Topline IZAR-1 results show 42.1% of biologic-naïve patients with psoriatic arthritis achieved ACR50 at Week 16, while 61% with skin involvement achieved PASI90.
The phase 3 IZAR-1 trial (NCT06641076) investigating sonelokimab in adults with active psoriatic arthritis (PsA) has met its primary endpoint, according to topline results announced by MoonLake Immunotherapeutics.¹
Week 16 results show efficacy across key PsA domains
IZAR-1 is a global, randomized, double-blind trial evaluating sonelokimab in biologic-naïve adults with active PsA. The primary endpoint was the proportion of patients achieving at least a 50% improvement in American College of Rheumatology response criteria (ACR50) at Week 16.
At Week 16, 42.1% of patients receiving sonelokimab 60 mg with induction achieved an ACR50 response. Key secondary endpoints covering musculoskeletal, skin and functional domains were also met for the sonelokimab 60 mg arm. At Week 16, 66.5% of patients achieved an ACR20 response and 41.2% achieved minimal disease activity (MDA). Among patients with concomitant skin involvement, 61% achieved PASI90.
Patient-reported and physical function outcomes also improved, including a mean change of −0.427 in Health Assessment Questionnaire-Disability Index (HAQ-DI) score and a 6.54-point improvement in the Short Form-36 (SF-36) physical component summary (PCS) score.
The IZAR-1 results follow positive phase 2 ARGO data, in which ACR50 and MDA responses were observed in approximately 60% of patients treated with sonelokimab at Week 24.¹
Under 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 programme.¹ MoonLake expects IZAR-1 to be completed in the first half of 2027.
Safety signals consistent with previous sonelokimab studies
The company reported that blinded safety findings were consistent with previous studies of sonelokimab, with no new safety signals identified and a low dropout rate through Week 16.¹
Following the announcement, Jorge Santos da Silva, Founder and Chief Executive Officer of MoonLake Immunotherapeutics, described the IZAR-1 results as “an important milestone for MoonLake and, more importantly, for patients living with psoriatic arthritis.”¹
He added: “We are particularly encouraged by the strong efficacy observed across multiple clinically relevant endpoints simultaneously, which has been our focus. These data are also encouraging as they are consistent with what was previously observed in other IL-17A/F programs. This reinforces our conviction that sonelokimab has the potential to become a leading treatment option in PsA and further validate the broad potential of our Nanobody® platform in inflammatory disease.”
Sonelokimab and and next steps in the IZAR programme
Sonelokimab is an investigational trivalent nanobody designed to bind with high affinity to interleukin (IL)-17A and IL-17F, inhibiting IL-17A/A, IL-17A/F and IL-17F/F dimers.¹
The second registrational study in the IZAR programme, IZAR-2, is evaluating sonelokimab in patients with an inadequate response to tumour necrosis factor inhibitors and includes a risankizumab active reference arm. Enrolment is expected to be completed in the third quarter of 2026.
The therapy is also being investigated in plaque psoriasis and hidradenitis suppurativa.
References
- MoonLake Immunotherapeutics. (August 10, 2026). MoonLake announces positive topline results from the phase 3 IZAR-1 trial of sonelokimab in psoriatic arthritis demonstrating significant improvements across all clinical endpoints [Press release]. 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
Disclosure: This article was created by the touchDERMATOLOGY team utilizing AI as an editorial tool (Claude [Large language model]. https://claude.ai.) The content was developed and edited by human editors. No funding was received in the publication of this article.
Cite: Sonelokimab meets primary endpoint in phase 3 IZAR-1 trial for psoriatic arthritis. touchDERMATOLOGY. August 19, 2026
Editor: Gina Furnival
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