Agios Pharmaceuticals (AGIO) 10-Q 8 Aug 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Aug. 05, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
Trading Symbol	AGIO
Entity Registrant Name	AGIOS PHARMACEUTICALS INC
Entity Central Index Key	1,439,222
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		38,046,368

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 234,048	$ 71,764
Marketable securities	231,321	245,238
Collaboration receivable - related party	7,853	8,225
Tenant improvement and other receivables	2,014	3,374
Prepaid expenses and other current assets	8,923	8,728
Total current assets	484,159	337,329
Marketable securities	46,926	58,905
Property and equipment, net	25,134	23,220
Other assets	1,382	611
Total assets	557,601	420,065
Current liabilities:
Accounts payable	18,448	14,748
Accrued expenses	14,414	15,996
Deferred revenue - related party	31,469	19,665
Deferred rent	2,933	2,479
Total current liabilities	67,264	52,888
Deferred revenue, net of current portion - related party	183,540	4,699
Deferred rent, net of current portion	17,719	17,360
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized; no shares issued or outstanding at June 30, 2016 and December 31, 2015
Common stock, $0.001 par value; 125,000,000 shares authorized; 38,029,510 and 37,696,502 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	38	38
Additional paid-in capital	652,574	630,078
Accumulated other comprehensive income (loss)	297	(318)
Accumulated deficit	(363,831)	(284,680)
Total stockholders' equity	289,078	345,118
Total liabilities and stockholders' equity	$ 557,601	$ 420,065

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	38,029,510	37,696,502
Common stock, shares outstanding	38,029,510	37,696,502

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Collaboration revenue - related party	$ 6,978	$ 13,219	$ 38,259	$ 47,421
Operating expenses:
Research and development (net of $5,922 and $4,546 of cost reimbursement from related party for the three months ended June 30, 2016 and 2015, respectively, and $14,716 and $8,912 for the six months ended June 30, 2016 and 2015, respectively)	50,804	36,423	94,842	68,866
General and administrative	12,644	8,929	23,481	15,883
Total operating expenses	63,448	45,352	118,323	84,749
Loss from operations	(56,470)	(32,133)	(80,064)	(37,328)
Interest income	517	236	913	474
Net loss	$ (55,953)	$ (31,897)	$ (79,151)	$ (36,854)
Net loss per share - basic and diluted	$ (1.47)	$ (0.85)	$ (2.09)	$ (0.99)
Weighted-average number of common shares used in net loss per share - basic and diluted	37,956,383	37,329,220	37,910,233	37,272,300

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Cost reimbursement from related party	$ 5,922	$ 4,546	$ 14,716	$ 8,912

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (55,953)	$ (31,897)	$ (79,151)	$ (36,854)
Other comprehensive income:
Unrealized gain on available-for-sale securities	208	31	615	279
Comprehensive loss	$ (55,745)	$ (31,866)	$ (78,536)	$ (36,575)

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Operating activities
Net loss	$ (79,151)	$ (36,854)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,550	1,150
Stock-based compensation expense	20,103	13,237
Net amortization of premium and discounts on investments	330	319
Changes in operating assets and liabilities:
Collaboration receivable - related party	372	(3,982)
Tenant improvement and other receivables	1,360	(2,948)
Prepaid expenses and other assets	(1,129)	125
Accounts payable	3,755	(1,210)
Accrued expenses and other liabilities	(833)	(2,558)
Deferred rent	813	13,689
Refundable income taxes and income taxes payable		3,841
Deferred revenue - related party	190,645	(6,414)
Net cash provided by (used in) operating activities	138,815	(21,605)
Investing activities
Purchases of marketable securities	(226,289)	(106,205)
Proceeds from maturities and sales of marketable securities	252,468	198,078
Purchases of property and equipment	(5,267)	(14,679)
Net cash provided by investing activities	20,912	77,194
Financing activities
Payment of public offering costs		(207)
Net proceeds from stock option exercises and employee stock purchase plan	2,557	3,120
Net cash provided by financing activities	2,557	2,913
Net increase in cash and cash equivalents	162,284	58,502
Cash and cash equivalents at beginning of the period	71,764	14,031
Cash and cash equivalents at end of the period	234,048	72,533
Supplemental disclosure of non-cash investing and financing transactions
Additions to property, plant and equipment in accounts payable and accrued expenses	1,360	1,531
Vesting of restricted stock		(4)
Proceeds from stock option exercises in other current assets	$ 23	$ 3

Overview and Basis of Presentat

Overview and Basis of Presentation	6 Months Ended
	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Overview and Basis of Presentation	1. Overview and Basis of Presentation Overview Agios Pharmaceuticals, Inc. (“Agios” or the “Company”) is a biopharmaceutical company committed to the fundamental transformation of patients’ lives through scientific leadership in the field of cancer and rare genetic metabolic disorders. The Company has built a unique set of core capabilities in the field of cellular metabolism, with the goal of making transformative, first or best in class medicines. Agios’ therapeutic areas of focus are cancer and rare genetic metabolic disorders, which are a broad group of more than 600 rare genetic diseases caused by mutations, or defects, of single metabolic genes. In both of these areas, the Company is seeking to unlock the biology of cellular metabolism to create transformative therapies. The Company is located in Cambridge, Massachusetts. Basis of presentation The condensed consolidated interim balance sheet as of June 30, 2016, the condensed consolidated interim statements of operations and comprehensive loss for the three and six months ended June 30, 2016 and 2015 and cash flows for the six months ended June 30, 2016 and 2015, are unaudited. The unaudited condensed consolidated interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s condensed consolidated financial position as of June 30, 2016, its results of operations for the three and six months ended June 30, 2016 and June 30, 2015 and cash flows for the six months ended June 30, 2016 and 2015. The financial data and the other financial information disclosed in these notes to the condensed consolidated interim financial statements related to the three-month and six-month periods are also unaudited. The results of operations for the three and six months ended June 30, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other future annual or interim period. The condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015 that was filed with the Securities and Exchange Commission (the “SEC”) on February 26, 2016. The Company’s consolidated financial statements include the Company’s accounts and the accounts of the Company’s wholly owned subsidiaries, Agios Securities Corporation and Agios International Sarl. All intercompany transactions have been eliminated in consolidation. The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Recent Accounting Pronouncements	2. Summary of Significant Accounting Policies and Recent Accounting Pronouncements Significant accounting policies There have been no material changes to the significant accounting policies previously disclosed in the Annual Report on Form 10-K for the year ended December 31, 2015. Recent accounting pronouncements In May 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements – Going Concern (Subtopic 205-40) In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 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 the Company’s financial statements upon adoption.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company records cash equivalents and marketable securities at fair value. Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures Level 1 – Level 2 – Level 3 – The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of June 30, 2016 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 225,564 $ — $ — $ 225,564 Marketable securities: Certificates of deposit — 15,790 — 15,790 Government securities 169,179 — — 169,179 Corporate debt securities — 93,278 — 93,278 $ 394,743 $ 109,068 $ — $ 503,811 The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of December 31, 2015 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 59,332 $ — $ — $ 59,332 Marketable securities: Certificates of deposit — 11,243 — 11,243 Government securities 292,900 — — 292,900 $ 352,232 $ 11,243 $ — $ 363,475 Cash equivalents and marketable securities have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, 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 its validation procedures, the Company did not adjust or override any fair value measurements provided by the pricing services as of June 30, 2016 or December 31, 2015. The carrying amounts reflected in the condensed consolidated balance sheets for cash, collaboration receivable – related party, tenant improvement and other receivables, prepaid expenses and other current assets, other assets, accounts payable, and accrued expenses approximate their fair values at June 30, 2016 and December 31, 2015, due to their short-term nature. There have been no changes to the valuation methods during the three and six months ended June 30, 2016 or 2015. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1 and Level 2 during the three and six months ended June 30, 2016 and 2015. The Company had no financial assets or liabilities that were classified as Level 3 at any point during the three and six months ended June 30, 2016 or the year ended December 31, 2015.

