Allogene Therapeutics (ALLO) 10-Q 5 Aug 20 2020 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-38693
Entity Registrant Name	Allogene Therapeutics, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-3562771
Entity Address, Address Line One	210 East Grand Avenue
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	457-2700
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	ALLO
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		139,291,518
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Entity Central Index Key	0001737287
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	[1]
Current assets:
Cash and cash equivalents	$ 280,379	$ 175,126
Short-term investments	619,271	355,407
Prepaid expenses and other current assets	9,927	14,043
Total current assets	909,577	544,576
Long-term investments	210,794	58,322
Operating lease right-of-use asset	42,432	44,495
Property and equipment, net	84,605	56,449
Intangible assets, net	0	151
Restricted cash	4,299	4,299
Other long-term assets	2,160	4,618
Equity method investment	4,677	4,892
Total assets	1,258,544	717,802
Current liabilities:
Accounts payable	9,057	9,250
Accrued and other current liabilities	31,838	23,829
Total current liabilities	40,895	33,079
Lease liability, noncurrent	51,067	51,349
Other long-term liabilities	3,163	4,351
Total liabilities	95,125	88,779
Commitments and Contingencies (Notes 6 and 7)
Stockholders’ equity:
Preferred stock, $0.001 par value: 10,000,000 shares authorized as of June 30, 2020 and December 31, 2019; no shares were issued and outstanding as of June 30, 2020 and December 31, 2019	0	0
Common stock, $0.001 par value: 200,000,000 shares authorized as of June 30, 2020 and December 31, 2019; 139,233,450 and 124,267,358 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively	139	124
Additional paid-in capital	1,673,026	1,023,876
Accumulated deficit	(511,576)	(396,122)
Accumulated other comprehensive income	1,830	1,145
Total stockholders’ equity	1,163,419	629,023
Total liabilities and stockholders’ equity	$ 1,258,544	$ 717,802
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	139,233,450	124,267,358
Common stock, shares outstanding (in shares)	139,233,450	124,267,358

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development	$ 47,296,000	$ 31,774,000	$ 89,337,000	$ 55,177,000
General and administrative	15,862,000	14,187,000	31,502,000	27,245,000
Total operating expenses	63,158,000	45,961,000	120,839,000	82,422,000
Loss from operations	(63,158,000)	(45,961,000)	(120,839,000)	(82,422,000)
Other income (expense), net:
Interest and other income, net	2,340,000	4,559,000	5,600,000	9,384,000
Other expenses	(156,000)	0	(215,000)	0
Total other income (expense), net	2,184,000	4,559,000	5,385,000	9,384,000
Loss before income taxes	(60,974,000)	(41,402,000)	(115,454,000)	(73,038,000)
Benefit from income taxes	0	159,000	0	209,000
Net loss	(60,974,000)	(41,243,000)	(115,454,000)	(72,829,000)
Other comprehensive income:
Net unrealized gain on available-for-sale investments	220,000	756,000	685,000	1,855,000
Net comprehensive loss	$ (60,754,000)	$ (40,487,000)	$ (114,769,000)	$ (70,974,000)
Net loss per share, basic and diluted (in dollars per share)	$ (0.53)	$ (0.41)	$ (1.03)	$ (0.74)
Weighted-average number of shares used in computing net loss per share, basic and diluted (in shares)	115,377,210	99,846,946	112,163,123	98,588,410

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total		ATM offering	Public offering	Common Stock	Common StockATM offering	Common StockPublic offering	Additional Paid-in Capital	Additional Paid-in CapitalATM offering	Additional Paid-in CapitalPublic offering	Accumulated Deficit	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2018					121,482,671
Beginning balance at Dec. 31, 2018	$ 703,164				$ 121			$ 914,265			$ (211,528)	$ 306
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and vesting of RSU's (in shares)					103,958
Issuance of common stock upon exercise of stock options and vesting of RSUs	237				$ 1			236
Vesting of early exercised common stock	3,170							3,170
Stock-based compensation	19,354							19,354
Employee stock purchase plan (in shares)					44,649
Employee stock purchase plan	684							684
Net loss	(72,829)										(72,829)
Net unrealized gain on available-for-sale investments	1,855											1,855
Ending balance (in shares) at Jun. 30, 2019					121,631,278
Ending balance at Jun. 30, 2019	655,635				$ 122			937,709			(284,357)	2,161
Beginning balance (in shares) at Mar. 31, 2019					121,527,320
Beginning balance at Mar. 31, 2019	681,228				$ 121			922,816			(243,114)	1,405
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and vesting of RSU's (in shares)					103,958
Issuance of common stock upon exercise of stock options and vesting of RSUs	237				$ 1			236
Vesting of early exercised common stock	3,170							3,170
Stock-based compensation	11,487							11,487
Net loss	(41,243)										(41,243)
Net unrealized gain on available-for-sale investments	756											756
Ending balance (in shares) at Jun. 30, 2019					121,631,278
Ending balance at Jun. 30, 2019	$ 655,635				$ 122			937,709			(284,357)	2,161
Beginning balance (in shares) at Dec. 31, 2019	124,267,358				124,267,358
Beginning balance at Dec. 31, 2019	$ 629,023	[1]			$ 124			1,023,876			(396,122)	1,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and vesting of RSU's (in shares)					853,241
Issuance of common stock upon exercise of stock options and vesting of RSUs	4,780				$ 1			4,779
Vesting of early exercised common stock	1,419							1,419
Stock-based compensation	30,985							30,985
Employee stock purchase plan (in shares)					84,565
Employee stock purchase plan	1,438							1,438
Issuance of common stock from public offering (in shares)						570,839	13,457,447
Issuance of common stock from public offering			$ 14,845	$ 595,698		$ 1	$ 13		$ 14,844	$ 595,685
Net loss	(115,454)										(115,454)
Net unrealized gain on available-for-sale investments	$ 685											685
Ending balance (in shares) at Jun. 30, 2020	139,233,450				139,233,450
Ending balance at Jun. 30, 2020	$ 1,163,419				$ 139			1,673,026			(511,576)	1,830
Beginning balance (in shares) at Mar. 31, 2020					125,262,537
Beginning balance at Mar. 31, 2020	606,519				$ 125			1,055,386			(450,602)	1,610
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and vesting of RSU's (in shares)					513,466
Issuance of common stock upon exercise of stock options and vesting of RSUs	4,476				$ 1			4,475
Vesting of early exercised common stock	710							710
Stock-based compensation	16,770							16,770
Issuance of common stock from public offering (in shares)					13,457,447
Issuance of common stock from public offering	595,698				$ 13			595,685
Net loss	(60,974)										(60,974)
Net unrealized gain on available-for-sale investments	$ 220											220
Ending balance (in shares) at Jun. 30, 2020	139,233,450				139,233,450
Ending balance at Jun. 30, 2020	$ 1,163,419				$ 139			$ 1,673,026			$ (511,576)	$ 1,830
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders’ Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
ATM offering
Statement of Stockholders' Equity [Abstract]
Issuance costs		$ 0.3
Issuance costs		0.3
Public offering
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 36.8	36.8
Issuance costs	$ 36.8	$ 36.8

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (115,454)	$ (72,829)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	30,985	19,354
Amortization of other intangible assets acquired	151	301
Depreciation and amortization	3,781	1,543
Net amortization/accretion on investment securities	20	(2,285)
Non-cash rent expense	1,060	1,548
Benefit from income taxes	0	(209)
Share of losses from equity method investments	215	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	4,116	(521)
Other long-term assets	2,458	(1,993)
Accounts payable	(503)	1,332
Accrued and other current liabilities	6,829	(107)
Other long-term liabilities	(1,188)	(1,282)
Net cash used in operating activities	(67,530)	(55,148)
Cash flows from investing activities:
Purchases of property and equipment	(28,307)	(18,279)
Proceeds from sales of investments	4,877	0
Proceeds from maturities of investments	221,633	197,415
Purchase of investments	(642,181)	(101,756)
Net cash (used in) provided by investing activities	(443,978)	77,380
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options	4,780	236
Proceeds from issuance of common stock under the employee stock purchase plan	1,438	684
Net cash provided by financing activities	616,761	920
Net change in cash, cash equivalents and restricted cash	105,253	23,152
Cash, cash equivalents and restricted cash — beginning of period	179,425	93,731
Cash, cash equivalents and restricted cash — end of period	284,678	116,883
Non-cash investing activities:
Property and equipment purchases in accounts payable and accrued liabilities	8,298	13,667
Supplemental disclosure:
Cash paid for amounts included in the measurement of lease liabilities	2,816	1,156
Cash received for amounts related to tenant improvement allowances	1,617	0
ATM offering
Cash flows from financing activities:
Proceeds from issuance of common stock, net of commissions and issuance costs	14,845	0
Public offering
Cash flows from financing activities:
Proceeds from issuance of common stock, net of commissions and issuance costs	$ 595,698	$ 0

