Does Blocking IL-17F Actually Matter?
Two of the newest PsA drugs block IL-17F as well as IL-17A; the older ones block only IL-17A. A plain walk through what the extra target actually buys: clear help on the skin, no proven help on the joints yet, and a fungal cost in the middle.
Sonelokimab met its Phase 3 endpoint in psoriatic arthritis in August 2026, the second drug engineered to neutralise IL-17F alongside IL-17A. The first, bimekizumab, is already approved; secukinumab and ixekizumab block IL-17A alone. On the joints, the dual drugs post ACR50s around 43–44% versus 35–40% for the A-only incumbents — but the trials aren't comparable, so the gap isn't proof. On the skin the story firms up: PASI90 around 61–69% versus 33–49%, plus a head-to-head in psoriasis where bimekizumab out-cleared secukinumab. Blocking IL-17F looks like a skin benefit, not yet a joint one.