Moderna (MRNA) 10-Q 30 Oct 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 20, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-38753
Entity Registrant Name	Moderna, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3467528
Entity Address, Address Line One	200 Technology Square
Entity Address, City or Town	Cambridge,
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	714-6500
Title of 12(b) Security	Common stock, par value $0.0001 per share
Trading Symbol	MRNA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		395,710,105
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001682852
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 1,505,581	$ 235,876
Investments	1,770,721	867,124
Accounts receivable	190,501	5,369
Prepaid expenses and other current assets	109,376	19,403
Restricted cash	1,032	1,032
Total current assets	3,577,211	1,128,804
Investments, non-current	691,969	159,987
Property and equipment, net	276,909	201,495
Right-of-use assets, operating leases	91,684	86,414
Restricted cash, non-current	11,053	10,791
Other non-current assets	2,047	1,931
Total assets	4,650,873	1,589,422
Current liabilities:
Accounts payable	20,521	7,090
Accrued liabilities	208,832	67,652
Deferred revenue	1,234,506	63,310
Other current liabilities	9,702	5,063
Total current liabilities	1,473,561	143,115
Deferred revenue, non-current	207,768	138,995
Operating lease liabilities, non-current	98,954	93,675
Financing lease liabilities, non-current	108,609	38,689
Other non-current liabilities	2,183	138
Total liabilities	1,891,075	414,612
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, par value $0.0001; 162,000,000 shares authorized as of September 30, 2020 and December 31, 2019; no shares issued or outstanding at September 30, 2020 and December 31, 2019	0	0
Common stock, par value $0.0001; 1,600,000,000 shares authorized as of September 30, 2020 and December 31, 2019; 395,390,672 and 336,536,985 shares issued and outstanding as of September 30, 2020 and December 31, 2019, respectively	40	34
Additional paid-in capital	4,726,007	2,669,426
Accumulated other comprehensive income	4,784	1,804
Accumulated deficit	(1,971,033)	(1,496,454)
Total stockholders’ equity	2,759,798	1,174,810
Total liabilities and stockholders’ equity	$ 4,650,873	$ 1,589,422

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	162,000,000	162,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	1,600,000,000	1,600,000,000
Common stock, shares, issued (in shares)	395,390,672	336,536,985
Common stock, shares, outstanding (in shares)	395,390,672	336,536,985

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Revenue:
Total revenue	$ 157,910	$ 17,046	[1]	$ 232,650	$ 46,154	[1]
Operating expenses:
Research and development	344,486	119,637	[1]	611,479	378,355	[1]
General and administrative	48,541	28,173	[1]	109,277	83,913	[1]
Total operating expenses	393,027	147,810	[1]	720,756	462,268	[1]
Loss from operations	(235,117)	(130,764)	[1]	(488,106)	(416,114)	[1]
Interest income	5,571	9,252	[1]	20,515	30,546	[1]
Other expense, net	(3,226)	(1,881)	[1]	(5,910)	(5,689)	[1]
Loss before income taxes	(232,772)	(123,393)	[1]	(473,501)	(391,257)	[1]
Provision for (benefit from) income taxes	864	(178)	[1]	1,078	(526)	[1]
Net loss	$ (233,636)	$ (123,215)	[2]	$ (474,579)	$ (390,731)	[2]
Net loss per share, basic and diluted (usd per share)	$ (0.59)	$ (0.37)	[1]	$ (1.26)	$ (1.19)	[1]
Weighted average common shares used in net loss per share, basic and diluted (in shares)	394,682,744	330,769,341	[1]	376,174,283	329,592,322	[1]
Grant revenue
Revenue:
Total revenue	$ 145,694	$ 3,708	[1]	$ 187,535	$ 8,671	[1]
Collaboration revenue
Revenue:
Total revenue	$ 12,216	$ 13,338	[1]	$ 45,115	$ 37,483	[1]
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	[1]	Sep. 30, 2020	Sep. 30, 2019	[1]
Statement of Comprehensive Income [Abstract]
Net loss	$ (233,636)	$ (123,215)		$ (474,579)	$ (390,731)
Other comprehensive income:
Unrealized (loss) gain on available-for-sale debt securities, net of tax of $0 and $25, for the three months ended September 30, 2020 and 2019, respectively, and net of tax of $0 and $1,173 for the nine months ended September 30, 2020 and 2019, respectively	(3,683)	168		1,878	4,243
Less: amounts recognized for net realized loss (gain) included in net loss	211	(79)		1,102	(93)
Total other comprehensive (loss) income	(3,472)	89		2,980	4,150
Comprehensive loss	$ (237,108)	$ (123,126)		$ (471,599)	$ (386,581)
[1]	Restated to conform to ASC 842. See accompanying Note 2.

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Unrealized gain (loss) on available-for-sale debt securities, tax	$ 0	$ 25	$ 0	$ 1,173

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total		Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit		ASU adjustment	ASU adjustmentAccumulated Deficit
Balance at beginning of period (in shares) at Dec. 31, 2018				328,798,904
Balance at beginning of period at Dec. 31, 2018		$ 1,530,241	[1]	$ 33	$ 2,538,155	$ (1,320)	$ (1,006,627)	[1]
Balance at beginning of period (Accounting standards update 2014-09) at Dec. 31, 2018	[1]								$ 27,984	$ 27,984
Balance at beginning of period (Accounting standards update 2016-02) at Dec. 31, 2018	[1]								$ (3,789)	$ (3,789)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)				141,153
Vesting of restricted common stock units	[1]	0
Exercise of options to purchase common stock, net (in shares)				3,554,720
Exercise of options to purchase common stock, net		19,541	[1]		19,541
Stock-based compensation		60,796	[1]		60,796
Unrealized gain (loss) on marketable securities		4,150	[2]			4,150
Net loss		(390,731)	[2]				(390,731)	[1]
Balance at end of period (in shares) at Sep. 30, 2019				332,494,777
Balance at end of period at Sep. 30, 2019		1,248,192	[1]	$ 33	2,618,492	2,830	(1,373,163)	[3]
Balance at beginning of period (in shares) at Jun. 30, 2019				329,958,172
Balance at beginning of period at Jun. 30, 2019		1,334,960	[3]	$ 33	2,582,134	2,741	(1,249,948)	[3]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)				33,678
Vesting of restricted common stock units		0
Exercise of options to purchase common stock, net (in shares)				2,502,927
Exercise of options to purchase common stock, net		15,554	[3]		15,554
Stock-based compensation		20,804	[3]		20,804
Unrealized gain (loss) on marketable securities		89	[2]			89
Net loss		(123,215)	[2]				(123,215)
Balance at end of period (in shares) at Sep. 30, 2019				332,494,777
Balance at end of period at Sep. 30, 2019		1,248,192	[1]	$ 33	2,618,492	2,830	(1,373,163)	[3]
Balance at beginning of period (in shares) at Dec. 31, 2019				336,536,985
Balance at beginning of period at Dec. 31, 2019		1,174,810		$ 34	2,669,426	1,804	(1,496,454)
Balance at end of period at Mar. 31, 2020						(6,127)
Balance at beginning of period (in shares) at Dec. 31, 2019				336,536,985
Balance at beginning of period at Dec. 31, 2019		1,174,810		$ 34	2,669,426	1,804	(1,496,454)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from public offering of common stock, net of issuance costs (in shares)				47,863,158
Proceeds from public offering of common stock, net of issuance costs		1,852,759		$ 4	1,852,755
Vesting of restricted common stock (in shares)				203,488
Vesting of restricted common stock units		$ 0
Exercise of options to purchase common stock, net (in shares)		10,613,303		10,613,303
Exercise of options to purchase common stock, net		$ 133,369		$ 2	133,367
Purchase of common stock under employee stock purchase plan (in shares)				173,738
Purchase of common stock under employee stock purchase plan		2,917			2,917
Stock-based compensation		67,542			67,542
Unrealized gain (loss) on marketable securities		2,980				2,980
Net loss		(474,579)					(474,579)
Balance at end of period (in shares) at Sep. 30, 2020				395,390,672
Balance at end of period at Sep. 30, 2020		2,759,798		$ 40	4,726,007	4,784	(1,971,033)
Balance at beginning of period at Mar. 31, 2020						(6,127)
Balance at end of period (in shares) at Jun. 30, 2020				393,277,267
Balance at end of period at Jun. 30, 2020		2,946,885		$ 39	4,675,987	8,256	(1,737,397)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (in shares)				43,374
Vesting of restricted common stock units		0
Exercise of options to purchase common stock, net (in shares)				2,070,031
Exercise of options to purchase common stock, net		26,815		$ 1	26,814
Stock-based compensation		23,206			23,206
Unrealized gain (loss) on marketable securities		(3,472)				(3,472)
Net loss		(233,636)					(233,636)
Balance at end of period (in shares) at Sep. 30, 2020				395,390,672
Balance at end of period at Sep. 30, 2020		$ 2,759,798		$ 40	$ 4,726,007	$ 4,784	$ (1,971,033)
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.
[3]	Restated to conform to ASC 842. See accompanying Note 2.

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Statement of Stockholders' Equity [Abstract]
Offering expenses	$ 2,086

CONDENSED CONSOLIDATED STATEM_6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (474,579)	$ (390,731)	[1]
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	67,542	60,796	[2]
Depreciation and amortization	23,545	22,046	[2]
Amortization/accretion of investments	5,053	(3,428)	[2]
Loss on disposal of property and equipment	287	70	[2]
Changes in assets and liabilities:
Accounts receivable	(185,132)	4,369	[2]
Prepaid expenses and other assets	(67,994)	1,813	[2]
Right-of-use assets, operating leases	(13,117)	(7,970)	[2]
Accounts payable	13,633	(19,185)	[2]
Accrued liabilities	132,374	(8,253)	[2]
Deferred revenue	1,239,969	(32,795)	[2]
Operating lease liabilities	14,417	13,475	[2]
Other liabilities	6,684	(153)	[2]
Net cash provided by (used in) operating activities	762,682	(359,946)	[2]
Investing activities
Purchases of marketable securities	(2,326,141)	(949,277)	[2]
Proceeds from maturities of marketable securities	748,152	747,846	[2]
Proceeds from sales of marketable securities	140,337	81,030	[2]
Purchases of property and equipment	(44,147)	(24,892)	[2]
Net cash used in investing activities	(1,481,799)	(145,293)	[2]
Financing activities
Proceeds from public offerings of common stock, net of issuance costs	1,852,759	0	[2]
Proceeds from issuance of common stock through equity plans, net	133,369	19,541	[2]
Proceeds from purchase of common stock under employee stock purchase plan	2,917	0
Charges to financing lease liabilities	39	741	[2]
Net cash provided by financing activities	1,989,084	20,282	[2]
Net increase (decrease) in cash, cash equivalents and restricted cash	1,269,967	(484,957)	[2]
Cash, cash equivalents and restricted cash, beginning of year	247,699	670,491	[2]
Cash, cash equivalents and restricted cash, end of period	1,517,666	185,534	[2]
Non-cash investing and financing activities
Purchases of property and equipment included in accounts payable and accrued liabilities	13,280	1,863	[2]
Leasehold improvements included in prepaid and other current assets	$ 0	$ 6,310
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.

Description of the Business

Description of the Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of the Business	Description of the Business Moderna, Inc. (collectively, with its consolidated subsidiaries, any of Moderna, we, us, or the Company) was incorporated in Delaware on July 22, 2016. We are the successor in interest to Moderna LLC, a limited liability company formed under the laws of the State of Delaware in 2013. Our principal executive office is located at 200 Technology Square, Cambridge, MA. We are a biotechnology company creating a new generation of transformative medicines based on messenger RNA (mRNA), to improve the lives of patients. mRNA medicines are designed to direct the body’s cells to produce intracellular, membrane, or secreted proteins that have a therapeutic or preventive benefit with the potential to address a broad spectrum of diseases. Our platform builds on continuous advances in basic and applied mRNA science, delivery technology, and manufacturing, providing us the capability to pursue in parallel a robust pipeline of new development candidates. We are developing therapeutics and vaccines for infectious diseases, immuno-oncology, rare diseases, autoimmune and cardiovascular diseases, independently and with our strategic collaborators. Since inception, we have incurred significant net losses. As of September 30, 2020, we had an accumulated deficit of $1.97 billion. We may continue to incur significant expenses and operating losses for the foreseeable future. In addition, we anticipate that our expenses will increase significantly in connection with our ongoing activities to support our platform research, drug discovery and clinical development, infrastructure and Research Engine and Early Development Engine, digital infrastructure, creation of a portfolio of intellectual property, pre-launch inventory buildup, expansion into global markets, and administrative support. We do not expect to recognize significant revenue from sales of potential mRNA medicines unless and until we successfully complete clinical development and obtain regulatory approval for one or more of our investigational medicines. If we seek to obtain regulatory approval for any of our investigational medicines, we expect to incur significant commercialization expenses. Our investigational vaccine against the novel coronavirus (mRNA-1273), which is currently in clinical trials, has been developed rapidly to respond to the global COVID-19 pandemic. We are expending significant efforts to further the rapid development of this potential vaccine and expect to continue to do so over the next 12 months. These efforts have required and will continue to require the expenditure of significant funds and the establishment of significant worldwide infrastructure and partnerships. As a result, we expect we will need substantial additional funding to support our continued operations and pursue our growth strategy. Until we can generate significant revenue from potential mRNA medicines, if ever, we expect to finance our operations through a combination of public or private equity offerings, structured financings and debt financings, government funding arrangements, strategic alliances and marketing, manufacturing, distribution and licensing arrangements. We may be unable to raise additional funds or enter into such other agreements on favorable terms, or at all. If we fail to raise capital or enter into such agreements as, and when, needed, we may have to significantly delay, scale back or discontinue the development and commercialization of one or more of our programs. We believe that our cash, cash equivalents, and investments as of September 30, 2020 will be sufficient to enable us to fund our projected operations through at least the next 12 months from the issuance of our financial statements. Because of the numerous risks and uncertainties associated with pharmaceutical development, we are unable to predict the timing or amount of increased expenses or when or if we will be able to achieve or maintain profitability. Even if we are able to generate revenues from the sale of our investigational medicines, including mRNA-1273, if approved, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to continue our operations at planned levels and be forced to reduce our operations.

Summary of Basis of Presentatio

Summary of Basis of Presentation and Recent Accounting Standards	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Basis of Presentation and Recent Accounting Standards	Summary of Basis of Presentation and Recent Accounting Standards Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements that accompany these notes have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial reporting, consistent in all material respects with those applied in our Annual Report on Form 10-K for the year ended December 31, 2019 (2019 Form 10-K). Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). This report should be read in conjunction with the consolidated financial statements in our 2019 Form 10-K. The consolidated financial statements include the Company and its subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Use of Estimates We have made estimates and judgments affecting the amounts reported in our condensed consolidated financial statements and the accompanying notes. On an ongoing basis, we evaluate our estimates, including critical accounting policies or estimates related to revenue recognition, research and development expenses, income tax provisions, stock-based compensation, leases, and useful lives of long-lived assets. We base our estimates on historical experience and on various relevant assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. The actual results that we experience may differ materially from our estimates. Significant estimates relied upon in preparing these financial statements include, among others, those related to fair value of equity awards, revenue recognition, research and development expenses, leases, fair value instruments, useful lives of property and equipment, income taxes, and our valuation allowance on our deferred tax assets. Significant Accounting Policies The significant accounting policies used in preparation of these condensed consolidated financial statements for the three and nine months ended September 30, 2020 are consistent with those described in our 2019 Form 10-K, except for “ Pre-Launch Inventory ” and as noted within the “ Recently Adopted Accounting Standards ” section below. Effective on December 31, 2019, we lost our emerging growth company (EGC) status which accelerated the requirement of ASC 842 (Lease Accounting) adoption. As a result, we adjusted our previously reported consolidated financial statements effective January 1, 2019 in our 2019 Form 10-K, and amendments to previously filed Forms 10-Q were not required. Accordingly, our prior period condensed consolidated financial statements and information, as presented herein, have been restated to conform to the new standard. The following tables summarize the effects of adopting ASC 842 on our condensed consolidated financial statements for the three and nine months ended September 30, 2019 (in thousands, except per share data): Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ASC 842 ASC 842 Previously reported Adjustments As adjusted Previously reported Adjustments As adjusted Operating expenses: Research and development $ 119,715 $ (78) $ 119,637 $ 378,786 $ (431) $ 378,355 General and administrative 28,188 (15) 28,173 83,994 (81) 83,913 Total operating expenses 147,903 (93) 147,810 462,780 (512) 462,268 Loss from operations (130,857) 93 (130,764) (416,626) 512 (416,114) Other expense, net (1,767) (114) (1,881) (5,351) (338) (5,689) Loss before benefit from income taxes (123,372) (21) (123,393) (391,431) 174 (391,257) Net loss (123,194) (21) (123,215) (390,905) 174 (390,731) Net loss per share attributable to common stockholders, basic and diluted (0.37) — (0.37) (1.19) — (1.19) Nine Months Ended September 30, 2019 Previously reported ASC 842 Adjustment during the period As adjusted Operating activities Net loss $ (390,905) $ 174 $ (390,731) Depreciation and amortization 22,082 (36) 22,046 Prepaid expenses and other assets (1,407) 3,220 1,813 Right-of-use assets, operating leases — (7,970) (7,970) Deferred lease obligation 3,844 (3,844) — Operating lease liabilities — 13,475 13,475 Other liabilities 1,617 (1,770) (153) Net cash used in operating activities (363,195) 3,249 (359,946) Financing activities Reimbursement of assets under lease financing obligation 3,678 (3,678) — Charges to financing lease obligation — 741 741 Payments on financing lease obligation 312 (312) — Net cash provided by financing activities 23,531 (3,249) 20,282 Comprehensive Loss Comprehensive loss includes net loss and other comprehensive (loss) income for the period. Other comprehensive (loss) income consists of unrealized gains and losses on our investments. Total comprehensive loss for all periods presented has been disclosed in the condensed consolidated statements of comprehensive loss. The components of accumulated other comprehensive (loss) income for the three and nine months ended September 30, 2020 are as follows (in thousands): Unrealized (Loss) Gain on Available-for-Sale Debt Securities Accumulated other comprehensive income, balance at December 31, 2019 $ 1,804 Other comprehensive loss (7,931) Accumulated other comprehensive loss, balance at March 31, 2020 (6,127) Other comprehensive income 14,383 Accumulated other comprehensive income, balance at June 30, 2020 8,256 Other comprehensive loss (3,472) Accumulated other comprehensive income, balance at September 30, 2020 $ 4,784 Restricted Cash We include our restricted cash balance in the cash, cash equivalents and restricted cash reconciliation of operating, investing and financing activities in the condensed consolidated statements of cash flows. The following table provides a reconciliation of cash, cash equivalents and restricted cash in the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 1,505,581 $ 173,711 Restricted cash 1,032 1,032 Restricted cash, non-current 11,053 10,791 Total cash, cash equivalents and restricted cash shown in the condensed consolidated $ 1,517,666 $ 185,534 Pre-Launch Inventory Prior to an initial regulatory approval for our investigational medicines, we expense costs relating to production of inventory as research and development expense in our condensed consolidated statements of operations, in the period incurred. When we believe regulatory approval and subsequent commercialization of our investigational medicines is probable, and we also expect future economic benefit from the sales of the investigational medicines to be realized, we will then capitalize the costs of production as inventory. Recently Adopted Accounting Standards In June 2016, the FASB issued ASU No. 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard changes how companies account for credit losses for most financial assets and certain other instruments. For trade receivables, loans and held-to-maturity debt securities, companies will be required to recognize an allowance for credit losses rather than reducing the carrying value of the asset. The amendments in this standard should be applied on a modified retrospective basis to all periods presented. We adopted this standard in the first quarter of 2020. Based on the composition of our investment portfolio and investment policy, the adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This standard requires capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). We adopted this standard in the first quarter of 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard removes certain exceptions for investments, intra-period allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. We early adopted this standard in the second quarter of 2020. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. Recently Issued Accounting Standards From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements and disclosures.

