using the Company’s CRISPR Cas12b system, which commercial rights remain with the Company. Under the terms of the agreement, Sana agreed to pay the Company an upfront payment of $ 50.0 million. The Company received this payment in October 2021. The Company is also eligible to receive certain target option exercise fees, certain milestone payments upon the achievement of certain development and commercial sale milestones, and certain royalties on net sales of royalty-bearing products by Sana.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of presentation The accompanying condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or GAAP. 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.
Principles of Consolidation	Principles of consolidation The accompanying condensed consolidated financial statements include the results of operations of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. In September 2021, the Company's wholly-owned subsidiary Blink Therapeutics Inc., or Blink, merged with and into Beam, such that Blink’s separate corporate existence ceased and Beam continued as the surviving corporation.
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, the determination of the fair value equity instruments and intangible assets acquired in an asset acquisition, 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.
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 a remaining 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 and manufacturing 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 statements of cash flows (in thousands): September 30, September 30, Cash and cash equivalents $ 612,023 $ 137,903 Restricted cash 14,840 14,840 Total cash, cash equivalents, and restricted cash $ 626,863 $ 152,743
Asset Acquisitions	Asset acquisitions In 2018, the Company adopted ASU 2017-01 , Business Combinations , or ASU 2017-01, which clarified the definition of a business. The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes transaction costs, and the consideration is allocated to the items acquired based on a relative fair value methodology. Goodwill is not recognized in asset acquisitions. In an asset acquisition, the cost allocated to acquire in-process research and development with no alternative future use is charged to research and development expense at the acquisition date. At the time of acquisition, the Company determines if a transaction should be accounted for as a business combination or acquisition of assets.
Contingent Consideration Liabilities	Contingent consideration liabilities The estimated fair value of contingent consideration liabilities, initially measured and recorded on the acquisition date, are considered to be a Level 3 measurement and are reviewed quarterly, or whenever events or circumstances occur that indicate a change in fair value. The contingent consideration liabilities are recorded at fair value at the end of each reporting period with changes in estimated fair values recorded in other income (expense) in the condensed consolidated statements of operations and other comprehensive loss. The estimated fair value is determined based on probability adjusted discounted cash flow models that include significant estimates and assumptions pertaining to technology and product development. Significant changes in any of the probabilities of success would result in a significantly higher or lower fair value measurement. Significant changes in the probabilities as to the periods in which milestones will be achieved would result in a significantly lower or higher fair value measurement.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2021
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 statements of cash flows (in thousands): September 30, September 30, Cash and cash equivalents $ 612,023 $ 137,903 Restricted cash 14,840 14,840 Total cash, cash equivalents, and restricted cash $ 626,863 $ 152,743

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): September 30, December 31, Lab equipment $ 24,374 $ 17,201 Leasehold improvements 12,769 12,706 Furniture and fixtures 1,081 1,078 Computer equipment 576 547 Construction in process 46,255 15,880 Total property and equipment 85,055 47,412 Less accumulated depreciation ( 13,522 ) ( 8,899 ) Property and equipment, net $ 71,533 $ 38,513
Summary of Depreciation Expense Incurred	The following table summarizes depreciation expense incurred (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Depreciation expense $ 1,675 $ 1,218 $ 4,642 $ 3,463

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2021
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 September 30, 2021 (in thousands): Carrying Fair Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 583,524 $ 583,524 $ 583,524 $ — $ — Commercial paper 28,499 28,499 — 28,499 — Marketable securities: Commercial paper 317,324 317,324 — 317,324 — Corporate notes 4,058 4,058 — 4,058 — Equity securities included in other long-term investments: Corporate equity securities 24,438 24,438 — 24,438 — Total assets $ 957,843 $ 957,843 $ 583,524 $ 374,319 $ — Liabilities Success payment liability – Harvard $ 24,700 $ 24,700 $ — $ — $ 24,700 Success payment liability – Broad Institute 24,900 24,900 — — 24,900 Contingent consideration liability – Technology 19,910 19,910 $ — $ — $ 19,910 Contingent consideration liability – Product 7,050 7,050 — — 7,050 Total liabilities $ 76,560 $ 76,560 $ — $ — $ 76,560 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, 2020 (in thousands): Carrying Fair Level 1 Level 2 Level 3 Assets Cash equivalents: Money market funds $ 88,259 $ 88,259 $ 88,259 $ — $ — Commercial paper 60,494 60,497 — 60,497 — Corporate notes 12,314 12,308 — 12,308 — Marketable securities: Commercial paper 113,622 113,622 — 113,622 — Corporate notes 7,836 7,836 — 7,836 — U.S. Treasury securities 11,009 11,009 — 11,009 — Government securities 5,033 5,033 — 5,033 — Total assets $ 298,567 $ 298,564 $ 88,259 $ 210,305 $ — Liabilities Success payment liability – Harvard $ 35,500 $ 35,500 $ — $ — $ 35,500 Success payment liability – Broad Institute 35,700 35,700 — — 35,700 Total liabilities $ 71,200 $ 71,200 $ — $ — $ 71,200
Success Payment Liabilities
Schedule of Variables Included in Calculation of Estimated Fair Value	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 September 30, December 31, September 30, December 31, Fair value of common stock (per share) $ 87.01 $ 81.64 $ 87.01 $ 81.64 Expected volatility 77 % 74 % 76 % 74 % Expected term (years) 0.10 - 7.75 0.35 - 8.49 0.10 - 8.61 0.35 - 9.36
Schedule of change in Fair Value of 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): Nine Months Ended September 30, 2021 Harvard Broad Institute Total Balance at December 31, 2020 $ 35,500 $ 35,700 $ 71,200 Payments ( 15,000 ) ( 15,000 ) ( 30,000 ) Change in fair value 4,200 4,200 8,400 Balance at September 30, 2021 $ 24,700 $ 24,900 $ 49,600
Contingent Consideration Liabilities
Schedule of Variables Included in Calculation of Estimated Fair Value	The following variables were incorporated in the calculation of the estimated fair value of the contingent consideration liabilities: Technology Milestones Product Milestones September 30, September 30, Discount Rate 7.50 % 7.50 % Probability of Achievement 10 - 50 % 2 - 15 % Projected Year of Achievement 2022 2023 - 2028
Schedule of change in Fair Value of Liabilities based on Level 3 inputs	The following table reconciles the change in fair value of the contingent consideration liabilities based on level 3 inputs (in thousands): Nine Months Ended September 30, 2021 Technology Milestones Product Milestones Total Balance at February 23, 2021 (inception) $ 29,403 $ 7,110 $ 36,513 Change in fair value ( 9,493 ) ( 60 ) ( 9,553 ) Balance at September 30, 2021 $ 19,910 $ 7,050 $ 26,960

