Agios Pharmaceuticals (AGIO) 10-Q 2 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 26, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	AGIOS PHARMACEUTICALS INC
Trading Symbol	AGIO
Entity Central Index Key	0001439222
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		58,711,333

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 103,443	$ 70,502
Marketable securities	421,114	514,800
Accounts receivable, net	4,355	5,076
Collaboration receivable – related party	2,319	2,462
Collaboration receivable – other	1,640	670
Royalty receivable – related party	2,200	2,234
Inventory	2,328	869
Prepaid expenses and other current assets	19,696	17,167
Total current assets	557,095	613,780
Marketable securities	183,234	220,119
Operating lease assets	57,768
Property and equipment, net	23,974	24,320
Other non-current assets	60	238
Total assets	822,131	858,457
Current liabilities:
Accounts payable	12,413	17,880
Accrued expenses	37,199	42,147
Deferred revenue – related party	22,167	32,710
Operating lease liabilities	9,128
Deferred rent	0	766
Total current liabilities	80,907	93,503
Deferred revenue, net of current portion – related party	54,961	59,809
Operating lease liabilities, net of current portion	66,006
Deferred rent, net of current portion	0	17,608
Total liabilities	201,874	170,920
Stockholders’ equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized; no shares issued or outstanding at March 31, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value; 125,000,000 shares authorized; 58,659,821 and 58,218,653 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	59	58
Additional paid-in capital	1,818,393	1,794,283
Accumulated other comprehensive loss	(484)	(2,171)
Accumulated deficit	(1,197,711)	(1,104,633)
Total stockholders’ equity	620,257	687,537
Total liabilities and stockholders’ equity	$ 822,131	$ 858,457

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 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)	58,659,821	58,218,653
Common stock, shares outstanding (in shares)	58,659,821	58,218,653

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Total revenue	$ 30,227	$ 8,762
Cost and expenses:
Cost of sales	334	0
Research and development	95,585	78,224
Selling, general and administrative	31,791	24,550
Total cost and expenses	127,710	102,774
Loss from operations	(97,483)	(94,012)
Interest income	4,405	3,187
Net loss	$ (93,078)	$ (90,825)
Net loss per share – basic and diluted (in usd per share)	$ (1.59)	$ (1.63)
Weighted-average number of common shares used in computing net loss per share – basic and diluted	58,453,918	55,694,603
Product revenue, net
Revenues:
Total revenue	$ 9,138	$ 0
Collaboration revenue – related party
Revenues:
Total revenue	17,919	7,345
Collaboration revenue – other
Revenues:
Total revenue	970	0
Royalty revenue – related party
Revenues:
Total revenue	$ 2,200	$ 1,417

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (93,078)	$ (90,825)
Other comprehensive income (loss)
Unrealized gain (loss) on available-for-sale securities	1,687	(1,254)
Comprehensive loss	$ (91,391)	$ (92,079)

Condensed Consolidated Statem_3

Condensed 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, 2017		48,826,153
Beginning balance at Dec. 31, 2017	$ 375,503	$ 49	$ 1,174,904	$ (1,389)	$ (798,061)
Unrealized gain (loss) on available-for-sale securities	(1,254)			(1,254)
Net loss	(90,825)				(90,825)
Stock-based compensation expense	14,522		14,522
Issuance of common stock under stock incentive and employee stock purchase plan (in shares)		562,474
Issuance of common stock under stock incentive and employee stock purchase plans	12,332	$ 1	12,331
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	(346)		(346)
Ending balance (in shares) at Mar. 31, 2018		57,541,613
Ending balance at Mar. 31, 2018	865,594	$ 58	1,717,609	(2,643)	(849,430)
Beginning balance (in shares) at Dec. 31, 2018		58,218,653
Beginning balance at Dec. 31, 2018	687,537	$ 58	1,794,283	(2,171)	(1,104,633)
Unrealized gain (loss) on available-for-sale securities	1,687			1,687
Net loss	(93,078)				(93,078)
Stock-based compensation expense	$ 18,108		18,108
Issuance of common stock under stock incentive and employee stock purchase plan (in shares)	106,859	441,168
Issuance of common stock under stock incentive and employee stock purchase plans	$ 6,003	$ 1	6,002
Ending balance (in shares) at Mar. 31, 2019		58,659,821
Ending balance at Mar. 31, 2019	$ 620,257	$ 59	$ 1,818,393	$ (484)	$ (1,197,711)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (93,078)	$ (90,825)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,005	1,725
Stock-based compensation expense	18,108	14,522
Net amortization of premium and discounts on investments	(1,131)	(406)
Non-cash operating lease expense	2,085
Changes in operating assets and liabilities:
Accounts receivable, net	721	0
Collaboration receivable – related party	143	(1,064)
Collaboration receivable – other	(970)	0
Royalty receivable – related party	34	(195)
Inventory	(1,459)	0
Prepaid expenses and other current and non-current assets	(2,173)	1,901
Accounts payable	(4,939)	(4,469)
Accrued expenses	(5,097)	(17,144)
Deferred revenue – related party	(15,391)	(3,141)
Operating lease liabilities	(2,129)
Deferred rent	0	96
Net cash used in operating activities	(103,271)	(99,000)
Investing activities
Purchases of marketable securities	(77,421)	(330,971)
Proceeds from maturities and sales of marketable securities	210,811	164,871
Purchases of property and equipment	(2,038)	(1,432)
Net cash provided by (used in) investing activities	131,352	(167,532)
Financing activities
Payment of public offering costs, net of reimbursements	0	(188)
Proceeds from public offering of common stock, net of commissions	0	516,206
Net proceeds from stock option exercises and employee stock purchase plan	4,860	12,259
Net cash provided by financing activities	4,860	528,277
Net change in cash and cash equivalents	32,941	261,745
Cash and cash equivalents at beginning of the period	70,502	102,724
Cash and cash equivalents at end of the period	103,443	364,469
Supplemental disclosure of non-cash investing and financing transactions
Additions to property and equipment in accounts payable and accrued expenses	727	605
Proceeds from stock option exercises in other current assets	1,149	73
Public offering costs in other current assets, net of amounts in accounts payable and accrued expenses	$ 0	$ 158

