WALTHAM, Mass. — January 5, 2026 — Leads & Copy — Zenas BioPharma, Inc. (Nasdaq: ZBIO) announced positive results from the Phase 3 INDIGO trial of obexelimab in Immunoglobulin G4-Related Disease (IgG4-RD).
The trial met its primary endpoint, with obexelimab demonstrating a clinically meaningful and statistically significant 56% reduction in the risk of IgG4-RD flare compared to placebo (Hazard Ratio 0.44, p=0.0005) during the 52-week randomized placebo-controlled period.
Obexelimab also met and demonstrated statistically significant activity compared to placebo on all four key secondary endpoints, which were reduction in investigator assessed IgG4-RD flare, the number of flares requiring rescue therapy, the proportion of patients achieving complete remission and the cumulative use of IgG4-RD rescue therapy.
Rates of infections, including Grade 3, were lower in the obexelimab arm compared to placebo, and the incidence of injection site reactions was similar across both study arms.
Zenas anticipates submitting a Biologics License Application (BLA) to the FDA in the second quarter of 2026 and a Marketing Authorization Application (MAA) to the EMA in the second half of 2026.
The company expects that full data from the INDIGO trial will be presented at a future medical meeting. Zenas also expects to report topline results, including a biomarker analysis, of the obexelimab Phase 2 SunStone trial in SLE in the fourth quarter of 2026. In addition, orelabrutinib, a potentially best-in-class, highly selective central nervous system (CNS)-penetrant, oral, small molecule Bruton’s Tyrosine Kinase (BTK) inhibitor, is being studied in a global Phase 3 clinical trial in patients with Primary Progressive Multiple Sclerosis (PPMS). A global Phase 3 trial of orelabrutinib in patients with non-active Secondary Progressive Multiple Sclerosis (naSPMS) is expected to initiate in the first quarter of 2026. Subject to Investigational New Drug (IND) clearance, Zenas expects to initiate Phase 1 clinical development for ZB021, a potentially best-in-class oral IL-17AA/AF inhibitor, in 2026. