MoonLake Immunotherapeutics is a clinical-stage biotech built around a single drug: sonelokimab (SLK), a Nanobody that inhibits both IL-17A and IL-17F, two proteins that drive inflammation in certain skin and joint diseases. MoonLake exclusively licensed SLK from Merck Healthcare KGaA, which originally developed the molecule with Ablynx. SLK is being developed across four inflammatory indications: hidradenitis suppurativa (HS), psoriatic arthritis (PsA), axial spondyloarthritis, and palmoplantar pustulosis. HS is the lead indication; MoonLake completed two Phase 3 trials and is targeting a BLA submission to the FDA in the second half of 2026, with a U.S. commercial launch targeted for the second half of 2027. PsA Phase 3 readouts are expected in 2026, and a PPP Phase 3 is expected to initiate in Q3 2026. MoonLake has no revenue today and funds operations from its cash balance. If SLK is approved, revenue would come from selling a specialty biologic through insurers and hospital systems, subject to royalties and milestone payments owed to Merck Healthcare under the license agreement. Manufacturing is fully outsourced to contract manufacturers. MoonLake argues SLK is differentiated by its small Nanobody format, which it claims enables deeper tissue penetration than conventional antibodies, along with a convenient monthly dosing schedule and a clean safety profile relative to other IL-17 agents.