Obexelimab - (MoonStone)

Feb. 9, 2026: Zenas BioPharma (NASDAQ: ZBIO) reported late-breaking ACTRIMS Forum 2026 Phase 2 MoonStone data for obexelimab in relapsing multiple sclerosis. Obexelimab met the primary endpoint, reducing cumulative new gadolinium-enhancing T1 lesions by 95% versus placebo over weeks 8 and 12 (p=0.0009). Adjusted mean new lesions per scan were 0.01 (95% CI 0.00-0.06) with obexelimab vs 0.23 (95% CI 0.11-0.51) with placebo; 2 new lesions were seen in treated patients vs 19 on placebo, and 97.2% of obexelimab-treated patients were lesion-free over this period. Safety was consistent with prior trials, with infections and hypersensitivity including mostly mild injection-site reactions; no new safety signals were reported.

Separately, 24-week MoonStone data showed durability: unadjusted mean total Gd-enhancing T1 lesions fell from 0.87 at baseline to 0.08 at week 12 and 0.04 at week 24, with a 40% reduction in serum neurofilament light by week 24 (15.28 pg/mL baseline, 12.7 at week 12, 9.2 at week 24). New/enlarging T2 lesions were lower and EDSS scores were stable.

Upcoming catalysts mentioned: obexelimab BLA submission to FDA for IgG4-related disease in Q2 2026, EMA MAA in 2H 2026, topline Phase 2 SunStone SLE data in Q4 2026, and initiation this quarter of a global Phase 3 orelabrutinib trial in non-active SPMS; orelabrutinib is already in Phase 3 for PPMS.