X0202 SCHEDULE 13G/A 0001425738 XXXXXXXX LIVE 6 Common Stock, par value $0.001 per share 07/01/2026 0001528115 Annexon, Inc. 03589W102 1400 Sierra Point Parkway Bldg C, Suite 200 Brisbane CA 94005 Rule 13d-1(c) Redmile Group, LLC DE 0.00 17918459.00 0.00 17918459.00 17918459.00 N 9.9 IA OO Reported information current as of July 8, 2026. The information in Item 4 relating to the shares of the Issuer's common stock ("Common Stock") that are or may be deemed beneficially owned by Redmile Group, LLC ("Redmile") is incorporated herein by reference. Jeremy C. Green X0 0.00 17918459.00 0.00 17918459.00 17918459.00 N 9.9 HC IN Reported information current as of July 8, 2026. The information in Item 4 relating to the shares of Common Stock that are or may be deemed beneficially owned by Jeremy C. Green is incorporated herein by reference. RedCo II Offshore SPV LLC E9 0.00 9802458.00 0.00 9802458.00 9802458.00 N 5.5 FI OO Reported information current as of July 8, 2026. The information in Item 4 relating to the shares of Common Stock that are or may be deemed beneficially owned by RedCo II Offshore SPV LLC is incorporated herein by reference. Annexon, Inc. 1400 Sierra Point Parkway, Bldg C, Suite 200, Brisbane, CA 94005 Redmile Group, LLC Jeremy C. Green RedCo II Offshore SPV LLC * * This amendment No. 6 reports the addition of RedCo II Offshore SPV LLC as a reporting person in this jointly filed Schedule 13G following its initial acquisition of more than 5% of the Issuer's outstanding common stock as of July 1, 2026. Redmile Group, LLC 900 Larkspur Landing Circle, Suite 270 Larkspur, California 94939 Jeremy C. Green c/o Redmile Group, LLC (NY Office) 45 W. 27th Street, Floor 11 New York, NY 10001 RedCo II Offshore SPV LLC c/o Redmile Group, LLC 900 Larkspur Landing Circle, Suite 270 Larkspur, California 94939 Redmile Group, LLC: Delaware Jeremy C. Green: United Kingdom RedCo II Offshore SPV LLC: Cayman Islands Y Redmile Group, LLC - 17,918,459 (1) Jeremy C. Green - 17,918,459 (1) RedCo II Offshore SPV LLC - 9,802,458 (2) Redmile Group, LLC - 9.9% Jeremy C. Green - 9.9% RedCo II Offshore SPV LLC - 5.5% Redmile Group, LLC - 0 Jeremy C. Green - 0 RedCo II Offshore SPV LLC - 0 Redmile Group, LLC - 17,918,459 (1) Jeremy C. Green - 17,918,459 (1) RedCo II Offshore SPV LLC - 9,802,458 (2) Redmile Group, LLC - 0 Jeremy C. Green - 0 RedCo II Offshore SPV LLC - 0 Redmile Group, LLC - 17,918,459 (1) Jeremy C. Green - 17,918,459 (1) RedCo II Offshore SPV LLC - 9,802,458 (2) (1) As of July 8, 2026, Redmile's and Jeremy C. Green's beneficial ownership of the Issuer's Common Stock is comprised of (i) 14,548,896 shares of Common Stock and (ii) 3,369,563 shares of Common Stock issuable upon exercise of certain pre-funded warrants to purchase Common Stock (the "Warrants"). The shares of Common Stock issuable upon exercise of the Warrants reported as beneficially owned by the Reporting Persons represent the maximum number of shares of Common Stock that could be issued upon exercise of those Warrants subject to the 9.99% beneficial ownership limitation (the "Beneficial Ownership Limitation"). All of such shares of Common Stock and the Warrants are directly owned by certain investment vehicles, including RedCo II Offshore SPV LLC ("RedCo II Offshore"), for which Redmile is the investment manager (the "Redmile Funds"). Redmile may be deemed to beneficially own these securities in its capacity as their investment manager with discretion to vote and dispose of all shares of Common Stock held by the Redmile Funds. Mr. Green also may be deemed to beneficially own these securities as the principal of Redmile. Redmile and Mr. Green each disclaims beneficial ownership of these securities, except to the extent of its or his pecuniary interest in such securities, if any. (2) As of July 8, 2026, RedCo II Offshore may be deemed to beneficially own (i) 6,432,895 shares of Common Stock, and (ii) 3,369,563 shares of Common Stock issuable upon exercise of the Warrants directly held by RedCo II Offshore. The shares of Common Stock issuable upon exercise of the Warrants reported as beneficially owned by RedCo II Offshore represent the maximum number of shares of Common Stock that could be issued to RedCo II Offshore upon exercise of those Warrants subject to the Beneficial Ownership Limitation. Percentage based on: (i) 163,842,538 shares of Common Stock outstanding as of May 4, 2026, as reported by the Issuer in its Form 10-Q for the quarterly period ended March 31, 2026 filed with the SEC on May 7, 2026; plus (ii) 15,521,422 shares of Common Stock issued and, under the Beneficial Ownership Limitation, issuable upon exercise of the Warrants directly held by the Redmile Funds (including RedCo II Offshore). Y Y N See the response to Item 4. 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. Redmile Group, LLC /s/ Jeremy C. Green 07/08/2026 Jeremy C. Green /s/ Jeremy C. Green 07/08/2026 RedCo II Offshore SPV LLC /s/ Jeremy C. Green 07/08/2026