Sonelokimab Meets Primary End Point in Phase 3 Psoriatic Arthritis Trial

MoonLake Immunotherapeutics (NASDAQ: MLTX) announced positive topline results from the phase 3 IZAR-1 trial evaluating sonelokimab in biologic-naive adults with active psoriatic arthritis (PsA).¹ The trial (NCT06641076) met its primary end point at week 16, with 42.1% of patients receiving sonelokimab 60 mg with induction achieving an American College of Rheumatology 50 (ACR50) response. Key secondary end points were also met, including ACR20 (66.5%), Minimal Disease Activity (MDA; 41.2%), and Psoriasis Area and Severity Index 90 (PASI90; 61%).¹

Sonelokimab is an investigational trivalent Nanobody designed to inhibit interleukin (IL)-17A and IL-17F by targeting IL-17A/A, IL-17A/F, and IL-17F/F dimers.¹ The IZAR-1 results follow positive phase 2 ARGO data, in which sonelokimab demonstrated ACR50 and MDA responses in approximately 60% of patients at week 24.¹

MoonLake's lead indication, hidradenitis suppurativa (HS), is progressing toward a planned Biologics License Application submission by the end of September 2026, with PsA representing another late-stage target indication for sonelokimab.²

IZAR Phase 3 Program Evaluates Sonelokimab in PsA

IZAR-1 (NCT06641076) is a global, randomized, double-blind, placebo-controlled phase 3 trial evaluating sonelokimab in biologic disease-modifying antirheumatic drug-naive adults with active PsA.^1,3 It is part of the phase 3 IZAR program alongside IZAR-2 (NCT06641089), which is evaluating sonelokimab in patients with an inadequate response to tumor necrosis factor-alpha (TNF-α) inhibitors and includes a risankizumab active reference arm.¹

IZAR-1 also includes an evaluation of radiographic progression. Patients received sonelokimab 60 mg with induction dosing, with ACR50 response assessed as the primary end point at week 16.^1,3

Per the unblinding protocol agreed with the FDA, the week 16 topline disclosure includes absolute response rates for the sonelokimab 60-mg induction arm, while comparative data versus placebo remain blinded until completion of the phase 3 program.¹ MoonLake reported that all clinical end points assessed at week 16 for the 60-mg dose were met.¹

Secondary End Points Show Responses Across PsA Domains

Key secondary end points spanning musculoskeletal, skin, and functional domains were met for the sonelokimab 60-mg arm.¹ Among these patients, 66.5% achieved an ACR20 response, 41.2% achieved MDA, and 61% achieved a PASI90 response. According to MoonLake, the findings demonstrate responses across joint, skin, and overall disease activity measures in PsA.¹

Statistically significant improvements were also reported in patient-reported and physical function measures, including the Health Assessment Questionnaire Disability Index (HAQ-DI) and the SF-36 Physical Component Summary (PCS) score.¹

Safety Findings Consistent With Previous Sonelokimab Studies

The blinded safety analysis of IZAR-1 showed a profile consistent with previous sonelokimab studies, according to MoonLake, with no new safety signals identified.¹ The trial's dropout rate through week 16 was low and in line with other PsA studies, and patients will continue through week 52 to evaluate the durability of efficacy and safety.¹

Jorge Santos da Silva, PhD, founder and chief executive officer of MoonLake Immunotherapeutics, said,

The positive topline results from IZAR-1 represent an important milestone for MoonLake and, more importantly, for patients living with psoriatic arthritis. We are particularly encouraged by the strong efficacy observed across multiple clinically relevant endpoints simultaneously, which has been our focus.¹

MoonLake Continues Late-Stage Sonelokimab Development

Sonelokimab's dual inhibition of IL-17A and IL-17F builds on efficacy observed with IL-17A/F-targeted therapies and expands MoonLake's late-stage development program beyond HS. IZAR-2 enrollment is expected to be completed in the third quarter of 2026, with additional PsA and axial spondyloarthritis data from the P-OLARIS trial expected by early 2027.¹

References:

1. MoonLake announces positive topline results from the phase 3 IZAR-1 trial of sonelokimab in psoriatic arthritis demonstrating significant improvements across all clinical endpoints, and reports second quarter 2026 financial results. News release. MoonLake Immunotherapeutics. August 10, 2026. Accessed August 10, 2026. https://www.globenewswire.com/news-release/2026/08/10/3341679/0/en/moonlake-announces-positive-topline-results-from-the-phase-3-izar-1-trial-of-sonelokimab-in-psoriatic-arthritis-demonstrating-significant-improvements-across-all-clinical-endpoints.html
2. MoonLake Immunotherapeutics announces positive outcome from its final pre-BLA meeting with the U.S. FDA and reports first quarter 2026 financial results. News release. MoonLake Immunotherapeutics. May 11, 2026. Accessed August 10, 2026. https://ir.moonlaketx.com/news-releases/news-release-details/moonlake-immunotherapeutics-announces-positive-outcome-its-final
3. Evaluation of sonelokimab in patients with active psoriatic arthritis naive to biologic disease-modifying antirheumatic drug (IZAR-1). ClinicalTrials.gov. Updated June 12, 2026. Accessed August 10, 2026. NCT06641076. https://clinicaltrials.gov/study/NCT06641076