Agios Reports Third Quarter 2015 Financial Results New AG-221 and AG-120 Data in Solid Tumors and Hematologic Malignancies to be Presented at AACR-NCI-EORTC and ASH Annual Meeting R&D Day Highlights Included Initiation o

Agios Reports Third Quarter 2015 Financial Results

New AG-221 and AG-120 Data in Solid Tumors and Hematologic Malignancies to be Presented at AACR-NCI-EORTC and ASH Annual Meeting

R&D Day Highlights Included Initiation of AG-221 Phase 3 IDHENTIFY Study, Design of AG-221 and AG-120

Frontline Combination Studies, and Selection of Second PKR Activator, AG-519, for Clinical Development

CAMBRIDGE, Mass., November 5,

2015 Agios Pharmaceuticals, Inc. (NASDAQ: AGIO), a leader in the fields of cancer metabolism and rare genetic metabolic disorders, today reported business highlights and financial results for the third quarter ended September 30,

We have made significant progress this year toward realizing our goal of what s possible for patients with our IDH inhibitors by

deploying a comprehensive development strategy of speed and breadth with AG-221 and AG-120 in AML and other cancers, said David Schenkein, M.D., chief executive officer at Agios. In addition, we are pleased to have selected our fifth

molecule, AG-519, for clinical development in PK deficiency. This coupled with DRIVE PK, our ongoing Phase 2 study of AG-348, may optimize our potential to help people with this rare genetic disorder.

KEY UPCOMING MILESTONES IN CANCER METABOLISM

anticipates the following milestones from its IDH clinical development programs in collaboration with Celgene:

AG-221: a first-in-class, oral,

selective, potent inhibitor of the mutated IDH2 protein

AG-120: a first-in-class, oral, selective, potent inhibitor of the mutated IDH1 protein

AG-221 and AG-120 front-line AML combination trials

KEY UPCOMING MILESTONES IN RARE GENETIC METABOLIC DISORDERS

AG-348: a novel, first-in-class, oral activator of pyruvate kinase-R (PKR) for the treatment of pyruvate kinase (PK) deficiency

AG-519: a novel, oral activator of PKR for the treatment of PK deficiency

RECENT DEVELOPMENT UPDATES IN CANCER METABOLISM

has provided the following updates on its clinical development programs in collaboration with Celgene:

AG-881: a brain-penetrant, first-in-class, oral, potent pan-inhibitor of the mutated IDH1 and IDH2

RECENT DEVELOPMENT UPDATES IN

RARE GENETIC DISORDERS OF METABOLISM

THIRD QUARTER 2015 FINANCIAL RESULTS

equivalents and marketable securities as of September 30, 2015 were $408.0 million, compared to $467.4 million as of December 31, 2014. The decrease was driven by cash used to fund operating activities of approximately $101.2 million,

which was offset by funding of approximately $54.8 million made by Celgene during the nine months ended September 30, 2015 related to our collaboration agreements.

Collaboration revenue was $5.5 million for the third quarter of 2015, compared to $33.9 million for the comparable period in 2014. In July 2014, the company

amended its collaboration agreement with Celgene. As a result, for the third quarter of 2014 the company recognized a total of $25.9 million under the previous accounting guidance and upon the modification in addition to $8.0 million in revenue

subsequent to the modification through September 30, 2014.

Research and development (R&D) expense was $36.0 million, including $4.9 million of

stock-based compensation expense in the third quarter of 2015, compared to $25.5 million, including $1.4 million in stock-based compensation expense for the comparable period in 2014. The increase in R&D expense was primarily due to increased

costs to support advancement of the company s lead investigational medicines toward later-stage development.

General and administrative (G&A) expense was $9.9 million, including $4.5 million of stock-based

compensation expense, in the third quarter of 2015, compared to $5.2 million, including $1.4 million of stock-based compensation expense, for the comparable period in 2014. The increase in G&A expense was largely due to increased headcount and

other professional expenses to support growing operations.

Net loss for the third quarter of 2015 was $40.3 million, compared to net income of $3.7

million for the comparable period in 2014. The third quarter of 2014 includes additional revenue recognition related to the amendment of the company s collaboration agreement with Celgene.

FINANCIAL GUIDANCE FOR THE FULL YEAR 2015

reiterating that it expects to end 2015 with more than $350.0 million of cash, cash equivalents and marketable securities. The anticipated year end 2015 cash position does not include any additional program-specific milestone payments. Agios expects

that its cash, cash equivalents and marketable securities would be sufficient to fund its operating expenses and capital expenditure requirements until late 2017.

