KROS

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 4, 2026

Keros Therapeutics, Inc. (Exact name of registrant as specified in its charter)

Delaware 001-39264 81-1173868 (state or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.)

1050 Waltham Street, Suite 302 Lexington, Massachusetts 02421 (Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (617) 314-6297

Not applicable (Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol Name of each exchange on which registered

Common Stock, $0.0001 par value per share KROS The Nasdaq Stock Market LLC Preferred Share Purchase RightsN/AThe Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02    Results of Operations and Financial Condition.

On March 4, 2026, Keros Therapeutics, Inc. (the “Company”) issued a press release announcing its recent business highlights and financial results for the quarter and year ended December 31, 2025. A copy of the press release is furnished hereto as Exhibit 99.1 and is incorporated herein by reference. The information in this Item 2.02, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) or otherwise subject to the liabilities of that section. The information contained in this Item 2.02 and in the accompanying exhibit is not incorporated by reference in any filing of the Company under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as shall be expressly set forth by specific reference in such filing. Item 9.01     Financial Statements and Exhibits.

(d) Exhibits

Exhibit No. Description 99.1 Press Release dated March 4, 2026.

104Cover Page Interactive Data File (the cover page XBRL tags are embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

KEROS THERAPEUTICS, INC.

By: /s/ Jasbir Seehra Jasbir Seehra, Ph.D. Chief Executive Officer

Dated: March 4, 2026

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 5, 2025

Keros Therapeutics, Inc. (Exact name of registrant as specified in its charter)

Delaware 001-39264 81-1173868 (state or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer Identification No.)

1050 Waltham Street, Suite 302 Lexington, Massachusetts 02421 (Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (617) 314-6297

Not applicable (Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading Symbol Name of each exchange on which registered

Common Stock, $0.0001 par value per share KROS The Nasdaq Stock Market LLC Preferred Share Purchase RightsN/AThe Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02    Results of Operations and Financial Condition.

On November 5, 2025, Keros Therapeutics, Inc. (the “Company”) issued a press release announcing its financial results for the quarter ended September 30, 2025. A copy of the press release is furnished hereto as Exhibit 99.1 and is incorporated herein by reference. The information in this Item 2.02, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) or otherwise subject to the liabilities of that section. The information contained in this Item 2.02 and in the accompanying exhibit is not incorporated by reference in any filing of the Company under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as shall be expressly set forth by specific reference in such filing. Item 9.01     Financial Statements and Exhibits.

(d) Exhibits

Exhibit No. Description 99.1 Press Release dated November 5, 2025.

104Cover Page Interactive Data File (the cover page XBRL tags are embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

KEROS THERAPEUTICS, INC.

By: /s/ Jasbir Seehra Jasbir Seehra, Ph.D. Chief Executive Officer

Dated: November 5, 2025

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 15, 2025

Keros Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

Delaware

001-39264

81-1173868

(state or other jurisdiction

of incorporation)

(Commission

File Number)

(I.R.S. Employer

Identification No.)

1050 Waltham Street, Suite 302

Lexington, Massachusetts

(Address of principal executive offices)

02421

(Zip Code)

Registrant’s telephone number, including area code: (617) 314-6297

Not applicable

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

xPre-commencement

communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading

Symbol

Name of each exchange

on which registered

Common Stock, $0.0001 par value per share

KROS

The Nasdaq Stock Market LLC

Preferred Share Purchase Rights

N/A

The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Introductory Note.

In furtherance of its previously announced plan to initiate a process to return $375.0 million of excess capital to stockholders, on October 15, 2025, Keros Therapeutics, Inc. (the “Company”) announced (i) that it had entered into stock purchase agreements with certain entities affiliated with ADAR1 Capital Management (collectively, the “ADAR1 Parties”, and such stock purchase agreement, the “ADAR1 Repurchase Agreement”) and certain entities affiliated with Pontifax Venture Capital (collectively, the “Pontifax Parties”, and such stock purchase agreement, the “Pontifax Repurchase Agreement” and, together with the ADAR1 Repurchase Agreement, the “Repurchase Agreements”) to repurchase the shares of the Company’s common stock, $0.0001 par value per share (the “Common Stock”), held by the ADAR1 Parties and the Pontifax Parties, respectively, at a price of $17.75 per share, and (ii) following the entry into the Repurchase Agreements, that it intends to commence a tender offer to all holders of Common Stock to complete the return of capital to stockholders, subject to market conditions, at a cash purchase price of $17.75 per share. The Company expects to complete the repurchases under each of the Repurchase Agreements on or about October 15, 2025. The Company presently intends to commence the tender offer by the end of October 2025.

Item 1.01 Entry into a Material Definitive Agreement.

The information set forth in the Introductory Note is incorporated by reference in this Item 1.01.

The ADAR1 Parties, in the aggregate, beneficially own 5,389,264 shares of Common Stock representing in the aggregate approximately 13.3% of the Company’s issued and outstanding shares of Common Stock as of October 14, 2025. The Pontifax Parties, in the aggregate, beneficially own 4,787,331 shares of Common Stock, representing in the aggregate approximately 11.8% of the Company’s issued and outstanding shares of Common Stock as of October 14, 2025.

Pursuant to the terms and conditions of the Repurchase Agreements, the ADAR1 Parties and the Pontifax Parties (collectively, the “Repurchase Parties”) agreed to sell all of the shares of Common Stock beneficially owned by them, being an aggregate of 10,176,595 shares of Common Stock, to the Company at a per share purchase price of $17.75 per share (collectively, the “Repurchase Transactions”), for an aggregate purchase price of approximately $181 million. In addition, concurrently with the execution of the Pontifax Repurchase Agreement, each of Tomer Kariv and Ran Nussbaum delivered their resignations from the Company’s board of directors and all committees thereof.