X0508 4 2023-11-17 0001492422 Apellis Pharmaceuticals, Inc. APLS 0001721108 Dunlop A. Sinclair C/O APELLIS PHARMACEUTICALS, INC. 100 FIFTH AVENUE, 3RD FLOOR WALTHAM MA 02451 1 0 Common Stock 2023-11-17 4 S 0 8894 49.991 D 122403 D Common Stock 216679 I Indirect Owner (Epidarex) Common Stock 31855 I Indirect Owner (Masa) This transaction was executed in multiple trades at prices ranging from $49.9509 - $50.125. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. The securities are held by Epidarex and the reporting person, a general partner of Epidarex, may be deemed to have voting and dispositive power over the shares held by Epidarex. The reporting person disclaims beneficial ownership over the shares held by Epidarex except to the extent of his pecuniary interest therein. The securities are held by MASA and the reporting person, a managing partner of MASA, may be deemed to have voting and dispositive power over the shares held by MASA. The reporting person disclaims beneficial ownership over the shares held by MASA except to the extent of his pecuniary interest therein. /s/ David Watson, attorney-in-fact for Sinclair Dunlop 2023-11-21