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Allogene Therapeutics, Inc. (the Company or Allogene) was incorporated on November 30, 2017, in the State of Delaware and is headquartered in South San Francisco, California. Allogene is a clinical-stage immuno-oncology company pioneering the development and commercialization of genetically engineered allogeneic T cell therapies for the treatment of cancer. The Company is developing a pipeline of off-the-shelf T cell product candidates that are designed to target and kill cancer cells. Public Offerings In November 2019, the Company entered into a sales agreement with Cowen and Company, LLC (Cowen), under which the Company may from time to time issue and sell shares of its common stock through Cowen in at-the-market (ATM) offerings for an aggregate offering price of up to $250.0 million. The aggregate compensation payable to Cowen as the Company's sales agent equals up to 3.0% of the gross sales price of the shares sold through it pursuant to the sales agreement. In January 2020, the Company sold an aggregate of 570,839 shares of common stock in ATM offerings resulting in net proceeds of $14.8 million. In June 2020, the Company sold 13,457,447 shares of its common stock, which included 1,755,319 shares sold pursuant to the full exercise of the underwriters' option to purchase additional shares, in an underwritten public offering at a price of $47.00 per share, which resulted in gross proceeds of approximately $632.5 million. Net proceeds to the Company after deducting the underwriting discounts and commissions and other expenses were approximately $595.7 million. Need for Additional Capital The Company has sustained operating losses and expects to continue to generate operating losses for the foreseeable future. The Company’s ultimate success depends on the outcome of its research and development activities. The Company had cash and cash equivalents and investments of $1.1 billion as of June 30, 2020. Since inception through June 30, 2020, the Company has incurred cumulative net losses of $511.6 million. Management expects to incur additional losses in the future to fund its operations and conduct product research and development and recognizes the need to raise additional capital to fully implement its business plan. The Company intends to raise additional capital through the issuance of equity securities, debt financings or other sources in order to further implement its business plan. However, if such financing is not available when needed and at adequate levels, the Company will need to reevaluate its operating plan and may be required to delay the development of its product candidates. The Company expects that its cash and cash equivalents and investments will be sufficient to fund its operations for a period of at least one year from the date the accompanying unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (SEC).

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the SEC. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the results of operations and cash flows for the periods presented have been included. In June 2020, the Company formed a wholly-owned Netherlands-based subsidiary, Allogene Therapeutics, B.V., to help prepare for and assist with the Company's activities in Europe. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All material intercompany balances and transactions have been eliminated during consolidation. The condensed consolidated balance sheet as of June 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed consolidated statements of stockholders’ equity as of June 30, 2020 and 2019, the condensed consolidated statements of cash flows for the six months ended June 30, 2020 and 2019, and the financial data and other financial information disclosed in the notes to the condensed consolidated financial statements are unaudited. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020, or for any other future annual or interim period. These condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2019, included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2020. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include but are not limited to the fair value of stock options, income tax uncertainties, and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Significant Accounting Policies There have been no significant changes to the accounting policies during the three and six months ended June 30, 2020, as compared to the significant accounting policies described in Note 1 of the “Notes to Financial Statements” in the Company’s audited financial statements included in its Annual Report, with the exception of the recently adopted accounting pronouncements in the section below. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires measurement and recognition of expected credit losses for financial assets by requiring an allowance to be recorded as an offset to the amortized cost of such assets. For available-for-sale debt securities, expected credit losses should be estimated when the fair value of the debt securities is below their associated amortized costs. This standard is effective for fiscal years beginning after December 15, 2019, with early adoption permitted beginning the first quarter of 2019. The Company’s financial instruments that are in the scope of ASU 2016-13 include, but are not limited to, other receivables and available-for-sale debt securities. The Company adopted this standard on January 1, 2020 and applied the modified retrospective approach. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-15, Intangibles – Goodwill and other – Internal-Use Software (Subtopic 350-40) , which amended its guidance for costs of implementing a cloud computing service arrangement and aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This new standard also requires customers to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. The guidance is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company adopted this standard on January 1, 2020, on a prospective basis for applicable implementation costs. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606 when the counterparty is a customer. In addition, Topic 808 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. The Company adopted this standard on January 1, 2020. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In December 2019, the FASB issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12) , which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. This guidance will be effective for the Company in the first quarter of 2021 on a prospective basis, and early adoption is permitted. The Company early adopted this standard as of January 1, 2020 on a prospective basis in accordance with ASC 250, Accounting Changes and Error Corrections. The adoption resulted in the Company no longer needing to determine the tax effect from unrealized gains on available for sale securities, which previously had been disclosed in the condensed consolidated statement of operations as a benefit from income taxes. The impact of the adoption in the three and six months ended June 30, 2020 is that the benefit from income taxes in the condensed consolidated statement of operations and comprehensive loss is zero for both periods compared to recognition of a $0.2 million and $0.2 million tax benefit for the three and six months ended June 30, 2019, respectively. Recent Accounting Pronouncements Not Yet Adopted In January 2020, the FASB issued Accounting Standard Update No. 2020-01, Investments – Equity Securities (Topic 321), Investments – Equity Method and Joint Ventures (Topic 323) , which clarifies the interactions between topics 321 and 323 in applying or discontinuing the equity method of accounting for investments. This guidance will be effective for the Company in the first quarter of 2021, and early adoption is permitted. The Company is currently evaluating the impact of the new guidance on the consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures and reports its cash equivalents, restricted cash, and investments at fair value. Money market funds are measured at fair value on a recurring basis using quoted prices and are classified as Level 1. Investments are measured at fair value based on inputs other than quoted prices that are derived from observable market data and are classified as Level 2 inputs except for investments in U.S treasury securities which are classified as Level 1. There were no Level 3 assets or liabilities as of June 30, 2020 and as of December 31, 2019. Financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of June 30, 2020 and as of December 31, 2019 are presented in the following tables: June 30, 2020 Level 1 Level 2 Level 3 Fair Value (in thousands) Financial Assets: Money market funds (1) $ 256,773 $ — $ — $ 256,773 Commercial paper — 79,910 — 79,910 Corporate bonds — 292,055 — 292,055 U.S. treasury securities 423,486 — — 423,486 U.S. agency securities — 34,614 — 34,614 Total financial assets $ 680,259 $ 406,579 $ — $ 1,086,838 December 31, 2019 Level 1 Level 2 Level 3 Fair Value (in thousands) Financial Assets: Money market funds (1) $ 122,900 $ — $ — $ 122,900 Corporate bonds — 205,011 — 205,011 U.S. treasury securities 181,894 — — 181,894 U.S. agency securities — 25,824 — 25,824 Certificates of deposit — 1,000 — 1,000 Total financial assets $ 304,794 $ 231,835 $ — $ 536,629 (1) Included within cash and cash equivalents on the Company’s condensed consolidated balance sheets

Financial Instruments

Financial Instruments	6 Months Ended
	Jun. 30, 2020
Investments, All Other Investments [Abstract]
Financial Instruments	Financial Instruments The fair value and amortized cost of cash equivalents and available-for-sale securities by major security type as of June 30, 2020 and as of December 31, 2019 are presented in the following tables: June 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 256,773 $ — $ — $ 256,773 Commercial paper 79,822 90 (2) 79,910 Corporate bonds 290,898 1,205 (48) 292,055 U.S. treasury securities 422,592 907 (13) 423,486 U.S. agency securities 34,479 137 (2) 34,614 Total cash equivalents and investments $ 1,084,564 $ 2,339 $ (65) $ 1,086,838 Classified as: Cash equivalents $ 256,773 Short-term investments 619,271 Long-term investments 210,794 Total cash equivalents and investments $ 1,086,838 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 122,900 $ — $ — $ 122,900 Corporate bonds 204,144 871 (4) 205,011 U.S. treasury securities 181,340 557 (3) 181,894 U.S. agency securities 25,658 167 (1) 25,824 Certificates of deposit 1,000 — — 1,000 Total cash equivalents and investments $ 535,042 $ 1,595 $ (8) $ 536,629 Classified as: Cash equivalents $ 122,900 Short-term investments 355,407 Long-term investments 58,322 Total cash equivalents and investments $ 536,629 As of June 30, 2020, the remaining contractual maturities of available-for-sale securities were less than 3 years. There have been no significant realized losses on available-for-sale securities for the periods presented. As of June 30, 2020, unrealized losses on available-for-sale investments are not attributed to credit risk. The Company believes that it is more-likely-than-not that investments in an unrealized loss position will be held until maturity and all interest and principal will be received. The Company believes that an allowance for credit losses is unnecessary because the unrealized losses on certain of the Company’s marketable securities are due to market factors. To date, the Company has not recorded any impairment charges on marketable securities.