Overview and Basis of Presentat

Overview and Basis of Presentation	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Overview and Basis of Presentation	Overview and Basis of Presentation References to Agios Throughout this Quarterly Report on Form 10-Q, “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 making transformative, first- or best-in-class medicines for the treatment of cancer and rare genetic diseases, or RGDs. To address both cancer and RGDs, 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. Basis of presentation The condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations, comprehensive loss, stockholders' equity and cash flows for the three months ended March 31, 2019 and 2018 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of our management, reflect all adjustments, which include only normal recurring adjustments, necessary to fairly state our financial position as of March 31, 2019, our results of operations and stockholders' equity for the three months ended March 31, 2019 and 2018, and cash flows for the three months ended March 31, 2019 and 2018. The financial data and the other financial information disclosed in these notes to the condensed consolidated financial statements related to the three-month period are also unaudited. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The year-end condensed consolidated balance sheet data was derived from our audited financial statements, but does not include all disclosures required by U.S. generally accepted accounting principles, or U.S. GAAP. Accordingly, the condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission, or the SEC, on February 14, 2019. Our condensed consolidated financial statements include our accounts and the accounts of our wholly owned subsidiaries, Agios Securities Corporation, Agios International Sarl, and Agios Limited. All intercompany transactions have been eliminated in consolidation. The condensed consolidated financial statements have been prepared in conformity with U.S. GAAP. Liquidity As of March 31, 2019, we had cash, cash equivalents and marketable securities of $707.8 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 will be sufficient to fund current operations for at least the next twelve months from the issuance date of these financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Leases In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2016-02, Leases (Topic 842) , which was codified as Accounting Standards Codification, or ASC, 842, Leases , and amended through subsequent ASUs. We adopted ASC 842 effective January 1, 2019 using the modified retrospective transition approach and elected the package of practical expedients, both provided for under ASU 2018-11, Leases (Topic 842): Targeted Improvements . The package of practical expedients 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, we chose not to separate the non-lease components from the lease components for our building leases and, instead, accounted for each non-lease component and lease component as a single component. Impact of Adoption of ASC 842 Upon adoption of ASC 842 on January 1, 2019, we recorded operating lease assets of $59.9 million and operating lease liabilities of $77.3 million. The adoption of ASC 842 did not have a material impact on our condensed consolidated statements of operations. Prior periods are presented in accordance with ASC 840, Leases . Leases Accounting Policy 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, plant, 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. Recent accounting pronouncements 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.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
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, directly or indirectly, for substantially the full term of the asset or liability. Level 3 – Unobservable inputs that reflect our own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date. The following table summarizes our cash equivalents and marketable securities measured at fair value on a recurring basis as of March 31, 2019 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 20,276 $ 38,170 $ — $ 58,446 Marketable securities: Certificates of deposit — 479 — 479 U.S. Treasuries — 183,760 — 183,760 Government securities — 115,630 — 115,630 Corporate debt securities — 304,479 — 304,479 Total cash equivalents and marketable securities $ 20,276 $ 642,518 $ — $ 662,794 Cash equivalents and marketable securities have been initially valued at the transaction price and subsequently, at the end of each reporting period, valued utilizing third-party pricing services or other market observable 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 March 31, 2019. There have been no changes to the valuation methods during the three months ended March 31, 2019. We evaluate transfers between levels at the end of each reporting period. There were no transfers between Level 1 and Level 2 during the three months ended March 31, 2019. We have no financial assets or liabilities that were classified as Level 3 at any point during the three months ended March 31, 2019.

Marketable Securities

Marketable Securities	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Our marketable securities are classified as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities , and 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 condensed consolidated statements of comprehensive loss, until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were no material realized gains or losses on marketable securities for the three months ended March 31, 2019 and 2018. Marketable securities at March 31, 2019 consisted of the following (in thousands): Amortized Unrealized Unrealized Fair Current: Certificates of deposit $ 480 $ — $ (1) $ 479 U.S. Treasuries 173,432 59 (125) 173,366 Government securities 69,419 16 (65) 69,370 Corporate debt securities 178,047 53 (201) 177,899 Non-current: U.S. Treasuries 10,434 10 (50) 10,394 Government securities 46,377 7 (124) 46,260 Corporate debt securities 126,641 185 (246) 126,580 Total marketable securities $ 604,830 $ 330 $ (812) $ 604,348 Marketable securities at December 31, 2018 consisted of the following (in thousands): Amortized Unrealized Unrealized Fair 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 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 marketable securities $ 737,090 $ 33 $ (2,204) $ 734,919 As of March 31, 2019 and December 31, 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 greater than one year, and (ii) we do not intend to liquidate within the next twelve months, although these funds are available for use and, therefore, are classified as available-for-sale. As of March 31, 2019 and December 31, 2018, we held 148 and 242 debt securities, respectively, that were in an unrealized loss position for less than one year. The aggregate fair value of debt securities in an unrealized loss position at March 31, 2019 and December 31, 2018 was $362.6 million and $639.3 million, respectively. There were no individual securities that were in a significant unrealized loss position as of March 31, 2019 and December 31, 2018. Given our intent and ability to hold such

Inventory

Inventory	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventory	Inventory Inventory, which consists of commercial supply of TIBSOVO® (ivosidenib), consists of the following (in thousands): March 31, December 31, Raw materials $ — $ — Work-in-process 2,267 788 Finished goods 61 81 Total inventory $ 2,328 $ 869

