Editas Medicine, Inc.

This summary highlights information related to topics discussed throughout this Proxy Statement. This summary does not contain all of the information that you should consider, and you should read the entire Proxy Statement carefully before voting.

Attend our 2026 Annual Meeting of Stockholders Via Live Webcast

Wednesday, June 17, 2026 at 8:30 a.m., Eastern Time Access to Live Webcast: www.virtualshareholdermeeting.com/EDIT2026

How to Vote Prior to the Annual Meeting

Please note that the Annual Meeting will be held virtually, via live webcast, rather than in-person. To attend the Annual Meeting, you will need the 16-digit control number located on your Notice, on your proxy card or on the instructions that accompanied your proxy materials.

If you attend the Annual Meeting, you may vote your shares electronically during the Annual Meeting even if you have previously returned your proxy card or completed your proxy by phone or on the Internet. Stockholders wishing to vote their shares electronically during the Annual Meeting should refer to the Notice for instructions regarding voting electronically during the Annual Meeting.

Cast Your Vote Right Away

Please cast your vote right away on all of the proposals listed below to ensure that your shares are represented.

Select Business Highlights

In January 2023, we announced our strategy to become a leader inin vivo gene editing, leveraging cutting edge gene editing technology to deliver transformative therapies that simplify the usability for patients, minimize the burdens to patients and healthcare systems, and are meaningfully differentiated from the current standards of care. Following scientific breakthroughs by our team, we accelerated this strategy in December 2024 by transitioning to a fullyin vivo focused preclinical company with the intent of achievingin vivo human proof-of-concept within approximately two years.

In 2025, we began to see the fruits of this decision, as indicated by the below highlights.

•Cardiovascular. In September 2025 we announced the nomination of our leadin vivo development candidate, EDIT-401, an experimental, potential best-in-class, one-time therapy designed to treat elevated levels of LDL-cholesterol (“LDL-C”), or hyperlipidemia, through upregulation of the LDL receptor. In preclinical studies in non-human primates, EDIT-401 has achieved LDL-C reductions exceeding 90%.

•Hemoglobinopathies. Leveraging our differentiated approach from our former reni-cel program, in January 2025, we announcedin vivo preclinical proof-of-concept data of editing hematopoietic stem cells (“HSC”) in non-human primates, a key step in developing anin vivo treatment for sickle cell disease and transfusion-dependent beta thalassemia, and continued to optimize candidates for our HSC program.

•Other cells and tissues. We advanced our “plug ‘n play” lipid nanoparticle (“LNP”) platform, which is designed to enable targeted delivery ofin vivo gene editing medicines to multiple cells and tissues. In the liver, using this LNP platform enables us to develop new therapies by only reprogramming guide RNAs for specific liver targets. For extrahepatic delivery, our LNP platform enables us to target multiple tissues through the substitution of different targeting ligands conjugated to the LNP.

In addition, through the use of our at-the-market offering facility and continued financial discipline, we extended our cash runway into the third quarter of 2027, placing us in a strong position to build on our achievements in 2025 and drive EDIT-401 toward upcoming milestones.

The following summarizes our current research programs and disease areas:

Governance Highlights

We are committed to strong corporate governance and the regular review of our corporate governance practices to continue building on our success and create long-term stockholder value. As part of our regular governance practice review, we conduct a robust stockholder outreach program to solicit and understand our stockholders’ perspectives on our practices and to better understand the reasons for their votes. We also engage with certain proxy advisory firms to understand their governance policies and related vote recommendations. Our Board and the Nominating and Corporate Governance Committee of our Board consider feedback received from this effort and other input from our stockholders and other stakeholders in determining what further governance actions, if any, are in the best interest of our company and our stockholders.

We intend to continue our stockholder outreach following the filing of this Proxy Statement with the SEC, to seek support for our annual meeting proposals and to solicit additional feedback regarding governance, compensation and other matters of importance to our stockholders.

Our current governance practices include the following:

Director Nominees

The following table provides summary information regarding our two director nominees. For detailed information about each nominee’s background and areas of expertise, please see “Proposal No. 1—Election of Two Class I Directors.”

*As of April 20, 2026

Executive Compensation Highlights

Our executive compensation program is designed to support business performance and drive long-term stockholder value. Below are highlights of our executive compensation program.

2025 Executive Target Compensation Mix

The charts below illustrate the target 2025 pay mix (excluding benefits) for Gilmore O’Neill, our Chief Executive Officer, and for our other named executive officers, Linda C. Burkly, Ph.D., our Chief Scientific Officer, and Amy Parison, our Chief Financial Officer. Please see “Executive Compensation—2025 Summary Compensation Table” for amounts actually earned by each of them.

(1)Ms. Parison’s initial base annual salary for 2025 was $340,000 but was increased to $415,000 in connection with her promotion in March 2025 to Chief Financial Officer. For purposes of this chart, her base annual salary following promotion has been annualized.

Transition to All Options in Executive Equity Award Program

In connection with our acceleration from a clinical-stage company with bothin vivoandex vivo programs to a fullyin vivo focused preclinical company in December 2024, we updated our peer group to align with our new preclinical status and new corporate size and strategy. At that time, we reevaluated the structure of our equity incentive program to ensure alignment with this updated peer group and our new company profile and strategy. In February 2025, our Organization, Leadership, and Compensation Committee (“Compensation Committee”) determined that all employees would receive only time-based vesting stock options rather than a mix of time-based vesting restricted stock units (“RSUs”) and time-based vesting stock options, as had been awarded to employees in the past. For our officers, including the named executive officers, the Compensation Committee also determined to no longer award performance-based restricted stock units (“PSUs”), as it had done in previous years. The Compensation Committee determined that this transition in the type of equity awards made was appropriate in order to create momentum to drive long-term stockholder value and simplify the equity compensation program for our employees. This transition also reflects the guidance of the Compensation Committee’s independent compensation consultant that RSUs and PSUs are less common among preclinical biotechnology companies, including other companies in our updated peer group. The Compensation Committee believes that options are performance-based equity awards, particularly with our typical four-year vesting period, since the recipient recognizes value only if the company achieves objectives that result in recognized stockholder value and our stock price appreciates over time.

Stockholder Engagement Highlights

Stockholder Outreach

We are committed to strong corporate governance and the regular review of our corporate governance practices to continue building on our success and to create long-term stockholder value. As part of our regular corporate governance practice review, we conduct a robust stockholder outreach program to solicit and understand our stockholders’ perspectives on our practices and to better understand the reasons for their votes. We also engage with certain proxy advisory firms to understand their governance policies and related vote recommendations. Our Board and the Nominating and Corporate Governance Committee of our Board consider feedback received from this effort and other input from our stakeholders in determining what further governance actions, if any, are in the best interest of our company and its stockholders.

During the second half of 2025, we solicited feedback from institutional investors holding approximately 35% of our outstanding shares, and received feedback from investors holding approximately 12% of our outstanding shares. Our integrated engagement team included our Chief Financial Officer, our General Counsel, the head of our human resources team, and our investor relations team, and in certain engagements the chair of our Compensation Committee participated. We discussed numerous topics of stockholder interest, including our most recent “say on pay” vote results, corporate strategy, corporate governance, board skills and leadership, and other matters.