MoonLake's Sonelokimab Hits Primary Endpoint in Phase 3 Psoriatic Arthritis Trial

MoonLake Immunotherapeutics (Nasdaq: MLTX) reported positive topline results from the phase 3 IZAR-1 trial evaluating sonelokimab in biologic-naive adults with active psoriatic arthritis (PsA), with the trial meeting its primary endpoint at week 16: 42.1 percent of patients receiving sonelokimab 60 mg with induction achieved an American College of Rheumatology 50 (ACR50) response.

Responses Across Joints and Skin

Key secondary endpoints were also met, including ACR20 in 66.5 percent of patients, Minimal Disease Activity (MDA) in 41.2 percent, and PASI90 — a 90 percent improvement in skin involvement — in 61 percent, demonstrating responses across musculoskeletal, skin and overall disease-activity domains, the company said. The blinded safety analysis showed a profile consistent with prior sonelokimab studies, with no new safety signals and a low dropout rate through week 16; the trial will continue through week 52 to evaluate durability and safety.

Per the unblinding protocol agreed with the FDA, the week-16 disclosure includes absolute response rates for the 60 mg induction arm, while comparative data versus placebo remain blinded until completion of the phase 3 program. IZAR-1 (NCT06641076) is part of the global IZAR program alongside IZAR-2 (NCT06641089), which is evaluating sonelokimab in patients with an inadequate response to TNF-alpha inhibitors and includes a risankizumab active reference arm.

Race to a New IL-17A/F Class

Sonelokimab is a trivalent nanobody that targets IL-17A, IL-17F and human serum albumin, positioning it to compete in the fast-growing IL-17 class that has been dominated by Novartis' Cosentyx and Lilly's Taltz. MoonLake, which held a positive final pre-BLA meeting with the FDA in May, is expected to use the IZAR data to support regulatory filings in psoriatic arthritis as it advances its larger ankylosing spondylitis program, where a prior phase 2 readout showed best-in-class potential, according to analysts cited by Dermatology Times.