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2021
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities Held	The following table summarizes the Company’s marketable securities held at September 30, 2021 (in thousands): Amortized Cost Gross Gross Fair Value Commercial paper $ 317,303 $ 26 $ ( 5 ) $ 317,324 Corporate notes 4,060 — ( 2 ) 4,058 Total $ 321,363 $ 26 $ ( 7 ) $ 321,382 The following table summarizes the Company’s marketable securities held at December 31, 2020 (in thousands): Amortized Cost Gross Gross Fair Value Commercial paper $ 113,628 $ 11 $ ( 17 ) $ 113,622 Corporate notes 7,839 2 ( 5 ) 7,836 U.S. Treasury securities 11,009 — — 11,009 Government securities 5,033 — — 5,033 Total $ 137,509 $ 13 $ ( 22 ) $ 137,500

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): September 30, December 31, Employee compensation and related benefits $ 5,841 $ 7,591 Research costs 4,987 2,423 Professional fees 3,733 1,948 Process development and manufacturing costs 3,285 2,272 Other 5,119 4,229 Total $ 22,965 $ 18,463

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2021
Leases [Abstract]
Summary of Operating Lease Costs	The following table summarizes operating lease costs (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Operating lease costs $ 4,557 $ 1,644 13,660 4,946 Variable lease costs 588 249 1,162 786 Short-term lease costs 383 — 761 — Total $ 5,528 $ 1,893 $ 15,583 $ 5,732
Summary of Lease Term and Discount Rate	The following table summarizes the lease term and discount rate for operating leases: September 30, December 31, Weighted-average remaining lease term (years) 11.4 11.5 Weighted-average discount rate 7.1 % 7.4 %
Summary of Lease Costs Included in Measurement of Lease Liabilities	The following table summarizes the lease costs for amounts included in the measurement of lease liabilities (in thousands): Three Months Ended Nine Months Ended 2021 2020 2021 2020 Operating cash flows used for operating leases $ 3,058 $ 2,014 $ 7,053 $ 5,132 Operating lease liabilities arising from obtaining ROU assets — — 24,164 5,795
Summary of Future Minimum Lease Payments of Operating Leases	At September 30, 2021, 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 2021 $ 4,159 2022 16,616 2023 17,262 2024 17,787 2025 18,260 Thereafter 132,835 Undiscounted lease payments 206,919 Less: imputed interest ( 67,315 ) Total operating lease liabilities $ 139,604

Guide Acquisition (Tables)

Guide Acquisition (Tables)	9 Months Ended
	Sep. 30, 2021
Business Combinations [Abstract]
Summary of Transaction Price Determined and Allocated	The transaction price was determined and allocated as follows (in thousands): Transaction price Fair value of equity instruments issued $ 120,032 Technology and product contingent consideration liabilities 36,513 Transaction costs 2,531 Total transaction price $ 159,076 Transaction price allocated In-process research and development $ 154,953 Cash acquired 3,151 Prepaid expenses and other assets 264 Property and equipment 1,835 Assembled workforce 300 Other liabilities assumed ( 1,427 ) Total transaction price $ 159,076

License Agreements (Tables)

License Agreements (Tables)	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Success Payment Liability	The following table summarizes the Company’s success payment liability for Harvard (in thousands): September 30, December 31, Harvard success payment liability $ 24,700 $ 35,500 The following table summarizes the Company’s success payment liability for Broad Institute (in thousands): September 30, December 31, Broad Institute success payment liability $ 24,900 $ 35,700
Schedule of Change in Fair Value of Success Payment Liability	The following table summarizes the expense resulting from the change in the fair value of the success payment liability for Harvard (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Change in fair value of Harvard success payment liability $ ( 17,900 ) $ ( 1,400 ) $ 4,200 $ 4,300 The following table summarizes the expense resulting from the change in the fair value of the success payment liability for Broad Institute (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Change in fair value of Broad Institute success payment liability $ ( 17,900 ) $ ( 1,300 ) $ 4,200 $ 4,400

Stock Option and Grant Plan (Ta

Stock Option and Grant Plan (Tables)	9 Months Ended
	Sep. 30, 2021
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 Nine Months Ended 2021 2020 2021 2020 Research and development $ 7,554 $ 1,999 $ 17,049 $ 5,577 General and administrative 5,414 1,013 11,019 2,996 Total stock-based compensation expense $ 12,968 $ 3,012 $ 28,068 $ 8,573
Summary of Option Activity Under Equity Award Plans	summary of option activity under the Company’s equity award plans: Number Weighted Outstanding at December 31, 2020 5,336,441 $ 9.70 Granted 1,638,143 88.57 Exercised ( 774,352 ) 9.89 Forfeitures ( 60,982 ) 28.53 Outstanding at September 30, 2021 6,139,250 30.53 Exercisable as of September 30, 2021 2,008,588 $ 9.57
Summary of Restricted Stock Activity	The following table summarizes the Company’s restricted stock activity: Shares Weighted- Unvested as of December 31, 2020 1,275,338 $ 10.95 Issued 819,830 88.13 Vested ( 799,609 ) 4.61 Cancelled ( 8,725 ) 80.04 Unvested as of September 30, 2021 1,286,834 $ 63.59

Net Loss per Share Attributab_2

Net Loss per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2021
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: As of September 30, 2021 2020 Unvested restricted stock 1,286,834 1,492,203 Outstanding options to purchase common stock 6,139,250 5,633,485 Total 7,426,084 7,125,688
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 September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Numerator: Net loss attributable to common stockholders $ ( 28,118 ) $ ( 34,452 ) $ ( 305,931 ) $ ( 100,405 ) Denominator: Weighted average number of common shares, basic and diluted 66,377,611 50,087,747 62,960,219 43,438,919 Net loss per common share attributable to common stockholders, basic and diluted $ ( 0.42 ) $ ( 0.69 ) $ ( 4.86 ) $ ( 2.31 )