Balance Sheets Components

Balance Sheets Components	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheets Components	Balance Sheets Components Property and Equipment Property and Equipment consist of the following: June 30, December 31, (In thousands) Construction in progress $ 36,963 $ 12,390 Leasehold improvements 31,519 29,924 Laboratory equipment 18,813 13,117 Computers equipment and purchased software 3,783 3,726 Furniture and fixtures 2,780 2,764 Total 93,858 61,921 Less: accumulated depreciation (9,253) (5,472) Total property and equipment, net $ 84,605 $ 56,449

License Agreements

License Agreements	6 Months Ended
	Jun. 30, 2020
Research and Development [Abstract]
License Agreements	License Agreements Asset Contribution Agreement with Pfizer In April 2018, the Company entered into an Asset Contribution Agreement (the Pfizer Agreement) with Pfizer pursuant to which the Company acquired certain assets, including certain contracts and intellectual property for the development and administration of chimeric antigen receptor (CAR) T cells for the treatment of cancer. The Company is required to make milestone payments upon successful completion of regulatory and sales milestones on a target-by-target basis for the targets including CD19 and B-cell maturation antigen (BCMA), covered by the Pfizer Agreement. The aggregate potential milestone payments upon successful completion of various regulatory milestones in the United States and the European Union are $30.0 million or $60.0 million, depending on the target, with aggregate potential regulatory and development milestones of up to $840.0 million, provided that the Company is not obligated to pay a milestone for regulatory approval in the European Union for an anti-CD19 allogeneic CAR T cell product, to the extent Servier has commercial rights to such territory. The aggregate potential milestone payments upon reaching certain annual net sales thresholds in North America, Europe, Asia, Australia and Oceania (the Territory) for a certain number of targets covered by the Pfizer Agreement are $325.0 million per target. The sales milestones in the foregoing sentence are payable on a country-by-country basis until the last to expire of any Pfizer Royalty Term, as described below, for any product in such country in the Territory. In October 2019, the Territory was expanded to all countries in the world. No milestone or royalty payments were made in the three months ended June 30, 2020 and 2019 respectively. Pfizer is also eligible to receive, on a product-by-product and country-by-country basis, royalties in single-digit percentages on annual net sales for products covered by the Pfizer Agreement or that use certain Pfizer intellectual property and for which an investigational new drug application (IND) is first filed on or before April 6, 2023. The Company’s royalty obligation with respect to a given product in a given country begins upon the first sale of such product in such country and ends on the later of (i) expiration of the last claim of any applicable patent or (ii) 12 years from the first sale of such product in such country. Research Collaboration and License Agreement with Cellectis As part of the Pfizer Agreement, Pfizer assigned to the Company a Research Collaboration and License Agreement (the Original Cellectis Agreement) with Cellectis S.A. (Cellectis). On March 8, 2019, the Company entered into a License Agreement (the Cellectis Agreement) with Cellectis. In connection with the execution of the Cellectis Agreement, on March 8, 2019, the Company and Cellectis also entered into a letter agreement (the Letter Agreement), pursuant to which the Company and Cellectis agreed to terminate the Original Cellectis Agreement. The Original Cellectis Agreement included a research collaboration to conduct discovery and pre-clinical development activities to generate CAR T cells directed at targets selected by each party, which was completed in June 2018. Pursuant to the Cellectis Agreement, Cellectis granted to the Company an exclusive, worldwide, royalty-bearing license, on a target-by-target basis, with sublicensing rights under certain conditions, under certain of Cellectis’s intellectual property, including its TALEN and electroporation technology, to make, use, sell, import, and otherwise exploit and commercialize CAR T products directed at certain targets, including BCMA, FLT3, DLL3 and CD70 (the Allogene Targets), for human oncologic therapeutic, diagnostic, prophylactic and prognostic purposes. In addition, certain Cellectis intellectual property rights granted by Cellectis to the Company and to Servier pursuant to the Exclusive License and Collaboration Agreement by and between Servier and Pfizer, dated October 30, 2016, which Pfizer assigned to the Company in April 2018, will survive the termination of the Original Cellectis Agreement. Pursuant to the Cellectis Agreement, the Company granted Cellectis a non-exclusive, worldwide, royalty-free, perpetual and irrevocable license, with sublicensing rights under certain conditions, under certain of the Company's intellectual property, to make, use, sell, import and otherwise commercialize CAR T products directed at certain targets (the Cellectis Targets). The Cellectis Agreement provides for development and sales milestone payments by the Company of up to $185.0 million per product that is directed against an Allogene Target, with aggregate potential development and sales milestone payments totaling up to $2.8 billion. Cellectis is also eligible to receive tiered royalties on annual worldwide net sales of any products that are commercialized by the Company that contain or incorporate, are made using or are claimed or covered by, Cellectis intellectual property licensed to the Company under the Cellectis Agreement (the Allogene Products), at rates in the high single-digit percentages. Such royalties may be reduced, on a licensed product-by-licensed product and country-by-country basis, for generic entry and for payments due under licenses of third party patents. Pursuant to the Cellectis Agreement, and subject to certain exceptions, the Company is required to indemnify Cellectis against all third party claims related to the development, manufacturing, commercialization or use of any Allogene Product or arising out of the Company’s material breach of the representations, warranties or covenants set forth in the Cellectis Agreement, and Cellectis is required, subject to certain exceptions, to indemnify the Company against all third party claims related to the development, manufacturing, commercialization or use of CAR T products directed at Cellectis Targets or arising out of Cellectis’s material breach of the representations, warranties or covenants set forth in the Cellectis Agreement. The royalties are payable, on a licensed product-by-licensed product and country-by-country basis, until the later of (i) the expiration of the last to expire of the licensed patents covering such product; (ii) the loss of regulatory exclusivity afforded such product in such country, and (iii) the tenth anniversary of the date of the first commercial sale of such product in such country; however, in no event shall such royalties be payable, with respect to a particular licensed product, past the twentieth anniversary of the first commercial sale for such product. Depending on the Cellectis Target, the Company has a right of first refusal or right of first negotiation to purchase or license from Cellectis rights to develop and commercialize products against such Cellectis Targets. Under the Cellectis Agreement, the Company has certain diligence obligations to progress the development of CAR T product candidates and to commercialize one CAR T product per Allogene Target in one major market country where the Company has received regulatory approval. If the Company materially breaches any of its diligence obligations and fails to cure within 90 days, then with respect to certain targets, such target will cease to be an Allogene Target and instead will become a Cellectis Target. Unless earlier terminated in accordance with its terms, the Cellectis Agreement will expire on a product-by-product and country-by-country basis, upon expiration of all royalty payment obligations with respect to such licensed product in such country. The Company has the right to terminate the Cellectis Agreement at will upon 60 days’ prior written notice, either in its entirety or on a target-by-target basis. Either party may terminate the Cellectis Agreement, in its entirety or on a target-by-target basis, upon 90 days’ prior written notice in the event of the other party’s uncured material breach. The Cellectis Agreement may also be terminated by the Company upon written notice at any time in the event that Cellectis becomes bankrupt or insolvent or upon written notice within 60 days of a consummation of a change of control of Cellectis. All costs the Company incurred in connection with this agreement were recognized as research and development expenses. For the three and six months ended June 30, 2020 and 2019, zero costs were incurred related to the achievement of a clinical development milestone under this agreement. For the three and six months ended June 30, 2020 and 2019, zero costs were incurred associated with research services performed by Cellectis under this agreement. License and Collaboration Agreement with Servier As part of the Pfizer Agreement, Pfizer assigned to the Company an Exclusive License and Collaboration Agreement (the Servier Agreement), with Les Laboratoires Servier SAS and Institut de Recherches Internationales Servier SAS (collectively, Servier) to develop, manufacture and commercialize certain allogeneic anti-CD19 CAR T cell product candidates, including UCART19, in the United States with the option to obtain the rights over additional anti-CD19 product candidates and for allogeneic CAR T cell product candidates directed against one additional target. In October 2019, the Company agreed to waive its rights to the one additional target. Under the Servier Agreement, the Company has an exclusive license to develop, manufacture and commercialize UCART19 in the field of anti-tumor adoptive immunotherapy in the United States, with an exclusive option to obtain the same rights for additional product candidates in the United States and, if Servier does not elect to pursue development or commercialization of those product candidates in certain markets outside of the United States pursuant to its license, outside of the United States as well. The Company is not required to make any additional payments to Servier to exercise an option. If the Company opts-in to another product candidate, Servier has the right to obtain rights to such product candidate outside the United States and to share development costs for such product candidate. Under the Servier Agreement, the Company is required to use commercially reasonable efforts to develop and obtain marketing approval in the United States in the field of anti-tumor adoptive immunotherapy for at least one product directed against CD19, and Servier is required to use commercially reasonable efforts to develop and obtain marketing approval in the European Union, and one other country in a group of specified countries outside of the European Union and the United States, in the field of anti-tumor adoptive immunotherapy for at least one allogeneic adaptive T cell product directed against a certain Company-selected target. For product candidates that the Company is co-developing with Servier, including UCART19, ALLO-501 and ALLO-501A, the Company is responsible for 60% of the specified development costs and Servier is responsible for the remaining 40% of the specified development costs under the applicable global research and development plan. Subject to certain restrictions, each party has the right to conduct activities that are specific to its territory outside the global research and development plan at such party’s sole expense. In addition, each party is solely responsible for commercialization activities in its territory at such party’s sole expense. The Company is required to make milestone payments to