As Of	Filer	Filing¹	For·On·As	Docs:Size	Issuer		Filing Agent

 2/10/16  bng0, LLC                         4          10% Owner²  1:6K   Editas Medicine, Inc.             Section16 Direct/FA      
  2/9/16  Afeyan Noubar                     4          10% Owner²  1:24K  Editas Medicine, Inc.             Section16 Direct/FA      
          Flagship Ventures Fund IV General Partner LLC
          Flagship Ventures Fund IV, L.P.
          Flagship Ventures Fund IV-Rx, L.P.
          Kania Edwin M Jr.
  2/9/16  Bitterman Kevin                   4          Dir.,%Own.² 1:11K  Editas Medicine, Inc.             Section16 Direct/FA      
  2/9/16  Ott David C.                      4/A        Other²      1:29K  Editas Medicine, Inc.             Cleary Gottlieb Ste… LLP 
          Halvorsen Ole Andreas
          Sundheim Daniel S.
          Viking Global Investors LP
          Viking Global Opportunities GP LLC
          Viking Global Opportunities Illiquid Investments Sub-Master LP
          Viking Global Opportunities Portfolio GP LLC
  2/9/16  Viking Long Fund Master Ltd.      4/A        Other²      1:28K  Editas Medicine, Inc.             Cleary Gottlieb Ste… LLP 
          VGE III Portfolio Ltd.
          Viking Global Equities II LP
          Viking Global Equities LP
          Viking Global Performance LLC
          Viking Long Fund GP LLC
  2/9/16  Borisy Alexis                     4          Director²   1:10K  Editas Medicine, Inc.             Section16 Direct/FA      
  2/9/16  Nikolic Boris                     4          Director²   1:6K   Editas Medicine, Inc.             Section16 Direct/FA      
  2/9/16  Bosley Katrine                    4          Dir.,Off.²  1:8K   Editas Medicine, Inc.             Section16 Direct/FA      
  2/9/16  Polaris Venture Partners F… VI LP 4          10% Owner²  1:15K  Editas Medicine, Inc.             Donnelley Fin’l S… 06/FA 
          Polaris Venture Management Co. VI, L.L.C.
          Polaris Venture Partners VI, L.P.
  2/8/16  Ott David C.                      4          10% Owner²  1:29K  Editas Medicine, Inc.             Cleary Gottlieb Ste… LLP 
          Halvorsen Ole Andreas
          Sundheim Daniel S.
          Viking Global Investors LP
          Viking Global Opportunities GP LLC
          Viking Global Opportunities Illiquid Investments Sub-Master LP
          Viking Global Opportunities Portfolio GP LLC
  2/8/16  Viking Long Fund Master Ltd.      4          10% Owner²  1:28K  Editas Medicine, Inc.             Cleary Gottlieb Ste… LLP 
          VGE III Portfolio Ltd.
          Viking Global Equities II LP
          Viking Global Equities LP
          Viking Global Performance LLC
          Viking Long Fund GP LLC
  2/8/16  Viking Long Fund GP LLC           3          10% Owner²  1:16K  Editas Medicine, Inc.             Cleary Gottlieb Ste… LLP 
          VGE III Portfolio Ltd.
          Viking Global Equities II LP
          Viking Global Equities LP
          Viking Global Performance LLC
          Viking Long Fund Master Ltd.
  2/8/16  Tepper Robert I                   4          10% Owner²  1:16K  Editas Medicine, Inc.             Donnelley Fin’l S… 06/FA 
          Levin Mark J
          Starr Kevin P
          Third Rock Ventures GP III, L.P.
          Third Rock Ventures III, L.P.
          TRV GP III, LLC
  2/8/16  Editas Medicine, Inc.             8-K:5,9      2/8/16    3:301K                                   Toppan Merrill-FA        
  2/8/16  Deerfield Mgmt HIF, L.P.          4          %Own.,Oth.² 2:45K  Editas Medicine, Inc.             E-Data Systems, Inc./FA  
          Deerfield Healthcare Innovations Fund, L.P.
          Deerfield Management Co.
          Deerfield Mgmt III, L.P.
          Deerfield Private Design Fund III, L.P.
          Flynn James E
  2/8/16  Flynn James E                     SC 13G                 1:325K Editas Medicine, Inc.             E-Data Systems, Inc./FA  
          Deerfield Healthcare Innovations Fund, L.P.³
          Deerfield Management Company, L.P.³
          Deerfield Mgmt Hif, L.P.³
          Deerfield Mgmt III, L.P.³
          Deerfield Private Design Fund III, L.P.³

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¹	Filing/Form Types:  /A
	3	Initial Statement of Beneficial Ownership of Securities by an Insider — Form 3 { The Filer is an Insider² of the Issuer }.
	4	Statement of Changes in Beneficial Ownership of Securities by an Insider — Form 4 { The Filer is an Insider² of the Issuer }.
	8-K	Current Report — Form 8-K { Item 1: Business & Operations;  2: Financial Info;  3: Securities & Trading;  4: Accountants & Accounting;  5: Governance & Management;  6: Asset-Backed Securities;  7: Disclosures;  8: Events;  9: Financials }.
	SC 13G	Statement of Acquisition of Beneficial Ownership by a “Passive” Investor — Schedule 13G.
	/A	Amendment to, or Amended version of, a previous Filing of this Type.
²	Insider:  The Filer is a Director, Officer, 10% Owner and/or Other “insider” of the Issuer.
³	Group Member:  A Registrant or non-Registrant party to this Filing made by a Group.