Editas Medicine Announces Second Quarter 2016 Results and Update Exclusive license to high-fidelity Cas9 and Cas9 PAM variants from Massachusetts General Hospital further advances leading genome editing platform Strategi

Editas Medicine Announces Second Quarter 2016 Results and Update

Exclusive license to high-fidelity Cas9 and Cas9 PAM variants from Massachusetts General Hospital further advances leading genome editing platform

Strategic partnership with Adverum to explore delivery of genomic medicines

to treat range of genetic eye diseases

CAMBRIDGE, Mass., August 9, 2016 Editas Medicine, Inc. (NASDAQ: EDIT), a leading genome editing company, today reported financial results for the second quarter ended June 30, 2016, and provided an update on recent accomplishments and upcoming events.

We continue to make strong progress advancing our leadership position in genome editing and developing important new medicines for patients with a wide range of genetically-defined diseases, said Katrine Bosley, President and Chief Executive Officer of Editas Medicine. With our recent strategic agreements with Massachusetts General Hospital, Adverum, and San Raffaele Telethon Institute for Gene Therapy, we have significantly expanded our platform capabilities while continuing to enhance and expand our product pipeline.

Second Quarter 2016 Financial Results

Cash and cash equivalents at June 30, 2016 were $217.7 million, compared to $143.2

million at December 31, 2015.

For the three months ended June 30, 2016, net loss attributable to common stockholders was $19.0 million, or $0.54 per share, compared to $47.7 million, or $21.45 per share, for the same period in 2015.

The Editas management team will host a conference call and webcast today at 5:00 p.m. ET to provide and discuss a corporate update and second quarter 2016 financial results. To access the call, please dial 877-809-6321 (domestic) or 615-247-0223 (international) and provide the passcode 56269948. A live webcast of the call will be available on the Investors & Media section of the Editas website at www.editasmedicine.com and a replay will be available approximately two hours after its completion.

About Editas Medicine

Editas Medicine is a leading genome editing company dedicated to treating patients with genetically-defined diseases by correcting their disease-causing genes. The Company was founded by world leaders in genome editing, and its mission is to translate the promise of genome editing science into a broad class of transformative genomic medicines to benefit the greatest number of patients.

Forward-Looking Statements

This press release contains forward-looking statements and information within the meaning of The Private Securities Litigation Reform Act of 1995. The words anticipate,'' believe,'' continue,'' could,'' estimate,'' expect,'' intend,'' may,'' plan,'' potential,'' predict,'' project,'' target,'' should,'' would,'' and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. The Company may not actually achieve the plans, intentions, or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various factors, including: uncertainties inherent in the initiation and completion of preclinical studies and clinical trials and clinical development of the Company's product candidates; availability and timing of results from preclinical studies and clinical trials; whether interim results from a clinical trial will be predictive of the final results of the trial or the results of future trials; expectations for regulatory approvals to conduct trials or to market products and availability of funding sufficient for the Company's foreseeable and unforeseeable operating expenses and capital expenditure requirements. These and other risks are described in greater detail under the caption Risk Factors included in the Company's most recent Quarterly Report on Form 10-Q, which is on file with the Securities and Exchange Commission, and in other filings that the Company 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 the Company expressly disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

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