Servier upon successful completion of regulatory and sales milestones. The Servier Agreement provides for aggregate potential payments by the Company to Servier of up to $137.5 million upon successful completion of various regulatory milestones, and aggregate potential payments by the Company to Servier of up to $78.0 million upon successful completion of various sales milestones. Similarly, Servier is required to make milestone payments upon successful completion of regulatory and sales milestones for products directed at the Allogene-target covered by the Servier Agreement that achieves such milestones. The total potential payments that Servier is obligated to make to the Company under the Servier Agreement upon successful completion of regulatory and sales milestones are $42.0 million and €70.5 million ($79.1 million), respectively. The foregoing milestones are subject to certain adjustments if the Company obtains rights for certain products outside of the United States upon Servier’s election not to pursue such rights. Each party is also eligible to receive tiered royalties on annual net sales in countries within the paying party’s respective territory of any licensed products that are commercialized by such party that are directed at the targets licensed by such party under the Servier Agreement. The royalty rates are in a range from the low tens to the high teen percentages. Such royalties may be reduced for interchangeable drug entry, expiration of patent rights and amounts paid pursuant to licenses of third-party patents. The royalty obligation for each party with respect to a given licensed product in a given country in each party’s respective territory (the Servier Royalty Term) begins upon the first commercial sale of such product in such country and ends after a defined number of years. Unless earlier terminated in accordance with the Servier Agreement, the Servier Agreement will continue, on a licensed product-by-licensed product and country-by-country basis, until the Servier Royalty Term with respect to the sale of such licensed product in such country expires. For the three and six months ended June 30, 2020, the Company recorded $0.9 million and $1.9 million, respectively, of net cost recoveries under the cost-sharing terms of the Servier Agreement as a reduction to research and development expenses. For the three and six months ended June 30, 2019, the Company recorded $2.4 million and $3.1 million, respectively, of costs as research and development expenses. As of June 30, 2020, amounts due from Servier of $0.8 million were recorded in other current assets in the accompanying condensed consolidated balance sheets. As of December 31, 2019, amounts due to Servier of $2.2 million were recorded in accrued and other current liabilities in the accompanying condensed consolidated balance sheets. Research Collaboration and License Agreement with Notch On November 1, 2019, the Company entered into a Collaboration and License Agreement (the Notch Agreement) with Notch Therapeutics Inc. (Notch), pursuant to which Notch granted to Allogene an exclusive, worldwide, royalty-bearing, sublicensable license under certain of Notch’s intellectual property to develop, make, use, sell, import, and otherwise commercialize therapeutic gene-edited T cell and/or natural killer (NK) cell products from induced pluripotent stem cells directed at certain CAR targets for initial application in non-Hodgkin lymphoma, acute lymphoblastic leukemia and multiple myeloma. In addition, Notch has granted Allogene an option to add certain specified targets to its exclusive license in exchange for an agreed per-target option fee. The Notch Agreement includes a research collaboration to conduct research and pre-clinical development activities to generate engineered cells directed to Allogene’s exclusive targets, which will be conducted in accordance with an agreed research plan and budget under the oversight of a joint development committee. Allogene will reimburse Notch’s costs incurred in accordance with such plan and budget. The term of the research collaboration will expire upon the earlier of (i) the fifth anniversary of the date of the Notch Agreement, (ii) at Allogene’s election, following the joint development committee’s determination that for each exclusive target, Notch has met certain success criteria, or (iii) the joint development committee’s determination that the research collaboration cannot be reasonably pursued against any exclusive target due to technical infeasibility or safety issues. In connection with the execution of the Notch Agreement, Allogene made an upfront payment to Notch of $10.0 million in return for a license to access Notch's technology in order to conduct research pursuant to the Notch Agreement. The Company recognized a research and development expense of $10 million during the year ended December 31, 2019 as the license had no foreseeable alternative future use. In addition, Allogene made a $5.0 million investment in Notch’s series seed convertible preferred stock, resulting in Allogene having a 25% ownership interest in Notch’s outstanding capital stock on a fully diluted basis immediately following the investment. In connection with this investment, David Chang, M.D., Ph.D., the Company's President, Chief Executive Officer and Board member, was appointed to Notch’s Board of Directors. Under the Notch Agreement, Notch will be eligible to receive up to $7.25 million upon achieving certain agreed research milestones, up to $4.0 million per exclusive target upon achieving certain pre-clinical development milestones, and up to $283.0 million per exclusive target and cell type (i.e., T cell or NK cell) upon achieving certain clinical, regulatory and commercial milestones. Notch is also entitled to receive tiered royalties in the mid to high single digit range on Allogene’s sales of licensed products, subject to certain reductions, for a term, on a country-by-country and product-by-product basis, commencing on first commercial sale of such product in such country and continuing until the latest of (i) the date upon which there is no valid claim of the licensed patents in such country of sale that covers such product, (ii) the expiration of applicable data or other regulatory exclusivity in such country of sale or (iii) a defined period from the first commercial sale of such product in such country. The terms of the Notch Agreement will continue on a product-by-product and country-by-country basis until Allogene’s payment obligations with respect to such product in such country have expired. Following such expiration, Allogene’s license with respect to such product and country shall be perpetual, irrevocable, fully paid up and royalty-free. Allogene may terminate the Collaboration Agreement in whole or on a product-by-product basis upon ninety days’ prior written notice to Notch. Either party may also terminate the Collaboration Agreement with written notice upon material breach by the other party, if such breach has not been cured within a defined period of receiving such notice, or in the event of the other party’s insolvency. The Company has determined that Notch continues to be a variable interest entity as of June 30, 2020. The Company does not have the power to direct the activities which most significantly affect Notch's economic performance. Accordingly, for the three and six months ended June 30, 2020, the Company did not consolidate Notch because the Company determined that it was not the primary beneficiary.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases In August 2018, the Company entered into an operating lease agreement for new office and laboratory space which consists of approximately 68,000 square feet located in South San Francisco, California. The lease term is 127 months beginning August 2018 through February 2029 with an option to extend the term for another seven years which is not reasonably assured of exercise. The Company has made certain tenant improvements, including the addition of laboratory space, and has received $5.0 million of tenant improvement allowances up to June 30, 2020. The rent payments began on March 1, 2019 after an abatement period. In October 2018, the Company entered into an operating lease agreement for new office and laboratory space which consists of 14,943 square feet located in South San Francisco, California. The lease term is 124 months beginning November 2018 through February 2029, with an option to extend the term for another seven years which is not reasonably assured of exercise. The Company has made certain tenant improvements, including the upgrading of current office and laboratory space with a lease incentive allowance of $0.8 million. Rent payments began in November 2018. In February 2019, the Company entered into a lease agreement for approximately 118,000 square feet of space to develop a cell therapy manufacturing facility in Newark, California. The lease has a term of 188 months and is expected to commence in October 2020. Upon certain conditions, the Company has two ten-year options to extend the lease which are not reasonably assured of exercise. Rent payments are expected to begin in early 2021 after an abatement period. The Company is entitled to a tenant improvement allowance of $2.9 million for costs related to the design and construction of certain Company improvements. The Company maintained letters of credit for the benefit of landlords in the amount of $4.3 million which is disclosed as restricted cash as of June 30, 2020 and December 31, 2019, respectively. The balance sheet classification of our lease liabilities were as follows (in thousands): June 30, 2020 December 31, 2019 Operating lease liabilities Current portion included in accrued and other current liabilities $ 2,395 $ 1,679 Long-term portion of lease liabilities 51,067 51,349 Total operating lease liabilities $ 53,462 $ 53,028 The components of lease costs for operating leases, which were recognized in operating expenses, were as follows (in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Operating lease cost $ 1,868 $ 1,354 $ 3,736 $ 2,705 Variable lease cost 399 263 608 401 Total lease costs $ 2,267 $ 1,617 $ 4,344 $ 3,106 Cash paid for amounts included in the measurement of lease liabilities for the six months ended June 30, 2020 was $2.8 million and was included in net cash used in operating activities in our condensed consolidated statements of cash flows. The undiscounted future lease payments under the lease agreements as of June 30, 2020 were as follows (in thousands): Year ending December 31: 2020 (remaining 6 months) $ 2,846 2021 6,813 2022 7,927 2023 8,178 2024 8,440 2025 and thereafter 56,294 Total undiscounted lease payments 90,498 Less: Present value adjustment (34,311) Less: Tenant improvement allowance (2,725) Total $ 53,462 Operating lease liabilities are based on the net present value of the remaining lease payments over the remaining lease term. In determining the present value of lease payments, we use our estimated incremental borrowing rate. The weighted average discount rate used to determine the operating lease liability was 8.35%. As of June 30, 2020, the weighted average remaining lease term for our operating leases is 10.4 years. Other Commitments The Company has entered into certain license agreements for intellectual property which is used as part of our development and manufacturing processes. Each of these respective agreements are generally cancellable by the Company. These agreements require payment of annual license fees and may include conditional milestone payments for achievement of specific research, clinical and commercial events, and royalty payments. The timing and likelihood of any significant conditional milestone payments or royalty payments becoming due was not probable as of June 30, 2020. The Company enters into contracts in the normal course of business that includes arrangements with clinical research organizations, vendors for preclinical research and vendors for manufacturing. These agreements generally allow for cancellation with notice. As of June 30, 2020, the Company had non-cancellable purchase commitments of $5.6 million.