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities Marketable securities at June 30, 2016 and December 31, 2015 consisted primarily of investments in certificates of deposit, government securities and corporate debt securities. Management determines the appropriate classification of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its marketable securities as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities Marketable securities at June 30, 2016 consist of the following (in thousands): Amortized Cost Unrealized Unrealized Fair Current: Certificates of deposit $ 5,040 $ 2 $ — $ 5,042 Government securities 158,571 91 (1 ) 158,661 Corporate debt securities 67,586 38 (6 ) 67,618 Non-current: Certificates of deposit 10,720 31 (3 ) 10,748 Government securities 10,511 7 — 10,518 Corporate debt securities 25,522 138 — 25,660 $ 277,950 $ 307 $ (10 ) $ 278,247 Marketable securities at December 31, 2015 consist of the following (in thousands): Amortized Cost Unrealized Unrealized Fair Current: Certificates of deposit $ 11,248 $ — $ (5 ) $ 11,243 Government securities 234,130 10 (145 ) 233,995 Non-current: Government securities 59,083 — (178 ) 58,905 $ 304,461 $ 10 $ (328 ) $ 304,143 At June 30, 2016 and December 31, 2015, the Company held both current and non-current investments. Investments classified as current have maturities of less than one year. Investments classified as non-current are those that (i) have a maturity of one to two years and (ii) management does not intend to liquidate within the next twelve months, although these funds are available for use and therefore classified as available-for-sale. The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the condensed consolidated interim statements of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. At June 30, 2016 and December 31, 2015, the Company held 13 and 74 debt securities that were in an unrealized loss position for less than one year, respectively. The aggregate fair value of debt securities in an unrealized loss position at June 30, 2016 and December 31, 2015 was $20.3 million and $207.4 million, respectively. There were no individual securities that were in a significant unrealized loss position as of June 30, 2016 and December 31, 2015. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. It is not more likely than not that the Company will be required to sell the securities, and the Company does not intend to do so prior to the recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of June 30, 2016 and December 31, 2015.

