X0508 4/A 2023-07-11 2023-12-29 0 0001528115 Annexon, Inc. ANNX 0001818525 Yednock Ted C/O ANNEXON, INC. 1400 SIERRA POINT PKWY, BLDG C, STE 200 BRISBANE CA 94005 0 1 0 0 EVP & Chief Innovation Officer 1 Common Stock 2023-07-11 4 S 0 1057 3.8361 D 37885 D Common Stock 2023-12-27 4 M 0 10615 1.4096 A 48500 D Common Stock 2023-12-27 4 M 0 10385 1.8501 A 58885 D Common Stock 2023-12-27 4 S 0 21000 4.5222 D 37885 D Common Stock 21000 I By Spouse Late reporting of transaction being made as a result of an administrative oversight. The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs"). This transaction was executed in multiple trades in prices ranging from $3.72 to $3.90, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote. Includes 33,559 restricted stock units. The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 28, 2023. Column 5 is being amended to reflect the correct amount of securities beneficially owned following reported transaction. Reflects the correct amount of securities beneficially owned that was unintentionally omitted from the Form 4 filed December 29, 2023. On December 29, 2023, the reporting person filed a Form 4 that inadvertently omitted to report the reporting person's (1) shares of common stock that were sold to cover tax withholding obligations in connection with the vesting of restricted stock units and (2) then current Column 5 holdings of common stock beneficially owned, as initially reported by the reporting person on Form 3. This amendment reports the correct amount of securities beneficially owned. /s/ Jennifer Lew, as Attorney-in-Fact 2024-01-23