X0306 4 2022-01-11 0 0001664710 Keros Therapeutics, Inc. KROS 0001808322 Lachey Jennifer C/O KEROS THERAPEUTICS, INC. 99 HAYDEN AVENUE, SUITE 120, BUILDING E LEXINGTON MA 02421 0 1 0 0 Chief Scientific Officer Common Stock 2022-01-11 4 M 0 2650 0.30 A 88350 D Common Stock 2022-01-11 4 S 0 320 52.01 D 88030 D Common Stock 2022-01-11 4 S 0 1196 53.56 D 86834 D Common Stock 2022-01-11 4 S 0 1134 54.45 D 85700 D Employee Stock Option (right to buy) 0.30 2022-01-11 4 M 0 2650 0.00 D 2028-03-25 Common Stock 2650 89955 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $51.695 to $52.45 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnotes (2), (3) and (4). The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $53.035 to $53.98 inclusive. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $54.075 to $54.85 inclusive. Immediately exercisable. /s/ Keith Regnante, Attorney-in-Fact 2022-01-13