Zenas BioPharma's Obexelimab Achieves 95% Reduction in Brain Lesions in Phase 2 Multiple Sclerosis Trial
核心洞察
Obexelimab met its primary endpoint with a 95% relative reduction in new gadolinium-enhancing T1 lesions compared to placebo in the Phase 2 MoonStone trial for relapsing multiple sclerosis (p=0.0009).
The bifunctional monoclonal antibody demonstrated near-complete suppression of inflammatory brain lesions by week 8, with sustained effects through week 12 of treatment.
The safety profile remained consistent with previous trials, and Zenas plans to report 24-week data in Q1 2026 to evaluate potential impact on disability progression.
Zenas BioPharma announced positive results from its Phase 2 MoonStone trial of obexelimab in relapsing multiple sclerosis (RMS), with the experimental therapy achieving a highly statistically significant 95% relative reduction in new brain lesions compared to placebo. The bifunctional monoclonal antibody met its primary endpoint, demonstrating profound suppression of gadolinium-enhancing T1 hyperintense lesions over weeks 8 and 12 (p=0.0009).
Trial Design and Patient Population
The randomized, double-blind, placebo-controlled Phase 2 MoonStone trial enrolled 116 patients with RMS. Participants were randomized 2:1 to receive either 250 mg of obexelimab or placebo via subcutaneous injection once weekly over a 12-week double-blinded treatment period. The trial follows a standard design using magnetic resonance imaging (MRI) endpoints that have historically been highly predictive of successful outcomes in large, randomized trials.
The primary endpoint measured the cumulative number of new gadolinium-enhancing T1 hyperintense lesions over weeks 8 and 12 as assessed by brain MRI. Secondary and exploratory endpoints include standardized assessments, imaging, and biomarkers to evaluate the impact on disease progression.
Efficacy Results
Near-complete suppression of new gadolinium-enhancing T1 hyperintense lesions, which are markers of active inflammation, was observed with obexelimab by 8 weeks of treatment and sustained through week 12. The adjusted mean number of new gadolinium-enhancing T1 hyperintense lesions per scan in the obexelimab group was 0.01 (95% CI: 0.00, 0.06) compared to 0.23 (95% CI: 0.11, 0.51) with placebo.
Additionally, over weeks 8 and 12 of treatment, obexelimab significantly reduced the cumulative number of new and/or enlarging T2 weighted hyperintense lesions compared to placebo, which represent the amount of disease burden or chronic lesion load.
Safety Profile
The safety profile of obexelimab was consistent with that observed in prior completed trials, including cases of infections and hypersensitivity, most commonly mild injection site reactions. Obexelimab has been evaluated in seven clinical trials in a total of 286 patients, including MoonStone, who received obexelimab either as an intravenous infusion or as a subcutaneous injection.
Mechanism of Action
Obexelimab is a bifunctional monoclonal antibody designed to bind both CD19 (搜索) and FcγRIIb (搜索), which are broadly present across B cell lineage, to inhibit the activity of cells that are implicated in many autoimmune diseases without depleting them. This unique mechanism of action and self-administered, subcutaneous injection regimen may broadly and effectively address the pathogenic role of the B cell lineage in chronic autoimmune disease.
Clinical Context and Unmet Need
Multiple sclerosis is a chronic, autoimmune-mediated disorder of the central nervous system affecting approximately 2.9 million people worldwide according to the Multiple Sclerosis International Federation. The disease disproportionately affects females, with highest prevalence observed in North America, Europe and Australia.
RMS is characterized by distinct episodes of new or worsening neurological symptoms (relapses), followed by partial or complete remission. Approximately 85% of patients are initially diagnosed with RMS. MS onset typically occurs between 20 and 40 years of age, making MS the leading cause of non-traumatic neurological disability in young adults.
Development Timeline and Pipeline
"With these highly statistically significant data, we look forward to reporting 24-week data in the first quarter of 2026, which will include additional secondary and exploratory endpoints that may inform obexelimab's potential impact on disability progression and help us determine next steps for future development of obexelimab in relapsing MS," said Lisa von Moltke, M.D., Head of Research and Development and Chief Medical Officer of Zenas.
Zenas expects to report topline results from the obexelimab Phase 3 INDIGO trial in IgG4-Related Disease around year-end 2025 and topline results from the Phase 2 SunStone trial in Systemic Lupus Erythematosus mid-2026. The company is also advancing orelabrutinib, a potentially best-in-class, highly-selective central nervous system-penetrant, oral, small molecule Bruton's Tyrosine Kinase (BTK (搜索)) inhibitor, in a global Phase 3 clinical trial in patients with Primary Progressive Multiple Sclerosis.
Company Perspective
"These profound MoonStone trial results, including the near elimination of new GdE T1 lesions, provide strong evidence of the deep and sustained inhibitory mechanism of obexelimab and further validate the potential for obexelimab to become a meaningful therapy across multiple autoimmune diseases," said Lonnie Moulder, Founder and Chief Executive Officer of Zenas.