Keros Therapeutics, Inc.

SCHEDULE 14A INFORMATION

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Keros Therapeutics, Inc.

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April 22, 2026

To our stockholders:

2025 was a year of pivotal change for Keros Therapeutics. We continued to advance our strategy to develop protein therapeutics designed to deliver meaningful, disease-modifying benefits for patients, while maintaining our focus on long-term value creation for our stockholders. Guided by scientific rigor and disciplined execution, we have taken deliberate actions to optimize our performance and position the Company to capitalize on the opportunities ahead, aligning our resources around the development of our key clinical program, rinvatercept (KER-065). As we enter 2026, we are continuing to take steps to reallocate resources and streamline Keros’ operations to create a more efficient structure that best supports patient needs and positions us to deliver on our objectives.

In 2025, we made the strategic decision to exclusively prioritize the clinical advancement of our lead product candidate, rinvatercept, an asset we believe has therapeutic potential for individuals living with Duchenne muscular dystrophy (“DMD”). As part of that initiative, we discontinued all material internal development activities related to cibotercept (KER-012). This decision follows the previously announced termination of the development of cibotercept in pulmonary arterial hypertension (“PAH”), following the analysis of all available safety and efficacy data from the TROPOS Phase 2 clinical trial in patients with PAH. When presented with data that raised potential concerns, we acted promptly and decisively, prioritizing patient safety. These portfolio changes were not easy, but they were deliberate and necessary to sharpen our strategic focus, reinforce disciplined development, and position the Company to advance our highest-priority program while maintaining our commitment to returning capital to stockholders.

We are encouraged by positive data from the Phase 1 clinical trial of rinvatercept, with the trial achieving its key objectives for safety, tolerability, pharmacokinetics and pharmacodynamics. Building on these results, we are progressing toward commencement of a Phase 2 clinical trial of rinvatercept in patients with DMD. We are also evaluating additional neuromuscular indications in which rinvatercept may provide meaningful benefit, including amyotrophic lateral sclerosis (“ALS”). Our initial observations indicate that the observed effect of rinvatercept on skeletal muscle may offer a differentiated approach to treating ALS. In March 2026, we announced that we entered into an agreement with the Massachusetts General Hospital for the design of a Phase 2 clinical trial evaluating rinvatercept in patients with ALS within the Healey ALS MyMatch program, led by the Sean M. Healey & AMG Center for ALS at Mass General Brigham. We expect to engage with regulators in the second half of 2026 to discuss the design of a potential Phase 2 clinical program for ALS. Supported by encouraging early data and disciplined execution, we believe the continued advancement of rinvatercept positions Keros to generate sustainable long-term growth and stockholder value.

As part of our commitment to ongoing Board refreshment and effective governance, we have continued to evolve the composition of our Board in alignment with the Company’s strategic priorities. Over the past five years, three new directors have been added to the Board, broadening its expertise and strengthening its oversight capabilities. Collectively, our directors bring deep experience across the biotechnology and pharmaceutical sectors, including drug discovery, clinical development, regulatory strategy, and commercialization. Their combined scientific, operational, and strategic expertise provides strong guidance to support the Company’s execution and generate sustainable value creation. In March 2026, Charles Newton was appointed to the Keros Board, bringing deep expertise in healthcare finance and capital markets, as well as a strong track record of supporting companies through key value inflection points. We believe his experience and perspective enhance the Board’s capabilities as we advance our clinical and strategic priorities. In conjunction with this appointment, Carl Gordon stepped down from the Board following years of dedicated service. We appreciate his many contributions to Keros and wish him well in his future endeavors.

In line with our strategic realignment efforts and consistent with a disciplined capital allocation framework, we took meaningful steps this year to optimize our capital structure and return excess capital to stockholders while allocating the necessary resources to advance our highest-priority programs. Following a comprehensive review of strategic alternatives, our Board authorized a $375 million capital return program that we completed through a combination of share repurchases, including a tender offer that concluded in November 2025. This capital return program enabled us to deliver immediate value to our stockholders while still maintaining financial flexibility to advance our clinical pipeline and position Keros for long-term value creation.

As we move forward in 2026, the Board remains confident in Keros’ ability to deliver on its strategic priorities through focused clinical execution, disciplined capital allocation, and continued progress toward key development milestones.

Thank you for your investment in Keros Therapeutics, continued trust and support.

Sincerely,

Jasbir Seehra, Ph.D.

President and Chief Executive Officer

KEROS THERAPEUTICS, INC.

1050 Waltham Street, Suite 302

Lexington, Massachusetts 02421

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To Be Held On June 3, 2026

To the Stockholders of Keros Therapeutics, Inc.:

NOTICE IS HEREBY GIVEN that the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Keros Therapeutics, Inc., a Delaware corporation (the “Company”), will be held on Wednesday, June 3, 2026 at 11:00 a.m. Eastern time in a virtual meeting format only, live via audio webcast for the following purposes:

To elect two (2) nominees for Class III director, Jean-Jacques Bienaimé and Charles Newton, each to hold office until the 2029 Annual Meeting of Stockholders and until their successors are duly elected and qualified.

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To ratify the selection by the Audit Committee of the Board of Directors of Deloitte & Touche LLP as the independent registered public accounting firm of the Company for its fiscal year ending December 31, 2026.

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To approve, on an advisory basis, the compensation of the Company’s named executive officers as disclosed in the proxy statement.

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To conduct any other business properly brought before the Annual Meeting.

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These items of business are more fully described in the proxy statement accompanying this Notice.

The record date for the Annual Meeting was April 6, 2026 (the “Record Date”). Only stockholders of record at the close of business on the Record Date may vote at the Annual Meeting or any adjournment or postponement thereof.

By Order of the Board of Directors,

Esther Cho

Corporate Secretary

Lexington, Massachusetts

April 22, 2026