Agios Pharmaceuticals (AGIO) 10-K 19 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 13, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-36014
Entity Registrant Name	AGIOS PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-0662915
Entity Address, Address Line One	88 Sidney Street
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	649-8600
Title of 12(b) Security	Common Stock, Par Value $0.001 per share
Trading Symbol	AGIO
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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 Public Float			$ 2,563,418,196
Entity Common Stock, Shares Outstanding		68,513,573
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement for its 2020 Annual Meeting of Stockholders to be filed pursuant to Regulation 14A within 120 days of the end of the registrant’s fiscal year ended December 31, 2019 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Central Index Key	0001439222
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 80,931	$ 70,502
Marketable securities	483,946	514,800
Accounts receivable, net	8,952	5,076
Collaboration receivable – related party	1,539	2,462
Collaboration receivable – other	1,928	670
Royalty receivable – related party	2,900	2,234
Inventory	7,331	869
Prepaid expenses and other current assets	24,177	17,167
Total current assets	611,704	613,780
Marketable securities	152,929	220,119
Operating lease assets	93,643
Property and equipment, net	31,472	24,320
Financing lease assets	993
Other non-current assets	0	238
Total assets	890,741	858,457
Current liabilities:
Accounts payable	21,896	17,880
Accrued expenses	53,142	42,147
Deferred revenue – related party	10,933	32,710
Operating lease liabilities	6,642
Deferred rent	0	766
Financing lease liabilities	273
Total current liabilities	92,886	93,503
Deferred revenue, net of current portion – related party	50,580	59,809
Operating lease liabilities, net of current portion	106,074
Deferred rent, net of current portion	0	17,608
Financing lease liabilities, net of current portion	673
Total liabilities	250,213	170,920
Commitments and contingent liabilities (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized, no shares issued and outstanding at December 31, 2019 and 2018	0	0
Common stock, $0.001 par value; 125,000,000 shares authorized and 68,401,105 and 58,218,653 shares issued and outstanding at December 31, 2019 and 2018, respectively	68	58
Additional paid-in capital	2,156,363	1,794,283
Accumulated other comprehensive income (loss)	202	(2,171)
Accumulated deficit	(1,516,105)	(1,104,633)
Total stockholders’ equity	640,528	687,537
Total liabilities and stockholders’ equity	$ 890,741	$ 858,457

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	125,000,000	125,000,000
Common stock, shares issued (in shares)	68,401,105	58,218,653
Common stock, shares outstanding (in shares)	68,401,105	58,218,653

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Revenues		$ 117,912	$ 94,387	$ 43,011
Cost and expenses:
Cost of sales		1,317	1,397	0
Research and development	[1]	410,894	341,324	292,681
Selling, general and administrative		132,034	114,145	71,124
Total cost and expenses		544,245	456,866	363,805
Loss from operations		(426,333)	(362,479)	(320,794)
Interest income, net		14,861	16,451	6,124
Net loss		$ (411,472)	$ (346,028)	$ (314,670)
Net loss per share - basic and diluted (in usd per share)		$ (6.86)	$ (6.03)	$ (6.75)
Weighted-average number of common shares used in computing net loss per share - basic and diluted (in shares)		59,994,539	57,418,300	46,587,631
Product revenue, net
Revenues:
Revenues		$ 59,851	$ 13,841	$ 0
Collaboration revenue – related party
Revenues:
Revenues		39,257	60,661	41,074
Collaboration revenue – other
Revenues:
Revenues		8,262	12,670	0
Royalty revenue – related party
Revenues:
Revenues		$ 10,542	$ 7,215	$ 1,937
[1]	(1) Total research and development expenses are net of cost reimbursements from related party of $0, $0, and $7,811 for the years ended December 31, 2019, 2018 and 2017, respectively.

Consolidated Statements of Op_2

Consolidated Statements of Operations (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Reduction of research and development costs	$ 0	$ 0	$ 7,811,000

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (411,472)	$ (346,028)	$ (314,670)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	2,373	(782)	(1,076)
Comprehensive loss	$ (409,099)	$ (346,810)	$ (315,746)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2016		42,220,444
Beginning balance at Dec. 31, 2016	$ 358,591	$ 42	$ 842,013	$ (313)	$ (483,151)
Unrealized gain on available-for-sale securities	(1,076)			(1,076)
Net loss	(314,670)				(314,670)
Stock-based compensation expense	47,809		47,809
Issuance of common stock under stock incentive and employee stock purchase plan (in shares)		797,629
Issuance of common stock under stock incentive and employee stock purchase plans	14,190	$ 1	14,189
Issuance of common stock for follow-on offering (in shares)		5,808,080
Issuance of common stock for follow-on offering	270,250	$ 6	270,244
Other	409		649		(240)
Ending balance (in shares) at Dec. 31, 2017		48,826,153
Ending balance at Dec. 31, 2017	375,503	$ 49	1,174,904	(1,389)	(798,061)
Unrealized gain on available-for-sale securities	(782)			(782)
Net loss	(346,028)				(346,028)
Stock-based compensation expense	73,357		73,357
Issuance of common stock under stock incentive and employee stock purchase plan (in shares)		1,239,514
Issuance of common stock under stock incentive and employee stock purchase plans	30,216	$ 1	30,215
Issuance of common stock for follow-on offering (in shares)		8,152,986
Issuance of common stock for follow-on offering	516,206	$ 8	516,198
Other	(391)		(391)
Ending balance (in shares) at Dec. 31, 2018		58,218,653
Ending balance at Dec. 31, 2018	687,537	$ 58	1,794,283	(2,171)	(1,104,633)
Unrealized gain on available-for-sale securities	2,373			2,373
Net loss	(411,472)				(411,472)
Stock-based compensation expense	$ 72,373		72,373
Issuance of common stock under stock incentive and employee stock purchase plan (in shares)	283,200	694,952
Issuance of common stock under stock incentive and employee stock purchase plans	$ 12,516	$ 1	12,515
Issuance of common stock for follow-on offering (in shares)		9,487,500
Issuance of common stock for follow-on offering	277,201	$ 9	277,192
Ending balance (in shares) at Dec. 31, 2019		68,401,105
Ending balance at Dec. 31, 2019	$ 640,528	$ 68	$ 2,156,363	$ 202	$ (1,516,105)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net loss	$ (411,472)	$ (346,028)	$ (314,670)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8,087	7,172	6,432
Stock-based compensation expense	72,373	73,357	47,809
Net accretion of discount on marketable securities	(3,195)	(3,837)	(11)
Loss on disposal of property and equipment	1,052	20	40
Non-cash operating lease expense	8,532
Changes in operating assets and liabilities:
Accounts receivable, net	(3,876)	(5,076)	0
Collaboration receivable – related party	923	(14)	2,438
Collaboration receivable – other	(1,258)	(670)	0
Royalty receivable – related party	(666)	(1,012)	(1,222)
Inventory	(6,462)	(869)	0
Prepaid expenses and other current and non-current assets	(7,742)	1,148	(3,600)
Accounts payable	3,716	(5,488)	5,329
Accrued expenses	7,233	8,623	1,522
Deferred revenue – related party	(31,006)	(31,665)	(26,570)
Operating lease liabilities	(6,861)
Deferred rent	0	(82)	(2,729)
Net cash used in operating activities	(370,622)	(304,421)	(285,232)
Investing activities
Purchases of marketable securities	(488,566)	(933,320)	(688,702)
Proceeds from maturities and sales of marketable securities	592,177	666,481	635,421
Purchases of property and equipment	(12,171)	(6,986)	(4,627)
Net cash provided by (used in) investing activities	91,440	(273,825)	(57,908)
Financing activities
Payments on financing lease obligations	(113)
Proceeds from public offering of common stock, net of reimbursements	277,201	516,206	270,250
Reimbursement (payment) of public offering costs	0	(391)
Reimbursement (payment) of public offering costs			638
Net proceeds from stock option exercises and employee stock purchase plan	12,523	30,209	14,222
Net cash provided by financing activities	289,611	546,024	285,110
Net change in cash and cash equivalents	10,429	(32,222)	(58,030)
Cash and cash equivalents at beginning of the period	70,502	102,724	160,754
Cash and cash equivalents at end of the period	80,931	70,502	102,724
Supplemental disclosure of non-cash investing and financing transactions:
Additions to property and equipment in accounts payable and accrued expenses	5,168	1,106	1,011
Proceeds from stock option exercises in other current assets	0	$ 7	$ 0
Operating lease liabilities arising from obtaining operating lease assets	42,322
Financing lease liabilities arising from obtaining financing lease assets	$ 1,052

