MoonLake Immunotherapeutics has initiated its Phase 3 IZAR clinical program, evaluating the Nanobody® sonelokimab in patients with active psoriatic arthritis (PsA). The program consists of two trials, IZAR-1 and IZAR-2, conducted across sites in the United States, Europe, and Latin America. This initiative follows positive results from the Phase 2 ARGO trial and aims to address the unmet needs in managing inflammation and pain across multiple domains affected by PsA.
PsA is a chronic, debilitating inflammatory condition affecting peripheral joints, skin, entheses, nails, and axial joints. Affecting up to 30% of patients with psoriasis, PsA significantly impairs function and reduces quality of life. The IZAR program seeks to confirm the effectiveness of sonelokimab in treating PsA, with the ultimate goal of helping more patients reach their treatment goals across multiple domains.
IZAR Trial Design
The Phase 3 IZAR program is expected to enroll approximately 1,500 adult patients across two trials, IZAR-1 (NCT06641076) and IZAR-2 (NCT06641089). Both trials are global, randomized, double-blind, and placebo-controlled, designed to evaluate the efficacy and safety of sonelokimab over 52 weeks. IZAR-1 will enroll biologic-naïve patients and include an evaluation of radiographic progression. IZAR-2 will enroll patients with an inadequate response to tumor necrosis factor-α inhibitors (TNF-IR) and will be the first to include risankizumab, an IL-23 inhibitor, as an active reference arm. The primary endpoint for both trials is the American College of Rheumatology (ACR) 50 response compared to placebo at Week 16. Key secondary endpoints will also be assessed at Week 16. The IZAR program will assess 60mg and 120mg doses of sonelokimab, with the primary endpoint readout expected in H1 2026.
Sonelokimab Mechanism of Action
Sonelokimab is an investigational Nanobody® designed to directly target sites of inflammation by inhibiting the IL-17A/A, IL-17A/F, and IL-17F/F dimers. Its smaller size as a Nanobody® compared to antibodies allows it to better penetrate and treat difficult-to-reach inflamed tissues. Evidence suggests that activation of the IL-17 pathway plays a crucial role in the pathophysiology of PsA.
Expert Commentary
Alan Kivitz, MD, MACR, an ARGO and IZAR investigator, stated, “I’m excited to be part of the Phase 3 IZAR program as an investigator, focusing on the Nanobody® sonelokimab for psoriatic arthritis... The Phase 2 ARGO trial yielded particularly promising results, with strong responses across multiple domains including joints, skin, and nails... The IZAR program seeks to confirm the effectiveness of sonelokimab in treating PsA, with the ultimate goal of helping more patients reach their treatment goals across multiple domains.”
Philip J. Mease, MD, Director of Rheumatology Research at the Providence Swedish Medical Center, commented, “MoonLake’s Nanobody®, Sonelokimab is designed to precisely target challenging sites of inflammation by integrating Nanobody® innovation with the dual inhibition of IL-17F and IL-17A – a novel and promising clinical approach that may allow enhanced treatment of the multiple domains of PsA compared with conventional antibodies... The Phase 3 IZAR program is therefore an exciting opportunity to determine whether the novel design of sonelokimab can raise the current treatment bar in psoriatic arthritis.”
Kristian Reich, Founder and Chief Scientific Officer at MoonLake, added, “This is a major milestone for MoonLake, marking the second Phase 3 program independently initiated by the company this year... We are in full execution mode with our late-stage clinical development plans and look forward to reporting the primary endpoint in H1 2026.”