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration Agreements	5. Collaboration Agreements 2010 Agreement and amendments In April 2010, the Company entered into a collaboration agreement focused on cancer metabolism with Celgene Corporation and related subsidiaries (“Celgene”), a related party through ownership of the Company’s common stock. The agreement was amended in October 2011 and July 2014 (the agreement together with the amendments, the “2010 Agreement”). The goal of the collaboration is to discover, develop and commercialize disease-altering therapies in oncology based on the Company’s cancer metabolism research platform. The Company will initially lead discovery, preclinical and early clinical development for all cancer metabolism programs under the collaboration. The discovery phase of the 2010 Agreement expired in April 2016. The July 2014 amendment of the 2010 Agreement allowed for more flexibility in the design and conduct of phase 1 clinical trials and additional nonclinical and/or clinical activities that the Company agreed to perform at Celgene’s request. This amendment further modified the mechanism and timing for payments to be made with respect to such development activities. Under the 2010 Agreement, the Company is eligible to receive up to $120.0 million in potential milestone payments for the AG-221 program. The potential milestone payments are comprised of: (i) a $25.0 million milestone payment upon achievement of a specified clinical development milestone event, (ii) up to $70.0 million in milestone payments upon achievement of specified regulatory milestone events, and (iii) a $25.0 million milestone payment upon achievement of a specified commercial milestone event. In January 2016, the Company determined that a substantive clinical development milestone related to the AG-221 program was achieved and received a milestone payment of $25.0 million. Under the 2010 Agreement, the Company may also receive royalties at tiered, low- to mid-teen percentage rates on net sales. The royalty payments will be recognized as revenue in the period in which they are earned. To date, the Company has not earned any royalty payments under the 2010 Agreement. Unless terminated earlier by either party, the term of the 2010 Agreement will continue until the expiration of the last-to-expire of all royalty terms with respect to all royalty-bearing products. Celgene may terminate this agreement for convenience in its entirety or with respect to one or more programs upon ninety days written notice to the Company. If either party is in material breach and fails to cure such breach within the specified cure period, the other party may terminate the 2010 Agreement in its entirety or with respect to one or more programs; however, if such breach relates solely to a specific program, the non-breaching party may only terminate the agreement with respect to such program. Either the Company or Celgene may terminate the agreement in the event of specified insolvency events involving the other party. AG-881 Agreements On April 27, 2015, the Company entered into a joint worldwide development and profit share collaboration and license agreement with Celgene and the Company’s wholly owned subsidiary, Agios International Sarl, entered into a collaboration and license agreement with Celgene International II Sarl (collectively, the “AG-881 Agreements”). The AG-881 Agreements establish a worldwide collaboration focused on the development and commercialization of AG-881 products. Under the terms of the AG-881 Agreements, the Company received an initial payment of $10.0 million in May 2015 and is eligible to receive milestone-based payments described below. The Company and Celgene will equally split all worldwide development costs, subject to specified exceptions, as well as any profits from any net sales of, or commercialization losses related to, licensed AG-881 products. The Company is eligible to receive up to $70.0 million in potential milestone payments related to AG-881 under the AG-881 Agreements. The potential milestone payments are comprised of: (i) a $15.0 million milestone payment for filing of first NDA in a major market and (ii) up to $55.0 million in milestone payments upon achievement of specified regulatory milestone events. The Company may also receive royalties at tiered, low- to mid-teen percentage rates on net sales if it elects to not participate in the development and commercialization of AG-881. 2016 Agreement On May 17, 2016, Agios entered into a master research and collaboration agreement (the “2016 Agreement”) with Celgene and Celgene RIVOT Ltd. The 2016 Agreement establishes a new global collaboration focused on the research and development of immunotherapies against certain metabolic targets that exert their antitumor efficacy primarily via the immune system. In addition to new programs identified under the 2016 Agreement, Agios and Celgene have also agreed that all future development and commercialization of two programs that were conducted under the 2010 Agreement will now be governed by the 2016 Agreement. During the research term of the 2016 Agreement, the Company plans to conduct research programs focused on discovering compounds that are active against metabolic targets in the immuno-oncology, or IO, field. The initial four-year research term will expire on May 17, 2020. Celgene may extend the research term for up to two, or in specified cases, up to four, additional one-year terms. For each program under the 2016 Agreement, Agios may nominate compounds that meet specified criteria as development candidates, and, in limited circumstances, Celgene may also nominate compounds as development candidates for each such program. Celgene may designate the applicable program for further development following any such nomination, after which the Company may conduct, at the Company’s expense, additional pre-clinical and clinical development for such program through completion of an initial phase 1 dose escalation study. At the end of the research term, Celgene may designate for continued development up to three research programs for which development candidates have yet to be nominated, which are referred to as continuation programs. Agios may conduct further research and pre-clinical and clinical development activities on any continuation program, at the Company’s expense, through completion of an initial phase 1 dose escalation study. The Company has granted Celgene the right to obtain exclusive options to development and commercialization rights for each program that Celgene has designated for further development and for each continuation program. Celgene may exercise each such option beginning on the designation of a development candidate for such program (or on the designation of such program as a continuation program) and ending on the earlier of the end of a specified period after Celgene is furnished with specified information about the initial phase 1 dose escalation study for such program, or January 1, 2030. Research programs that have applications in the inflammation or autoimmune, or I&I, field that may result from the 2016 Agreement will also be subject to the exclusive options described above. Agios will retain rights to any program that Celgene does not designate for further development or as to which Celgene does not exercise its option. Under the terms of the 2016 Agreement, following Celgene’s exercise of its option with respect to a program, Agios or its affiliates and Celgene will enter into either a co-development and co-commercialization agreement if such program is in the IO field, or a license agreement if such program is in the I&I field. Under each co-development and co-commercial agreement, the Company and Celgene will co-develop and co-commercialize licensed products worldwide. Either Agios or Celgene will lead development and commercialization of licensed products for the United States and Celgene will lead development and commercialization of licensed products outside of the United States. Depending on the country, the Company and Celgene will each have the right to provide a portion of field-based marketing activities. Under each license agreement, Celgene will have the sole right to develop and commercialize licensed products worldwide. Co-development and co-commercialization agreements Under each co-development and co-commercialization agreement entered into under the 2016 Agreement, Agios and Celgene will split all post-option-exercise worldwide development costs, subject to specified exceptions, as well as any profits from any net sales of, or commercialization losses related to, licensed products. Celgene has the option to designate one program in the IO field as the 65/35 program, for which Celgene will be the lead party for the United States and will have a 65% profit or loss share. For programs in the IO field other than the 65/35 program, the Company and Celgene will alternate, on a program-by-program basis, being the lead party for the United States, with Agios having the right to be the lead party for the first such program, and Agios and Celgene will each have a 50% profit or loss share. The lead party for the United States will book commercial sales of licensed products, if any, in the United States, and Celgene will book commercial sales of licensed products, if any, outside of the United States. License agreements Under each license agreement under the 2016 Agreement, Celgene will be responsible for all post-option-exercise worldwide development and associated costs, subject to specified exceptions, as well as worldwide commercialization and associated costs, for licensed products. Financial terms Under the terms of the 2016 Agreement, Celgene made an initial upfront payment in the amount of $200 million. Celgene has specified rights to extend the research term for up to two, or in specified cases, up to four, additional years by paying a $40 million per-year extension fee. Celgene will pay an $8 million designation fee for each program that Celgene designates for further development and for each continuation program. For each program as to which Celgene exercises its option to develop and commercialize, subject to antitrust clearance, Celgene will pay an option exercise fee of at least $30 million for any designated development program and at least $35 million for any continuation programs. In certain cases, Celgene may exercise its option to develop and commercialize two early-stage I&I programs, prior to Celgene designating the program for further development, by paying an option exercise fee of $10 million. For the co-development and co-commercialization program Celgene designates the 65/35 program in the IO field, the Company is eligible to receive up to $209 million in potential milestone-based payments. The potential milestone-based payments for that program are comprised of: (i) a $25 million milestone-based payment upon achievement of a specified clinical development event and (ii) up to $184 million in milestone-based payments upon achievement of specified regulatory milestone events. For each co-development and co-commercialization program in the IO field other than the 65/35 program, Agios is eligible to receive up to $169 million in potential milestone-based payments payable for each program selected by Celgene. The potential milestone-based payments for such programs are comprised of: (i) a $20 million milestone-based payment upon achievement of a specified clinical development event and (ii) up to $149 million in milestone-based payments upon achievement of specified regulatory milestone events. For each licensed program in the I&I field, Agios is eligible to receive royalties at tiered, low double-digit percentage rates on Celgene’s net sales, if any, of the applicable licensed products and up to $386 million in potential milestone-based payments. The potential milestone-based payments for such programs are comprised of: (i) a $25 million milestone-based payment upon achievement of a specified clinical development event, (ii) up to $236 million in milestone-based payments upon achievement of specified regulatory milestone events, and (iii) up to $125 million in milestone-based payments upon achievement of specified commercial milestone events. Opt-out right Under the 2016 Agreement, the Company may elect to opt out of the cost and profit share under any co-development and co-commercialization agreement, subject to specified exceptions. Upon opting out, Celgene will have the sole right to develop, manufacture and commercialize the applicable licensed products throughout the world, at its cost, and the Company will undertake transitional activities reasonably necessary to transfer the development, manufacture and commercialization of such licensed products to Celgene, at the Company’s expense. Further, in lieu of the profit or loss sharing described above, Agios would be eligible to receive royalties at tiered, low double-digit percentage rates on Celgene’s net sales, if any, of the applicable licensed products. However, the Company would continue to be eligible to receive the developmental and regulatory milestone-based payments described above. Term The term of the 2016 Agreement commenced on May 17, 2016 and, if not terminated earlier, will expire upon later of the last-to-expire of the research term and all option exercise periods, or, if an option is exercised by Celgene for one or more programs in the collaboration, upon the termination or expiration of the last-to-exist co-development and co-commercialization agreement or license agreement, as applicable, for any such program. Termination Subject to specified exceptions, Celgene may terminate the 2016 Agreement in its entirety for any reason by providing Agios with prior written notice if there are no active co-development and co-commercialization agreements or license agreements in place or on a program-by-program basis if there are no active co-development and co-commercialization agreements or license agreements in place for the terminated program(s). Either party may terminate the 2016 Agreement for the insolvency of the other party. On a program-by-program basis, prior to the exercise of an option, either party may terminate the 2016 Agreement either in its entirety or with respect to one or more programs on prior written notice to the other party in the case of an uncured material breach by the other party that frustrates the fundamental purpose of the 2016 Agreement. Following the exercise of an option for a program, either party may terminate the 2016 Agreement with respect to such program if such party terminates the co-development and co-commercialization agreement or license agreement for such program for an uncured material breach by the other party that frustrates the fundamental purpose of such agreement. Either party may terminate a co-development and co-commercialization agreement or a license agreement upon the bankruptcy or insolvency of the other party. Either party also has the right to terminate the co-development and co-commercialization agreement or license agreement if the other party or any of its affiliates challenges the validity, scope or enforceability of or otherwise opposes, any patent included within the intellectual property rights licensed to the other party under such agreement. Exclusivity While any of Celgene’s options remain available under the 2016 Agreement, subject to specified exceptions, the Company may not directly or indirectly develop, manufacture or commercialize, outside of the 2016 Agreement, any therapeutic modality in the IO field or the I&I field with specified activity against a metabolic target. During the term of each co-development and co-commercialization agreement and license agreement, subject to specified exceptions, neither the Company nor Celgene may directly or indirectly develop, manufacture or commercialize outside of such agreement any therapeutic modality in any field with specified activity against the metabolic target that is the focus of the program licensed under such agreement. AG-120 letter agreement On May 17, 2016, Agios entered into a letter agreement with Celgene regarding AG-120 (the “AG-120 Letter Agreement”). Under