Zenas Biopharma reported that obexelimab met the primary endpoint in a Phase 3 trial for IgG4‑related disease, delivering a statistically significant reduction in flares versus placebo. The topline effect—a 56% reduction in flare risk over 52 weeks—fell short of the efficacy seen with Amgen’s Uplizna, prompting investor concern and rapid share price declines. Management said a BLA submission is planned for the second quarter, positioning obexelimab as a non‑depleting B‑cell inhibitor that could appeal to older patients concerned about depletion during vaccination season. Investors focused on cross‑trial comparisons: Amgen’s drug showed an 87% risk reduction in a pivotal study, and markets reacted by halving Zenas’ stock despite the positive primary result. Zenas emphasized differentiated safety and dosing characteristics as potential commercial levers.