Mechanism of action

Iptacopan binds to complement factor B (FB), a key component of the alternative complement pathway.
This inhibits formation of the C3 convertase (C3bBb), thereby:

Reducing C3 cleavage and C3b generation
Preventing downstream formation of C5 convertase and the membrane attack complex (MAC)


By acting upstream (proximal) in the complement cascade, iptacopan controls:

C3b‑mediated extravascular hemolysis
Terminal complement‑mediated intravascular hemolysis


Importantly, it selectively blocks the alternative pathway, leaving the classical and lectin pathways intact to preserve host immune defense.

Indication

Approved indications (FDA / EMA):

Paroxysmal nocturnal hemoglobinuria (PNH) in adults
Reduction of proteinuria in adults with primary IgA nephropathy (IgAN) at risk of rapid disease progression
Complement 3 glomerulopathy (C3G) to reduce proteinuria