February 11, 2016 Vic Myer, Chief Technology Officer

The Potential to Repair Any Broken Gene Confluence of human genetics, delivery technologies, and CRISPR genome editing Our mission is to translate the promise of genome editing into a broad class of transformative genomic medicines to benefit the greatest number of patients © 2016 Editas Medicine

Scalable Platform Targeting CRISPR Medicines Wide range of technologies underpinning translation of the technology Achieve Right Repair Specifically Edit Wide Range of Mutations  New Cas9 species and variants  Engineered Protein and gRNAs  Identification of Lead Molecules  Cut orientation  Donor template engineering  Exogenous repair factors Directed Editing Nuclease Engineering Control & Specificity Delivery Tightly Control Cutting Reach Site of Disease  Multiple orthogonal specificity  All-in-one AAVs  Electroporation of RNA/RNP  Lipid nanoparticles measurement technologies  Tissue selective promoters  Self-regulating systems © 2016 Editas Medicine

Biology, Clinical, Regulatory Multiple Potential Therapeutic Areas ~6,000 diseases caused by genetic mutations; ~95% have no approved therapy  Repair mechanism required for edi4ng  Presence of common muta4on or mul4ple muta4ons  Ability to iden4fy specific and efficacious leads  Needs not presently being adequately addressed by exis4ng therapeu4c modali4es  Ability to generate a differen4ated product Medical Need Priority Disease Indica0ons Biology, Clinical, Regulatory Technology  Number of cells and type of cells to target  Demonstrated methods for specific target cell and 4ssue type  Disease natural history and ability to affect disease with edi4ng  Sufficient clinical endpoints and access to pa4ents to carry out clinical trials Delivery © 2016 Editas Medicine

Diverse Pipeline Across Range of Diseases Targeting first product candidate in clinic in 2017 with additional programs to follow Target Editing Delivery Commercial IND Our Programs Gene Mechanism Mode Rights Discovery Enabling Phase I Eye Diseases NHEJ – Small Deletion Leber Congenital Amaurosis 10 CEP290 AAV in vivo 2016 2017 Genetic and Infectious Disease(s) of Eye Examples: Usher Syndrome 2a, HSV-1 Multiple NHEJ AAV in vivo Engineered T Cells Juno Gene Editing in T Cells to Treat Cancer Multiple NHEJ ex vivo Additional Research Programs Non-Malignant Hematologic Diseases Examples: Beta Thalassemia, Sickle Cell Multiple NHEJ & HDR ex vivo Genetic Disease(s) of Muscle Example: Duchenne Muscular Dystrophy NHEJ – Small & Large Del. Multiple Multiple Genetic Disease(s) of Lung Example: Cystic Fibrosis Multiple NHEJ & HDR Multiple Genetic and Infectious Disease(s) of Liver Example: Alpha-1 Antitrypsin Deficiency NHEJ: Non-homologous end joining Multiple NHEJ & HDR Multiple HDR: Homology directed repair © 2016 Editas Medicine

Potential Regulatory Framework for IND Filing Product candidates that create directed, durable changes to the somatic genome are in the clinic:  HIV and hemophilia (ZFN) and CLL and ALL (TALENS) The procedures and standards applied to gene therapy products and cell therapy products may be applied to any CRISPR/Cas9 product candidates  Within the FDA’s CBER, Office of Cellular, Tissue and Gene Therapies; Advisory Committee to advise CBER on its reviews  CBER works closely with the NIH and their Recombinant DNA Advisory Committee (RAC), which makes recommendations to the NIH on gene therapy issues Engages in a public discussion of scientific, safety, ethical, and societal issues related to proposed and ongoing gene therapy protocols. Close working partnership with global regulators is critical © 2016 Editas Medicine

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