WALTHAM, Mass. — Zenas BioPharma, Inc. (“Zenas,” “Zenas BioPharma” or the “Company”) (Nasdaq: ZBIO), a clinical-stage global biopharmaceutical company committed to being a leader in the development and commercialization of transformative therapies for patients living with autoimmune diseases, today announced that safety and efficacy outcomes from the Phase 3 INDIGO trial evaluating obexelimab in Immunoglobulin G4-Related Disease (IgG4-RD) will be presented in an oral presentation at the upcoming European Alliance of Associations for Rheumatology (EULAR) 2026 Congress, held from June 3-6, 2026, in London, England.
INDIGO, the largest randomized, double-blind, placebo-controlled study conducted in IgG4-RD, met the primary endpoint demonstrating a highly statistically significant and clinically meaningful 56% reduction in the risk of IgG4-RD flare compared to placebo (HR 0.443; 95% CI 0.277–0.711; p=0.0005) during the 52-week randomized placebo-controlled period. Obexelimab also met and demonstrated highly statistically significant activity compared to placebo on all four key secondary endpoints: time to first investigator-determined flare requiring rescue therapy (p=0.0001), number of investigator- and AC-determined flares requiring rescue therapy (p=0.0008), proportion of patients achieving complete remission (p=0.0049), and cumulative glucocorticoid rescue therapy use (p=0.0042). Obexelimab was well tolerated with no new safety signals observed. Treatment-emergent adverse events (TEAEs) occurred in 97.9% vs 95.9% of participants (obexelimab vs placebo). Incidence of Grade ≥3 TEAEs was less with obexelimab (11.3% vs 23.7%), and the incidence of serious adverse events was 10.3% vs 18.6%. Infections occurred in 53.6% vs 62.9% of participants. Injection-site reactions were reported in 3.5% vs 2.3% of total patient doses. Hypersensitivity occurred in 16.5% vs 11.3% of participants. There were no deaths in the obexelimab group and one death (1.0%) in the placebo group.
Details of EULAR Presentation:
- Title: Obexelimab, a B Cell Inhibitor, in IgG4-Related Disease: Results From the Phase 3 INDIGO Trial
- Presenting Author: Emanuel Della Torre, M.D., Ph.D., Associate Professor of Rheumatology, Vita-Salute San Raffaele University, Milan, Italy
- Session: New Perspectives in IgG4-Associated Diseases
- Session Date & Time: Thursday, June 4, 2026, at 2:45 PM GMT
- Abstract Number: OP018
- Location: Excel London, Room N1
About Obexelimab
Obexelimab is a bifunctional monoclonal antibody designed to bind both CD19 and FcgRIIb, which are broadly present across B cell lineage, to inhibit the activity of cells that are implicated in many autoimmune diseases without depleting them. This unique inhibitory mechanism of action and self-administered, subcutaneous injection regimen may broadly and effectively address the pathogenic role of the B cell lineage in chronic autoimmune disease.
Obexelimab has been evaluated in eight clinical trials in a total of 383 subjects, including INDIGO. Obexelimab was well tolerated and demonstrated clinical activity across these clinical trials. The registrational Phase 3 INDIGO trial for Immunoglobulin G4-Related Disease met its primary endpoint and all four key secondary endpoints with high statistical significance. The trial continues to evaluate patients in the 3-year open label extension period which will further build upon the largest body of clinical data reported for IgG4-RD patients to date. Enrollment in a randomized Phase 2 trial for Systemic Lupus Erythematosus is completed and Zenas expects to report topline results, including biomarker data from this trial in the fourth quarter of 2026.
About Zenas BioPharma
Zenas is a clinical-stage global biopharmaceutical company committed to becoming a leader in the development and commercialization of transformative therapies for patients living with autoimmune diseases. Zenas’ core business strategy combines our experienced leadership team with a disciplined product candidate acquisition approach to identify, acquire and develop product candidates globally that we believe can provide superior clinical benefits to patients living with autoimmune diseases. Zenas is advancing two late-stage, potential franchise molecules, obexelimab and orelabrutinib. Obexelimab, Zenas’ lead product candidate, is a bifunctional monoclonal antibody designed to bind both CD19 and FcgRIIb, which are broadly present across B cell lineage, to inhibit the activity of cells that are implicated in many autoimmune diseases without depleting them. Zenas believes that obexelimab’s unique mechanism of action and self-administered, subcutaneous injection regimen may broadly and effectively address the pathogenic role of B cell lineage in chronic autoimmune disease. Orelabrutinib is a potentially best-in-class, highly selective CNS-penetrant, oral, small molecule BTK inhibitor. Orelabrutinib’s mechanism of action targets pathogenic B cells not only in the periphery but also within the CNS. Additionally, it directly modulates macrophages and microglial cells in the CNS, with the potential to address compartmentalized inflammation and disease progression in MS. Zenas’ earlier stage programs include ZB021, a novel, potentially best-in-class, oral small molecule IL-17AA/AF inhibitor, ZB022, a preclinical, potentially best-in-class, oral, brain-penetrant, TYK2 inhibitor, and ZB014, a preclinical, half-life extended anti-CD19 and FcgRIIb monoclonal antibody. For more information about Zenas BioPharma, please visit https://zenasbio.com/ and follow us on LinkedIn.
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