The complement cascade has been one of the most lucrative story arcs in rare disease.
Alexion built a $39B company on Soliris, then Ultomiris.
Apellis turned pegcetacoplan into a franchise.
Novartis paid $3.5B for Chinook in part for iptacopan, which hits complement factor B.
Commit Biologics just raised €21.5M to weaponize the complement system against B cells — no effector cell component required.
All of it has been monoclonal antibodies and peptides. Infusions. Subcutaneous injections every few weeks. Lifetime dosing.
Argo Biopharma just dosed the first patients in Phase 2 of BW-40202.
It’s not an antibody. It’s an siRNA. And it silences complement factor B at the source.
The Phase 2 is running in two indications that usually get separate drugs: paroxysmal nocturnal hemoglobinuria (PNH) and IgA nephropathy (IgAN). Both are complement-mediated. Both have approved drugs already. Both have patients who still aren’t doing well on them.
Drugs hitting the complement cascade
Phase 2
Approved
Approved
Approved
Argo is the only siRNA in the mix.
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The siRNA angle matters for a specific reason. iptacopan is a twice-daily oral. Pegcetacoplan is a twice-weekly subcutaneous. Ultomiris is every eight weeks by IV.
An siRNA for CFB could plausibly dose once a quarter, or once every six months. That’s the whole reason Alnylam has been able to price its siRNA drugs the way it does, despite being in diseases with existing options.
Argo isn’t new to this, by the way. The pipeline already has RNA-focused shots on goal in Lp(a), hepatitis B, hereditary angioedema, and mixed dyslipidemia. BW-40202 is the immunology bet.
No efficacy data disclosed yet. No enrollment numbers. That’s normal for a first-patient-dosed announcement.
What’s worth watching is whether Argo can deliver the kind of durable CFB knockdown that makes a quarterly shot beat a twice-daily pill. If the answer is yes, the complement cascade gets rewritten again.