Grant Revenue

Grant Revenue	9 Months Ended
	Sep. 30, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Grant Revenue	Grant RevenueIn September 2020, we entered into an agreement with the Defense Advanced Research Projects Agency (DARPA) for an award of up to $56.4 million to fund development of a mobile manufacturing prototype leveraging our existing manufacturing technology that is capable of rapidly producing vaccines and therapeutics. As of September 30, 2020, the committed funding was $5.0 million, with an additional $51.4 million available if DARPA exercises additional contract options. In April 2020, we entered into an agreement with the Biomedical Advanced Research and Development Authority (BARDA), a division of the Office of the Assistant Secretary for Preparedness and Response (ASPR) within the U.S. Department of Health and Human Services (HHS), for an award of up to $483.3 million to accelerate development of mRNA-1273, our vaccine candidate against the novel coronavirus. In July 2020, we amended our agreement with BARDA to provide for an additional commitment of up to $471.6 million to support late-stage clinical development of mRNA-1273, including the execution of a 30,000 participant Phase 3 study in the U.S. The amendment increased the maximum award from BARDA from $483.3 million to $954.9 million. Under the terms of the agreement, BARDA will fund the advancement of mRNA-1273 to FDA licensure. All contract options have been exercised. As of September 30, 2020, the remaining available funding net of revenue earned was $781.7 million. In September 2016, we received an award of up to $125.8 million from BARDA, to help fund our Zika vaccine program. Three of the four contract options have been exercised. As of September 30, 2020, the remaining available funding net of revenue earned was $71.9 million, with an additional $8.4 million available if the final contract option is exercised. In January 2016, we entered a global health project framework agreement with the Gates Foundation to advance mRNA-based development projects for various infectious diseases, including human immunodeficiency virus (HIV). As of September 30, 2020, the available funding net of revenue earned was $12.6 million, with up to an additional $80.0 million available if additional follow-on projects are approved. The following tables summarize grant revenue and deferred grant revenue as of and for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 BARDA $ 143,318 $ 1,135 $ 183,134 $ 4,500 Other grant revenue 2,376 2,573 4,401 4,171 Total grant revenue $ 145,694 $ 3,708 $ 187,535 $ 8,671 September 30, December 31, 2020 2019 Deferred grant revenue $ 5,670 $ 1,496 U.S. Supply Agreement In August 2020, we entered into a supply agreement with the U.S. Government, which we refer to as the U.S. Supply Agreement, for 100 million doses of our vaccine candidate against COVID-19, mRNA-1273, for a total award of up to $1.525 billion. The total award amount includes approximately $300.0 million of incentive payments which we will earn if an Emergency Use Authorization or a Biologics License Application, which we refer to as an EUA or a BLA, respectively, is received on or before January 31, 2021. We will receive such incentive payments as product is delivered to and accepted by the U.S. Government. Pursuant to the U.S. Supply Agreement, the U.S. Government made a $601.4 million upfront payment to us which represents approximately 50% of the fixed price per dose that we are entitled to receive for the committed 100 million doses. We will receive the remaining 50% of the fixed price per dose upon delivery and acceptance of the 100 million doses to the U.S. Government. We will secure, manage and maintain storage for up to 100 million doses of mRNA-1273 based on the specific requirements of the contract and deliver the product to the designated government facility in accordance with the U.S. Supply Agreement. We will be reimbursed for such services at a negotiated price prior to the first product delivery. The U.S. Government has the option to purchase up to an additional 400 million doses at a fixed price of $1.65 billion per 100 million doses by specified dates in the agreement. The U.S. Supply Agreement contains terms and conditions that are customary for U.S. Government agreements of this nature, including provisions giving the U.S. Government the right to terminate the agreement if the applicable Contracting Officer determines that a termination is in the U.S. Government’s interest. Following any such termination, we and the U.S. Government may agree upon the amount to be paid or remaining to be paid to us because of the termination. Accounting Treatment We determined that the U.S. Supply Agreement represents a transaction with a customer and therefore should be accounted for in accordance with ASC 606. We concluded that the delivery of each dose pursuant to the U.S. Supply Agreement represents a separate performance obligation and therefore we have multiple performance obligations under the contract. The U.S. Government options to purchase additional doses are considered marketing offers and will be accounted for as a separate contract upon the customer’s election. The total transaction price for the U.S. Supply Agreement is $1.225 billion, which represents the fixed price for the 100 million doses ordered. We have fully constrained the $300.0 million incentive payments as such amounts are subject to our receipt of regulatory approval (an EUA or BLA). We have determined the upfront payment of $601.4 million received from the U.S. Government is non-refundable as we have incurred costs to date related to the U.S. Supply Agreement that exceed such amount. We will recognize revenue based on the fixed price per dose when control of the product has transferred and customer acceptance has occurred, unless such acceptance provisions are deemed perfunctory. For the three and nine months ended September 30, 2020, we did not recognize any revenue associated with the U.S. Supply Agreement. As of September 30, 2020, the aggregate amount of the transaction price allocated to the remaining performance obligations is expected to be recognized as revenue within a year. As of September 30, 2020, we had deferred revenue of $601.4 million, classified as current deferred revenue in our condensed consolidated balance sheet. Timing of product manufacturing, delivery and receipt of marketing approval will determine the period in which revenue is recognized. International Supply Agreements In the third quarter of 2020, we entered into several supply agreements with international government agencies, including agencies from which we had previously received deposits in the second quarter of 2020, to supply such agencies with mRNA-1273, our vaccine candidate against COVID-19. Pursuant to the supply agreements, we have promised to provide a certain quantity of doses, which we refer to as the Ordered Amount, based on anticipated delivery schedules. Certain agreements provide the ability to increase an agency’s Ordered Amount during specific periods of time. Each agency may have to pay an upfront for its Ordered Amount, and can receive a partial refund based on contractual provisions in such supply agreement that generally involve delivery delays, certain failures (delivery failures, clinical failures or failure to obtain market approvals) or the discontinuation of our worldwide clinical development of mRNA-1273. As of September 30, 2020, we had received cash of $569.0 million associated with such international supply agreements. Each supply agreement contains delivery and acceptance instructions. We continue to work with each applicable agency to confirm our distribution channel to each territory covered by such agreement. Accounting Treatment We determined that each supply agreement represents a transaction with a customer and therefore should be accounted for in accordance with ASC 606. We concluded that the delivery of each dose pursuant to a supply agreement represents a separate performance obligation and therefore we have multiple performance obligations under each contract. Options to increase the Ordered Amount are considered marketing offers and each will be accounted for as a separate contract upon the customer’s election. The total transaction price for each supply agreement equals the Ordered Amount multiplied by the fixed price per dose charged to the customer. Because the customer can reduce the Ordered Amount in certain circumstances based on the terms of the applicable supply agreement, we have concluded that the transaction price represents variable consideration. We have elected to not include sales and excise tax in the transaction price as an accounting election and any ancillary costs, to the extent billable to the customer, will be recorded as an offset to our related costs as such costs will be invoiced at cost. We will recognize revenue based on the fixed price per dose when control of the product has transferred to the customer and customer acceptance has occurred, unless such acceptance provisions are deemed perfunctory.

Collaboration Revenue

Collaboration Revenue	9 Months Ended
	Sep. 30, 2020
Research and Development [Abstract]
Collaboration Revenue	Collaboration Revenue The following table summarizes our total consolidated net revenue from our strategic collaborators for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Collaboration Revenue by Strategic Collaborator: 2020 2019 2020 2019 AstraZeneca $ 48 $ 3,724 $ 17,202 $ 4,726 Merck 6,718 9,110 18,060 28,456 Vertex 5,450 504 9,698 4,301 Other — — 155 — Total collaboration revenue $ 12,216 $ 13,338 $ 45,115 $ 37,483 The following table presents changes in the balances of our receivables and contract liabilities related to our strategic collaboration agreements during the nine months ended September 30, 2020 (in thousands): December 31, 2019 Additions Deductions September 30, 2020 Contract Assets: Accounts receivable $ 1,972 $ 115,037 $ (85,354) $ 31,655 Contract Liabilities: Deferred revenue $ 199,528 $ 117,002 $ (50,320) $ 266,210 During the three and nine months ended September 30, 2020, we recognized the following revenue as a result of the change in the contract liability balances related to our collaboration agreements (in thousands): Revenue recognized in the period from: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Amounts included in contract liabilities at the beginning of the period (1) $ 13,263 $ 50,320 Performance obligations satisfied (or partially satisfied) in previous reporting periods (2) — 1,262 ______ (1) We first allocate revenue to the individual contract liability balance outstanding at the beginning of the period until the revenue exceeds that balance. If additional consideration is received on those contracts in subsequent periods, we assume all revenue recognized in the reporting period is first applied to the beginning contract liability. (2) Related to changes in estimated costs for our future performance obligations and estimated variable considerations. As of September 30, 2020, the aggregated amount of the transaction price allocated to performance obligations under our collaboration agreements that are unsatisfied or partially unsatisfied was $366.7 million. AstraZeneca – Strategic Alliances in Cardiovascular and Oncology 2013 Option Agreement and Services and Collaboration Agreement In March 2013, we entered into an Option Agreement, the AZ Option Agreement, and a related Services and Collaboration Agreement, the AZ Services Agreement, with AstraZeneca plc (AstraZeneca) to develop and commercialize potential therapeutic mRNA medicines directed at certain targets for the treatment of cardiovascular and cardiometabolic diseases and cancer, which were amended and restated in June 2018. We refer to these agreements in the forms that existed prior to the 2018 amendment and restatement as the 2013 AZ Agreements. 2016 Strategic Alliance with AstraZeneca – IL-12 In January 2016, we entered into a new Strategic Drug Development Collaboration and License Agreement, which we refer to as the 2016 AZ Agreement, with AstraZeneca to discover, develop and commercialize potential mRNA medicines for the treatment of a range of cancers. 2017 Strategic Alliance with AstraZeneca – Relaxin In October 2017, we entered a new Collaboration and License Agreement, which we refer to as the 2017 AZ Agreement, under which AstraZeneca may clinically develop and commercialize a development candidate, now known as AZD7970, which is comprised of an mRNA construct for the relaxin protein designed by us and encapsulated in one of our proprietary lipid nanoparticles (LNP). We discovered and performed preclinical development activities for AZD7970 prior to the initiation of the strategic alliance with AstraZeneca under the 2017 AZ Agreement. 2013 Agreements with AstraZeneca, amended and restated in 2018 In June 2018, we entered into an Amended and Restated Option Agreement and a related Amended and Restated Services and Collaboration Agreement with AstraZeneca (2018 A&R Agreements), which amended and restated the 2013 AZ Agreements. Under the 2018 A&R Agreements, we granted AstraZeneca certain exclusive rights and licenses to research, develop and commercialize potential therapeutic mRNA medicines directed at certain targets for the treatment of cardiovascular and cardiometabolic diseases and cancer, and agreed to provide related services to AstraZeneca. The activities to be performed by the parties under the 2018 A&R Agreements are limited to defined biological targets in the cardiovascular and cardiometabolic fields and one defined target in the cancer field. Please refer to our 2019 Form 10-K under the heading “Third-Party Strategic Alliances” for further description of each of the AstraZeneca collaboration agreements. Accounting Treatment We applied the provisions of ASC 606 (Revenue from Contracts with Customers) in accounting for these arrangements, except for the 2017 AZ Agreement which was accounted for under ASC 808 (Collaborative Arrangements). In August 2016, AstraZeneca exercised a product option available pursuant to the 2013 AZ Agreements to obtain exclusive rights to clinically develop and commercialize the VEGF-A product (AZD8601). This option exercise is referred to as the 2016 VEGF Exercise. Pursuant to ASC 606, we determined that the 2016 VEGF Exercise and the 2017 AZ Agreement should be accounted for as separate transactions as the agreements are not interrelated or interdependent. Conversely, the 2013 Agreements, as amended by the 2018 A&R Agreements, and the 2016 AZ Agreement, were combined for accounting purposes and treated as a single agreement, as these agreements were negotiated in contemplation of each other. We refer to this combined transaction as the Combined 2018 AZ Agreements. We determined that all aspects of Combined 2018 AZ Agreements and the 2016 VEGF Exercise represent a transaction with a customer and therefore is accounted for in accordance with ASC 606. Combined 2018 AZ Agreements We identified the following performance obligations in the Combined 2018 AZ Agreements: (i) a combined performance obligation that includes a research license, research and development pool services, and manufacturing obligations related to the 2013 AZ Agreements, as amended by the 2018 A&R Agreements, collectively referred to as the Combined 2018 AZ Agreement Performance Obligation, (ii) preclinical development services for IL-12, (iii) preclinical development services for an oncology development target, (iv) a combined performance obligation for a development and commercialization license and manufacturing obligations for IL-12, and (v) a material right to receive development and commercialization rights and manufacturing services for an oncology development target. We concluded that the research license is not distinct from the research and development pool services or the manufacturing obligations related to the 2018 A&R Agreements, as AstraZeneca cannot fully exploit the value of the research license without receipt of such services and supply. Our services and supply involve specialized expertise, particularly as it relates to mRNA technology that is not available in the marketplace. Any supply requested by AstraZeneca in excess of the minimum quantities specified in the agreement are considered customer options and treated as separate contracts for accounting purposes. Further, we concluded that AstraZeneca cannot exploit the value of the development and commercialization license for IL-12 without receipt of supply as the development and commercialization license does not convey to AstraZeneca the right to manufacture and therefore combined the development and commercialization license and the manufacturing obligations for IL-12 into one performance obligation. The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, Combined 2018 AZ Agreements: 2020 2019 Upfront payments $ 240,000 $ 240,000 Sublicense reimbursement 1,000 1,000 Toxicity milestone payment 60,000 60,000 Competition milestone payment 60,000 60,000 Estimated reimbursement for IL-12 manufacturing obligations 38,089 40,782 Total $ 399,089 $ 401,782 We utilize the most likely amount method to determine the amount of reimbursement for IL-12 manufacturing obligations to be received. We determined that any sales-based royalties related to IL-12 will be recognized when the related sales occur as they were determined to relate predominately to the license granted and therefore have been excluded from the transaction price. In addition, we are eligible to receive future milestones and royalties on future commercial sales for optioned product candidates under the 2018 A&R Agreements and future royalties under the 2016 Agreement; however, these amounts are not considered variable consideration under the Combined 2018 Agreements as we are only eligible to receive such amounts if AstraZeneca exercises its options (including certain options that are deemed to be material rights). We have concluded that the exercise of an optioned product candidate represents a separate transaction under ASC 606. We re-evaluate the transaction price at the end of each reporting period. There was a $2.7 million decrease to the transaction price during the nine months ended September 30, 2020, resulting from a change in estimate of variable consideration. The transaction price was allocated to the performance obligations based on the relative estimated standalone selling prices of each performance obligation. We developed the estimated standalone selling price for the licenses included in the Combined 2018 AZ Agreement Performance Obligation and the combined performance obligation for a development and commercialization license and manufacturing obligations for IL-12 primarily based on the probability-weighted present value of expected future cash flows associated with each license related to each specific program. In developing such estimate, we also considered applicable market conditions and relevant entity-specific factors, including those factors contemplated in negotiating the agreement, probability of success and the time needed to commercialize a product candidate pursuant to the associated license. We developed the estimated standalone selling price for the services and/or manufacturing and supply included in each of the performance obligation, as applicable, primarily based on the nature of the services to be performed and/or goods to be manufactured and estimates of the associated costs, adjusted for a reasonable profit margin that would be expected to be realized under similar contracts. The estimated standalone selling price of the material right to receive development and commercialization rights and manufacturing services for an oncology development target was developed by estimating the amount of discount that AstraZeneca would receive when exercising the option and adjusting such amount by the likelihood that the option will be exercised. The following table summarizes the allocation of the total transaction price to the identified performance obligations under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price Combined 2018 AZ Agreements: September 30, 2020 Combined 2018 AZ Agreement performance obligation $ 293,223 Preclinical development service - IL-12 8,133 Preclinical development service - oncology development target 8,133 Development and commercialization license and manufacturing obligation 88,009 Material right to receive development and commercialization rights 1,591 Total $ 399,089 Remaining unsatisfied performance obligation $ 104,945 As of September 30, 2020, $95.2 million of the remaining performance obligations that are unsatisfied is expected to be recognized as revenue through December 31, 2029 and $9.7 million is expected to be recognized as revenue at the earlier of expiration or modification of the Combined 2018 AZ Agreement. We measure proportional performance over time using an input method based on cost incurred relative to the total estimated costs for the Combined 2018 AZ Agreement Performance Obligation and the preclinical development services for IL-12 and the other oncology target performance obligations. We recognize revenue related to the amounts allocated to the combined performance obligation for a development and commercialization license and manufacturing obligations for IL-12 based on the point in time upon which control of supply is transferred to AstraZeneca for each delivery of the associated supply. We recognize revenue for the Combined 2018 AZ Agreement Performance Obligation, on a quarterly basis, by determining the proportion of effort incurred as a percentage of total effort we expect to expend. This ratio is applied to the transaction price allocated to this combined performance obligation. We also estimate the development plan, including expected demand from AstraZeneca, and the associated costs for this combined performance obligation, as we will satisfy this combined performance obligation as the manufacturing services are performed. Management has applied significant judgment in the process of developing our budget estimates. Any changes to these estimates will be recognized in the period in which they change as a cumulative catch up. The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Combined AZ Agreements $ 49 $ 3,552 $ 2,950 $ 4,580 The revenue recognized for the three and nine months ended September 30, 2020 includes the amortization of deferred revenue due to the satisfaction of our performance obligation during the period, offset by a cumulative catch-up adjustment of $1.4 million in the first quarter due to changes in estimated costs for our future performance obligations. The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the services are expected to be performed or control of the supply is expected to be transferred (in thousands): September 30, 2020 December 31, 2019 Combined AZ Agreements $ 72,266 $ 73,669 2016 VEGF Exercise We concluded that the 2016 VEGF Exercise should be treated as a separate transaction for accounting purposes. We identified one performance obligation in this arrangement which is comprised of the exclusive license to develop and commercialize VEGF and the manufacturing of clinical supply. We concluded that the VEGF license is not distinct from the manufacturing obligations because AstraZeneca cannot fully exploit the value of the license without receipt of such supply. This is due to limitations inherent in the licenses conveyed wherein AstraZeneca does not have the contractual right to manufacture during the term of the agreement. The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, 2016 VEGF Exercise: 2020 2019 Option exercise fee $ 10,000 $ 10,000 Milestone payment 30,000 30,000 Sublicense reimbursement 2,250 2,250 Estimated reimbursement for clinical supply 18,062 15,621 Total $ 60,312 $ 57,871 We are eligible to receive future milestones and royalties on future commercial sales under this arrangement. We utilize the most likely amount method to estimate any development and regulatory milestone payments to be received and the amount of estimated reimbursement for clinical supply. As of September 30, 2020, there were no milestones that had not been achieved included in the transaction price. We considered the stage of development and the risks associated with the remaining development required to achieve each milestone, as well as whether the achievement of the milestone is outside of our or AstraZeneca’s control. The outstanding milestone payments were fully constrained, as a result of the uncertainty whether any of the milestones would be achieved. We determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur as they were determined to relate predominantly to the license granted and therefore have also been excluded from the transaction price. We re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. When a milestone payment is included in the transaction price in the future, it is recognized as revenue based on the relative completion of the underlying performance obligation. There was a $2.4 million increase to the transaction price during the nine months ended September 30, 2020, resulting from a change in estimate of variable consideration. The following table summarizes the total transaction price allocated to the single identified performance obligation under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price September 30, 2020 2016 VEGF Exercise combined performance obligation $ 60,312 Remaining unsatisfied performance obligation 41,877 As of September 30, 2020, the aggregate amount of the transaction price allocated to the remaining performance obligation that is unsatisfied is expected to be recognized as revenue through December 31, 2025. We recognize revenue related to the amount of the transaction price allocated to the VEGF Exercise performance obligation based on the point in time upon which control of supply is transferred to AstraZeneca for each delivery of the associated supply. The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 2016 VEGF Exercise $ — $ 172 $ 14,253 $ 146 The revenue recognized for the three and nine months ended September 30, 2020 includes the amortization of deferred revenue due to the satisfaction of our performance obligation during the period, offset by a cumulative catch-up adjustment in the first quarter of $0.4 million as a reduction of revenue due to changes in estimated costs for our future performance obligation associated with the 2016 VEGF Exercise. The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the control of the supply is expected to be transferred for the periods presented (in thousands): September 30, 2020 December 31, 2019 2016 VEGF Exercise $ 29,335 $ 41,266 2017 AZ Agreement We concluded the 2017 AZ Agreement is under the scope of ASC 808 as we and AstraZeneca are both active participants in the development, manufacturing and commercialization activities and are exposed to significant risks and rewards that are dependent on commercial success of the activities of the arrangement. Additionally, we determined the development, manufacturing and commercialization activities are not deliverables under ASC 606. As a result, the activities conducted pursuant to the development, manufacturing and commercialization activities are accounted for as a component of the related expense in the period incurred. We considered the guidance in ASC 606 by analogy in determining the appropriate treatment for the transactions between us and AstraZeneca and concluded that reimbursement for transactions in which we are considered to be principal because we control a promised good or service before transferring that good or service to the customer, are accounted for as gross revenue. We did not recognize any revenue from the 2017 AZ Agreement for either of the three or nine month periods ended September 30, 2020 and 2019. Merck – Strategic Alliances in Infectious Diseases and Cancer Vaccines 2015 Strategic Alliance with Merck – Infectious Disease In January 2015, we entered into a Master Collaboration and License Agreement with Merck & Co., Inc (Merck), which was amended in each of January 2016, June 2016, and May 2019, and which we refer to, as amended, as the 2015 Merck Agreement. Pursuant to the 2015 Merck Agreement, we and Merck have agreed to research, develop, and commercialize potential mRNA medicines for the prevention of infections by RSV. Subsequent to the end of the third quarter of 2020, the Master Collaboration and License Agreement between us and Merck related to our collaboration on RSV was terminated by mutual agreement on October 7, 2020. Please refer to our 2019 Form 10-K under the heading “Third-Party Strategic Alliances” for further description of the 2015 Merck Agreement. Accounting Treatment We determined that all aspects of amended 2015 Merck Agreement represent a transaction with a customer and therefore the amended 2015 Merck Agreement is accounted for in accordance with ASC 606. The four-year research period was complete as of December 31, 2018 and we recognized the total transaction price of $65.0 million (the $60.0 million in aggregate upfront payments and a $5.0 million payment pertaining to achievement of a development milestone) in full as we concluded there were no unsatisfied performance obligations pertaining to the amended 2015 Merck Agreement. Additionally, we concluded the following customer options are marketing offers as such options did not provide any discounts or other rights that would be considered a material right in the arrangement: (i) research services during the three-year period following the initial four-year research period during which Merck may continue to preclinically and clinically develop product candidates and (ii) clinical mRNA supply for Phase 1 and Phase 2 and/or non-cGMP mRNA supply beyond the initial four-year research period. Therefore, such options would be accounted for as a separate contract if exercised by the customer. We utilize the most likely amount method to estimate any development and regulatory milestone payments to be received. As of September 30, 2020, there were no milestones that had not been achieved included in the transaction price. We considered the stage of development and the risks associated with the remaining development required to achieve each milestone, as well as whether the achievement of the milestone is outside of our or Merck’s control. The outstanding milestone payments were fully constrained, as a result of the uncertainty whether any of the milestones would be achieved. We determined that any commercial milestones and sales-based royalties would be recognized when the related sales were to occur as they were determined to relate predominantly to the license granted and therefore have also been excluded from the transaction price. If a milestone payment were to be included in the transaction price in the future, it would be recognized as revenue based on the relative completion of the underlying performance obligation. After completion of the initial four-year research period, and as part of the May 2019 amendment of the 2015 Merck Agreement, Merck elected to establish a new RSV vaccine product candidate and elected to conduct a Phase 1 clinical trial. We are responsible for certain costs associated with the conduct of the Phase 1 clinical trial. We determined that our obligation under the May 2019 amendment to reimburse Merck for certain costs associated with the RSV vaccine Phase 1 clinical trial represents consideration payable to a customer and is accounted for as a reduction of the transaction price. The consideration amount is determined based on the most likely method and recorded as contra-revenue as costs are incurred. The one-time payment upon election by Merck to continue developing RSV is fully constrained as it is contingent upon completion of the RSV Phase 1 clinical trial and upon decisions to be made by Merck to continue development thereafter. The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, 2015 Merck Agreement: 2020 2019 Upfront payments $ 60,000 $ 60,000 Development milestones 5,000 5,000 Reduction of reimbursements paid to Merck (10,778) (5,265) Total $ 54,222 $ 59,735 We re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. For the nine months ended September 30, 2020, there was a $5.5 million deduction to the transaction price related to reimbursements paid to Merck for RSV vaccine Phase I clinical trial costs. The following table summarizes the total transaction price allocated to the combined performance obligation under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price September 30, 2020 2015 Merck Agreement $ 54,222 Remaining unsatisfied performance obligation — We utilize the most likely amount method to estimate any development and regulatory milestone payments to be received. As of September 30, 2020, there were no milestones that had not been achieved included in the transaction price. We considered the stage of development and the risks associated with the remaining development required to achieve each milestone, as well as whether the achievement of the milestone is outside of our or Merck’s control. The outstanding milestone payments were fully constrained, as a result of the uncertainty whether any of the milestones would be achieved. We determined that any commercial milestones and sales-based royalties will be recognized when the related sales occur as they were determined to relate predominantly to the license granted and therefore have also been excluded from the transaction price. When a milestone payment is included in the transaction price in the future, it will be recognized as revenue based on the relative completion of the underlying performance obligation. The following table summarizes the revenue and contra-revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Contra-revenue under the May 2019 Amendment $ (1,074) $ (1,657) $ (5,513) $ (3,796) Collaboration revenue under the 2015 Merck Agreement — (188) 12 666 Total contra-revenue $ (1,074) $ (1,845) $ (5,501) $ (3,130) Contra-revenue recognized was related to consideration payable to Merck under the May 2019 Amendment. Collaboration revenue recognized was pursuant to separate agreements with Merck related to the exercise of customer options to purchase clinical mRNA supply to further develop a product candidate after the initial four-year research period. Clinical mRNA supply is recognized as collaboration revenue at a point in time upon which control of supply is transferred to Merck for each delivery of the associated supply. We had no deferred revenue as of September 30, 2020 or December 31, 2019 from the amended 2015 Merck Agreement as all performance obligations under the amended 2015 Merck Agreement were completed as of December 31, 2018. On October 7, 2020, the Master Collaboration and License Agreement between us and Merck related to our collaboration on RSV was terminated by mutual agreement. The termination did not have an impact to our condensed consolidated financial statements as of and for the three and nine months ended September 30, 2020. 2016 Cancer Vaccine Strategic Alliance—Personalized mRNA Cancer Vaccines In June 2016, we entered into a personalized mRNA cancer vaccines (PCV) Collaboration and License Agreement with Merck, which we refer to as the PCV Agreement, to develop and commercialize PCVs for individual patients using our mRNA vaccine and formulation technology. Under the strategic alliance, we identify genetic mutations present in a particular patient’s tumor cells, synthesize mRNA for these mutations, encapsulate the mRNA in one of our proprietary LNPs and administer to each patient a unique mRNA cancer vaccine designed to specifically activate the patient’s immune system against her or his own cancer cells. 2018 Expansion of the Cancer Vaccine Strategic Alliance—Shared Neoepitope Cancer Vaccines In April 2018, we and Merck agreed to expand our cancer vaccine strategic alliance to include the development and commercialization of our KRAS vaccine development candidate, mRNA-5671 or V941, and potentially other shared neoantigen mRNA cancer vaccines (SAVs). We preclinically developed mRNA-5671 prior to its inclusion in the cancer vaccine strategic alliance and it is comprised of a novel mRNA construct designed by us and encapsulated in one of our proprietary LNPs. The PCV Agreement was amended and restated to include the new SAV strategic alliance (PCV/SAV Agreement). Please refer to our 2019 Form 10-K under the heading “Third-Party Strategic Alliances” for further description of the Merck PCV/SAV Agreement. Accounting Treatment We determined that the PCV/SAV Agreement should be accounted for separately from the amended 2015 Merck Agreement, as the agreements were not negotiated in contemplation of one another and the elements within each of the agreements are not closely interrelated or interdependent on each other. We determined that all aspects of the PCV/SAV Agreement represent a transaction with a customer and therefore the PCV/SAV Agreement is accounted for in accordance with ASC 606. In addition, the equity investment in our Series H redeemable convertible preferred stock was considered together with the PCV/SAV Agreement as the transactions were executed contemporaneously in contemplation of one another. Further, the purchase price paid by Merck with respect to the investment in the Series H redeemable convertible preferred stock was not representative of fair value on the date of such purchase. As such, the incremental proceeds received in excess of the fair value of the underlying stock related to the equity investment were included in the transaction price related to the PCV/SAV Agreement and the shares of Series H redeemable convertible preferred stock purchased by Merck were recorded at their respective fair value on the date of issuance. We identified the following performance obligations in the PCV/SAV Agreement: (i) a research license and research and development services, including manufacturing and supply of PCVs, during the proof of concept (POC) term for the PCV program, referred to as the PCV Performance Obligation, and (ii) research license and manufacturing and supply of mRNA-5671 during the POC term for the KRAS program, referred to as the KRAS Performance Obligation. We concluded that the research license is not distinct from the research and development services, including manufacturing and supply of PCVs, during the POC term for the PCV program, as Merck cannot fully exploit the value of the license without receipt of such services and supply. Our services and supply involve specialized expertise, particularly as it relates to mRNA technology that is not available in the marketplace. Therefore, the research license has been combined with the research and development services, including manufacturing and supply of PCVs, during the POC term for the PCV program, into a single performance obligation. Similarly, we concluded that the research license is not distinct from the manufacturing and supply of mRNA-5671 during the POC term for the KRAS program, as Merck cannot fully exploit the value of the license without receipt of such supply which must be provided by us. This is due to limitations inherent in the licenses conveyed wherein Merck does not have the contractual right to manufacture during the POC term. Therefore, the research license has been combined with the manufacturing and supply of mRNA-5671, during the POC term for the KRAS program, into a single performance obligation. Conversely, we concluded that the PCV Performance Obligation and the KRAS Performance Obligation are distinct from each other because Merck can fully exploit the value of each program for its intended purpose without the promises associated with the other program. Additionally, we concluded the following customer options are marketing offers as such options did not provide any discounts or other rights that would be considered a material right in the arrangement: (i) Merck participation election license related to future joint development and commercialization on a program-by-program basis, (ii) manufacturing and supply in support of certain SAV programs and/or the PCV program upon Merck election to not participate in futur

