MoonLake’s Phase 3 IZAR-1 trial of sonelokimab in psoriatic arthritis achieved a 42.1% ACR50 response, with strong ACR20, MDA and PASI90 results.
Written By: Meghana Jinka, PharmD
Reviewed By: Pharmacally Editorial Team
MoonLake Immunotherapeutics reported positive topline Week 16 results from the Phase 3 IZAR-1 trial (NCT06641076) of sonelokimab in biologic-naïve adults with active psoriatic arthritis (PsA), with the 60 mg dose plus induction meeting the primary endpoint and all key clinical secondary endpoints. The treatment produced an ACR50 response in 42.1% of patients, while ACR20, Minimal Disease Activity (MDA), and PASI90 responses reached 66.5%, 41.2%, and 61%, respectively.
Broad Efficacy Across Psoriatic Arthritis Domains
Sonelokimab is an investigational Nanobody targeting IL-17A and IL-17F, two inflammatory cytokines involved in the pathogenesis of psoriatic disease. Blocking both cytokines could address several manifestations of PsA, including joint inflammation and associated skin disease.
PsA is a heterogeneous inflammatory disease that can affect peripheral joints, entheses, the skin, and physical function. Effective treatment therefore requires control across multiple disease domains rather than improvement in joint symptoms alone.
The IZAR-1 results showed activity across these domains. Alongside the 42.1% ACR50 response, 66.5% of patients achieved ACR20 at Week 16 and 41.2% reached MDA, a stringent measure reflecting low disease activity across multiple clinical domains. Among patients with concomitant skin involvement, 61% achieved PASI90.
Patient-Reported Outcomes Also Improved
Sonelokimab produced meaningful improvements in physical function and health-related quality of life. The mean change from baseline in the Health Assessment Questionnaire Disability Index (HAQ-DI) was -0.427, while the mean improvement in the SF-36 Physical Component Summary (PCS) score was 6.54.
IZAR-1 used ACR50 at Week 16 as its primary endpoint. The trial evaluated additional measures spanning musculoskeletal disease, skin involvement, physical function, and patient-reported health status.
The topline disclosure included absolute response levels for the 60 mg sonelokimab with-induction group, consistent with the unblinding protocol agreed with the FDA. Comparative analyses against placebo and detailed treatment-arm data remain blinded.
Safety Remains Consistent with Earlier Studies
The blinded safety analysis showed a safety profile consistent with previous sonelokimab clinical studies, with no new safety signals identified through Week 16. The trial also recorded a low dropout rate that MoonLake said was consistent with other PsA studies.
IZAR-1 does not include a standard-of-care comparator. Earlier ARGO data provided comparative evidence in biologic-naïve patients using adalimumab, while the Phase 3 IZAR-2 trial will evaluate sonelokimab against risankizumab in patients with TNF-refractory PsA.
MoonLake CEO Jorge Santos da Silva said the breadth of responses across clinically relevant endpoints reinforces the potential of sonelokimab in PsA. Chief Scientific Officer Kristian Reich similarly highlighted the importance of simultaneously addressing joint, skin, functional, and patient-reported manifestations of the disease.
IZAR Program Moves Toward Further Readouts
IZAR-1 remains blinded and will continue through Week 52 to assess durability of efficacy and safety, with the full readout expected in the first half of 2027. IZAR-2 is expected to complete enrollment in the third quarter of 2026.
The company expects several additional development milestones. MoonLake plans to submit a Biologics License Application for sonelokimab in hidradenitis suppurativa by the end of September 2026 and expects a PDUFA date allocation and a decision on Priority Review by the end of November. Enrollment in a Phase 3 program for palmoplantar pustulosis is expected to begin in the second half of 2026, while results from the P-OLARIS trial in PsA and axial spondyloarthritis are expected by late 2026 or early 2027.
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About the Writer
Meghana Jinka (LinkedIn) is a Pharm.D graduate with a strong interest in clinical pharmacy, clinical research, pharmacovigilance, and medical writing. She has developed expertise in evaluating scientific literature, interpreting clinical data, and communicating complex medical information in a clear and accessible manner. Through clinical training, patient counseling, and healthcare awareness activities, she has gained practical experience in evidence-based medicine and patient-centered care. Passionate about healthcare communication, Meghana is committed to developing accurate, engaging, and evidence-based healthcare documents that support healthcare professionals and the wider community.