X0508 4 2023-08-28 0001811623 PaxMedica, Inc. PXMD 0001809613 Derby Michael C/O PAXMEDICA, INC. 303 SOUTH BROADWAY, SUITE 125 TARRYTOWN NY 10591 0 0 1 0 1 Common Stock 2023-08-28 4 S 0 7000 0.4931 D 454886 D Common Stock 2023-08-29 4 S 0 6540 0.4845 D 448346 D Common Stock 7336745 I TardiMed Sciences, LLC The sales reported in this Form 4 were effected pursuant to the Reporting Person's pre-existing Rule 10b5-1 trading plan to, inter alia, pay tax withholding on vested RSUs. The sale price represents the weighted average sale price of the shares sold ranging from $0.4767 to $0.5005 per share. Upon request by the Commission staff, the Issuer, or a security holder of the Issuer, the reporting person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. The sale price represents the weighted average sale price of the shares sold ranging from $0.4844 to $0.5024 per share. Upon request by the Commission staff, the Issuer, or a security holder of the Issuer, the reporting person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4. The reporting person is the managing partner of TardiMed Sciences, LLC and has sole voting and dispositive control over the shares of Common Stock held by the entity. The reporting person disclaims beneficial ownership of the securities except to the extent of his pecuniary interest therein. /s/ Stephen D. Sheldon, Jr. Attorney-in-Fact 2023-08-30