Contracts With Customers

Contracts With Customers	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Contracts With Customers	Grant RevenueIn September 2020, we entered into an agreement with the Defense Advanced Research Projects Agency (DARPA) for an award of up to $56.4 million to fund development of a mobile manufacturing prototype leveraging our existing manufacturing technology that is capable of rapidly producing vaccines and therapeutics. As of September 30, 2020, the committed funding was $5.0 million, with an additional $51.4 million available if DARPA exercises additional contract options. In April 2020, we entered into an agreement with the Biomedical Advanced Research and Development Authority (BARDA), a division of the Office of the Assistant Secretary for Preparedness and Response (ASPR) within the U.S. Department of Health and Human Services (HHS), for an award of up to $483.3 million to accelerate development of mRNA-1273, our vaccine candidate against the novel coronavirus. In July 2020, we amended our agreement with BARDA to provide for an additional commitment of up to $471.6 million to support late-stage clinical development of mRNA-1273, including the execution of a 30,000 participant Phase 3 study in the U.S. The amendment increased the maximum award from BARDA from $483.3 million to $954.9 million. Under the terms of the agreement, BARDA will fund the advancement of mRNA-1273 to FDA licensure. All contract options have been exercised. As of September 30, 2020, the remaining available funding net of revenue earned was $781.7 million. In September 2016, we received an award of up to $125.8 million from BARDA, to help fund our Zika vaccine program. Three of the four contract options have been exercised. As of September 30, 2020, the remaining available funding net of revenue earned was $71.9 million, with an additional $8.4 million available if the final contract option is exercised. In January 2016, we entered a global health project framework agreement with the Gates Foundation to advance mRNA-based development projects for various infectious diseases, including human immunodeficiency virus (HIV). As of September 30, 2020, the available funding net of revenue earned was $12.6 million, with up to an additional $80.0 million available if additional follow-on projects are approved. The following tables summarize grant revenue and deferred grant revenue as of and for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 BARDA $ 143,318 $ 1,135 $ 183,134 $ 4,500 Other grant revenue 2,376 2,573 4,401 4,171 Total grant revenue $ 145,694 $ 3,708 $ 187,535 $ 8,671 September 30, December 31, 2020 2019 Deferred grant revenue $ 5,670 $ 1,496 U.S. Supply Agreement In August 2020, we entered into a supply agreement with the U.S. Government, which we refer to as the U.S. Supply Agreement, for 100 million doses of our vaccine candidate against COVID-19, mRNA-1273, for a total award of up to $1.525 billion. The total award amount includes approximately $300.0 million of incentive payments which we will earn if an Emergency Use Authorization or a Biologics License Application, which we refer to as an EUA or a BLA, respectively, is received on or before January 31, 2021. We will receive such incentive payments as product is delivered to and accepted by the U.S. Government. Pursuant to the U.S. Supply Agreement, the U.S. Government made a $601.4 million upfront payment to us which represents approximately 50% of the fixed price per dose that we are entitled to receive for the committed 100 million doses. We will receive the remaining 50% of the fixed price per dose upon delivery and acceptance of the 100 million doses to the U.S. Government. We will secure, manage and maintain storage for up to 100 million doses of mRNA-1273 based on the specific requirements of the contract and deliver the product to the designated government facility in accordance with the U.S. Supply Agreement. We will be reimbursed for such services at a negotiated price prior to the first product delivery. The U.S. Government has the option to purchase up to an additional 400 million doses at a fixed price of $1.65 billion per 100 million doses by specified dates in the agreement. The U.S. Supply Agreement contains terms and conditions that are customary for U.S. Government agreements of this nature, including provisions giving the U.S. Government the right to terminate the agreement if the applicable Contracting Officer determines that a termination is in the U.S. Government’s interest. Following any such termination, we and the U.S. Government may agree upon the amount to be paid or remaining to be paid to us because of the termination. Accounting Treatment We determined that the U.S. Supply Agreement represents a transaction with a customer and therefore should be accounted for in accordance with ASC 606. We concluded that the delivery of each dose pursuant to the U.S. Supply Agreement represents a separate performance obligation and therefore we have multiple performance obligations under the contract. The U.S. Government options to purchase additional doses are considered marketing offers and will be accounted for as a separate contract upon the customer’s election. The total transaction price for the U.S. Supply Agreement is $1.225 billion, which represents the fixed price for the 100 million doses ordered. We have fully constrained the $300.0 million incentive payments as such amounts are subject to our receipt of regulatory approval (an EUA or BLA). We have determined the upfront payment of $601.4 million received from the U.S. Government is non-refundable as we have incurred costs to date related to the U.S. Supply Agreement that exceed such amount. We will recognize revenue based on the fixed price per dose when control of the product has transferred and customer acceptance has occurred, unless such acceptance provisions are deemed perfunctory. For the three and nine months ended September 30, 2020, we did not recognize any revenue associated with the U.S. Supply Agreement. As of September 30, 2020, the aggregate amount of the transaction price allocated to the remaining performance obligations is expected to be recognized as revenue within a year. As of September 30, 2020, we had deferred revenue of $601.4 million, classified as current deferred revenue in our condensed consolidated balance sheet. Timing of product manufacturing, delivery and receipt of marketing approval will determine the period in which revenue is recognized. International Supply Agreements In the third quarter of 2020, we entered into several supply agreements with international government agencies, including agencies from which we had previously received deposits in the second quarter of 2020, to supply such agencies with mRNA-1273, our vaccine candidate against COVID-19. Pursuant to the supply agreements, we have promised to provide a certain quantity of doses, which we refer to as the Ordered Amount, based on anticipated delivery schedules. Certain agreements provide the ability to increase an agency’s Ordered Amount during specific periods of time. Each agency may have to pay an upfront for its Ordered Amount, and can receive a partial refund based on contractual provisions in such supply agreement that generally involve delivery delays, certain failures (delivery failures, clinical failures or failure to obtain market approvals) or the discontinuation of our worldwide clinical development of mRNA-1273. As of September 30, 2020, we had received cash of $569.0 million associated with such international supply agreements. Each supply agreement contains delivery and acceptance instructions. We continue to work with each applicable agency to confirm our distribution channel to each territory covered by such agreement. Accounting Treatment We determined that each supply agreement represents a transaction with a customer and therefore should be accounted for in accordance with ASC 606. We concluded that the delivery of each dose pursuant to a supply agreement represents a separate performance obligation and therefore we have multiple performance obligations under each contract. Options to increase the Ordered Amount are considered marketing offers and each will be accounted for as a separate contract upon the customer’s election. The total transaction price for each supply agreement equals the Ordered Amount multiplied by the fixed price per dose charged to the customer. Because the customer can reduce the Ordered Amount in certain circumstances based on the terms of the applicable supply agreement, we have concluded that the transaction price represents variable consideration. We have elected to not include sales and excise tax in the transaction price as an accounting election and any ancillary costs, to the extent billable to the customer, will be recorded as an offset to our related costs as such costs will be invoiced at cost. We will recognize revenue based on the fixed price per dose when control of the product has transferred to the customer and customer acceptance has occurred, unless such acceptance provisions are deemed perfunctory.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Financial Instruments	Financial Instruments Cash and Cash Equivalents and Investments The following tables summarize our cash and available-for-sale securities by significant investment category at September 30, 2020 and December 31, 2019 (in thousands): September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Current Marketable Securities Non- Current Marketable Securities Cash and cash equivalents $ 1,505,579 $ 2 $ — $ 1,505,581 $ 1,505,581 $ — $ — Available-for-sale: Level 2: Certificates of deposit 161,097 46 (1) 161,142 — 152,649 8,493 U.S. treasury securities 130,495 385 (1) 130,879 — 81,607 49,272 Debt securities of U.S. government agencies and corporate entities 2,165,133 6,043 (507) 2,170,669 — 1,536,465 634,204 $ 3,962,304 $ 6,476 $ (509) $ 3,968,271 $ 1,505,581 $ 1,770,721 $ 691,969 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Current Marketable Securities Non- Current Marketable Securities Cash and cash equivalents $ 225,874 $ — $ — $ 225,874 $ 225,874 $ — $ — Available-for-sale: Level 2: Certificates of deposit 82,028 79 (6) 82,101 10,002 69,197 2,902 U.S. treasury securities 117,891 260 (2) 118,149 — 110,186 7,963 Debt securities of U.S. government agencies and corporate entities 834,187 2,708 (32) 836,863 — 687,741 149,122 $ 1,259,980 $ 3,047 $ (40) $ 1,262,987 $ 235,876 $ 867,124 $ 159,987 The amortized cost and estimated fair value of marketable securities by contractual maturity at September 30, 2020 are as follows (in thousands): September 30, 2020 Amortized Cost Estimated Fair Value Due in one year or less $ 1,766,834 $ 1,770,721 Due after one year through five years 689,891 691,969 Total $ 2,456,725 $ 2,462,690 In accordance with our investment policy, we place investments in investment grade securities with high credit quality issuers, and generally limit the amount of credit exposure to any one issuer. We evaluate securities for impairment at the end of each reporting period. Impairment is evaluated considering numerous factors, and their relative significance varies depending on the situation. Factors considered include whether a decline in fair value below the amortized cost basis is due to credit-related factors or noncredit-related factors, the financial condition and near-term prospects of the issuer, and our intent and ability to hold the investment to allow for an anticipated recovery in fair value. Any impairment that is not credit related is recognized in other comprehensive (loss) income, net of applicable taxes. A credit-related impairment is recognized as an allowance on the balance sheet with a corresponding adjustment to earnings. We did not recognize any credit losses related to available-for-sale securities for the three and nine months ended September 30, 2020 and 2019. The following table summarizes the amount of gross unrealized losses and the estimated fair value for our available-for-sale securities in an unrealized loss position by length of time the securities have been in an unrealized loss position at September 30, 2020 and December 31, 2019 (in thousands): Less than 12 months 12 months or more Total Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value As of September 30, 2020: Certificates of deposit $ (1) $ 14,893 $ — $ — $ (1) $ 14,893 U.S. treasury securities (1) 15,341 — — (1) 15,341 Debt securities of U.S. government agencies and corporate entities (507) 729,249 — — (507) 729,249 Total $ (509) $ 759,483 $ — $ — $ (509) $ 759,483 As of December 31, 2019: Certificates of deposit $ (6) $ 12,822 $ — $ — $ (6) $ 12,822 U.S. treasury securities (2) 9,979 — — (2) 9,979 Debt securities of U.S. government agencies and corporate entities (32) 62,360 — — (32) 62,360 Total $ (40) $ 85,161 $ — $ — $ (40) $ 85,161 At September 30, 2020 and December 31, 2019, we held zero and 19 individual available-for-sale securities, respectively, out of our total investment portfolio that were in a continuous unrealized loss position. We neither intend to sell these investments nor conclude that we are more-likely-than-not that we will have to sell them before recovery of their carrying values. We also believe that we will be able to collect both principal and interest amounts due to us at maturity.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Down payments to manufacturing vendors $ 23,990 $ — Other prepaid expenses 62,434 8,475 Tenant incentives receivables 12,941 4,093 Interest receivable on marketable securities 10,011 6,835 Prepaid expenses and other current assets $ 109,376 $ 19,403 Property and Equipment, Net Property and equipment, net, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Laboratory equipment $ 113,326 $ 108,257 Leasehold improvements 163,793 152,426 Furniture, fixtures and other 4,613 3,316 Computer equipment and software 12,583 11,985 Internally developed software 7,020 7,020 Right-of-use asset, financing 56,348 9,853 Construction in progress 31,216 3,222 388,899 296,079 Less: Accumulated depreciation (111,990) (94,584) Property and equipment, net $ 276,909 $ 201,495 Depreciation and amortization expense for the three months ended September 30, 2020 and 2019 was $8.5 million and $7.3 million, respectively. Depreciation and amortization expense for the nine months ended September 30, 2020 and 2019 was $23.5 million and $22.0 million, respectively. Accrued Liabilities Accrued liabilities, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Clinical trials $ 44,554 $ 6,291 Development operations 24,187 2,567 Manufacturing 14,029 5,872 Other external goods and services 64,439 21,465 Compensation-related 48,788 27,428 Property and equipment 12,835 4,029 Accrued liabilities $ 208,832 $ 67,652 Deferred Revenue The following table summarizes the activities in deferred revenue for the nine months ended September 30, 2020 (in thousands): Deferred Revenue Balance at December 31, 2019 $ 202,305 Additions 1,293,370 Deductions (53,401) Balance at September 30, 2020 $ 1,442,274

