X0306 4 2020-10-27 true 0001822462 Foghorn Therapeutics Inc. FHTX 0001362558 Abu Dhabi Investment Authority 211 CORNICHE STREET PO BOX 3600 ABU DHABI C0 0000 UNITED ARAB EMIRATES true Former 10% Owner 0001790748 Platinum International Investment Holding RSC Ltd 26TH FLOOR, AL KHATEM TOWER, ADGM SQUARE PO BOX 25642, AL MARYAH ISLAND ABU DHABI C0 NA UNITED ARAB EMIRATES true Former 10% Owner 0001790749 Platinum Falcon B 2018 RSC Ltd 26TH FLOOR, AL KHATEM TOWER, ADGM SQUARE PO BOX 25642, AL MARYAH ISLAND ABU DHABI C0 NA UNITED ARAB EMIRATES true Former 10% Owner Common Stock 2020-10-27 4 C 0 1081081 A 1081081 D Common Stock 2020-10-27 4 P 0 150000 16 A 1231081 D Series B Preferred Stock 2020-10-27 4 C 0 2000001 D Common Stock 1081081 0 D Upon the closing of the sale of shares of Common Stock of the Issuer to the public in a firm-commitment underwritten public offering pursuant to an effective registration statement under the Securities Act of 1933, as amended, resulting in at least $35,000,000 of gross proceeds to the Issuer, the Series B Preferred Stock converted automatically into Common Stock. Every 1.85 shares of Series B Preferred Stock converted into one share of Common Stock. There was no expiration date for the Series B Preferred Stock. Platinum Falcon B 2018 RSC Limited ("Platinum Falcon") directly holds the Series B Preferred Stock and the shares of Common Stock received upon conversion of the Series B Preferred Stock. Platinum International Investment Holding RSC Limited ("Platinum Holdings") is the sole owner of Platinum Falcon, and the Abu Dhabi Investment Authority ("ADIA" and, together with Platinum Falcon and Platinum Holdings, the "Reporting Persons") is the sole owner of Platinum Holdings. Therefore, Platinum Holdings and ADIA may also be deemed to beneficially own the Series B Preferred Stock and the shares of Common Stock received upon conversion of the Series B Preferred Stock. Platinum Falcon directly acquired 143,540 shares of Common Stock. Platinum Holdings and ADIA may also be deemed to beneficially own such shares of Common Stock. ADIA acquired directly 6,460 shares of Common Stock, and Platinum Holdings and Platinum Falcon disclaim beneficial ownership of such shares. /s/ Humaid Bin Butti Bin Humaid Bin Bishr AlMarri, Authorized Signatory of Abu Dhabi Investment Authority 2020-10-27 /s/ Ahmed Mohamed Ghubash, Authorized Signatory of Abu Dhabi Investment Authority 2020-10-27 /s/ Humaid Bin Butti Bin Humaid Bin Bishr AlMarri, Authorized Signatory of Platinum International Investment Holding RSC Limited 2020-10-27 /s/ Ahmed Mohamed Ghubash, Authorized Signatory of Platinum International Investment Holding RSC Limited 2020-10-27 /s/ Humaid Bin Butti Bin Humaid Bin Bishr AlMarri, Authorized Signatory of Platinum Falcon B 2018 RSC Limited 2020-10-27 /s/ Ahmed Mohamed Ghubash, Authorized Signatory of Platinum Falcon B 2018 RSC Limited 2020-10-27