Nature of Business

Nature of Business	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business References to Agios Throughout this Annual Report on Form 10-K, “we,” “us,” and “our,” and similar expressions, except where the context requires otherwise, refer to Agios Pharmaceuticals, Inc. and its consolidated subsidiaries, and “our board of directors” refers to the board of directors of Agios Pharmaceuticals, Inc. Overview We are a biopharmaceutical company committed to the fundamental transformation of patients’ lives through scientific leadership in the field of cellular metabolism and adjacent areas of biology, with the goal of creating differentiated, small molecule medicines for patients in the areas of hematologic malignancies, solid tumors and rare genetic diseases, or RGDs. To address these focus areas, we take a systems biology approach to deeply understand disease states, drive the discovery and validation of novel therapeutic targets, and define patient selection strategies, thereby increasing the probability that our experimental medicines will have the desired therapeutic effect. We are located in Cambridge, Massachusetts. Our wholly-owned product, TIBSOVO® (ivosidenib) is an oral targeted inhibitor of the mutated isocitrate dehydrogenase 1, or IDH1 enzyme. TIBSOVO® is the first and only U.S. Food and Drug Administration, or FDA-approved therapy for the treatment of adult patients with (i) relapsed or refractory acute myeloid leukemia, or R/R AML, with a susceptible IDH1 mutation as detected by an FDA-approved test (approved by the FDA in July 2018) and (ii) newly diagnosed AML with a susceptible IDH1 mutation as detected by an FDA-approved test who are at least 75 years old or who have comorbidities that preclude use of intensive induction chemotherapy (approved by the FDA in May 2019). In December 2018, we submitted an Marketing Authorization Application, or MAA, to the European Medicines Agency, or EMA, for TIBSOVO® for the treatment of adult patients with R/R AML with an IDH1 mutation. Our other marketed product is IDHIFA® (enasidenib), an oral targeted inhibitor of the mutated isocitrate dehydrogenase 2, or IDH2 enzyme and the first and only FDA-approved therapy for patients with R/R AML and an IDH2 mutation. In August 2017, the FDA granted our collaboration partner Celgene approval of IDHIFA® for the treatment of adult patients with R/R AML and an IDH2, mutation as detected by an FDA-approved test. We are eligible to receive royalties at tiered low-double digit to mid-teen percentage rates on any net sales of IDHIFA® and have exercised our rights to provide up to one-third of the field-based commercialization efforts in the United States. In June 2018, Celgene submitted an MAA to the EMA for IDHIFA® for IDH2 mutant-positive AML which it subsequently withdrew in December 2019. Our pre-commercial clinical cancer product candidates are vorasidenib, AG-270, and AG-636. Vorasidenib is an orally available, selective brain-penetrant pan-IDH mutant inhibitor. We are developing vorasidenib for the treatment of IDH mutant-positive low grade glioma and are currently evaluating vorasidenib in clinical trials. AG-270 is an orally available selective potent inhibitor of methionine adenosyltransferase 2a, or MAT2A. We are currently evaluating AG-270 in a phase 1 dose-escalation and expansion trial in multiple tumor types carrying a methylthioadenosine phosphorylase, or MTAP, deletion. AG-636 is an inhibitor of the metabolic enzyme dihydroorotate dehydrogenase, or DHODH. We are currently evaluating AG-636 in the phase 1 dose-escalation trial in lymphoma. The lead product candidate in our RGD portfolio, mitapivat, is an activator of both wild-type and mutant pyruvate kinase-R for the potential treatment of hemolytic anemias. We are currently evaluating mitapivat for the treatment of pyruvate kinase, or PK, deficiency, thalassemia and sickle cell disease, or SCD, in clinical trials. In addition to the aforementioned development programs, we are seeking to advance a number of early-stage discovery programs in our focus areas of malignant hematology, solid tumors and RGDs based on our scientific leadership in the field of cellular metabolism and adjacent areas of biology. We are subject to risks common to companies in our industry including, but not limited to, uncertainties relating to conducting clinical research and development, the manufacture and supply of products for clinical and commercial use, obtaining and maintaining regulatory approvals and pricing and reimbursement for our products, market acceptance, managing global growth and operating expenses, availability of additional capital, competition, obtaining and enforcing patents, stock price volatility, dependence on collaborative relationships and third-party service providers, dependence on key personnel, potential litigation, product liability claims and government investigations. Liquidity In November 2019, we completed a public offering of 8,250,000 shares of common at an offering price of $31.00 per share. We received net proceeds from this offering of $241.0 million, after deducting underwriting discounts and commissions paid by us. In addition, we granted the underwriters the right to purchase up to an additional 1,237,500 shares of common stock, which was exercised in November 2019, resulting in additional net proceeds to us of $36.2 million, after underwriting discounts and commissions. After giving effect to the full exercise of the over-allotment option, the number of shares sold by us in the public offering totaled 9,487,500 shares, and net proceeds to us totaled $277.2 million, after underwriting discounts and commissions. As of December 31, 2019, we had cash, cash equivalents and marketable securities of $717.8 million. Although we have incurred recurring losses and expect to continue to incur losses for the foreseeable future, we expect our cash, cash equivalents and marketable securities to be sufficient to fund current operations for at least the next twelve months from the issuance of the financial statements. If the Company is unable to raise additional funds through equity or debt financings, the Company may be required to delay, limit, reduce or terminate product development or future commercialization efforts or grant rights to develop and market products or product candidates that the Company would otherwise prefer to develop and market itself.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of consolidation The consolidated financial statements include our accounts and the accounts of our wholly owned subsidiaries, Agios Securities Corporation, Agios International Sarl, Agios Germany GmbH, Agios Netherlands B.V., and Agios Limited. All intercompany transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles, or U.S. GAAP. Use of estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates. Cash and cash equivalents We consider highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are stated at fair value. Marketable securities Marketable securities at December 31, 2019 and 2018 consisted of investments in certificates of deposit, U.S. Treasuries, government securities and corporate debt securities. We determine the appropriate classification of the securities at the time they are acquired and evaluate the appropriateness of such classifications at each balance sheet date. We classify our marketable securities as available-for-sale pursuant to Accounting Standards Codification, or ASC, 320, Investments – Debt and Equity Securities . Marketable securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive loss in stockholders’ equity and a component of total comprehensive loss in the consolidated statements of comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. At December 31, 2019 and 2018, we held both current and non-current investments. Investments classified as current have maturities of less than one year. Investments classified as non-current are those that: (i) have a maturity of one We review marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if we experience a credit loss, have the intent to sell the marketable security, or if it is more likely than not that we will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with our investment policy, the severity and the duration of the impairment, and changes in value subsequent to the end of the period. Fair value measurements We record cash equivalents and marketable securities at fair value. ASC 820, Fair Value Measurements and Disclosures , establishes a fair value hierarchy for those instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and our own assumptions (unobservable inputs). The hierarchy consists of three levels: Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3 – Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. Our financial assets, which include cash equivalents and marketable securities, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models, including both income and market based approaches, and observable market inputs to determine value. After completing our validation procedures, we did not adjust or override any fair value measurements provided by the pricing services as of December 31, 2019 or 2018. Fair value information for these assets, including their classification in the fair value hierarchy is included in Note 3. Fair Value Measurements . There have been no changes to the valuation methods during the years ended December 31, 2019 and 2018. We evaluate transfers between levels at the end of each reporting period. The carrying amounts of collaboration receivable – related party, collaboration receivable – other, royalty receivable – related party, accounts receivable, prepaid expenses and other current assets, accounts payable, and accrued expenses approximate their fair values due to their short-term maturities. Accounts receivable, net Our trade accounts receivable arise from product sales and represent amounts due from specialty distributors and specialty pharmacy providers in the U.S. We monitor the financial performance and creditworthiness of our customers so that we can properly assess and respond to changes in their credit profile. We reserve against these receivables for estimated losses that may arise from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. Concentrations of credit risk Financial instruments which potentially subject us to credit risk consist primarily of cash, cash equivalents, and marketable securities. We hold these investments in highly rated financial institutions, and, by policy, limit the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. We have not experienced any credit losses in such accounts and do not believe we are exposed to any significant credit risk on these funds. We have no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts, or other hedging arrangements. We are also subject to credit risk on our receivables, including trade receivables from our customers and collaboration and royalty receivables from Celgene and CStone Pharmaceuticals, or CStone. Concentrations of credit risk with respect to receivables, which are typically unsecured, are somewhat mitigated due to the number of customers using our products. Our trade receivables arise from product sales in the U.S. and have standard payment terms that generally require payment within 30 to 60 days. We have evaluated the creditworthiness of our customers, including Celgene, and determined them to be creditworthy. To date we have not experienced any losses with respect to our receivables. Inventory Inventory is stated at the lower of cost or estimated net realizable value on a first-in, first-out basis. Prior to the regulatory approval of our product candidates, we incur expenses for the manufacture of drug product that could potentially be available to support the commercial launch of those products. Until the date at which regulatory approval has been received or is otherwise considered probable, we record all such costs as research and development expenses. Upon approval of our wholly owned product, TIBSOVO®, by the FDA on July 20, 2018 for the treatment of adult patients with R/R AML with susceptible IDH1 mutation as detected by an FDA-approved test, we began to capitalize inventories of TIBSOVO®. We perform an assessment of the recoverability of capitalized inventory during each reporting period and write down any excess and obsolete inventory to its estimated net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales in the consolidated statements of operations. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required. Property and equipment Property and equipment consist of laboratory equipment, computer equipment and software, leasehold improvements, furniture and fixtures, and office equipment. Costs of major additions and betterment are capitalized; maintenance and repairs, which do not improve or extend the life of the respective assets, are charged to expense as incurred. Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and the resulting gain or loss is recognized. Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets: Years Laboratory equipment 5 Computer equipment and software 3 Furniture and fixtures 5 Office equipment 5 Leasehold improvements are amortized over the lesser of the remaining lease term or the estimated useful life of the improvement. Impairment of long-lived assets We periodically evaluate our long-lived assets for potential impairment in accordance with ASC 360, Property, Plant and Equipment . Potential impairment is assessed when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. Recoverability of these assets is assessed based on the undiscounted expected future cash flows from the assets, considering a number of factors, including past operating results, budgets and economic projections, market trends and product development cycles. If impairments are identified, assets are written down to their estimated fair value. We did not recognize any impairment charges through December 31, 2019. Leases We determine if an arrangement is a lease at inception. An arrangement is determined to contain a lease if the contract conveys the right to control the use of an identified property or equipment for a period of time in exchange for consideration. If we can benefit from the various underlying assets of a lease on their own or together with other resources that are readily available, or if the various underlying assets are neither highly dependent on nor highly interrelated with other underlying assets in the arrangement, they are considered to be a separate lease component. In the event multiple underlying assets are identified, the lease consideration is allocated to the various components based on each of the component’s relative fair value. Operating lease assets represent our right to use an underlying asset for the lease term and operating lease liabilities represent our obligation to make lease payments arising from the leasing arrangement. Operating lease assets and operating lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, in determining the operating lease liabilities, we use an estimate of our incremental borrowing rate. The incremental borrowing rate is determined using two alternative credit scoring models to estimate our credit rating, adjusted for collateralization. The calculation of the operating lease assets includes any lease payments made and excludes any lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. For operating leases, we record operating lease assets and lease liabilities in our consolidated balance sheets. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Short-term leases, or leases that have a lease term of 12 months or less at commencement date, are excluded from this treatment and are recognized on a straight-line basis over the term of the lease. We have not entered into any material short-term leases or financing leases as of December 31, 2019. Revenue from contracts with customers On January 1, 2018 we adopted ASC 606, Revenue from Contracts with Customers , under the modified retrospective method. Prior to January 1, 2018 we accounted for the consideration received under the Collaboration Agreements under ASC 605-25, Multiple Element Arrangements. In adopting ASC 606, we applied the practical expedient that permits aggregating the effect of all contract modifications that occurred prior to January 1, 2018. No other practical expedients were used. Similar to the accounting under ASC 605-25, the 2016 Agreement was determined to be a modification of the 2010 Agreement and the AG-881 Agreements with Celgene. Revenue is recognized when the customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that we determined to be within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract and determine those that are performance obligations, and assess whether each promised good or service is distinct. We will then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product revenue We generate product revenue from sales of TIBSOVO® to a limited number of specialty distributors and specialty pharmacy providers in the U.S., or collectively, the Customers. The Customers subsequently resell TIBSOVO® to pharmacies or dispense directly to patients. In addition to distribution agreements with Customers, we enter into arrangements with healthcare providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts with respect to the purchase of TIBSOVO®. The performance obligation related to the sale of TIBSOVO® is satisfied and revenue is recognized when the Customer obtains control of the product, which occurs at a point in time, typically upon delivery to the Customer. Revenues from product sales are recorded at the net sales price, or transaction price, which includes estimates of variable consideration for which reserves are established and result from contractual adjustments, government rebates, returns and other allowances that are offered within the contracts with our Customers, healthcare providers, payors and other indirect customers relating to the sale of our products. Contractual adjustments. We generally provide Customers with discounts, including prompt pay discounts, and allowances that are explicitly stated in the contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. Chargebacks and discounts represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from us. Customers charge us for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are estimated using the expected value method, based upon a range of possible outcomes that are probability-weighted for the estimated channel mix and are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue. Government rebates. Government rebates consist of Medicare, TriCare, and Medicaid rebates, which we estimate using the expected value method, based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue. For Medicare, we also estimate the number of patients in the prescription drug coverage gap for whom we will owe an additional liability under the Medicare Part D program. Returns. We estimate the amount of product sales that may be returned by Customers and record this estimate as a reduction of revenue in the period the related product revenue is recognized. We currently estimate product return liabilities using the expected value method, based on available industry data, including our visibility into the inventory remaining in the distribution channel. Collaboration revenue We apply the provisions of ASC 808, Collaborative Arrangements, when accounting for our collaboration agreements. We evaluate the presentation of amounts due from our collaborative partners associated with activities in the collaborative arrangement based on the nature of each activity. For transactions with customers, we have reported revenues and costs in accordance with ASC 606, Revenue from Contracts with Customers , ASC 606-10-55-36 through 55-40, Principal versus Agent Considerations . We recognize revenue when the customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that have been determined to be within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract based on the relative standalone selling prices of the goods or services provided; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. Once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract and determine those that are performance obligations, and assess whether each promised good or service is distinct. We will then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The transaction price for each collaboration agreement is determined based on the amount of consideration we expect to be entitled to for satisfying all performance obligations within the agreement. Significant judgment may be required in determining the amount of variable consideration to be included in the transaction price. We use the expected value methods to determine variable consideration and will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. As part of the initial accounting for these arrangements, we must develop assumptions that require judgment to determine the standalone selling price, or SSP, for each performance obligation identified in the contract. We use these key assumptions to determine the SSP, which include forecast of revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. We recognize the transaction price allocated to upfront license payments as revenue upon delivery of the license to the customer and resulting ability of the customer to use and benefit from the license, if the license is determined to be distinct from the other performance obligations identified in the contract. If the license is considered to not be distinct from other performance obligations, we exercise judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied (i) at a point in time, but only for licenses determined to be distinct from other performance obligations in the contract, or (ii) over time; and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from license payments. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. A significant portion of revenue generated from our collaboration agreements with Celgene relates to the provision of research and development services whereby revenue is recognized under an input method using the ratio of effort incurred to date compared to the total estimated effort required to complete the performance obligation. The calculation of the total estimated effort includes the total amount of forecasted costs associated with the completion of discovery, pre-clinical or clinical trials, as well as the assumed timing of these activities and estimated patient populations. Such cost estimates include forecasted direct labor and material costs, subcontractor costs, and external contract research organization, or CRO, costs. Milestone revenue Many of our collaboration agreements also entitle us to additional payments upon the achievement of performance-based milestones. These milestones are generally categorized into three types: development milestones, which are generally based on the initiation of clinical trials; regulatory milestones, which are generally based on the submission, filing or approval of regulatory applications such as a new drug application, or NDA, in the U.S.; and sales-based milestones, which are generally based on meeting specific thresholds of sales in certain geographic areas during a specified period. Upfront and ongoing development milestones per our collaboration agreements are not subject to refund if the development activities are not successful. For each collaboration that includes development milestone payments, we evaluate whether it is probable that the consideration associated with each milestone will not be subject to a significant reversal in the cumulative amount of revenue recognized. Amounts that meet this threshold are included in the transaction price using the most likely amount method, whereas amounts that do not meet this threshold are considered constrained and excluded from the transaction price until they meet this threshold. Milestones tied to regulatory approval, and therefore not within our control, are considered constrained until such approval is received. At the end of each subsequent reporting period, we re-evaluate the probability of a significant reversal of the cumulative revenue recognized for our milestones, and, if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues from collaborators and loss in the period of adjustment. For arrangements that include sales-based milestone or royalty payments based on the level of sales, and in which the license is deemed to be the predominant item to which the sales-based milestone or royalties relate to, we recognize revenue in the period in which the sales-based milestone is achieved and in the period in which the sales associated with the royalty occur. Adoption of ASC 606 We adopted ASC 606 using the modified retrospective method. Under this method, we recognized the cumulative effect of the change in the opening balance of accumulated deficit in the December 31, 2018 consolidated balance sheet. In adopting ASC 606, we applied the practical expedient that permits aggregating the effect of all contract modifications that occurred prior to January 1, 2018. No other practical expedients were used. The impact of the cumulative effect of the accounting changes upon the adoption of the standard is as follows: (In thousands) December 31, Cumulative January 1, Deferred revenue – related party, current and net of current portions $ 163,640 $ (39,456) $ 124,184 Accumulated deficit (798,061) 39,456 (758,605) The following tables summarize the effects of adopting ASC 606 on our consolidated financial statements: Consolidated Balance Sheets December 31, 2018 (In thousands) Under Topic Under Topic Effect of Accounts receivable, net $ 5,076 $ 5,076 $ — Collaboration receivable – related party 2,462 2,462 — Collaboration receivable – other 670 230 440 Total current assets 613,780 613,340 440 Total assets 858,457 858,017 440 Deferred revenue – related party 32,710 29,133 3,577 Total current liabilities 93,503 89,926 3,577 Deferred revenue, net of current portion – related party 59,809 101,180 (41,371) Total liabilities 170,920 208,714 (37,794) Accumulated deficit (1,104,633) (1,142,867) 38,234 Total stockholders’ equity 687,537 649,303 38,234 Total liabilities and stockholders’ equity 858,457 858,017 440 Consolidated Statements of Operations Year ended December 31, 2018 (In thousands, except per share data) Under Topic Under Topic Effect of Product revenue, net $ 13,841 $ 13,841 $ — Collaboration revenue – related party 60,661 58,994 1,667 Collaboration revenue – other 12,670 12,230 440 Total revenue 94,387 92,280 2,107 Research and development expense 341,324 337,995 3,329 Total cost and expenses 456,866 453,537 3,329 Loss from operations (362,479) (361,257) (1,222) Net loss (346,028) (344,806) (1,222) Net loss per share – basic and diluted (6.03) (6.01) (0.02) Consolidated Statements of Comprehensive Loss Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Comprehensive loss (346,810) (345,588) (1,222) Consolidated Statements of Cash Flows Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Adjustments to reconcile net loss to net cash used in operating activities: Accounts receivable, net (5,076) (5,076) — Collaboration receivable – related party (14) (14) — Collaboration receivable – other (670) (230) (440) Deferred revenue – related party (31,665) (33,327) 1,662 Cost of Sales Cost of sales consists primarily of manufacturing costs of TIBSOVO®. Based on our policy to expense costs associated with the manufacturing of our products prior to regulatory approval, certain of the manufacturing costs associated with product shipments of TIBSOVO® recorded during the years ended December 31, 2019 and December 31, 2018 were expensed prior to July 20, 2018 and, therefore, are not included in costs of sales during the years ended December 31, 2019 or 2018. Research and development costs Research and development costs, including those accrued as of each balance sheet date, are expensed as incurred. These costs include salaries and personnel-related costs, consulting fees, fees paid for contract research services, fees paid to contract CROs, and other third parties in connection with clinical trials and preclinical development activities, fees paid to investigative sites in connection with clinical studies, the costs associated with the product manufacturing, development, and distribution of clinical supplies, the costs of laboratory equipment and facilities, and other external costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. Additionally, there may be instances in which payments made to our vendors will exceed the level of services provided, and result in a prepayment of the research and development expense. The capitalized amounts are expensed as the related goods are delivered or the services are performed. We estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual or prepaid accordingly. Stock-based compensation We account for stock-based compensation awards in accordance with ASC 718, Compensation –Stock Compensation , or ASC 718. For stock-based awards granted to employees and to members of the board of directors for their services and for participation in our employee stock purchase plan, we primarily estimate the grant date fair value of each option award using the Black-Scholes option-pricing model. The use of the Black-Scholes option-pricing model requires us to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. For awards subject to service-based vesting conditions, we recognize stock-based compensation expense equal to the grant date fair value of stock options on a straight-line basis over the requisite service period. For awards subject to both performance and service-based vesting conditions, we recognize stock-based compensation expense over the remaining service period if the performance condition is considered probable of achievement using management’s best estimates. In 2017, we adopted ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of the accounting for employee share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification in the statement of cash flows. Upon adoption of this standard, we recorded a cumulative-effect adjustment of approximately $32.7 million through retained earnings and deferred tax assets. Income taxes Income taxes are recorded in accordance with ASC 740, Accounting for Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in our financial statements or tax returns. We determine our deferred tax assets and liabilities based on differences between the financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. We also account for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, we recognize the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. Comprehensive income (loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances, and currently consists of net loss and unrealized gains and losses on available-for-sale securities. Accumulated other comprehensive loss consists entirely of unrealized gains and losses from available-for-sale securities as of December 31, 2019 and 2018. Net loss per share Basic net loss per share is calculated by dividing net loss by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the dil

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following table summarizes our cash equivalents and marketable securities measured at fair value and by level (as described in Note 2. Summary of Significant Accounting Policies ) on a recurring basis as of December 31, 2019: (In thousands) Level 1 Level 2 Level 3 Total Cash equivalents $ 12,568 $ 36,299 $ — $ 48,867 Total cash equivalents 12,568 36,299 — 48,867 Marketable securities: Certificates of deposit — — — — U.S. Treasuries — 214,027 — 214,027 Government securities — 97,820 — 97,820 Corporate debt securities — 325,028 — 325,028 Total marketable securities — 636,875 — 636,875 Total cash equivalents and marketable securities $ 12,568 $ 673,174 $ — $ 685,742 There were no transfers between Level 1 and Level 2 and we had no financial assets or liabilities that were classified as Level 3 at any point during the year ended December 31, 2019.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Marketable securities at December 31, 2019 consisted of the following: (In thousands) Amortized Unrealized Unrealized Fair Current: Certificates of deposit $ — $ — $ — $ — U.S. Treasuries 178,721 58 (38) 178,741 Government securities 80,228 17 (16) 80,229 Corporate debt securities 224,928 139 (91) 224,976 Total Current 483,877 214 (145) 483,946 Non-current: U.S. Treasuries 35,296 3 (13) 35,286 Government securities 17,587 14 (10) 17,591 Corporate debt securities 99,913 239 (100) 100,052 Total Non-current 152,796 256 (123) 152,929 Total marketable securities $ 636,673 $ 470 $ (268) $ 636,875 Marketable securities at December 31, 2018 consisted of the following: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 960 $ — $ (4) $ 956 U.S. Treasuries 231,101 7 (228) 230,880 Government securities 75,335 — (121) 75,214 Corporate debt securities 208,233 — (483) 207,750 Total Current 515,629 7 (836) 514,800 Non-current: U.S. Treasuries 12,202 4 (125) 12,081 Government securities 70,177 10 (188) 69,999 Corporate debt securities 139,082 12 (1,055) 138,039 Total Non-current 221,461 26 (1,368) 220,119 Total marketable securities $ 737,090 $ 33 $ (2,204) $ 734,919 There were no material realized gains or losses on marketable securities for the years ended December 31, 2019 and 2018. At December 31, 2019 and 2018, we held 113 and 242 debt securities that were in an unrealized loss position for less than one year, respectively. The aggregate fair value of debt securities in an unrealized loss position at December 31, 2019 and 2018 was $345.7 million and $639.3 million, respectively. There were no individual securities that were in a significant unrealized loss position as of December 31, 2019 and 2018. Given our intent and ability to hold such securities until recovery, and the lack of material change in the credit risk of these investments, we do not consider these marketable securities to be other-than-temporarily impaired as of December 31, 2019 and 2018.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment, net consisted of the following at December 31: (In thousands) 2019 2018 Laboratory equipment $ 23,418 $ 20,165 Computer equipment and software 6,415 5,449 Leasehold improvements 23,879 22,084 Furniture and fixtures 2,101 1,065 Office equipment 589 407 Construction in progress 7,182 1,302 Total property and equipment 63,584 50,472 Less: accumulated depreciation (32,112) (26,152) Total property and equipment, net $ 31,472 $ 24,320 Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was $8.0 million, $7.2 million and $6.4 million, respectively.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory	Inventory Inventory consisted of the following at December 31: (In thousands) 2019 2018 Raw materials $ 180 $ — Work-in-process 6,808 788 Finished goods 343 81 Total Inventory $ 7,331 $ 869

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Leases Our building leases are comprised of office and laboratory space under non-cancelable operating leases. These lease agreements have remaining lease terms of eight years and contain various clauses for renewal at our option. The renewal options were not included in the calculation of the operating lease assets and the operating lease liabilities as the renewal option is not reasonably certain of being exercised. The lease agreements do not contain residual value guarantees. Operating lease costs for the year ended December 31, 2019 were $15.1 million, and cash paid for amounts included in the measurement of operating lease liabilities for the year ended December 31, 2019 was $12.8 million. On April 11, 2019, we entered into an agreement to lease approximately 13,000 square feet of office space located at 38 Sidney Street, Cambridge, Massachusetts, or the 38 Sidney Lease, with Thirty-Eight Sidney Street, LLC. The initial term of the 38 Sidney Lease commenced on May 1, 2019 and expires on February 29, 2028. At the end of the lease term, we have the option to extend the 38 Sidney Lease for two consecutive terms of five years at fair market rent at the time of the extension. The 38 Sidney Lease provides us with the right to lease additional space within the 38 Sidney Street building and also includes rent escalation clauses and a tenant improvement allowance of $1.0 million. In connection with the 38 Sidney Lease, we also amended our existing building leases at 88 Sidney Street, Cambridge, Massachusetts and at 64 Sidney Street, Cambridge, Massachusetts to extend the initial terms of those leases by approximately three years through February 29, 2028. The amendments also provide us with the right to lease additional space at the 64 Sidney Street building. Our existing extension options for the 88 Sidney Street building and 64 Sidney Street building continue as set forth in the existing leases for those buildings. We have not entered into any material short-term leases or financing leases as of December 31, 2019. In arriving at the operating lease liabilities as of December 31, 2019, we applied the weighted-average incremental borrowing rate of 5.7% over a weighted-average remaining lease term of 8.2 years. As of December 31, 2019, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter, were as follows: (In thousands) 2020 $ 13,242 2021 14,380 2022 16,773 2023 18,126 2024 18,660 Thereafter 63,891 Undiscounted minimum rental commitments 145,072 Interest (32,356) Total operating lease liabilities $ 112,716 As of December 31, 2018, minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter, were as follows: (In thousands) 2019 $ 12,759 2020 13,135 2021 13,473 2022 15,552 2023 17,145 Thereafter 19,223 Total minimum rental commitments $ 91,287 Rental expense under these leases, net of tenant improvement reimbursements, amounted to $11.4 million, and $6.0 million for the years ended December 31, 2018 and 2017, respectively. In addition to rent, the leases may require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses. We provided our landlord a standby letter of credit of $2.9 million as security for our leases. We are not required to maintain any cash collateral for the standby letter of credit.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses and other current liabilities consisted of the following at December 31: (In thousands) 2019 2018 Accrued compensation $ 18,982 $ 20,843 Accrued research and development costs 21,777 14,777 Accrued professional fees 8,335 5,441 Accrued other 4,048 1,086 Total accrued expenses $ 53,142 $ 42,147

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities Manufacturing Commitments We are party to various agreements with contract manufacturing organizations that we are not contractually able to terminate for convenience and avoid any and all future obligations to the vendors. Under such agreements, we are obligated to make certain minimum payments, with the exact amounts in the event of termination to be based on the timing of the termination and the exact terms of the agreement. Legal Contingencies From time to time, we may be involved in disputes and legal proceedings in the ordinary course of business. These proceedings may include allegations of infringement of intellectual property, employment or other matters. We do not have any ongoing legal proceedings that, based on our estimates, could have a material effect on our consolidated financial statements.

