ANX-105

Initial Clinical Data Expected from the Phase 2 ARCHER Trial of ANX007 in Geographic Atrophy in Mid-2023 Initial Clinical Data Anticipated from the Phase 1b Trial of ANX009 in Lupus Nephritis in 1H’23 Enrollment Expected to be Completed in Phase 3 Trial in Guillain-Barré Syndrome During 2H’23, with Initial Topline Results Expected in 1H’24 Strong Financial Position with Operating Runway into 2025, with Multiple Mid-Stage and Pivotal Clinical Trial Readouts Expected Across 2023 and 2024 BRISBANE, Calif., May 08, 2023 (GLOBE NEWSWIRE) -- Annexon, Inc. (Nasdaq: ANNX), a clinical-stage biopharmaceutical company developing a new class of complement medicines for patients with classical complement-mediated autoimmune, neurodegenerative and ophthalmic disorders, today reported first quarter 2023 financial results and highlighted recent progress across its portfolio of complement therapies. “The first quarter was another period of strong execution of our flagship and next-wave clinical-stage programs for the treatment of complement-mediated diseases of the body, brain and eye, thereby enabling multiple clinical catalysts over the next several quarters,” said Douglas Love, president and CEO of Annexon. “Our platform approach of blocking classical complement-driven inflammation where it initiates on diseased tissue has demonstrated robust patient benefit in multiple autoimmune and neurodegenerative diseases. We are excited by the potential of demonstrating patient benefit in our first ophthalmologic indication with the Phase 2 ANX007 ARCHER trial in geographic atrophy, whereby stopping the initiation of the inflammatory classical complement cascade may reduce retinal inflammation and improve macular health. We are eagerly anticipating results from our pivotally designed and executed ARCHER trial in mid-2023.” “In autoimmune, we expect to report initial clinical results from our Phase 1b program in lupus nephritis during the first half of 2023 and share data during the second half of the year with ANX1502, our first-in-class, small molecule oral inhibitor of the classical pathway, which we anticipate advancing into several autoimmune conditions. Importantly, enrollment is progressing well in our pivotal ANX005 Phase 3 program in Guillain-Barré Syndrome with clinical results expected during the first half of 2024,” Mr. Love continued. “With multiple clinical milestones expected over the next 18 months, these readouts have the potential to accelerate our transition into a leading late-stage biopharmaceutical company focused on the treatment of complement-mediated diseases.” Recent Highlights Annexon has prioritized advancing four flagship programs with the goal of creating near-term value for patients and physicians: Guillain-Barré syndrome (GBS), Huntington’s disease (HD), geographic atrophy (GA) and a first-in-kind oral small molecule, ANX1502, for autoimmune diseases. Beyond these programs, there is a range of next-wave programs for the treatment of amyotrophic lateral sclerosis (ALS), lupus nephritis (LN) and other earlier-stage autoimmune and neurodegenerative diseases, where additional investments are planned based upon meeting certain development and funding objectives. Flagship Programs ANX005 in GBS: Enrollment in the Phase 3 pivotal trial of ANX005 in patients with GBS is progressing and expected to be completed in second half of 2023, with initial topline clinical results anticipated during the first half of 2024. ANX007 in GA: Last patient treated and initial clinical data from ANX007 ARCHER Phase 2 trial in GA expected to be reported mid-2023, followed by additional data after the conclusion of the six-month off-treatment period by the end of 2023. ANX1502 in autoimmune diseases: Enrollment underway in second cohort of the multiple-ascending dose Phase 1a trial in healthy volunteers. Data expected to be reported in the second half of 2023. ANX005 in HD: Initiate a planned Phase 2/3 trial in HD in 2023, upon obtaining funding for full program development. Next Wave Programs ANX009 in LN: Initial clinical data from Phase 1b signal-finding trial of ANX009 for LN expected during the first half of 2023. ANX005 in ALS: Enrollment continues in the Phase 2a trial, following encouraging preliminary results which showed slowing of disease progression. Additional data expected in the second half of 2023. ANX105: Report initial data from the single-ascending dose Phase 1 trial of ANX105 in healthy volunteers in 2023. First Quarter 2023 Financial Results Cash and operating runway: Cash and cash equivalents and short-term investments were $228.2 million as of March 31, 2023. Based on the current operating plan, Annexon continues to expect its cash, cash equivalents and marketable securities as of March 31, 2023, to be sufficient to fund the company’s operating expenses and capital expenditure requirements related to currently ongoing clinical trials into 2025. Research and development (R&D) expenses: R&D expenses were $32.3 million for the quarter ended March 31, 2023, reflecting the advancement of our late-stage flagship programs, including GBS and GA. This compared to $27.0 million for the quarter ended March 31, 2022. General and administrative (G&A) expenses: G&A expenses were $8.9 million for the