MoonLake Immunotherapeutics has reported encouraging results for its IL-17 inhibitor sonelokimab in adolescent patients with hidradenitis suppurativa (HS), potentially offering a path forward after disappointing adult trial outcomes earlier this year.
Teen Trial Shows Improved Response Rates
The Phase III VELA-TEEN study demonstrated that 46% of adolescent HS patients achieved HiSCR75 (Hidradenitis Suppurativa Clinical Response 75) at 16 weeks. HiSCR75 defines a response as at least 75% reduction in abscess and inflammatory nodule count, with no increase from baseline in abscess or draining tunnel count.
This response rate represents a notable improvement over the drug's performance in adult populations, where the VELA-1 and VELA-2 trials showed HiSCR75 rates of 34.8% and 35.9% respectively at 16 weeks, compared to placebo rates of 17.5% and 25.6%.
Adult Trial Challenges and Market Context
The adult trials fell short of expectations, particularly when compared to UCB's Bimzelx (bimekizumab-bkz), which achieved HiSCR75 in 64% of patients after 96 weeks in its Phase III programme. The VELA programme was impacted by higher-than-expected placebo response rates, particularly in the VELA-2 trial.
GlobalData neurology and immunology director Erela Dana noted that "the expectation was that sonelokimab would outperform Bimzelx, which showed HiSCR75 in ~60% of patients in Phase III studies." The disappointing adult results led to an 88.77% stock drop, from $61.99 to $6.96, though shares have since partially recovered to $10.59.
Regulatory Path Forward
Despite the mixed results, MoonLake is pursuing regulatory approval. The company has scheduled a Type B meeting with the FDA for December 15, 2025, to discuss a potential biologics license application (BLA) submission. The safety profile of sonelokimab remained consistent with previous studies, with no new safety signals observed.
Importantly, Bimzelx is not currently FDA-approved for adolescent patients, potentially creating a market opportunity for sonelokimab in this population.
Expansion into Palmoplantar Pustulosis
Beyond HS, sonelokimab demonstrated positive results in the Phase II LEDA study for palmoplantar pustulosis (PPP). The drug achieved a statistically significant 64% reduction in palmoplantar pustular psoriasis area and severity index (PPPASI) scores at week 16, with 39% of patients achieving 75% or greater PPPASI score reduction.
MoonLake noted these data suggest sonelokimab could "provide clinically meaningful improvements" in PPP, a condition where no therapy has yet gained approval in the US and EU. The company plans to advance to Phase III PPP trials beginning in Q3 2026.
Market Landscape and Competition
The HS market is forecast to grow significantly, from $1.84 billion in 2024 to $7.83 billion in 2034, according to GlobalData. Analysts predict Bimzelx will become a blockbuster seller in 2025, generating $1.5 billion for UCB.
In the PPP space, sonelokimab will face competition from established players including Johnson & Johnson's Tremfya (guselkumab) and AbbVie's Rinvoq (upadacitinib), which are forecast to generate $9.1 billion and $15 billion respectively by 2031 across all their approved indications.
