Keros Therapeutics Reports Recent Business Highlights and First Quarter 2021 Financial Results Lexington, Massachusetts

Keros Therapeutics Reports Recent Business Highlights and First Quarter 2021 Financial Results

Lexington, Massachusetts - May 6, 2021 - Keros Therapeutics, Inc. ("Keros" or the "Company") (Nasdaq KROS), a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel treatments for patients suffering from hematological and musculoskeletal disorders with high unmet medical need, today provided a business update and reported financial results for the quarter ended March 31, 2021.

"As we maintain hope that the world has begun to turn the corner on the ongoing COVID-19 pandemic, we look forward to the upcoming year for Keros. The first quarter of 2021 provided a strong start, both operationally and from a financial position," said Jasbir S. Seehra, Ph.D., President and Chief Executive Officer. "We are continuing to enroll patients for our open-label Phase 2 clinical trial of KER-050 in patients with myelodysplastic syndromes, and we remain on track to report the initial data from Part 1 of that trial in mid-2021. We are also progressing towards the expected initiation of three additional Phase 2 clinical trials this year, one evaluating KER-050 and two evaluating KER-047, and are generating exciting preclinical data to both support our clinical efforts and expand our early pipeline."

KER-012 for the treatment of disorders associated with bone loss and for the treatment of pulmonary arterial hypertension

Keros will present data from a preclinical study of a research form of KER-012 on pulmonary and ventricular dysfunction in an established model of pulmonary arterial hypertension at the American Thoracic Society International Conference, to be held virtually May 14-19, 2021.

First Quarter 2021 Financial Results

Keros reported a net loss of $15.9 million in the first quarter of 2021 as compared to a net loss of $11.9 million in the first quarter of 2020. The increase in net loss for the first quarter was largely due to increased research and development efforts as well as the infrastructure to support operations as a publicly traded company.

Research and development expenses were $11.5 million for the first quarter of 2021 as compared to $8.5 million for the same period in 2020. The increase of $3.0 million was primarily due to additional preclinical and manufacturing activities related to KER-012, as well as an increase in personnel expenses, including additional share-based compensation cost, to support the advancement of our pipeline.

General and administrative expenses were $4.3 million for the first quarter of 2021 as compared to $2.0 million for the same period in 2020. The increase of $2.3 million was primarily due to increase in personnel expenses, which includes share-based compensation cost, to support Keros' organizational growth as well as expenses related to our directors and officers insurance.

Keros' cash and cash equivalents as of March 31, 2021 was $255.2 million compared to $265.9 million as of December 31, 2020. Keros expects that the cash and cash equivalents it had on hand at March 31, 2021 will fund its operating expenses and capital expenditure requirements into the fourth quarter of 2023.

About Keros Therapeutics, Inc.

Keros is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel treatments for patients suffering from hematologic and musculoskeletal disorders with high unmet medical need. Keros is a leader in understanding the role of the Transforming

Growth Factor-Beta family of proteins, which are master regulators of red blood cell and platelet production as well as of the growth, repair and maintenance of muscle and bone. Keros' lead protein therapeutic product candidate, KER-050, is being developed for the treatment of low blood cell counts, or cytopenias, including anemia and thrombocytopenia, in patients with myelodysplastic syndromes and in patients with myelofibrosis. Keros' lead small molecule product candidate, KER-047, is being developed for the treatment of anemia resulting from iron imbalance, as well as for the treatment of fibrodysplasia ossificans progressiva. Keros' third product candidate, KER-012, is being developed for the treatment of disorders associated with bone loss, such as osteoporosis and osteogenesis imperfecta, and for the treatment of pulmonary arterial hypertension.

Cautionary Note Regarding Forward-Looking Statements

Statements contained in this press release regarding matters that are not historical facts are "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Words such as anticipates, believes, expects, intends, "plans," "potential," projects," "would" and future or similar expressions are intended to identify forward-looking statements. Examples of these forward-looking statements include statements concerning Keros' expectations regarding its growth, strategy, progress and timing of its preclinical studies and clinical trials for KER-050 and KER-047 the potential impact of COVID-19 on Keros' ongoing and planned preclinical studies, clinical trials, business and operations Keros' plans to present preclinical data at an upcoming conference and Keros' expected cash runway. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. These risks and uncertainties include, among others Keros' limited operating history and historical losses Keros' ability to raise additional funding to complete the development and any commercialization of its product candidates Keros' dependence on the success of its lead product candidates, KER-050 and KER-047 that Keros may be delayed in initiating, enrolling or completing any clinical trials competition from third parties that are developing products for similar uses Keros' ability to obtain, maintain and protect its intellectual property Keros' dependence on third parties in connection with manufacturing, clinical trials and preclinical studies and risks relating to the impact on Keros' business of the COVID-19 pandemic or similar public health crises.

These and other risks are described more fully in Keros' filings with the Securities and Exchange Commission ("SEC"), including the "Risk Factors" section of the Company's Annual Report on Form 10-K, filed with the SEC on March 25, 2021, and its other documents subsequently filed with or furnished to the SEC. All forward-looking statements contained in this press release speak only as of the date on which they were made. Except to the extent required by law, Keros undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

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KEROS THERAPEUTICS, INC.

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KEROS THERAPEUTICS, INC.

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