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases Our building leases comprise of office and laboratory space under non-cancelable operating leases. These lease agreements have remaining lease terms of six 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 is not reasonably certain. The lease agreements do not contain residual value guarantees. Operating lease costs for the three months ended March 31, 2019 were $3.1 million and cash paid for amounts included in the measurement of operating lease liabilities for the three months ended March 31, 2019 were $3.1 million. We have not entered into any material short-term leases or financing leases as of March 31, 2019. As of March 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): Remaining 2019 $ 8,576 2020 13,096 2021 13,434 2022 15,798 2023 17,040 2024 17,542 Thereafter 2,951 $ 88,437 In arriving at the operating lease liabilities as of March 31, 2019, we applied the weighted-average incremental borrowing rate of 5.3% over a weighted-average remaining lease term of 5.9 years. As of March 31, 2019, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities (in thousands): Undiscounted minimum rental commitments $ 88,437 Present value adjustment using incremental borrowing rate (13,303) Operating lease liabilities $ 75,134 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 $ 91,287 New lease arrangements 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 is expected to commence on May 1, 2019 and expire 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 will continue as set forth in the existing leases for those buildings.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consist of the following (in thousands): March 31, December 31, Accrued compensation $ 5,201 $ 20,843 Accrued research and development costs 23,588 14,777 Accrued professional fees 6,774 5,441 Accrued other 1,636 1,086 Total accrued expenses $ 37,199 $ 42,147

Product Revenue

Product Revenue	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Product Revenue	Product Revenue Our wholly owned product, TIBSOVO®, received approval from the U.S. Food and Drug Administration, or FDA, on July 20, 2018 for the treatment of adult patients with relapsed and refractory, or R/R, acute myeloid leukemia, or AML, with a susceptible isocitrate dehydrogenase 1, or IDH1, mutation. Upon FDA approval of TIBSOVO® in the U.S., we began generating product revenue from sales of TIBSOVO®. We sell 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. Reserves for Variable Consideration 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. In addition, we receive sales order management, data and distribution services from certain Customers. Chargebacks for fees 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. Total net product revenue from U.S. sales of TIBSOVO®, which is our only source of product revenue, was $9.1 million for the three months ended March 31, 2019. The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the three months ended March 31, 2019 (in thousands): Contractual Adjustments Government Rebates Returns Total Balance at December 31, 2018 $ 592 $ 325 $ 334 $ 1,251 Current provisions relating to sales in the current year 1,265 421 215 1,901 Adjustments relating to prior years 8 — — 8 Payments/returns relating to sales in the current year (756) — — (756) Payments/returns relating to sales in the prior years (598) (150) — (748) Balance at March 31, 2019 $ 511 $ 596 $ 549 $ 1,656 Total revenue-related reserves above, included in our condensed consolidated balance sheets, are summarized as follows (in thousands): March 31, December 31, Reduction of accounts receivable $ 303 $ 326 Component of accrued expenses 1,353 925 Total revenue-related reserves $ 1,656 $ 1,251 The following table presents changes in our contract assets during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Accounts receivable, net $ 5,076 $ 11,047 $ (11,768) $ 4,355

Collaboration and License Agree

Collaboration and License Agreements	3 Months Ended
	Mar. 31, 2019
Revenue Recognition and Deferred Revenue [Abstract]
Collaboration and License Agreements	Collaboration and License Agreements Accounting analysis and revenue recognition Our collaboration and license agreements typically involve us granting licenses of our intellectual property and performing research and development services in exchange of upfront fees, milestone payments and royalty payments. Since December 31, 2018, there have been no material changes to the key terms of our collaboration or license agreements. For further information on the terms and conditions of our existing collaboration and license agreements, please see the notes to the consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2018. Collaboration revenue 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 collaboration agreements under ASC 605-25, Multiple Element Arrangements. 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. Royalty revenue For arrangements that include sales-based royalties and sales-based milestones and in which the license is deemed to be the predominant item to which the royalties relate, we recognize royalty revenue upon the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Milestone revenue 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. Celgene Corporation We have entered into the following collaboration agreements, or collectively, the Collaboration Agreements, with Celgene Corporation, or Celgene, which 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. The discovery phase of the 2010 Agreement expired in April 2016. On August 15, 2016, we terminated the 2010 Agreement as to the program directed to the IDH1 target, for which ivosidenib is the lead development candidate. Accordingly, the sole program remaining under the 2010 Agreement is IDHIFA® (enasidenib), a co-commercialized licensed program for which Celgene leads and funds global development and commercialization activities. Under the remaining terms of the 2010 Agreement, we are eligible to receive up to $80.0 million in potential milestone payments for the enasidenib 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, and (ii) a $25.0 million milestone payment upon achievement of a specified ex-U.S. commercial milestone event, as well as royalties at tiered, low-double digit to mid-teen percentage rates on net sales of IDHIFA®. • 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. Under the AG-881 Agreements, we and Celgene split all worldwide development costs for vorasidenib, subject to specified exceptions. The AG-881 Agreements were terminated effective September 4, 2018, upon which we received sole global rights to vorasidenib. In connection with the termination of the AG-881 Agreements, Celgene will be eligible to receive royalties from us at a low single-digit percentage rate on worldwide net sales of products containing vorasidenib. • In May 2016 , we entered into a master research and collaboration agreement with Celgene, or the 2016 Agreement, focused on metabolic immuno-oncology, or MIO. The initial four one Collaboration revenue During the three months ended March 31, 2019 and 2018, we recognized the following collaboration revenue (in thousands): Three Months Ended March 31, 2019 2018 Services performed that were considered performance obligations as of the modification dates On-going research and development services $ 17,065 $ 6,364 Services performed that were not considered performance obligations as of the modification dates Development activities 854 981 Total collaboration revenue - related party $ 17,919 $ 7,345 The following table presents changes in our contract assets and liabilities during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Collaboration receivable – related party $ 2,462 $ 2,531 $ (2,674) $ 2,319 Royalty receivable – related party 2,234 2,200 (2,234) 2,200 Contract liabilities (2) Deferred revenue – related party, current and net of current portions 92,519 2,528 (17,919) 77,128 (1) Additions to contract assets relate to amounts billed to Celgene during the reporting period. Deductions to contract assets relate to collection of receivables during the reporting period. (2) Additions to contract liabilities relate to consideration from Celgene during the reporting period. Deductions to contract liabilities relate to deferred revenue recognized as revenue during the reporting period. During the three months ended March 31, 2019, we recognized the following as revenue due to changes in the contract liability balances (in thousands): Three Months Ended March 31, 2019 2018 Amounts included in the contract liability at the beginning of the period $ 16,410 $ 5,984 Performance obligations satisfied in previous periods 21 323 As of March 31, 2019, the aggregate amount of the transaction price allocated to performance obligations that are partially unsatisfied was $83.8 million. This amount is expected to be recognized as performance obligations are satisfied through March 2023. Royalty revenue 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. During the three months ended March 31, 2019 and 2018, we recognized the following as royalty revenue (in thousands): Three Months Ended March 31, 2019 2018 Royalty revenue – related party $ 2,200 $ 1,417 Milestone revenue No milestones were achieved during the three months ended March 31, 2019 or 2018. The next potential milestone expected to be achieved under our Collaboration Agreements is the first regulatory approval in any of China, Japan or a major European country. Achievement of this event would result in milestone payment of $35.0 million under the 2010 Agreement. CStone Pharmaceuticals In June 2018, we and CStone Pharmaceuticals, or CStone, entered into an exclusive license agreement, 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, or the CStone Territory. 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. CStone is responsible for all costs it incurs in developing, obtaining regulatory approval of, and commercializing ivosidenib in the CStone Territory, as well as certain costs incurred by us. Pursuant to 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 $412.0 million in milestone payments upon the achievement of certain development, regulatory and sales milestone events. We will also be entitled to receive tiered royalties, ranging from 15% to 19% percent, on annual net sales, if any, of ivosidenib in the CStone Territory. Collaboration revenue During the three months ended March 31, 2019, we recognized $1.0 million as collaboration revenue - other for certain other services provided by us to CStone, that were not considered performance obligations as of the inception date of the CStone Agreement. The following table presents changes in our contract assets during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Collaboration receivable - other $ 670 $ 970 $ — $ 1,640 (1) Additions to contract assets relate to amounts receivable from CStone. Deductions to contract assets relate to collection of receivables during the reporting period. As of March 31, 2019, the aggregate amount of the transaction price allocated to performance obligations that are partially unsatisfied was $0.7 million. Royalty revenue The license was determined to be the predominant item to which sales-based royalties and sales-based milestones relate. As the license was delivered in June 2018, we will recognize royalty revenue when the related sales occur. To date, no royalties have been received under the CStone Agreement. Milestone revenue No milestones were earned during the three months ended March 31, 2019. The next potential milestone expected to be achieved under the CStone Agreement is the dosing of the first patient in a local study in a hematological indication in mainland China. Achievement of this event will result in milestone payments of $5.0 million.

Share-Based Payments

Share-Based Payments	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments	Share-Based Payments 2013 Stock Incentive Plan 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, market-based stock units, or MSUs, and other stock-based awards. 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 remained outstanding and effective. As of March 31, 2019, the total number of shares reserved under the 2007 Plan and the 2013 Plan are 9,564,967, and we had 2,328,237 shares available for future issuance under the 2013 Plan. Stock options The following table presents stock option activity for the three months ended March 31, 2019: Number of Weighted-Average Exercise Price Outstanding at December 31, 2018 5,416,069 $ 60.10 Granted 1,357,189 57.47 Exercised (106,859) 39.45 Forfeited/Expired (183,526) 64.12 Outstanding at March 31, 2019 6,482,873 $ 59.77 Exercisable at March 31, 2019 3,269,079 $ 57.85 Vested and expected to vest at March 31, 2019 6,482,873 $ 59.77 At March 31, 2019, the total unrecognized compensation expense related to unvested stock option awards was $128.9 million, which we expect to recognize over a weighted-average period of approximately 3.0 years. Restricted stock units The following table presents RSU activity for the three months ended March 31, 2019: Number of Weighted-Average Grant Date Fair Value Unvested shares at December 31, 2018 532,144 $ 75.45 Granted 334,827 58.76 Vested (134,868) 66.98 Forfeited (22,941) 74.33 Unvested shares at March 31, 2019 709,162 $ 69.22 As of March 31, 2019, there was approximately $40.6 million of total unrecognized compensation expense related to RSUs, which we expect to recognize over a weighted-average period of approximately 2.1 years. Performance-based stock units The following table presents PSU activity for the three months ended March 31, 2019: Number of Weighted-Average Grant Date Fair Value Unvested shares at December 31, 2018 169,031 $ 52.67 Vested (167,031) 52.36 Unvested shares at March 31, 2019 2,000 $ 79.05 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. Performance-based vesting criteria primarily relate to events specific to our corporate goals. As of March 31, 2019, there was approximately $0.2 million of total unrecognized compensation expense related to PSUs with performance-based vesting criteria that are not considered probable of achievement. Market-based stock units The following table presents MSU activity for the three months ended March 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 — $ — Granted 42,695 41.50 Unvested shares at March 31, 2019 42,695 $ 41.50 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. Based on the simulation model, the aggregate grant date fair value of the share units was $1.8 million, which will be recognized over the remaining derived service period of 1.5 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 32,410 shares and 27,377 shares during the three months ended March 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 March 31, 2019, we had 199,146 shares available for future issuance under the 2013 ESPP. Stock-based compensation expense Stock-based compensation expense by award type included within the condensed consolidated statements of operations is as follows (in thousands): Three Months Ended March 31, 2019 2018 Stock options $ 13,046 $ 12,472 Restricted stock units 4,548 1,797 Employee stock purchase plan 328 253 Other stock awards 186 — Total stock-based compensation expense $ 18,108 $ 14,522 Expenses related to equity-based awards were allocated as follows in the condensed consolidated statements of operations (in thousands): Three Months Ended March 31, 2019 2018 Research and development expense $ 10,042 $ 8,640 Selling, general and administrative expense 8,066 5,882 Total stock-based compensation expense $ 18,108 $ 14,522

Loss per Share

Loss per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Loss per Share	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 met, and ESPP options are considered to be common stock equivalents, while PSUs and MSUs with performance and market vesting conditions, respectively, that were not met as of March 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 all periods presented. 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: Three Months Ended March 31, 2019 2018 Stock options 6,482,873 6,104,808 Restricted stock units 709,162 405,646 Employee stock purchase plan 6,778 5,289 Total common stock equivalents 7,198,813 6,515,743

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations, comprehensive loss, stockholders' equity and cash flows for the three months ended March 31, 2019 and 2018 are unaudited. The unaudited condensed consolidated financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of our management, reflect all adjustments, which include only normal recurring adjustments, necessary to fairly state our financial position as of March 31, 2019, our results of operations and stockholders' equity for the three months ended March 31, 2019 and 2018, and cash flows for the three months ended March 31, 2019 and 2018. The financial data and the other financial information disclosed in these notes to the condensed consolidated financial statements related to the three-month period are also unaudited. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other future annual or interim period. The year-end condensed consolidated balance sheet data was derived from our audited financial statements, but does not include all disclosures required by U.S. generally accepted accounting principles, or U.S. GAAP. Accordingly, the condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission, or the SEC, on February 14, 2019. Our condensed consolidated financial statements include our accounts and the accounts of our wholly owned subsidiaries, Agios Securities Corporation, Agios International Sarl, and Agios Limited. All intercompany transactions have been eliminated in consolidation. The condensed consolidated financial statements have been prepared in conformity with U.S. GAAP.
Leases	Leases In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2016-02, Leases (Topic 842) , which was codified as Accounting Standards Codification, or ASC, 842, Leases , and amended through subsequent ASUs. We adopted ASC 842 effective January 1, 2019 using the modified retrospective transition approach and elected the package of practical expedients, both provided for under ASU 2018-11, Leases (Topic 842): Targeted Improvements . The package of practical expedients 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, we chose not to separate the non-lease components from the lease components for our building leases and, instead, accounted for each non-lease component and lease component as a single component. Impact of Adoption of ASC 842 Upon adoption of ASC 842 on January 1, 2019, we recorded operating lease assets of $59.9 million and operating lease liabilities of $77.3 million. The adoption of ASC 842 did not have a material impact on our condensed consolidated statements of operations. Prior periods are presented in accordance with ASC 840, Leases . Leases Accounting Policy 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, plant, 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.
Recent accounting pronouncements	Recent accounting pronouncements 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.
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, 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.
Marketable Securities	Our marketable securities are classified as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities
Product Revenue	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. Reserves for Variable Consideration 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. In addition, we receive sales order management, data and distribution services from certain Customers. Chargebacks for fees 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.
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 met, and ESPP options are considered to be common stock equivalents, while PSUs and MSUs with performance and market vesting conditions, respectively, that were not met as of March 31, 2019 are not considered to be common stock equivalents.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 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 on a recurring basis as of March 31, 2019 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 20,276 $ 38,170 $ — $ 58,446 Marketable securities: Certificates of deposit — 479 — 479 U.S. Treasuries — 183,760 — 183,760 Government securities — 115,630 — 115,630 Corporate debt securities — 304,479 — 304,479 Total cash equivalents and marketable securities $ 20,276 $ 642,518 $ — $ 662,794

Marketable Securities (Tables)

Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of Marketable Securities	Marketable securities at March 31, 2019 consisted of the following (in thousands): Amortized Unrealized Unrealized Fair Current: Certificates of deposit $ 480 $ — $ (1) $ 479 U.S. Treasuries 173,432 59 (125) 173,366 Government securities 69,419 16 (65) 69,370 Corporate debt securities 178,047 53 (201) 177,899 Non-current: U.S. Treasuries 10,434 10 (50) 10,394 Government securities 46,377 7 (124) 46,260 Corporate debt securities 126,641 185 (246) 126,580 Total marketable securities $ 604,830 $ 330 $ (812) $ 604,348 Marketable securities at December 31, 2018 consisted of the following (in thousands): Amortized Unrealized Unrealized Fair 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 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 marketable securities $ 737,090 $ 33 $ (2,204) $ 734,919

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventory, which consists of commercial supply of TIBSOVO® (ivosidenib), consists of the following (in thousands): March 31, December 31, Raw materials $ — $ — Work-in-process 2,267 788 Finished goods 61 81 Total inventory $ 2,328 $ 869

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of Undiscounted Minimum Rental Commitments Under Topic 842	As of March 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): Remaining 2019 $ 8,576 2020 13,096 2021 13,434 2022 15,798 2023 17,040 2024 17,542 Thereafter 2,951 $ 88,437
Schedule of Difference Between Remaining Undiscounted Minimum Rental Commitments and Lease Liability	As of March 31, 2019, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities (in thousands): Undiscounted minimum rental commitments $ 88,437 Present value adjustment using incremental borrowing rate (13,303) Operating lease liabilities $ 75,134
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 $ 91,287

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2019
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following (in thousands): March 31, December 31, Accrued compensation $ 5,201 $ 20,843 Accrued research and development costs 23,588 14,777 Accrued professional fees 6,774 5,441 Accrued other 1,636 1,086 Total accrued expenses $ 37,199 $ 42,147

Product Revenue (Tables)

Product Revenue (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
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 three months ended March 31, 2019 (in thousands): Contractual Adjustments Government Rebates Returns Total Balance at December 31, 2018 $ 592 $ 325 $ 334 $ 1,251 Current provisions relating to sales in the current year 1,265 421 215 1,901 Adjustments relating to prior years 8 — — 8 Payments/returns relating to sales in the current year (756) — — (756) Payments/returns relating to sales in the prior years (598) (150) — (748) Balance at March 31, 2019 $ 511 $ 596 $ 549 $ 1,656
Schedule of Revenue Related Reserves	Total revenue-related reserves above, included in our condensed consolidated balance sheets, are summarized as follows (in thousands): March 31, December 31, Reduction of accounts receivable $ 303 $ 326 Component of accrued expenses 1,353 925 Total revenue-related reserves $ 1,656 $ 1,251
Schedule of Changes in Contract Assets and Liabilities, Product Revenue	The following table presents changes in our contract assets during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Accounts receivable, net $ 5,076 $ 11,047 $ (11,768) $ 4,355