CONFERENCE CALL INFORMATION

Agios will host a conference

call and live webcast with slides today at 8:00 a.m. ET to discuss the third quarter 2015 financial results and recent business activities. To participate in the conference call, please dial (877) 377-7098 (domestic) or (631) 291-4547

(international) and refer to conference ID 66586914. The live webcast can be accessed under Events & Presentations in the Investors & Media section of the company s website at www.agios.com. The archived webcast

will be available on the company s website beginning approximately two hours after the event.

Agios is focused on discovering and developing novel investigational medicines to treat cancer and rare genetic metabolic disorders through scientific

leadership in the field of cellular metabolism. In addition to an active research and discovery pipeline across both therapeutic areas, Agios has multiple first-in-class investigational medicines in clinical and/or preclinical development. All Agios

programs focus on genetically identified patient populations, leveraging our knowledge of metabolism, biology and genomics. For more information, please visit the company s website at agios.com.

About Agios/Celgene Collaboration

AG-881 are part of Agios global strategic collaboration with Celgene Corporation. Under the terms of the collaboration, Celgene has worldwide development and commercialization rights for AG-221. Agios continues to conduct clinical development

activities within the AG-221 development program and is eligible to receive up to $120 million in payments on achievement of certain milestones and royalties on net sales. For AG-120, Agios retains U.S. development and commercialization rights.

Celgene has an exclusive license outside

the United States. Celgene is eligible to receive royalties on net sales in the U.S. Agios is eligible to receive royalties on net sales outside the U.S. and up to $120 million in payments on

achievement of certain milestones. For AG-881, the companies have a joint worldwide development and 50/50 profit share collaboration, and Agios is eligible to receive regulatory milestone payments of up to $70 million.

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking

statements include those regarding the potential benefits of Agios product candidates targeting IDH1/IDH2 or pyruvate kinase-R mutations, including AG-221, AG-120, AG-881, AG-348 and AG-519; its plans and timelines for the clinical development

of AG-221, AG-120, AG-881, AG-348 and AG-519; its plans regarding future data presentations; its financial guidance regarding the amount of cash, cash equivalents and marketable securities that the company will have as of December 31, 2015; and

the benefit of its strategic plans and focus. The words anticipate, believe, estimate, expect, intend, may, plan, predict, project,

potential, hope, could, would and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Such statements

are subject to numerous important factors, risks and uncertainties that may cause actual events or results to differ materially from Agios current expectations and beliefs. For example, there can be no guarantee that any product candidate

Agios is developing will successfully commence or complete necessary preclinical and clinical development phases, or that development of any of Agios product candidates will successfully continue. There can be no guarantee that any positive

developments in Agios business will result in stock price appreciation. Management s expectations and, therefore, any forward-looking statements in this press release could also be affected by risks and uncertainties relating to a number

of other important factors, including: Agios results of clinical trials and preclinical studies, including subsequent analysis of existing data and new data received from ongoing and future studies; the content and timing of decisions made by

the U.S. FDA and other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies; Agios ability to obtain and maintain requisite regulatory approvals and to enroll patients in its planned

clinical trials; unplanned cash requirements and expenditures; competitive factors; Agios ability to obtain, maintain and enforce patent and other intellectual property protection for any product candidates it is developing; Agios

ability to maintain key collaborations, such as its agreement with Celgene; and general economic and market conditions. These and other risks are described in greater detail under the caption Risk Factors included in Agios

Quarterly Report on Form 10-Q for the quarter ended June 30, 2015, and other filings that Agios may make with the Securities and Exchange Commission in the future. Any forward-looking statements contained in this press release speak only as of

the date hereof, and Agios expressly disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

Consolidated Balance Sheet Data

Consolidated Statements of Operations Data

(in thousands, except share and per share data)

Note 1 (Collaboration revenue): The collaboration revenue decrease for the three months ended

September 30, 2015 was primarily due to the application of new accounting guidance to the Company s collaboration arrangements with Celgene, which include the July 2014 amendment of the 2010 agreement and the April 2015 execution of the

AG-881 agreements. Previously, all arrangement consideration was recognized ratably over the estimated period of performance. Under the new accounting guidance, revenue is recognized as services or goods are delivered. The three months ended

September 30, 2014 included recognized revenue at the July 2014 amendment date related to the excess of total consideration over the best estimate of selling price of undelivered elements, which fundamentally related to previously delivered

elements under the agreement and includes the exclusive global license for development and commercialization of AG-221.

Note 2 (R&D expense): During

the first quarter of 2015, the Company began offsetting R&D expense for amounts received from Celgene for reimbursement of costs incurred on Celgene s behalf. The R&D expense reported for the three and nine months ended

September 30, 2015 is presented net of $7.8 million and $16.7 million, respectively, of reimbursement compared to no offset for cost reimbursement for the comparable periods in 2014.

Agios Pharmaceuticals:

Renee Leck, 617-649-8299

Senior Manager, Investor and Public