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	Leases We have entered into various long-term non-cancelable lease arrangements for our facilities and equipment expiring at various times through 2032. Certain of these arrangements have free rent periods or escalating rent payment provisions. We recognize lease cost under such arrangements on a straight-line basis over the life of the leases. We have two campuses in Massachusetts, our Cambridge facility and our Moderna Technology Center (MTC), located in Norwood. Operating Leases Cambridge facility We occupy a multi-building campus in Technology Square in Cambridge, Massachusetts with a mix of offices and research laboratory space totaling approximately 175,000 square feet. Our Cambridge facility leases have expiry ranges from 2020 to 2029. In August 2019, we entered into an amendment to our lease agreements to consolidate our Technology Square space in Cambridge, Massachusetts. This included entering into a forward-starting lease agreement starting in January 2020 to acquire approximately 50,000 square feet of additional space at 200 Technology Square including space previously occupied under a sublease which expired on December 31, 2019. In addition, our current 200 Technology Square lease has been extended for two years to 2029. As part of the lease amendment, we completely exited our leased space of approximately 60,000 square feet at 500 Technology Square in May 2020. We record operating lease cost for each of our operating leases on a straight-line basis from lease commencement date through the end of the lease term. Operating lease cost is recorded to operating expenses in our consolidated statements of operations. Finance Leases Moderna Technology Center manufacturing facility (MTC South) In August 2016, we entered into a lease agreement for approximately 200,000 square feet of office, laboratory, and light manufacturing space, MTC South, in Norwood, Massachusetts. The lease will expire in September 2032. We have the option to extend the term for two extension periods of ten years each at market-based rents. The base rent is subject to increases over the term of the lease. Moderna Technology Center North (MTC North) In February 2019, we entered into a lease agreement for office and laboratory space of approximately 200,000 square feet, MTC North, located in Norwood, Massachusetts. The lease commenced in the second quarter of 2019 and had an initial expiration date of 2031. We have the option to extend the lease for up to four additional five-year terms. Contemporaneously, we entered into an agreement to sublease approximately 64 percent of the leased space to a third party. We have no rent obligations to the landlord for the space occupied by the third party. All sublease payments from the third party are paid directly to the landlord. In May 2020, we entered into an amendment to the lease whereby we exercised an option available in the original lease to receive a tenant improvement allowance in the amount of $22.2 million to be paid back over the term of the lease with interest and extend the term of the lease to 2035. In May 2020, we also amended our MTC North sublease agreement. As the result of that amendment, effective June 1, 2020, we obtained an additional, approximately 28,000 square feet, or 12 percent of the leased space in MTC North and the remainder of the space in July 2020 when the sublease expired. The lease modifications to MTC North in the second quarter of 2020 resulted in a change in lease classification, from operating to finance. Operating and financing lease right-of-use assets and lease liabilities as of September 30, 2020 and December 31, 2019 were as follows (in thousands): September 30, December 31, 2020 2019 Assets: Right-of-use assets, operating, net (1) (2) $ 91,684 $ 86,414 Right-of-use assets, financing, net (3) (4) 55,503 9,544 Total $ 147,187 $ 95,958 Liabilities: Current: Operating lease liabilities (5) $ 4,731 $ 3,584 Non-current: Operating lease liabilities, non-current 98,954 93,675 Financing lease liabilities, non-current 108,609 38,689 Total non-current lease liabilities 207,563 132,364 Total $ 212,294 $ 135,948 _______ (1) These assets are real estate related assets, which include land, office and laboratory spaces. (2) Net of accumulated depreciation. (3) These assets are real estate assets related to the MTC North and MTC South leases. (4) Included in property and equipment in the condensed consolidated balance sheets, net of accumulated depreciation. (5) Included in other current liabilities in the condensed consolidated balance sheets. The components of the lease costs for the three and nine months ended September 30, 2020 and 2019 were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Operating lease costs $ 3,962 $ 3,872 $ 12,977 $ 11,614 Financing lease costs: Amortization of right-of-use assets, financing leases 368 73 553 219 Interest expense for financing lease liabilities 2,843 1,644 6,385 4,901 Total financing lease costs $ 3,211 $ 1,717 $ 6,938 $ 5,120 Variable lease costs $ 1,120 $ 1,430 $ 3,618 $ 3,495 Supplemental cash flow information relating to our leases for the nine months ended September 30, 2020 and 2019 was as follows (in thousands): Nine Months Ended September 30, 2020 2019 Cash paid for amounts included in measurement of lease liabilities: Operating cash flows used in operating leases $ (11,314) $ (11,396) Operating cash flows used in financing leases (5,383) (4,161) Operating lease non-cash items: Right-of-use assets reduced through lease modifications and reassessments 6,755 16,242 Right-of-use assets obtained in exchange for operating lease liabilities 17,107 26,839 Finance lease non-cash items: Right-of-use assets obtained through lease modifications and reassessments 46,495 — Charges to financing lease obligation 39 741 Future minimum lease payments under non-cancelable operating lease agreements at September 30, 2020, are as follows (in thousands): Fiscal Year Operating Leases (1) Financing Leases (1) 2020 (remainder of the year) $ 2,770 $ 1,858 2021 15,492 11,634 2022 15,913 11,848 2023 16,008 12,054 2024 16,168 12,279 Thereafter 110,167 440,552 Total minimum lease payments 176,518 490,225 Less amounts representing interest or imputed interest (72,833) (381,616) (2) Present value of lease liabilities $ 103,685 $ 108,609 ______ (1) Includes optional extensions in the MTC South lease term which represent a total of $10.3 million and $208.5 million un-discounted future lease payments in operating leases and financing leases, respectively. Includes optional extensions in the MTC North lease term which represent a total of $110.3 million un-discounted future lease payments in financing leases. (2) MTC South interest is based on an imputed interest rate of 17.2%. MTC North interest is based upon an incremental borrowing rate of 8.2%.
Leases	Leases We have entered into various long-term non-cancelable lease arrangements for our facilities and equipment expiring at various times through 2032. Certain of these arrangements have free rent periods or escalating rent payment provisions. We recognize lease cost under such arrangements on a straight-line basis over the life of the leases. We have two campuses in Massachusetts, our Cambridge facility and our Moderna Technology Center (MTC), located in Norwood. Operating Leases Cambridge facility We occupy a multi-building campus in Technology Square in Cambridge, Massachusetts with a mix of offices and research laboratory space totaling approximately 175,000 square feet. Our Cambridge facility leases have expiry ranges from 2020 to 2029. In August 2019, we entered into an amendment to our lease agreements to consolidate our Technology Square space in Cambridge, Massachusetts. This included entering into a forward-starting lease agreement starting in January 2020 to acquire approximately 50,000 square feet of additional space at 200 Technology Square including space previously occupied under a sublease which expired on December 31, 2019. In addition, our current 200 Technology Square lease has been extended for two years to 2029. As part of the lease amendment, we completely exited our leased space of approximately 60,000 square feet at 500 Technology Square in May 2020. We record operating lease cost for each of our operating leases on a straight-line basis from lease commencement date through the end of the lease term. Operating lease cost is recorded to operating expenses in our consolidated statements of operations. Finance Leases Moderna Technology Center manufacturing facility (MTC South) In August 2016, we entered into a lease agreement for approximately 200,000 square feet of office, laboratory, and light manufacturing space, MTC South, in Norwood, Massachusetts. The lease will expire in September 2032. We have the option to extend the term for two extension periods of ten years each at market-based rents. The base rent is subject to increases over the term of the lease. Moderna Technology Center North (MTC North) In February 2019, we entered into a lease agreement for office and laboratory space of approximately 200,000 square feet, MTC North, located in Norwood, Massachusetts. The lease commenced in the second quarter of 2019 and had an initial expiration date of 2031. We have the option to extend the lease for up to four additional five-year terms. Contemporaneously, we entered into an agreement to sublease approximately 64 percent of the leased space to a third party. We have no rent obligations to the landlord for the space occupied by the third party. All sublease payments from the third party are paid directly to the landlord. In May 2020, we entered into an amendment to the lease whereby we exercised an option available in the original lease to receive a tenant improvement allowance in the amount of $22.2 million to be paid back over the term of the lease with interest and extend the term of the lease to 2035. In May 2020, we also amended our MTC North sublease agreement. As the result of that amendment, effective June 1, 2020, we obtained an additional, approximately 28,000 square feet, or 12 percent of the leased space in MTC North and the remainder of the space in July 2020 when the sublease expired. The lease modifications to MTC North in the second quarter of 2020 resulted in a change in lease classification, from operating to finance. Operating and financing lease right-of-use assets and lease liabilities as of September 30, 2020 and December 31, 2019 were as follows (in thousands): September 30, December 31, 2020 2019 Assets: Right-of-use assets, operating, net (1) (2) $ 91,684 $ 86,414 Right-of-use assets, financing, net (3) (4) 55,503 9,544 Total $ 147,187 $ 95,958 Liabilities: Current: Operating lease liabilities (5) $ 4,731 $ 3,584 Non-current: Operating lease liabilities, non-current 98,954 93,675 Financing lease liabilities, non-current 108,609 38,689 Total non-current lease liabilities 207,563 132,364 Total $ 212,294 $ 135,948 _______ (1) These assets are real estate related assets, which include land, office and laboratory spaces. (2) Net of accumulated depreciation. (3) These assets are real estate assets related to the MTC North and MTC South leases. (4) Included in property and equipment in the condensed consolidated balance sheets, net of accumulated depreciation. (5) Included in other current liabilities in the condensed consolidated balance sheets. The components of the lease costs for the three and nine months ended September 30, 2020 and 2019 were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Operating lease costs $ 3,962 $ 3,872 $ 12,977 $ 11,614 Financing lease costs: Amortization of right-of-use assets, financing leases 368 73 553 219 Interest expense for financing lease liabilities 2,843 1,644 6,385 4,901 Total financing lease costs $ 3,211 $ 1,717 $ 6,938 $ 5,120 Variable lease costs $ 1,120 $ 1,430 $ 3,618 $ 3,495 Supplemental cash flow information relating to our leases for the nine months ended September 30, 2020 and 2019 was as follows (in thousands): Nine Months Ended September 30, 2020 2019 Cash paid for amounts included in measurement of lease liabilities: Operating cash flows used in operating leases $ (11,314) $ (11,396) Operating cash flows used in financing leases (5,383) (4,161) Operating lease non-cash items: Right-of-use assets reduced through lease modifications and reassessments 6,755 16,242 Right-of-use assets obtained in exchange for operating lease liabilities 17,107 26,839 Finance lease non-cash items: Right-of-use assets obtained through lease modifications and reassessments 46,495 — Charges to financing lease obligation 39 741 Future minimum lease payments under non-cancelable operating lease agreements at September 30, 2020, are as follows (in thousands): Fiscal Year Operating Leases (1) Financing Leases (1) 2020 (remainder of the year) $ 2,770 $ 1,858 2021 15,492 11,634 2022 15,913 11,848 2023 16,008 12,054 2024 16,168 12,279 Thereafter 110,167 440,552 Total minimum lease payments 176,518 490,225 Less amounts representing interest or imputed interest (72,833) (381,616) (2) Present value of lease liabilities $ 103,685 $ 108,609 ______ (1) Includes optional extensions in the MTC South lease term which represent a total of $10.3 million and $208.5 million un-discounted future lease payments in operating leases and financing leases, respectively. Includes optional extensions in the MTC North lease term which represent a total of $110.3 million un-discounted future lease payments in financing leases. (2) MTC South interest is based on an imputed interest rate of 17.2%. MTC North interest is based upon an incremental borrowing rate of 8.2%.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Strategic Collaborations Under our strategic collaboration agreements, we are committed to perform certain research, development, and manufacturing activities. As part of our PCV Agreement and PCV/SAV Agreement with Merck, we are committed to perform certain research, development and manufacturing activities related to PCV products through an initial Phase 2 clinical trial up to a budgeted amount of $243.0 million for both periods as of September 30, 2020 and December 31, 2019 (see Note 4). Legal Proceedings We are not currently a party to any material legal proceedings. Indemnification Obligations As permitted under Delaware law, we indemnify our officers, directors, and employees for certain events, occurrences while the officer, or director is, or was, serving at our request in such capacity. The term of the indemnification is for the officer’s or director’s lifetime. We have standard indemnification arrangements in our leases for laboratory and office space that require us to indemnify the landlord against any liability for injury, loss, accident, or damage from any claims, actions, proceedings, or costs resulting from certain acts, breaches, violations, or non-performance under our leases. We enter into indemnification provisions under our agreements with counterparties in the ordinary course of business, typically with business partners, contractors, clinical sites and customers. Under these provisions, we generally indemnify and hold harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of our activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments we could be required to make under these indemnification provisions is unlimited. Through the three months ended September 30, 2020 and the year ended December 31, 2019, we had not experienced any losses related to these indemnification obligations, and no material claims were outstanding. We do not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related reserves were established. Purchase Commitments and Purchase Orders In May 2020, we entered into a 10-year strategic collaboration agreement with Lonza Ltd. to enable larger scale manufacture for our mRNA vaccine candidate, mRNA-1273, against the SARS-CoV-2 virus and additional Moderna products in the future. This agreement was reflected in the Global Long Term Agreement entered into between Moderna and Lonza on September 4, 2020. Under the terms of the agreement, we plan to establish dedicated manufacturing suites at Lonza’s facilities in the United States and Switzerland for the manufacture of mRNA-1273 at both sites. Certain arrangements under this strategic collaboration agreement are within the scope of lease accounting (Lonza leases). However, we did not recognize any right-of-use assets or lease liabilities related to Lonza leases as of September 30, 2020, as the leases had not yet commenced or the lease terms were less than 12 months. The non-cancelable contractual obligations related to the Lonza agreement, including the early termination fees, are included in our non-cancelable purchase commitments related to supply and manufacturing agreements of $613.9 million below. We enter into agreements in the normal course of business with vendors for preclinical research studies and clinical trials and with contract manufacturing organizations (CMOs) for supply and manufacturing. As of September 30, 2020, we h ad $16.9 million of non-cancelable purchase commitments for clinical services which are expected to be paid from 2020 to 2023. As of September 30, 2020, we had $613.9 million of non-c ancelable purchase commitments related to supply and manufacturing agreements which are expected to be paid through 2021. These amounts represent our minimum contractual obligations, including termination fees. In addition to purchase commitments, we have agreements with third parties for various services, including services related to clinical operations and support and contract manufacturing, for which we are not contractually able to terminate for convenience and avoid any and all future obligations to the vendors. Certain agreements provide for termination rights subject to termination fees or wind down costs. Under such agreements, we are contractually obligated to make certain payments to vendors, mainly, to reimburse them for their unrecoverable outlays incurred prior to cancellation. At September 30, 2020 and December 31, 2019, we had cancelable open purchase orders of $747.9 million and $105.9 million, respectively, in total under such agreements for our significant clinical operations and support and contract manufacturing. These amounts represent only our estimate of those items for which we had a contractual commitment to pay at September 30, 2020 and December 31, 2019, assuming we would not cancel these agreements. The actual amounts we pay in the future to the vendors under such agreements may differ from the purchase order amounts.

