X0306 4 2020-11-17 0 0001664710 Keros Therapeutics, Inc. KROS 0001726334 Pontifax Management 4 G.P. (2015) Ltd. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 0001726039 Pontifax (Israel) IV, L.P. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 0001726029 Pontifax (Cayman) IV L.P. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 0001726030 Pontifax (China) IV L.P. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 0001793769 Pontifax Late Stage Fund L.P. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 0001793770 Pontifax Late Stage GP Ltd. 14 SHENKAR STREET, BEIT OFEK HERZLIYA PITUACH L3 46140 ISRAEL 0 0 1 0 Common Stock 2020-11-17 4 P 0 26634 50.00 A 2288151 I See footnote Common Stock 2020-11-17 4 P 0 12966 50.00 A 1122768 I See footnote Common Stock 2020-11-17 4 P 0 14400 50.00 A 1228326 I See footnote Common Stock 2020-11-17 4 P 0 6000 50.00 A 155262 I See footnote The securities are held by Pontifax (Israel) IV, L.P. ("Israel IV"). Pontifax Management 4 G.P. (2015) Ltd. ("Management 4") is the ultimate general partner of Israel IV. As a result Management 4 may be deemed to share voting and dispositive power with respect to the shares held by Israel IV. Management 4 disclaims beneficial ownership of such shares, except to the extent of its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise. The securities are held by Pontifax (Cayman) IV, L.P. ("Cayman IV"). Management 4 is the ultimate general partner of Cayman IV. As a result Management 4 may be deemed to share voting and dispositive power with respect to the shares held by Cayman IV. Management 4 disclaims beneficial ownership of such shares, except to the extent of its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise. The securities are held by Pontifax (China) IV, L.P. ("China IV"). Management 4 is the ultimate general partner of China IV. As a result Management 4 may be deemed to share voting and dispositive power with respect to the shares held by China IV. Management 4 disclaims beneficial ownership of such shares, except to the extent of its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise. The securities are held by Pontifax Late Stage Fund, L.P. ("Late Stage"). Pontifax Late Stage GP Ltd. ("Late Stage GP") is the general partner of Late Stage and the sole shareholder of Late Stage GP is Mr. Shlomo Karako. Pursuant to Strategic Alliance Agreement, dated August 9, 2018, between Late Stage, Israel IV, Cayman IV and China IV (collectively the, "Pontifax IV Funds"), Late Stage invests side-by-side with the Pontifax IV Funds. By virtue of the strategic relationship, Management 4 may be deemed to share voting and dispositive power with respect to the shares held by Late Stage in a manner similar to the voting and investment power with respect to the shares held by each of the Pontifax IV Funds. Each of Management 4 and Late Stage GP disclaims beneficial ownership of such shares, except to the extent of its pecuniary interest therein, and the inclusion of the shares in this report shall not be deemed to be an admission of beneficial ownership of the reported shares for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise. /s/ Keith Regnante, Attorney-in-Fact for Pontifax Management 4 G.P. (2015) Ltd. 2020-11-19 /s/ Keith Regnante, Attorney-in-Fact for Pontifax (Israel) IV L.P. 2020-11-19 /s/ Keith Regnante, Attorney-in-Fact for Pontifax (Cayman) IV L.P. 2020-11-19 /s/ Keith Regnante, Attorney-in-Fact for Pontifax (China) IV L.P. 2020-11-19 /s/ Keith Regnante, Attorney-in-Fact for Pontifax Late Stage Fund, L.P. 2020-11-19 /s/ Keith Regnante, Attorney-in-Fact for Pontifax Late Stage GP Ltd. 2020-11-19