Equity Method Investment

Equity Method Investment	6 Months Ended
	Jun. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	Equity Method Investment In conjunction with the execution of the Notch Agreement (see Note 6), the Company also entered into a Share Purchase Agreement with the Company acquiring shares of Notch’s Series Seed convertible preferred stock for a total investment cost of $5.1 million which includes transaction costs of $0.1 million, resulting in a 25% ownership interest in Notch. The Company’s total equity investment in Notch as of June 30, 2020 and December 31, 2019 was $4.7 million and $4.9 million, respectively, and the Company accounted for the investment using the equity method of accounting. During the three and six months ended June 30, 2020, the Company recognized its share of Notch's net loss under the other expenses caption within the condensed consolidated statements of operations. The Company's share of Notch's net loss was $0.1 million and $0.2 million for the three and six months ended June 30, 2020.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation In June 2018, the Company adopted the 2018 Equity Incentive Plan (2018 Plan). The 2018 Plan provided for the Company to sell or issue common stock or restricted common stock, or to grant incentive stock options or nonqualified stock options for the purchase of common stock, to employees, members of the Company’s Board of Directors and consultants of the Company under terms and provisions established by the Company’s Board of Directors. In October 2018, the Board of Directors approved an amendment and restatement of the 2018 Plan, increasing the shares of common stock issuable under the 2018 Plan as well as allowing for an automatic annual increase to the shares issuance under the 2018 Plan to the amount equal to 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year. The term of any stock option granted under the 2018 Plan cannot exceed 10 years. The Company generally grants stock-based awards with service conditions only. Options shall not have an exercise price less than 100% of the fair market value of the Company’s common stock on the grant date. Options granted typically vest over a four-year period but may be granted with different vesting terms. Restricted Stock Units granted typically vest annually over a four-year period but may be granted with different vesting terms. As of June 30, 2020, there were 12,562,263 shares reserved by the Company under the 2018 Plan for the future issuance of equity awards. Stock Option Activity The following summarizes option activity under the 2018 Plan: Outstanding Options Number of Options Weighted- Average Exercise Price Weighted- Aggregate intrinsic value (in years) (in thousands) Balance, December 31, 2019 9,190,522 $ 14.51 8.82 $ 110,490 Granted 2,896,287 20.01 Exercised (498,406) 9.89 Forfeited (536,964) 11.97 Balance, June 30, 2020 11,051,439 $ 16.28 8.59 $ 293,934 Exercisable, June 30, 2020 6,474,921 $ 14.24 8.45 $ 184,688 Vested and expected to vest, June 30, 2020 11,051,439 $ 16.28 8.59 $ 293,934 The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on the Nasdaq Global Select Market on June 30, 2020. For the six months ended June 30, 2020, the estimated weighted-average grant-date fair value of employee options granted was $20.01 per share. As of June 30, 2020, there was $91.8 million of unrecognized stock-based compensation related to unvested stock options, which is expected to be recognized over a weighted-average period of 2 years, 336 days. The fair value of employee, consultant and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Six Months Ended June 30, 2020 2019 Expected term in years 5.31 - 6.09 5.99 - 6.25 Expected volatility 71.42% - 72.14% 74.84% Expected risk-free interest rate 0.38% - 1.65% 2.45% - 2.62% Expected dividend 0% 0% Expected term — The expected term represents the period that stock-based awards are expected to be outstanding. The expected term for option grants is determined using the simplified method. The simplified method deems the term to be the average of the time-to-vesting and the contractual life of the stock-based awards. Expected volatility — The Company uses an average historical stock price volatility of comparable public companies within the biotechnology and pharmaceutical industry that were deemed to be representative of future stock price trends as the Company does not have sufficient trading history for its common stock. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Risk-free interest rate —The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option. Expected dividend —The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero. Restricted Stock Unit Activity The following summarizes restricted stock unit activity under the 2018 Plan: Outstanding Restricted Stock Units Restricted Stock Units Weighted- Average Fair Value at Date of Grant per Share Weighted Average Remaining Vesting Life Aggregate Intrinsic Value (in years) (in thousands) Unvested December 31, 2019 1,941,155 $ 27.45 1.98 $50,431 Granted 1,042,799 21.71 2.19 Vested (383,730) 27.28 Forfeited (108,515) 24.93 Unvested June 30, 2020 2,491,709 $ 25.18 2.03 $106,695 Vested and expected to vest, June 30, 2020 2,491,709 $ 25.18 2.03 $106,695 As of June 30, 2020, there was $55.1 million of unrecognized stock-based compensation related to unvested restricted stock units, which is expected to be recognized over a weighted-average period of 3 years, 55 days. Total stock-based compensation related to stock options, restricted stock units, employee stock purchase plan and vesting of the founders’ common stock was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 7,979 $ 4,747 $ 14,636 $ 7,478 General and administrative 8,791 6,740 16,349 11,876 Total stock-based compensation $ 16,770 $ 11,487 $ 30,985 $ 19,354 Early Exercised Options The Company allows certain of its employees and its directors to exercise options granted under the 2018 Plan prior to vesting. The shares related to early exercised stock options are subject to the Company’s lapsing repurchase right upon termination of employment or service on the Company’s board of directors at the lesser of the original purchase price or fair market value at the time of repurchase. In order to vest, the holders are required to provide continued service to the Company. The proceeds are initially recorded in accrued and other liabilities for the current portion, and other long-term liabilities for the non-current portion. The proceeds are reclassified to paid-in capital as the repurchase right lapses. As of June 30, 2020 and December 31, 2019 there was $2.8 million and $2.8 million recorded in accrued and other liabilities and $2.5 million and $3.9 million recorded in other long-term liabilities related to shares held by employees and directors that were subject to repurchase. The underlying shares are shown as outstanding in the condensed consolidated financial statements since the exercise date but the shares which are subject to future vesting conditions are not included in the calculation of earnings per share.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions As of June 30, 2020, Pfizer held 22,032,040 shares of Common Stock and had appointed one member to the Company’s board of directors. In April 2018, the Company and Pfizer entered into a transition services agreement (the Pfizer TSA) for Pfizer to provide professional services to the Company related to research and development, project management, and other administrative functions. In September 2019, the Company and Pfizer terminated the Pfizer TSA. For the three and six months ended June 30, 2020, the costs incurred under the Pfizer TSA were zero. For the three and six months ended June 30, 2019, the costs incurred under the Pfizer TSA were $1.8 million and $4.2 million, respectively. The Company also purchased certain lab supplies from Pfizer in connection with its research and development activities. For the three and six months ended June 30, 2020, the total lab supplies and services purchased from Pfizer were zero. For the three and six months ended June 30, 2019, the total lab supplies and services purchased from Pfizer were $0.4 million and $1.0 million, respectively. As of June 30, 2020 and December 31, 2019, the Company had an amount payable to Pfizer of zero and $1.7 million, respectively, which was recorded in the accrued and other current liabilities on the accompanying condensed consolidated balance sheets. Sublease Agreement In December 2018, the Company entered into a sublease with Bellco Capital LLC (Bellco) for 1,293 square feet of office space in Los Angeles, California for a three In February 2019, the Company subleased 2,180 square feet of its office space in New York, New York, to ByHeart, Inc. (ByHeart), formerly known as Second Science, Inc. ByHeart is a development-stage infant formula company. Certain of the Company’s board members and executive officers have beneficial ownership in ByHeart and two serve on the board of directors of ByHeart. In September 2019, the Company entered into an amendment to the sublease agreement and increased the subleased space to 2,907 square feet. Sublease income for the three and six months ended June 30, 2020 were $0.1 million and $0.2 million, respectively, and was recognized as other income. Sublease income for the three and six months ended June 30, 2019 was $0.1 million and $0.1 million, respectively. Consulting Agreements In June 2018, the Company entered into a services agreement with Two River Consulting LLC (Two River) a firm affiliated with the Company’s President and Chief Executive Officer, the Company’s Executive Chairman of the board of directors, and a director of the Company to provide various managerial, administrative, accounting and financial services to the Company. The costs incurred for services provided under this agreement were $0.1 million and $0.2 million for the three and six months ended June 30, 2020, respectively, and $0.1 million and $0.3 million for the three and six months ended June 30, 2019, respectively. In August 2018, the Company entered into a consulting agreement with Bellco. Pursuant to the consulting agreement, Bellco provides certain services for the Company, which are performed by Dr. Belldegrun and include without limitation, providing advice and analysis with respect to the Company’s business, business strategy and potential opportunities in the field of allogeneic CAR T cell therapy and any other aspect of the CAR T cell therapy business as the Company may agree. In consideration for these services, the Company paid Bellco $33,333 per month in arrears commencing January 2019 and $37,500 per month in arrears commencing January 2020. The Company may also, at its discretion, pay Bellco an annual performance award in an amount up to 60% of the aggregate compensation payable to Bellco in a calendar year. The Company also reimburses Bellco for out of pocket expenses incurred in performing the services. The cost incurred for services provided and out-of-pocket expenses incurred under this consulting agreement were $0.2 million and $0.4 million for the three and six months ended June 30, 2020, respectively, and $0.1 million and $0.3 million for the three and six months ended June 30, 2019, respectively.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesThe Company has a history of losses, and expects to record a loss in 2020. The Company continues to maintain a full valuation allowance against its net deferred tax assets.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the period presented due to their anti-dilutive effect: June 30, 2020 2019 Stock options to purchase common stock 11,051,439 9,287,848 Restricted stock units subject to vesting 2,491,709 1,433,582 Expected shares to be purchased under Employee Stock Purchase Plan 207,129 176,722 Founder's shares of common stock subject to future vesting 10,600,961 16,658,645 Early exercised stock options subject to future vesting 2,364,712 3,619,869 Total 26,715,950 31,176,666