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue Recognition and Deferred Revenue [Abstract]
Summary of Multiple-deliverable Arrangements Revenue, Allocated to Each Performance Obligation	During the three months ended March 31, 2019 and 2018, we recognized the following collaboration revenue (in thousands): Three Months Ended March 31, 2019 2018 Services performed that were considered performance obligations as of the modification dates On-going research and development services $ 17,065 $ 6,364 Services performed that were not considered performance obligations as of the modification dates Development activities 854 981 Total collaboration revenue - related party $ 17,919 $ 7,345
Schedule of Changes in Contract Assets and Liabilities	The following table presents changes in our contract assets and liabilities during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Collaboration receivable – related party $ 2,462 $ 2,531 $ (2,674) $ 2,319 Royalty receivable – related party 2,234 2,200 (2,234) 2,200 Contract liabilities (2) Deferred revenue – related party, current and net of current portions 92,519 2,528 (17,919) 77,128 (1) Additions to contract assets relate to amounts billed to Celgene during the reporting period. Deductions to contract assets relate to collection of receivables during the reporting period. (2) Additions to contract liabilities relate to consideration from Celgene during the reporting period. Deductions to contract liabilities relate to deferred revenue recognized as revenue during the reporting period. During the three months ended March 31, 2019, we recognized the following as revenue due to changes in the contract liability balances (in thousands): Three Months Ended March 31, 2019 2018 Amounts included in the contract liability at the beginning of the period $ 16,410 $ 5,984 Performance obligations satisfied in previous periods 21 323
Schedule of Royalty Revenue	During the three months ended March 31, 2019 and 2018, we recognized the following as royalty revenue (in thousands): Three Months Ended March 31, 2019 2018 Royalty revenue – related party $ 2,200 $ 1,417
Schedule of Changes in Contract Assets and Liabilities, CStone Agreement	The following table presents changes in our contract assets during the three months ended March 31, 2019 (in thousands): December 31, Additions Deductions March 31, Contract assets (1) Collaboration receivable - other $ 670 $ 970 $ — $ 1,640 (1) Additions to contract assets relate to amounts receivable from CStone. Deductions to contract assets relate to collection of receivables during the reporting period.

Share-Based Payments (Tables)

Share-Based Payments (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Company's Stock Option Activity	The following table presents stock option activity for the three months ended March 31, 2019: Number of Weighted-Average Exercise Price Outstanding at December 31, 2018 5,416,069 $ 60.10 Granted 1,357,189 57.47 Exercised (106,859) 39.45 Forfeited/Expired (183,526) 64.12 Outstanding at March 31, 2019 6,482,873 $ 59.77 Exercisable at March 31, 2019 3,269,079 $ 57.85 Vested and expected to vest at March 31, 2019 6,482,873 $ 59.77
Unvested Stock Unit Activity	The following table presents RSU activity for the three months ended March 31, 2019: Number of Weighted-Average Grant Date Fair Value Unvested shares at December 31, 2018 532,144 $ 75.45 Granted 334,827 58.76 Vested (134,868) 66.98 Forfeited (22,941) 74.33 Unvested shares at March 31, 2019 709,162 $ 69.22
Schedule of Performance-Based Units	The following table presents PSU activity for the three months ended March 31, 2019: Number of Weighted-Average Grant Date Fair Value Unvested shares at December 31, 2018 169,031 $ 52.67 Vested (167,031) 52.36 Unvested shares at March 31, 2019 2,000 $ 79.05
Schedule of Market-Based Units Activity	The following table presents MSU activity for the three months ended March 31, 2019: Number of Weighted-Average Unvested shares at December 31, 2018 — $ — Granted 42,695 41.50 Unvested shares at March 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 condensed consolidated statements of operations is as follows (in thousands): Three Months Ended March 31, 2019 2018 Stock options $ 13,046 $ 12,472 Restricted stock units 4,548 1,797 Employee stock purchase plan 328 253 Other stock awards 186 — Total stock-based compensation expense $ 18,108 $ 14,522
Summary of Allocated Stock-Based Compensation Expense	Expenses related to equity-based awards were allocated as follows in the condensed consolidated statements of operations (in thousands): Three Months Ended March 31, 2019 2018 Research and development expense $ 10,042 $ 8,640 Selling, general and administrative expense 8,066 5,882 Total stock-based compensation expense $ 18,108 $ 14,522

Loss per Share (Tables)

Loss per Share (Tables)	3 Months Ended
	Mar. 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: Three Months Ended March 31, 2019 2018 Stock options 6,482,873 6,104,808 Restricted stock units 709,162 405,646 Employee stock purchase plan 6,778 5,289 Total common stock equivalents 7,198,813 6,515,743

Overview and Basis of Present_2

Overview and Basis of Presentation - Additional Information (Details) $ in Millions	Mar. 31, 2019USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash, cash equivalents, and short-term investments	$ 707.8

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Schedule of Significant Accounting Policies [Line Items]
Operating lease assets	$ 57,768
Operating lease liabilities	$ 75,134
ASU 2016-02
Schedule of Significant Accounting Policies [Line Items]
Operating lease assets		$ 59,900
Operating lease liabilities		$ 77,300

Fair Value Measurements - Cash

Fair Value Measurements - Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring $ in Thousands	Mar. 31, 2019USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 58,446
Total cash equivalents and marketable securities	662,794
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	479
U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	183,760
Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	115,630
Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	304,479
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	20,276
Total cash equivalents and marketable securities	20,276
Level 1 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 1 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 1 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 1 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	38,170
Total cash equivalents and marketable securities	642,518
Level 2 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	479
Level 2 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	183,760
Level 2 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	115,630
Level 2 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	304,479
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0
Total cash equivalents and marketable securities	0
Level 3 | Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 3 | U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 3 | Government securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0
Level 3 | Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details)	Mar. 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 - Additio

Marketable Securities - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)security	Mar. 31, 2018USD ($)	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	148		242
Aggregate fair value of debt securities in an unrealized loss position	$ 362.6		$ 639.3

