MoonLake's lead drug hit every endpoint in a 16-week psoriatic arthritis trial. Its only comparison was placebo.

Swiss biotech MoonLake said its lead drug sonelokimab, a nanobody, or small single-domain antibody fragment derived from camelid heavy-chain-only antibodies, hit every primary and secondary clinical endpoint in a 16-week Phase 3 trial of adults with active psoriatic arthritis who had never taken a biologic. Psoriatic arthritis is the chronic inflammatory disease that causes joint pain, swelling, and stiffness in people with or at risk of psoriasis; MoonLake cites roughly 2.4 million U.S. patients.

At week 16, 42.1% of patients reached ACR50, at least a 50% improvement in joint symptoms, against a much smaller share on placebo. The release also reported 66.5% ACR20, 41.2% minimal disease activity, and 61% PASI90 skin clearance in the subset with skin involvement (GlobeNewswire, FierceBiotech, BioSpace).

IZAR-1 used placebo as its only control arm, so the readout proves the drug works in biologic-naive adults without showing how it compares with AbbVie's Humira or Skyrizi. Full arm data stay blinded until the trial completes in the first half of 2027 (ClinicalTrials.gov).

IZAR-2, the program's second Phase 3, runs sonelokimab head-to-head against Skyrizi in patients who failed a TNF inhibitor such as Humira. That result, not Monday's topline, will decide where sonelokimab sits in psoriatic arthritis care (ACR abstract, RTT News).