Product Revenue

Product Revenue	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Product Revenue	Product Revenue Our wholly owned product, TIBSOVO®, received approval from the FDA on July 20, 2018 for the treatment of adult patients with R/R AML with a susceptible IDH1 mutation. Upon FDA approval of TIBSOVO® in the U.S., we began generating product revenue from U.S. sales of TIBSOVO®. (In thousands) 2019 2018 2017 Product revenue, net $ 59,851 $ 13,841 $ — The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2019: (In thousands) Contractual Government Returns Total Balance at December 31, 2018 592 325 334 1,251 Current provisions relating to sales in the current year 7,899 2,387 1,464 11,750 Adjustments relating to prior years 8 (41) — (33) Payments/returns relating to sales in the current year (7,027) (1,286) — (8,313) Payments/returns relating to sales in the prior years (598) (261) — (859) Balance at December 31, 2019 874 1,124 1,798 3,796 The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2018: (In thousands) Contractual Government Returns Total Balance at December 31, 2017 — — — — Current provisions relating to sales in the current year 1,777 422 334 2,533 Adjustments relating to prior years — — — — Payments/returns relating to sales in the current year (1,185) (97) — (1,282) Payments/returns relating to sales in the prior years — — — — Balance at December 31, 2018 592 325 334 1,251 Total revenue-related reserves for the years ended December 31, 2019 and 2018 above, included in our consolidated balance sheets, are summarized as follows: (In thousands) December 31, December 31, Reduction of accounts receivable $ 540 $ 326 Component of accrued expenses 3,256 925 Total revenue-related reserves $ 3,796 $ 1,251 The following table presents changes in our contract assets and liabilities during the year ended December 31, 2019: (In thousands) December 31, Additions Deductions December 31, Contract assets Accounts receivable, net (1) $ 5,076 $ 71,542 $ (67,666) $ 8,952 (1) Additions to accounts receivable, net relate to amounts billed to Customers for product sales and deductions primarily relate to collection of receivables during the reporting period. The following table presents changes in our contract assets and liabilities during the year ended December 31, 2018: (In thousands) December 31, Additions Deductions December 31, Contract assets Accounts receivable, net (1) $ — $ 16,374 $ (11,298) $ 5,076

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2019
Revenue Recognition and Deferred Revenue [Abstract]
Collaboration and License Agreements	Collaboration and License Agreements Celgene Corporation To date, our revenue has primarily been generated from our collaboration agreements with Celgene, or collectively, the Collaboration Agreements. Celgene is a related party through ownership of our common stock. In April 2010, we entered into a discovery and development collaboration and license agreement focused on cancer metabolism, or the 2010 Agreement. The 2010 Agreement was amended in October 2011 and July 2014. In April 2015, we entered into a joint worldwide development and profit share collaboration and license agreement with Celgene, and our wholly owned subsidiary, Agios International Sarl, entered into a collaboration and license agreement with Celgene International II Sarl, or collectively, the AG-881 Agreements, to establish a worldwide collaboration focused on the development and commercialization of vorasidenib products. The AG-881 Agreements were terminated effective September 4, 2018. In May 2016, we entered into a master research and collaboration agreement with Celgene, or the 2016 Agreement. 2016 Agreement In May 2016, we entered into the 2016 Agreement focused on metabolic immuno-oncology, a developing field which aims to modulate the activity of relevant immune cells by targeting critical metabolic nodes, thereby enhancing the immune mediated anti-tumor response. In addition to new programs identified under the 2016 Agreement, both parties also agreed that all future development and commercialization of two remaining cancer metabolism programs discovered under the 2010 Agreement, including AG-270, will now be governed by the 2016 Agreement. During the research term of the 2016 Agreement, we plan to conduct research programs focused on discovering compounds that are active against metabolic targets in the immuno-oncology, or IO, field. The initial four one For each program under the 2016 Agreement, we may nominate compounds that meet specified criteria as development candidates and, in limited circumstances, Celgene may also nominate compounds as development candidates for each such program. Celgene may designate the applicable program for further development following any such nomination, after which we may conduct, at our expense, additional preclinical and clinical development for such program through the completion of an initial phase 1 dose escalation study. At the end of the research term, Celgene may designate for continued development up to three research programs for which development candidates have yet to be nominated, which are referred to as continuation programs. We may conduct further research and preclinical and clinical development activities on any continuation program, at our expense, through the completion of an initial phase 1 dose escalation study. We granted Celgene the right to obtain exclusive options for development and commercialization rights for each program that Celgene has designated for further development, and for each continuation program. Celgene may exercise each such option beginning on the designation of a development candidate for such program (or on the designation of such program as a continuation program) and ending on the earlier of: (i) the end of a specified period after we have furnished Celgene with specified information about the initial phase 1 dose escalation study for such program, or (ii) January 1, 2030. Research programs that have applications in the inflammation or autoimmune, or I&I, field that may result from the 2016 Agreement will also be subject to the exclusive options described above. We will retain rights to any program that Celgene does not designate for further development or as to which it does not exercise its option. Under the terms of the 2016 Agreement, following Celgene’s exercise of its option with respect to a program, the parties will enter into either a co-development and co-commercialization agreement if such program is in the IO field, or a license agreement if such program is in the I&I field. Under each co-development and co-commercialization agreement, the two parties will co-develop and co-commercialize licensed products worldwide. Either we or Celgene will lead development and commercialization of licensed products for the United States, and Celgene will lead development and commercialization of licensed products outside of the United States. Depending on the country, the parties will each have the right to provide a portion of field-based marketing activities. Under each license agreement, Celgene will have the sole right to develop and commercialize licensed products worldwide. Co-development and co-commercialization agreements Under each co-development and co-commercialization agreement entered into under the 2016 Agreement, the parties will split all post-option exercise worldwide development costs, subject to specified exceptions, as well as any profits from any net sales of, or commercialization losses related to, licensed products in the IO field. Celgene has the option to designate one program in the IO field as the 65/35 program, for which Celgene will be the lead party for the United States and will have a 65% profit or loss share. For programs in the IO field other than the 65/35 program, we and Celgene will alternate, on a program-by-program basis, being the lead party for the United States, with us having the right to be the lead party for the first such program, and each party will have a 50% profit or loss share. The lead party for the United States will book commercial sales of licensed products, if any, in the United States, and Celgene will book commercial sales of licensed products, if any, outside of the United States. License agreements Under each license agreement under the 2016 Agreement, Celgene will be responsible for all post-option exercise worldwide development and associated costs, subject to specified exceptions, as well as worldwide commercialization and associated costs, for licensed products in the I&I field. Financial terms Under the terms of the 2016 Agreement, we received an initial upfront payment in the amount of $200.0 million. The 2016 Agreement provides specified rights to extend the research term for up to two, or in specified cases, up to four, additional years by paying a $40.0 million per-year extension fee. Celgene will pay an $8.0 million designation fee for each program that Celgene designates for further development and for each continuation program. During the year ended December 31, 2017, we received $8.0 million from Celgene upon the designation of AG-270 as a development candidate. For each program as to which Celgene exercises its option to develop and commercialize, subject to antitrust clearance, Celgene will pay an option exercise fee of at least $30.0 million for any designated development program and at least $35.0 million for any continuation programs. In certain cases, Celgene may exercise its option to develop and commercialize two early-stage I&I programs, prior to Celgene designating the program for further development, by paying an option exercise fee of $10.0 million. We are eligible to receive the following milestone-based payments associated with the 2016 Agreement: Program Milestone Amount 65/35 program in IO field Specified clinical development event $25.0 million 65/35 program in IO field Specified regulatory milestone events Up to $183.8 million 50/50 program in IO field Specified clinical development event $20.0 million 50/50 program in IO field Specified regulatory milestone events Up to $148.8 million I&I field Specified clinical development event $25.0 million I&I field Specified regulatory milestone events Up to $236.3 million I&I field Specified commercial milestone events Up to $125.0 million Additionally, for each licensed program in the I&I field, we are eligible to receive royalties at tiered, low double-digit percentage rates on Celgene’s net sales, if any, of the applicable licensed products. Opt-out right Under the 2016 Agreement, we may elect to opt out of the cost and profit share under any co-development and co-commercialization agreement, subject to specified exceptions. Upon opting out, Celgene will have the sole right to develop, manufacture and commercialize the applicable licensed products throughout the world, at its cost, and we will undertake transitional activities reasonably necessary to transfer the development, manufacture and commercialization of such licensed products to Celgene, at our expense. Further, in lieu of the profit or loss sharing described above, we would be eligible to receive royalties at tiered, low double-digit percentage rates on Celgene’s net sales, if any, of the applicable licensed products. However, we would continue to be eligible to receive the developmental and regulatory milestone-based payments described above. Term The term of the 2016 Agreement commenced on May 17, 2016 and, if not terminated earlier, will expire upon the later of the last-to-expire of the research term and all option exercise periods, or, if an option is exercised by Celgene for one or more programs in the collaboration, upon the termination or expiration of the last-to-exist co-development and co-commercialization agreement or license agreement, as applicable, for any such program. Termination Subject to specified exceptions, Celgene may terminate the 2016 Agreement in its entirety for any reason by providing us with prior written notice if there are no active co-development and co-commercialization agreements or license agreements in place or on a program-by-program basis if there are no active co-development and co-commercialization agreements or license agreements in place for the terminated program(s). Either party may terminate the 2016 Agreement for the insolvency of the other party. On a program-by-program basis, prior to the exercise of an option, either party may terminate the 2016 Agreement either in its entirety or with respect to one or more programs on prior written notice to the other party in the case of an uncured material breach by the other party that frustrates the fundamental purpose of the 2016 Agreement. Following the exercise of an option for a program, either party may terminate the 2016 Agreement with respect to such program if such party terminates the co-development and co-commercialization agreement or license agreement for such program for an uncured material breach by the other party that frustrates the fundamental purpose of such agreement. Either party may terminate a co-development and co-commercialization agreement or a license agreement upon the bankruptcy or insolvency of the other party. Either party also has the right to terminate the co-development and co-commercialization agreement or license agreement if the other party or any of its affiliates challenges the validity, scope or enforceability of or otherwise opposes, any patent included within the intellectual property rights licensed to the other party under such agreement. Exclusivity While any of Celgene’s options remain available under the 2016 Agreement, subject to specified exceptions, we may not directly or indirectly develop, manufacture or commercialize, outside of the 2016 Agreement, any therapeutic modality in the IO or I&I field with specified activity against a metabolic target. During the term of each co-development and co-commercialization agreement and license agreement, subject to specified exceptions, neither we nor Celgene may directly or indirectly develop, manufacture or commercialize outside of such agreement any therapeutic modality in any field with specified activity against the metabolic target that is the focus of the program licensed under such agreement. Ivosidenib Letter Agreement On May 17, 2016, we entered into a letter agreement with Celgene regarding ivosidenib, or the Ivosidenib Letter Agreement. Under the Ivosidenib Letter Agreement, the parties agreed to terminate the 2010 Agreement, effective as of August 15, 2016, as to the program directed to the IDH1 target, for which ivosidenib is the lead development candidate. Under the 2010 Agreement, Celgene had held development and commercialization rights to the IDH1 program outside of the United States, and we held such rights inside the United States. As a result of the Ivosidenib Letter Agreement, we obtained global rights to ivosidenib and the IDH1 program. Neither party will have any further financial obligation, including royalties or milestone payments, to the other concerning ivosidenib or the IDH1 program. Under the terms of the Ivosidenib Letter Agreement, the parties also agreed to conduct specified transitional activities in connection with the termination. In addition, pursuant to the Ivosidenib Letter Agreement, the parties are released from their exclusivity obligations under the 2010 Agreement with respect to the IDH1 program. The Ivosidenib Letter Agreement does not affect the AG-881 Agreements, which were directed to both the IDH1 target and the IDH2 target, and were subsequently terminated in September 2018 as discussed below. Termination of AG-881 Agreements We and Celgene terminated the AG-881 Agreements, effective as of September 4, 2018. From and after September 4, 2018, we obtained sole global rights to vorasidenib. Neither we nor Celgene will have any further financial obligation under the AG-881 Agreements, including milestones, royalties or other payments, except that (a) Celgene is eligible to receive royalties from us at a low single-digit percentage rate on worldwide net sales of products containing vorasidenib and (b) we and Celgene agreed to split certain agreed-upon worldwide development costs for vorasidenib until December 31, 2018. In addition, for a specified period and subject to specified exceptions, Celgene and its affiliates are prohibited from developing, manufacturing or commercializing any product that inhibits IDH1 at specified levels of binding for any indication and we are prohibited from developing, manufacturing or commercializing vorasidenib in hematologic indications. 2010 Agreement The 2010 Agreement, which was entered into in April 2010, was amended in October 2011 and July 2014. The goal of the collaboration was to discover, develop and commercialize disease-altering therapies in oncology based on our cancer metabolism research platform. We initially led discovery, preclinical and early clinical development for all cancer metabolism programs under the collaboration. The discovery phase of the 2010 Agreement expired in April 2016. Upon agreement to terminate the 2010 Agreement, effective as of August 15, 2016, as to the program directed to the IDH1 target, for which ivosidenib is the lead development candidate, the sole program remaining under the 2010 Agreement is IDHIFA®, a co-commercialized licensed program for which Celgene leads and funds global development and commercialization activities. We have exercised our right to participate in a portion of commercialization activities in the United States for IDHIFA® in accordance with the applicable commercialization plan. On August 1, 2017, the FDA granted Celgene approval of IDHIFA® for the treatment of adult patients with R/R AML with an IDH2 mutation as detected by an FDA-approved test. Under the remaining terms of the 2010 Agreement, we are eligible to receive up to $80.0 million in potential milestone payments for the IDHIFA® program. The potential milestone payments are comprised of: (i) up to $55.0 million in milestone payments upon achievement of specified ex-U.S. regulatory milestone events, of which $35.0 million relates to the first regulatory approval in any of China, Japan or a major European country, and (ii) a $25.0 million milestone payment upon achievement of a specified commercial milestone event. Under the 2010 Agreement, we receive royalties at tiered, low-double digit to mid-teen percentage rates on net sales of IDHIFA®. Unless terminated earlier by either party, the term of the 2010 Agreement will continue until the expiration of all royalty terms with respect to IDHIFA®. Celgene may terminate this agreement for convenience in its entirety upon ninety days written notice to us. If either party is in material breach and fails to cure such breach within the specified cure period, the other party may terminate the 2010 Agreement in its entirety. Either party may terminate the agreement in the event of specified insolvency events involving the other party. Collaboration revenue Performance obligations identified Upon the adoption of ASC 606 on January 1, 2018, we applied the practical expedient that permits aggregating the effect of all contract modifications that occurred prior to January 1, 2018. No other practical expedients were used. Similar to the accounting under ASC 605-25, the 2016 Agreement was determined to be a modification of the 2010 Agreement and the AG-881 Agreements. In determining the appropriate amount of revenue to be recognized under ASC 606, we performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measured the transaction price, including the constraint on variable consideration; (iv) allocated the transaction price to the performance obligations; and (v) recognized revenue when (or as) we satisfied each performance obligation. The transaction price is calculated as the total amount of consideration to which the Company expects to be entitled to in exchange of transferring the promised goods and services to Celgene, and excludes any amounts of variable consideration that have been constrained (being contingency based development, regulatory and sales based milestones for which the Company cannot assert it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the milestone is subsequently resolved). The transaction price upon the adoption of ASC 606 was comprised of all consideration received to date under the agreements, as well as the estimated amount of research and development cost reimbursements that will be received under the agreement. The transaction price was subsequently allocated to the individual performance obligations based on their relative standalone selling prices. We developed assumptions that require judgment to determine the stand-alone selling price, or SSP, for each performance obligation identified in the contract. We use key assumptions to determine the SSP, which include forecast of revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. The satisfied and unsatisfied performance obligations at the time of the adoption of ASC 606, each of which are considered by us to be distinct within the context of the contract, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized were as follows: Performance SSP No. of Performance Recognition Fully satisfied at time of adoption Licenses (1) $ 86.7 million 4 Fully satisfied; recognized upon adoption of ASC 606 Research and development services (2) $ 350.7 million 10 Fully satisfied; recognized upon adoption of ASC 606 Partially satisfied at time of adoption Research and development services (2) $ 266.6 million 6 Proportionally as services are delivered over the performance period, expected to be through September 2023 (3) (1) The SSP was developed by probability weighting multiple cash flow scenarios using the income approach. Our management estimates within the models include the expected, probability-weighted net profits from estimated future sales, an estimate of the direct cost incurred to generate future cash flows, a discount rate and other business forecast factors. There are significant judgments and estimates inherent in the determination of the SSP of these performance obligations. These judgments and estimates include assumptions regarding future operating performance, the timelines of the clinical trials and regulatory approvals, and other factors. If different reasonable assumptions are utilized, the SSP and revenue recognized would vary. (2) The SSP was developed using our management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider and using internal full time equivalent costs to support the development services. (3) We determined that recognizing revenue on a proportional basis using the ratio of effort incurred to date compared to the total estimated effort required to complete the performance obligation best depicts the satisfaction of our obligations under the Collaboration Agreements. Remaining performance obligations As of December 31, 2019, the remaining performance obligations under the Celgene agreements, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized are as follows: Performance SSP No. of Remaining Performance Recognition Research and development services $175.4 million 2 Proportionally as services are delivered over the performance period A significant portion of revenue generated from our collaboration agreements with Celgene relates to the provision of research and development services whereby revenue is recognized under an input method using the ratio of effort incurred to date compared to the total estimated effort required to complete the performance obligation. The calculation of the total estimated effort includes the total amount of forecasted costs associated with the completion of discovery, pre-clinical or clinical trials, as well as the assumed timing of these activities and estimated patient populations. Such cost estimates include forecasted direct labor and material costs, subcontractor costs, and external contract research organization costs. As of December 31, 2019, the aggregate amount of the transaction price allocated to performance obligations that are partially unsatisfied was $70.0 million. This amount is expected to be recognized as performance obligations are satisfied through September 2023. Revenue recognition During the years ended December 31, we recognized the following collaboration revenue: (In thousands) 2019 2018 2017 (1) Services performed that were considered performance obligations upon the adoption of ASC 606 Licenses $ — $ 15,000 $ — On-going research and development services 35,954 40,575 37,953 Committee participation — — 167 Services performed that were not considered performance obligations as of the adoption of ASC 606 Development activities — 1,342 — Commercialization Activities 3,303 3,744 2,954 Total collaboration revenue - related party 39,257 60,661 41,074 (1) Amounts prior to 2018 do not reflect the impact of the adoption of Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606), in the first quarter of 2018. See Note 2. Summary of Significant Accounting Policies for additional information. We also recognized certain consideration received from Celgene as a reduction of research and development expenses of zero for 2019 and 2018, respectively and $7.8 million for 2017. The following table presents changes in our contract assets and liabilities during the year ended December 31, 2019: (In thousands) December 31, Additions Deductions December 31, Contract assets Collaboration receivable – related party (1) $ 2,462 $ 8,253 $ (9,176) $ 1,539 Royalty receivable – related party (2) 2,234 10,542 (9,876) 2,900 Contract liabilities Deferred revenue – related party, current and non-current portions (3) 92,519 4,948 (35,954) 61,513 (1) Additions to collaboration receivables - related party relate to amounts billed to Celgene for reimbursable costs incurred by us during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. The following table presents changes in our contract assets and liabilities during the year ended December 31, 2018: (In thousands) December 31, Additions Deductions December 31, Contract assets Collaboration receivable – related party (1) $ 2,448 $ 28,695 $ (28,681) $ 2,462 Royalty receivable – related party (2) 1,222 7,087 (6,075) 2,234 Contract liabilities Deferred revenue – related party, current and non-current portions (3) 163,640 9,237 (80,358) 92,519 (1) Additions to collaboration receivables - related party relate to amounts billed to Celgene for reimbursable costs incurred by us during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. (2) Additions to receivables relate to amounts billed to Celgene during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. (3) Additions to deferred revenue relate to consideration from Celgene during the reporting period. Deductions relate to deferred revenue recognized as revenue during the reporting period and the cumulative catch-up adjustment recognized upon adoption of ASC 606 on January 1, 2018. During the years ended December 31, 2019, 2018 and 2017, we recognized the following as revenue due to changes in the contract liability balances: (In thousands) 2019 2018 2017 (1) Amounts included in the contract liability at the beginning of the period $ 31,605 $ 37,590 $ — Performance obligations satisfied in previous periods — 469 — (1) Amounts prior to 2018 do not reflect the impact of the adoption of Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606), in the first quarter of 2018. See Note 2. Summary of Significant Accounting Policies for additional information. Royalty revenue During the years ended December 31, 2019, 2018 and 2017, we recognized the following as royalty revenue: (In thousands) 2019 2018 2017 Royalty revenue – related party $ 10,542 $ 7,215 $ 1,937 As the underlying performance obligation, or delivery of the enasidenib license, had been satisfied as of June 2014, royalty revenue is recognized as the related sales occur. Milestone revenue (variable consideration) At each reporting period we evaluate whether milestones are considered probable of being reached and, to the extent that a significant reversal would not occur in future periods, estimate the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within our control, such as regulatory approvals, are not considered probable of being achieved and are excluded from the transaction price until those approvals are received. During the year ended December 31, 2019, we did not receive any milestone payments related to our Celgene Agreements, and all variable consideration relating to the remaining development, regulatory and sales-based milestones that can be earned under the terms of the agreement remain fully constrained. During the year ended December 31, 2018, Celgene submitted an MAA to the EMA for IDHIFA® for IDH2 mutant-positive R/R AML. As a result of the filing, we determined that a $15.0 million milestone payment for the filing of a first new drug application equivalent in an ex-U.S. country was considered probable of being reached and that a significant reversal of revenue would not occur in future periods. As the underlying performance obligation, or delivery of the license to IDHIFA®, had been satisfied as of June 2014, the milestone payment was recognized in full as collaboration revenue. The next potential milestone expected to be achieved under our collaboration agreements with Celgene is the first regulatory approval in any of China, Japan or a major European country. Achievement of this event will result in a milestone payment of $35.0 million under the 2010 Agreement. CStone Pharmaceuticals In June 2018, we entered into an exclusive license agreement with CStone, or the CStone Agreement, to grant CStone specified intellectual property licenses to enable CStone to develop and commercialize certain products containing ivosidenib in mainland China, Hong Kong, Macau, and Taiwan. We retain development and commercialization rights for the rest of the world. Pursuant to the CStone Agreement, CStone will initially be responsible for the development and commercialization of ivosidenib in AML, cholangiocarcinoma, and, at our discretion, brain cancer indications. Under the terms of the CStone Agreement, we received an initial upfront payment in the amount of $12.0 million and are entitled to receive up to an additional $407.0 million in milestone payments upon the achievement of certain development, regulatory and sales milestone events. Approximately one third of the milestone payments are related to development and regulatory milestones, half of which are related to ivosidenib in AML and cholangiocarcinoma and the other half are related to brain cancer indications, including glioma. We will also be entitled to receive tiered royalties, ranging from 15% to 19% percent, on annual net sales, if any, of ivosidenib. CStone is responsible for all costs it incurs in developing, obtaining regulatory approval of, and commercializing ivosidenib in mainland China, Hong Kong, Macau, and Taiwan, as well as certain costs incurred by us. During the term of the CStone Agreement, each party and its affiliates are prohibited from developing or commercializing any other compound or product that inhibits IDH1 mutations at specified levels of binding, in the case of CStone, anywhere in the world, and in our case, in mainland China, Hong Kong, Macau, and Taiwan. Termination Unless earlier terminated, the CStone Agreement will expire upon the expiration of the last royalty term for the last licensed product within the scope of the CStone Agreement. At any time after CStone has obtained regulatory approval in mainland China in R/R AML and the last patient has been enrolled in a specified clinical trial (or, if earlier, at any time that CStone acquires or is acquired by an entity with a competing or restricted product), CStone may terminate the CStone Agreement in its entirety by providing us with prior written notice. Either party may, subject to specified cure periods, terminate the CStone Agreement in the event of the other party’s uncured material breach. Either party may terminate the CStone Agreement under specified circumstances relating to the other party’s insolvency. We have the right to terminate the CStone Agreement immediately if CStone or its affiliates or sublicensees or subcontractors challenges the validity, patentability, or enforceability of certain patent rights that relate to ivosidenib and are owned by or licensed to us or our affiliates. Collaboration revenue Performance obligations identified We developed assumptions that require judgment to determine the SSP for each performance obligation identified in the contract. We use key assumptions to determine the SSP, which include forecast of revenues, development timelines, reimbursement rates, discount rates and probabilities of technical and regulatory success. The satisfied and unsatisfied performance obligations, each of which are considered by us to be distinct within the context of the contract, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized are as follows: Performance SSP No. of Performance Obligation(s) Recognition Licenses (1) $ 16.4 million 1 Fully satisfied; recognized upon delivery of license Other services (2) $ 1.7 million 1 As services are delivered, expected to be through September 2021 (1) The SSP was developed by probability weighting multiple cash flow scenarios using the income approach. Our management estimates within the models include the expected, probability-weighted net profits from estimated future sales, an estimate of the direct costs incurred to generate future cash flows, a discount rate and other business forecast factors. There are significant judgments and estimates inherent in the determination of the SSP of this performance obligation. These judgments and estimates include assumptions regarding future operating performance, the timelines of the clinical trials and regulatory approvals, and other factors. If different reasonable assumptions are utilized, the SSP and revenue recognized would vary. (2) The SSP was developed using our management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider. As of December 31, 2019, the