Shareholders' Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Shareholders' Equity	Shareholders' Equity On February 28, 2018 and May 7, 2018, the Board of Directors approved an amendment to our Certificate of Incorporation resulting in a total of 775,000,000 shares of common stock and a total of 509,352,795 shares of redeemable convertible preferred stock being authorized, respectively. Upon completion of our initial public offering (IPO), our authorized capital stock consists of 1,600,000,000 shares of common stock, par value $0.0001 per share, and 162,000,000 shares of preferred stock, par value $0.0001 per share, all of which shares of preferred stock are undesignated. On December 11, 2018, we completed our IPO, whereby we sold 26,275,993 shares of common stock at a price of $23.00 per share. The aggregate net proceeds received by us from the IPO were $563.0 million, net of underwriting discounts and commissions of $33.2 million and offering expenses of $8.1 million payable by us. Upon the closing of the IPO, all outstanding shares of our redeemable convertible preferred stock were converted into 236,012,913 shares of the common stock. On February 14, 2020, we sold 26,315,790 shares of common stock at a price of $19.00 per share through a public equity offering. The aggregate net proceeds from the offering were $477.7 million, net of underwriting discounts, commissions and offering expenses. In addition, the underwriters exercised their options to purchase an additional 3,947,368 shares of common stock at the public offering price less underwriting discounts, resulting in additional net proceeds of $71.8 million. On May 21, 2020, we sold 17,600,000 shares of common stock at a price of $76.00 per share through a public equity offering. The aggregate net proceeds from the offering were $1.30 billion, net of underwriting discounts, commissions and offering expenses.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation Equity Plans In October 2013, we adopted the 2013 Equity Incentive Plan (the 2013 Incentive Plan) and the 2013 Unit Option and Grant Plan (the 2013 Option Plan), which provided for the grant of incentive units, non-qualified unit options, and restricted and unrestricted unit awards to our employees, officers, directors, advisors, and outside consultants. Historically, we also granted restricted stock to founders, officers, directors, and advisors outside any of the Plans. In August 2016, we adopted the 2016 Stock Option and Grant Plan (the 2016 Equity Plan), which replaced the 2013 Option Plan and the 2013 Incentive Plan. The 2016 Equity Plan and provided for the grant of incentive stock options, non-qualified stock options, restricted stock, unrestricted stock, and restricted stock units to our employees, officers, directors, consultants, and other key persons. In connection with the IPO, we adopted the 2018 Stock Option and Incentive Plan (the 2018 Equity Plan) in November 2018. The 2018 Equity Plan became effective on the date immediately prior to the effective date of the IPO and replaced our 2016 Plan. The 2018 Equity Plan provides flexibility to our compensation committee to use various equity-based incentive awards as compensation tools to motivate our workforce. We have initially reserved 13,000,000 shares of our common stock for the issuance of awards under the 2018 Equity Plan. The 2018 Equity Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2019, by 4 percent of the outstanding number of our common stock on the immediately preceding December 31, or such lesser number of shares as determined by our compensation committee. The shares of common stock underlying any awards that are forfeited, canceled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by us prior to vesting, satisfied without any issuance of stock, expire or are otherwise terminated (other than by exercise) under the 2018 Equity Plan and the 2016 Plan will be added back to the shares of common stock available for issuance under the 2018 Equity Plan. The terms and conditions of stock-based awards are defined at the sole discretion of our Board of Directors. We issue service-based awards, vesting over a defined period of service, and performance-based awards, vesting upon achievement of defined conditions. Service based awards generally vest over a four-year period, with the first 25% of such awards vesting following twelve months of continued employment or service. The remaining awards vests in twelve quarterly installments over the following twelve quarters. Stock options granted under the 2016 Equity Plan expire ten years from the date of grant and the exercise price must be at least equal to the fair market value of common stock on the grant date. As of September 30, 2020, we had a total of 67.5 million shares reserved for future issuance under our Equity Plans, of which 39.4 million shares were reserved for equity awards previously granted, and 28.1 million shares were available for future grants under the 2018 Equity Plan. No additional awards will be granted under the 2016 Equity Plan as it was replaced by the 2018 Equity Plan. Options We have granted options generally through the 2018 Equity Plan and 2016 Equity Plan. The following table summarizes our option activity during the nine months ended September 30, 2020: Number of Options Weighted- Average Exercise Price per Share Weighted- Average Grant Date Fair Value per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (1) (in thousands) Outstanding at Outstanding at December 31, 2019 45,536,915 $ 13.82 $ 7.35 7.2 years $ 286,310 Granted 4,809,336 33.79 18.10 Exercised (10,613,303) 12.57 6.32 Canceled/forfeited (2,471,131) 17.78 10.39 Outstanding at September 30, 2020 37,261,817 16.49 8.82 7.0 years 2,022,154 Exercisable at September 30, 2020 18,348,695 10.96 5.61 5.6 years 1,097,117 Expected to vest at September 30, 2020 18,913,122 21.86 11.94 8.3 years 926,598 _______ (1) Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those options in the money as of September 30, 2020. For the nine months ended September 30, 2020, 10.6 million stock options were exercised. The total intrinsic value of options exercised was $434.9 million for the nine months ended September 30, 2020. The aggregate intrinsic value represents the difference between the exercise price and the selling price received by option holders upon the exercise of stock options during the period. The total consideration recorded as a result of stock option exercises was approximately $133.4 million for the nine months ended September 30, 2020. Restricted Common Stock Units We have granted restricted stock unit awards generally through the 2018 Equity Plan and 2016 Equity Plan. The following table summarizes our restricted stock unit activity during the nine months ended September 30, 2020: Units Weighted-Average Outstanding, non-vested at December 31, 2019 1,177,249 $ 19.01 Issued 1,386,066 34.29 Vested (203,488) 20.46 Canceled/forfeited (187,650) 22.69 Outstanding, non-vested at September 30, 2020 2,172,177 28.37 2018 Employee Stock Purchase Plan In November 2018, we adopted our 2018 Employee Stock Purchase Plan (ESPP), which became effective on December 5, 2018. The ESPP initially reserved and authorized the issuance of up to a total of 810,000 shares of common stock to participating employees. The ESPP provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, by the lesser of 3,240,000 shares of common stock, one percent of the outstanding number of our common stock on the immediately preceding December 31, or such lesser number of shares as determined by our compensation committee. We make one or more offerings, consisting of one or more purchase periods, each year to our employees to purchase shares under the ESPP. Offerings usually begin every six months and will continue for six-month periods, referred to as offering periods. The purchase price at which shares are sold under the ESPP is equal to 85% of the lower of the fair market value of the shares on the first business day of the offering period or the last business day of the purchase period. Employees are generally eligible to participate through payroll deductions of between 1% to 50% of their compensation and may not purchase more than 3,000 shares of common stock during each purchase period or $25,000 worth of shares of common stock in any calendar year. We began our first ESPP offering on June 1, 2019. There were 173,738 shares sold at an average price of $16.80 per share under the ESPP during the nine months ended September 30, 2020. As of September 30, 2020, 3.7 million shares were available for future issuance under the ESPP. Valuation and Stock-Based Compensation Expense Stock-based compensation for options granted under our Equity Plans and share purchases under our ESPP are determined using the Black-Scholes option pricing model. The weighted-average assumptions used to estimate the fair value of options and ESPP granted for the nine months ended September 30, 2020 and 2019 are as follows: Weighted Average Nine Months Ended September 30, 2020 2019 Options: Risk-free interest rate 0.85 % 2.39 % Expected term 6.11 years 6.07 years Expected volatility 57.82 % 62 % Expected dividends — % — % Weighted average fair value per share $ 18.10 $ 11.71 ESPP: Risk-free interest rate 0.18 % 2.31 % Expected term 0.50 years 0.50 years Expected volatility 65 % 50 % Expected dividends — % — % Weighted average fair value per share $ 20.64 $ 19.85 The following table presents the components and classification of stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Options $ 18,924 $ 18,994 $ 57,365 $ 56,475 Restricted common stock units 3,404 1,291 8,098 3,628 ESPP 878 519 2,079 693 Total $ 23,206 $ 20,804 $ 67,542 $ 60,796 Research and development $ 14,022 $ 12,616 $ 40,761 $ 36,268 General and administrative 9,184 8,188 26,781 24,528 Total $ 23,206 $ 20,804 $ 67,542 $ 60,796 As of September 30, 2020, there was $236.9 million of total unrecognized compensation cost related to unvested stock-based compensation with respect to options and restricted stock granted. That cost is expected to be recognized over a weighted-average period of 2.98 years at September 30, 2020.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial reporting and tax basis of assets and liabilities. These differences are measured using the enacted statutory tax rates that are expected to be in effect for the years in which differences are expected to reverse. Valuation allowances are provided when the expected realization of deferred tax assets does not meet a “more likely than not” criterion. Realization of our deferred tax assets is dependent upon the generation of future taxable income, the amount and timing of which are uncertain. We continued to maintain a full valuation allowance against all of our deferred tax assets based on management’s evaluation of all available evidence. During the three and nine months ended September 30, 2020, we recorded an income tax provision of $0.9 million and $1.1 million, respectively, primarily related to withholding taxes on a foreign collaboration agreement upfront payment. There were no significant income tax provisions or benefits for the three and nine months ended September 30, 2019.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic and diluted net loss per share for the three and nine months ended September 30, 2020 and 2019 are calculated as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (233,636) $ (123,215) $ (474,579) $ (390,731) Denominator: Weighted average common shares used in net loss per share, basic and diluted 394,682,744 330,769,341 376,174,283 329,592,322 Net loss per share, basic and diluted $ (0.59) $ (0.37) $ (1.26) $ (1.19) The following common stock equivalents, presented based on amounts outstanding as of September 30, 2020 and 2019, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because their inclusion would have been anti-dilutive: September 30, 2020 2019 Stock options 37,261,817 48,962,655 Restricted common stock — 21,564 Restricted common stock units 2,172,177 1,659,187 39,433,994 50,643,406

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent to September 30, 2020, we entered into an additional supply agreement with an international government agency to provide mRNA-1273 supply, our vaccine candidate against COVID-19, up to 50.0 million doses.On October 7, 2020, the Master Collaboration and License Agreement between us and Merck related to our collaboration on RSV was terminated by mutual agreement. The termination did not have an impact to our condensed consolidated financial statements as of and for the three and nine months ended September 30, 2020.

Summary of Basis of Presentat_2

Summary of Basis of Presentation and Recent Accounting Standards (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	The accompanying unaudited condensed consolidated financial statements that accompany these notes have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and applicable rules and regulations of the Securities and Exchange Commission (SEC) for interim financial reporting, consistent in all material respects with those applied in our Annual Report on Form 10-K for the year ended December 31, 2019 (2019 Form 10-K). Any reference in these notes to applicable guidance is meant to refer to the authoritative accounting principles generally accepted in the United States as found in the Accounting Standard Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). This report should be read in conjunction with the consolidated financial statements in our 2019 Form 10-K. The consolidated financial statements include the Company and its subsidiaries. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	We have made estimates and judgments affecting the amounts reported in our condensed consolidated financial statements and the accompanying notes. On an ongoing basis, we evaluate our estimates, including critical accounting policies or estimates related to revenue recognition, research and development expenses, income tax provisions, stock-based compensation, leases, and useful lives of long-lived assets. We base our estimates on historical experience and on various relevant assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. The actual results that we experience may differ materially from our estimates. Significant estimates relied upon in preparing these financial statements include, among others, those related to fair value of equity awards, revenue recognition, research and development expenses, leases, fair value instruments, useful lives of property and equipment, income taxes, and our valuation allowance on our deferred tax assets.
Comprehensive Loss	Comprehensive loss includes net loss and other comprehensive (loss) income for the period. Other comprehensive (loss) income consists of unrealized gains and losses on our investments. Total comprehensive loss for all periods presented has been disclosed in the condensed consolidated statements of comprehensive loss.
Restricted cash	We include our restricted cash balance in the cash, cash equivalents and restricted cash reconciliation of operating, investing and financing activities in the condensed consolidated statements of cash flows.
Pre-Launch Inventory	Pre-Launch Inventory Prior to an initial regulatory approval for our investigational medicines, we expense costs relating to production of inventory as research and development expense in our condensed consolidated statements of operations, in the period incurred. When we believe regulatory approval and subsequent commercialization of our investigational medicines is probable, and we also expect future economic benefit from the sales of the investigational medicines to be realized, we will then capitalize the costs of production as inventory.
Recently Adopted Accounting Standards and Recently Issued Accounting Standards	Recently Adopted Accounting Standards In June 2016, the FASB issued ASU No. 2016-13, Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard changes how companies account for credit losses for most financial assets and certain other instruments. For trade receivables, loans and held-to-maturity debt securities, companies will be required to recognize an allowance for credit losses rather than reducing the carrying value of the asset. The amendments in this standard should be applied on a modified retrospective basis to all periods presented. We adopted this standard in the first quarter of 2020. Based on the composition of our investment portfolio and investment policy, the adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Topic 350): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This standard requires capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). We adopted this standard in the first quarter of 2020 using the prospective method. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes . This standard removes certain exceptions for investments, intra-period allocations and interim calculations, and adds guidance to reduce complexity in accounting for income taxes. We early adopted this standard in the second quarter of 2020. The adoption of this standard did not have a material impact on our consolidated financial statements and disclosures. Recently Issued Accounting Standards From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies and adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on our consolidated financial statements and disclosures.

Summary of Basis of Presentat_3

Summary of Basis of Presentation and Recent Accounting Standards (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Effect of Adoption of 842 on Condensed Financial Statements	The following tables summarize the effects of adopting ASC 842 on our condensed consolidated financial statements for the three and nine months ended September 30, 2019 (in thousands, except per share data): Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ASC 842 ASC 842 Previously reported Adjustments As adjusted Previously reported Adjustments As adjusted Operating expenses: Research and development $ 119,715 $ (78) $ 119,637 $ 378,786 $ (431) $ 378,355 General and administrative 28,188 (15) 28,173 83,994 (81) 83,913 Total operating expenses 147,903 (93) 147,810 462,780 (512) 462,268 Loss from operations (130,857) 93 (130,764) (416,626) 512 (416,114) Other expense, net (1,767) (114) (1,881) (5,351) (338) (5,689) Loss before benefit from income taxes (123,372) (21) (123,393) (391,431) 174 (391,257) Net loss (123,194) (21) (123,215) (390,905) 174 (390,731) Net loss per share attributable to common stockholders, basic and diluted (0.37) — (0.37) (1.19) — (1.19) Nine Months Ended September 30, 2019 Previously reported ASC 842 Adjustment during the period As adjusted Operating activities Net loss $ (390,905) $ 174 $ (390,731) Depreciation and amortization 22,082 (36) 22,046 Prepaid expenses and other assets (1,407) 3,220 1,813 Right-of-use assets, operating leases — (7,970) (7,970) Deferred lease obligation 3,844 (3,844) — Operating lease liabilities — 13,475 13,475 Other liabilities 1,617 (1,770) (153) Net cash used in operating activities (363,195) 3,249 (359,946) Financing activities Reimbursement of assets under lease financing obligation 3,678 (3,678) — Charges to financing lease obligation — 741 741 Payments on financing lease obligation 312 (312) — Net cash provided by financing activities 23,531 (3,249) 20,282
Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive (loss) income for the three and nine months ended September 30, 2020 are as follows (in thousands): Unrealized (Loss) Gain on Available-for-Sale Debt Securities Accumulated other comprehensive income, balance at December 31, 2019 $ 1,804 Other comprehensive loss (7,931) Accumulated other comprehensive loss, balance at March 31, 2020 (6,127) Other comprehensive income 14,383 Accumulated other comprehensive income, balance at June 30, 2020 8,256 Other comprehensive loss (3,472) Accumulated other comprehensive income, balance at September 30, 2020 $ 4,784
Reconciliation of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and restricted cash in the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 1,505,581 $ 173,711 Restricted cash 1,032 1,032 Restricted cash, non-current 11,053 10,791 Total cash, cash equivalents and restricted cash shown in the condensed consolidated $ 1,517,666 $ 185,534
Reconciliation of Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash in the condensed consolidated balance sheets that sum to the total of the same such amounts shown in the condensed consolidated statements of cash flows (in thousands): September 30, 2020 2019 Cash and cash equivalents $ 1,505,581 $ 173,711 Restricted cash 1,032 1,032 Restricted cash, non-current 11,053 10,791 Total cash, cash equivalents and restricted cash shown in the condensed consolidated $ 1,517,666 $ 185,534

Grant Revenue (Tables)

Grant Revenue (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue Recognition and Deferred Revenue [Abstract]
Disaggregation of Revenue	The following tables summarize grant revenue and deferred grant revenue as of and for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 BARDA $ 143,318 $ 1,135 $ 183,134 $ 4,500 Other grant revenue 2,376 2,573 4,401 4,171 Total grant revenue $ 145,694 $ 3,708 $ 187,535 $ 8,671 September 30, December 31, 2020 2019 Deferred grant revenue $ 5,670 $ 1,496 The following table summarizes our total consolidated net revenue from our strategic collaborators for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Collaboration Revenue by Strategic Collaborator: 2020 2019 2020 2019 AstraZeneca $ 48 $ 3,724 $ 17,202 $ 4,726 Merck 6,718 9,110 18,060 28,456 Vertex 5,450 504 9,698 4,301 Other — — 155 — Total collaboration revenue $ 12,216 $ 13,338 $ 45,115 $ 37,483 The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Combined AZ Agreements $ 49 $ 3,552 $ 2,950 $ 4,580 The following table summarizes the revenue and contra-revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Contra-revenue under the May 2019 Amendment $ (1,074) $ (1,657) $ (5,513) $ (3,796) Collaboration revenue under the 2015 Merck Agreement — (188) 12 666 Total contra-revenue $ (1,074) $ (1,845) $ (5,501) $ (3,130)

Collaboration Revenue (Tables)

