Zenas BioPharma says obexelimab met primary endpoint in Phase 2 MoonStone trial

Zenas BioPharma (ZBIO) announced results from the Phase 2 MoonStone trial of obexelimab in Relapsing Multiple Sclerosis. Obexelimab met the primary endpoint, demonstrating a highly statistically significant 95% relative reduction in the cumulative number of new gadolinium-enhancing T1 hyperintense lesions over week 8 and week 12 compared with placebo. Near-complete suppression of new GdE T1 hyperintense lesions, which are markers of active inflammation, was observed with obexelimab by 8 weeks of treatment and was sustained through week 12. The adjusted mean number of new GdE T1 hyperintense lesions per scan in the obexelimab group was 0.01 compared to 0.23 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. 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. Zenas also expects to report topline results from the obexelimab Phase 3 INDIGO trial in IgG4-RD around year-end 2025 and topline results from the Phase 2 SunStone trial in Systemic Lupus Erythematosus, mid-2026, as well as the 24-week MoonStone trial results in the first quarter of 2026. In addition, orelabrutinib, a potentially best-in-class, highly-selective central nervous system-penetrant, oral, small molecule Bruton’s Tyrosine Kinase inhibitor, which Zenas recently in-licensed from InnoCare Pharma Limited, is now being studied in a global Phase 3 clinical trial in patients with Primary Progressive Multiple Sclerosis. Zenas also expects to initiate a global Phase 3 trial of orelabrutinib in patients with Secondary Progressive Multiple Sclerosis in the first quarter of 2026.