Zenas BioPharma Reports Positive Long-Term Phase 3 Data for Obexelimab in IgG4-Related Disease
Zenas BioPharma, Inc. (ZBIO) presented new clinical findings for its lead drug candidate, obexelimab, at an international medical conference. Results from the Phase 3 INDIGO open-label extension demonstrated that the subcutaneous therapy provided sustained flare protection and significantly reduced cumulative steroid toxicity in patients with immunoglobulin G4-related disease. Shares of the biopharmaceutical company traded up nearly 3.9% following the presentation.
The long-term data revealed a 93% probability of patients remaining flare-free over 12 months based on committee-adjudicated criteria, with a median cumulative steroid rescue dose of 0 mg. A sub-study also evaluated vaccine responses, showing that patients who temporarily paused treatment for an average of 34.6 days successfully developed antibodies against influenza and COVID-19 without experiencing disease flares.
IgG4-related disease is a chronic inflammatory condition affecting roughly 25,000 diagnosed individuals in the United States. Obexelimab is designed to inhibit autoimmune B cells without depleting them. Looking ahead, investors will be monitoring upcoming clinical milestones, including topline results from the Phase 2 SunStone trial evaluating obexelimab in systemic lupus erythematosus, expected in the fourth quarter of 2026.
Key points
- Phase 3 INDIGO trial extension showed a 93% probability of patients remaining flare-free over 12 months on weekly obexelimab.
- Obexelimab significantly reduced cumulative glucocorticoid toxicity compared to placebo at week 52 with a GTI score difference of -11.4.
- Patients pausing treatment for an average of 34.6 days successfully developed vaccine antibodies against flu and COVID-19 without disease flares.
- Zenas BioPharma plans to report topline Phase 2 data for obexelimab in systemic lupus erythematosus in the fourth quarter of 2026.
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What were the Phase 3 INDIGO trial results for obexelimab?
The Phase 3 extension showed a 93% probability of patients remaining flare-free over 12 months, with reduced steroid toxicity and a median steroid rescue dose of 0 mg.
Does obexelimab allow patients to respond to vaccines?
Yes. In a sub-study, patients taking a planned break from obexelimab generated antibodies to influenza and COVID-19 vaccines without suffering disease flares.
When will Zenas BioPharma release its next clinical update?
Zenas BioPharma expects to report topline results from its Phase 2 SunStone trial of obexelimab in systemic lupus erythematosus in the fourth quarter of 2026.