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 604,830	$ 737,090
Unrealized Gains	330	33
Unrealized Losses	(812)	(2,204)
Fair Value	604,348	734,919
Current: | Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	480	960
Unrealized Gains	0	0
Unrealized Losses	(1)	(4)
Fair Value	479	956
Current: | U.S. Treasuries
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	173,432	231,101
Unrealized Gains	59	7
Unrealized Losses	(125)	(228)
Fair Value	173,366	230,880
Current: | Government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	69,419	75,335
Unrealized Gains	16	0
Unrealized Losses	(65)	(121)
Fair Value	69,370	75,214
Current: | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	178,047	208,233
Unrealized Gains	53	0
Unrealized Losses	(201)	(483)
Fair Value	177,899	207,750
Non-current: | U.S. Treasuries
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,434	12,202
Unrealized Gains	10	4
Unrealized Losses	(50)	(125)
Fair Value	10,394	12,081
Non-current: | Government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	46,377	70,177
Unrealized Gains	7	10
Unrealized Losses	(124)	(188)
Fair Value	46,260	69,999
Non-current: | Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,641	139,082
Unrealized Gains	185	12
Unrealized Losses	(246)	(1,055)
Fair Value	$ 126,580	$ 138,039

Inventory - Schedule of Invento

Inventory - Schedule of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 0	$ 0
Work-in-process	2,267	788
Finished goods	61	81
Total inventory	$ 2,328	$ 869

Leases - Additional Information

Leases - Additional Information (Details) ft² in Thousands, $ in Millions	Apr. 11, 2019USD ($)ft²lease_term	Mar. 31, 2019USD ($)
Leases [Abstract]
Remaining lease terms		6 years
Operating lease cost		$ 3.1
Cash paid for amounts included in measurement of lease liabilities		$ 3.1
Weighted-average incremental borrowing rate		5.30%
Weighted-average remaining lease term		5 years 10 months 24 days
38 Sidney Street Lease | Subsequent Event
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 | Subsequent Event
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	Mar. 31, 2019USD ($)
Leases [Abstract]
Remaining 2019	$ 8,576
2020	13,096
2021	13,434
2022	15,798
2023	17,040
2024	17,542
Thereafter	2,951
Undiscounted minimum rental commitments	$ 88,437

Leases - Difference Between Rem

Leases - Difference Between Remaining Undiscounted Minimum Rental Commitments and Lease Liability (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Undiscounted minimum rental commitments	$ 88,437
Present value adjustment using incremental borrowing rate	(13,303)
Operating lease liabilities	$ 75,134

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 due under non-cancelable leases	$ 91,287

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued compensation	$ 5,201	$ 20,843
Accrued research and development costs	23,588	14,777
Accrued professional fees	6,774	5,441
Accrued other	1,636	1,086
Total accrued expenses	$ 37,199	$ 42,147

Product Revenue - Additional In

Product Revenue - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenue	$ 30,227	$ 8,762
Product revenue, net
Disaggregation of Revenue [Line Items]
Total revenue	$ 9,138	$ 0

Product Revenue - Schedule of P

Product Revenue - Schedule of Product Revenue Allowance and Reserves (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Contractual Adjustments [Roll Forward]
Contract adjustments, beginning balance	$ 592
Contractual adjustments, current provisions relating to sales in the current year	1,265
Contractual adjustments, adjustments relating to prior year	8
Contractual adjustments, payments/returns relating to sales in the current year	(756)
Contractual adjustments, payments/returns relating to sales in the prior year	(598)
Contract adjustments, ending balance	511
Government Rebates [Roll Forward]
Government rebates, beginning balance	325
Government rebates, current provisions relating to sales in the current year	421
Government rebates, adjustments relating to prior years	0
Government rebates, payments/returns relating to sales in the current year	0
Government rebates, payments/returns relating to sales in the prior years	(150)
Government rebates, ending balance	596
Product Returns [Roll Forward]
Returns, beginning balance	334
Returns, current provisions relating to sales in the current year	215
Returns, adjustments relating to prior years	0
Returns, payments/returns relating to sales in the current year	0
Returns, payments/returns relating to sales in the prior years	0
Returns, ending balance	549
Allowance for Doubtful Accounts Receivable [Roll Forward]
Total revenue-related reserves	1,656	$ 1,251
Total allowances and reserves, current provisions relating to sales in the current year	1,901
Total allowances and reserves, adjustments relating to prior years	8
Total allowances and reserves, payments/returns relating to sales in the current year	(756)
Total allowances and reserves, payments/returns relating to sales in the prior years	$ (748)

Product Revenue - Schedule of R

Product Revenue - Schedule of Revenue-Related Reserves (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Reduction of accounts receivable	$ 303	$ 326
Component of accrued expenses	1,353	925
Total revenue-related reserves	$ 1,656	$ 1,251

Product Revenue - Schedule of C

Product Revenue - Schedule of Changes in Contract Assets and Liabilities, Product Revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Contract assets
Contract assets, beginning balance	$ 5,076
Additions	11,047
Deductions	(11,768)
Contract assets, ending balance	$ 4,355

Collaboration and License Agr_3

Collaboration and License Agreements - Celegene Purchase Agreements (Details)	1 Months Ended
	May 31, 2016USD ($)extension	Mar. 31, 2019USD ($)	May 17, 2016USD ($)
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
2016 Agreement | Celgene
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of agreements	4 years
Extension period | extension	2
Number of allowable special case extensions | extension	4
Special case extension term	1 year
Upfront payment agreement extension fee receivable	$ 40,000,000
Option exercise fee receivable			$ 30,000,000
2016 Agreement | Celgene | Specified clinical development event
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	20,000,000
2016 Agreement | Celgene | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	169,000,000
2016 Agreement | Celgene | Maximum | Specified regulatory milestone events
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone-based receivable payments, eligible to be received	$ 149,000,000

Collaboration and License Agr_4

Collaboration and License Agreements - Collaboration Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 30,227	$ 8,762
On-going research and development services
Disaggregation of Revenue [Line Items]
Revenue	17,065	6,364
Development activities
Disaggregation of Revenue [Line Items]
Revenue	854	981
Collaboration revenue – related party
Disaggregation of Revenue [Line Items]
Revenue	$ 17,919	$ 7,345

