MoonLake’s IL‑17A/F‑targeting nanobody sonelokimab met the Phase III IZAR‑1 primary endpoint in biologic‑naïve patients with active psoriatic arthritis, with 42.1% achieving ACR50 at week 16. Secondary outcomes (ACR20, MDA, PASI90) and patient‑reported function and quality‑of‑life measures improved. IZAR‑1 participants will be followed to 52 weeks (data due H1 2027), while a head‑to‑head IZAR‑2 trial versus risankizumab is expected to complete enrollment in Q3 2026. The drug is also advancing in hidradenitis suppurativa, with an HS filing planned for H2 2026.
MoonLake’s Nanobody Sonelokimab Hits Phase III Target, Strengthening Psoriatic Arthritis Prospects
MoonLake’s nanobody boosts PsA indication hopes after Phase III success
MoonLake Immunotherapeutics reported positive topline results from the Phase III IZAR-1 study (NCT06641076), showing its IL‑17A/F‑targeting nanobody sonelokimab delivered clinically meaningful benefit in biologic‑naïve adults with active psoriatic arthritis (PsA).
Primary and key secondary outcomes: In the 60 mg arm at week 16, 42.1% of patients achieved an American College of Rheumatology 50 (ACR50) response, meeting the trial's primary endpoint. Key secondary outcomes were also favorable: 66.5% achieved ACR20, 41.2% reached Minimal Disease Activity (MDA), and 61% achieved Psoriasis Area and Severity Index 90 (PASI90).
Function and quality of life: Patients showed functional and quality‑of‑life gains from baseline, with a mean change in the Health Assessment Questionnaire Disability Index (HAQ‑DI) of -0.427 and an improvement of 6.54 points in the SF‑36 Physical Component Summary (PCS).
Participants in IZAR‑1 will remain on their assigned treatment or placebo through 52 weeks to assess durability; those longer‑term data are expected in H1 2027.
Ongoing and comparator studies: Sonelokimab is also being evaluated in IZAR‑2 (NCT06641089), a study that includes a standard‑of‑care arm and directly compares sonelokimab with AbbVie’s Skyrizi (risankizumab) in patients with active PsA who had an inadequate response to anti‑TNFα therapy. IZAR‑2 enrollment is expected to complete in Q3 2026.
Dr Jorge Santos da Silva, MoonLake’s founder and CEO, 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. These data are also encouraging as they are consistent with what was previously observed in other IL‑17A/F programmes."
Hidradenitis suppurativa (HS) programme: MoonLake is advancing sonelokimab in HS across VELA‑1 (NCT06411899), VELA‑2 (NCT06411379) and VELA‑TEEN (NCT06768671). In VELA‑1/2, 62% of treated patients achieved HiSCR75 at week 40 and 32% achieved HiSCR100; 25% achieved inflammatory remission as defined by the company (complete clearance of abscesses, nodules and draining tunnels). MoonLake plans to file for HS approval in H2 2026.
Market and competitive context: Despite the positive IZAR‑1 topline, MoonLake shares slipped roughly 5% on 10 August and continued to trade lower the following session. The company is listed on Nasdaq with a market capitalization around $1.41 billion. Independent expert commentary highlights competitive pressure in PsA—Dr Christopher Ritchlin noted sonelokimab may find it difficult to unseat UCB’s Bimzelx (bimekizumab) unless it demonstrates a clear advantage in efficacy, safety or pricing.
Outlook: The Phase III IZAR‑1 results support sonelokimab’s potential to improve musculoskeletal and skin outcomes as well as patient function and quality of life in PsA. Upcoming milestones to watch are IZAR‑1 52‑week durability data (H1 2027), IZAR‑2 enrollment completion (Q3 2026) and the planned HS regulatory filing (H2 2026).
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