the AG-120 Letter Agreement, Celgene and the Company have agreed to terminate the 2010 Agreement, effective as of August 15, 2016, as to the program directed to the IDH1 target, for which AG-120 is the lead development candidate. Under the 2010 Agreement, Celgene Corporation had held development and commercialization rights to the IDH1 program outside of the United States, and Agios holds such rights inside the United States. As a result of the AG-120 Letter Agreement, the Company will obtain global rights to AG-120 and the IDH1 program. Neither party will have any financial obligation, including royalties or milestone payments, to the other concerning AG-120 or the IDH1 program after final reconciliation of specified shared development costs. Under the AG-120 Letter Agreement, the parties have also agreed to conduct specified transitional activities in connection with the termination. In addition, pursuant to the AG-120 Letter Agreement, the parties are released from their exclusivity obligations under the 2010 Agreement with respect to the IDH1 program. The AG-120 Letter Agreement does not alter the global collaboration with Celgene Corporation pursuant to the collaboration and license agreements entered into with Celgene Corporation and Celgene International II Sarl on April 27, 2015 concerning AG-881, which is directed to both the IDH1 target and the IDH2 target. Accounting analysis and revenue recognition – collaboration revenue Pre-July 2014 Prior to the July 2014 amendment of the 2010 Agreement, the Company concluded that none of the identified deliverables had stand-alone value and, therefore, accounted for the deliverables as a single unit of accounting. The Company further concluded it was unable to estimate the fair value of the undelivered items within the 2010 Agreement. All considerations were recognized on a straight-line basis through the period over which the Company expected to fulfill its performance obligations (the performance period), which was initially determined to be six years. July 2014 – April 2015 The July 2014 amendment of the 2010 Agreement was determined to be a material modification of the 2010 Agreement due to the change in the total potential consideration that was more than insignificant and significant changes to certain of the deliverables in the arrangement. Upon concluding that the 2010 Agreement had been materially modified in July 2014, the Company identified the remaining deliverables under the arrangement and determined its best estimates of selling price for the undelivered elements as of the modification date as vendor specific objective evidence and third-party evidence were not available. The Company then allocated the total arrangement consideration, which included the remaining deferred revenue balance at the modification date and other consideration that was deemed to be determinable at the modification date, to each unit of accounting based on its best estimate of selling price. The difference between the total arrangement consideration and the best estimate of selling price of the undelivered items was recognized as revenue at the modification date. The undelivered items from the July 2014 modification, the related best estimate of selling price, the method of recognizing the allocated consideration, and the revenue recognized related to each unit of account through April 27, 2015, the effective date of the AG-881 Agreements was as follows: • License for the split licensed program – AG-120: The Company developed the best estimate of selling price of the license by probability weighting multiple cash flow scenarios using the income approach. There were significant judgments and estimates inherent in the determination of the best estimate of selling price of this unit of accounting. Should different reasonable assumptions be utilized, the best estimate of selling price and the associated revenue recognized would be different. The Company allocated $21.2 million to the license which was delivered in January 2015. During the period April 1, 2015 through April 27, 2015 and for the period January 1, 2015 through April 27, 2015, the Company recognized the non-contingent consideration allocated to this unit of accounting of $0.1 million and $15.8 million, respectively, as collaboration revenue. • Development services for five separate on-going phase 1 clinical trials (each of which is a separate unit of accounting): The Company developed the best estimate of selling price of the on-going phase 1 clinical trial development services of $50.8 million for all five studies using management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider, as well as internal full time equivalent costs to support the development services. The amount allocated to these units of accounting is recognized as revenue on a proportional performance basis as services are provided. As committed to on the date of the July 2014 amendment, the Company has completed services for three of the on-going phase 1 clinical trials and expected services for the remaining two on-going phase 1 clinical trials are expected to be performed through the second quarter of 2016. As additional consideration is earned and allocated to the three fully delivered units of accounting it is recognized immediately. During the period April 1, 2015 through April 27, 2015 and for the period January 1, 2015 through April 27, 2015, the Company recognized the non-contingent consideration allocated to this unit of accounting of $0.4 million and $14.7 million, respectively, as collaboration revenue. • On-going research and development: The Company developed the best estimate of selling price of the research and development services of $13.6 million using management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider. The amount allocated to this unit of accounting was recognized as revenue ratably over the performance period. During the period April 1, 2015 through April 27, 2015 and for the period January 1, 2015 through April 27, 2015, the Company recognized the non-contingent consideration allocated to this unit of accounting of $1.0 million and $5.0 million, respectively, as collaboration revenue. • Committee participation: The Company developed the best estimate of selling price of the committee participation services of $0.2 million using management’s best estimate of the anticipated participation hours multiplied by a market rate for comparable participants. The amount allocated to this unit of accounting was recognized as revenue ratably over the performance period. During the period April 1, 2015 through April 27, 2015 and for the period January 1, 2015 through April 27, 2015, the Company recognized the non-contingent consideration allocated to this unit of accounting of $0.1 million as collaboration revenue. In December 2014, Celgene elected to extend the term of the discovery period over which the Company was providing on-going research and development services from five to six years, to April 2016. As a result of the extension, the Company received a $20.0 million extension payment from Celgene in May 2015. The Company evaluated the extension and concluded that upon exercise it is obligated to provide its committee participation and research and development services for a period of one year from April 2015 through April 2016, and as such revenue should be recognized ratably over the performance period of April 2015 to April 2016 as services are rendered. The Company recognized revenue of $0.7 million related to this substantive option during the period April 16, 2015 through April 27, 2015. Beginning in the first quarter of 2015, the Company and Celgene agreed to plans to advance AG-221 into later stage development studies. Pursuant to the terms of the 2010 Agreement, the parties agreed to transition primary development responsibilities for AG-221 to Celgene for later stage development at which point Celgene became the lead development party for AG-221. During the transition, the Company continued to manage certain arrangements with third-party service providers whose contracts were assigned to Celgene. The Company determined it is no longer the primary obligor of these arrangements and, when considering the other factors included within ASC 605-45, Revenue Recognition – Principal Agent Considerations During the period January 1, 2015 through April 27, 2015, the execution date of the AG-881 Agreements, the Company performed planning services on behalf of Celgene related to an expanded phase 1 clinical trial of AG-221. The Company determined the work represented a substantive option under the 2010 Agreement. The Company also determined it is not the primary obligor of the underlying third-party contracts and determined that reimbursements of amounts incurred under the contracts should be reported on a net basis in research and development expense. Reimbursements of services performed directly by the Company are presented on a gross basis as collaboration revenue. During the period April 1, 2015 through April 27, 2015 and for the period January 1, 2015 through April 27, 2015, the Company recognized $0.3 million and $0.4 million, respectively, in revenues and recorded $0.3 million and $0.9 million, respectively, as a reduction in research and development costs related to these services. Costs reimbursed for services performed directly by the Company are presented as collaboration revenues. April 2015 – May 2016 The AG-881 Agreements, executed on April 27, 2015, were determined to be a modification of the 2010 Agreement due to the AG-881 Agreements including a compound originally identified within the 2010 Agreement. As a result of the modification the Company identified the remaining deliverables under the 2010 Agreement and the AG-881 Agreements with Celgene and determined the best estimate of selling price for the undelivered elements as of the modification date. The Company then allocated the total arrangement consideration, which included the remaining deferred revenue balance at the modification date, the initial payment of $10.0 million under the AG-881 Agreements and other consideration under the 2010 Agreement and the AG-881 Agreements that was deemed to be determinable at the modification date, to each unit of accounting relative to its best estimate of selling price. The undelivered items, which are each considered by the Company to have stand-alone value and therefore are separate units of accounting, the related best estimate of selling price at April 27, 2015, and the method of recognizing the allocated consideration, for each unit of accounting are as follows: • Licenses for the AG-881 program: The Company developed the best estimate of selling price of the U.S. license and the rest of world license by probability weighting multiple cash flow scenarios using the income approach. Management estimates within the models include the expected, probability-weighted net profits from estimated future sales, an estimate of the direct cost incurred to generate future cash flows, a discount rate and other business forecast factors. There are significant judgments and estimates inherent in the determination of the best estimate of selling price of these units of accounting. These judgments and estimates include assumptions regarding future operating performance, the timelines of the clinical trials and regulatory approvals and the estimated patient populations. Should different reasonable assumptions be utilized, the best estimate of selling price and the associated revenue recognized would be different. The Company developed a best estimate of selling price of the licenses of $33.2 million. The Company recognizes the non-contingent consideration allocated to these units of accounting upon delivery of the licenses to Celgene which occurred immediately upon the execution of the AG-881 Agreements. During the period April 1, 2016 through May 17, 2016, the effective date of the 2016 Agreement, and for the period January 1, 2016 through May 17, 2016, the Company recognized the non-contingent consideration allocated to this unit of accounting of $0.5 million and $1.4 million, respectively, as collaboration revenue. For the period April 27, 2015 through June 30, 2015, the Company recognized the non-contingent consideration allocated to this unit of accounting of $8.8 million as collaboration revenue. • Four separate on-going development services for which the Company determined it is acting as the principal of all development activities (each of which is a separate unit of accounting): The Company developed the best estimate of selling price for all four of the on-going development services of $12.7 million using management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider, as well as internal full time equivalent costs to support the development services. The estimated costs were determined to represent management’s best estimate of the price these services could be sold for separately. The amount allocated to these units of accounting is being recognized as revenue on a proportional performance basis as services are provided. The Company expects the services to be performed through 2017. When considering the factors included within ASC 605-45, the Company determined it is the principal of all development activities and is required to present reimbursement of amounts incurred for these services as revenue. During the period April 1, 2016 through May 17, 2016 and for the period January 1, 2016 through May 17, 2016, the Company recognized the non-contingent consideration allocated to these units of accounting of $0.6 million and $1.7 million, respectively, as collaboration revenue. For the period April 27, 2015 through June 30, 2015, the Company recognized the non-contingent consideration allocated to these units of accounting of $0.6 million as collaboration revenue. • Four separate on-going development services for which the Company determined it is not acting as the principal of all development activities (each of which is a separate unit of accounting): The Company developed the best estimate of selling price for all four of the on-going development services of $97.3 million using management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider, as well as internal full time equivalent costs to support the development services. The estimated costs were determined to represent management’s best estimate of the price these services could be sold for separately. The amount allocated to these units of accounting is being recognized on a proportional performance basis as services are provided. The Company expects the services to be performed through 2017. When considering the factors included within ASC 605-45, the Company determined it is not the principal of all development activities and is required to present reimbursement of amounts incurred for these services on a net basis as a reduction of research and development expenses. During the period April 1, 2016 through May 17, 2016 and for the period January 1, 2016 through May 17, 2016, the Company recognized the non-contingent consideration allocated to these units of accounting of $2.6 million and $7.5 million, respectively, as a reduction of research and development costs related to these services. For the period April 27, 2015 through June 30, 2015, the Company recognized the non-contingent consideration allocated to these units of accounting of $3.4 million as a reduction of research and development costs related to these services. • On-going research and development: The Company developed the best estimate of selling price of the research and development services of $30.5 million using management’s best estimate of the cost of obtaining these services at arm’s length from a third-party provider. The amount allocated to this unit of accounting is being recognized as revenue ratably over the performance period through April 2016. During the period April 1, 2016 through May 17, 2016 and for the period January 1, 2016 through May 17, 2016, the Company recognized the non-contingent consideration allocated to this unit of accounting of $1.0 million and $4.6 million, respectively, as collaboration revenue. For the period April 27, 2015 through June 30, 2015,