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsIn July 2020, the Company entered into a Solar Power Purchase and Energy Services Agreement with Onyx Development Group LLC (Onyx) for the installation and operation of a solar photovoltaic generating system and battery energy storage system at the Company's cell therapy manufacturing facility in Newark, California. The agreement has a term of 20 years and is expected to commence in the first quarter of 2021. The Company is obligated to pay for electricity generated from the system at an agreed rate for the duration of the agreement term. Termination of the agreement by the Company will result in a termination payment due of approximately $4.3 million. In connection with the agreement, the Company will maintain a letter of credit for the benefit of Onyx in the amount of $4.3 million and increased the letter of credit for the benefit of the landlord of the Newark manufacturing facility by $0.9 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the SEC. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the Company’s opinion, all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation of the results of operations and cash flows for the periods presented have been included. In June 2020, the Company formed a wholly-owned Netherlands-based subsidiary, Allogene Therapeutics, B.V., to help prepare for and assist with the Company's activities in Europe. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All material intercompany balances and transactions have been eliminated during consolidation. The condensed consolidated balance sheet as of June 30, 2020, the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2020 and 2019, the condensed consolidated statements of stockholders’ equity as of June 30, 2020 and 2019, the condensed consolidated statements of cash flows for the six months ended June 30, 2020 and 2019, and the financial data and other financial information disclosed in the notes to the condensed consolidated financial statements are unaudited. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results to be expected for the year ending December 31, 2020, or for any other future annual or interim period. These condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2019, included in the Company’s Annual Report on Form 10-K filed with the SEC on February 27, 2020.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include but are not limited to the fair value of stock options, income tax uncertainties, and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Significant Accounting Policies	Significant Accounting Policies There have been no significant changes to the accounting policies during the three and six months ended June 30, 2020, as compared to the significant accounting policies described in Note 1 of the “Notes to Financial Statements” in the Company’s audited financial statements included in its Annual Report, with the exception of the recently adopted accounting pronouncements in the section below.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments and also issued subsequent amendments to the initial guidance: ASU 2018-19, ASU 2019-04, ASU 2019-05, and ASU 2019-11. The standard requires measurement and recognition of expected credit losses for financial assets by requiring an allowance to be recorded as an offset to the amortized cost of such assets. For available-for-sale debt securities, expected credit losses should be estimated when the fair value of the debt securities is below their associated amortized costs. This standard is effective for fiscal years beginning after December 15, 2019, with early adoption permitted beginning the first quarter of 2019. The Company’s financial instruments that are in the scope of ASU 2016-13 include, but are not limited to, other receivables and available-for-sale debt securities. The Company adopted this standard on January 1, 2020 and applied the modified retrospective approach. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In August 2018, the FASB issued Accounting Standards Update No. 2018-15, Intangibles – Goodwill and other – Internal-Use Software (Subtopic 350-40) , which amended its guidance for costs of implementing a cloud computing service arrangement and aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This new standard also requires customers to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. The guidance is effective for fiscal years beginning after December 15, 2019, with early adoption permitted. The Company adopted this standard on January 1, 2020, on a prospective basis for applicable implementation costs. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 , which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606 when the counterparty is a customer. In addition, Topic 808 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. The Company adopted this standard on January 1, 2020. Adoption of the new guidance had no significant impact on the Company’s consolidated financial statements. In December 2019, the FASB issued Accounting Standards Update No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes (ASU 2019-12) , which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. This guidance will be effective for the Company in the first quarter of 2021 on a prospective basis, and early adoption is permitted. The Company early adopted this standard
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In January 2020, the FASB issued Accounting Standard Update No. 2020-01, Investments – Equity Securities (Topic 321), Investments – Equity Method and Joint Ventures (Topic 323) , which clarifies the interactions between topics 321 and 323 in applying or discontinuing the equity method of accounting for investments. This guidance will be effective for the Company in the first quarter of 2021, and early adoption is permitted. The Company is currently evaluating the impact of the new guidance on the consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Financial Assets And Liabilities Subject To Fair Value Measurements On Recurring Basis And Level Of Inputs Used In Such Measurements By Major Security Type	Financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements by major security type as of June 30, 2020 and as of December 31, 2019 are presented in the following tables: June 30, 2020 Level 1 Level 2 Level 3 Fair Value (in thousands) Financial Assets: Money market funds (1) $ 256,773 $ — $ — $ 256,773 Commercial paper — 79,910 — 79,910 Corporate bonds — 292,055 — 292,055 U.S. treasury securities 423,486 — — 423,486 U.S. agency securities — 34,614 — 34,614 Total financial assets $ 680,259 $ 406,579 $ — $ 1,086,838 December 31, 2019 Level 1 Level 2 Level 3 Fair Value (in thousands) Financial Assets: Money market funds (1) $ 122,900 $ — $ — $ 122,900 Corporate bonds — 205,011 — 205,011 U.S. treasury securities 181,894 — — 181,894 U.S. agency securities — 25,824 — 25,824 Certificates of deposit — 1,000 — 1,000 Total financial assets $ 304,794 $ 231,835 $ — $ 536,629 (1) Included within cash and cash equivalents on the Company’s condensed consolidated balance sheets

Financial Instruments (Tables)

Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2020
Investments, All Other Investments [Abstract]
Schedule of Fair Value and Amortized Cost	The fair value and amortized cost of cash equivalents and available-for-sale securities by major security type as of June 30, 2020 and as of December 31, 2019 are presented in the following tables: June 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 256,773 $ — $ — $ 256,773 Commercial paper 79,822 90 (2) 79,910 Corporate bonds 290,898 1,205 (48) 292,055 U.S. treasury securities 422,592 907 (13) 423,486 U.S. agency securities 34,479 137 (2) 34,614 Total cash equivalents and investments $ 1,084,564 $ 2,339 $ (65) $ 1,086,838 Classified as: Cash equivalents $ 256,773 Short-term investments 619,271 Long-term investments 210,794 Total cash equivalents and investments $ 1,086,838 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Fair Value (in thousands) Money market funds $ 122,900 $ — $ — $ 122,900 Corporate bonds 204,144 871 (4) 205,011 U.S. treasury securities 181,340 557 (3) 181,894 U.S. agency securities 25,658 167 (1) 25,824 Certificates of deposit 1,000 — — 1,000 Total cash equivalents and investments $ 535,042 $ 1,595 $ (8) $ 536,629 Classified as: Cash equivalents $ 122,900 Short-term investments 355,407 Long-term investments 58,322 Total cash equivalents and investments $ 536,629

Balance Sheets Components (Tabl

Balance Sheets Components (Tables)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment	Property and Equipment consist of the following: June 30, December 31, (In thousands) Construction in progress $ 36,963 $ 12,390 Leasehold improvements 31,519 29,924 Laboratory equipment 18,813 13,117 Computers equipment and purchased software 3,783 3,726 Furniture and fixtures 2,780 2,764 Total 93,858 61,921 Less: accumulated depreciation (9,253) (5,472) Total property and equipment, net $ 84,605 $ 56,449

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of Lease Liabilities	The balance sheet classification of our lease liabilities were as follows (in thousands): June 30, 2020 December 31, 2019 Operating lease liabilities Current portion included in accrued and other current liabilities $ 2,395 $ 1,679 Long-term portion of lease liabilities 51,067 51,349 Total operating lease liabilities $ 53,462 $ 53,028
Schedule of Lease Costs	The components of lease costs for operating leases, which were recognized in operating expenses, were as follows (in thousands): Three Months Ended Six Months Ended 2020 2019 2020 2019 Operating lease cost $ 1,868 $ 1,354 $ 3,736 $ 2,705 Variable lease cost 399 263 608 401 Total lease costs $ 2,267 $ 1,617 $ 4,344 $ 3,106
Summary of Future Lease Payments Under Lease Liability	The undiscounted future lease payments under the lease agreements as of June 30, 2020 were as follows (in thousands): Year ending December 31: 2020 (remaining 6 months) $ 2,846 2021 6,813 2022 7,927 2023 8,178 2024 8,440 2025 and thereafter 56,294 Total undiscounted lease payments 90,498 Less: Present value adjustment (34,311) Less: Tenant improvement allowance (2,725) Total $ 53,462

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Summary of Stock Option Activity Under Plan	The following summarizes option activity under the 2018 Plan: Outstanding Options Number of Options Weighted- Average Exercise Price Weighted- Aggregate intrinsic value (in years) (in thousands) Balance, December 31, 2019 9,190,522 $ 14.51 8.82 $ 110,490 Granted 2,896,287 20.01 Exercised (498,406) 9.89 Forfeited (536,964) 11.97 Balance, June 30, 2020 11,051,439 $ 16.28 8.59 $ 293,934 Exercisable, June 30, 2020 6,474,921 $ 14.24 8.45 $ 184,688 Vested and expected to vest, June 30, 2020 11,051,439 $ 16.28 8.59 $ 293,934
Schedule Stock Option Valuation Assumptions	The fair value of employee, consultant and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Six Months Ended June 30, 2020 2019 Expected term in years 5.31 - 6.09 5.99 - 6.25 Expected volatility 71.42% - 72.14% 74.84% Expected risk-free interest rate 0.38% - 1.65% 2.45% - 2.62% Expected dividend 0% 0%
Schedule of Restricted Stock Units Activity Under Plan	The following summarizes restricted stock unit activity under the 2018 Plan: Outstanding Restricted Stock Units Restricted Stock Units Weighted- Average Fair Value at Date of Grant per Share Weighted Average Remaining Vesting Life Aggregate Intrinsic Value (in years) (in thousands) Unvested December 31, 2019 1,941,155 $ 27.45 1.98 $50,431 Granted 1,042,799 21.71 2.19 Vested (383,730) 27.28 Forfeited (108,515) 24.93 Unvested June 30, 2020 2,491,709 $ 25.18 2.03 $106,695 Vested and expected to vest, June 30, 2020 2,491,709 $ 25.18 2.03 $106,695
Schedule of Stock-Based Compensation Expense	Total stock-based compensation related to stock options, restricted stock units, employee stock purchase plan and vesting of the founders’ common stock was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 7,979 $ 4,747 $ 14,636 $ 7,478 General and administrative 8,791 6,740 16,349 11,876 Total stock-based compensation $ 16,770 $ 11,487 $ 30,985 $ 19,354

