SCHEDULE 13G/A 0001380585 XXXXXXXX LIVE 1 Common Stock, par value $0.001 per share 09/30/2025 0001527599 SYNLOGIC, INC. 87166L209 PO BOX 30 WINCHESTER MA 01890 Rule 13d-1(c) Radoff Bradley Louis X1 520000.00 0.00 520000.00 0.00 520000.00 N 4.4 IN SYNLOGIC, INC. This statement is filed by Bradley L. Radoff. The address of the principal office of Mr. Radoff is 2727 Kirby Drive, Unit 29L, Houston, Texas 77098. Mr. Radoff is a citizen of the United States of America. Y As of the close of business on September 30, 2025, Mr. Radoff directly beneficially owned 520,000 shares of Common Stock, par value $0.001 per share (the "Shares"). The following percentage is based on 11,698,919 Shares outstanding as of August 6, 2025, which is the total number of Shares outstanding as disclosed in the Issuer's Registration Statement on Form S-3 filed with the Securities and Exchange Commission on August 8, 2025. As of the close of business on September 30, 2025, Mr. Radoff beneficially owned approximately 4.4% of the outstanding Shares. See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. See Cover Pages Items 5-9. N Y Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Radoff Bradley Louis /s/ Bradley L. Radoff 11/13/2025