Collaboration Revenue (Tables)	9 Months Ended
	Sep. 30, 2020
Research and Development [Abstract]
Disaggregation of Revenue	The following tables summarize grant revenue and deferred grant revenue as of and for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 BARDA $ 143,318 $ 1,135 $ 183,134 $ 4,500 Other grant revenue 2,376 2,573 4,401 4,171 Total grant revenue $ 145,694 $ 3,708 $ 187,535 $ 8,671 September 30, December 31, 2020 2019 Deferred grant revenue $ 5,670 $ 1,496 The following table summarizes our total consolidated net revenue from our strategic collaborators for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, Collaboration Revenue by Strategic Collaborator: 2020 2019 2020 2019 AstraZeneca $ 48 $ 3,724 $ 17,202 $ 4,726 Merck 6,718 9,110 18,060 28,456 Vertex 5,450 504 9,698 4,301 Other — — 155 — Total collaboration revenue $ 12,216 $ 13,338 $ 45,115 $ 37,483 The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Combined AZ Agreements $ 49 $ 3,552 $ 2,950 $ 4,580 The following table summarizes the revenue and contra-revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Contra-revenue under the May 2019 Amendment $ (1,074) $ (1,657) $ (5,513) $ (3,796) Collaboration revenue under the 2015 Merck Agreement — (188) 12 666 Total contra-revenue $ (1,074) $ (1,845) $ (5,501) $ (3,130)
Changes in Balances of Receivables and Contract Liabilities	The following table presents changes in the balances of our receivables and contract liabilities related to our strategic collaboration agreements during the nine months ended September 30, 2020 (in thousands): December 31, 2019 Additions Deductions September 30, 2020 Contract Assets: Accounts receivable $ 1,972 $ 115,037 $ (85,354) $ 31,655 Contract Liabilities: Deferred revenue $ 199,528 $ 117,002 $ (50,320) $ 266,210 During the three and nine months ended September 30, 2020, we recognized the following revenue as a result of the change in the contract liability balances related to our collaboration agreements (in thousands): Revenue recognized in the period from: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Amounts included in contract liabilities at the beginning of the period (1) $ 13,263 $ 50,320 Performance obligations satisfied (or partially satisfied) in previous reporting periods (2) — 1,262 ______ (1) We first allocate revenue to the individual contract liability balance outstanding at the beginning of the period until the revenue exceeds that balance. If additional consideration is received on those contracts in subsequent periods, we assume all revenue recognized in the reporting period is first applied to the beginning contract liability. (2) Related to changes in estimated costs for our future performance obligations and estimated variable considerations. The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the services are expected to be performed or control of the supply is expected to be transferred (in thousands): September 30, 2020 December 31, 2019 Combined AZ Agreements $ 72,266 $ 73,669 Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 2016 VEGF Exercise $ — $ 172 $ 14,253 $ 146 The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the control of the supply is expected to be transferred for the periods presented (in thousands): September 30, 2020 December 31, 2019 2016 VEGF Exercise $ 29,335 $ 41,266 Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 PCV/SAV Agreement $ 7,792 $ 10,944 $ 23,561 $ 31,575 The following table summarizes the balances of deferred revenue, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the services are expected to be performed or control of the supply is expected to be transferred for the periods presented (in thousands): September 30, 2020 December 31, 2019 PCV/SAV Agreement $ 60,548 $ 83,799 The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Vertex First Extended Research Term $ 5,449 $ — $ 7,645 $ — Vertex Agreement/2019 Amendment — 504 2,052 4,301 Total $ 5,449 $ 504 $ 9,697 $ 4,301 The following table summarizes the balances of deferred revenue, classified as current and non-current in the condensed consolidated balance sheets based on the term of the research period for the periods presented (in thousands): September 30, 2020 December 31, 2019 Vertex Agreement 1 $ 4,061 $ 793 ____________ (1) Balance as of December 31, 2019 represents deferred revenue related to the Vertex 2019 Amendment The following table summarizes the activities in deferred revenue for the nine months ended September 30, 2020 (in thousands): Deferred Revenue Balance at December 31, 2019 $ 202,305 Additions 1,293,370 Deductions (53,401) Balance at September 30, 2020 $ 1,442,274
Summary of Composition of the Total Transaction	The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, Combined 2018 AZ Agreements: 2020 2019 Upfront payments $ 240,000 $ 240,000 Sublicense reimbursement 1,000 1,000 Toxicity milestone payment 60,000 60,000 Competition milestone payment 60,000 60,000 Estimated reimbursement for IL-12 manufacturing obligations 38,089 40,782 Total $ 399,089 $ 401,782 The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, 2016 VEGF Exercise: 2020 2019 Option exercise fee $ 10,000 $ 10,000 Milestone payment 30,000 30,000 Sublicense reimbursement 2,250 2,250 Estimated reimbursement for clinical supply 18,062 15,621 Total $ 60,312 $ 57,871 The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, 2015 Merck Agreement: 2020 2019 Upfront payments $ 60,000 $ 60,000 Development milestones 5,000 5,000 Reduction of reimbursements paid to Merck (10,778) (5,265) Total $ 54,222 $ 59,735 The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price September 30, December 31, PCV/SAV Agreement: 2020 2019 Upfront payment $ 200,000 $ 200,000 Premium associated with the contemporaneous sale of Series H redeemable convertible 13,050 13,050 Reimbursement for clinical supply 310 — Total $ 213,360 $ 213,050 The following table summarizes the composition of the total transaction price for the First Extended Research Term at September 30, 2020 (in thousands): Transaction Price Vertex Agreement - First Extended Research Term: September 30, 2020 Upfront payment $ 4,000 Research and development 46,410 Total $ 50,410 The following table summarizes the composition of the total transaction price for the periods presented (in thousands): Transaction Price Chiesi Agreement: September 30, 2020 Upfront payment $ 25,000 Estimated reimbursement for research and development 17,656 Total $ 42,656
Summary of Total Transaction Price to the Identified Performance Obligations	The following table summarizes the allocation of the total transaction price to the identified performance obligations under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price Combined 2018 AZ Agreements: September 30, 2020 Combined 2018 AZ Agreement performance obligation $ 293,223 Preclinical development service - IL-12 8,133 Preclinical development service - oncology development target 8,133 Development and commercialization license and manufacturing obligation 88,009 Material right to receive development and commercialization rights 1,591 Total $ 399,089 Remaining unsatisfied performance obligation $ 104,945 The following table summarizes the total transaction price allocated to the single identified performance obligation under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price September 30, 2020 2016 VEGF Exercise combined performance obligation $ 60,312 Remaining unsatisfied performance obligation 41,877 The following table summarizes the total transaction price allocated to the combined performance obligation under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price September 30, 2020 2015 Merck Agreement $ 54,222 Remaining unsatisfied performance obligation — The following tables summarize the allocation of the total transaction price to the identified performance obligations under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price PCV/SAV Agreement: September 30, 2020 PCV performance obligation $ 206,356 KRAS performance obligation 7,004 Total $ 213,360 Remaining unsatisfied performance obligation $ 60,548 The following table summarizes the total transaction price allocated to the single performance obligation under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction Price September 30, 2020 First Extended Research Term transaction price $ 50,410 Remaining unsatisfied performance obligation 42,766 The following table summarizes the allocation of the transaction price to the identified performance obligations under the arrangement, and the amount of the transaction price unsatisfied as of September 30, 2020 (in thousands): Transaction price Chiesi Agreement: September 30, 2020 Research and development $ 17,656 Material right for the first product development and commercialization license 17,500 Material right for the second product development and commercialization license 7,500 Total $ 42,656 Remaining unsatisfied performance obligation $ 42,656

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Summary of Cash and Available-for-Sale Securities by Significant Investment Category	The following tables summarize our cash and available-for-sale securities by significant investment category at September 30, 2020 and December 31, 2019 (in thousands): September 30, 2020 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Current Marketable Securities Non- Current Marketable Securities Cash and cash equivalents $ 1,505,579 $ 2 $ — $ 1,505,581 $ 1,505,581 $ — $ — Available-for-sale: Level 2: Certificates of deposit 161,097 46 (1) 161,142 — 152,649 8,493 U.S. treasury securities 130,495 385 (1) 130,879 — 81,607 49,272 Debt securities of U.S. government agencies and corporate entities 2,165,133 6,043 (507) 2,170,669 — 1,536,465 634,204 $ 3,962,304 $ 6,476 $ (509) $ 3,968,271 $ 1,505,581 $ 1,770,721 $ 691,969 December 31, 2019 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Cash and Cash Equivalents Current Marketable Securities Non- Current Marketable Securities Cash and cash equivalents $ 225,874 $ — $ — $ 225,874 $ 225,874 $ — $ — Available-for-sale: Level 2: Certificates of deposit 82,028 79 (6) 82,101 10,002 69,197 2,902 U.S. treasury securities 117,891 260 (2) 118,149 — 110,186 7,963 Debt securities of U.S. government agencies and corporate entities 834,187 2,708 (32) 836,863 — 687,741 149,122 $ 1,259,980 $ 3,047 $ (40) $ 1,262,987 $ 235,876 $ 867,124 $ 159,987
Amortized Cost and Estimated Fair Value of Marketable Securities, by Contractual Maturity	The amortized cost and estimated fair value of marketable securities by contractual maturity at September 30, 2020 are as follows (in thousands): September 30, 2020 Amortized Cost Estimated Fair Value Due in one year or less $ 1,766,834 $ 1,770,721 Due after one year through five years 689,891 691,969 Total $ 2,456,725 $ 2,462,690
Schedule of Unrealized Loss on Investments	The following table summarizes the amount of gross unrealized losses and the estimated fair value for our available-for-sale securities in an unrealized loss position by length of time the securities have been in an unrealized loss position at September 30, 2020 and December 31, 2019 (in thousands): Less than 12 months 12 months or more Total Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value As of September 30, 2020: Certificates of deposit $ (1) $ 14,893 $ — $ — $ (1) $ 14,893 U.S. treasury securities (1) 15,341 — — (1) 15,341 Debt securities of U.S. government agencies and corporate entities (507) 729,249 — — (507) 729,249 Total $ (509) $ 759,483 $ — $ — $ (509) $ 759,483 As of December 31, 2019: Certificates of deposit $ (6) $ 12,822 $ — $ — $ (6) $ 12,822 U.S. treasury securities (2) 9,979 — — (2) 9,979 Debt securities of U.S. government agencies and corporate entities (32) 62,360 — — (32) 62,360 Total $ (40) $ 85,161 $ — $ — $ (40) $ 85,161

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Down payments to manufacturing vendors $ 23,990 $ — Other prepaid expenses 62,434 8,475 Tenant incentives receivables 12,941 4,093 Interest receivable on marketable securities 10,011 6,835 Prepaid expenses and other current assets $ 109,376 $ 19,403
Schedule of Property and Equipment, Net	Property and equipment, net, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Laboratory equipment $ 113,326 $ 108,257 Leasehold improvements 163,793 152,426 Furniture, fixtures and other 4,613 3,316 Computer equipment and software 12,583 11,985 Internally developed software 7,020 7,020 Right-of-use asset, financing 56,348 9,853 Construction in progress 31,216 3,222 388,899 296,079 Less: Accumulated depreciation (111,990) (94,584) Property and equipment, net $ 276,909 $ 201,495
Schedule of Accrued Liabilities	Accrued liabilities, as of September 30, 2020 and December 31, 2019 consists of the following (in thousands): September 30, December 31, 2020 2019 Clinical trials $ 44,554 $ 6,291 Development operations 24,187 2,567 Manufacturing 14,029 5,872 Other external goods and services 64,439 21,465 Compensation-related 48,788 27,428 Property and equipment 12,835 4,029 Accrued liabilities $ 208,832 $ 67,652
Changes in Balances of Receivables and Contract Liabilities	The following table presents changes in the balances of our receivables and contract liabilities related to our strategic collaboration agreements during the nine months ended September 30, 2020 (in thousands): December 31, 2019 Additions Deductions September 30, 2020 Contract Assets: Accounts receivable $ 1,972 $ 115,037 $ (85,354) $ 31,655 Contract Liabilities: Deferred revenue $ 199,528 $ 117,002 $ (50,320) $ 266,210 During the three and nine months ended September 30, 2020, we recognized the following revenue as a result of the change in the contract liability balances related to our collaboration agreements (in thousands): Revenue recognized in the period from: Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 Amounts included in contract liabilities at the beginning of the period (1) $ 13,263 $ 50,320 Performance obligations satisfied (or partially satisfied) in previous reporting periods (2) — 1,262 ______ (1) We first allocate revenue to the individual contract liability balance outstanding at the beginning of the period until the revenue exceeds that balance. If additional consideration is received on those contracts in subsequent periods, we assume all revenue recognized in the reporting period is first applied to the beginning contract liability. (2) Related to changes in estimated costs for our future performance obligations and estimated variable considerations. The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the services are expected to be performed or control of the supply is expected to be transferred (in thousands): September 30, 2020 December 31, 2019 Combined AZ Agreements $ 72,266 $ 73,669 Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 2016 VEGF Exercise $ — $ 172 $ 14,253 $ 146 The following table summarizes the balances of deferred revenue at period end, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the control of the supply is expected to be transferred for the periods presented (in thousands): September 30, 2020 December 31, 2019 2016 VEGF Exercise $ 29,335 $ 41,266 Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 PCV/SAV Agreement $ 7,792 $ 10,944 $ 23,561 $ 31,575 The following table summarizes the balances of deferred revenue, which is classified as current or non-current in the condensed consolidated balance sheets based on the period the services are expected to be performed or control of the supply is expected to be transferred for the periods presented (in thousands): September 30, 2020 December 31, 2019 PCV/SAV Agreement $ 60,548 $ 83,799 The following table summarizes the revenue recognized for the periods presented (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Vertex First Extended Research Term $ 5,449 $ — $ 7,645 $ — Vertex Agreement/2019 Amendment — 504 2,052 4,301 Total $ 5,449 $ 504 $ 9,697 $ 4,301 The following table summarizes the balances of deferred revenue, classified as current and non-current in the condensed consolidated balance sheets based on the term of the research period for the periods presented (in thousands): September 30, 2020 December 31, 2019 Vertex Agreement 1 $ 4,061 $ 793 ____________ (1) Balance as of December 31, 2019 represents deferred revenue related to the Vertex 2019 Amendment The following table summarizes the activities in deferred revenue for the nine months ended September 30, 2020 (in thousands): Deferred Revenue Balance at December 31, 2019 $ 202,305 Additions 1,293,370 Deductions (53,401) Balance at September 30, 2020 $ 1,442,274

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Assets And Liabilities, Lessee	Operating and financing lease right-of-use assets and lease liabilities as of September 30, 2020 and December 31, 2019 were as follows (in thousands): September 30, December 31, 2020 2019 Assets: Right-of-use assets, operating, net (1) (2) $ 91,684 $ 86,414 Right-of-use assets, financing, net (3) (4) 55,503 9,544 Total $ 147,187 $ 95,958 Liabilities: Current: Operating lease liabilities (5) $ 4,731 $ 3,584 Non-current: Operating lease liabilities, non-current 98,954 93,675 Financing lease liabilities, non-current 108,609 38,689 Total non-current lease liabilities 207,563 132,364 Total $ 212,294 $ 135,948 _______ (1) These assets are real estate related assets, which include land, office and laboratory spaces. (2) Net of accumulated depreciation. (3) These assets are real estate assets related to the MTC North and MTC South leases. (4) Included in property and equipment in the condensed consolidated balance sheets, net of accumulated depreciation. (5) Included in other current liabilities in the condensed consolidated balance sheets.
Lease, Cost	The components of the lease costs for the three and nine months ended September 30, 2020 and 2019 were as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Operating lease costs $ 3,962 $ 3,872 $ 12,977 $ 11,614 Financing lease costs: Amortization of right-of-use assets, financing leases 368 73 553 219 Interest expense for financing lease liabilities 2,843 1,644 6,385 4,901 Total financing lease costs $ 3,211 $ 1,717 $ 6,938 $ 5,120 Variable lease costs $ 1,120 $ 1,430 $ 3,618 $ 3,495 Supplemental cash flow information relating to our leases for the nine months ended September 30, 2020 and 2019 was as follows (in thousands): Nine Months Ended September 30, 2020 2019 Cash paid for amounts included in measurement of lease liabilities: Operating cash flows used in operating leases $ (11,314) $ (11,396) Operating cash flows used in financing leases (5,383) (4,161) Operating lease non-cash items: Right-of-use assets reduced through lease modifications and reassessments 6,755 16,242 Right-of-use assets obtained in exchange for operating lease liabilities 17,107 26,839 Finance lease non-cash items: Right-of-use assets obtained through lease modifications and reassessments 46,495 — Charges to financing lease obligation 39 741
Finance Lease Maturity	Future minimum lease payments under non-cancelable operating lease agreements at September 30, 2020, are as follows (in thousands): Fiscal Year Operating Leases (1) Financing Leases (1) 2020 (remainder of the year) $ 2,770 $ 1,858 2021 15,492 11,634 2022 15,913 11,848 2023 16,008 12,054 2024 16,168 12,279 Thereafter 110,167 440,552 Total minimum lease payments 176,518 490,225 Less amounts representing interest or imputed interest (72,833) (381,616) (2) Present value of lease liabilities $ 103,685 $ 108,609 ______ (1) Includes optional extensions in the MTC South lease term which represent a total of $10.3 million and $208.5 million un-discounted future lease payments in operating leases and financing leases, respectively. Includes optional extensions in the MTC North lease term which represent a total of $110.3 million un-discounted future lease payments in financing leases. (2) MTC South interest is based on an imputed interest rate of 17.2%. MTC North interest is based upon an incremental borrowing rate of 8.2%.
Operating Lease Maturity	Future minimum lease payments under non-cancelable operating lease agreements at September 30, 2020, are as follows (in thousands): Fiscal Year Operating Leases (1) Financing Leases (1) 2020 (remainder of the year) $ 2,770 $ 1,858 2021 15,492 11,634 2022 15,913 11,848 2023 16,008 12,054 2024 16,168 12,279 Thereafter 110,167 440,552 Total minimum lease payments 176,518 490,225 Less amounts representing interest or imputed interest (72,833) (381,616) (2) Present value of lease liabilities $ 103,685 $ 108,609 ______ (1) Includes optional extensions in the MTC South lease term which represent a total of $10.3 million and $208.5 million un-discounted future lease payments in operating leases and financing leases, respectively. Includes optional extensions in the MTC North lease term which represent a total of $110.3 million un-discounted future lease payments in financing leases. (2) MTC South interest is based on an imputed interest rate of 17.2%. MTC North interest is based upon an incremental borrowing rate of 8.2%.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Options Activity	The following table summarizes our option activity during the nine months ended September 30, 2020: Number of Options Weighted- Average Exercise Price per Share Weighted- Average Grant Date Fair Value per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (1) (in thousands) Outstanding at Outstanding at December 31, 2019 45,536,915 $ 13.82 $ 7.35 7.2 years $ 286,310 Granted 4,809,336 33.79 18.10 Exercised (10,613,303) 12.57 6.32 Canceled/forfeited (2,471,131) 17.78 10.39 Outstanding at September 30, 2020 37,261,817 16.49 8.82 7.0 years 2,022,154 Exercisable at September 30, 2020 18,348,695 10.96 5.61 5.6 years 1,097,117 Expected to vest at September 30, 2020 18,913,122 21.86 11.94 8.3 years 926,598 _______ (1) Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those options in the money as of September 30, 2020.
Restricted Common Stock Units Activity	The following table summarizes our restricted stock unit activity during the nine months ended September 30, 2020: Units Weighted-Average Outstanding, non-vested at December 31, 2019 1,177,249 $ 19.01 Issued 1,386,066 34.29 Vested (203,488) 20.46 Canceled/forfeited (187,650) 22.69 Outstanding, non-vested at September 30, 2020 2,172,177 28.37
Weighted-Average Assumptions Used to Estimate the Fair Value of Options Granted	The weighted-average assumptions used to estimate the fair value of options and ESPP granted for the nine months ended September 30, 2020 and 2019 are as follows: Weighted Average Nine Months Ended September 30, 2020 2019 Options: Risk-free interest rate 0.85 % 2.39 % Expected term 6.11 years 6.07 years Expected volatility 57.82 % 62 % Expected dividends — % — % Weighted average fair value per share $ 18.10 $ 11.71 ESPP: Risk-free interest rate 0.18 % 2.31 % Expected term 0.50 years 0.50 years Expected volatility 65 % 50 % Expected dividends — % — % Weighted average fair value per share $ 20.64 $ 19.85
Stock-Based Compensation Expense	The following table presents the components and classification of stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Options $ 18,924 $ 18,994 $ 57,365 $ 56,475 Restricted common stock units 3,404 1,291 8,098 3,628 ESPP 878 519 2,079 693 Total $ 23,206 $ 20,804 $ 67,542 $ 60,796 Research and development $ 14,022 $ 12,616 $ 40,761 $ 36,268 General and administrative 9,184 8,188 26,781 24,528 Total $ 23,206 $ 20,804 $ 67,542 $ 60,796