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Shares	The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share for the period presented due to their anti-dilutive effect: June 30, 2020 2019 Stock options to purchase common stock 11,051,439 9,287,848 Restricted stock units subject to vesting 2,491,709 1,433,582 Expected shares to be purchased under Employee Stock Purchase Plan 207,129 176,722 Founder's shares of common stock subject to future vesting 10,600,961 16,658,645 Early exercised stock options subject to future vesting 2,364,712 3,619,869 Total 26,715,950 31,176,666

Description of Business (Detail

Description of Business (Details) - USD ($)	1 Months Ended		3 Months Ended
	Jun. 30, 2020	Jan. 31, 2020	Jun. 30, 2020	Dec. 31, 2019		Nov. 30, 2019
Subsidiary, Sale of Stock [Line Items]
Stock issuance, maximum value						$ 250,000,000
Stock issuance, maximum compensation due to third party, percent				3.00%
Issuance of common stock (in shares)		570,839
Stock issues during period, value	$ 595,700,000	$ 14,800,000	$ 595,698,000
Shares sold in transaction (in shares)	13,457,447
Offering price (in dollars per share)	$ 47		$ 47
Gross proceeds from sale of stock	$ 632,500,000
Cash and cash equivalents and marketable securities	1,100,000,000		$ 1,100,000,000
Accumulated deficit	$ 511,576,000		$ 511,576,000	$ 396,122,000	[1]
Underwriters' Option
Subsidiary, Sale of Stock [Line Items]
Shares sold in transaction (in shares)	1,755,319
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accounting Policies [Abstract]
Benefit from income taxes	$ 0	$ 159,000	$ 0	$ 209,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - Fair Value, Measurements, Recurring - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 1,086,838,000	$ 536,629,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Financial liabilities	$ 0	$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities (Detail) - Fair Value, Measurements, Recurring - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 1,086,838,000	$ 536,629,000
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	256,773,000	122,900,000
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	79,910,000
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	292,055,000	205,011,000
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	423,486,000	181,894,000
U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	34,614,000	25,824,000
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets		1,000,000
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	680,259,000	304,794,000
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	256,773,000	122,900,000
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0
Level 1 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 1 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	423,486,000	181,894,000
Level 1 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 1 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	406,579,000	231,835,000
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	79,910,000
Level 2 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	292,055,000	205,011,000
Level 2 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 2 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	34,614,000	25,824,000
Level 2 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets		1,000,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0
Level 3 | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | U.S. agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 0	0
Level 3 | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets		$ 0

Financial Instruments - Cash Eq

Financial Instruments - Cash Equivalents, Restricted Cash and Investments, Classified as Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,084,564	$ 535,042
Unrealized Gains	2,339	1,595
Unrealized Losses	(65)	(8)
Cash equivalents	256,773	122,900
Short-term investments	619,271	355,407	[1]
Long-term investments	210,794	58,322	[1]
Total cash equivalents and investments	1,086,838	536,629
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	256,773	122,900
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	256,773	122,900
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	79,822	204,144
Unrealized Gains	90	871
Unrealized Losses	(2)	(4)
Fair Value	79,910	205,011
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	290,898	181,340
Unrealized Gains	1,205	557
Unrealized Losses	(48)	(3)
Fair Value	292,055	181,894
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	422,592	25,658
Unrealized Gains	907	167
Unrealized Losses	(13)	(1)
Fair Value	423,486	25,824
U.S. agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	34,479
Unrealized Gains	137
Unrealized Losses	(2)
Fair Value	$ 34,614
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		1,000
Unrealized Gains		0
Unrealized Losses		0
Fair Value		$ 1,000
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Financial Instruments - Additio

Financial Instruments - Additional Information (Details)	Jun. 30, 2020
Investments, All Other Investments [Abstract]
Maximum remaining contractual maturities of available-for-sale securities (in years)	3 years

Balance Sheets Components (Deta

Balance Sheets Components (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 93,858	$ 61,921
Less: accumulated depreciation	(9,253)	(5,472)
Total property and equipment, net	84,605	56,449	[1]
Construction in progress
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	36,963	12,390
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	31,519	29,924
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	18,813	13,117
Computers equipment and purchased software
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	3,783	3,726
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 2,780	$ 2,764
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

License Agreements (Details)

License Agreements (Details) € in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)		Jun. 30, 2020EUR (€)	Nov. 01, 2019USD ($)
Related Party Transaction [Line Items]
Research and development	$ 47,296,000	$ 31,774,000	$ 89,337,000	$ 55,177,000
Accrued and other current liabilities	31,838,000		31,838,000		$ 23,829,000	[1]
Equity method investment	4,677,000		4,677,000		4,892,000	[1]
Research and development
Related Party Transaction [Line Items]
Collaboration arrangement, expense	400,000		700,000
Notch Therapeutics, Inc.
Related Party Transaction [Line Items]
Equity method investment	$ 4,700,000		$ 4,700,000		4,900,000			$ 5,000,000
Ownership percentage	25.00%		25.00%				25.00%	25.00%
Pfizer
Related Party Transaction [Line Items]
Royalty obligation period from date of first sale			12 years
Pfizer | Asset Contribution Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			$ 325,000,000
Aggregate potential milestone payments	$ 0	0
Pfizer | Asset Contribution Agreement | Minimum
Related Party Transaction [Line Items]
Aggregate potential milestone payments	30,000,000
Pfizer | Asset Contribution Agreement | Maximum
Related Party Transaction [Line Items]
Aggregate potential milestone payments	60,000,000
Aggregate potential regulatory and development milestones	840,000,000
Cellectis | Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Maximum payments required per product against selected target			185,000,000
Cellectis | Research Services | Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Research and development	0	0	0	0
Cellectis | Pre-Clinical Development Milestone | Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Research and development	0	$ 0	0	$ 0
Cellectis | Development and Sales | Maximum | Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			2,800,000,000
Servier | License and Collaboration Agreement
Related Party Transaction [Line Items]
Research and development	2,400,000		$ 3,100,000
Percentage of development costs payable by the Company			60.00%
Percentage of development cost payable by collaboration partner			40.00%
Recovery of research and development expense	900,000		$ 1,900,000
Receivables	800,000		800,000
Accrued and other current liabilities					2,200,000
Servier | Regulatory Milestone | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone receivable	42,000,000		42,000,000
Servier | Regulatory Milestone | Maximum | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			137,500,000
Servier | Sales Milestone | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone receivable	79,100,000		79,100,000				€ 70.5
Servier | Sales Milestone | Maximum | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			78,000,000
Notch Therapeutics, Inc. | Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payable	$ 7,250,000		7,250,000
Notch Therapeutics, Inc. | License and Collaboration Agreement
Related Party Transaction [Line Items]
Research and development					$ 10,000,000
Collaboration agreement, upfront payment								$ 10,000,000
Notch Therapeutics, Inc. | Pre-Clinical Development Milestone | Maximum | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			4,000,000
Notch Therapeutics, Inc. | Clinical, Regulatory, and Commercial Milestone | Maximum | License and Collaboration Agreement
Related Party Transaction [Line Items]
Aggregate potential milestone payments			$ 283,000,000
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended	6 Months Ended
	Feb. 28, 2019USD ($)ft²renewal	Jun. 30, 2020USD ($)	Dec. 31, 2019USD ($)	Oct. 31, 2018USD ($)ft²	Aug. 31, 2018ft²
Operating Leased Assets [Line Items]
Area of office and laboratory (in square feet) | ft²				14,943	68,000
Operating lease term				124 months	127 months
Operating lease, option to extend term (in years)				7 years	7 years
Tenant Improvements		$ 5,000
Allowance for tenant improvements		2,725		$ 800
Letter of credit		4,300	$ 4,300
Cash paid for amounts included in measurement of lease liabilities		$ 2,800
Weighted average discount rate, percent		8.35%
Weighted average remaining lease term (in years)		10 years 4 months 24 days
Non-cancellable purchase commitments		$ 5,600
Newark
Operating Leased Assets [Line Items]
Operating lease term	188 months
Operating lease, option to extend term (in years)	10 years
Allowance for tenant improvements	$ 2,900
Area of operating lease (in square feet) | ft²	118,000
Number of options to extend lease | renewal	2

Commitments and Contingencies_2

Commitments and Contingencies - Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Current portion included in accrued and other current liabilities	$ 2,395	$ 1,679
Long-term portion of lease liabilities	51,067	51,349	[1]
Total operating lease liabilities	$ 53,462	$ 53,028
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Commitments and Contingencies_3