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Common Stock	Common StockWe are authorized to issue 125,000,000 shares of our common stock. Holders of common stock are entitled to one vote per share. Additionally, holders of common stock are entitled to receive dividends, if and when declared by our board of directors, and to share ratably in our assets legally available for distribution to our shareholders in the event of liquidation.

Share-Based Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Share-Based Payments	Share-Based Payments Stock incentive plans In June 2013, our Board of Directors adopted and, in July 2013 our stockholders approved, the 2013 Stock Incentive Plan, or the 2013 Plan. The 2013 Plan became effective upon the closing of our initial public offering and provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units, or RSUs, performance-based stock units, or PSUs, and other stock-based awards to employees, non-employees and non-employee directors. Following the adoption of the 2013 Plan, we granted no further stock options or other awards under the 2007 Stock Incentive Plan, or the 2007 Plan. Any options or awards outstanding under the 2007 Plan at the time of adoption of the 2013 Plan remain outstanding and effective. As of December 31, 2019, the total number of shares reserved under the 2007 Plan and the 2013 Plan are 9,356,754, and we had 2,127,478 shares available for future issuance under the 2013 Plan. The 2013 Plan provides for an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2014 and continuing until the expiration of the 2013 Plan, equal to the lesser of (i) 2,000,000 shares of common stock, (ii) 4% of the outstanding shares of common stock on such date or (iii) an amount determined by our Board of Directors. On January 1, 2020, the annual increase for the 2013 Plan resulted in an additional 2,000,000 shares authorized for issuance. Stock options The following table summarizes the stock option activity of all stock incentive plans for the year ended December 31, 2019: Number of Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 5,416,069 $ 60.10 7.30 $ 27,941 Granted 1,772,485 53.79 Exercised (283,200) 32.69 Forfeited/Expired (703,869) 68.36 Outstanding at December 31, 2019 6,201,485 $ 58.61 7.09 $ 28,528 Exercisable at December 31, 2019 3,541,821 $ 58.90 5.89 $ 25,258 Vested and expected to vest at December 31, 2019 6,201,485 $ 58.61 7.09 $ 28,528 The weighted-average grant date fair value of options granted was $36.44, $53.22 and $35.24 during the years ended December 31, 2019, 2018 and 2017, respectively. The total intrinsic value of options exercised was $6.4 million, $65.1 million and $31.5 million during the years ended December 31, 2019, 2018 and 2017, respectively. At December 31, 2019, the total unrecognized compensation expense related to unvested stock option awards was $92.3 million, which we expect to recognize over a weighted-average period of approximately 2.54 years. Restricted stock units Upon vesting, each RSU entitles the holder to receive a specified number of shares of our common stock. The following table presents RSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 532,144 $ 75.45 Granted 505,362 54.44 Vested (166,740) 69.58 Forfeited (103,813) 71.34 Unvested shares at December 31, 2019 766,953 $ 63.44 As of December 31, 2019, there was approximately $28.1 million of total unrecognized compensation expense related to RSUs, which we expect to be recognized over a weighted-average period of 1.71 years. Performance-based stock units At the achievement of the performance-based and service-based vesting criteria, each PSU entitles the holder to receive a specified number of shares of our common stock. The following table presents PSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 169,031 $ 52.67 Granted 216,143 55.43 Vested (167,031) 52.36 Forfeited — — Unvested shares at December 31, 2019 218,143 $ 55.64 Stock-based compensation expense associated with these PSUs is recognized if the underlying performance condition is considered probable of achievement using our management’s best estimates. As of December 31, 2019, there was approximately $1.5 million of total unrecognized compensation expense related to PSUs with performance-based vesting criteria that are considered probable of achievement, which we expect to recognize over a weighted-average period of 0.33 years, and $8.0 million of total unrecognized compensation expense related to PSUs with performance-based vesting criteria that are considered not probable of achievement. Market-based stock units The Company has issued certain equity awards that contain market based vesting conditions, in which shares of stock are earned at vesting based on stock price performance. The fair value of MSUs are estimated using a Monte Carlo simulation model. Assumptions and estimates utilized in the model include the risk-free interest rate, dividend yield, expected stock volatility and the estimated period to achievement of the market condition. The following table presents MSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 — $ — Granted 42,695 41.50 Unvested shares at December 31, 2019 42,695 $ 41.50 As of December 31, 2019, there was approximately $0.8 million of total unrecognized compensation expense related to MSUs, which we expect to recognize over the remaining derived service period of 0.72 years. 2013 Employee Stock Purchase Plan In June 2013, our Board of Directors adopted, and in July 2013 our stockholders approved, the 2013 Employee Stock Purchase Plan, or the 2013 ESPP. We issued 77,981 shares and 53,255 shares during the years ended December 31, 2019 and 2018, respectively, under the 2013 ESPP. The 2013 ESPP provides participating employees with the opportunity to purchase up to an aggregate of 327,272 shares of our common stock. As of December 31, 2019, we had 82,555 shares available for future issuance under the 2013 ESPP. On January 1, 2020, the annual increase for the 2013 ESPP resulted in an additional 509,091 shares authorized for issuance. Stock-based compensation expense During the years ended December 31, 2019, 2018 and 2017, we recorded stock-based compensation expense for employee and non-employee stock options, RSUs, PSUs, ESPP shares and other stock-based awards. Stock-based compensation expense by award type included within the consolidated statements of operations is as follows: (In thousands) 2019 2018 2017 Stock options $ 48,219 $ 51,460 $ 43,997 Restricted stock units 19,079 12,032 2,858 Performance-based stock units 2,647 8,717 — Employee Stock Purchase Plan 1,437 1,148 954 Other stock awards 991 — — Total stock-based compensation expense $ 72,373 $ 73,357 $ 47,809 Expenses related to equity-based awards were allocated as follows in the consolidated statements of operations: (In thousands) 2019 2018 2017 Research and development expense $ 39,029 $ 41,982 $ 30,807 Selling, general and administrative expense 33,344 31,375 17,002 Total stock-based compensation expense $ 72,373 $ 73,357 $ 47,809 No related tax benefits were recognized for the years ended December 31, 2019, 2018 and 2017. The fair value of each stock option granted to employees and nonemployees is estimated on the date of grant using the Black-Scholes option-pricing model. The following table summarizes the weighted average assumptions used in calculating the grant date fair value of the awards: 2019 2018 2017 Risk-free interest rate 2.32 % 2.71 % 2.05 % Expected dividend yield — — — Expected term (in years) 6.06 6.06 6.05 Expected volatility 76.19 % 76.62 % 77.73 % Expected term We use the “simplified method” as prescribed by the Securities and Exchange Commission Staff Accounting Bulletin No. 107, Share Based Payments , to estimate the expected term of stock option grants. Under this approach, the weighted-average expected life is presumed to be the average of the contractual term of ten years and the weighted-average vesting term of the stock options, taking into consideration multiple vesting tranches. We utilize this method due to lack of historical data and the plain-vanilla nature of our share-based awards. Volatility We use a weighted-average of expected volatility based on the volatilities of a representative group of publicly traded biopharmaceutical companies, including ourselves. The expected volatility has been determined using a weighted-average of the historical volatilities of the representative group of companies for a period equal to the expected term of the option grant. Risk-free rate The risk-free rate is based on the yield curve of U.S. Treasury securities with periods commensurate with the expected term of the options being valued. Dividends We have never paid, and do not anticipate paying, any cash dividends in the foreseeable future, and, therefore, use an expected dividend yield of zero in the option-pricing model. Forfeitures We account for forfeitures as they occur and, therefore, do not estimate forfeitures.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The domestic and foreign components of loss before income taxes are as follows: (In thousands) 2019 2018 2017 Domestic $ (432,535) $ (311,159) $ (290,423) Foreign 21,063 (34,869) (24,247) Total $ (411,472) $ (346,028) $ (314,670) We did not have any provision for income taxes for the years ended December 31, 2019, 2018 and 2017. A reconciliation of the expected income tax benefit (expense) computed using the federal statutory income tax rate to our effective income tax rate is as follows for the years ended December 31, 2019, 2018 and 2017: 2019 2018 2017 Income tax benefit computed at federal statutory tax rate 21.0 % 21.0 % 35.0 % State taxes, net of federal benefit 2.8 % 0.8 % 4.0 % Change in valuation allowance (27.2) % (28.4) % (19.4) % General business credits and other credits 5.0 % 5.7 % 10.4 % Permanent differences and other adjustments (1.3) % (0.7) % — % Incentive stock options (0.6) % 2.2 % 0.3 % Foreign rate differential 0.3 % (0.6) % (1.6) % Impact of federal rate change — % — % (28.7) % Total — % — % — % Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets and liabilities for the years ended December 31, 2019 and 2018 are as follows: (In thousands) 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 294,614 $ 211,563 Deferred revenue 14,372 21,956 Tax credit carryforwards 141,219 120,605 Purchased intangible assets 14,479 3,204 Stock-based compensation 30,861 27,636 Operating lease liability 27,173 — Deferred rent — 4,458 Non-deductible accruals and reserves, including inventory 4,729 4,900 Total deferred tax assets 527,447 394,322 Depreciation and amortization (2,613) (3,569) Operating lease right of use asset (22,625) — Less: valuation allowance (502,209) (390,753) Net deferred taxes $ — $ — In December 2017, the Tax Cuts and Jobs Act, or TCJA, was signed into law. Among other things, the TCJA permanently lowers the corporate federal income tax rate to 21% from the existing maximum rate of 35%, effective for tax years including or commencing January 1, 2018. As a result of the reduction of the corporate federal income tax rate to 21%, U.S. GAAP requires companies to revalue their deferred tax assets and deferred tax liabilities as of the date of enactment, with the resulting tax effects accounted for in the reporting period of enactment. This revaluation resulted in a provision of $90.0 million to income tax expense in continuing operations and a corresponding reduction in the valuation allowance. As a result, there was no impact on our consolidated statements of operations from the reduction in tax rate. The other provisions of the TCJA did not have a material impact on the consolidated financial statements. As of December 31, 2019, we had net operating loss carryforwards, or NOLs, available to reduce federal, state and foreign income taxes of approximately $1,133.0 million, $877.9 million and $61.9 million, respectively. If not utilized, these NOLs begin to expire in 2033 (for pre-2018 NOLs), 2032 and 2023, respectively. Approximately $669.6 million of federal NOLs can be carried forward indefinitely. At December 31, 2019, we also had available research and development tax credits for federal and state income tax purposes of approximately $31.2 million and $15.0 million, respectively. If not utilized, the credits begin to expire in 2027 and 2020 for federal and state income tax purposes, respectively. We engaged in clinical testing activities and incurred expenses that qualify for the federal orphan drug tax credit. At December 31, 2019, we had available orphan drug tax credits for federal purposes only of approximately $98.1 million. If not utilized, the orphan drug credits begin to expire in 2035. As provided by Section 382 of the Internal Revenue Code of 1986, or Section 382, and similar state provisions, utilization of NOLs and tax credit carryforwards may be subject to substantial annual limitations due to ownership change limitations that have previously occurred or that could occur in the future. Ownership changes may limit the amount of NOLs and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. In general, an ownership change, as defined by Section 382, results from transactions that increase the ownership of five percent stockholders in the stock of a corporation by more than 50 percent in the aggregate over a three As required by ASC 740, we have evaluated the positive and negative evidence bearing upon the realizability of our deferred tax assets. Based on the weight of available evidence, both positive and negative, we recorded a valuation allowance of $502.2 million and $390.8 million as of December 31, 2019 and December 31, 2018, respectively, because we have determined that it is more likely than not that these assets will not be fully realized. The valuation allowance increased by $111.4 million and $88.8 million for the years ended December 31, 2019 and, 2018, respectively. In December 2019, the FASB issued Accounting Standards Update No. 2019-12 – Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes, as part of its initiative to reduce complexity in the accounting standards. The amendments in ASU 2019-12 eliminate certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. The amendments in ASU 2019-12 are effective for the fiscal years beginning after December 15, 2020. Early adoption is permitted, including adoption in any interim period. The Company has early adopted this amendment as of January 1, 2019. There was no material impact to the Company’s consolidated financial position, results of operation, or cash flows. We apply the accounting guidance in ASC 740 related to accounting for uncertainty in income taxes. Our reserves related to taxes are based on a determination of whether, and how much of, a tax benefit taken by us in our tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit. The following table presents our unrecognized tax benefits activity for the years ended December 31, 2019 and 2018: (In thousands) 2019 2018 Unrecognized tax benefits at the beginning of the year $ 14,288 $ 11,263 Gross increases - current period tax positions 3,172 3,025 Unrecognized tax benefits at the end of the year $ 17,460 $ 14,288 The uncertain tax position does not impact our effective income tax rate due to the full valuation allowance. We are subject to taxation in the United States and Switzerland. The statute of limitations for assessment by the IRS and state tax authorities is open for tax years ending December 31, 2019, 2018, 2017, and 2016, although carryforward attributes that were generated for tax years prior to 2016 may still be adjusted upon examination by the IRS or state tax authorities if they either have been, or will be, used in a future period. The statute of limitations for assessment in Switzerland remains open for tax year ending December 31, 2019, 2018, 2017, and 2016. There are currently no federal, state or foreign audits in progress.

