Annexon, Inc.

What the company does

• Biopharmaceutical company developing targeted immunotherapies that inhibit the classical complement cascade, starting with C1q.
• Platform is designed to block the classical cascade (C1q, C4, C3, C5) while preserving lectin and alternative pathways, with the goal of reducing chronic inflammation and tissue damage in the body, brain, and eye.
• Therapeutic focus areas: autoimmune diseases, neurodegenerative diseases, and ophthalmology (retina).

Core therapeutic approach

• Upstream inhibition of the classical complement pathway to prevent immune cell recruitment, immune attack on targeted cells, and membrane damage, while maintaining immune function from other complement pathways.

Pipeline and key product candidates

• Tanruprubart

  • Indication: Guillain-Barré Syndrome (GBS).
  • Stage: Phase 3 completed in 2024 (Bangladesh and Philippines sites); topline results showed statistically meaningful improvement on the GBS-Disability Scale at week 8 for the 30 mg/kg dose.
  • Dosing: 30 mg/kg (one-time IV infusion) produced rapid and durable benefit; 75 mg/kg did not meet the primary endpoint.
  • Regulatory: Marketing Authorization Application (MAA) filed with the EMA in January 2026; orphan designation from the EMA; FDA Fast Track and orphan designations.
  • Regulatory path: Western (U.S./EU) data from the FORWARD study expected to support Western generalizability; FDA alignment is ongoing for a BLA submission in 2026.
  • Enrollment: 241 patients in Bangladesh and the Philippines.

• Vonaprument

  • Indication: Geographic Atrophy (GA) associated with dry AMD.
  • Stage: Phase 3 ARCHER II completed enrollment (659 patients); topline data expected in Q4 2026.
  • Design: Global registration program aligned with FDA/EMA guidance; single study analyzed as two US/EU sub-studies per FDA guidance.
  • Regulatory: EMA PRIME designation and ongoing regulatory engagement.

• ANX1502

  • Indication focus: Autoimmune diseases (oral small molecule).
  • Mechanism: Inhibits activated C1s to block the classical cascade upstream.
  • Stage: Phase 1 (SAD/MAD) in healthy volunteers completed; enteric-coated tablet formulation being evaluated in an open-label CAD proof-of-concept study with data anticipated in 2026.

• ANX009

  • Indication focus: Lupus nephritis (LN) and other indications.
  • Stage: Phase 1b signal-finding trial completed; subcutaneous delivery showed durable C1q target engagement and downstream complement inhibition; increased circulating PACAs; further development options are being evaluated.

• Wider program

  • Tanruprubart, vonaprument, ANX009, and ANX1502 are part of a broader program that includes exploration in Huntington’s disease (HD) and amyotrophic lateral sclerosis (ALS).

Other program notes

• Next-wave programs include Tanruprubart for Huntington’s disease and ALS, with Phase 2 data supporting precision-medicine approaches.
• ANX1502 aims to enable oral dosing and long-term treatment options for autoimmune diseases.
• IP strategy covers multiple patent families addressing anti-C1q antibodies, C1q/C1s targets, and small-molecule inhibitors (ANX1502) with expiries roughly 2034–2046 absent extensions.

Intellectual property

• Portfolio comprises 19 patent families (as of March 13, 2026), including:
  • Stanford-licensed patents covering anti-C1q antibodies (e.g., Tanruprubart, Vonaprument, ANX009) with expiries 2026–2030.
  • In-house families covering anti-C1q antibodies and methods of use (expiries 2034–2037).
  • Small-molecule programs (ANX1502) with expiries around 2041–2043.
  • Additional families covering compositions, formulations, and dosing regimens (expiries up to 2046).
• Exclusive license with Stanford University (ongoing milestones, royalties, and potential termination rights).
• International patent protection across multiple jurisdictions; trade secrets and know-how protected via confidentiality agreements.

Corporate and regulatory footprint

• Headquarters and primary facility: Brisbane, California.
• Employees: 96 full-time employees as of December 31, 2025; 77 in research and development.
• Company stage: Clinical development.
• Cash position: Approximately $238.3 million in cash and short-term investments as of December 31, 2025; runway into the second half of 2027.
• Financing activities: At-the-market program authorized; March 2026 Sales Agreement established to allow up to $150 million in at-the-market offerings; prior financings include pre-funded and common warrants outstanding.
• Stock: As of December 31, 2025, 149,362,800 shares of common stock outstanding; potential dilution from warrants (42,293,577 issuable from pre-funded warrants and 6,877,622 from common warrants). Founders and insiders retain a substantial stake; executive officers, directors, and 5%+ holders collectively hold 48% of outstanding voting stock.

Market context and therapeutic rationale

• GBS: Rapid-onset autoimmune neuropathy without FDA-approved targeted therapies; Tanruprubart aims to halt early classical cascade–driven damage.
• GA: Leading cause of blindness with limited treatment options targeting the complement cascade; Vonaprument targets the early classical pathway to preserve retinal structure and vision.
• Autoimmune and neurodegenerative diseases: C1q inhibition has potential across diseases where classical pathway–driven inflammation and synapse pruning contribute to pathology.

Clinical program highlights

• GBS Phase 3 (30 mg/kg) showed a statistically meaningful improvement on the GBS-Disability Scale at week 8, 28 fewer days on ventilation through week 26, and a 31-day faster walk to independent ambulation in prespecified analyses.
• The 75 mg/kg dose in the GBS Phase 3 did not meet the primary endpoint; the 30 mg/kg dose defined the optimal duration window (approximately one week of C1q inhibition).
• Real-world evidence for GBS indicated faster motor recovery and lower likelihood of ventilation versus IVIg/PE in matched Western cohorts.
• GA ARCHER II enrolled 659 patients; topline readout planned for late 2026.
• ARCHER data indicate C1q inhibition preserves ellipsoid zone and photoreceptor structure on some measures; EMA and FDA designations support regulatory engagement.

Manufacturing and operations

• Manufacturing relies on contract manufacturers with multi-site supply chains, including EU-based suppliers for Tanruprubart and Vonaprument.
• Plans are in place to transfer processes and establish manufacturing readiness for potential BLA/MAA submissions; the company is evaluating long-term supply agreements and alternative sources to mitigate supply risk.

Summary of current status

• Tanruprubart (GBS) is in late-stage regulatory submission discussions with the EMA; Western expansion data are expected to support a BLA filing in 2026.
• Vonaprument (GA) is in Phase 3 with ARCHER II data expected in 2026 and an expressed regulatory path for U.S./EU approvals.
• ANX1502 and ANX009 represent oral and subcutaneous approaches for autoimmune and neuroinflammatory indications with early clinical data supporting target engagement.
• Financial position supports ongoing late-stage development, with efforts underway to extend runway through at-the-market offerings and other financings.