MoonLake reports phase 3 win for psoriatic arthritis drug

MoonLake Immunotherapeutics said sonelokimab met the primary endpoint in IZAR-1, a phase 3 study in biologic-naive adults with active psoriatic arthritis. At week 16, 42.1 percent of patients achieved at least a 50 percent improvement under the American College of Rheumatology response measure.

The company also reported that all secondary clinical endpoints were met. Those included a 66.5 percent ACR20 response, minimal disease activity in 41.2 percent of patients and a 90 percent improvement in psoriasis severity for 61 percent of patients who had skin involvement.

Important comparative data remain blinded

IZAR-1 is randomized and placebo controlled, but MoonLake has not disclosed the results by treatment arm. Comparative data and detailed safety findings are expected when the study is completed in the first half of 2027.

Without the placebo results, the topline percentages cannot establish the size of the treatment effect. They show that the study met its prespecified statistical tests, according to the company, but do not yet allow a full comparison with existing medicines.

A second phase 3 trial tests a harder population

MoonLake is also running IZAR-2 in patients who did not respond adequately to tumor necrosis factor inhibitors. That trial includes AbbVie's Skyrizi as an active reference arm.

Results from IZAR-2 will help determine whether sonelokimab can compete in patients who have already tried biologic treatment. The psoriatic arthritis market includes established medicines from AbbVie, Johnson & Johnson, Amgen and Bristol Myers Squibb.

Sonelokimab uses a smaller antibody format

Sonelokimab is a nanobody designed to inhibit IL-17A and IL-17F while binding albumin. MoonLake argues that the smaller format can reach inflamed tissue efficiently, although that proposed advantage must be established through clinical comparisons.

The drug is also being developed for hidradenitis suppurativa and other inflammatory diseases. Regulatory decisions will depend on the complete efficacy, safety and manufacturing package rather than the topline response rates alone.