Defined Contribution Benefit Pl

Defined Contribution Benefit Plan	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Defined Contribution Benefit Plan	Defined Contribution Benefit PlanWe sponsor a 401(k) retirement plan, in which substantially all of our full-time employees are eligible to participate. Participants may contribute a percentage of their annual compensation to this plan, subject to statutory limitations. We will make matching contributions equal to 100% of the employee’s contributions, subject to a maximum of 4% of eligible compensation.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting the weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury stock method. For purposes of the dilutive net loss per share calculation, stock options, RSUs, PSUs and MSUs for which the performance and market vesting conditions, respectively, have been deemed probable, and 2013 ESPP shares are considered to be common stock equivalents, while PSUs and MSUs with performance and market vesting conditions, respectively, that were not deemed probable as of December 31, 2019 are not considered to be common stock equivalents. Since we had a net loss for all periods presented, the effect of all potentially dilutive securities is anti-dilutive. Accordingly, basic and diluted net loss per share was the same for the years ended December 31, 2019, 2018 and 2017. The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Years ended December 31, 2019 2018 2017 Stock options 6,201,485 5,416,069 5,577,562 Restricted stock units 766,953 532,144 125,584 Performance-based stock units 72,046 169,031 — Employee Stock Purchase Plan shares 49,418 32,304 22,062 Total 7,089,902 6,149,548 5,725,208

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following table contains quarterly financial information for 2019 and 2018: 2019 (in thousands, except per share data) First Second Third Fourth Total revenue $ 30,227 $ 26,221 $ 26,024 $ 35,440 Loss from operations (97,483) (113,861) (109,060) (105,929) Net loss (93,078) (109,871) (106,173) (102,350) Net loss per share – basic and diluted (1.59) (1.87) (1.81) (1.60) 2018 (in thousands, except per share data) First Second Third Fourth Total revenue $ 8,762 $ 40,414 $ 15,198 $ 30,013 Loss from operations (94,012) (72,949) (99,162) (96,356) Net loss (90,825) (68,745) (94,664) (91,794) Net loss per share – basic and diluted (1.63) (1.19) (1.63) (1.58)

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Principles of consolidation	Principles of consolidation The consolidated financial statements include our accounts and the accounts of our wholly owned subsidiaries, Agios Securities Corporation, Agios International Sarl, Agios Germany GmbH, Agios Netherlands B.V., and Agios Limited. All intercompany transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles, or U.S. GAAP.
Use of estimates	Use of estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances. Actual results could differ from those estimates.
Cash and cash equivalents	Cash and cash equivalents We consider highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash equivalents are stated at fair value.
Marketable securities	Marketable securities Marketable securities at December 31, 2019 and 2018 consisted of investments in certificates of deposit, U.S. Treasuries, government securities and corporate debt securities. We determine the appropriate classification of the securities at the time they are acquired and evaluate the appropriateness of such classifications at each balance sheet date. We classify our marketable securities as available-for-sale pursuant to Accounting Standards Codification, or ASC, 320, Investments – Debt and Equity Securities . Marketable securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive loss in stockholders’ equity and a component of total comprehensive loss in the consolidated statements of comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. At December 31, 2019 and 2018, we held both current and non-current investments. Investments classified as current have maturities of less than one year. Investments classified as non-current are those that: (i) have a maturity of one We review marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if we experience a credit loss, have the intent to sell the marketable security, or if it is more likely than not that we will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with our investment policy, the severity and the duration of the impairment, and changes in value subsequent to the end of the period.
Fair value measurements	Fair value measurements We record cash equivalents and marketable securities at fair value. ASC 820, Fair Value Measurements and Disclosures , establishes a fair value hierarchy for those instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and our own assumptions (unobservable inputs). The hierarchy consists of three levels: Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities. Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3 – Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. Our financial assets, which include cash equivalents and marketable securities, have been initially valued at the transaction price, and subsequently revalued at the end of each reporting period, utilizing third-party pricing services or other observable market data. The pricing services utilize industry standard valuation models, including both income and market based approaches, and observable market inputs to determine value. After completing our validation procedures, we did not adjust or override any fair value measurements provided by the pricing services as of December 31, 2019 or 2018. Fair value information for these assets, including their classification in the fair value hierarchy is included in Note 3. Fair Value Measurements . There have been no changes to the valuation methods during the years ended December 31, 2019 and 2018. We evaluate transfers between levels at the end of each reporting period. The carrying amounts of collaboration receivable – related party, collaboration receivable – other, royalty receivable – related party, accounts receivable, prepaid expenses and other current assets, accounts payable, and accrued expenses approximate their fair values due to their short-term maturities.
Accounts receivable, net	Accounts receivable, net Our trade accounts receivable arise from product sales and represent amounts due from specialty distributors and specialty pharmacy providers in the U.S. We monitor the financial performance and creditworthiness of our customers so that we can properly assess and respond to changes in their credit profile. We reserve against these receivables for estimated losses that may arise from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve.
Concentrations of credit risk	Concentrations of credit risk Financial instruments which potentially subject us to credit risk consist primarily of cash, cash equivalents, and marketable securities. We hold these investments in highly rated financial institutions, and, by policy, limit the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. We have not experienced any credit losses in such accounts and do not believe we are exposed to any significant credit risk on these funds. We have no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts, or other hedging arrangements. We are also subject to credit risk on our receivables, including trade receivables from our customers and collaboration and royalty receivables from Celgene and CStone Pharmaceuticals, or CStone. Concentrations of credit risk with respect to receivables, which are typically unsecured, are somewhat mitigated due to the number of customers using our products. Our trade receivables arise from product sales in the U.S. and have standard payment terms that generally require payment within 30 to 60 days. We have evaluated the creditworthiness of our customers, including Celgene, and determined them to be creditworthy. To date we have not experienced any losses with respect to our receivables.
Inventory	Inventory Inventory is stated at the lower of cost or estimated net realizable value on a first-in, first-out basis. Prior to the regulatory approval of our product candidates, we incur expenses for the manufacture of drug product that could potentially be available to support the commercial launch of those products. Until the date at which regulatory approval has been received or is otherwise considered probable, we record all such costs as research and development expenses. Upon approval of our wholly owned product, TIBSOVO®, by the FDA on July 20, 2018 for the treatment of adult patients with R/R AML with susceptible IDH1 mutation as detected by an FDA-approved test, we began to capitalize inventories of TIBSOVO®. We perform an assessment of the recoverability of capitalized inventory during each reporting period and write down any excess and obsolete inventory to its estimated net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales in the consolidated statements of operations. The determination of whether inventory costs will be realizable requires the use of estimates by management. If
Property and equipment	Property and equipment Property and equipment consist of laboratory equipment, computer equipment and software, leasehold improvements, furniture and fixtures, and office equipment. Costs of major additions and betterment are capitalized; maintenance and repairs, which do not improve or extend the life of the respective assets, are charged to expense as incurred. Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and the resulting gain or loss is recognized. Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets: Years Laboratory equipment 5 Computer equipment and software 3 Furniture and fixtures 5 Office equipment 5 Leasehold improvements are amortized over the lesser of the remaining lease term or the estimated useful life of the improvement.
Impairment of long-lived assets	Impairment of long-lived assets We periodically evaluate our long-lived assets for potential impairment in accordance with ASC 360, Property, Plant and Equipment . Potential impairment is assessed when there is evidence that events or changes in circumstances indicate that the carrying amount of an asset may not be recovered. Recoverability of these assets is assessed based on the undiscounted expected future cash flows from the assets, considering a number of factors, including past operating results, budgets and economic projections, market trends and product development cycles. If impairments are identified, assets are written down to their estimated fair value. We did not recognize any impairment charges through December 31, 2019.
Leases	Leases We determine if an arrangement is a lease at inception. An arrangement is determined to contain a lease if the contract conveys the right to control the use of an identified property or equipment for a period of time in exchange for consideration. If we can benefit from the various underlying assets of a lease on their own or together with other resources that are readily available, or if the various underlying assets are neither highly dependent on nor highly interrelated with other underlying assets in the arrangement, they are considered to be a separate lease component. In the event multiple underlying assets are identified, the lease consideration is allocated to the various components based on each of the component’s relative fair value. Operating lease assets represent our right to use an underlying asset for the lease term and operating lease liabilities represent our obligation to make lease payments arising from the leasing arrangement. Operating lease assets and operating lease liabilities are recognized at commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, in determining the operating lease liabilities, we use an estimate of our incremental borrowing rate. The incremental borrowing rate is determined using two alternative credit scoring models to estimate our credit rating, adjusted for collateralization. The calculation of the operating lease assets includes any lease payments made and excludes any lease incentives. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. For operating leases, we record operating lease assets and lease liabilities in our consolidated balance sheets. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Short-term leases, or leases that have a lease term of 12 months or less at commencement date, are excluded from this treatment and are recognized on a straight-line basis over the term of the lease. We have not entered into any material short-term leases or financing leases as of December 31, 2019.
Revenue from contracts with customers	Revenue from contracts with customers On January 1, 2018 we adopted ASC 606, Revenue from Contracts with Customers , under the modified retrospective method. Prior to January 1, 2018 we accounted for the consideration received under the Collaboration Agreements under ASC 605-25, Multiple Element Arrangements. In adopting ASC 606, we applied the practical expedient that permits aggregating the effect of all contract modifications that occurred prior to January 1, 2018. No other practical expedients were used. Similar to the accounting under ASC 605-25, the 2016 Agreement was determined to be a modification of the 2010 Agreement and the AG-881 Agreements with Celgene. Revenue is recognized when the customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that we determined to be within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract and determine those that are performance obligations, and assess whether each promised good or service is distinct. We will then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product revenue We generate product revenue from sales of TIBSOVO® to a limited number of specialty distributors and specialty pharmacy providers in the U.S., or collectively, the Customers. The Customers subsequently resell TIBSOVO® to pharmacies or dispense directly to patients. In addition to distribution agreements with Customers, we enter into arrangements with healthcare providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts with respect to the purchase of TIBSOVO®. The performance obligation related to the sale of TIBSOVO® is satisfied and revenue is recognized when the Customer obtains control of the product, which occurs at a point in time, typically upon delivery to the Customer. Revenues from product sales are recorded at the net sales price, or transaction price, which includes estimates of variable consideration for which reserves are established and result from contractual adjustments, government rebates, returns and other allowances that are offered within the contracts with our Customers, healthcare providers, payors and other indirect customers relating to the sale of our products. Contractual adjustments. We generally provide Customers with discounts, including prompt pay discounts, and allowances that are explicitly stated in the contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. Chargebacks and discounts represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from us. Customers charge us for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are estimated using the expected value method, based upon a range of possible outcomes that are probability-weighted for the estimated channel mix and are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue. Government rebates. Government rebates consist of Medicare, TriCare, and Medicaid rebates, which we estimate using the expected value method, based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue. For Medicare, we also estimate the number of patients in the prescription drug coverage gap for whom we will owe an additional liability under the Medicare Part D program. Returns. We estimate the amount of product sales that may be returned by Customers and record this estimate as a reduction of revenue in the period the related product revenue is recognized. We currently estimate product return liabilities using the expected value method, based on available industry data, including our visibility into the inventory remaining in the distribution channel. Collaboration revenue We apply the provisions of ASC 808, Collaborative Arrangements, when accounting for our collaboration agreements. We evaluate the presentation of amounts due from our collaborative partners associated with activities in the collaborative arrangement based on the nature of each activity. For transactions with customers, we have reported revenues and costs in accordance with ASC 606, Revenue from Contracts with Customers , ASC 606-10-55-36 through 55-40, Principal versus Agent Considerations . We recognize revenue when the customer obtains control of promised goods or services, in an amount that reflects the consideration that we expect to receive in exchange for those goods or services. To determine revenue recognition for arrangements that have been determined to be within the scope of ASC 606, we perform the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract based on the relative standalone selling prices of the goods or services provided; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) we satisfy a performance obligation. We only apply the five-step model to contracts when it is probable that we will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. Once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract and determine those that are performance obligations, and assess whether each promised good or service is distinct. We will then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The transaction price for each collaboration agreement is determined based on the amount of consideration we expect to be entitled to for satisfying all performance obligations within the agreement. Significant judgment may be required in determining the amount of variable consideration to be included in the transaction price. We use the expected value methods to determine variable consideration and will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. As part of the initial accounting for these arrangements, we must develop assumptions that require judgment to determine the standalone selling price, or SSP, for each performance obligation identified in the contract. We use these key assumptions to determine the SSP, which include forecast of revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success. We recognize the transaction price allocated to upfront license payments as revenue upon delivery of the license to the customer and resulting ability of the customer to use and benefit from the license, if the license is determined to be distinct from the other performance obligations identified in the contract. If the license is considered to not be distinct from other performance obligations, we exercise judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied (i) at a point in time, but only for licenses determined to be distinct from other performance obligations in the contract, or (ii) over time; and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from license payments. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. A significant portion of revenue generated from our collaboration agreements with Celgene relates to the provision of research and development services whereby revenue is recognized under an input method using the ratio of effort incurred to date compared to the total estimated effort required to complete the performance obligation. The calculation of the total estimated effort includes the total amount of forecasted costs associated with the completion of discovery, pre-clinical or clinical trials, as well as the assumed timing of these activities and estimated patient populations. Such cost estimates include forecasted direct labor and material costs, subcontractor costs, and external contract research organization, or CRO, costs. Milestone revenue Many of our collaboration agreements also entitle us to additional payments upon the achievement of performance-based milestones. These milestones are generally categorized into three types: development milestones, which are generally based on the initiation of clinical trials; regulatory milestones, which are generally based on the submission, filing or approval of regulatory applications such as a new drug application, or NDA, in the U.S.; and sales-based milestones, which are generally based on meeting specific thresholds of sales in certain geographic areas during a specified period. Upfront and ongoing development milestones per our collaboration agreements are not subject to refund if the development activities are not successful. For each collaboration that includes development milestone payments, we evaluate whether it is probable that the consideration associated with each milestone will not be subject to a significant reversal in the cumulative amount of revenue recognized. Amounts that meet this threshold are included in the transaction price using the most likely amount method, whereas amounts that do not meet this threshold are considered constrained and excluded from the transaction price until they meet this threshold. Milestones tied to regulatory approval, and therefore not within our control, are considered constrained until such approval is received. At the end of each subsequent reporting period, we re-evaluate the probability of a significant reversal of the cumulative revenue recognized for our milestones, and, if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues from collaborators and loss in the period of adjustment. For arrangements that include sales-based milestone or royalty payments based on the level of sales, and in which the license is deemed to be the predominant item to which the sales-based milestone or royalties relate to, we recognize revenue in the period in which the sales-based milestone is achieved and in the period in which the sales associated with the royalty occur. Adoption of ASC 606 We adopted ASC 606 using the modified retrospective method. Under this method, we recognized the cumulative effect of the change in the opening balance of accumulated deficit in the December 31, 2018 consolidated balance sheet. In adopting ASC 606, we applied the practical expedient that permits aggregating the effect of all contract modifications that occurred prior to January 1, 2018. No other practical expedients were used. The impact of the cumulative effect of the accounting changes upon the adoption of the standard is as follows: (In thousands) December 31, Cumulative January 1, Deferred revenue – related party, current and net of current portions $ 163,640 $ (39,456) $ 124,184 Accumulated deficit (798,061) 39,456 (758,605) The following tables summarize the effects of adopting ASC 606 on our consolidated financial statements: Consolidated Balance Sheets December 31, 2018 (In thousands) Under Topic Under Topic Effect of Accounts receivable, net $ 5,076 $ 5,076 $ — Collaboration receivable – related party 2,462 2,462 — Collaboration receivable – other 670 230 440 Total current assets 613,780 613,340 440 Total assets 858,457 858,017 440 Deferred revenue – related party 32,710 29,133 3,577 Total current liabilities 93,503 89,926 3,577 Deferred revenue, net of current portion – related party 59,809 101,180 (41,371) Total liabilities 170,920 208,714 (37,794) Accumulated deficit (1,104,633) (1,142,867) 38,234 Total stockholders’ equity 687,537 649,303 38,234 Total liabilities and stockholders’ equity 858,457 858,017 440 Consolidated Statements of Operations Year ended December 31, 2018 (In thousands, except per share data) Under Topic Under Topic Effect of Product revenue, net $ 13,841 $ 13,841 $ — Collaboration revenue – related party 60,661 58,994 1,667 Collaboration revenue – other 12,670 12,230 440 Total revenue 94,387 92,280 2,107 Research and development expense 341,324 337,995 3,329 Total cost and expenses 456,866 453,537 3,329 Loss from operations (362,479) (361,257) (1,222) Net loss (346,028) (344,806) (1,222) Net loss per share – basic and diluted (6.03) (6.01) (0.02) Consolidated Statements of Comprehensive Loss Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Comprehensive loss (346,810) (345,588) (1,222) Consolidated Statements of Cash Flows Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Adjustments to reconcile net loss to net cash used in operating activities: Accounts receivable, net (5,076) (5,076) — Collaboration receivable – related party (14) (14) — Collaboration receivable – other (670) (230) (440) Deferred revenue – related party (31,665) (33,327) 1,662
Cost of Sales	Cost of SalesCost of sales consists primarily of manufacturing costs of TIBSOVO®. Based on our policy to expense costs associated with the manufacturing of our products prior to regulatory approval, certain of the manufacturing costs associated with product shipments of TIBSOVO® recorded during the years ended December 31, 2019 and December 31, 2018 were expensed prior to July 20, 2018 and, therefore, are not included in costs of sales during the years ended December 31, 2019 or 2018.
Research and development costs	Research and development costs Research and development costs, including those accrued as of each balance sheet date, are expensed as incurred. These costs include salaries and personnel-related costs, consulting fees, fees paid for contract research services, fees paid to contract CROs, and other third parties in connection with clinical trials and preclinical development activities, fees paid to investigative sites in connection with clinical studies, the costs associated with the product manufacturing, development, and distribution of clinical supplies, the costs of laboratory equipment and facilities, and other external costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are deferred and capitalized. Additionally, there may be instances in which payments made to our vendors will exceed the level of services provided, and result in a prepayment of the research and development expense. The capitalized amounts are expensed as the related goods are delivered or the services are performed. We estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual or prepaid accordingly.
Stock-based compensation	Stock-based compensation We account for stock-based compensation awards in accordance with ASC 718, Compensation –Stock Compensation , or ASC 718. For stock-based awards granted to employees and to members of the board of directors for their services and for participation in our employee stock purchase plan, we primarily estimate the grant date fair value of each option award using the Black-Scholes option-pricing model. The use of the Black-Scholes option-pricing model requires us to make assumptions with respect to the expected term of the option, the expected volatility of the common stock consistent with the expected life of the option, risk-free interest rates and expected dividend yields of the common stock. For awards subject to service-based vesting conditions, we recognize stock-based compensation expense equal to the grant date fair value of stock options on a straight-line basis over the requisite service period. For awards subject to both performance and service-based vesting conditions, we recognize stock-based compensation expense over the remaining service period if the performance condition is considered probable of achievement using management’s best estimates. In 2017, we adopted ASU 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting , which simplifies several aspects of the accounting for employee share-based payment transactions, including income tax consequences, classification of awards as either equity or liabilities, and classification in the statement of
Income taxes	Income taxes Income taxes are recorded in accordance with ASC 740, Accounting for Income Taxes , or ASC 740, which provides for deferred taxes using an asset and liability approach. We recognize deferred tax assets and liabilities for the expected future tax consequences of events that have been included in our financial statements or tax returns. We determine our deferred tax assets and liabilities based on differences between the financial reporting and tax bases of assets and liabilities, which are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. Valuation allowances are provided, if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. We also account for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, we recognize the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances.
Comprehensive income (loss)	Comprehensive income (loss) Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period from transactions, and other events and circumstances, and currently consists of net loss and unrealized gains and losses on available-for-sale securities. Accumulated other comprehensive loss consists entirely of unrealized gains and losses from available-for-sale securities as of December 31, 2019 and 2018.
Net loss per share	Net loss per share Basic net loss per share is calculated by dividing net loss by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the dilutive net loss per share calculation, stock options, restricted stock units, performance-based stock units and market-based stock units for which the performance vesting conditions have been met, and employee stock purchase plan shares are considered to be common stock equivalents but are excluded from the calculation of diluted net loss per share as their effect would be anti-dilutive.
Segment and geographic information	Segment and geographic information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. Our chief operating decision maker is the chief executive officer. Our chief operating decision maker and we view our operations and manage our business as one operating segment.
Recent accounting pronouncements	Recent accounting pronouncements Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) , which was codified as ASC 842, Leases , and amended through subsequent ASUs. We adopted ASC 842 effective January 1, 2019 using the optional transition method provided for under ASU 2018-11, Leases (Topic 842): Targeted Improvements , whereby we applied the new lease requirements through a cumulative-effect adjustment, which after completing our implementation analysis, resulted in no material adjustment to our January 1, 2019 beginning accumulated deficit balance. We also elected the package of practical expedients provided for under ASU 2018-11, which allows us not to reassess whether contracts are or contain leases, lease classification, and whether initial direct costs qualify for capitalization. Additionally, as an accounting policy, for our building leases, we chose not to separate the non-lease components from the lease components and, instead, accounted for each non-lease component and lease component as a single component. We completed our assessment over the impact of the standard and determined that the only material leases that we hold are our building leases. Upon adoption of the standard on January 1, 2019, we recorded operating right of use assets of $59.9 million and operating lease liabilities of $77.3 million on our consolidated balance sheets. Prior periods are presented in accordance with ASC 840, Leases . Other recent accounting pronouncements In June 2018, the FASB issued Accounting Standards Update No. 2018-07 – Compensation-Stock Compensation (Topic 718)-Improvements to Nonemployee Share-Based Payment Accounting . ASU 2018-07 simplifies the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. ASU 2018-07 is effective for fiscal years beginning after December 15, 2018. The Company adopted the new standard as of January 1, 2019. There was no material impact to the Company’s consolidated financial position, results of operation, or cash flows. In December 2019, the FASB issued Accounting Standards Update No. 2019-12 – Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes, as part of its initiative to reduce complexity in the accounting standards. The amendments in ASU 2019-12 eliminate certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also clarifies and simplifies other aspects of the accounting for income taxes. The amendments in ASU 2019-12 are effective for the fiscal years beginning after December 15, 2020. Early adoption is permitted, including adoption in any interim period. The Company has early adopted this amendment as of January 1, 2019. There was no material impact to the Company’s consolidated financial position, results of operation, or cash flows. Other accounting standards that have been issued by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on our financial statements upon adoption.
Subsequent events	Subsequent events We considered events or transactions occurring after the balance sheet date, but prior to the issuance of the consolidated financial statements, for potential recognition or disclosure in our consolidated financial statements. All significant subsequent events have been properly disclosed in the consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Estimated Useful Lives of Property and Equipment	Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets: Years Laboratory equipment 5 Computer equipment and software 3 Furniture and fixtures 5 Office equipment 5
Schedule of Impact of New Accounting Pronouncements	The impact of the cumulative effect of the accounting changes upon the adoption of the standard is as follows: (In thousands) December 31, Cumulative January 1, Deferred revenue – related party, current and net of current portions $ 163,640 $ (39,456) $ 124,184 Accumulated deficit (798,061) 39,456 (758,605) The following tables summarize the effects of adopting ASC 606 on our consolidated financial statements: Consolidated Balance Sheets December 31, 2018 (In thousands) Under Topic Under Topic Effect of Accounts receivable, net $ 5,076 $ 5,076 $ — Collaboration receivable – related party 2,462 2,462 — Collaboration receivable – other 670 230 440 Total current assets 613,780 613,340 440 Total assets 858,457 858,017 440 Deferred revenue – related party 32,710 29,133 3,577 Total current liabilities 93,503 89,926 3,577 Deferred revenue, net of current portion – related party 59,809 101,180 (41,371) Total liabilities 170,920 208,714 (37,794) Accumulated deficit (1,104,633) (1,142,867) 38,234 Total stockholders’ equity 687,537 649,303 38,234 Total liabilities and stockholders’ equity 858,457 858,017 440 Consolidated Statements of Operations Year ended December 31, 2018 (In thousands, except per share data) Under Topic Under Topic Effect of Product revenue, net $ 13,841 $ 13,841 $ — Collaboration revenue – related party 60,661 58,994 1,667 Collaboration revenue – other 12,670 12,230 440 Total revenue 94,387 92,280 2,107 Research and development expense 341,324 337,995 3,329 Total cost and expenses 456,866 453,537 3,329 Loss from operations (362,479) (361,257) (1,222) Net loss (346,028) (344,806) (1,222) Net loss per share – basic and diluted (6.03) (6.01) (0.02) Consolidated Statements of Comprehensive Loss Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Comprehensive loss (346,810) (345,588) (1,222) Consolidated Statements of Cash Flows Year ended December 31, 2018 (In thousands) Under Topic Under Topic Effect of Net loss $ (346,028) $ (344,806) $ (1,222) Adjustments to reconcile net loss to net cash used in operating activities: Accounts receivable, net (5,076) (5,076) — Collaboration receivable – related party (14) (14) — Collaboration receivable – other (670) (230) (440) Deferred revenue – related party (31,665) (33,327) 1,662

