Annexon Biosciences

Tanruprubart (ANX005), a single-infusion antibody for Guillain-Barré syndrome, which has no FDA-approved drug today.

How it works: blocks C1q, the protein that starts the classical complement cascade, so the immune attack on the nerves is stopped at its first step.

Status: Phase 3 complete. Filed in Europe in January 2026 and under review there; Annexon said in August 2026 that it expects to file with the FDA in the fourth quarter of 2026.

Today's treatment: intravenous immunoglobulin or plasma exchange.

Source: Annexon second quarter 2026 results, August 12, 2026.

Two more uses of the same idea, blocking complement at C1q.

Eye: vonaprument (ANX007), injected into the eye, is in Phase 3 for geographic atrophy, the advanced dry form of age-related macular degeneration, with the Month 15 primary endpoint due in the fourth quarter of 2026 and the Month 24 result in the third quarter of 2027.

Brain: tanruprubart completed Phase 2 studies in Huntington's disease in 2022 and ALS in 2024, and Annexon's August 2026 update lists no active program in either disease.

It acts at the top of one branch of the cascade instead of near the bottom of all of them.

Approved drugs: Soliris and Ultomiris block C5, near the end of the cascade where all the pathways meet, and Fabhalta blocks factor B in the alternative pathway.

Annexon's drugs: C1q sits at the start of the classical pathway, the branch triggered when antibodies bind to tissue, so blocking it stops that branch before it starts and leaves the other pathways working.

Why it matters: Annexon's thesis is that the classical pathway is what tags nerve connections and retinal cells for destruction in the diseases it targets.

Brisbane, California, in the San Francisco Bay Area, and yes.

Founded: 2011.

Ticker: ANNX on the Nasdaq.

Products: none approved yet; Annexon is a rare disease specialist in the clinical stage.

Only through a clinical trial or an expanded access arrangement, since it is not approved anywhere as of October 2026.

Trials: the Guillain-Barré syndrome page lists recruiting studies.

Expanded access: our guide to continued access options explains how it works while an application is under review.

None that we track as of October 2026. No Annexon Biosciences label in the FDA's openFDA database matches a rare disease on Trial Friend, which usually means the company has no approved product yet or its approved drugs are for common conditions.

In development: the trials list on this page shows what Annexon Biosciences is recruiting for now, and the FDA calendar lists any application once a decision date is public.