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($)

Feb. 23, 2021

Jan. 16, 2021

Apr. 30, 2021

Feb. 28, 2021

Oct. 31, 2020

Feb. 29, 2020

Sep. 30, 2021

Jun. 30, 2021

Mar. 31, 2021

Mar. 31, 2020

Sep. 30, 2021

Jul. 07, 2021

Dec. 31, 2020

Nature Of Business And Basis Of Presentation [Line Items]

Gross proceeds from issuance of common stock

$ 135,100,000

Accumulated deficit

$ 703,567,000

$ 703,567,000

$ 397,636,000

Cash, cash equivalents, and marketable securities

$ 933,400,000

933,400,000

Common Stock

Nature Of Business And Basis Of Presentation [Line Items]

Shares issued and sold

5,750,000

2,912,557

1,761,285

2,795,700

12,176,471

Public offering price per share

$ 23.50

Net proceeds from sale of common stock

$ 126,600,000

$ 188,300,000

IPO | Common Stock

Nature Of Business And Basis Of Presentation [Line Items]

Shares issued and sold

12,176,471

Public offering price per share

$ 17

Gross proceeds from issuance of common stock

$ 207,000,000

Net proceeds from sale of common stock

$ 188,300,000

Shares issued upon conversion of preferred stock

29,127,523

Underwriters Option | Common Stock

Nature Of Business And Basis Of Presentation [Line Items]

Shares issued and sold

750,000

1,588,235

Private Placement

Nature Of Business And Basis Of Presentation [Line Items]

Gross proceeds from issuance of common stock

$ 260,000,000

Private Placement | Common Stock

Nature Of Business And Basis Of Presentation [Line Items]

Shares issued and sold

2,795,700

Public offering price per share

$ 93

Net proceeds from sale of common stock

$ 252,000,000

Jeffries LLC Amended Sales Agreement

Nature Of Business And Basis Of Presentation [Line Items]

Gross proceeds from issuance of common stock

$ 190,500,000

Jeffries LLC Amended Sales Agreement | Common Stock

Nature Of Business And Basis Of Presentation [Line Items]

Shares issued and sold

1,765,833

Public offering price per share

$ 107.88

$ 107.88

Jeffries LLC Amended Sales Agreement | At-The-Market

Nature Of Business And Basis Of Presentation [Line Items]

Aggregate gross proceeds of shares authorized under ATM sales agreement

$ 500,000,000

Jeffries LLC Sales Agreement

Nature Of Business And Basis Of Presentation [Line Items]

Stock sold during period shares, new issues

2,908,009

Public offering price per share

$ 103.16

$ 103.16

Gross proceeds from issuance of common stock

$ 300,000,000

Jeffries LLC Sales Agreement | Maximum | At-The-Market

Nature Of Business And Basis Of Presentation [Line Items]

Commission rate

3.00%

Aggregate gross proceeds of shares authorized under ATM sales agreement

$ 300,000,000

Jeffries LLC Sales Agreement and Amended Sales Agreement

Nature Of Business And Basis Of Presentation [Line Items]

Gross proceeds from issuance of common stock

$ 490,500,000

Guide Therapeutics, Inc. | Merger Agreement

Nature Of Business And Basis Of Presentation [Line Items]

Business combination upfront consideration paid in common stock

$ 120,000,000

$ 120,000,000

Merger agreement description

the Company paid Guide’s former stockholders and optionholders upfront consideration in an aggregate amount of $120.0 million, excluding customary purchase price adjustments, in shares of its common stock, based upon the volume-weighted average price of the Company’s common stock over the ten-trading day period ending on February 19, 2021.

Milestone payment method, description

In addition, Guide’s former stockholders and optionholders are eligible to receive up to an additional $100.0 million in technology milestone payments and $220.0 million in product milestone payments, payable in the Company’s common stock.

Guide Therapeutics, Inc. | Technology Milestones | Merger Agreement | Former Stockholders and Optionholders | Maximum

Nature Of Business And Basis Of Presentation [Line Items]

Potential milestone payable in form of common stock

100,000,000

Guide Therapeutics, Inc. | Product Milestones | Merger Agreement | Former Stockholders and Optionholders | Maximum

Nature Of Business And Basis Of Presentation [Line Items]

Potential milestone payable in form of common stock

$ 220,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 612,023	$ 162,171	$ 137,903
Restricted cash	14,840	14,840	14,840
Total cash, cash equivalents, and restricted cash	$ 626,863	$ 177,011	$ 152,743	$ 50,553

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details)	1 Months Ended
	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted	true
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201701Member

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 85,055	$ 47,412
Less accumulated depreciation	(13,522)	(8,899)
Property and equipment, net	71,533	38,513
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	24,374	17,201
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	12,769	12,706
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,081	1,078
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	576	547
Construction in Process
Property Plant And Equipment [Line Items]
Total property and equipment	$ 46,255	$ 15,880

Property and Equipment, Net -_2

Property and Equipment, Net - Summary of Depreciation Expense Incurred (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 1,675	$ 1,218	$ 4,642	$ 3,463

