• Other Ocular Programs
  Preclinical data for USH2A and RP4 presented at ARVO
  Editas Medicine presented preclinical data at the Association for Research in Vision and Ophthalmology (ARVO) 2021 Annual Meeting for Usher Syndrome 2A (USH2A) and retinitis pigmentosa 4 (RP4). For USH2A, the Company demonstrated that gene editing restored protein expression and rescued deficits in photoreceptor morphology in human retinal organoids. For RP4, the Company demonstrated that a dual adeno-associated virus editing system, which simultaneously knocks out and replaces the rhodopsin mutation of RP4, produced clinically relevant editing levels with no off-target editing. The Company expects to declare a development candidate for its RP4 program by the end of 2021.
  

• EDIT-301 for Sickle Cell Disease
  On track to dose first patient in RUBY trial by year-end
  Editas Medicine is developing EDIT-301 using Cas12a (Cpf1), a proprietary enzyme, as a potentially best-in-class medicine to treat sickle cell disease. The Phase 1/2 RUBY trial for the treatment of sickle cell disease is active and recruitment of patients has started. The Company remains on track to begin patient dosing in the RUBY trial by the end of 2021.

• Edited iPSC NK (iNK) Cell Medicines to Treat Solid Tumors
  Preclinical data presented at AACR
  Editas Medicine presented preclinical data at the American Association for Cancer Research (AACR) 2021 Annual Meeting for its iNK program to treat solid tumors. The data showed that iPSC-derived natural killer (NK) cells, edited with CRISPR/Cas12a to knockout CISH and TGFβR2, demonstrated superior cytotoxicity and enhanced metabolic function in a tumor microenvironment, as well as improved serial killing capacity of certain tumors. These data confirm the expectation of the CISH and TGFβR2 double knockout as a potential superior treatment for solid tumors.

• Leadership
  Today, the Company announced Mark S. Shearman, Ph.D., will be joining Editas as Chief Scientific Officer, in June 2021. Dr. Shearman has more than 30 years of experience in drug discovery and development across multiple therapeutic modalities, and his expertise in neurology, ophthalmology, and immunology will strengthen the Company's existing pipeline. Dr. Shearman will join Editas Medicine from Applied Genetic Technologies Corporation (AGTC), where he is currently serving as Chief Scientific Officer and is responsible for leading the company's product candidate selection process, pre-clinical and translational research, and long-term research and development planning. Prior to AGTC, Dr. Shearman served as Senior Vice President of Research & Early Development at EMD Serono, Inc., the U.S. and Canadian subsidiary of Merck KGaA. Previously, Dr. Shearman was Executive Director of Merck & Co. Research Laboratories in Boston, and Senior Director at the Merck Sharp & Dohme Research Laboratories Neuroscience Research Centre in the United Kingdom. Dr. Shearman earned a B.Sc. from the University of Bristol, U.K., and a Ph.D. from the University of Nottingham, U.K. He also conducted academic research at institutes in Japan and Germany.
  

• Manufacturing
  Editas Medicine continues to advance internal and external manufacturing capabilities for the Company's portfolio of in vivo gene edited medicines, ex vivo gene edited cell medicines, and cell therapy medicines. The Company is finalizing the preparation of internal manufacturing capabilities for EDIT-301. This capability will provide early phase product for the RUBY trial. Concurrently, the Company has initiated the technology transfer process of EDIT-301 to its strategic CDMO partner Catalent for the later stages of the RUBY trial.
  

• Offering of Common Stock
  Strengthened balance sheet with net proceeds of approximately $250 million
  Editas Medicine closed an underwritten offering of 4,025,000 shares of its common stock at a public offering price of $66.00 per share, before deducting underwriter discounts and commissions and estimated offering expenses. This included 525,000 shares issued upon exercise in full by the underwriters of their option to purchase additional shares. All shares in the offering were sold by Editas Medicine.

• Research and development expenses increased by $7.3 million, to $41.9 million for the three months ended March 31, 2021, from $34.6 million for the same period in 2020. The $7.3 million increase was primarily attributable to sublicense and license fees primarily related to success payments under certain of our license agreements, as well as increased manufacturing and clinical related costs, during the first quarter of 2021.
  
• General and administrative expenses increased by $3.6 million to $21.4 million for the three months ended March 31, 2021, from $17.8 million for the same period in 2020. The $3.6 million increase was primarily attributable to increased employee-related expenses.

Conference Call

The Editas Medicine management team will host a conference call and webcast today at 8:00 a.m. ET to provide and discuss a corporate update and financial results for the first quarter 2021. To access the call, please dial 844-348-3801 (domestic) or 213-358-0955 (international) and provide the passcode 7587147.  A live webcast of the call will be available on the Investors & Media section of the Editas Medicine website at www.editasmedicine.com and a replay will be available approximately two hours after its completion.

About Editas Medicine
As a leading genome editing company, Editas Medicine is focused on translating the power and potential of the CRISPR/Cas9 and CRISPR/Cas12a (also known as Cpf1) genome editing systems into a robust pipeline of treatments for people living with serious diseases around the world. Editas Medicine aims to discover, develop, manufacture, and commercialize transformative, durable, precision genomic medicines for a broad class of diseases. For the latest information and scientific presentations, please visit www.editasmedicine.com.

About BRILLIANCE
The BRILLIANCE Phase 1/2 clinical trial of EDIT-101 for the treatment of Leber congenital amaurosis 10 (LCA10) is designed to assess the safety, tolerability, and efficacy of EDIT-101 in up to 18 patients with this disorder. Clinical trial sites are enrolling up to five cohorts testing up to three dose levels in this open label, multi-center study. Both adult and pediatric patients (3 – 17 years old) with a range of baseline visual acuity assessments are eligible for enrollment. Patients receive a single administration of EDIT-101 via subretinal injection in one eye. Additional details are available on www.clinicaltrials.gov (NCT#03872479).

About EDIT-301
EDIT-301 is an experimental, autologous cell therapy medicine under investigation for the treatment of sickle cell disease. EDIT-301 is comprised of sickle patient CD34+ cells genetically modified using a highly specific and efficient CRISPR/Cas12a (also known as Cpf1) ribonucleoprotein (RNP) that targets the HBG1 and HBG2 promoters in the beta-globin locus where naturally occurring fetal hemoglobin (HbF) inducing mutations reside. Red blood cells derived from EDIT-301 CD34+ cells demonstrate a sustained increase in HbF production, which has the potential to provide a durable treatment benefit for people living with sickle cell disease.

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. Forward-looking statements in this press release include statements regarding the initiation, timing, progress and results of the Company's preclinical and clinical studies and its research and development programs, including beginning patient dosing in the RUBY trial by the end of 2021, the timing for the Company's receipt and presentation of data from its clinical trials and preclinical studies, including presenting data from the first two cohorts of the BRILLIANCE trial by the end of 2021, and the timing or likelihood of regulatory filings and approvals, including filing an IND for EDIT-301 for the treatment of beta-thalassemia by the end of 2021. 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 pre-clinical studies and clinical trials and clinical development of the Company's product candidates; availability and timing of results from pre-clinical 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 Annual Report on Form 10-K, 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 represent Company's views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, the Company explicitly disclaims any obligation to update any forward-looking statements.