Collaboration and License Agr_5

Collaboration and License Agreements - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Contract assets
Contract assets, beginning balance	$ 5,076
Additions	11,047
Deductions	(11,768)
Contract assets, ending balance	4,355
Contract liabilities
Additions	16,410	$ 5,984
Collaboration receivable – related party
Contract assets
Contract assets, beginning balance	2,462
Additions	2,531
Deductions	(2,674)
Contract assets, ending balance	2,319
Royalty receivable – related party
Contract assets
Contract assets, beginning balance	2,234
Additions	2,200
Deductions	(2,234)
Contract assets, ending balance	2,200
Deferred revenue – related party, current and net of current portions
Contract liabilities
Contract liabilities, beginning balance	92,519
Additions	2,528
Deductions	(17,919)
Contract liabilities, ending balance	$ 77,128

Collaboration and License Agr_6

Collaboration and License Agreements - Schedule of Revenues as a Result of Changes in Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue Recognition and Deferred Revenue [Abstract]
Amounts included in the contract liability at the beginning of the period	$ 16,410	$ 5,984
Performance obligations satisfied in previous periods	$ 21	$ 323

Collaboration and License Agr_7

Collaboration and License Agreements - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Remaining unsatisfied performance obligation	$ 83,800,000
Revenue	30,227,000	$ 8,762,000
Milestones achieved	0	0
2010 Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payment	35,000,000
Royalty revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue	$ 2,200,000	$ 1,417,000

Collaboration and License Agr_8

Collaboration and License Agreements - CStone Pharmaceuticals Purchase Agreement (Details) - USD ($)	1 Months Ended	3 Months Ended
	Jun. 30, 2018	Mar. 31, 2019	Mar. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		$ 30,227,000	$ 8,762,000
Remaining unsatisfied performance obligation		83,800,000
Milestones achieved		0	0
Collaboration revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		17,919,000	7,345,000
Royalty revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		2,200,000	$ 1,417,000
CStone Agreement | Collaboration revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		1,000,000
CStone Pharmaceuticals | CStone Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Initial payment received	$ 12,000,000
Potential future milestone payments		5,000,000
Remaining unsatisfied performance obligation		700,000
Milestones achieved		0
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]
Potential future milestone payments		412,000,000
Royalty percentage	19.00%
CStone Pharmaceuticals | CStone Agreement | Royalty revenue – related party
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue		$ 0

Collaboration and License Agr_9

Collaboration and License Agreements - Changes in Contract Assets and Liabilities Under CStone Agreement (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Contract assets
Contract assets, beginning balance	$ 5,076
Deductions	(11,768)
Contract assets, ending balance	4,355
Collaboration receivable - other | CStone Agreement
Contract assets
Contract assets, beginning balance	670
Additions	970
Deductions	0
Contract assets, ending balance	$ 1,640

Share-Based Payments - Addition

Share-Based Payments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to stock option	$ 40.6
Weighted-average period to recognize compensation expense (in years)	2 years 1 month 6 days
2007 Plan and 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (in shares)	9,564,967
2013 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	2,328,237
Total unrecognized compensation expense related to stock option	$ 128.9
Weighted-average period to recognize compensation expense (in years)	3 years
2013 Stock Incentive Plan | Performance-Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to stock option	$ 0.2
Market-Based Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate grant date fair value	$ 1.8
Derived service period to be recognized over	1 year 6 months
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	199,146
Shares issued under 2013 ESPP (in shares)	32,410	27,377
Opportunity to purchase of common stock (in shares)	327,272

Share-Based Payments - Summary

Share-Based Payments - Summary of Company's Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2019$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of Stock Options, Outstanding, Beginning balance (in shares) | shares	5,416,069
Number of Stock Options, Granted (in shares) | shares	1,357,189
Number of Stock Options, Exercised (in shares) | shares	(106,859)
Number of Stock Options, Forfeited/Expired (in shares) | shares	(183,526)
Number of Stock Options, Outstanding, Ending balance (in shares) | shares	6,482,873
Number of Stock Options, Exercisable (in shares) | shares	3,269,079
Number of Stock Options, Vested and expected to vest (in shares) | shares	6,482,873
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) | $ / shares	$ 60.10
Weighted-Average Exercise Price, Granted (in usd per share) | $ / shares	57.47
Weighted-Average Exercise Price, Exercised (in usd per share) | $ / shares	39.45
Weighted-Average Exercise Price, Forfeited/Expired (in usd per share) | $ / shares	64.12
Weighted-Average Exercise Price, Outstanding, Ending balance (in usd per share) | $ / shares	59.77
Weighted-Average Exercise Price, Exercisable (in usd per share) | $ / shares	57.85
Weighted-Average Exercise Price, Vested and expected to vest (in usd per share) | $ / shares	$ 59.77

Share-Based Payments - Summar_2

Share-Based Payments - Summary of Unvested RSUs Activity (Details) - Restricted stock units	3 Months Ended
	Mar. 31, 2019$ / sharesshares
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	334,827
Vested (in shares) | shares	(134,868)
Forfeited (in shares) | shares	(22,941)
Unvested shares end of period (in shares) | shares	709,162
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	58.76
Weighted-average grant date fair value, Vested (in usd per share) | $ / shares	66.98
Weighted-average grant date fair value, Forfeited (in usd per share) | $ / shares	74.33
Weighted-average grant date fair value, Unvested shares end of period (in usd per share) | $ / shares	$ 69.22

Share-Based Payments - Schedule

Share-Based Payments - Schedule of Performance-Based and Market- Based Units (Details)	3 Months Ended
	Mar. 31, 2019$ / sharesshares
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
Vested (in shares) | shares	(167,031)
Unvested shares end of period (in shares) | shares	2,000
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, Vested (in usd per share) | $ / shares	52.36
Weighted-average grant date fair value, Unvested shares end of period (in usd per share) | $ / shares	$ 79.05
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 - Schedu_2

Share-Based Payments - Schedule of Stock-Based Compensation Expense by Award Type Included Within the Condensed Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 18,108	$ 14,522
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	13,046	12,472
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,548	1,797
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	328	253
Other stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 186	$ 0

Share-Based Payments - Expenses

Share-Based Payments - Expenses Related to Equity-Based Awards (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 18,108	$ 14,522
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	10,042	8,640
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 8,066	$ 5,882

Loss per Share - Common Stock E

Loss per Share - Common Stock Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,198,813	6,515,743
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,482,873	6,104,808
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)	709,162	405,646
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,778	5,289

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