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Fair Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Marketable securities	$ 321,382	$ 137,500
Commercial Paper
Assets
Marketable securities	317,324	113,622
Harvard
Liabilities
Success payment liability	24,700	35,500
Broad Institute
Liabilities
Success payment liability	24,900	35,700
Recurring | Carrying Amount
Assets
Total assets	957,843	298,567
Liabilities
Total liabilities	76,560	71,200
Recurring | Carrying Amount | Money Market Funds
Assets
Cash equivalents	583,524	88,259
Recurring | Carrying Amount | Commercial Paper
Assets
Cash equivalents	28,499	60,494
Marketable securities	317,324	113,622
Recurring | Carrying Amount | Corporate Notes
Assets
Cash equivalents		12,314
Marketable securities	4,058	7,836
Recurring | Carrying Amount | Corporate Equity Securities
Assets
Equity securities included in other long-term investments	24,438
Recurring | Carrying Amount | Government Securities
Assets
Marketable securities		5,033
Recurring | Carrying Amount | U.S. Treasury Securities
Assets
Marketable securities		11,009
Recurring | Carrying Amount | Contingent Consideration of Technology Liabilities
Liabilities
Contingent consideration liability	19,910
Recurring | Carrying Amount | Contingent Consideration of Product Liabilities
Liabilities
Contingent consideration liability	7,050
Recurring | Fair Value
Assets
Total assets	957,843	298,564
Liabilities
Total liabilities	76,560	71,200
Recurring | Fair Value | Money Market Funds
Assets
Cash equivalents	583,524	88,259
Recurring | Fair Value | Commercial Paper
Assets
Cash equivalents	28,499	60,497
Marketable securities	317,324	113,622
Recurring | Fair Value | Corporate Notes
Assets
Cash equivalents		12,308
Marketable securities	4,058	7,836
Recurring | Fair Value | Corporate Equity Securities
Assets
Equity securities included in other long-term investments	24,438
Recurring | Fair Value | Government Securities
Assets
Marketable securities		5,033
Recurring | Fair Value | U.S. Treasury Securities
Assets
Marketable securities		11,009
Recurring | Fair Value | Contingent Consideration of Technology Liabilities
Liabilities
Contingent consideration liability	19,910
Recurring | Fair Value | Contingent Consideration of Product Liabilities
Liabilities
Contingent consideration liability	7,050
Recurring | Fair Value | Level 1
Assets
Total assets	583,524	88,259
Recurring | Fair Value | Level 1 | Money Market Funds
Assets
Cash equivalents	583,524	88,259
Recurring | Fair Value | Level 2
Assets
Total assets	374,319	210,305
Recurring | Fair Value | Level 2 | Commercial Paper
Assets
Cash equivalents	28,499	60,497
Marketable securities	317,324	113,622
Recurring | Fair Value | Level 2 | Corporate Notes
Assets
Cash equivalents		12,308
Marketable securities	4,058	7,836
Recurring | Fair Value | Level 2 | Corporate Equity Securities
Assets
Equity securities included in other long-term investments	24,438
Recurring | Fair Value | Level 2 | Government Securities
Assets
Marketable securities		5,033
Recurring | Fair Value | Level 2 | U.S. Treasury Securities
Assets
Marketable securities		11,009
Recurring | Fair Value | Level 3
Liabilities
Total liabilities	76,560	71,200
Recurring | Fair Value | Level 3 | Contingent Consideration of Technology Liabilities
Liabilities
Contingent consideration liability	19,910
Recurring | Fair Value | Level 3 | Contingent Consideration of Product Liabilities
Liabilities
Contingent consideration liability	7,050
Recurring | Harvard | Carrying Amount
Liabilities
Success payment liability	24,700	35,500
Recurring | Harvard | Fair Value
Liabilities
Success payment liability	24,700	35,500
Recurring | Harvard | Fair Value | Level 3
Liabilities
Success payment liability	24,700	35,500
Recurring | Broad Institute | Carrying Amount
Liabilities
Success payment liability	24,900	35,700
Recurring | Broad Institute | Fair Value
Liabilities
Success payment liability	24,900	35,700
Recurring | Broad Institute | Fair Value | Level 3
Liabilities
Success payment liability	$ 24,900	$ 35,700

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Schedule of Calculation of Estimated Fair Value of Success Payment Liabilities (Details) - Success Payment Liabilities	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value of Common Stock | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability measurement input	87.01	81.64
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	87.01	81.64
Expected Volatility | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability measurement input	77	74
Expected Volatility | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability measurement input	76	74
Expected Term (years) | Minimum | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	1 month 6 days	4 months 6 days
Expected Term (years) | Minimum | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	1 month 6 days	4 months 6 days
Expected Term (years) | Maximum | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	7 years 9 months	8 years 5 months 26 days
Expected Term (years) | Maximum | Broad Institute
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, term	8 years 7 months 9 days	9 years 4 months 9 days

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Schedule of Change in Fair Value of Success Payment Liabilities Based on Level 3 Inputs (Details) - Success Payment Liabilities $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 71,200
Payments	(30,000)
Change in fair value	8,400
Balance at September 30, 2021	49,600
Harvard
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	35,500
Payments	(15,000)
Change in fair value	4,200
Balance at September 30, 2021	24,700
Broad Institute
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	35,700
Payments	(15,000)
Change in fair value	4,200
Balance at September 30, 2021	$ 24,900

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Feb. 29, 2020	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Feb. 23, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent liabilities		$ 26,960	$ 26,960			$ 0
Equity securities recognition amount		(4,892)	21,960	$ 517
Verve Therapeutics, Inc.
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities recognition amount		(4,900)	22,000
Equity securities		$ 24,400	$ 24,400
Verve Therapeutics, Inc. | Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of shares purchased under equity method	546,970		546,970
Guide Therapeutics, Inc. | Merger Agreement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent liabilities					$ 36,500
Technology Milestones | Guide Therapeutics, Inc. | Maximum | Merger Agreement | Former Stockholders and Optionholders
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Potential milestone payable in form of common stock					100,000
Product Milestones | Guide Therapeutics, Inc. | Maximum | Merger Agreement | Former Stockholders and Optionholders
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Potential milestone payable in form of common stock					$ 220,000

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Schedule of Change in Fair Value of Contingent Consideration Liabilities Based on Level 3 Inputs (Details) - Contingent Consideration Liabilities $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 36,513
Change in fair value	(9,553)
Balance at September 30, 2021	26,960
Technology Milestones
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	29,403
Change in fair value	(9,493)
Balance at September 30, 2021	19,910
Product Milestones
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	7,110
Change in fair value	(60)
Balance at September 30, 2021	$ 7,050

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Schedule of Calculation of Estimated Fair Value of Contingent Consideration Liabilities (Details) - Contingent Consideration Liabilities	9 Months Ended
	Sep. 30, 2021
Technology Milestones
Derivative Liability [Abstract]
Milestone liabilities projected year of achievement	2022
Product Milestones | Minimum
Derivative Liability [Abstract]
Milestone liabilities projected year of achievement	2023
Product Milestones | Maximum
Derivative Liability [Abstract]
Milestone liabilities projected year of achievement	2028
Measurement Input, Discount Rate | Technology Milestones
Derivative Liability [Abstract]
Contingent consideration liability measurement input	7.50
Measurement Input, Discount Rate | Product Milestones
Derivative Liability [Abstract]
Contingent consideration liability measurement input	7.50
Probability of Achievement | Technology Milestones | Minimum
Derivative Liability [Abstract]
Contingent consideration liability measurement input	10
Probability of Achievement | Technology Milestones | Maximum
Derivative Liability [Abstract]
Contingent consideration liability measurement input	50
Probability of Achievement | Product Milestones | Minimum
Derivative Liability [Abstract]
Contingent consideration liability measurement input	2
Probability of Achievement | Product Milestones | Maximum
Derivative Liability [Abstract]
Contingent consideration liability measurement input	15