Commitments and Contingencies - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 1,868	$ 1,354	$ 3,736	$ 2,705
Variable lease cost	399	263	608	401
Total lease costs	$ 2,267	$ 1,617	$ 4,344	$ 3,106

Commitments and Contingencies_4

Commitments and Contingencies - Undiscounted Future Lease Payments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Oct. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
2020 (remaining 6 months)	$ 2,846
2021	6,813
2022	7,927
2023	8,178
2024	8,440
2025 and thereafter	56,294
Total undiscounted lease payments	90,498
Less: Present value adjustment	(34,311)
Less: Tenant improvement allowance	(2,725)		$ (800)
Total operating lease liabilities	$ 53,462	$ 53,028

Equity Method Investment (Detai

Equity Method Investment (Details) - USD ($) $ in Thousands	Nov. 01, 2019	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity method investment		$ 4,677	$ 4,677		$ 4,892	[1]
Share of losses from equity method investments			$ 215	$ 0
Notch Therapeutics, Inc.
Schedule of Equity Method Investments [Line Items]
Payments to acquire interest in Notch	$ 5,100
Transaction cost	$ 100
Ownership percentage	25.00%	25.00%	25.00%
Equity method investment	$ 5,000	$ 4,700	$ 4,700		$ 4,900
Share of losses from equity method investments		$ 100	$ 200
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares as percentage of common shares outstanding	5.00%
Number of shares reserved for future issuance (in shares)	12,562,263
Accrued and other liabilities, related to shares held by employees and directors that were subject to repurchase	$ 2.8	$ 2.8
Other long term liabilities, related to shares held by employees and directors that were subject to repurchase	$ 2.5	$ 3.9
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	4 years
Stock options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period, weighted average grant date fair value (in dollars per share)	$ 20.01
Unrecognized stock based compensation expense	$ 91.8
Unrecognized stock based compensation expense, weighted average recognition period (in years)	2 years 336 days
Restricted Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	4 years
Unrecognized stock based compensation expense	$ 55.1
Unrecognized stock based compensation expense, weighted average recognition period (in years)	3 years 55 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option grant period (in years)	10 years
Option exercise price as percentage of fair value of common stock on grate date	100.00%

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - 2018 Plan $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of Options
Number of options, beginning balance (in shares) | shares	9,190,522
Number of options, options granted (in shares) | shares	2,896,287
Number of options, options exercised (in shares) | shares	(498,406)
Number of options, options forfeited (in shares) | shares	(536,964)
Number of options, ending balance (in shares) | shares	11,051,439	9,190,522
Number of options, exercisable (in shares) | shares	6,474,921
Number of options, vested and expected to vest (in shares) | shares	11,051,439
Weighted- Average Exercise Price
Weighted-average exercise price, beginning balance (in dollars per share) | $ / shares	$ 14.51
Weighted-average exercise price, options granted (in dollars per share) | $ / shares	20.01
Weighted-average exercise price, options exercised (in dollars per share) | $ / shares	9.89
Weighted-average exercise price, options forfeited (in dollars per share) | $ / shares	11.97
Weighted-average exercise price, ending balance (in dollars per share) | $ / shares	16.28	$ 14.51
Weighted-average exercise price, exercisable (in dollars per share) | $ / shares	14.24
Weighted-average exercise price, vested and expected to vest (in dollars per share) | $ / shares	$ 16.28
Weighted-average remaining contract term, outstanding (in years)	8 years 7 months 2 days	8 years 9 months 25 days
Weighted-average remaining contract term, exercisable (in years)	8 years 5 months 12 days
Weighted-average remaining contract term, vested and expected to vest (in years)	8 years 7 months 2 days
Aggregate intrinsic value, balance | $	$ 293,934	$ 110,490
Aggregate intrinsic value, exercisable | $	184,688
Aggregate intrinsic value, vested and expected to vest | $	$ 293,934

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions (Details) - 2018 Plan	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility		74.84%
Expected risk-free interest rate, minimum	0.38%	2.45%
Expected risk-free interest rate, maximum	1.65%	2.62%
Expected dividend	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term in years	5 years 3 months 21 days	5 years 11 months 26 days
Expected volatility	71.42%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term in years	6 years 1 month 2 days	6 years 3 months
Expected volatility	72.14%

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Stock Units Activity (Details) - Restricted Stock Unit - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Restricted Stock Units
Restricted stock units, unvested, beginning balance (in shares)	1,941,155
Restricted stock units, granted (in shares)	1,042,799
Restricted stock units, vested (in shares)	(383,730)
Restricted stock units, forfeited (in shares)	(108,515)
Restricted stock units, unvested, ending balance (in shares)	2,491,709	1,941,155
Restricted stock units, vested and expected to vest (in shares)	2,491,709
Weighted- Average Fair Value at Date of Grant per Share
Weighted-average fair value at date of grant per share, beginning balance (in dollars per share)	$ 27,450
Weighted-average fair value at date of grant per share, granted (in dollars per share)	21.71
Weighted-average fair value at date of grant per share, vested (in dollars per share)	27.28
Weighted-average fair value at date of grant per share, forfeited (in dollars per share)	24.93
Weighted-average fair value at date of grant per share, ending balance (in dollars per share)	25.18	$ 27,450
Weighted-average fair value at date of grant per share, vested and expected to vest (in dollars per share)	$ 25.18
Weighted average remaining vesting life, unvested (in years)	2 years 10 days	1 year 11 months 23 days
Weighted average remaining vesting life, granted (in years)	2 years 2 months 8 days
Weighted average remaining vesting life, vested and expected to vest (in years)	2 years 10 days
Aggregate intrinsic value, unvested	$ 106,695	$ 50,431
Aggregate intrinsic value, vested and expected to vest	$ 106,695

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	$ 16,770	$ 11,487	$ 30,985	$ 19,354
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	7,979	4,747	14,636	7,478
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation	$ 8,791	$ 6,740	$ 16,349	$ 11,876

Related Party Transactions (Det

Related Party Transactions (Details)	1 Months Ended				3 Months Ended		6 Months Ended
	Sep. 30, 2019ft²	Feb. 28, 2019ft²	Dec. 31, 2018ft²	Aug. 31, 2018USD ($)	Jun. 30, 2020USD ($)board_membershares	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)board_membershares	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)shares
Related Party Transaction [Line Items]
Common stock, shares outstanding (in shares) | shares					139,233,450		139,233,450		124,267,358
Operating lease right-of-use asset					$ 42,432,000		$ 42,432,000		$ 44,495,000	[1]
Operating lease liability					$ 53,462,000		$ 53,462,000		53,028,000
Pfizer
Related Party Transaction [Line Items]
Common stock, shares outstanding (in shares) | shares					22,032,040		22,032,040
Pfizer | Accrued and Other Current Liabilities
Related Party Transaction [Line Items]
Payable to related party, current					$ 0		$ 0		1,700,000
Pfizer | Transition Services Agreement
Related Party Transaction [Line Items]
Related party costs					0	$ 1,800,000	0	$ 4,200,000
Pfizer | Transition Services Agreement | Research and development
Related Party Transaction [Line Items]
Related party transaction, expenses from transactions with related party					0	400,000	0	1,000,000
Bellco | Sublease Agreement
Related Party Transaction [Line Items]
Area of office space (in square feet) | ft²			1,293
Sublease, term of contract (in years)			3 years
Operating lease right-of-use asset					100,000		100,000		100,000
Operating lease liability					100,000		100,000		$ 200,000
Bellco | Consulting Agreements
Related Party Transaction [Line Items]
Related party costs					$ 200,000	100,000	$ 400,000	300,000
Bellco | Consulting Agreements | Payments Commencing January 2019
Related Party Transaction [Line Items]
Related party transaction monthly payment in arrears				$ 33,333
Bellco | Consulting Agreements | Payments Commencing January 2020
Related Party Transaction [Line Items]
Related party transaction monthly payment in arrears				$ 37,500
Bellco | Consulting Agreements | Maximum
Related Party Transaction [Line Items]
Related party transaction compensation percentage				60.00%
ByHeart
Related Party Transaction [Line Items]
Number of members appointed to board of directors | board_member					2		2
ByHeart | Sublease Agreement
Related Party Transaction [Line Items]
Area of office space (in square feet) | ft²	2,907	2,180
Sublease income					$ 100,000	100,000	$ 200,000	100,000
Two River | Consulting Agreements
Related Party Transaction [Line Items]
Related party costs					$ 100,000	$ 100,000	$ 200,000	$ 300,000
[1]	The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	26,715,950	31,176,666
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	11,051,439	9,287,848
Restricted stock units subject to vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	2,491,709	1,433,582
Expected shares to be purchased under Employee Stock Purchase Plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	207,129	176,722
Founder's shares of common stock subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	10,600,961	16,658,645
Early exercised stock options subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	2,364,712	3,619,869

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event - Onyx	Jul. 31, 2020USD ($)
Subsequent Event [Line Items]
Term of contract	20 years
Potential payable related to termination of agreement	$ 4,300,000
Letter of Credit
Subsequent Event [Line Items]
Maximum borrowing capacity	4,300,000
Additional capacity to landlords	$ 900,000