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Basic and Diluted Net Loss per Share Attributable to Common Stockholders	Basic and diluted net loss per share for the three and nine months ended September 30, 2020 and 2019 are calculated as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Numerator: Net loss $ (233,636) $ (123,215) $ (474,579) $ (390,731) Denominator: Weighted average common shares used in net loss per share, basic and diluted 394,682,744 330,769,341 376,174,283 329,592,322 Net loss per share, basic and diluted $ (0.59) $ (0.37) $ (1.26) $ (1.19)
Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents, presented based on amounts outstanding as of September 30, 2020 and 2019, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because their inclusion would have been anti-dilutive: September 30, 2020 2019 Stock options 37,261,817 48,962,655 Restricted common stock — 21,564 Restricted common stock units 2,172,177 1,659,187 39,433,994 50,643,406

Description of the Business - A

Description of the Business - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 1,971,033	$ 1,496,454

Summary of Basis of Presentat_4

Summary of Basis of Presentation and Recent Accounting Standards - Effect of Adoption of ASC 606 on Condensed Consolidated Financial Statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Research and development	$ 344,486	$ 119,637	[1]	$ 611,479	$ 378,355	[1]
General and administrative	48,541	28,173	[1]	109,277	83,913	[1]
Total operating expenses	393,027	147,810	[1]	720,756	462,268	[1]
Loss from operations	(235,117)	(130,764)	[1]	(488,106)	(416,114)	[1]
Other expense, net	(3,226)	(1,881)	[1]	(5,910)	(5,689)	[1]
Loss before income taxes	(232,772)	(123,393)	[1]	(473,501)	(391,257)	[1]
Net loss	$ (233,636)	$ (123,215)	[2]	$ (474,579)	$ (390,731)	[2]
Net loss per share, basic and diluted (usd per share)	$ (0.59)	$ (0.37)	[1]	$ (1.26)	$ (1.19)	[1]
Depreciation and amortization	$ 8,500	$ 7,300		$ 23,545	$ 22,046	[3]
Prepaid expenses and other assets				(67,994)	1,813	[3]
Right-of-use assets, operating leases				(13,117)	(7,970)	[3]
Operating lease liabilities				14,417	13,475	[3]
Other liabilities				6,684	(153)	[3]
Net cash used in operating activities				762,682	(359,946)	[3]
Charges to financing lease liabilities				39	741	[3]
Net cash provided by financing activities				$ 1,989,084	20,282	[3]
Previously reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Research and development		119,715			378,786
General and administrative		28,188			83,994
Total operating expenses		147,903			462,780
Loss from operations		(130,857)			(416,626)
Other expense, net		(1,767)			(5,351)
Loss before income taxes		(123,372)			(391,431)
Net loss		$ (123,194)			$ (390,905)
Net loss per share, basic and diluted (usd per share)		$ (0.37)			$ (1.19)
Depreciation and amortization					$ 22,082
Prepaid expenses and other assets					(1,407)
Deferred lease obligation					3,844
Other liabilities					1,617
Net cash used in operating activities					(363,195)
Reimbursement of assets under lease financing obligation					3,678
Payments on financing lease obligation					312
Net cash provided by financing activities					23,531
Adjustments | Accounting standards update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Research and development		$ (78)			(431)
General and administrative		(15)			(81)
Total operating expenses		(93)			(512)
Loss from operations		93			512
Other expense, net		(114)			(338)
Loss before income taxes		(21)			174
Net loss		$ (21)			174
Depreciation and amortization					(36)
Prepaid expenses and other assets					3,220
Right-of-use assets, operating leases					(7,970)
Deferred lease obligation					(3,844)
Operating lease liabilities					13,475
Other liabilities					(1,770)
Net cash used in operating activities					3,249
Reimbursement of assets under lease financing obligation					(3,678)
Charges to financing lease liabilities					741
Payments on financing lease obligation					(312)
Net cash provided by financing activities					$ (3,249)
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.
[3]	Restated to conform to ASC 842. See accompanying Note 2.

Summary of Basis of Presentat_5

Summary of Basis of Presentation and Recent Accounting Standards - Components of Accumulated Other Comprehensive (loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	$ 2,946,885		$ 1,174,810	$ 1,334,960	[1]	$ 1,174,810	$ 1,530,241	[2]
Other comprehensive income	(3,472)			89	[3]	2,980	4,150	[3]
Balance at end of period	2,759,798	$ 2,946,885		1,248,192	[2]	2,759,798	1,248,192	[2]
Accumulated Other Comprehensive Income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	8,256	(6,127)	1,804	2,741		1,804	(1,320)
Other comprehensive income	(3,472)			89		2,980	4,150
Balance at end of period	4,784	8,256	(6,127)	$ 2,830		$ 4,784	$ 2,830
Unrealized (Loss) Gain on Available-for-Sale Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income	$ (3,472)	$ 14,383	$ (7,931)
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.
[3]	Restated to conform to ASC 842. See accompanying Note 2.

Summary of Basis of Presentat_6

Summary of Basis of Presentation and Recent Accounting Standards - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019		Dec. 31, 2018	[1]
Accounting Policies [Abstract]
Cash and cash equivalents	$ 1,505,581	$ 235,876	$ 173,711
Restricted cash	1,032	1,032	1,032
Restricted cash, non-current	11,053	10,791	10,791
Total cash, cash equivalents and restricted cash shown in the condensed consolidated statements of cash flows	$ 1,517,666	$ 247,699	$ 185,534	[1]	$ 670,491
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Grant Revenue (Details)

Grant Revenue (Details) $ in Thousands	1 Months Ended			3 Months Ended			9 Months Ended
	Sep. 30, 2020USD ($)	Apr. 30, 2020USD ($)	Sep. 30, 2016USD ($)option	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)		Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)		Jul. 26, 2020USD ($)	Dec. 31, 2019USD ($)
Disaggregation of Revenue [Line Items]
Total grant revenue				$ 157,910	$ 17,046	[1]	$ 232,650	$ 46,154	[1]
Contract with customer, liability	$ 1,442,274			1,442,274			1,442,274				$ 202,305
Grant revenue
Disaggregation of Revenue [Line Items]
Total grant revenue				145,694	3,708	[1]	187,535	8,671	[1]
Contract with customer, liability	5,670			5,670			5,670				$ 1,496
DARPA
Disaggregation of Revenue [Line Items]
Award amount	56,400
DARPA | Contract options
Disaggregation of Revenue [Line Items]
Amount committed for funding	5,000			5,000			5,000
Available funding	51,400			51,400			51,400
BARDA
Disaggregation of Revenue [Line Items]
Award amount		$ 483,300	$ 125,800
Amount committed for funding	781,700			781,700			781,700
Additional commitment										$ 471,600
Number of contract options | option			3
Number of contract options exercised | option			4
BARDA | Maximum
Disaggregation of Revenue [Line Items]
Award amount							954,900
BARDA | Minimum
Disaggregation of Revenue [Line Items]
Award amount							483,300
BARDA | Grant revenue
Disaggregation of Revenue [Line Items]
Total grant revenue				143,318	1,135		183,134	4,500
BARDA | Contract options
Disaggregation of Revenue [Line Items]
Amount committed for funding	71,900			71,900			71,900
Available funding	8,400			8,400			8,400
The Bill & Melinda Gates Foundation | Initial project
Disaggregation of Revenue [Line Items]
Available funding	12,600			12,600			12,600
Contract with customer, liability	$ 80,000			80,000			80,000
Other grant revenue | Grant revenue
Disaggregation of Revenue [Line Items]
Total grant revenue				$ 2,376	$ 2,573		$ 4,401	$ 4,171
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Collaboration Revenue - Summary

Collaboration Revenue - Summary of Total Consolidated Net Revenues from Strategic Collaborators (Details) - Collaboration Revenue by Strategic Collaborator: - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total collaboration revenue	$ 12,216	$ 13,338	$ 45,115	$ 37,483
AstraZeneca
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total collaboration revenue	48	3,724	17,202	4,726
Merck
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total collaboration revenue	6,718	9,110	18,060	28,456
Vertex
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total collaboration revenue	5,450	504	9,698	4,301
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total collaboration revenue	$ 0	$ 0	$ 155	$ 0

Collaboration Revenue - Changes

Collaboration Revenue - Changes in Balances of Receivables and Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Contract Liabilities:
Beginning balance		$ 202,305
Additions		1,293,370
Deductions		(53,401)
Ending balance	$ 1,442,274	1,442,274
Remaining performance obligations	104,945	104,945
Collaboration Revenue by Strategic Collaborator:
Contract Assets:
Beginning balance		1,972
Additions		115,037
Deductions		(85,354)
Ending balance	31,655	31,655
Contract Liabilities:
Beginning balance		199,528
Additions		117,002
Deductions		(50,320)
Ending balance	266,210	266,210
Amounts included in contract liabilities at the beginning of the period	13,263	50,320
Performance obligations satisfied (or partially satisfied) in previous reporting periods	0	1,262
Remaining performance obligations	$ 366,700	$ 366,700

Collaboration Revenue - Remaini

Collaboration Revenue - Remaining Performance Obligation (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Collaboration Revenue by Strategic Collaborator:
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	366,700
Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	399,089	$ 401,782
Combined 2018 AZ agreements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 95,200
Performance period	8 years 3 months
Combined 2018 AZ agreements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 9,700
Performance period
VEGF exercise 2016
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 60,312	57,871
VEGF exercise 2016 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 41,877
Performance period	4 years 3 months
PCVSAV agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 213,360	$ 213,050
PCVSAV agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 60,548
Performance period	3 years 3 months
2020 Vertex agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance period	1 year

Collaboration Revenue - AstraZe

Collaboration Revenue - AstraZeneca - Strategic Alliances in Cardiovascular and Oncology (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019		Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price				$ 5,500,000
Remaining performance obligations	$ 104,945,000			104,945,000
Revenue	157,910,000	$ 17,046,000	[1]	232,650,000	$ 46,154,000	[1]
Collaboration revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue	12,216,000	13,338,000	[1]	45,115,000	37,483,000	[1]
Combined 2018 AZ agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price				2,700,000
Remaining performance obligations	399,089,000			399,089,000			$ 401,782,000
Combined 2018 AZ agreements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	9,700,000			9,700,000
Combined 2018 AZ agreements | Collaboration revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price	(1,400,000)			(1,400,000)
VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price	(400,000)			(400,000)
Remaining performance obligations	60,312,000			60,312,000			57,871,000
VEGF exercise 2016 | Estimated reimbursement for clinical supply
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price				(2,400,000)
Remaining performance obligations	18,062,000			18,062,000			$ 15,621,000
VEGF exercise 2016 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	41,877,000			41,877,000
2017 Strategic alliance with AstraZeneca – Relaxin | Collaboration revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue	$ 0	$ 0		$ 0	$ 0
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Collaboration Revenue - Composi

Collaboration Revenue - Composition of the Total Transaction Price (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 104,945
Combined 2018 AZ agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	399,089	$ 401,782
Combined 2018 AZ agreements | Upfront payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	240,000	240,000
Combined 2018 AZ agreements | Sublicense reimbursement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	1,000	1,000
Combined 2018 AZ agreements | Milestone payment | Toxicity milestone payment
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	60,000	60,000
Combined 2018 AZ agreements | Milestone payment | Competition milestone payment
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	60,000	60,000
Combined 2018 AZ agreements | Estimated reimbursement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 38,089	$ 40,782

Collaboration Revenue - Total T

Collaboration Revenue - Total Transaction Price to the Identified Performance Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	399,089	$ 401,782
Combined 2018 AZ agreements | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	9,700
Combined 2018 AZ Agreement performance obligation | Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	293,223
Preclinical development service - IL-12 | Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	8,133
Preclinical development service - oncology development target | Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	8,133
Development and commercialization license and manufacturing obligation | Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	88,009
Material right to receive development and commercialization rights | Combined 2018 AZ agreements
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 1,591

Collaboration Revenue - Revenue

Collaboration Revenue - Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Increase to the transaction price			$ (5,500)
Combined 2018 AZ agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Increase to the transaction price			(2,700)
Collaboration revenue | Combined 2018 AZ agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	$ 49	$ 3,552	2,950	$ 4,580
Increase to the transaction price	$ 1,400		$ 1,400

Collaboration Revenue - Deferre

Collaboration Revenue - Deferred Revenue which is Classified as Current or Non-Current in the Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 1,442,274	$ 202,305
Combined 2018 AZ agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 72,266	$ 73,669

Collaboration Revenue - VEGF To

Collaboration Revenue - VEGF Total Transaction Price (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 104,945
VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	60,312	$ 57,871
Option exercise fee | VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	10,000	10,000
Milestone payment | VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	30,000	30,000
Sublicense reimbursement | VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	2,250	2,250
Estimated reimbursement for clinical supply | VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 18,062	$ 15,621

Collaboration Revenue - Total_2

Collaboration Revenue - Total Transaction Price Allocated to the Single Identified Performance Obligation (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
VEGF exercise 2016
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	60,312	$ 57,871
VEGF exercise 2016 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 41,877

Collaboration Revenue - VEGF Re

Collaboration Revenue - VEGF Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	$ 0	$ 172	$ 14,253	$ 146

Collaboration Revenue - VEGF De

Collaboration Revenue - VEGF Deferred Revenue which is Classified as Current or Non-Current in the Balance Sheets (Details) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 1,442,274	$ 202,305
VEGF exercise 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 29,335	$ 41,266

Collaboration Revenue - Merck _

Collaboration Revenue - Merck – Strategic Alliances in Infectious Diseases and Cancer Vaccines (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended		53 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	May 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price			$ 5,500
Merck agreement 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue (contra-revenue)						$ 65,000
Initial research period							4 years
Agreement period							3 years
Decrease to the transaction price			(10,778)		$ (5,265)
Merck agreement 2015 | Upfront payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue (contra-revenue)						60,000
Merck agreement 2015 | Upfront payment, research and development
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue (contra-revenue)						$ 5,000
Merck agreement 2015 | Collaboration revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue (contra-revenue)	$ 0	$ (188)	12	$ 666
PCVSAV agreement | Clinical supply reimbursement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Decrease to the transaction price			(300)
PCVSAV agreement | Collaboration revenue
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue (contra-revenue)	7,792	$ 10,944	23,561	$ 31,575
Decrease to the transaction price	$ (3,500)		$ (3,500)

Collaboration Revenue - MERCK C

Collaboration Revenue - MERCK Composition of the Total Transaction Price (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 104,945
Decrease to the transaction price	5,500
Merck agreement 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	54,222	$ 59,735
Decrease to the transaction price	(10,778)	(5,265)
Merck agreement 2015 | Upfront payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	60,000	60,000
Merck agreement 2015 | Upfront payment, research and development
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 5,000	$ 5,000

Collaboration Revenue - MERCK T

Collaboration Revenue - MERCK Total Transaction Price to the Identified Performance Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Merck agreement 2015
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	54,222	$ 59,735
Merck agreement 2015 | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 0

Collaboration Revenue - MERCK R

Collaboration Revenue - MERCK Revenue and Contra-Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2018
Merck agreement 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue					$ 65,000
Collaboration revenue | Contra-revenue under the May 2019 Amendment
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	$ (1,074)	$ (1,657)	$ (5,513)	$ (3,796)
Collaboration revenue | Merck agreement 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	0	(188)	12	666
Collaboration revenue | Separate agreements with Merck
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	$ (1,074)	$ (1,845)	$ (5,501)	$ (3,130)

Collaboration Revenue - PCV_SAV

Collaboration Revenue - PCV/SAV Composition of the Total Transaction Price (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
PCVSAV agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	213,360	$ 213,050
PCVSAV agreement | Upfront payments
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	200,000	200,000
PCVSAV agreement | Upfront payment, premium associated with contemporaneous sale Of preferred stock
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	13,050	13,050
PCVSAV agreement | Clinical supply reimbursement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 310	$ 0

Collaboration Revenue - PCV_S_2

Collaboration Revenue - PCV/SAV Total Transaction Price to the Identified Performance Obligations (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
PCVSAV agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	213,360	$ 213,050
PCVSAV agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	60,548
PCV performance obligation | PCVSAV agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	206,356
KRAS performance obligation | PCVSAV agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 7,004

Collaboration Revenue - PCV_S_3

Collaboration Revenue - PCV/SAV Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaboration revenue | PCVSAV agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue	$ 7,792	$ 10,944	$ 23,561	$ 31,575

Collaboration Revenue - PCV_S_4

Collaboration Revenue - PCV/SAV Balances of Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 1,442,274	$ 202,305
PCVSAV agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 60,548	$ 83,799

Collaboration Revenue - Vertex

Collaboration Revenue - Vertex – 2016 Strategic Alliance in Cystic Fibrosis (Details) $ in Thousands	1 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Jul. 31, 2019extension_period	Sep. 30, 2020USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 104,945		$ 104,945
Increase to the transaction price			(5,500)
Upfront cash payments			1,293,370
2020 Vertex agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payment received, research extension period		18 months
Number of extension periods | extension_period		2
Research extension period		1 year
Total collaboration revenue			4,500
Increase to the transaction price			15,200
2020 Vertex agreement | Upfront payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	2,000		2,000
2020 Vertex agreement | Research and development
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 2,500		2,500
Chiesi agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research extension period	4 years
Remaining performance obligations	$ 42,656		42,656
Initial research period	4 years
Chiesi agreement | Upfront payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Total collaboration revenue			25,000
Remaining performance obligations	$ 25,000		25,000
Chiesi agreement | Research and development
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Remaining performance obligations	$ 17,656		$ 17,656

Collaboration Revenue - VERTE_2

Collaboration Revenue - VERTEX Composition of the Total Transaction Price (Details) $ in Thousands	Sep. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Vertex First Extended Research Term
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	50,410
Upfront payments | Vertex First Extended Research Term
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	4,000
Research and development | Vertex First Extended Research Term
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 46,410

Collaboration Revenue - VERTE_3

Collaboration Revenue - VERTEX Total Transaction Price to the Identified Performance Obligations (Details) $ in Thousands	Sep. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Vertex First Extended Research Term
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	50,410
Vertex First Extended Research Term | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 42,766

Collaboration Revenue - VERTE_4

Collaboration Revenue - VERTEX Revenue Recognized (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Vertex First Extended Research Term
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognized	$ 5,449	$ 0	$ 7,645	$ 0
Vertex Agreement/2019 Amendment
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognized	0	504	2,052	4,301
Vertex agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognized	$ 5,449	$ 504	$ 9,697	$ 4,301

Collaboration Revenue - VERTE_5

Collaboration Revenue - VERTEX Balances of Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 1,442,274	$ 202,305
Vertex Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract with customer, liability	$ 4,061	$ 793

Collaboration Revenue - Verte_6

Collaboration Revenue - Vertex 2020 Strategic Alliance in Cystic Fibrosis (Details) - USD ($) $ in Thousands	1 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Remaining performance obligations	$ 104,945
Deferred revenue	$ 1,234,506	$ 63,310
Vertex 2020 Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Initial research period	3 years
Total collaboration revenue	$ 75,000
Written notice period	90 days
Termination period	180 days
Remaining performance obligations	$ 75,000
Deferred revenue	75,000
Vertex 2020 Agreement | Upfront payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total collaboration revenue	75,000
Vertex 2020 Agreement | Certain development, regulatory and commercial milestone events
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized	$ 380,000

Collaboration Revenue - Chiesi

Collaboration Revenue - Chiesi Agreement Composition of the Total Transaction Price (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945	$ 104,945
Deferred revenue, non-current	$ 207,768	$ 207,768	$ 138,995
Chiesi agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Initial research period	4 years
Research extension period elected		1 year
Research extension period	4 years
Remaining performance obligations	$ 42,656	$ 42,656
Revenue recognized		25,000
Deferred revenue, non-current	25,000	25,000
Chiesi agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	17,700	17,700
Chiesi agreement | Upfront payments
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total collaboration revenue		25,000
Remaining performance obligations	25,000	$ 25,000
Chiesi agreement | Certain development, regulatory and commercial milestone events
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue recognized	$ 405,000

