MoonLake's IL-17 Drug Faces Setback in Phase 3 HS Trial, Stock Plummets

MoonLake Immunotherapeutics experienced a significant setback as its investigational interleukin-17 (IL-17) inhibitor, sonelokimab, failed to meet the primary endpoint in one of two phase 3 studies for hidradenitis suppurativa (HS). The news caused the company's stock to crash by 87% in premarket trading on Monday.

Mixed Results from VELA-1 and VELA-2 Studies

The biotechnology company conducted two identical phase 3 studies, VELA-1 and VELA-2, evaluating a single 120-mg dose of sonelokimab in 838 patients with moderate to severe HS. The primary endpoint was the proportion of patients achieving at least a 75% reduction in abscess and inflammatory nodule count compared to placebo.

While the proportion of patients reaching the primary endpoint was similar in both studies (34.8% in VELA-1 and 35.9% in VELA-2), the placebo response rates differed significantly. VELA-1 showed a placebo response of 17.5%, but VELA-2 had a higher-than-expected rate of 25.6%, causing the study to miss its primary endpoint.

Despite the setback, MoonLake reported that both studies met key secondary endpoints related to lesion count and patient-reported outcomes. The company also noted a favorable safety profile consistent with previous studies, with no new safety signals observed.

Company Response and Future Plans

Dr. Kristian Reich, Chief Scientific Officer at MoonLake, expressed disappointment with the higher placebo response in VELA-2 but remained optimistic about sonelokimab's potential. "We are encouraged by the results of VELA-1, which follow the expected performance of sonelokimab in all the important metrics for patients and treating physicians," Reich stated.

MoonLake plans to discuss the unexpected placebo data with regulators while continuing to pursue approval for the drug. The company has several ongoing studies, including:

• 52-week data from VELA-1 and VELA-2, expected in Q2 2026
• A phase 2 study in palmoplantar pustulosis, with results due later this year
• A phase 2 study in axial spondyloarthritis and phase 3 studies in adolescent HS and psoriatic arthritis, all scheduled to read out next year

Market Impact and Industry Implications

The mixed phase 3 results have cast doubt on sonelokimab's future, potentially affecting MoonLake's position in the competitive IL-17 inhibitor market. The setback may also impact ongoing discussions with potential acquirers, as reports from June suggested that Merck & Co. had previously submitted a non-binding offer valuing MoonLake at over $3 billion.

Sonelokimab, originally developed by Ablynx (now part of Sanofi), was licensed to MoonLake from Germany's Merck KGaA in 2021. The drug's performance in these trials could have far-reaching implications for MoonLake's pipeline and strategic partnerships within the pharmaceutical industry.