MoonLake’s nanobody boosts all clinical endpoints in phase 3 psoriatic arthritis trial

Biotech MoonLake’s nanobody boosts all clinical endpoints in phase 3 psoriatic arthritis trial By Marissa Russo Aug 10, 2026 11:00am MoonLake Immunotherapeutics psoriatic arthritis IL-17 nanobodies MoonLake Immunotherapeutics announced positive phase 3 data of patients with psoriatic arthritis treated with its lead nanobody candidate, sonelokimab. At week 16, 42.1% of patients achieved American College of Rheumatology 50 (ACR50), or at least a 50% improvement in rheumatoid arthritis symptoms such as joint pain and swelling. All secondary clinical endpoints were also met, according to today’s release.

These included 66.5% of patients achieving ACR20, 41.2% achieving minimal disease activity (MDA), and in patients with concomitant skin involvement, 61% achieving psoriasis area and severity index 90 (PASI90) at week 16. Patients enrolled in the trial, coded Izar-1, were new to any biologic treatment. “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,” founder and CEO of MoonLake, Jorge Santos de Silva Ph.D., said in the release. The trial does not include an active comparator arm but uses placebo as the control arm. Comparative analyses versus placebo, plus detailed treatment arm data, remain blinded until completion of the trial, which is expected in the first half of 2027, according to MoonLake.

The Izar-1 trial in biologic-naïve patients is part of a pair of global randomized double-blind trials evaluating subcutaneously administered sonelokimab in adults with active psoriatic arthritis. The second trial, Izar-2, is being conducted in patients who have not seen improvement in symptoms after taking TNF inhibitors such as AbbVie's Humira, and it will directly compare sonelokimab with AbbVie’s Skyrizi. Related MoonLake's phase 2 arthritis win kicks off pivotal year for IL-17 nanobody MoonLake was founded in 2021 and focuses on developing nanobodies to treat inflammatory diseases with high unmet needs including hidradenitis suppurativa, psoriatic arthritis, axial spondyloarthritis and palmoplantar pustulosis.

As the Swiss biotech's lead asset, sonelokimab recently showed positive phase 2 data in axial spondyloarthritis and is also currently being tested in multiple phase 3 trials for hidradenitis suppurativa. Psoriatic arthritis is a chronic inflammatory disease that causes joint pain, swelling, and stiffness. The disease affects 2.4 million people in the U.S., while 1 in 3 people living with psoriasis also has psoriatic arthritis.

MoonLake is looking to enter an already saturated market for psoriasis and psoriatic arthritis drugs. Besides AbbVie’s Skyrizi, Humira and Rinvoq, existing and future contenders include Johnson & Johnson’s Tremfya, Amgen’s Otezla, Bristol Myers Squibb’s Sotyktu and Takeda’s up-and-coming zasocitinib. MoonLake’s sonelokimab, licensed from Germany’s Merck KGaA in 2021, is unique because the drug is a nanobody, a modality that's different from any FDA-approved therapies.

Nanobodies are smaller than antibodies and can be designed to target multiple and different binding sites. Sonelokimab is designed to “more directly target sites of inflammation and penetrate difficult-to-reach inflamed tissues,” according to MoonLake's website. It binds to interleukin 17F and 17A, central drivers of inflammatory disease, as well as albumin, further enriching the drug at sites of inflammation.

MoonLake Immunotherapeutics psoriatic arthritis IL-17 nanobodies clinical trial data Biotech