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2016
Payables and Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consist of the following (in thousands): June 30, December 31, Accrued compensation $ 6,352 $ 7,005 Accrued contracted research and development costs 6,214 7,449 Accrued professional fees 1,641 228 Accrued other 207 1,314 Total $ 14,414 $ 15,996

Share-Based Payments

Share-Based Payments	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments	7. Share-Based Payments 2013 Stock Incentive Plan In June 2013, the Company’s Board of Directors adopted and, in July 2013, the Company’s stockholders approved the 2013 Stock Incentive Plan (the “2013 Plan”). The 2013 Plan became effective upon the closing of the Company’s Initial Public Offering, or IPO, and provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Following the adoption of the 2013 Plan, the Company granted no further stock options or other awards under the 2007 Stock Incentive Plan, or 2007 Plan. Any options or awards outstanding under the 2007 Plan at the time of adoption of the 2013 Plan remain outstanding and effective. As of June 30, 2016, the total number of shares reserved under the 2007 Plan and the 2013 Plan are 6,546,275 and the Company had 981,516 shares available for future issuance under such plans. The 2013 Plan provides for an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2014 and continuing until the expiration of the 2013 Plan, equal to the lesser of (i) 2,000,000 shares of common stock, (ii) 4% of the outstanding shares of common stock on such date or (iii) an amount determined by the Company’s Board of Directors. On January 1, 2016 and 2015, the annual increase for the 2013 Plan resulted in an additional 1,507,860 shares and 1,484,020 shares, respectively, authorized for issuance. The following table summarizes all stock option activity for the six months ended June 30, 2016: Number of Weighted- Weighted- Aggregate Outstanding at December 31, 2015 4,618,697 $ 44.45 7.49 $ 153,573 Granted 1,155,940 42.61 Exercised (313,183 ) 6.36 Forfeited/expired (78,265 ) 73.33 Outstanding at June 30, 2016 5,383,189 $ 45.85 7.63 $ 73,370 Exercisable at June 30, 2016 2,452,292 $ 30.04 6.26 $ 58,983 Vested and expected to vest at June 30, 2016 5,037,783 $ 46.38 7.60 $ 67,811 The weighted-average grant date fair value of options granted was $31.89, $64.19, $27.17 and $67.57 during the three months ended June 30, 2016 and 2015 and six months ended June 30, 2016 and 2015, respectively. The total intrinsic value of options exercised was $5.3 million and $11.3 million during the three months ended June 30, 2016 and 2015, respectively, and $15.3 million and $29.4 million during the six months ended June 30, 2016 and 2015, respectively. At June 30, 2016, the total unrecognized compensation expense related to unvested stock option awards, including estimated forfeitures, was $95.4 million, which the Company expects to recognize over a weighted-average period of approximately 2.70 years. The Company also has unrecognized stock-based compensation expense of $8.2 million related to stock options and performance-based stock units both with performance-based vesting criteria that are not considered probable of achievement as of June 30, 2016. Restricted stock units The Company may grant awards of restricted stock units (“RSUs”) to non-employee directors, members of the management team and employees on a discretionary basis pursuant to the 2013 Plan. Each RSU entitles the holder to receive, at the end of each vesting period, a specified number of shares of the Company’s common stock. During the three months ended March 31, 2016, the Company granted 58,800 RSUs to various employees; no RSUs were granted during the three months ended June 30, 2016. The Company granted 15,000 RSUs during the three and six months ended June 30, 2015. The Company recorded stock-based compensation expense related to RSUs of $0.5 million and $0.2 million for the three months ended June 30, 2016 and 2015, respectively, and stock-based compensation expenses of $0.9 million and $0.3 million for the six months ended June 30, 2016 and 2015, respectively. These amounts are included in the total stock-based compensation expense disclosed below. As of June 30, 2016, there was approximately $2.6 million of total unrecognized compensation expense related to RSUs, which is expected to be recognized over a weighted-average period of 1.5 years. The following table presents RSU activity for the six months ended June 30, 2016: Number of Weighted-average Unvested shares at December 31, 2015 15,000 $ 122.22 Granted 58,800 39.76 Vested (7,500 ) 122.22 Unvested shares at June 30, 2016 66,300 $ 49.09 Performance-based stock options During the three and six months ended June 30, 2016 and 2015, no options to purchase shares of common stock that contain performance-based or a combination of performance-based and service-based vesting criteria were granted by the Company. However, certain performance-based stock options issued in prior periods were still outstanding as of June 30, 2016. Performance-based vesting criteria for options primarily relate to milestone events specific to the Company’s corporate goals, including but not limited to certain preclinical, clinical and regulatory development milestones related to the Company’s product candidates. Stock-based compensation expense associated with these performance-based stock options is recognized if the performance condition is considered probable of achievement using management’s best estimates. As of June 30, 2016, certain of the performance-based milestones had been achieved. The achievements of certain other milestones have been deemed probable and therefore the related expense either has been fully recognized or is being recognized over the remaining service period. The achievement of the remaining milestones was deemed to be not probable as of June 30, 2016 and, therefore, no expense has been recognized related to these awards. During the three and six months ended June 30, 2015, the Company recognized stock-based compensation expense of $0.1 million and $0.3 million, respectively, related to stock options with performance-based vesting criteria. During the three and six months ended June 30, 2016, the Company did not recognize any stock-based compensation expense related to stock options with performance-based vesting criteria. Performance-based stock units In December 2015, pursuant to the 2013 Plan, the Company granted 100,270 performance stock units (“PSUs”) to certain employees and, in February 2016, the Company granted 15,000 PSUs to one employee. Each PSU entitles the holder to receive, at the achievement of the performance-based and service-based criteria, a specified number of shares of the Company’s stock. Performance-based vesting criteria primarily relate to milestone events specific to the Company’s corporate goals, specifically regulatory development milestones related to the Company’s product candidates. Stock-based compensation expense associated with these PSUs is recognized if the performance condition is considered probable of achievement using management’s best estimates. As of June 30, 2016, these milestones were not probable and, therefore, no expense has been recognized related to these awards. No such awards were granted during the six months ended June 30, 2015. 2013 Employee Stock Purchase Plan In June 2013, the Company’s Board of Directors adopted, and in July 2013 the Company’s stockholders approved, the 2013 Employee Stock Purchase Plan (the “2013 ESPP”). The 2013 ESPP is administered by the Company’s Board of Directors or by a committee appointed by the Company’s Board of Directors. Under the 2013 ESPP, each offering period is six months, at the end of which employees may purchase shares of common stock through payroll deductions made over the term of the offering period. The per-share purchase price at the end of each offering period is equal to 85% of the closing price of one share of the Company’s common stock at the beginning or end of the offering period, whichever is lower, subject to Internal Revenue Service limits. The Company issued 12,327 shares and 10,664 shares during the six months ended June 30, 2016 and 2015, respectively, under the 2013 ESPP. The Company did not issue any shares during the three months ended June 30, 2016 and 2015. The 2013 ESPP provides participating employees with the opportunity to purchase up to an aggregate of 327,272 shares of the Company’s common stock. As of June 30, 2016, the Company had 297,795 shares available for future issuance under the 2013 ESPP. The Company recorded $0.2 million and $0.1 million of stock-based compensation expense for the three months ended June 30, 2016 and 2015, respectively, and $0.3 million and $0.2 million of stock-based compensation expense for the six months ended June 30, 2016 and 2015, respectively, related to the 2013 ESPP. Stock-based compensation expense During the three and six months ended June 30, 2016 and 2015, the Company recorded stock-based compensation expense for employee and non-employee stock options, restricted stock units, restricted stock, performance-based stock options, performance-based stock units and the employee stock purchase plan shares. Expenses related to these equity-based awards were allocated as follows in the condensed consolidated interim statements of operations (in thousands): Three Months Ended Six Months Ended June 30, 2016 2015 2016 2015 Research and development expense $ 6,561 $ 4,569 $ 12,089 $ 7,180 General and administrative expense 4,435 3,608 8,014 6,057 $ 10,996 $ 8,177 $ 20,103 $ 13,237 The fair value of each stock option granted to employees is estimated on the date of grant using the Black-Scholes option-pricing model. For non-employees, the fair value of each stock option is estimated on each vesting and reporting date using the Black-Scholes option-pricing model. The following table summarizes the weighted average assumptions used in calculating the grant date fair value of the awards: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Risk-free interest rate 1.38 % 1.71 % 1.41 % 1.71 % Expected dividend yield — — — — Expected term (in years) 5.89 5.88 6.04 6.03 Expected volatility 72.53 % 68.93 % 71.72 % 70.02 %