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis	The following table summarizes our cash equivalents and marketable securities measured at fair value and by level (as described in Note 2. Summary of Significant Accounting Policies ) on a recurring basis as of December 31, 2019: (In thousands) Level 1 Level 2 Level 3 Total Cash equivalents $ 12,568 $ 36,299 $ — $ 48,867 Total cash equivalents 12,568 36,299 — 48,867 Marketable securities: Certificates of deposit — — — — U.S. Treasuries — 214,027 — 214,027 Government securities — 97,820 — 97,820 Corporate debt securities — 325,028 — 325,028 Total marketable securities — 636,875 — 636,875 Total cash equivalents and marketable securities $ 12,568 $ 673,174 $ — $ 685,742

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Summary of Marketable Securities	Marketable securities at December 31, 2019 consisted of the following: (In thousands) Amortized Unrealized Unrealized Fair Current: Certificates of deposit $ — $ — $ — $ — U.S. Treasuries 178,721 58 (38) 178,741 Government securities 80,228 17 (16) 80,229 Corporate debt securities 224,928 139 (91) 224,976 Total Current 483,877 214 (145) 483,946 Non-current: U.S. Treasuries 35,296 3 (13) 35,286 Government securities 17,587 14 (10) 17,591 Corporate debt securities 99,913 239 (100) 100,052 Total Non-current 152,796 256 (123) 152,929 Total marketable securities $ 636,673 $ 470 $ (268) $ 636,875 Marketable securities at December 31, 2018 consisted of the following: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Current: Certificates of deposit $ 960 $ — $ (4) $ 956 U.S. Treasuries 231,101 7 (228) 230,880 Government securities 75,335 — (121) 75,214 Corporate debt securities 208,233 — (483) 207,750 Total Current 515,629 7 (836) 514,800 Non-current: U.S. Treasuries 12,202 4 (125) 12,081 Government securities 70,177 10 (188) 69,999 Corporate debt securities 139,082 12 (1,055) 138,039 Total Non-current 221,461 26 (1,368) 220,119 Total marketable securities $ 737,090 $ 33 $ (2,204) $ 734,919

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	Property and equipment, net consisted of the following at December 31: (In thousands) 2019 2018 Laboratory equipment $ 23,418 $ 20,165 Computer equipment and software 6,415 5,449 Leasehold improvements 23,879 22,084 Furniture and fixtures 2,101 1,065 Office equipment 589 407 Construction in progress 7,182 1,302 Total property and equipment 63,584 50,472 Less: accumulated depreciation (32,112) (26,152) Total property and equipment, net $ 31,472 $ 24,320

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2019
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventory consisted of the following at December 31: (In thousands) 2019 2018 Raw materials $ 180 $ — Work-in-process 6,808 788 Finished goods 343 81 Total Inventory $ 7,331 $ 869

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of Undiscounted Minimum Rental Commitments Under Topic 842	As of December 31, 2019, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter, were as follows: (In thousands) 2020 $ 13,242 2021 14,380 2022 16,773 2023 18,126 2024 18,660 Thereafter 63,891 Undiscounted minimum rental commitments 145,072 Interest (32,356) Total operating lease liabilities $ 112,716
Schedule of Undiscounted Minimum Rental Commitments Under Topic 840	As of December 31, 2018, minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter, were as follows: (In thousands) 2019 $ 12,759 2020 13,135 2021 13,473 2022 15,552 2023 17,145 Thereafter 19,223 Total minimum rental commitments $ 91,287

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Payables and Accruals [Abstract]
Summary of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following at December 31: (In thousands) 2019 2018 Accrued compensation $ 18,982 $ 20,843 Accrued research and development costs 21,777 14,777 Accrued professional fees 8,335 5,441 Accrued other 4,048 1,086 Total accrued expenses $ 53,142 $ 42,147

Product Revenue (Tables)

Product Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Schedule of Product Revenue	Our wholly owned product, TIBSOVO®, received approval from the FDA on July 20, 2018 for the treatment of adult patients with R/R AML with a susceptible IDH1 mutation. Upon FDA approval of TIBSOVO® in the U.S., we began generating product revenue from U.S. sales of TIBSOVO®. (In thousands) 2019 2018 2017 Product revenue, net $ 59,851 $ 13,841 $ —
Schedule of Product Revenue Allowance and Reserves	The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2019: (In thousands) Contractual Government Returns Total Balance at December 31, 2018 592 325 334 1,251 Current provisions relating to sales in the current year 7,899 2,387 1,464 11,750 Adjustments relating to prior years 8 (41) — (33) Payments/returns relating to sales in the current year (7,027) (1,286) — (8,313) Payments/returns relating to sales in the prior years (598) (261) — (859) Balance at December 31, 2019 874 1,124 1,798 3,796 The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the year ended December 31, 2018: (In thousands) Contractual Government Returns Total Balance at December 31, 2017 — — — — Current provisions relating to sales in the current year 1,777 422 334 2,533 Adjustments relating to prior years — — — — Payments/returns relating to sales in the current year (1,185) (97) — (1,282) Payments/returns relating to sales in the prior years — — — — Balance at December 31, 2018 592 325 334 1,251
Schedule of Revenue Related Reserves	Total revenue-related reserves for the years ended December 31, 2019 and 2018 above, included in our consolidated balance sheets, are summarized as follows: (In thousands) December 31, December 31, Reduction of accounts receivable $ 540 $ 326 Component of accrued expenses 3,256 925 Total revenue-related reserves $ 3,796 $ 1,251
Schedule of Changes in Contract Assets and Liabilities	The following table presents changes in our contract assets and liabilities during the year ended December 31, 2019: (In thousands) December 31, Additions Deductions December 31, Contract assets Accounts receivable, net (1) $ 5,076 $ 71,542 $ (67,666) $ 8,952 (1) Additions to accounts receivable, net relate to amounts billed to Customers for product sales and deductions primarily relate to collection of receivables during the reporting period. The following table presents changes in our contract assets and liabilities during the year ended December 31, 2018: (In thousands) December 31, Additions Deductions December 31, Contract assets Accounts receivable, net (1) $ — $ 16,374 $ (11,298) $ 5,076

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue Recognition and Deferred Revenue [Abstract]
Schedule of Milestone-Based Payments Associated With 2016 Agreement	We are eligible to receive the following milestone-based payments associated with the 2016 Agreement: Program Milestone Amount 65/35 program in IO field Specified clinical development event $25.0 million 65/35 program in IO field Specified regulatory milestone events Up to $183.8 million 50/50 program in IO field Specified clinical development event $20.0 million 50/50 program in IO field Specified regulatory milestone events Up to $148.8 million I&I field Specified clinical development event $25.0 million I&I field Specified regulatory milestone events Up to $236.3 million I&I field Specified commercial milestone events Up to $125.0 million
Schedule of Satisfied and Unsatisfied Performance Obligations	The satisfied and unsatisfied performance obligations at the time of the adoption of ASC 606, each of which are considered by us to be distinct within the context of the contract, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized were as follows: Performance SSP No. of Performance Recognition Fully satisfied at time of adoption Licenses (1) $ 86.7 million 4 Fully satisfied; recognized upon adoption of ASC 606 Research and development services (2) $ 350.7 million 10 Fully satisfied; recognized upon adoption of ASC 606 Partially satisfied at time of adoption Research and development services (2) $ 266.6 million 6 Proportionally as services are delivered over the performance period, expected to be through September 2023 (3) (1) The SSP was developed by probability weighting multiple cash flow scenarios using the income approach. Our management estimates within the models include the expected, probability-weighted net profits from estimated future sales, an estimate of the direct cost incurred to generate future cash flows, a discount rate and other business forecast factors. There are significant judgments and estimates inherent in the determination of the SSP of these performance obligations. These judgments and estimates include assumptions regarding future operating performance, the timelines of the clinical trials and regulatory approvals, and other factors. If different reasonable assumptions are utilized, the SSP and revenue recognized would vary. (2) The SSP was developed using our management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider and using internal full time equivalent costs to support the development services. (3) We determined that recognizing revenue on a proportional basis using the ratio of effort incurred to date compared to the total estimated effort required to complete the performance obligation best depicts the satisfaction of our obligations under the Collaboration Agreements. As of December 31, 2019, the remaining performance obligations under the Celgene agreements, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized are as follows: Performance SSP No. of Remaining Performance Recognition Research and development services $175.4 million 2 Proportionally as services are delivered over the performance period
Summary of Collaboration Revenue	During the years ended December 31, we recognized the following collaboration revenue: (In thousands) 2019 2018 2017 (1) Services performed that were considered performance obligations upon the adoption of ASC 606 Licenses $ — $ 15,000 $ — On-going research and development services 35,954 40,575 37,953 Committee participation — — 167 Services performed that were not considered performance obligations as of the adoption of ASC 606 Development activities — 1,342 — Commercialization Activities 3,303 3,744 2,954 Total collaboration revenue - related party 39,257 60,661 41,074 (1) Amounts prior to 2018 do not reflect the impact of the adoption of Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606), in the first quarter of 2018. See Note 2. Summary of Significant Accounting Policies for additional information. During the years ended December 31, we recognized the following collaboration revenue: (In thousands) 2019 2018 2017 Services performed that were considered performance obligations upon contract inception Licenses $ 5,000 $ 12,440 $ — Other services 235 — — Services performed that were not considered performance obligations upon contract inception Other services 3,027 230 — Total collaboration revenue - other $ 8,262 $ 12,670 $ —
Schedule of Changes in Contract Assets and Liabilities	The following table presents changes in our contract assets and liabilities during the year ended December 31, 2019: (In thousands) December 31, Additions Deductions December 31, Contract assets Collaboration receivable – related party (1) $ 2,462 $ 8,253 $ (9,176) $ 1,539 Royalty receivable – related party (2) 2,234 10,542 (9,876) 2,900 Contract liabilities Deferred revenue – related party, current and non-current portions (3) 92,519 4,948 (35,954) 61,513 (1) Additions to collaboration receivables - related party relate to amounts billed to Celgene for reimbursable costs incurred by us during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. The following table presents changes in our contract assets and liabilities during the year ended December 31, 2018: (In thousands) December 31, Additions Deductions December 31, Contract assets Collaboration receivable – related party (1) $ 2,448 $ 28,695 $ (28,681) $ 2,462 Royalty receivable – related party (2) 1,222 7,087 (6,075) 2,234 Contract liabilities Deferred revenue – related party, current and non-current portions (3) 163,640 9,237 (80,358) 92,519 (1) Additions to collaboration receivables - related party relate to amounts billed to Celgene for reimbursable costs incurred by us during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. (2) Additions to receivables relate to amounts billed to Celgene during the reporting period. Deductions to receivables relate to collection of receivables during the reporting period. (3) Additions to deferred revenue relate to consideration from Celgene during the reporting period. Deductions relate to deferred revenue recognized as revenue during the reporting period and the cumulative catch-up adjustment recognized upon adoption of ASC 606 on January 1, 2018. During the years ended December 31, 2019, 2018 and 2017, we recognized the following as revenue due to changes in the contract liability balances: (In thousands) 2019 2018 2017 (1) Amounts included in the contract liability at the beginning of the period $ 31,605 $ 37,590 $ — Performance obligations satisfied in previous periods — 469 — (1) Amounts prior to 2018 do not reflect the impact of the adoption of Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers (Topic 606), in the first quarter of 2018. See Note 2. Summary of Significant Accounting Policies for additional information. The following table presents changes in our contract assets during the year ended December 31, 2019: (In thousands) December 31, Additions Deductions December 31 Contract assets Collaboration receivable – other (1) $ 670 $ 8,262 $ (7,004) $ 1,928 (1) Additions to contract assets relate to receivables from CStone and deductions to contract assets relate to collection of receivables during the reporting period. The following table presents changes in our contract assets during the year ended December 31, 2018: (In thousands) December 31, Additions Deductions December 31 Contract assets Collaboration receivable – other (1) $ — $ 12,670 $ (12,000) $ 670 (1) Additions to contract assets relate to receivables from CStone and deductions to contract assets relate to collection of receivables during the reporting period.
Schedule of Royalty Revenue	During the years ended December 31, 2019, 2018 and 2017, we recognized the following as royalty revenue: (In thousands) 2019 2018 2017 Royalty revenue – related party $ 10,542 $ 7,215 $ 1,937
Summary of Performance Obligations, CStone Agreement	The satisfied and unsatisfied performance obligations, each of which are considered by us to be distinct within the context of the contract, their SSP, the method of recognizing the allocated consideration, and the period through which they are expected to be recognized are as follows: Performance SSP No. of Performance Obligation(s) Recognition Licenses (1) $ 16.4 million 1 Fully satisfied; recognized upon delivery of license Other services (2) $ 1.7 million 1 As services are delivered, expected to be through September 2021 (1) The SSP was developed by probability weighting multiple cash flow scenarios using the income approach. Our management estimates within the models include the expected, probability-weighted net profits from estimated future sales, an estimate of the direct costs incurred to generate future cash flows, a discount rate and other business forecast factors. There are significant judgments and estimates inherent in the determination of the SSP of this performance obligation. These judgments and estimates include assumptions regarding future operating performance, the timelines of the clinical trials and regulatory approvals, and other factors. If different reasonable assumptions are utilized, the SSP and revenue recognized would vary. (2) The SSP was developed using our management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider.