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Marketable securities held, Amortized Cost	$ 321,363	$ 137,509
Marketable securities held, Gross Unrealized Gains	26	13
Marketable securities held, Gross Unrealized Losses	(7)	(22)
Marketable securities held, Fair Value	321,382	137,500
Commercial Paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities held, Amortized Cost	317,303	113,628
Marketable securities held, Gross Unrealized Gains	26	11
Marketable securities held, Gross Unrealized Losses	(5)	(17)
Marketable securities held, Fair Value	317,324	113,622
Corporate Notes
Debt Securities, Available-for-sale [Line Items]
Marketable securities held, Amortized Cost	4,060	7,839
Marketable securities held, Gross Unrealized Gains	0	2
Marketable securities held, Gross Unrealized Losses	(2)	(5)
Marketable securities held, Fair Value	$ 4,058	7,836
U.S. Treasury Securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities held, Amortized Cost		11,009
Marketable securities held, Gross Unrealized Gains		0
Marketable securities held, Gross Unrealized Losses		0
Marketable securities held, Fair Value		11,009
Government Securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities held, Amortized Cost		5,033
Marketable securities held, Gross Unrealized Gains		0
Marketable securities held, Gross Unrealized Losses		0
Marketable securities held, Fair Value		$ 5,033

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Investments Debt And Equity Securities [Abstract]
Realized gains or losses recognized on sale or maturity of marketable securities	$ 0	$ 0
Contractual maturity dates of investments	less than one year

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Employee compensation and related benefits	$ 5,841	$ 7,591
Research costs	4,987	2,423
Professional fees	3,733	1,948
Process development and manufacturing costs	3,285	2,272
Other	5,119	4,229
Total	$ 22,965	$ 18,463

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands

1 Months Ended

3 Months Ended

9 Months Ended

Aug. 31, 2020USD ($)ft²Option

Apr. 30, 2020USD ($)Option

Mar. 31, 2020USD ($)

Jul. 31, 2019

Jun. 30, 2019

Apr. 30, 2019USD ($)Option

Oct. 31, 2018

Feb. 28, 2018USD ($)ft²

Jun. 30, 2021USD ($)

Sep. 30, 2021USD ($)

Sep. 30, 2020USD ($)

Oct. 31, 2021USD ($)

Aug. 31, 2021USD ($)

Jan. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Oct. 31, 2020USD ($)

Lessee Lease Description [Line Items]

Operating lease right-of-use assets

$ 103,169

$ 86,859

Lease liability

139,604

Increase in operating lease liability

15,208

$ (3,249)

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

2019-10

2019-10

2018-03

Operating lease, termination month and year

2021-12

2021-12

2028-09

Operating lease, option to extend

option to extend the lease for two terms of five years each, which are not reasonably certain of exercise.

a term extension option, which is not reasonably certain of exercise.

Operating lease, existence of option to extend

true

Operating lease, number of renewal options | Option

2

Operating lease, option to extend term

5 years

Leasehold improvements landlord allowance

$ 23,400

$ 6,100

Operating lease, termination date

Feb. 28, 2034

Increase in operating lease right-of-use assets

$ 500

Increase in operating lease liability

$ 500

Operating lease term

12 years

Lessee, operating lease, lease not yet commenced anticipated undiscounted lease payments due

$ 2,600

$ 11,100

Office and Laboratory Space | Subsequent Event

Lessee Lease Description [Line Items]

Lessee, operating lease, lease not yet commenced anticipated undiscounted lease payments due

$ 1,900

Office and Laboratory Space | Letter of Credit

Lessee Lease Description [Line Items]

Lessee, operating lease, security deposit

$ 11,800

Office and Laboratory Space | First Phase of Lease in October 2020

Lessee Lease Description [Line Items]

Operating lease, commencement month and year

2020-10

Rent payments beginning month and year

2021-08

Operating lease right-of-use assets

$ 66,800

Lease liability

$ 68,800

Office and Laboratory Space | Second Phase of Lease in January 2021

Lessee Lease Description [Line Items]

Operating lease, commencement month and year

2021-01

Operating lease right-of-use assets

$ 22,000

Lease liability

$ 23,000

Laboratory Space

Lessee Lease Description [Line Items]

Operating lease, commencement month and year

2020-04

2019-04

Operating lease, termination month and year

2025-12

Operating lease, amendment month and year

2020-04

2020-03

Operating lease, option to extend

The amended lease is subject to fixed-rate rent escalations and provided an option to extend the lease for two additional two-year periods through December 31, 2029, which are not reasonably certain of being exercised.

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 right-of-use assets

$ 1,800

$ 4,200

Lease liability

$ 1,800

$ 4,200

Manufacturing Facility | Alexandria Real Estate Equities, Inc.

Lessee Lease Description [Line Items]

Operating lease, existence of option to extend

true

Operating lease, number of renewal options | Option

2

Operating lease, option to extend term

5 years

Manufacturing facility, number of square feet | ft²

100,000

Operating lease term

15 years

Lessee operating lease, description

The lease has a term of 15 years following the commencement date and provides the Company the option to extend the lease term for two five-year terms. It is subject to fixed rate escalation increases and also provides up to $20.0 million for reimbursement of tenant improvements. As the lease had not commenced as of September 30, 2021, the Company has not recorded an operating lease ROU asset or lease liability for this lease in the accompanying condensed consolidated balance sheets.