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes In January 2014, the Company paid $6.0 million as payment in full of its U.S. federal income tax liability related to the year ended December 31, 2011, including $1.5 million of interest and penalties accrued. The Company filed a carryback claim to apply the net losses incurred during the year ended December 31, 2013 against the previous taxable income. The amount to be refunded by the Internal Revenue Service (“IRS”) was recorded as refundable income taxes as of December 31, 2014. During the three months ended March 31, 2015, the Company received the balance of the refundable income tax. There was no (benefit) provision for income taxes during the three and six months ended June 30, 2016 and 2015. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. The Company evaluated whether any uncertain tax positions arise from commencing operations of its wholly owned subsidiary, Agios International Sarl, and determined no uncertain tax positions existed. As of June 30, 2016 and December 31, 2015, the Company did not have any uncertain tax positions.

Loss per Share

Loss per Share	6 Months Ended
	Jun. 30, 2016
Earnings Per Share [Abstract]
Loss per Share	9. Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the dilutive net loss per share calculation, stock options, restricted stock units, unvested restricted stock and employee stock purchase plan options are considered to be common stock equivalents but are excluded from the calculation of diluted net loss per share as their effect would be anti-dilutive; therefore, basic and diluted net loss per share were the same for all periods presented. The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect: Three and Six Months Ended June 30, 2016 2015 Stock options 5,383,189 4,687,805 Restricted stock units 66,300 25,000 Unvested restricted stock — 2,841 Employee stock purchase plan options 15,917 3,941 5,465,406 4,719,587

Summary of Significant Accoun17

Summary of Significant Accounting Policies and Recent Accounting Pronouncements (Policies)	6 Months Ended
	Jun. 30, 2016
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies There have been no material changes to the significant accounting policies previously disclosed in the Annual Report on Form 10-K for the year ended December 31, 2015.
Recent accounting pronouncements	Recent accounting pronouncements In May 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements – Going Concern (Subtopic 205-40) In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 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 the Company’s financial statements upon adoption.
Fair Value Measurements and Disclosures	The Company records cash equivalents and marketable securities at fair value. Accounting Standards Codification (“ASC”) 820, Fair Value Measurements and Disclosures Level 1 – Level 2 – Level 3 –
Investments - Debt and Equity Securities	Marketable securities at June 30, 2016 and December 31, 2015 consisted primarily of investments in certificates of deposit, government securities and corporate debt securities. Management determines the appropriate classification of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its marketable securities as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the condensed consolidated interim statements of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis	The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of June 30, 2016 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 225,564 $ — $ — $ 225,564 Marketable securities: Certificates of deposit — 15,790 — 15,790 Government securities 169,179 — — 169,179 Corporate debt securities — 93,278 — 93,278 $ 394,743 $ 109,068 $ — $ 503,811 The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of December 31, 2015 (in thousands): Level 1 Level 2 Level 3 Total Cash equivalents $ 59,332 $ — $ — $ 59,332 Marketable securities: Certificates of deposit — 11,243 — 11,243 Government securities 292,900 — — 292,900 $ 352,232 $ 11,243 $ — $ 363,475

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2016
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable securities at June 30, 2016 consist of the following (in thousands): Amortized Cost Unrealized Unrealized Fair Current: Certificates of deposit $ 5,040 $ 2 $ — $ 5,042 Government securities 158,571 91 (1 ) 158,661 Corporate debt securities 67,586 38 (6 ) 67,618 Non-current: Certificates of deposit 10,720 31 (3 ) 10,748 Government securities 10,511 7 — 10,518 Corporate debt securities 25,522 138 — 25,660 $ 277,950 $ 307 $ (10 ) $ 278,247 Marketable securities at December 31, 2015 consist of the following (in thousands): Amortized Cost Unrealized Unrealized Fair Current: Certificates of deposit $ 11,248 $ — $ (5 ) $ 11,243 Government securities 234,130 10 (145 ) 233,995 Non-current: Government securities 59,083 — (178 ) 58,905 $ 304,461 $ 10 $ (328 ) $ 304,143

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2016
Payables and Accruals [Abstract]
Summary of Accrued Expenses	Accrued expenses consist of the following (in thousands): June 30, December 31, Accrued compensation $ 6,352 $ 7,005 Accrued contracted research and development costs 6,214 7,449 Accrued professional fees 1,641 228 Accrued other 207 1,314 Total $ 14,414 $ 15,996

Share-Based Payments (Tables)

Share-Based Payments (Tables)	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Company's Stock Option Activity	The following table summarizes all stock option activity for the six months ended June 30, 2016: Number of Weighted- Weighted- Aggregate Outstanding at December 31, 2015 4,618,697 $ 44.45 7.49 $ 153,573 Granted 1,155,940 42.61 Exercised (313,183 ) 6.36 Forfeited/expired (78,265 ) 73.33 Outstanding at June 30, 2016 5,383,189 $ 45.85 7.63 $ 73,370 Exercisable at June 30, 2016 2,452,292 $ 30.04 6.26 $ 58,983 Vested and expected to vest at June 30, 2016 5,037,783 $ 46.38 7.60 $ 67,811
Unvested Stock Unit Activity	The following table presents RSU activity for the six months ended June 30, 2016: Number of Weighted-average Unvested shares at December 31, 2015 15,000 $ 122.22 Granted 58,800 39.76 Vested (7,500 ) 122.22 Unvested shares at June 30, 2016 66,300 $ 49.09
Stock-Based Compensation Expense for Employee and Non-Employee Stock Options, Restricted Stock Units, Restricted Stock, Performance-Based Stock Options, Performance-Based Stock Units and the Employee Stock Purchase Plan Shares	During the three and six months ended June 30, 2016 and 2015, the Company recorded stock-based compensation expense for employee and non-employee stock options, restricted stock units, restricted stock, performance-based stock options, performance-based stock units and the employee stock purchase plan shares. Expenses related to these equity-based awards were allocated as follows in the condensed consolidated interim statements of operations (in thousands): Three Months Ended Six Months Ended June 30, 2016 2015 2016 2015 Research and development expense $ 6,561 $ 4,569 $ 12,089 $ 7,180 General and administrative expense 4,435 3,608 8,014 6,057 $ 10,996 $ 8,177 $ 20,103 $ 13,237
Schedule of Grant Date Fair Value Option Award Weighted Average Assumptions Used	The following table summarizes the weighted average assumptions used in calculating the grant date fair value of the awards: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Risk-free interest rate 1.38 % 1.71 % 1.41 % 1.71 % Expected dividend yield — — — — Expected term (in years) 5.89 5.88 6.04 6.03 Expected volatility 72.53 % 68.93 % 71.72 % 70.02 %

Loss per Share (Tables)

Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2016
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 for the periods indicated because including them would have had an anti-dilutive effect: Three and Six Months Ended June 30, 2016 2015 Stock options 5,383,189 4,687,805 Restricted stock units 66,300 25,000 Unvested restricted stock — 2,841 Employee stock purchase plan options 15,917 3,941 5,465,406 4,719,587

Overview and Basis of Present23

Overview and Basis of Presentation - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2016Diseases
Minimum [Member]
Basis Of Presentation [Line Items]
Number of rare genetic disease under entity therapeutic group	600

Fair Value Measurements - Cash

Fair Value Measurements - Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 225,564	$ 59,332
Cash equivalents and marketable securities, total	503,811	363,475
Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	15,790	11,243
Government Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	169,179	292,900
Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	93,278
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	225,564	59,332
Cash equivalents and marketable securities, total	394,743	352,232
Level 1 [Member] | Government Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	169,179	292,900
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	109,068	11,243
Level 2 [Member] | Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	15,790	$ 11,243
Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents and marketable securities, total	$ 93,278

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets or liabilities that were classified as Level 3	$ 0
Transfers of assets from Level 1 to Level 2	0		$ 0
Transfers of assets from Level 2 to Level 1	0		0
Transfers of liabilities from Level 1 to Level 2	0		0
Transfers of liabilities from Level 2 to Level 1	0		$ 0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets classified as Level 3	0	$ 0
Financial liabilities classified as Level 3	$ 0	$ 0

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Jun. 30, 2016USD ($)Securities	Dec. 31, 2015USD ($)Securities
Schedule of Available-for-sale Securities [Line Items]
Realized gains or losses on marketable securities	$ 0
Minimum period to liquidate	12 months	12 months
Debt securities in an unrealized loss position | Securities	13	74
Aggregate fair value of debt securities in an unrealized loss position	$ 20,300,000	$ 207,400,000
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Schedule of Available-for-sale Securities [Line Items]
Accumulated other comprehensive income (loss)	$ 0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period, non-current	2 years	2 years
Investment maturity period, current	1 year	1 year
Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period, non-current	1 year	1 year

Marketable Securities - Marketa

Marketable Securities - Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 503,811	$ 363,475
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	15,790	11,243
Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	169,179	292,900
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	93,278
Fair Value, Measurements, Recurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	277,950	304,461
Unrealized Gains	307	10
Unrealized Losses	(10)	(328)
Fair Value	278,247	304,143
Fair Value, Measurements, Recurring [Member] | Current: [Member] | Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,040	11,248
Unrealized Gains	2
Unrealized Losses		(5)
Fair Value	5,042	11,243
Fair Value, Measurements, Recurring [Member] | Current: [Member] | Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	158,571	234,130
Unrealized Gains	91	10
Unrealized Losses	(1)	(145)
Fair Value	158,661	233,995
Fair Value, Measurements, Recurring [Member] | Current: [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67,586
Unrealized Gains	38
Unrealized Losses	(6)
Fair Value	67,618
Fair Value, Measurements, Recurring [Member] | Non-Current: [Member] | Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,720
Unrealized Gains	31
Unrealized Losses	(3)
Fair Value	10,748
Fair Value, Measurements, Recurring [Member] | Non-Current: [Member] | Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,511	59,083
Unrealized Gains	7
Unrealized Losses		(178)
Fair Value	10,518	$ 58,905
Fair Value, Measurements, Recurring [Member] | Non-Current: [Member] | Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,522
Unrealized Gains	138
Fair Value	$ 25,660

Collaboration Agreements - Addi

Collaboration Agreements - Additional Information (Detail)	May 17, 2016USD ($)	Apr. 27, 2015USD ($)	Apr. 27, 2015USD ($)	Jul. 31, 2014USD ($)	Jun. 30, 2016USD ($)	May 31, 2015USD ($)	Apr. 27, 2015USD ($)	Jul. 31, 2014	Oct. 31, 2011	May 17, 2016USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)$ / shares	Apr. 27, 2015USD ($)	May 17, 2016USD ($)	Jun. 30, 2016USD ($)Program	Jun. 30, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue recognized												$ 7,000,000		$ 13,200,000				$ 13,300,000	$ 47,400,000
Amended collaboration expiration date																					2016-04
Term of the initial discovery period before amendment to extend																					5 years
Term of extended period after amendment of the initial discovery period																					6 years
Payment made in pursuant to the amendment																					$ 20,000,000
Recognized revenue to extension			$ 700,000
Increase in revenue from related party												6,978,000		13,219,000				38,259,000	47,421,000
Reduction in research and development expenditure												(5,900,000)		$ (4,500,000)				(14,700,000)	$ (8,900,000)
Collaboration receivable					$ 7,900,000							7,900,000						7,900,000		$ 8,200,000
2010 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement amended date								2014-07	2011-10
Milestone or royalty payments received																		0
Collaboration revenue recognized							$ 300,000									$ 400,000
Increase in revenue from related party															$ 5,100,000
Reduction in research and development expenditure							(300,000)								(3,800,000)	(900,000)
Reduction in net loss															$ 8,900,000
Decrease in net loss per share | $ / shares															$ (0.24)
AG-881 Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Initial payment received						$ 10,000,000												10,000,000
Revenue recognition, selling price					0													$ 48,700,000
Collaboration revenue recognized					17,000					$ 32,000	$ 22,000						$ 89,000
Additional reimbursable development expenses																	4,400,000
AG-881 Agreements [Member] | Split License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price		$ 33,200,000
Collaboration revenue recognized										500,000	8,800,000						1,400,000
AG-881 Agreements [Member] | Participation Service [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price	$ 1,500,000	800,000
AG-881 Agreements [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price	$ 207,000,000	30,500,000
Collaboration revenue recognized					2,700,000					1,000,000	1,400,000						4,600,000
2016 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research agreement commence date																		May 17, 2016
July 2014 - April 2015 [Member] | Split License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price				$ 21,200,000
Collaboration revenue recognized							100,000									15,800,000
July 2014 - April 2015 [Member] | Participation Service [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price				200,000
Collaboration revenue recognized							100,000									100,000
July 2014 - April 2015 [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price				13,600,000
Collaboration revenue recognized							1,000,000									5,000,000
AG-120 Agreements [Member ]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional reimbursable development expenses										1,100,000
Celgene Collaboration Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reduction in research and development expenditure					(400,000)					(400,000)							(900,000)
Phase 1b Frontline Combination Trial [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue recognized										500,000							1,200,000
Reduction in research and development expenditure										(200,000)							(300,000)
Ag 221 Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received													$ 25,000,000					$ 0		$ 0
Phase 1 [Member] | July 2014 - April 2015 [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price				$ 50,800,000
Collaboration revenue recognized							400,000									14,700,000
Other Than 65/35 Program [Member] | Co-Development and Co-Commercialization Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Profit or loss share percentage	50.00%
Other Than 65/35 Program [Member] | Co-Development and Co-Commercialization Agreements [Member] | Clinical Development Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	$ 20,000,000
Prior to July 2014 Amendment [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of years company expected to fulfill its performance obligations																		6 years
Four Separate Ongoing Development Services Determined as Primary Obligor of Development Activities [Member] | AG-881 Agreements [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price		12,700,000
Collaboration revenue recognized										600,000	600,000						1,700,000
Four Separate Ongoing Development Services Not Determined As Primary Obligor Of Development Activities [Member] | AG-881 Agreements [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price		97,300,000
Reduction in research and development expenditure										(2,600,000)	$ (3,400,000)						(7,500,000)
Three Separate Ongoing Development Services Determined As Primary Obligor Of Development Activities [Member] | AG-881 Agreements [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price	67,800,000
Collaboration revenue recognized					1,700,000
Three Separate Ongoing Development Services Not Determined As Primary Obligor Of Development Activities [Member] | AG-881 Agreements [Member] | In Process Research and Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition, selling price	22,400,000
Reduction in research and development expenditure					(1,300,000)
Celgene and Celgene RIVOT Ltd. [Member] | 2016 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Initial payment received	200,000,000
Initial research agreement period																		4 years
Research agreement expire period																		May 17, 2020
Term of research extended																		2 years
Number of research programs | Program																		3
Upfront payment agreement extension fee receivable	40,000,000
Designation fee receivable	8,000,000
Option exercise fee receivable	30,000,000									30,000,000							30,000,000
Additional option exercise fee for further development	10,000,000
Celgene and Celgene RIVOT Ltd. [Member] | Co-Development and Co-Commercialization Agreements [Member] | Clinical Development Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	25,000,000
Celgene and Celgene RIVOT Ltd. [Member] | Co Commercial Agreement [Member] | Clinical Development Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	$ 25,000,000
Celgene and Celgene RIVOT Ltd. [Member] | 65/35 Program [Member] | Co-Development and Co-Commercialization Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Profit or loss share percentage	65.00%
Maximum [Member] | 2010 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receipts of potential milestone payments					120,000,000							120,000,000						$ 120,000,000
Milestone payment upon achievement of a specified clinical development milestone event					25,000,000							25,000,000						25,000,000
Milestone payments upon achievement of specified regulatory milestone events					70,000,000							70,000,000						70,000,000
Milestone payment upon achievement of a specified commercial milestone event					$ 25,000,000							$ 25,000,000						$ 25,000,000
Maximum [Member] | AG-881 Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receipts of potential milestone payments		70,000,000	70,000,000				70,000,000									70,000,000
Milestone payments upon achievement of specified regulatory milestone events		55,000,000	55,000,000				55,000,000									55,000,000
Milestone payment for filing of first NDA		$ 15,000,000	$ 15,000,000				$ 15,000,000									$ 15,000,000
Maximum [Member] | Co-Development and Co-Commercialization Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	$ 169,000,000
Maximum [Member] | Other Than 65/35 Program [Member] | Co-Development and Co-Commercialization Agreements [Member] | Regulatory Milestone Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	149,000,000
Maximum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | Co-Development and Co-Commercialization Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	209,000,000
Maximum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | Co-Development and Co-Commercialization Agreements [Member] | Regulatory Milestone Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	184,000,000
Maximum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | Co Commercial Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	386,000,000
Maximum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | Co Commercial Agreement [Member] | Regulatory Milestone Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	236,000,000
Maximum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | Co Commercial Agreement [Member] | Commercial Milestone Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone or royalty payments received	125,000,000
Minimum [Member] | Celgene and Celgene RIVOT Ltd. [Member] | 2016 Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Minimum option exercise fee receivable for continuation program	$ 35,000,000									$ 35,000,000							$ 35,000,000