quarter ended March 31, 2023, compared to $8.4 million for the quarter ended March 31, 2022. Net loss: Net loss was $38.7 million or $0.52 per share for the quarter ended March 31, 2023, compared to $35.4 million or $0.92 per share for the quarter ended March 31, 2022. About Annexon Annexon (Nasdaq: ANNX) is a clinical-stage biopharmaceutical company seeking to bring game-changing medicines to patients with classical complement-mediated diseases of the body, brain and eye. The classical complement pathway within the immune system, when overactivated, drives inflammation in a host of autoimmune, neurodegenerative and ophthalmic diseases. Annexon is advancing a new class of complement medicines targeting the early classical cascade and all downstream pathway components that contribute to disease, while selectively preserving the beneficial immune functions of other complement pathways. Annexon is rigorously developing a pipeline of diversified product candidates across multiple mid- to late-stage clinical trials, with clinical data anticipated throughout 2023 and beyond. Forward Looking Statements This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “design,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “positioned,” “potential,” “predict,” “seek,” “should,” “suggest,” “target,” “on track,” “will,” “would” and other similar expressions that are predictions of or indicate future events and future trends, or the negative of these terms or other comparable terminology. All statements other than statements of historical facts contained in this press release are forward-looking statements. These forward-looking statements include, but are not limited to, statements about: anticipated milestones; obtaining funding for advancement of the company’s programs; cash operating runway; the potential benefits from treatment with anti-C1q therapy; timing of data reports; and continuing advancement of the company’s portfolio. Forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including, but not limited to, risks and uncertainties related to: the company’s history of net operating losses; the company’s ability to obtain necessary capital to fund its clinical programs; the early stages of clinical development of the company’s product candidates; the effects of COVID-19 or other public health crises on the company’s clinical programs and business operations; the company’s ability to obtain regulatory approval of and successfully commercialize its product candidates; any undesirable side effects or other properties of the company’s product candidates; the company’s reliance on third-party suppliers and manufacturers; the outcomes of any future collaboration agreements; and the company’s ability to adequately maintain intellectual property rights for its product candidates. These and other risks are described in greater detail under the section titled “Risk Factors” contained in the company’s Annual Report on Form 10-K and Quarterly Reports on Form 10-Q and the company’s other filings with the SEC. Any forward-looking statements that the company makes in this press release are made pursuant to the Private Securities Litigation Reform Act of 1995, as amended, and speak only as of the date of this press release. Except as required by law, the company undertakes no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise. Investor Contact: Chelcie Lister THRUST Strategic Communications chelcie@thrustsc.com Media Contact: Sheryl Seapy Real Chemistry 949-903-4750 sseapy@realchemistry.com ANNEXON, INC. Condensed Consolidated Statements of Operations (in thousands, except share and per share amounts) (unaudited) Three Months Ended March 31, 2023 2022 Operating expenses: Research and development (1) $ 32,345 $ 26,998 General and administrative (1) 8,897 8,428 Total operating expenses 41,242 35,426 Loss from operations (41,242 ) (35,426 ) Interest and other income, net 2,566 53 Net loss $ (38,676 ) $ (35,373 ) Net loss per share, basic and diluted $ (0.52 ) $ (0.92 ) Weighted-average shares used in computing net loss per share, basic and diluted 73,855,642 38,563,384 (1) Includes the following stock-based compensation expense: Research and development $ 2,251 $ 1,959 General and administrative $ 2,356 $ 2,293 ANNEXON, INC. Condensed Consolidated Balance Sheets (in thousands) March 31, December 31, 2023 2022 (Unaudited) Assets Current assets: Cash and cash equivalents $ 144,120 $ 140,020 Short-term investments 84,045 102,637 Prepaid expenses and other current assets 4,371 5,441 Total current assets 232,536 248,098 Restricted cash 1,032 1,032 Property and equipment, net 16,334 16,838 Operating lease right-of-use assets 18,864 19,128 Other non-current assets 12 — Total assets $ 268,778 $ 285,096 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 10,346 $ 7,416 Accrued liabilities 10,677 13,448 Operating lease liabilities, current 1,534 1,316 Other current liabilities 384 180 Total current liabilities 22,941 22,360 Operating lease liabilities, non-current 30,976 31,542 Total liabilities 53,917 53,902 Stockholders’ equity: Common stock 53 48 Additional paid-in capital 691,963 669,780 Accumulated other comprehensive loss (217 ) (372 ) Accumulated deficit (476,938 ) (438,262 ) Total stockholders' equity 214,861 231,194 Total liabilities and stockholders’ equity $ 268,778 $ 285,096