Collaboration Revenue - Chies_2

Collaboration Revenue - Chiesi Agreement Total Transaction Price to the Identified Performance Obligations (Details) $ in Thousands	Sep. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 104,945
Chiesi agreement
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	42,656
Chiesi agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	17,700
Chiesi agreement | Upfront payments
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	25,000
Chiesi agreement | Research and development
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	17,656
Chiesi agreement | Material right for the first product development and commercialization license
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	17,500
Chiesi agreement | Material right for the second product development and commercialization license
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations	$ 7,500

Contracts With Customer (Detail

Contracts With Customer (Details) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 31, 2020USD ($)dose	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)dose	Dec. 31, 2019USD ($)
Disaggregation of Revenue [Line Items]
Contract with customer, liability		$ 1,442,274	$ 1,442,274	$ 202,305
Additional doses of vaccine | dose	100,000,000
Deferred revenue		1,234,506	$ 1,234,506	$ 63,310
Supply agreement with US government
Disaggregation of Revenue [Line Items]
Number of doses of vaccine candidate | dose	100,000,000		100,000,000
Contract with customer, liability	$ 1,650,000
Additional doses of vaccine | dose	400,000,000
Supply agreement with US government | US Government | Government contract
Disaggregation of Revenue [Line Items]
Contract with customer, liability	$ 1,525,000	1,225,000	$ 1,225,000
Incentive payments	300,000	300,000	300,000
Total collaboration revenue	$ 601,400		601,400
Percentage of fixed price received from upfront payment	50.00%
Percentage of fixed price remaining	50.00%
Deferred revenue		601,400	601,400
International supply agreements
Disaggregation of Revenue [Line Items]
Deferred revenue		569,000	$ 569,000
Proceeds from Customers		$ 569,000

Financial Instruments - Summary

Financial Instruments - Summary of Cash and Available-for-Sale Securities by Significant Investment Category (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,456,725
Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,962,304	$ 1,259,980
Unrealized Gains	6,476	3,047
Unrealized Losses	(509)	(40)
Estimated Fair Value	3,968,271	1,262,987
Level 2 | Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,505,581	235,876
Level 2 | Current marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,770,721	867,124
Level 2 | Noncurrent marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	691,969	159,987
Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,505,579	225,874
Unrealized Gains	2	0
Unrealized Losses	0	0
Estimated Fair Value	1,505,581	225,874
Cash and cash equivalents | Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,505,581	225,874
Cash and cash equivalents | Current marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Cash and cash equivalents | Noncurrent marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Certificates of deposit | Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	161,097	82,028
Unrealized Gains	46	79
Unrealized Losses	(1)	(6)
Estimated Fair Value	161,142	82,101
Certificates of deposit | Level 2 | Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	10,002
Certificates of deposit | Level 2 | Current marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	152,649	69,197
Certificates of deposit | Level 2 | Noncurrent marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	8,493	2,902
U.S. treasury securities | Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	130,495	117,891
Unrealized Gains	385	260
Unrealized Losses	(1)	(2)
Estimated Fair Value	130,879	118,149
U.S. treasury securities | Level 2 | Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
U.S. treasury securities | Level 2 | Current marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	81,607	110,186
U.S. treasury securities | Level 2 | Noncurrent marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	49,272	7,963
Debt securities of U.S. government agencies and corporate entities | Level 2
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,165,133	834,187
Unrealized Gains	6,043	2,708
Unrealized Losses	(507)	(32)
Estimated Fair Value	2,170,669	836,863
Debt securities of U.S. government agencies and corporate entities | Level 2 | Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	0	0
Debt securities of U.S. government agencies and corporate entities | Level 2 | Current marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	1,536,465	687,741
Debt securities of U.S. government agencies and corporate entities | Level 2 | Noncurrent marketable securities
Debt Securities, Available-for-sale [Line Items]
Estimated Fair Value	$ 634,204	$ 149,122

Financial Instruments - Amortiz

Financial Instruments - Amortized Cost and Estimated Fair Value of Marketable Securities, by Contractual Maturity (Details) $ in Thousands	Sep. 30, 2020USD ($)
Amortized Cost
Due in one year or less	$ 1,766,834
Due after one year through five years	689,891
Amortized Cost	2,456,725
Estimated Fair Value
Due in one year or less	1,770,721
Due after one year through five years	691,969
Total	$ 2,462,690

Financial Instruments - Unreali

Financial Instruments - Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2020USD ($)option	Dec. 31, 2019USD ($)option
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	$ (509)	$ (40)
Estimated Fair Value, Less than 12 months	759,483	85,161
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(509)	(40)
Estimated Fair Value, Total	$ 759,483	$ 85,161
Number of AFS securities in loss positions | option	0	19
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	$ (1)	$ (6)
Estimated Fair Value, Less than 12 months	14,893	12,822
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(1)	(6)
Estimated Fair Value, Total	14,893	12,822
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	(1)	(2)
Estimated Fair Value, Less than 12 months	15,341	9,979
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(1)	(2)
Estimated Fair Value, Total	15,341	9,979
Debt securities of U.S. government agencies and corporate entities
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Losses, Less than 12 months	(507)	(32)
Estimated Fair Value, Less than 12 months	729,249	62,360
Gross Unrealized Losses, 12 months or more	0	0
Estimated Fair Value, 12 months or more	0	0
Gross Unrealized Losses, Total	(507)	(32)
Estimated Fair Value, Total	$ 729,249	$ 62,360

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Down payments to manufacturing vendors	$ 23,990	$ 0
Other prepaid expenses	62,434	8,475
Tenant incentives receivables	12,941	4,093
Interest receivable on marketable securities	10,011	6,835
Prepaid expenses and other current assets	$ 109,376	$ 19,403

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	[1]	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 388,899		$ 388,899			$ 296,079
Less: Accumulated depreciation	(111,990)		(111,990)			(94,584)
Property and equipment, net	276,909		276,909			201,495
Depreciation and amortization	8,500	$ 7,300	23,545	$ 22,046
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	113,326		113,326			108,257
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	163,793		163,793			152,426
Furniture, fixtures and other
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,613		4,613			3,316
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,583		12,583			11,985
Internally developed software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,020		7,020			7,020
Right-of-use asset, financing
Property, Plant and Equipment [Line Items]
Property and equipment, gross	56,348		56,348			9,853
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 31,216		$ 31,216			$ 3,222
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Clinical trials	$ 44,554	$ 6,291
Development operations	24,187	2,567
Manufacturing	14,029	5,872
Other external goods and services	64,439	21,465
Compensation-related	48,788	27,428
Property and equipment	12,835	4,029
Accrued liabilities	$ 208,832	$ 67,652

Balance Sheet Components - Defe

Balance Sheet Components - Deferred Revenue (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Contract Liabilities:
Beginning balance	$ 202,305
Additions	1,293,370
Deductions	(53,401)
Ending balance	1,442,274
Disaggregation of Revenue [Line Items]
Contract with customer, liability	1,442,274
Vaccine supply
Contract Liabilities:
Ending balance	1,170,000
Disaggregation of Revenue [Line Items]
Contract with customer, liability	$ 1,170,000

Leases (Details)

Leases (Details) ft² in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)ft²extension_periodcampus	Jun. 01, 2020ft²	May 31, 2020USD ($)	Sep. 30, 2019	Aug. 31, 2019ft²	Feb. 28, 2019ft²	Aug. 31, 2016ft²extension_period
Lessee, Lease, Description [Line Items]
Number of campuses | campus	2
Amounts representing interest or imputed interest, operating lease | $	$ 72,833
Interest or imputed interest | $	$ 381,616
Cambridge leases
Lessee, Lease, Description [Line Items]
Area of office space (in sqft) | ft²	175
Cambridge leases | 200 technology square
Lessee, Lease, Description [Line Items]
Area of office space (in sqft) | ft²					50
Cambridge leases | 500 technology square
Lessee, Lease, Description [Line Items]
Area of office space (in sqft) | ft²					60
Extension term	2 years
Norwood leases | MTC South
Lessee, Lease, Description [Line Items]
Area of office space (in sqft) | ft²							200
Number of extension periods | extension_period							2
Extension term							10 years
Amounts representing interest or imputed interest, operating lease | $	$ 10,300
Interest or imputed interest | $	$ 208,500
Imputed interest rate	17.20%
Norwood leases | MTC North
Lessee, Lease, Description [Line Items]
Area of office space (in sqft) | ft²						200
Allowance for tenant improvements | $			$ 22,200
Number of extension periods | extension_period	4
Extension term				5 years
Percentage subleased	64.00%	12.00%
Additional space (in sqft) | ft²		28
Interest or imputed interest | $	$ 110,300
Incremental borrowing rate	8.20%

Leases - Balance Sheet Informat

Leases - Balance Sheet Information (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Right-of-use assets, operating, net	$ 91,684	$ 86,414
Right-of-use assets, financing, net	55,503	9,544
Total	147,187	95,958
Operating lease liabilities, current	4,731	3,584
Operating lease liabilities, non-current	98,954	93,675
Financing lease liabilities, non-current	108,609	38,689
Total non-current lease liabilities	207,563	132,364
Total	$ 212,294	$ 135,948
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization

Leases - Lease Costs (Details)

Leases - Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Leases [Abstract]
Operating lease costs	$ 3,962	$ 3,872	$ 12,977	$ 11,614
Amortization of right-of-use assets, financing leases	368	73	553	219
Interest expense for financing lease liabilities	2,843	1,644	6,385	4,901
Total financing lease costs	3,211	1,717	6,938	5,120
Variable lease costs	$ 1,120	$ 1,430	3,618	3,495
Operating cash flows used in operating leases			(11,314)	(11,396)
Operating cash flows used in financing leases			(5,383)	(4,161)
Right-of-use assets reduced through lease modifications and reassessments			6,755	16,242
Right-of-use assets obtained in exchange for operating lease liabilities			17,107	26,839
Right-of-use assets obtained through lease modifications and reassessments			46,495	0
Charges to financing lease obligation			$ 39	$ 741

Leases - Minimum Lease Payments

Leases - Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2020USD ($)
Operating Leases
2020	$ 2,770
2021	15,492
2022	15,913
2023	16,008
2024	16,168
Thereafter	110,167
Total minimum lease payments	176,518
Less amounts representing interest or imputed interest	(72,833)
Present value of lease liabilities	103,685
Financing Leases
2020	1,858
2021	11,634
2022	11,848
2023	12,054
2024	12,279
Thereafter	440,552
Total minimum lease payments	490,225
Less amounts representing interest or imputed interest	(381,616)
Present value of lease liabilities	$ 108,609

Commitments and Contingencies -

Commitments and Contingencies - Strategic Collaborations (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
PCV agreement | PCV products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Budgeted amount	$ 243	$ 243

Commitments and Contingencies_2

Commitments and Contingencies - Purchase Commitments and Purchase Orders (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Supply and manufacturing agreements
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase commitments	$ 613.9
Purchase commitment
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase commitments	16.9
Clinical operations and support commitment
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase commitments	$ 747.9	$ 105.9

Shareholders' Equity (Details)

Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	May 21, 2020	Feb. 14, 2020	Dec. 11, 2018	Sep. 30, 2020	Sep. 30, 2019	[1]	Dec. 31, 2019	May 07, 2018	Feb. 28, 2018
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares)			1,600,000,000	1,600,000,000			1,600,000,000		775,000,000
Redeemable convertible preferred stock, shares authorized (in shares)								509,352,795
Common stock, par value (usd per share)			$ 0.0001	$ 0.0001			$ 0.0001
Preferred stock, shares authorized (in shares)			162,000,000	162,000,000			162,000,000
Preferred stock par value (usd per share)			$ 0.0001	$ 0.0001			$ 0.0001
Offering expenses				$ 2,086
Proceeds from public offerings of common stock, net of issuance costs				$ 1,852,759	$ 0
IPO
Subsidiary, Sale of Stock [Line Items]
Shares of common stock issued (in shares)			26,275,993
Price per share (usd per share)			$ 23
Aggregate net proceeds from the offering			$ 563,000
Underwriting discounts			33,200
Offering expenses			$ 8,100
IPO | Common Stock
Subsidiary, Sale of Stock [Line Items]
Preferred stock converted into common stock (in shares)			236,012,913
Public equity offering
Subsidiary, Sale of Stock [Line Items]
Shares of common stock issued (in shares)	17,600,000	26,315,790
Price per share (usd per share)	$ 76	$ 19
Proceeds from public offerings of common stock, net of issuance costs	$ 1,300,000	$ 477,700
Underwriting option
Subsidiary, Sale of Stock [Line Items]
Shares of common stock issued (in shares)		3,947,368
Proceeds from public offerings of common stock, net of issuance costs		$ 71,800
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details)	Dec. 05, 2018USD ($)shares	Nov. 30, 2018shares	Nov. 30, 2018shares	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2019USD ($)	[1]	Sep. 30, 2020USD ($)installment$ / sharesshares	Sep. 30, 2019USD ($)	[2]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares authorized for issuance (in shares)				67,500,000			67,500,000
Stock options exercised (in shares)							10,613,303
Total intrinsic value of options exercised | $							$ 434,900,000
Exercise of options to purchase common stock, net | $				$ 26,815,000	$ 15,554,000		133,369,000	$ 19,541,000
Total unrecognized compensation cost related to non-vested stock-based compensation | $				$ 236,900,000			$ 236,900,000
Weighted-average period of cost expected to be recognized							2 years 11 months 23 days
Service-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							4 years
Service-based awards | Tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period							12 months
Vesting percentage							25.00%
Service-based awards | Tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of installments | installment							12
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares authorized for issuance (in shares)				39,400,000			39,400,000
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares sold under the ESPP (in shares)							173,738
Average share price (usd per share) | $ / shares				$ 16.80			$ 16.80
Share available for future issuance (in shares)				3,700,000			3,700,000
Stock option and incentive plan 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares authorized for issuance (in shares)		13,000,000	13,000,000
Annual percentage of additional shares authorized		4.00%
Shares available for future grant (in shares)				28,100,000			28,100,000
Stock option and grant plan 2016 | Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period							10 years
Employee stock | ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate number of shares authorized for issuance (in shares)	810,000
Additional shares authorized (in shares)			3,240,000
Offering period	6 months
Purchase price at which shares are sold, percent	85.00%
Minimum percentage of compensation through payroll deductions	1.00%
Maximum percentage of compensation through payroll deductions	50.00%
Maximum shares to be purchased during purchase period (in shares)	3,000
Maximum value of shares to be purchased during purchase period | $	$ 25,000
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.

Stock-Based Compensation - Opti

Stock-Based Compensation - Options Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares
Number of Options
Outstanding at beginning of period (in shares) | shares	45,536,915
Granted (in shares) | shares	4,809,336
Exercised (in shares) | shares	(10,613,303)
Cancelled/forfeited (in shares) | shares	(2,471,131)
Outstanding at end of period (in shares) | shares	37,261,817	45,536,915
Weighted- Average Exercise Price per Share
Outstanding at beginning of period (usd per share)	$ 13.82
Granted (usd per share)	33.79
Exercised (usd per share)	12.57
Cancelled/forfeited (usd per share)	17.78
Outstanding at end of period (usd per share)	16.49	$ 13.82
Weighted- Average Grant Date Fair Value per Share
Outstanding at beginning of period (usd per share)	7.35
Granted (usd per share)	18.10
Exercised (usd per share)	6.32
Cancelled/forfeited (usd per share)	10.39
Outstanding at end of period (usd per share)	$ 8.82	$ 7.35
Outstanding and Exercisable
Number of Options, Exercisable (in shares) | shares	18,348,695
Weighted- Average Exercise Price per Share, Exercisable (usd per share)	$ 10.96
Weighted- Average Grant Date Fair Value per Share, Exercisable (usd per share)	$ 5.61
Weighted- Average Remaining Contractual Term, Outstanding	7 years	7 years 2 months 12 days
Weighted- Average Remaining Contractual Term, Exercisable	5 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding | $	$ 2,022,154	$ 286,310
Aggregate Intrinsic Value, Exercisable | $	$ 1,097,117
Expected to vest
Number of Options (in shares) | shares	18,913,122
Weighted- Average Exercise Price per Share (usd per share)	$ 21.86
Weighted- Average Grant Date Fair Value per Share (usd per share)	$ 11.94
Weighted- Average Remaining Contractual Term	8 years 3 months 18 days
Aggregate Intrinsic Value | $	$ 926,598

Stock-Based Compensation - Rest

Stock-Based Compensation - Restricted Common Stock and Common Stock Units Activity (Details) - Restricted common stock units	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Units
Outstanding, non-vested at beginning of period (in shares) | shares	1,177,249
Issued (in shares) | shares	1,386,066
Vested (in shares) | shares	(203,488)
Canceled, forfeited (in shares) | shares	(187,650)
Outstanding, non-vested at end of period (in shares) | shares	2,172,177
Weighted-Average Fair Value per Unit
Outstanding, non-vested at beginning of period (usd per share) | $ / shares	$ 19.01
Issued (usd per share) | $ / shares	34.29
Vested (usd per share) | $ / shares	20.46
Canceled, forfeited (usd per share) | $ / shares	22.69
Outstanding, non-vested at end of period (usd per share) | $ / shares	$ 28.37

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate the Fair Value of Options Granted (Details) - $ / shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.85%	2.39%
Expected term	6 years 1 month 9 days	6 years 25 days
Expected volatility	57.82%	62.00%
Expected dividends	0.00%	0.00%
Options | Weighted average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share	$ 18.10	$ 11.71
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.18%	2.31%
Expected term	6 months	6 months
Expected volatility	65.00%	50.00%
Expected dividends	0.00%	0.00%
Weighted average fair value per share	$ 16.80
ESPP | Weighted average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share	$ 20.64	$ 19.85

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 23,206	$ 20,804	$ 67,542	$ 60,796
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	14,022	12,616	40,761	36,268
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	9,184	8,188	26,781	24,528
Options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	18,924	18,994	57,365	56,475
Restricted common stock units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	3,404	1,291	8,098	3,628
ESPP
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock-based compensation expense	$ 878	$ 519	$ 2,079	$ 693

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Provision for (benefit from) income taxes	$ 864	$ (178)	[1]	$ 1,078	$ (526)	[1]
[1]	Restated to conform to ASC 842. See accompanying Note 2.

Net Loss per Share - Basic and

Net Loss per Share - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (233,636)	$ (123,215)	[1]	$ (474,579)	$ (390,731)	[1]
Denominator:
Weighted average common shares used in net loss per share, basic and diluted (in shares)	394,682,744	330,769,341	[2]	376,174,283	329,592,322	[2]
Net loss per share, basic and diluted (usd per share)	$ (0.59)	$ (0.37)	[2]	$ (1.26)	$ (1.19)	[2]
[1]	Restated to conform to ASC 842. See accompanying Note 2.
[2]	Restated to conform to ASC 842. See accompanying Note 2.

Net Loss per Share - Common Sto

Net Loss per Share - Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	39,433,994	50,643,406
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	37,261,817	48,962,655
Restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	0	21,564
Restricted common stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities (in shares)	2,172,177	1,659,187

Subsequent Events (Details)

Subsequent Events (Details) dose in Millions	1 Months Ended
	Oct. 30, 2020dose
Subsequent event | Supply agreement with international government agency
Subsequent Event [Line Items]
Number of doses of vaccine candidate	50