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued compensation	$ 6,352	$ 7,005
Accrued contracted research and development costs	6,214	7,449
Accrued professional fees	1,641	228
Accrued other	207	1,314
Total	$ 14,414	$ 15,996

Share-Based Payments - Addition

Share-Based Payments - Additional Information (Detail) - USD ($)	Jan. 01, 2016	Jan. 01, 2015	Feb. 29, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation expense				$ 10,996,000		$ 8,177,000	$ 20,103,000	$ 13,237,000
Stock options granted							1,155,940
Performance-Based Stock Option Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation expense				0			$ 0
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option				$ 2,600,000			$ 2,600,000
Weighted-average period to recognize compensation expense							1 year 6 months
Fair value granted amount				0	58,800	15,000	58,800	15,000
Stock Based compensation expense				$ 500,000		$ 200,000	$ 900,000	$ 300,000
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				6,546,275			6,546,275
Shares available for future issuance				981,516			981,516
2013 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance	1,507,860	1,484,020
Weighted-average grant date fair value of options				$ 31.89		$ 64.19	$ 27.17	$ 67.57
Intrinsic value of options exercised				$ 5,300,000		$ 11,300,000	$ 15,300,000	$ 29,400,000
Unrecognized compensation expense related to stock option				95,400,000			$ 95,400,000
Weighted-average period to recognize compensation expense							2 years 8 months 12 days
2013 Stock Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock							2,000,000
Common stock outstanding							4.00%
2013 Stock Incentive Plan [Member] | Performance-Based Stock Option Grants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to stock option				$ 8,200,000			$ 8,200,000
Stock Based compensation expense						0.1		$ 0.3
Stock options granted				0				0
2013 Stock Incentive Plan [Member] | Performance-Based Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Based compensation expense							$ 0
Stock options granted			15,000					0	100,270
2013 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance				297,795			297,795
Stock Based compensation expense				$ 200,000		100,000	$ 300,000	$ 200,000
Common stock, shares issued				$ 0		$ 0	$ 12,327	$ 10,664
Purchase price discount rate stock option							85.00%
Opportunity to purchase of common stock							327,272

Share-Based Payments - Summary

Share-Based Payments - Summary of Company's Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Stock Options, Outstanding, Beginning balance | shares	4,618,697
Number of Stock Options, Granted | shares	1,155,940
Number of Stock Options, Exercised | shares	(313,183)
Number of Stock Options, Forfeited/expired | shares	(78,265)
Number of Stock Options, Outstanding, Ending balance | shares	5,383,189	4,618,697
Number of Stock Options, Exercisable | shares	2,452,292
Number of Stock Options, Vested and expected to vest | shares	5,037,783
Weighted-Average Exercise Price, Outstanding, Beginning balance | $ / shares	$ 44.45
Weighted-Average Exercise Price, Granted | $ / shares	42.61
Weighted-Average Exercise Price, Exercised | $ / shares	6.36
Weighted-Average Exercise Price, Forfeited/expired | $ / shares	73.33
Weighted-Average Exercise Price, Outstanding, Ending balance | $ / shares	45.85	$ 44.45
Weighted-Average Exercise Price, Exercisable | $ / shares	30.04
Weighted-Average Exercise Price, Vested and expected to vest | $ / shares	$ 46.38
Weighted-Average Remaining Contractual Term (in years), Outstanding	7 years 7 months 17 days	7 years 5 months 27 days
Weighted-Average Remaining Contractual Term (in years), Exercisable	6 years 3 months 4 days
Weighted-Average Remaining Contractual Term (in years), Vested and expected to vest	7 years 7 months 6 days
Aggregate Intrinsic Value, Outstanding | $	$ 73,370	$ 153,573
Aggregate Intrinsic Value, Exercisable | $	58,983
Aggregate Intrinsic Value, Vested and expected to vest | $	$ 67,811

Share-Based Payments - Summar32

Share-Based Payments - Summary of Unvested RSUs Activity (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares	3 Months Ended			6 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares beginning of period		15,000		15,000
Granted	0	58,800	15,000	58,800	15,000
Vested				(7,500)
Unvested shares end of period	66,300			66,300
Weighted-average grant date fair value, Unvested shares beginning of period		$ 122.22		$ 122.22
Weighted-average grant date fair value, Granted				39.76
Weighted-average grant date fair value, Vested				122.22
Weighted-average grant date fair value, Unvested shares end of period	$ 49.09			$ 49.09

Share-Based Payments - Stock-Ba

Share-Based Payments - Stock-Based Compensation Expense for Employee and Non-Employee Stock Options, Restricted Stock Units, Restricted Stock, Performance-Based Stock Options, Performance-Based Stock Units and the Employee Stock Purchase Plan Shares (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	$ 10,996	$ 8,177	$ 20,103	$ 13,237
Research and development expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	6,561	4,569	12,089	7,180
General and administrative expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation expense	$ 4,435	$ 3,608	$ 8,014	$ 6,057

Share-Based Payments - Schedule

Share-Based Payments - Schedule of Grant Date Fair Value Option Award Weighted Average Assumptions Used (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.38%	1.71%	1.41%	1.71%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	5 years 10 months 21 days	5 years 10 months 17 days	6 years 15 days	6 years 11 days
Expected volatility	72.53%	68.93%	71.72%	70.02%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	6 Months Ended
	Jan. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax liability paid	$ 6,000,000
Interest and penalties paid	$ 1,500,000
(Benefit) provision for income taxes		$ 0	$ 0
Unrecognized tax benefits		$ 0		$ 0

Loss per Share - Common Stock E

Loss per Share - Common Stock Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5,465,406	4,719,587	5,465,406	4,719,587
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5,383,189	4,687,805	5,383,189	4,687,805
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	66,300	25,000	66,300	25,000
Unvested Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		2,841		2,841
Employee Stock Purchase Plan Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	15,917	3,941	15,917	3,941