Initial Clinical Data from Phase 2 Trial of ANX007 in Patients with Geographic Atrophy On-track for Mid-2023 Oral Small Molecule ANX1502, for Autoimmune Indications, Advances into Multi-Ascending Dose Trial Well-capitalized with Operating Runway into 2025, Including through Multiple Mid-stage and Pivotal Clinical Trial Readouts Anticipated in 2023 and 2024 BRISBANE, Calif., March 06, 2023 (GLOBE NEWSWIRE) -- Annexon, Inc. (Nasdaq: ANNX), a clinical-stage biopharmaceutical company developing a new class of complement medicines for patients with classical complement-mediated autoimmune, neurodegenerative and ophthalmic disorders, today outlined anticipated upcoming milestones across its portfolio of complement therapies and reported fourth quarter and full year 2022 financial results. “2022 was a year of focused execution at Annexon, establishing a strong foundation on which to drive near- and long-term value across our deep portfolio of complement therapeutics,” said Douglas Love, president and CEO of Annexon. “We expect this year to be even stronger for Annexon, as we execute the pivotal and late-stage development of our four flagship programs across all three of our therapeutic franchises – autoimmune, ophthalmology and neurodegeneration. We’re prioritizing our focus and resources on well-supported, value creating programs, including our Phase 2 program for geographic atrophy with data anticipated mid-year, using our first-in-class up- and down-stream complement approach, and our potentially paradigm-shifting oral small molecule, ANX1502, for autoimmune indications. Overall, Annexon is well-positioned to continue executing our goals with a passionate and talented team, a strong balance sheet and multi-year runway, and a steady cadence of anticipated clinical catalysts over the next six to 18 months – all designed to deliver game-changing medicines to patients.” Recent Pipeline Progress Dosing Initiated in Phase 1 Multiple-Ascending Dose (MAD) Trial of ANX1502: Annexon has initiated dosing in its Phase 1 MAD trial of ANX1502 in healthy volunteers. The study is designed to evaluate the safety and tolerability of twice-daily dosing of ANX1502 for two weeks. To date, ANX1502 has been generally well-tolerated in the ongoing single-ascending dose (SAD) trial with no dose-limiting safety signals observed. The company also plans to expand development of ANX1502 into additional autoimmune indications with strong scientific rationale, including multifocal motor neuropathy (MMN), in early 2024. Key 2023-2024 Anticipated Milestones Flagship Programs Autoimmune: Complete expanded enrollment in the ongoing pivotal Phase 3 trial of ANX005 in patients with Guillain-Barré syndrome (GBS) in 2023 with pivotal data anticipated in the first half of 2024 Autoimmune: Complete the ongoing SAD trial of ANX1502 and identify the maximum tolerated dose; execute the ongoing MAD trial in healthy volunteers; and initiate a proof-of-concept study in patients with cold agglutinin disease (CAD) in 2023 Ophthalmology: Complete the ongoing Phase 2 trial of ANX007 in patients with geographic atrophy (GA) and report initial data in mid-2023 followed by additional data by the end of 2023 after the conclusion of the six-month off-treatment period Neurodegeneration: Initiate a randomized, double-blind, placebo-controlled Phase 2/3 trial for ANX005 in patients with Huntington’s disease (HD) in 2023 Additional Complement Programs Autoimmune: Report data from the Phase 1b signal-finding trial of ANX009, which applies a precision medicine approach and is enrolling patients with lupus nephritis (LN) who have high baseline complement activity, in the first half of 2023 Neurodegeneration: Report full data from the Phase 2a signal-finding trial in patients with amyotrophic lateral sclerosis (ALS) in 2023 Next-generation development: Report initial data from the SAD study of ANX105 in healthy volunteers in 2023 Fourth Quarter and Full Year 2022 Financial Results Cash and operating runway: Cash and cash equivalents and short-term investments were $242.7 million as of December 31, 2022. Annexon continues to expect its cash, cash equivalents and marketable securities as of December 31, 2022, to be sufficient to fund the company’s current operating plan into 2025. Research and development (R&D) expenses: R&D expenses were $28.5 million for the quarter ended December 31, 2022, and $112.5 million for the year ended December 31, 2022, compared to $27.2 million for the quarter ended December 31, 2021, and $100.0 million for the year ended December 31, 2021. General and administrative (G&A) expenses: G&A expenses were $8.2 million for the quarter ended December 31, 2022, and $33.1 million for the year ended December 31, 2022, compared to $10.2 million for the quarter ended December 31, 2021, and $30.6 million for the year ended December 31, 2021. Net loss: Net loss was $34.4 million for the quarter ended December 31, 2022, and $141.9 million for the year ended December 31, 2022, compared to $37.4 million for the quarter ended December 31, 2021, and $130.3 million for the year ended December 31, 2021. About Annexon Annexon (Nasdaq: ANNX) is a clinical-stage biopharmaceutical company seeking