Lessee, operating lease, lease not yet commenced anticipated undiscounted lease payments due

$ 81,100

Manufacturing Facility | Alexandria Real Estate Equities, Inc. | Maximum

Lessee Lease Description [Line Items]

Leasehold improvements landlord allowance

$ 20,000

Leases - Summary of Operating L

Leases - Summary of Operating Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease costs	$ 4,557	$ 1,644	$ 13,660	$ 4,946
Variable lease costs	588	249	1,162	786
Short-term lease costs	383		761	0
Total	$ 5,528	$ 1,893	$ 15,583	$ 5,732

Leases - Summary of Lease Term

Leases - Summary of Lease Term and Discount Rate (Details)	Sep. 30, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted-average remaining lease term (years)	11 years 4 months 24 days	11 years 6 months
Weighted-average discount rate	7.10%	7.40%

Leases - Summary of Lease Costs

Leases - Summary of Lease Costs Included in Measurement of Lease Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating cash flows used for operating leases	$ 3,058	$ 2,014	$ 7,053	$ 5,132
Operating lease liabilities arising from obtaining ROU assets			$ 24,164	$ 5,795

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Lease Payments of Operating Leases (Details) $ in Thousands	Sep. 30, 2021USD ($)
Operating Lease Liabilities Payments Due [Abstract]
Remainder of 2021	$ 4,159
2022	16,616
2023	17,262
2024	17,787
2025	18,260
Thereafter	132,835
Undiscounted lease payments	206,919
Less: imputed interest	(67,315)
Total operating lease liabilities	$ 139,604

Guide Acquisition - Additional

Guide Acquisition - Additional Information (Details) - USD ($) $ in Thousands	Feb. 23, 2021	Feb. 28, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Value of shares issued for upfront payment of acquisition					$ 120,032
Research and development expense							$ 154,953
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs			$ 318,609	$ 157,785	252,005	$ 188,323
Business combination liability for milestones at fair value			26,960				$ 26,960	$ 0
Common Stock
Business Acquisition [Line Items]
Value of shares issued for upfront payment of acquisition					10
Issuance of common stock from initial public offering/private placement/At-the-Market offering, net of issuance costs			$ 29	$ 18	$ 28	$ 122
Guide Therapeutics, Inc. | Merger Agreement
Business Acquisition [Line Items]
Business Acquisition, merger agreement date	Feb. 23, 2021
Business combination upfront consideration paid in common stock	$ 120,000	$ 120,000
Value of shares issued for upfront payment of acquisition	120,000
Research and development expense	155,000
Business combination liability for milestones at fair value	$ 36,500
Guide Therapeutics, Inc. | Merger Agreement | Common Stock
Business Acquisition [Line Items]
Number of shares issued for upfront payment of acquisition.	1,087,153
Guide Therapeutics, Inc. | Merger Agreement | Technology Milestones | Maximum | Former Stockholders and Optionholders
Business Acquisition [Line Items]
Potential milestone payable in form of common stock	$ 100,000
Guide Therapeutics, Inc. | Merger Agreement | Product Milestones | Maximum | Former Stockholders and Optionholders
Business Acquisition [Line Items]
Potential milestone payable in form of common stock	$ 220,000

Guide Acquisition - Summary of

Guide Acquisition - Summary of Transaction Price Determined and Allocated (Details) - Guide Therapeutics, Inc. - Merger Agreement $ in Thousands	Feb. 23, 2021USD ($)
Transaction price
Fair value of equity instruments issued	$ 120,032
Technology and product contingent consideration liabilities	36,513
Transaction costs	2,531
Total transaction price	159,076
Transaction price allocated
Cash acquired	3,151
Prepaid expenses and other assets	264
Property and equipment	1,835
Other liabilities assumed	(1,427)
Total transaction price	159,076
In-Process Research and Development
Transaction price allocated
Intangible assets	154,953
Assembled Workforce
Transaction price allocated
Intangible assets	$ 300

License Agreements - Harvard Li

License Agreements - Harvard License Agreement - Additional Information (Details) - Harvard	Jun. 10, 2021shares	Sep. 30, 2021USD ($)	May 31, 2021USD ($)
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 twelfth 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 calculation of any amounts owed to Harvard on each rolling 90-day period, commencing one year after the Company’s IPO, with the first success payment becoming due in May 2021.
Success payment due date month and year		2021-05
Success payments due		$ 0	$ 15,000,000
Product development, regulatory approval milestones and royalties recognized		0
Issuance of common stock for success payment liability, Shares | shares	174,825
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payments		$ 5,000,000
Minimum | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success Payments, valuation multiples		5
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payments		$ 105,000,000
Maximum | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success Payments, valuation multiples		40

License Agreements - Harvard _2

License Agreements - Harvard License Agreement - Success Payment Liability (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Harvard
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payment liability	$ 24,700	$ 35,500

License Agreements - Harvard _3

License Agreements - Harvard License Agreement - Change in Fair Value of Success Payment Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Change in fair value of derivative liabilities	$ (35,800)	$ (2,700)	$ 8,400	$ 8,700
Harvard
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Change in fair value of derivative liabilities	$ (17,900)	$ (1,400)	$ 4,200	$ 4,300

License Agreements - Broad Lice

License Agreements - Broad License Agreement - Additional Information (Details) - Broad License Agreement	Jun. 10, 2021shares	Sep. 30, 2021USD ($)	May 31, 2021USD ($)
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 calculation of any amounts owed to Broad Institute on each rolling 90-day period, commencing one year after the Company’s IPO, with the first success payment becoming due in May 2021.
Success payment due date month and year		2021-05
Success payments due		$ 0	$ 15,000,000
Product development, regulatory approval milestones and royalties recognized		0
Issuance of common stock for success payment liability, Shares | shares	174,825
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payments		$ 5,000,000
Minimum | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success Payments, valuation multiples		5
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payments		$ 105,000,000
Maximum | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success Payments, valuation multiples		40

License Agreements - Broad Li_2

License Agreements - Broad License Agreement - Success Payment Liability (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Broad Institute
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Success payment liability	$ 24,900	$ 35,700

License Agreements - Broad Li_3

License Agreements - Broad License Agreement - Change in Fair Value of Success Payment Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Change in fair value of derivative liabilities	$ (35,800)	$ (2,700)	$ 8,400	$ 8,700
Broad Institute
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Change in fair value of derivative liabilities	$ (17,900)	$ (1,300)	$ 4,200	$ 4,400

License Agreements - Editas Lic

License Agreements - Editas License Agreement - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Editas License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development regulatory and commercial milestones recognized	$ 0.1	$ 0.1

