MoonLake Immunotherapeutics (Nasdaq: MLTX) reported positive Week 16 topline results from the Phase III IZAR-1 trial of sonelokimab in biologic-naïve psoriatic arthritis (PsA) patients on August 10, 2026, meeting all primary and key secondary endpoints. The data support MoonLake's ambition to build a multi-indication franchise around its single asset with the company preparing to submit a Biologics License Application (BLA) for sonelokimab in hidradenitis suppurativa (HS) by end of September 2026.
Sonelokimab is an approximately 40 kDa humanized Nanobody that simultaneously inhibits the IL-17A/A, IL-17A/F, and IL-17F/F dimers driving inflammation, with a third domain binding human serum albumin to extend half-life and facilitate tissue penetration at sites of inflammatory edema.
In IZAR-1, a global, randomized, double-blind, placebo-controlled trial enrolling biologic-naïve adults with active PsA, 42.1% of patients treated with sonelokimab 60 mg with induction achieved the primary endpoint of American College of Rheumatology 50 (ACR50) response at Week 16. Across key secondary endpoints, 66.5% achieved ACR20, 41.2% achieved Minimal Disease Activity (MDA), and 61% of patients with concomitant skin involvement achieved Psoriasis Area and Severity Index 90 (PASI90). Statistically significant improvements were also reported in Health Assessment Questionnaire Disability Index (HAQ-DI; mean change −0.427) and SF-36 Physical Component Summary (PCS; +6.54). Consistent with a pre-specified FDA unblinding protocol, comparative data versus placebo remain blinded until the full Week 52 readout, expected in H1 2027.
The blinded safety analysis indicated a profile consistent with prior sonelokimab studies, with no new safety signals and a low drop-out rate through Week 16.
Interpretation of the response rates remains limited by the unusual topline disclosure, as comparative results versus placebo will remain blinded until the full Week 52 analysis expected in H1 2027 under a prespecified FDA unblinding protocol. The parallel IZAR-2 Phase III trial is evaluating sonelokimab in patients with inadequate response to TNF inhibitors and includes AbbVie's Skyrizi (risankizumab) as an active reference arm; enrollment is expected to complete in Q3 2026.