Share-Based Payments (Tables)

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Summary of Company's Stock Option Activity of all Stock Incentive Plans	The following table summarizes the stock option activity of all stock incentive plans for the year ended December 31, 2019: Number of Stock Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2018 5,416,069 $ 60.10 7.30 $ 27,941 Granted 1,772,485 53.79 Exercised (283,200) 32.69 Forfeited/Expired (703,869) 68.36 Outstanding at December 31, 2019 6,201,485 $ 58.61 7.09 $ 28,528 Exercisable at December 31, 2019 3,541,821 $ 58.90 5.89 $ 25,258 Vested and expected to vest at December 31, 2019 6,201,485 $ 58.61 7.09 $ 28,528
Schedule of Restricted Stock Unit Activity	The following table presents RSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 532,144 $ 75.45 Granted 505,362 54.44 Vested (166,740) 69.58 Forfeited (103,813) 71.34 Unvested shares at December 31, 2019 766,953 $ 63.44
Schedule of Performance-Based Unit Activity	The following table presents PSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 169,031 $ 52.67 Granted 216,143 55.43 Vested (167,031) 52.36 Forfeited — — Unvested shares at December 31, 2019 218,143 $ 55.64
Schedule of Market-Based Unit Activity	The following table presents MSU activity for the year ended December 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 — $ — Granted 42,695 41.50 Unvested shares at December 31, 2019 42,695 $ 41.50
Schedule of Stock-Based Compensation Expense by Award Type Included Within the Condensed Consolidated Statements of Operations	Stock-based compensation expense by award type included within the consolidated statements of operations is as follows: (In thousands) 2019 2018 2017 Stock options $ 48,219 $ 51,460 $ 43,997 Restricted stock units 19,079 12,032 2,858 Performance-based stock units 2,647 8,717 — Employee Stock Purchase Plan 1,437 1,148 954 Other stock awards 991 — — Total stock-based compensation expense $ 72,373 $ 73,357 $ 47,809
Stock-Based Compensation Expense for Employee and Non-Employee Stock Options, Restricted Stock Units, Performance-Based Stock Options, Performance-Based Stock Units and Employee Stock Purchase Plan Shares	Expenses related to equity-based awards were allocated as follows in the consolidated statements of operations: (In thousands) 2019 2018 2017 Research and development expense $ 39,029 $ 41,982 $ 30,807 Selling, general and administrative expense 33,344 31,375 17,002 Total stock-based compensation expense $ 72,373 $ 73,357 $ 47,809
Schedule of Grant Date Fair Value Option Award Weighted Average Assumptions Used	The following table summarizes the weighted average assumptions used in calculating the grant date fair value of the awards: 2019 2018 2017 Risk-free interest rate 2.32 % 2.71 % 2.05 % Expected dividend yield — — — Expected term (in years) 6.06 6.06 6.05 Expected volatility 76.19 % 76.62 % 77.73 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Schedule of Domestic and Foreign Components of Loss Before Income Taxes	The domestic and foreign components of loss before income taxes are as follows: (In thousands) 2019 2018 2017 Domestic $ (432,535) $ (311,159) $ (290,423) Foreign 21,063 (34,869) (24,247) Total $ (411,472) $ (346,028) $ (314,670)
Reconciliation of Expected Income Tax Benefit (Expense) Computed Using Federal Statutory Income Tax Rate	A reconciliation of the expected income tax benefit (expense) computed using the federal statutory income tax rate to our effective income tax rate is as follows for the years ended December 31, 2019, 2018 and 2017: 2019 2018 2017 Income tax benefit computed at federal statutory tax rate 21.0 % 21.0 % 35.0 % State taxes, net of federal benefit 2.8 % 0.8 % 4.0 % Change in valuation allowance (27.2) % (28.4) % (19.4) % General business credits and other credits 5.0 % 5.7 % 10.4 % Permanent differences and other adjustments (1.3) % (0.7) % — % Incentive stock options (0.6) % 2.2 % 0.3 % Foreign rate differential 0.3 % (0.6) % (1.6) % Impact of federal rate change — % — % (28.7) % Total — % — % — %
Company's Deferred Tax Assets and Liabilities	Significant components of our deferred tax assets and liabilities for the years ended December 31, 2019 and 2018 are as follows: (In thousands) 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 294,614 $ 211,563 Deferred revenue 14,372 21,956 Tax credit carryforwards 141,219 120,605 Purchased intangible assets 14,479 3,204 Stock-based compensation 30,861 27,636 Operating lease liability 27,173 — Deferred rent — 4,458 Non-deductible accruals and reserves, including inventory 4,729 4,900 Total deferred tax assets 527,447 394,322 Depreciation and amortization (2,613) (3,569) Operating lease right of use asset (22,625) — Less: valuation allowance (502,209) (390,753) Net deferred taxes $ — $ —
Schedule of Unrecognized Tax Benefits Rollforward	The following table presents our unrecognized tax benefits activity for the years ended December 31, 2019 and 2018: (In thousands) 2019 2018 Unrecognized tax benefits at the beginning of the year $ 14,288 $ 11,263 Gross increases - current period tax positions 3,172 3,025 Unrecognized tax benefits at the end of the year $ 17,460 $ 14,288

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Common Stock Excluded from Calculation of Diluted Earnings Per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: Years ended December 31, 2019 2018 2017 Stock options 6,201,485 5,416,069 5,577,562 Restricted stock units 766,953 532,144 125,584 Performance-based stock units 72,046 169,031 — Employee Stock Purchase Plan shares 49,418 32,304 22,062 Total 7,089,902 6,149,548 5,725,208

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following table contains quarterly financial information for 2019 and 2018: 2019 (in thousands, except per share data) First Second Third Fourth Total revenue $ 30,227 $ 26,221 $ 26,024 $ 35,440 Loss from operations (97,483) (113,861) (109,060) (105,929) Net loss (93,078) (109,871) (106,173) (102,350) Net loss per share – basic and diluted (1.59) (1.87) (1.81) (1.60) 2018 (in thousands, except per share data) First Second Third Fourth Total revenue $ 8,762 $ 40,414 $ 15,198 $ 30,013 Loss from operations (94,012) (72,949) (99,162) (96,356) Net loss (90,825) (68,745) (94,664) (91,794) Net loss per share – basic and diluted (1.63) (1.19) (1.63) (1.58)

Nature of Business - Additional

Nature of Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Number of shares issued from public offering (in shares)	9,487,500
Net proceeds from public offering	$ 277,200	$ 277,201	$ 516,206	$ 270,250
Cash, cash equivalents and marketable securities		$ 717,800
Public Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued from public offering (in shares)	8,250,000
Offering price (in usd per share)	$ 31
Net proceeds from public offering	$ 241,000
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Number of shares issued from public offering (in shares)	1,237,500
Net proceeds from public offering	$ 36,200

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)segment	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)	Dec. 31, 2017USD ($)
Schedule of Significant Accounting Policies [Line Items]
Minimum period to liquidate	12 months
Accumulated deficit	$ (1,516,105)		$ (1,104,633)	$ (758,605)
Number of operating segments | segment	1
Operating right of use assets	$ 93,643
Total operating lease liabilities	$ 112,716
ASU 2016-09
Schedule of Significant Accounting Policies [Line Items]
Deferred tax assets					$ 32,700
Accumulated deficit					$ 32,700
ASU 2016-02
Schedule of Significant Accounting Policies [Line Items]
Operating right of use assets		$ 59,900
Total operating lease liabilities		$ 77,300
Minimum
Schedule of Significant Accounting Policies [Line Items]
Investment maturity period, non-current	1 year
Maximum
Schedule of Significant Accounting Policies [Line Items]
Investment maturity period, current	1 year
Investment maturity period, non-current	2 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2019
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	5 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	5 years
Office equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	5 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Impact of Accounting Changes Upon Adoption of ASC 606 (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018	Dec. 31, 2016
Cumulative Effect of Accounting Changes [Abstract]
Deferred revenue - related party, current and net of current portions													$ 124,184
Accumulated deficit		$ (1,516,105)				$ (1,104,633)				$ (1,516,105)	$ (1,104,633)		(758,605)
Statement of Financial Position [Abstract]
Accounts receivable, net		8,952				5,076				8,952	5,076
Collaboration receivable – related party		1,539				2,462				1,539	2,462
Collaboration receivable – other		1,928				670				1,928	670
Total current assets		611,704				613,780				611,704	613,780
Total assets		890,741				858,457				890,741	858,457
Deferred revenue – related party		10,933				32,710				10,933	32,710
Total current liabilities		92,886				93,503				92,886	93,503
Deferred revenue, net of current portion – related party		50,580				59,809				50,580	59,809
Total liabilities		250,213				170,920				250,213	170,920
Total stockholders’ equity		640,528				687,537				640,528	687,537	$ 375,503		$ 358,591
Total liabilities and stockholders’ equity		890,741				858,457				890,741	858,457
Income Statement [Abstract]
Revenues		35,440	$ 26,024	$ 26,221	$ 30,227	30,013	$ 15,198	$ 40,414	$ 8,762	117,912	94,387	43,011
Upfront payment for research and development	[1]									410,894	341,324	292,681
Total cost and expenses											456,866
Loss from operations		$ (105,929)	$ (109,060)	$ (113,861)	$ (97,483)	$ (96,356)	$ (99,162)	$ (72,949)	$ (94,012)	(426,333)	(362,479)	(320,794)
Net loss										$ (411,472)	$ (346,028)	$ (314,670)
Net loss per share - basic and diluted (in usd per share)		$ (1.60)	$ (1.81)	$ (1.87)	$ (1.59)	$ (1.58)	$ (1.63)	$ (1.19)	$ (1.63)	$ (6.86)	$ (6.03)	$ (6.75)
Statement of Comprehensive Income [Abstract]
Comprehensive loss										$ (409,099)	$ (346,810)	$ (315,746)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable, net										(3,876)	(5,076)	0
Collaboration receivable – related party										923	(14)	2,438
Collaboration receivable – other										1,258	670	0
Deferred revenue – related party										(31,006)	(31,665)	(26,570)
Product revenue, net
Income Statement [Abstract]
Revenues										59,851	13,841	0
Collaboration revenue – related party
Income Statement [Abstract]
Revenues										39,257	60,661	41,074
Collaboration revenue – other
Income Statement [Abstract]
Revenues										$ 8,262	12,670	0
Under Topic 605
Cumulative Effect of Accounting Changes [Abstract]
Deferred revenue - related party, current and net of current portions												163,640
Accumulated deficit						$ (1,142,867)					(1,142,867)	$ (798,061)
Statement of Financial Position [Abstract]
Accounts receivable, net						5,076					5,076
Collaboration receivable – related party						2,462					2,462
Collaboration receivable – other						230					230
Total current assets						613,340					613,340
Total assets						858,017					858,017
Deferred revenue – related party						29,133					29,133
Total current liabilities						89,926					89,926
Deferred revenue, net of current portion – related party						101,180					101,180
Total liabilities						208,714					208,714
Total stockholders’ equity						649,303					649,303
Total liabilities and stockholders’ equity						858,017					858,017
Income Statement [Abstract]
Revenues											92,280
Upfront payment for research and development											337,995
Total cost and expenses											453,537
Loss from operations											(361,257)
Net loss											$ (344,806)
Net loss per share - basic and diluted (in usd per share)											$ (6.01)
Statement of Comprehensive Income [Abstract]
Comprehensive loss											$ (345,588)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable, net											(5,076)
Collaboration receivable – related party											(14)
Collaboration receivable – other											230
Deferred revenue – related party											(33,327)
Under Topic 605 | Product revenue, net
Income Statement [Abstract]
Revenues											13,841
Under Topic 605 | Collaboration revenue – related party
Income Statement [Abstract]
Revenues											58,994
Under Topic 605 | Collaboration revenue – other
Income Statement [Abstract]
Revenues											12,230
ASU 2014-09 | Cumulative Effect and Effect of Change
Cumulative Effect of Accounting Changes [Abstract]
Deferred revenue - related party, current and net of current portions													(39,456)
Accumulated deficit						38,234					38,234		$ 39,456
Statement of Financial Position [Abstract]
Accounts receivable, net						0					0
Collaboration receivable – related party						0					0
Collaboration receivable – other						440					440
Total current assets						440					440
Total assets						440					440
Deferred revenue – related party						3,577					3,577
Total current liabilities						3,577					3,577
Deferred revenue, net of current portion – related party						(41,371)					(41,371)
Total liabilities						(37,794)					(37,794)
Total stockholders’ equity						38,234					38,234
Total liabilities and stockholders’ equity						$ 440					440
Income Statement [Abstract]
Revenues											2,107
Upfront payment for research and development											3,329
Total cost and expenses											3,329
Loss from operations											(1,222)
Net loss											$ (1,222)
Net loss per share - basic and diluted (in usd per share)											$ (0.02)
Statement of Comprehensive Income [Abstract]
Comprehensive loss											$ (1,222)
Adjustments to reconcile net loss to net cash used in operating activities:
Accounts receivable, net											0
Collaboration receivable – related party											0
Collaboration receivable – other											440
Deferred revenue – related party											1,662
ASU 2014-09 | Cumulative Effect and Effect of Change | Product revenue, net
Income Statement [Abstract]
Revenues											0
ASU 2014-09 | Cumulative Effect and Effect of Change | Collaboration revenue – related party
Income Statement [Abstract]
Revenues											1,667
ASU 2014-09 | Cumulative Effect and Effect of Change | Collaboration revenue – other
Income Statement [Abstract]
Revenues											$ 440
[1]	(1) Total research and development expenses are net of cost reimbursements from related party of $0, $0, and $7,811 for the years ended December 31, 2019, 2018 and 2017, respectively.

Fair Value Measurements - Cash

Fair Value Measurements - Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	$ 636,875	$ 734,919
Fair Value, Measurements, Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	48,867
Total marketable securities	636,875
Total cash equivalents and marketable securities	685,742
Fair Value, Measurements, Recurring | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	48,867
Fair Value, Measurements, Recurring | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	214,027
Fair Value, Measurements, Recurring | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	97,820
Fair Value, Measurements, Recurring | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	325,028
Fair Value, Measurements, Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	12,568
Total marketable securities	0
Total cash equivalents and marketable securities	12,568
Fair Value, Measurements, Recurring | Level 1 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	12,568
Fair Value, Measurements, Recurring | Level 1 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	36,299
Total marketable securities	636,875
Total cash equivalents and marketable securities	673,174
Fair Value, Measurements, Recurring | Level 2 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	36,299
Fair Value, Measurements, Recurring | Level 2 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 2 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	214,027
Fair Value, Measurements, Recurring | Level 2 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	97,820
Fair Value, Measurements, Recurring | Level 2 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	325,028
Fair Value, Measurements, Recurring | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0
Total marketable securities	0
Total cash equivalents and marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total cash equivalents	0
Fair Value, Measurements, Recurring | Level 3 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total marketable securities	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Dec. 31, 2019USD ($)
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets (liabilities)	$ 0

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 636,673	$ 737,090
Unrealized Gains	470	33
Unrealized Losses	(268)	(2,204)
Fair Value	636,875	734,919
Current
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	483,877	515,629
Unrealized Gains	214	7
Unrealized Losses	(145)	(836)
Fair Value	483,946	514,800
Current | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	0	960
Unrealized Gains	0	0
Unrealized Losses	0	(4)
Fair Value	0	956
Current | U.S. Treasuries
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	178,721	231,101
Unrealized Gains	58	7
Unrealized Losses	(38)	(228)
Fair Value	178,741	230,880
Current | Government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,228	75,335
Unrealized Gains	17	0
Unrealized Losses	(16)	(121)
Fair Value	80,229	75,214
Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	224,928	208,233
Unrealized Gains	139	0
Unrealized Losses	(91)	(483)
Fair Value	224,976	207,750
Non Current
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	152,796	221,461
Unrealized Gains	256	26
Unrealized Losses	(123)	(1,368)
Fair Value	152,929	220,119
Non Current | U.S. Treasuries
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,296	12,202
Unrealized Gains	3	4
Unrealized Losses	(13)	(125)
Fair Value	35,286	12,081
Non Current | Government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,587	70,177
Unrealized Gains	14	10
Unrealized Losses	(10)	(188)
Fair Value	17,591	69,999
Non Current | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	99,913	139,082
Unrealized Gains	239	12
Unrealized Losses	(100)	(1,055)
Fair Value	$ 100,052	$ 138,039

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)security	Dec. 31, 2018USD ($)security
Investments, Debt and Equity Securities [Abstract]
Realized gain (loss) on marketable securities	$ 0	$ 0
Debt securities in an unrealized loss position | security	113	242
Aggregate fair value of debt securities in an unrealized loss position	$ 345.7	$ 639.3

Property and Equipment, net - S

Property and Equipment, net - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 63,584	$ 50,472
Less: accumulated depreciation	(32,112)	(26,152)
Total property and equipment, net	31,472	24,320
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	23,418	20,165
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	6,415	5,449
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	23,879	22,084
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	2,101	1,065
Office equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	589	407
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 7,182	$ 1,302

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 8	$ 7.2	$ 6.4

Inventory - Schedule of Invento

Inventory - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 180	$ 0
Work-in-process	6,808	788
Finished goods	343	81
Total Inventory	$ 7,331	$ 869

Inventory - Additional Informat

Inventory - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory write-downs	$ 0	$ 0

Leases - Additional Information

Leases - Additional Information (Details) ft² in Thousands, $ in Millions	Apr. 11, 2019USD ($)ft²lease_term	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost		$ 15.1
Cash paid for amounts included in measurement of lease liabilities		$ 12.8
Weighted-average incremental borrowing rate		5.70%
Weighted-average remaining lease term		8 years 2 months 12 days
Rent expense			$ 11.4	$ 6
Standby letter of credit		$ 2.9
38 Sidney Street Lease
Lessee, Lease, Description [Line Items]
Number of square feet of office space (in square feet) | ft²	13
Number of optional terms available at end of current lease term (in lease terms) | lease_term	2
Term of optional lease (in years)	5 years
Tenant improvement allowance	$ 1
64 Sidney Street Lease
Lessee, Lease, Description [Line Items]
Term for extension of operating lease (in years)	3 years

Leases - Schedule of Undiscount

Leases - Schedule of Undiscounted Minimum Rental Commitments Under Topic 842 (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 13,242
2021	14,380
2022	16,773
2023	18,126
2024	18,660
Thereafter	63,891
Undiscounted minimum rental commitments	145,072
Interest	(32,356)
Total operating lease liabilities	$ 112,716

Leases - Schedule of Minimum Re

Leases - Schedule of Minimum Rental Commitments Under Topic 840 (Details) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 12,759
2020	13,135
2021	13,473
2022	15,552
2023	17,145
Thereafter	19,223
Total minimum rental commitments	$ 91,287

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued compensation	$ 18,982	$ 20,843
Accrued research and development costs	21,777	14,777
Accrued professional fees	8,335	5,441
Accrued other	4,048	1,086
Total accrued expenses	$ 53,142	$ 42,147

Commitments and Contingent Li_2

Commitments and Contingent Liabilities - Additional Information (Details)	Dec. 31, 2019lawsuit
Commitments and Contingencies Disclosure [Abstract]
Number of ongoing legal proceedings	0

Product Revenue - Schedule of P

Product Revenue - Schedule of Product Revenues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 35,440	$ 26,024	$ 26,221	$ 30,227	$ 30,013	$ 15,198	$ 40,414	$ 8,762	$ 117,912	$ 94,387	$ 43,011
Product revenue, net
Disaggregation of Revenue [Line Items]
Revenues									$ 59,851	$ 13,841	$ 0

Product Revenue - Schedule of_2

Product Revenue - Schedule of Product Revenue Allowance and Reserves (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Contractual Adjustments
Contractual adjustments, beginning balance	$ 592	$ 0
Contractual adjustments, current provisions relating to sales in the current year	7,899	1,777
Contractual adjustments, adjustments relating to prior years	8	0
Contractual adjustments, payments/returns relating to sales in the current year	(7,027)	(1,185)
Contractual adjustments, payments/returns relating to sales in the prior year	(598)	0
Contractual adjustments, ending balance	874	592
Government Rebates
Government rebates, beginning balance	325	0
Government rebates, current provisions relating to sales in the current year	2,387	422
Government rebates, adjustments relating to prior years	(41)	0
Government rebates, payments/returns relating to sales in the current year	(1,286)	(97)
Government rebates, payments/returns relating to sales in the prior years	(261)	0
Government rebates, ending balance	1,124	325
Returns
Returns, beginning balance	334	0
Returns, current provisions relating to sales in the current year	1,464	334
Returns, adjustments relating to prior years	0	0
Returns, payments/returns relating to sales in the current year	0	0
Returns, payments/returns relating to sales in the prior years	0	0
Returns, ending balance	1,798	334
Total
Total revenue-related reserves	3,796	1,251	$ 0
Total allowances and reserves, current provisions relating to sales in the current year	11,750	2,533
Total allowances and reserves, adjustments relating to prior years	(33)	0
Total allowances and reserves, payments/returns relating to sales in the current year	(8,313)	(1,282)
Total allowances and reserves, payments/returns relating to sales in the prior years	$ (859)	$ 0