License Agreements - Bio Palett

License Agreements - Bio Palette - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended				3 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Jun. 30, 2020	Mar. 31, 2019	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Value of common stock shares issued					$ 318,609	$ 157,785	$ 252,005	$ 188,323
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock shares issued	5,750,000				2,912,557	1,761,285	2,795,700	12,176,471
Value of common stock shares issued					$ 29	$ 18	$ 28	$ 122
Bio Palette License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee paid				$ 500
Bio Palette License Agreement | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock shares issued				16,725
Value of common stock shares issued				$ 100
Bio Palette License Agreement | Bio Palette Patent
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment paid			$ 2,000
Bio Palette License Agreement | Bio Palette Patent | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock shares issued		175,000
Value of common stock shares issued		$ 300

Collaboration and License Agr_2

Collaboration and License Agreements - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended					9 Months Ended		12 Months Ended
	Jul. 31, 2021	Oct. 31, 2020	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Sep. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, value			$ 677,000					$ 677,000		$ 573,000
Common stock, shares issued			68,126,713					68,126,713		58,446,016
Research and development expense			$ 54,623,000			$ 29,825,000		$ 290,306,000	$ 70,728,000
Current portion of deferred revenue			12,822,000					12,822,000		$ 24,000
Long-term portion of deferred revenue			$ 36,820,000					$ 36,820,000		394,000
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued and sold		5,750,000	2,912,557	1,761,285	2,795,700		12,176,471
Prime Medicine Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement rights and obligations, description								The Company had an obligation to issue $5.0 million in shares of its common stock to Prime Medicine, and Prime Medicine had an obligation to issue 5,000,000 shares of its common stock to the Company, should the Company elect to extend the collaboration beyond one year
Obligation to issue common stock value											$ 5,000,000
Obligation to issue common stock shares											5,000,000
Prime Medicine Inc | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued and sold		200,307
Number of common stock received		5,000,000
Prime Medicine Inc | Common Stock Issued
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense						$ 5,000,000			$ 5,000,000
Prime Medicine Inc | Common Stock Received
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense offset amount										$ 100,000
Apellis Pharmaceuticals, Inc
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement description								On June 30, 2021, the Company entered into a master research and collaboration agreement, or the Apellis Agreement, with Apellis Pharmaceuticals, Inc., or Apellis, focused on the use of certain of the Company’s base editing technology to discover new treatments for complement system-driven diseases. Under the terms of the Apellis Agreement, the Company will apply certain of its base editing technology and conduct preclinical research on up to six base editing programs that target specific genes within the complement system in various organs, including the eye, liver, and brain. Apellis will have exclusive rights to license each of the six programs (each an “Opt-In Right”) and will assume responsibility for subsequent development. The Company may elect to enter into a 50-50 U.S. co-development and co-commercialization agreement with Apellis with respect to one program licensed under the collaboration. The collaboration will be managed on an overall basis by an Alliance Steering Committee, or ASC, formed by an equal number of representatives from the Company and Apellis.
Collaboration arrangement, initial term								5 years
Upfront revenue recognized								$ 0
Collaboration agreement upfront payment received	$ 50,000,000
Collaboration agreement performance obligation revenue recognized			$ 800,000					800,000
Collaboration agreement aggregate transaction price				$ 75,000,000
Upfront fee due upon signing contract				50,000,000
Collaboration agreement first anniversary amount due				25,000,000
Current portion of deferred revenue			12,800,000					12,800,000
Long-term portion of deferred revenue			$ 36,400,000					$ 36,400,000
Apellis Pharmaceuticals, Inc | ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract asset				25,000,000
Deferred revenue liability				$ 25,000,000
Apellis Pharmaceuticals, Inc | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration arrangement extension term								2 years

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Details) - USD ($)	Jan. 16, 2021	Jun. 30, 2021	Apr. 30, 2021	Oct. 31, 2020	Feb. 29, 2020	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2021	Jul. 07, 2021	May 10, 2021	Dec. 31, 2020	Jan. 31, 2020
Class Of Stock [Line Items]
Preferred stock, shares authorized						25,000,000				25,000,000			25,000,000	25,000,000
Preferred stock, par value per share						$ 0.01				$ 0.01			$ 0.01	$ 0.01
Common stock, shares authorized						250,000,000				250,000,000			250,000,000	250,000,000
Common stock, par or stated value per share						$ 0.01				$ 0.01			$ 0.01	$ 0.01
Gross proceeds from issuance of common stock				$ 135,100,000
Common stock, voting rights										The holders of the Company’s common stock are entitled to one vote for each share of common stock.
Common Stock
Class Of Stock [Line Items]
Shares issued and sold				5,750,000		2,912,557	1,761,285	2,795,700	12,176,471
Public offering price per share				$ 23.50
Net proceeds from sale of common stock				$ 126,600,000	$ 188,300,000
Issuance of common stock for success payment liability, Shares							349,650
Prime Medicine Inc | Common Stock
Class Of Stock [Line Items]
Shares issued and sold				200,307
Broad Institute
Class Of Stock [Line Items]
Issuance of common stock for success payment liability, Shares		174,825
Success payments liability												$ 15,000,000
Harvard Institute
Class Of Stock [Line Items]
Issuance of common stock for success payment liability, Shares		174,825
Success payments liability												$ 15,000,000
Jeffries LLC Amended Sales Agreement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock										$ 190,500,000
Jeffries LLC Amended Sales Agreement | Common Stock
Class Of Stock [Line Items]
Shares issued and sold										1,765,833
Public offering price per share						$ 107.88				$ 107.88
Jeffries LLC Sales Agreement
Class Of Stock [Line Items]
Stock sold during period shares, new issues										2,908,009
Public offering price per share						$ 103.16				$ 103.16
Gross proceeds from issuance of common stock										$ 300,000,000
Jeffries LLC Sales Agreement and Amended Sales Agreement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock										$ 490,500,000
IPO | Common Stock
Class Of Stock [Line Items]
Shares issued and sold					12,176,471
Public offering price per share					$ 17
Gross proceeds from issuance of common stock					$ 207,000,000
Net proceeds from sale of common stock					$ 188,300,000
Shares issued upon conversion of preferred stock					29,127,523
Underwriters Option | Common Stock
Class Of Stock [Line Items]
Shares issued and sold				750,000	1,588,235
Private Placement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 260,000,000
Private Placement | Common Stock
Class Of Stock [Line Items]
Shares issued and sold	2,795,700
Public offering price per share	$ 93
Net proceeds from sale of common stock	$ 252,000,000
At-The-Market | Jeffries LLC Amended Sales Agreement
Class Of Stock [Line Items]
Aggregate gross proceeds of shares authorized under ATM sales agreement											$ 500,000,000
At-The-Market | Jeffries LLC Sales Agreement | Maximum
Class Of Stock [Line Items]
Aggregate gross proceeds of shares authorized under ATM sales agreement			$ 300,000,000
Commission rate			3.00%

