X0508 4 2024-01-10 0 0001816736 Disc Medicine, Inc. IRON 0001591747 Bitterman Kevin C/O DISC MEDICINE, INC. 321 ARSENAL STREET, SUITE 101 WATERTOWN MA 02472 1 0 0 0 0 Common Stock 2024-01-10 4 S 0 20000 64.00 D 786160 I See footnote Common Stock 218326 I See footnote Common Stock 51000 I See footnote These shares are held by Atlas Venture Opportunity I, LP ("Opportunity I"). The general partner of Opportunity I is Atlas Venture Associates Opportunity I, LP ("Associates I"). Atlas Venture Associates Opportunity I, LLC ("Associates I LLC") is the general partner of Associates I. The Reporting Person is a member of Associates I LLC and disclaims beneficial ownership of such securities held by Opportunity I, except to the extent of his pecuniary interest therein, if any. These shares are held by Atlas Venture Opportunity II, LP ("Opportunity II"). The general partner of Opportunity II is Atlas Venture Associates Opportunity II, LP ("Associates II"). Atlas Venture Associates Opportunity II, LLC ("Associates II LLC") is the general partner of Associates II. The Reporting Person is a member of Associates II LLC and disclaims beneficial ownership of such securities held by Opportunity II, except to the extent of his pecuniary interest therein, if any. These shares are held by Atlas Venture Fund XII, L.P. ("Atlas XII"). The general partner of Atlas XII is Atlas Venture Associates XII, L.P. ("Associates XII"). Atlas Venture Associates XII, LLC ("Associates XII LLC") is the general partner of Associates XII. The Reporting Person is a member of Associates XII LLC and disclaims beneficial ownership of such securities held by Atlas XII, except to the extent of his pecuniary interest therein, if any. /s/ Ommer Chohan, Attorney-in-Fact 2024-01-12