to bring game-changing medicines to patients with classical complement-mediated diseases of the body, brain and eye. The classical complement cascade is a seminal pathway within the immune system that anchors and drives a host of autoimmune, neurodegenerative and ophthalmic diseases. Annexon is advancing a new class of complement medicines targeting the early classical cascade and all downstream pathway components that contribute to disease, while selectively preserving the beneficial immune functions of other complement pathways. Annexon is rigorously developing a pipeline of diversified product candidates across multiple mid- to late-stage clinical trials, with clinical data anticipated throughout 2023 and beyond. Forward Looking Statements This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “design,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “positioned,” “potential,” “predict,” “seek,” “should,” “suggest,” “target,” “on track,” “will,” “would” and other similar expressions that are predictions of or indicate future events and future trends, or the negative of these terms or other comparable terminology. All statements other than statements of historical facts contained in this press release are forward-looking statements. These forward-looking statements include, but are not limited to, statements about: anticipated milestones; cash operating runway; the potential benefits from treatment with anti-C1q therapy; timing of data reports; and continuing advancement of the company’s broad portfolio. Forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including, but not limited to, risks and uncertainties related to: the company’s history of net operating losses; the company’s ability to obtain necessary capital to fund its clinical programs; the early stages of clinical development of the company’s product candidates; the effects of COVID-19 or other public health crises on the company’s clinical programs and business operations; the company’s ability to obtain regulatory approval of and successfully commercialize its product candidates; any undesirable side effects or other properties of the company’s product candidates; the company’s reliance on third-party suppliers and manufacturers; the outcomes of any future collaboration agreements; and the company’s ability to adequately maintain intellectual property rights for its product candidates. These and other risks are described in greater detail under the section titled “Risk Factors” contained in the company’s Annual Report on Form 10-K and Quarterly Reports on Form 10-Q and the company’s other filings with the SEC. Any forward-looking statements that the company makes in this press release are made pursuant to the Private Securities Litigation Reform Act of 1995, as amended, and speak only as of the date of this press release. Except as required by law, the company undertakes no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise. Investor Contact: Chelcie Lister THRUST Strategic Communications chelcie@thrustsc.com Media Contact: Sheryl Seapy Real Chemistry 949-903-4750 sseapy@realchemistry.com ANNEXON, INC. Condensed Consolidated Statements of Operations (in thousands, except share and per share amounts) Three Months Ended Year Ended December 31, December 31, 2022 2021 2022 2021 (unaudited) (unaudited) Operating expenses: Research and development (1) $ 28,535 $ 27,217 $ 112,501 $ 100,066 General and administrative (1) 8,160 10,241 33,098 30,647 Total operating expenses 36,695 37,458 145,599 130,713 Loss from operations (36,695 ) (37,458 ) (145,599 ) (130,713 ) Interest and other income (expense), net 2,312 87 3,652 390 Net loss (34,383 ) (37,371 ) (141,947 ) (130,323 ) Net loss attributable to common stockholders $ (34,383 ) $ (37,371 ) $ (141,947 ) $ (130,323 ) Net loss per share attributable to common stockholders, basic and diluted $ (0.48 ) $ (0.97 ) $ (2.60 ) $ (3.40 ) Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted 72,368,539 38,479,221 54,673,572 38,316,273 _______________________ (1) Includes the following stock-based compensation expense: Research and development $ 2,365 $ 2,280 $ 8,874 $ 8,610 General and administrative $ 2,468 $ 2,075 $ 9,642 $ 7,652 ANNEXON, INC. Condensed Consolidated Balance Sheets (in thousands) December 31, December 31, 2022 2021 Assets Current assets: Cash and cash equivalents $ 140,020 $ 74,843 Short-term investments 102,637 167,872 Prepaid expenses and other current assets 5,441 4,978 Total current assets 248,098 247,693 Restricted cash 1,032 1,166 Property and equipment, net 16,838 17,848 Operating lease right-of-use assets 19,128 20,333 Total assets $ 285,096 $ 287,040 Liabilities and Stockholders' Equity Current liabilities: Accounts payable $ 7,416 $ 11,153 Accrued liabilities 13,448 9,250 Operating lease liabilities, current 1,316 1,202 Other current liabilities 180 139 Total current liabilities 22,360 21,744 Operating lease liabilities, non-current 31,542 33,387 Total liabilities 53,902 55,131 Stockholders’ equity: Common stock 48 39 Additional paid-in capital 669,780 528,365 Accumulated other comprehensive loss (372 ) (180 ) Accumulated deficit (438,262 ) (296,315 ) Total stockholders' equity 231,194 231,909 Total liabilities and stockholders’ equity $ 285,096 $ 287,040