Stock Option and Grant Plan - A

Stock Option and Grant Plan - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended
	Feb. 29, 2020	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value per share of options granted		$ 58.85
Unvested Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to unvested stock options		$ 107,300,000
Unrecognized compensation cost, cost to recognize over a weighted-average period		2 years 4 months 24 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost, cost to recognize over a weighted-average period		2 years 8 months 12 days
Unrecognized stock-based compensation expense, expected to vest		$ 74,500,000
Restricted Stock | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		2 years
Restricted Stock | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
2019 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for future issuance		9,019,805
Number of shares available for future issuance		1,985,950
2019 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance		1,049,460
Common stock, shares description		In February 2020, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Employee Stock Purchase Plan, or ESPP, which was approved by the Company’s stockholders. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee directors, are eligible to purchase common stock of the Company at a reduced rate during offering periods. The ESPP permits participants to purchase common stock using funds contributed through payroll deductions, subject to a calendar year limit of $25,000 and at a purchase price of 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period. The first offering period commenced on October 1, 2021.
Maximum amount allowed to purchase common stock using payroll deduction	$ 25,000
Percentage of common stock purchase price lower of the fair market value	85.00%
Common stock, offering period, start date	Oct. 1, 2021

Stock Option and Grant Plan - S

Stock Option and Grant Plan - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 12,968	$ 3,012	$ 28,068	$ 8,573
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	7,554	1,999	17,049	5,577
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,414	$ 1,013	$ 11,019	$ 2,996

Stock Option and Grant Plan -_2

Stock Option and Grant Plan - Summary of Option Activity Under Equity Award Plans (Details) - $ / shares	9 Months Ended
	Sep. 30, 2021
Number of options
Outstanding at December 31, 2020	5,336,441
Granted	1,638,143
Exercised	(774,352)
Forfeitures	(60,982)
Outstanding at September 30, 2021	6,139,250
Exercisable as of September 30, 2021	2,008,588
Weighted average exercise price
Outstanding at December 31, 2020	$ 9.70
Granted	88.57
Exercised	9.89
Forfeitures	28.53
Outstanding at September 30, 2021	30.53
Exercisable as of September 30, 2021	$ 9.57

Stock Option and Grant Plan -_3

Stock Option and Grant Plan - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Shares
Unvested as of December 31, 2020 | shares	1,275,338
Issued | shares	819,830
Vested | shares	(799,609)
Cancelled | shares	(8,725)
Unvested as of September 30, 2021 | shares	1,286,834
Weighted-average grant date fair value
Unvested as of December 31, 2020 | $ / shares	$ 10.95
Issued | $ / shares	88.13
Vested | $ / shares	4.61
Cancelled | $ / shares	80.04
Unvested as of September 30, 2021 | $ / shares	$ 63.59

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	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share	7,426,084	7,125,688
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	1,286,834	1,492,203
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted net loss per share	6,139,250	5,633,485

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		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss attributable to common stockholders	$ (28,118)	$ (34,452)	$ (305,931)	$ (100,405)
Denominator:
Weighted average number of common shares , basic	66,377,611	50,087,747	62,960,219	43,438,919
Weighted average number of common shares , diluted	66,377,611	50,087,747	62,960,219	43,438,919
Net loss per common share attributable to common stockholders, basic	$ (0.42)	$ (0.69)	$ (4.86)	$ (2.31)
Net loss per common share attributable to common stockholders, diluted	$ (0.42)	$ (0.69)	$ (4.86)	$ (2.31)

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)	1 Months Ended			3 Months Ended	9 Months Ended
	Oct. 31, 2021USD ($)ft²	Oct. 31, 2020USD ($)	Feb. 29, 2020shares	Sep. 30, 2021USD ($)	Sep. 30, 2021USD ($)Foundershares	Sep. 30, 2020USD ($)	Jun. 30, 2021
Related Party Transaction [Line Items]
Number of founder shareholders | Founder					3
Equity securities recognition amount				$ (4,892,000)	$ 21,960,000	$ 517,000
Office and Laboratory Space
Related Party Transaction [Line Items]
Operating lease term							12 years
Founder Shareholders | Scientific Consulting and Other Expenses
Related Party Transaction [Line Items]
Payments received from (made to) related parties				(100,000)	(300,000)
Verve Therapeutics, Inc.
Related Party Transaction [Line Items]
Purchases from related party						300,000
Equity securities recognition amount				(4,900,000)	22,000,000
Equity securities				$ 24,400,000	$ 24,400,000
Income from related party						200,000
Verve Therapeutics, Inc. | Common Stock
Related Party Transaction [Line Items]
Number of shares purchased under equity method | shares			546,970		546,970
Verve Therapeutics, Inc. | Office and Laboratory Space | Subsequent Event
Related Party Transaction [Line Items]
Sublease area of rented space | ft²	12,000
Operating lease term	1 year
Sublease, commencement month and year	2021-12
Rental payment over term of sublease	$ 1,400,000
Verve Therapeutics, Inc. | Research and Development Expense
Related Party Transaction [Line Items]
Purchases from related party					$ 200,000
Verve Therapeutics, Inc. | Series A Preferred Stock Shares
Related Party Transaction [Line Items]
Purchases from related party						800,000
Unrealized gains on investment						$ 500,000
Reimbursed Costs | Prime Agreement | Interest and Other Income (Expense), Net | Prime Medicine Inc
Related Party Transaction [Line Items]
Income from related party		$ 30,000			$ 100,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ in Millions	1 Months Ended
	Oct. 31, 2021USD ($)
Subsequent Event | Sana Biotechnology | Option and License Agreement
Subsequent Event [Line Items]
Upfront payment under term of agreement	$ 50