X0508 4 2023-08-28 0001811623 PaxMedica, Inc. PXMD 0001811802 Weisman Howard J. C/O PAXMEDICA, INC. 303 SOUTH BROADWAY, SUITE 125 TARRYTOWN NY 10591 1 1 0 0 Chairman and CEO 1 Common Stock 2023-08-28 4 S 0 12000 0.4882 D 689729 D Common Stock 2023-08-29 4 S 0 9596 0.4846 D 680133 D Common Stock 2023-08-30 4 S 0 22535 0.4461 D 657598 D 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 $0.4702 to $0.5246 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 $0.50 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 $0.4101 to $0.49 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. /s/ Stephen D. Sheldon, Jr. Attorney-in-Fact 2023-08-30