Product Revenue - Schedule of R

Product Revenue - Schedule of Revenue-Related Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Reduction of accounts receivable	$ 540	$ 326
Component of accrued expenses	3,256	925
Total revenue-related reserves	$ 3,796	$ 1,251	$ 0

Product Revenue - Schedule of C

Product Revenue - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Contract Assets and Liabilities [Roll Forward]
Contract assets, beginning balance	$ 5,076	$ 0
Additions	71,542	16,374
Deductions	(67,666)	(11,298)
Contract assets, ending balance	$ 8,952	$ 5,076

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Details)		May 17, 2016USD ($)	Jun. 30, 2018USD ($)	Apr. 30, 2017USD ($)	May 31, 2016USD ($)extensionprogramProgram	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reduction of research and development costs						$ 0	$ 0	$ 7,811,000
Revenue from remaining performance obligations						70,000,000
Upfront payment for research and development	[1]					410,894,000	341,324,000	292,681,000
Potential milestone revenue							15,000,000
2010 Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received						80,000,000
Milestone payments upon achievement of specified regulatory milestone events						55,000,000
Milestone payment upon achievement of a specified commercial milestone event						25,000,000
2010 Agreement | Non-US
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified regulatory milestone events						35,000,000
AG-881 program licenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment for filing of first NDA						35,000,000
Celgene | 2016 Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of cancer metabolism programs discovered under previous agreement, now governed by current agreement | Program					2
Initial research term					4 years
Extension period | extension					2
Number of allowable special case extensions | extension					4
Special case extension term					1 year
Number of programs that may be designated for continued development for which development candidates have yet to be nominated | program					3
Initial payment received		$ 200,000,000
Upfront payment agreement extension fee receivable					$ 40,000,000
Designation fee receivable		8,000,000
Designation fees received								$ 8,000,000
Option exercise fee receivable		30,000,000
Additional option exercise fee for further development		10,000,000
Celgene | 2016 Agreement | Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Minimum option exercise fee receivable for continuation program		$ 35,000,000
Celgene | Co-Development and Co-Commercialization Agreements | 65/35 Program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Profit or loss share percentage					65.00%
Celgene | Co-Development and Co-Commercialization Agreements | Other Than 65/35 Program
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Profit or loss share percentage					50.00%
CStone Pharmaceuticals | CStone Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue from remaining performance obligations						400,000
Initial payment received			$ 12,000,000
Potential future milestone payments						407,000,000
Milestone revenue received						5,000,000
CStone Pharmaceuticals | CStone Agreement | Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty percentage			15.00%
CStone Pharmaceuticals | CStone Agreement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty percentage			19.00%
Aurigene Discovery Technologies Limited
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments				$ 15,000,000
Upfront payment for research and development				$ 3,000,000			$ 3,000,000
Aurigene Discovery Technologies Limited | DHODH Phase One Clinical Trial
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future milestone payments						$ 2,000,000
[1]	(1) Total research and development expenses are net of cost reimbursements from related party of $0, $0, and $7,811 for the years ended December 31, 2019, 2018 and 2017, respectively.

Collaboration and License Agr_4

Collaboration and License Agreements - Summary of Milestone-Based Receivable Payments (Details) - Celgene $ in Millions	May 31, 2016USD ($)
Specified clinical development event | Co Commercial Agreement
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	$ 25
Specified clinical development event | 65/35 Program | Co-Development and Co-Commercialization Agreements
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	25
Specified clinical development event | Other Than 65/35 Program | Co-Development and Co-Commercialization Agreements
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	20
Specified regulatory milestone events | Maximum | Co Commercial Agreement
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	236.3
Specified regulatory milestone events | Maximum | 65/35 Program | Co-Development and Co-Commercialization Agreements
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	183.8
Specified regulatory milestone events | Maximum | Other Than 65/35 Program | Co-Development and Co-Commercialization Agreements
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	148.8
Specified commercial milestone events | Maximum | Co Commercial Agreement
Revenue Recognition, Milestone Method [Line Items]
Milestone-based receivable payments, eligible to be received	$ 125

Collaboration and License Agr_5

Collaboration and License Agreements - Schedule of Satisfied and Unsatisfied Performance Obligations (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)performance_obligation
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 70,000
Licenses | Transferred at Point in Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 86,700
No. of Performance Obligation(s) | performance_obligation	4
Licenses | Transferred at Point in Time | CStone Agreement
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 16,400
No. of Performance Obligation(s) | performance_obligation	1
On-going research and development services | Transferred at Point in Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 350,700
No. of Performance Obligation(s) | performance_obligation	10
On-going research and development services | Transferred over Time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 266,600
No. of Performance Obligation(s) | performance_obligation	6
On-going research and development services | Transferred over Time | Celegne Agreements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 175,400
No. of Performance Obligation(s) | performance_obligation	2
Other services | Transferred over Time | CStone Agreement
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Stand alone selling price	$ 1,700
No. of Performance Obligation(s) | performance_obligation	1

Collaboration and License Agr_6

Collaboration and License Agreements - Collaboration Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 35,440	$ 26,024	$ 26,221	$ 30,227	$ 30,013	$ 15,198	$ 40,414	$ 8,762	$ 117,912	$ 94,387	$ 43,011
CStone Agreement
Disaggregation of Revenue [Line Items]
Revenues									8,262	12,670	0
Licenses
Disaggregation of Revenue [Line Items]
Revenues									0	15,000	0
Licenses | CStone Agreement
Disaggregation of Revenue [Line Items]
Revenues									5,000	12,440	0
On-going research and development services
Disaggregation of Revenue [Line Items]
Revenues									35,954	40,575	37,953
Committee participation
Disaggregation of Revenue [Line Items]
Revenues									0	0	167
Development activities
Disaggregation of Revenue [Line Items]
Revenues									0	1,342	0
Commercialization Activities
Disaggregation of Revenue [Line Items]
Revenues									3,303	3,744	2,954
Other services | CStone Agreement
Disaggregation of Revenue [Line Items]
Revenues									235	0	0
Other Services, Non-Performance Obligations | CStone Agreement
Disaggregation of Revenue [Line Items]
Revenues									3,027	230	0
Collaboration revenue – related party
Disaggregation of Revenue [Line Items]
Revenues									$ 39,257	$ 60,661	$ 41,074

Collaboration and License Agr_7

Collaboration and License Agreements - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change In Contract With Customer, Asset [Roll Forward]
Contract assets, beginning balance	$ 5,076	$ 0
Additions	71,542	16,374
Deductions	(67,666)	(11,298)
Contract assets, ending balance	8,952	5,076	$ 0
Change in Contract with Customer, Liability [Roll Forward]
Additions	31,605	37,590	0
Collaboration receivable – related party
Change In Contract With Customer, Asset [Roll Forward]
Contract assets, beginning balance	2,462	2,448
Additions	8,253	28,695
Deductions	(9,176)	(28,681)
Contract assets, ending balance	1,539	2,462	2,448
Collaboration receivable – related party | CStone Agreement
Change In Contract With Customer, Asset [Roll Forward]
Contract assets, beginning balance	670	0
Additions	8,262	12,670
Deductions	(7,004)	(12,000)
Contract assets, ending balance	1,928	670	0
Royalty receivable – related party
Change In Contract With Customer, Asset [Roll Forward]
Contract assets, beginning balance	2,234	1,222
Additions	10,542	7,087
Deductions	(9,876)	(6,075)
Contract assets, ending balance	2,900	2,234	1,222
Deferred revenue – related party, current and net of current portion
Change in Contract with Customer, Liability [Roll Forward]
Contract liabilities, beginning balance	92,519	163,640
Additions	4,948	9,237
Deductions	(35,954)	(80,358)
Contract liabilities, ending balance	$ 61,513	$ 92,519	$ 163,640

Collaboration and License Agr_8

Collaboration and License Agreements - Schedule of Revenues as a Result of Changes in Contract Asset and Contract Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue Recognition and Deferred Revenue [Abstract]
Amounts included in the contract liability at the beginning of the period	$ 31,605	$ 37,590	$ 0
Performance obligations satisfied in previous periods	$ 0	$ 469	$ 0

Collaboration and License Agr_9

Collaboration and License Agreements - Royalty Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues	$ 35,440	$ 26,024	$ 26,221	$ 30,227	$ 30,013	$ 15,198	$ 40,414	$ 8,762	$ 117,912	$ 94,387	$ 43,011
Royalty revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues									$ 10,542	$ 7,215	$ 1,937

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - shares	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized (in shares)	125,000,000	125,000,000

Share-Based Payments - Addition

Share-Based Payments - Additional Information (Details) - USD ($)	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax benefits related to stock based compensation		$ 0	$ 0	$ 0
Expected contractual term		10 years
Expected dividend yield		0.00%	0.00%	0.00%
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense excluding options		$ 28,100,000
Weighted-average period to recognize compensation expense		1 year 8 months 15 days
Performance-based stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense excluding options		$ 1,500,000
Weighted-average period to recognize compensation expense		3 months 29 days
Unrecognized compensation cost not expected to be recognized		$ 8,000,000
Market-based stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense excluding options		$ 800,000
Weighted-average period to recognize compensation expense		8 months 19 days
2007 Plan and 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards reserved for issuance (in shares)		9,356,754
Shares available for future issuance under 2013 ESPP (in shares)		2,127,478
2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in common stock (in shares)		2,000,000
Percentage of outstanding shares of common stock (in shares)		4.00%
Additional shares authorized for issuance (in shares)	2,000,000
Weighted-average grant date fair value of options (in usd per share)		$ 36.44	$ 53.22	$ 35.24
Intrinsic value of options exercised		$ 6,400,000	$ 65,100,000	$ 31,500,000
Unrecognized compensation expense related to options		$ 92,300,000
Weighted-average period to recognize compensation expense		2 years 6 months 14 days
2013 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance under 2013 ESPP (in shares)		82,555
Shares issued under 2013 ESPP (in shares)		77,981	53,255
Opportunity to purchase common stock (in shares)		327,272
2013 Employee Stock Purchase Plan | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance under 2013 ESPP (in shares)					509,091

Share-Based Payments - Summary

Share-Based Payments - Summary of Company's Stock Option Activity of all Stock Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of stock options, outstanding, beginning balance (in shares)	5,416,069
Number of stock options, granted (in shares)	1,772,485
Number of stock options, exercised (in shares)	(283,200)
Number of stock options, forfeited/expired (in shares)	(703,869)
Number of stock options, outstanding, ending balance (in shares)	6,201,485	5,416,069
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average exercise price, outstanding, beginning balance (in usd per share)	$ 60.10
Weighted-average exercise price, granted (in usd per share)	53.79
Weighted-average exercise price, exercised (in usd per share)	32.69
Weighted-average exercise price, forfeited/expired (in usd per share)	68.36
Weighted-average exercise price, outstanding, ending balance (in usd per share)	$ 58.61	$ 60.10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual term, outstanding (in years)	7 years 1 month 2 days	7 years 3 months 18 days
Aggregate intrinsic value, outstanding	$ 28,528	$ 27,941
Number of stock options, exercisable (in shares)	3,541,821
Weighted-average exercise price, exercisable (in usd per share)	$ 58.90
Weighted-average remaining contractual term, exercisable (in years)	5 years 10 months 20 days
Aggregate intrinsic value, exercisable	$ 25,258
Number of stock options, vested and expected to vest (in shares)	6,201,485
Weighted-average exercise price, vested and expected to vest (in usd per share)	$ 58.61
Weighted-average remaining contractual term, vested and expected to vest (in years)	7 years 1 month 2 days
Aggregate intrinsic value, vested and expected to vest	$ 28,528

Share-Based Payments - Summar_2

Share-Based Payments - Summary of Unvested RSUs, Performance-Based Stock and Market-Based Stock Unit Activity (Details)	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares beginning of period (in shares) | shares	532,144
Granted (in shares) | shares	505,362
Vested (in shares) | shares	(166,740)
Forfeited (in shares) | shares	(103,813)
Unvested shares end of period (in shares) | shares	766,953
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, unvested shares beginning of period (in usd per share) | $ / shares	$ 75.45
Weighted-average grant date fair value, granted (in usd per share) | $ / shares	54.44
Weighted-average grant date fair value, vested (in usd per share) | $ / shares	69.58
Weighted-average grant date fair value, forfeited/expired (in usd per share) | $ / shares	71.34
Weighted-average grant date fair value, unvested shares end of period (in usd per share) | $ / shares	$ 63.44
Performance-based stock units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares beginning of period (in shares) | shares	169,031
Granted (in shares) | shares	216,143
Vested (in shares) | shares	(167,031)
Forfeited (in shares) | shares	0
Unvested shares end of period (in shares) | shares	218,143
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, unvested shares beginning of period (in usd per share) | $ / shares	$ 52.67
Weighted-average grant date fair value, granted (in usd per share) | $ / shares	55.43
Weighted-average grant date fair value, vested (in usd per share) | $ / shares	52.36
Weighted-average grant date fair value, forfeited/expired (in usd per share) | $ / shares	0
Weighted-average grant date fair value, unvested shares end of period (in usd per share) | $ / shares	$ 55.64
Market-based stock units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares beginning of period (in shares) | shares	0
Granted (in shares) | shares	42,695
Unvested shares end of period (in shares) | shares	42,695
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted-average grant date fair value, unvested shares beginning of period (in usd per share) | $ / shares	$ 0
Weighted-average grant date fair value, granted (in usd per share) | $ / shares	41.50
Weighted-average grant date fair value, unvested shares end of period (in usd per share) | $ / shares	$ 41.50

Share-Based Payments - Schedule

Share-Based Payments - Schedule of Stock-Based Compensation by Award Type Included Within the Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 72,373	$ 73,357	$ 47,809
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	48,219	51,460	43,997
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	19,079	12,032	2,858
Performance-based stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,647	8,717	0
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,437	1,148	954
Other stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 991	$ 0	$ 0

Share-Based Payments - Stock-Ba

Share-Based Payments - Stock-Based Compensation Expense for Equity-Based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	$ 72,373	$ 73,357	$ 47,809
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	39,029	41,982	30,807
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	$ 33,344	$ 31,375	$ 17,002

Share-Based Payments - Schedu_2

Share-Based Payments - Schedule of Grant Date Fair Value Option Award Weighted Average Assumptions Used (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement [Abstract]
Risk-free interest rate	2.32%	2.71%	2.05%
Expected dividend yield	0.00%	0.00%	0.00%
Expected term (in years)	6 years 21 days	6 years 21 days	6 years 18 days
Expected volatility	76.19%	76.62%	77.73%

Income Taxes - Schedule of Dome

Income Taxes - Schedule of Domestic and Foreign Components of Loss Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Domestic	$ (432,535)	$ (311,159)	$ (290,423)
Foreign	21,063	(34,869)	(24,247)
Total	$ (411,472)	$ (346,028)	$ (314,670)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Expected Income Tax Benefit (Expense) Computed Using Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax benefit computed at federal statutory tax rate	21.00%	21.00%	35.00%
State taxes, net of federal benefit	2.80%	0.80%	4.00%
Change in valuation allowance	(27.20%)	(28.40%)	(19.40%)
General business credits and other credits	5.00%	5.70%	10.40%
Permanent differences and other adjustments	(1.30%)	(0.70%)	0.00%
Incentive stock options	(0.60%)	2.20%	0.30%
Foreign rate differential	0.30%	(0.60%)	(1.60%)
Impact of federal rate change	0.00%	0.00%	(28.70%)
Total	0.00%	0.00%	0.00%

Income Taxes - Company's Deferr

Income Taxes - Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 294,614	$ 211,563
Deferred revenue	14,372	21,956
Tax credit carryforwards	141,219	120,605
Purchased intangible assets	14,479	3,204
Stock-based compensation	30,861	27,636
Operating lease liability	27,173
Deferred rent	0	4,458
Non-deductible accruals and reserves, including inventory	4,729	4,900
Total deferred tax assets	527,447	394,322
Depreciation and amortization	(2,613)	(3,569)
Operating lease right of use asset	(22,625)
Less: valuation allowance	(502,209)	(390,753)
Net deferred taxes	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019USD ($)AuditOwnership	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Income Taxes Disclosure [Line Items]
Provision for income taxes	$ 0	$ 0	$ 0
Adjustment to income tax expense related to tax reform		90,000,000
Percentage of stock owned resulting in an ownership change	50.00%
Aggregate period	3 years
Number of ownership changes | Ownership	0
Valuation allowance	$ 502,209,000	$ 390,753,000
Increase (decrease) in valuation allowance	$ 111,400,000		$ 88,800,000
Number of federal, state or foreign audits in process | Audit	0
Federal Orphan Drug Tax Credit
Income Taxes Disclosure [Line Items]
Research and development tax credit	$ 98,100,000
Federal
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	1,133,000,000
Net operating loss, indefinite carryforward	669,600,000
Federal | Research Tax Credit Carryforward
Income Taxes Disclosure [Line Items]
Research and development tax credit	31,200,000
State and Local Jurisdiction
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	877,900,000
State and Local Jurisdiction | Research Tax Credit Carryforward
Income Taxes Disclosure [Line Items]
Research and development tax credit	15,000,000
Foreign Income Tax
Income Taxes Disclosure [Line Items]
Net operating loss carryforwards	$ 61,900,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning balance	$ 14,288	$ 11,263
Gross increases - current period tax positions	3,172	3,025
Unrecognized tax benefits, ending balance	$ 17,460	$ 14,288

Defined Contribution Benefit _2

Defined Contribution Benefit Plan - Additional Information (Details)	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Employer's matching contribution percentage	100.00%
Employer's contribution percentage of eligible compensation	4.00%

Net Loss per Share - Common Sto

Net Loss per Share - Common Stock Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,089,902	6,149,548	5,725,208
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,201,485	5,416,069	5,577,562
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	766,953	532,144	125,584
Performance-based stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	72,046	169,031	0
Employee Stock Purchase Plan shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	49,418	32,304	22,062

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 35,440	$ 26,024	$ 26,221	$ 30,227	$ 30,013	$ 15,198	$ 40,414	$ 8,762	$ 117,912	$ 94,387	$ 43,011
Loss from operations	(105,929)	(109,060)	(113,861)	(97,483)	(96,356)	(99,162)	(72,949)	(94,012)	$ (426,333)	$ (362,479)	$ (320,794)
Net loss	$ (102,350)	$ (106,173)	$ (109,871)	$ (93,078)	$ (91,794)	$ (94,664)	$ (68,745)	$ (90,825)
Net loss per share - basic and diluted (in usd per share)	$ (1.60)	$ (1.81)	$ (1.87)	$ (1.59)	$ (1.58)	$ (1.63)	$ (1.19)	$ (1.63)	$ (6.86)	$ (6.03)	$ (6.75)

Uncategorized Items - agio-2019

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 39,456,000
Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 39,456,000