Zenas BioPharma's Obexelimab Phase 3 Cuts Flare Risk 56% and Slashes Steroid Use
ZBIO•Zenas BioPharma's Phase 3 INDIGO trial of obexelimab in IgG4-RD achieved a 56% reduction in flare risk (HR 0.44; p=0.0005) and a 65% decrease in cumulative glucocorticoid use (329.5 mg vs 929.8 mg; p=0.0042). The safety profile matched placebo with lower rates of serious adverse events and infections.
1. INDIGO Phase 3 Results
The INDIGO trial randomized 194 IgG4-RD patients to weekly subcutaneous obexelimab or placebo for 52 weeks. Obexelimab reduced flare risk by 56% (HR 0.44; 95% CI 0.277–0.711; p=0.0005) with 73.2% of treated patients remaining flare-free versus 45.4% on placebo.
2. Steroid Sparing Effects
At week 52, mean cumulative glucocorticoid rescue use was 329.5 mg in the obexelimab arm versus 929.8 mg in placebo, a 65% reduction (p=0.0042). Fewer obexelimab patients exceeded predefined Glucocorticoid Toxicity Index thresholds (42.2% vs 61.2% for ≥20-point increase; p=0.0135).
3. Safety and Tolerability
Treatment-emergent adverse events occurred in 97.9% of obexelimab patients versus 95.9% for placebo, with fewer Grade ≥3 TEAEs (11.3% vs 23.7%) and serious adverse events (10.3% vs 18.6%), and a lower infection rate (53.6% vs 62.9%).
4. BLA Submission and Next Steps
A Biologics License Application for obexelimab in IgG4-RD was submitted to the FDA in May 2026. Zenas BioPharma expects topline results from its Phase 2 SLE SunStone trial later this year and will advance its half-life-extended antibody ZB014 toward clinical development.
