Editas Medicine Inc

Director and Officer Trading Arrangements

A portion of the compensation of our directors and officers (as defined in Rule 16a-1(f) under the Securities Exchange Act of 1934 (the “Exchange Act”)) is in the form of equity awards and, from time to time, directors and officers may engage in open-market transactions with respect to the securities acquired pursuant to such equity awards or other of our securities, including to satisfy tax withholding obligations when equity awards vest or are exercised, and for diversification or other personal reasons.

Transactions in our securities by directors and officers are required to be made in accordance with our insider trading policy, which requires that the transactions be in accordance with applicable U.S. federal securities laws that prohibit trading while in possession of material nonpublic information. Rule 10b5-1 under the Exchange Act provides an affirmative defense that enables directors and officers to prearrange transactions in our securities in a manner that avoids concerns about initiating transactions while in possession of material nonpublic information.

None of our directors or officers adopted orterminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement (as defined in Item 408(c) of Regulation S-K) during the fourth quarter of 2024.

Common Stock Sales Agreement Amendment

On March 5, 2025, we entered in a second amendment to the Common Stock Sales Agreement with TD Cowen, pursuant to which we may offer and sell from time to time shares of our common stock through or to TD Cowen as our sales agent or principal, in order to reduce the aggregate offering amount of shares that may be sold thereunder from $300.0 million to $150.0 million. The foregoing description of the amendment is qualified in its entirety by reference to the full text of the amendment, a copy of which is included as Exhibit 10.38 to this Annual Report on Form 10-K.