Keros Therapeutics, Inc.

2026 Annual Meeting of Stockholders

June 3, 2026 at 11:00 A.M. ET

THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS OF KEROS THERAPEUTICS, INC.

The undersigned hereby appoints Jasbir Seehra and Keith Regnante (the “Named Proxies”), and each or either of them, as the true and lawful attorneys of the undersigned, with full power of substitution and revocation, and hereby authorizes them, and each of them, to represent and to vote, as designated on the reverse side of this ballot, all of the shares of common stock of Keros Therapeutics, Inc. (the “Company”) that the undersigned is entitled to vote at the Annual Meeting of Stockholders (the “Annual Meeting”) to be held at 11:00 AM Eastern Time on June 3, 2026 and any adjournment or postponement thereof, conferring authority upon such true and lawful attorneys to vote in their discretion on such other matters as may properly come before the meeting and revoking any proxy heretofore given.

The Annual Meeting will be held virtually. In order to attend the Annual Meeting, you must register at https://web.viewproxy.com/keros/2026 by 11:59 PM Eastern Time on June 2, 2026. On the day of the Annual Meeting, if you have properly registered, you may enter the Annual Meeting by clicking on the link you received via email in your registration confirmations. Further instructions on how to attend and vote during the Annual Meeting are contained in the Proxy Statement in the sections titled “Questions and Answers About These Proxy Materials and Voting – How do I attend the Annual Meeting?” and “Questions and Answers About These Proxy Materials and Voting – How can I vote?”

This proxy, when properly executed, will be voted in the manner directed herein. If no such direction is made, this proxy will be voted in accordance with the Board of Directors’ recommendations.