Company: KROS
Filing Date: 2025-10-15
Form Type: SC TO-C
Source: 0001104659-25-099513
Chunk: 0

Company: Keros Therapeutics, Inc.
Filing Date: 2025-10-15
Form: SC TO-C
Chunk 0
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<div align='center'>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)</div>

| 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)         |

<div align='center'>Registrant’s telephone number, including area code: (617) 314-6297

Not applicable

(Former name or former address, if changed since last report.)</div>

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))                          |

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

<div align='center'>Securities registered pursuant to Section 12(b) of the Act:</div>

| 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