Moonlake Immunotherapeutics (MLTX) Securities Class Action Lawsuit Filed [October 28, 2025]

Introduction to Moonlake Immunotherapeutics (MLTX) Securities Class Action Lawsuit

A securities fraud class action has been filed against Moonlake Immunotherapeutics (NASDAQ: MLTX) covering March 10, 2024 through September 29, 2025. Investors allege the company and its leadership misrepresented that sonelokimab's "Nanobody" design delivered superior clinical benefits and tissue penetration over monoclonal antibodies like BIMZELX, despite sharing the same IL-17A/IL-17F targets. On September 28, 2025, Moonlake announced Phase 3 VELA results that failed to show competitive efficacy versus BIMZELX, contradicting the touted advantages. The next trading day, Moonlake's stock price collapsed. Investors allege significant losses followed these revelations.

Moonlake Immunotherapeutics (MLTX) Securities Lawsuit Case Details

Case Name: Peters v. Moonlake Immunotherapeutics, et al. 
Case No.: 1:25-cv-08612 
Jurisdiction: U.S. District Court, Southern District of New York
Filed on: October 17, 2025

Moonlake Immunotherapeutics (MLTX) Company Profile

Moonlake is a Swiss clinical-stage biotechnology company focused on IL-17–driven inflammatory diseases in dermatology and rheumatology. Its sole drug candidate, sonelokimab (SLK), is developed for hidradenitis suppurativa and other inflammatory conditions, and the company trades on NASDAQ under ticker MLTX.

Moonlake Immunotherapeutics (MLTX) Securities Lawsuit Class Period

March 10, 2024–September 29, 2025, inclusive.

All persons and entities who purchased or otherwise acquired MLTX common stock during the Class Period, excluding Defendants, directors and officers of the Company, as well as their families and affiliates, may be eligible to join the Moonlake Immunotherapeutics (MLTX) class action lawsuit.

Allegations in the Moonlake Immunotherapeutics (MLTX) Securities Class Action Lawsuit

According to the complaint, investors are suing Moonlake Immunotherapeutics, its Chief Executive Officer Jorge Santos da Silva, and its Chief Financial Officer Matthias Bodenstedt over statements made as the company advanced sonelokimab. The story began in May 2022, when Moonlake started its Phase 2b MIRA trial of sonelokimab for moderate-to-severe hidradenitis suppurativa. By June 2023, the company reported positive top-line results meeting its HiSCR75 endpoint, and follow-up data in October 2023 showed further improvement with continued treatment. Early 2024 brought endorsements from both the FDA and EMA for the proposed Phase 3 program, setting the stage for broader claims about the supposed advantages of the company's Nanobody technology.

On March 10, 2024, during an R&D Day, CEO Jorge Santos da Silva told investors that sonelokimab "combine[s] two different targets in IL-17A and IL-17F" and that its third domain targets sites of inflammation—"all things that a monoclonal antibody cannot do." That same day, he said SLK "is much smaller than a monoclonal antibody, and that allows us to penetrate tissues better." As the program advanced, Moonlake began patient screening for its Phase 3 VELA-1 and VELA-2 trials in May 2024.

Defendants repeatedly promoted SLK's purported structural advantages as translating into superior clinical efficacy. On November 7, 2024, in a press release, da Silva stated that inhibiting all IL-17A and IL-17F dimers, together with Nanobody "molecular advantages," "translate into higher clinical responses for patients" and provide "ample opportunity for differentiation of sonelokimab versus all competitors." On March 28, 2025, he told Investment Reports that "nanobodies can penetrate tissues more effectively" and "offer a more convenient and effective treatment." On April 29, 2025, during a Capital Markets Update, he called nanobodies a "next-generation biologic" that is "excellent for penetration" with "devices that monoclonal antibodies don't have." On July 8, 2025, at Guggenheim's Biopharma Spotlight Series, Yatin Suneja stated that sonelokimab "is not simply a 'me-too' analog of UCB's BIMZELX" and provides "distinct drug hallmarks" that enhance efficacy and convenience.

Plaintiffs allege that while these statements painted a picture of superiority, SLK and BIMZELX share the same molecular targets, and SLK's distinct Nanobody structure would not confer a superior clinical benefit over BIMZELX's monoclonal structure. They further allege that claims about increased tissue penetration would not translate into clinical efficacy and, based on these facts, Defendants lacked a reasonable basis for positive statements about SLK's purported superiority. The narrative culminated on September 28, 2025, when Moonlake announced week-16 results from its Phase 3 VELA program.

The Truth Emerges

On September 28, 2025, Moonlake issued a press release and hosted a webcast detailing week-16 results from the Phase 3 VELA program in hidradenitis suppurativa. The disclosure stated that SLK failed to demonstrate competitive efficacy relative to BIMZELX. In VELA-1, SLK beat placebo in HS disease response by 17 percentage points, a statistically significant difference, while in VELA-2 a high placebo response prevented statistical significance; to be considered competitive with BIMZELX, SLK had to exceed placebo by at least 23 percentage points.

These results undercut the prior narrative that Nanobody features would yield higher clinical responses and meaningful differentiation versus monoclonal antibodies. The corrective disclosure directly contradicted earlier statements touting superior tissue penetration and efficacy, exposing the gap between promotion and performance.

Market Reaction

The market responded accordingly. On September 29, 2025, the first trading day after the disclosure, Moonlake's stock price fell $55.75 per share, or 89.9%, to close at $6.24. The sharp decline reflected the market's reassessment of SLK's competitive profile following the VELA results.

Next Steps

• Submissions for lead plaintiff are due December 15, 2025.
• The Court will issue its order for lead plaintiff and counsel in the weeks after submissions are due.
• The Court will then consider motion for class certification.
• The Court will later consider a Motion to Dismiss.

To learn if you are eligible for recovery under the MLTX securities class action lawsuit, visit the case submission page here.
Disclaimer: This shareholder alert is for informational purposes only and does not constitute legal advice. Consult a qualified attorney for personalized guidance. No specific outcomes are guaranteed.