Company: KROS
Filing Date: 2025-11-20
Form Type: SC TO-I/A
Source: 0001104659-25-114608
Chunk: 1

Company: Keros Therapeutics, Inc.
Filing Date: 2025-11-20
Form: SC TO-I/A
Chunk 1
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 provision(s) relied upon:

| ¨ | Rule 13e-4(i) (Cross-Border 
 Issuer Tender Offer)        |
| ¨ | Rule 14d-1(d) (Cross-Border 
 Third-Party Tender Offer)   |

<div align='center'>INTRODUCTION</div>

This Amendment No. 2 (this “Amendment”) amends and supplements
the Tender Offer Statement on Schedule TO originally filed with the Securities and Exchange Commission on October 20, 2025, as amended
and supplemented on November 19, 2025 (as amended and supplemented, the “Schedule TO”) relating to the offer by Keros Therapeutics,
Inc., a Delaware corporation (the “Company”), to purchase for cash up to an aggregate of 10,950,165 shares of its common stock,
par value $0.0001 per share, for an aggregate purchase price of up to $194.4 million, at a purchase price of $17.75 per share, less any
applicable withholding taxes and without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase dated
October 20, 2025 (the “Offer to Purchase”) and in the related Letter of Transmittal (the “Letter of Transmittal”
and, together with the Offer to Purchase, as they may be amended or supplemented from time to time, the “Tender Offer”), copies
of which were previously filed as Exhibits (a)(1)(A) and (a)(1)(B), respectively, to the Schedule TO.

This Amendment is intended
to satisfy the reporting requirements of Rule 13e-4(c)(4) under the Securities Exchange Act of 1934, as amended. Only those
items amended are reported in this Amendment. Except as specifically provided herein, the information contained in the Schedule TO remains
unchanged and this Amendment does not modify any of the information previously reported on the Schedule TO. This Amendment should be read
in conjunction with the Schedule TO and all of the exhibits thereto, including the Offer to Purchase and the Letter of Transmittal, as
each may be amended or supplemented from time to time.

ITEM 11. ADDITIONAL INFORMATION.

Item 11 of the Schedule TO
is hereby amended and supplemented by adding the following:

“On November 20,
2025, the Company issued a press release announcing the final results of the Tender Offer, which expired at 5:00 p.m., New