of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Director — Muneer Satter: Routine resignation of a non-executive director with an immediate replacement, explicitly stated to be without disagreement.

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth in

Entry into a Material Definitive Agreement. On July 30, 2026 (the “Effective Date”), Annexon, Inc. (the “Company”) entered into a Loan and Security Agreement (the “Agreement”) with Oxford Finance LLC, as collateral agent (in such capacity, the “Collateral Agent”), and certain lenders from time to time party thereto (collectively, the “Lenders”). The Agreement provides for term loans in an aggregate principal amount of up to $200.0 million. Under the terms of the Agreement, the Lenders have ag…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Results of Operations and Financial Condition. On March 30, 2026, Annexon, Inc. (the “Company”) announced certain financial results for the fourth quarter and the year ended December 31, 2025. A copy of the Company’s press release, titled “Annexon Reports Fourth Quarter and Year-End 2025 Financial Results, Portfolio Progress and Key Anticipated Milestones” is furnished pursuant to

Chairman of the Board of Directors — Thomas G. Wiggans: Mr. Wiggans notified the Company of his intent to retire as a member of the Board and not stand for reelection at the 2026 Annual Meeting.

Entry into a Material Definitive Agreement. On November 12, 2025, Annexon, Inc. (the “ Company ’) entered into an underwriting agreement (the “ Underwriting Agreement ”) with Goldman Sachs & Co. LLC, TD Securities (USA) LLC and Wells Fargo Securities, LLC, as representatives of the several underwriters listed therein (collectively, the “ Underwriters ”), to issue and sell 25,096,153 shares (the “ Shares ”) of the Company’s common stock, par value $0.001 per share (the “ Common Stock ”) at a p…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Material Modification to the Rights of Security Holders. 2022 Common Warrant Amendments On June 23, 2025, Annexon, Inc. (the “Company”) and certain holders thereof entered into amendments to the common stock purchase warrants (the “Common Warrants”) originally issued pursuant to that certain Securities Purchase Agreement, dated July 7, 2022, by and among the Company and the purchasers party thereto (the “Common Warrant Amendment”). The Common Warrant Amendment extends the term of such Common…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Results of Operations and Financial Condition. On March 3, 2025, Annexon, Inc. (the “Company”) announced certain financial results for the fourth quarter and the year ended December 31, 2024. A copy of the Company’s press release, titled “Annexon Reports Fourth Quarter and Year-End 2024 Financial Results, Portfolio Progress and Key Anticipated Milestones” is furnished pursuant to

Director — William Jones: Appointment of William Jones as a Class I director.

Other Events. On December 16, 2024, Annexon, Inc. (“Annexon” or the “Company”) issued a press release (the “RWE Press Release”) announcing positive topline results from a real-world evidence study of ANX005 in Guillain-Barré Syndrome. Working in collaboration, the International GBS Outcome Study (“IGOS”) investigators and Annexon established a matched cohort of patients treated with ANX005 30 mg/kg in the completed Phase 3 study conducted outside the U.S. with a cohort of real-world patients…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Entry into a Material Definitive Agreement. On June 5, 2024, Annexon, Inc. (the “ Company ”) entered into an underwriting agreement (the “ Underwriting Agreement ”) with J.P. Morgan Securities LLC, Jefferies LLC, TD Securities (USA) LLC and BofA Securities, Inc., as representatives of the several underwriters listed therein (collectively, the “ Underwriters ”), to issue and sell 13,001,120 shares (the “ Shares ”) of the Company’s common stock, par value $0.001 per share (the “ Common Stock ”)…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

Entry into a Material Definitive Agreement. On December 20, 2023, Annexon, Inc. (the “C ompan y’) entered into an underwriting agreement (“ Underwriting Agreement ”) with Jefferies LLC and Cowen and Company, LLC (the “ Underwriters ”), to issue and sell 25,035,000 shares (the “ Shares ”) of the Company’s common stock, par value $0.001 per share (the “ Common Stock ”) at a price of $2.880 per share and, in lieu of Common Stock, certain investors were issued pre-funded warrants to purchase an a…

Other Events. ANX007 On December 20, 2023, the Company outlined its global registrational program for ANX007, a potentially best-in-class C1q and classical complement inhibitor for the treatment of GA. The Company intends to initiate a comprehensive pivotal program with (1) ARCHER II, a global sham-controlled trial designed to confirm results from the previously completed Phase 2 ARCHER trial and to potentially expedite regulatory approval in Europe and (2) a second trial, ARROW, an injection…

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.

of this Current Report on Form 8-K, including Exhibit 99.1, shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission made by the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing, except as expressly set forth by specific reference in such a filing.