Editas Medicine Inc

Our Nominating and Corporate Governance Committee reviews each director’s external time commitments not less than quarterly and, as required by our corporate governance guidelines, takes into account the nature of, including any public company board leadership positions, and time involved in a director’s service on other boards in evaluating the suitability of individual directors and making recommendations to the Board. In addition, our corporate governance guidelines provide that existing directors should advise the Board chair and the chair of the Nominating and Corporate Governance Committee in advance of accepting an invitation to serve on another public company board. The Nominating and Corporate Governance Committee reviews such requests and has the discretion as to whether to approve or disapprove such directorship.

Our corporate governance guidelines include a formal policy limiting the number of director external commitments, requiring that:

•no director who serves as an executive officer of any public company (including Editas) should serve on the boards of more than two public companies (including Editas);

•no non-employee director should serve on the boards of more than four public companies (including Editas); and

•no director who serves as non-executive Chair of the Board or as lead independent director should serve on the boards of more than four public companies (including Editas),

in each case unless the Nominating and Corporate Governance Committee determines that such service would not impair the ability of such director to effectively serve on the Board. As of the date of this Proxy Statement, all directors are in compliance with this policy.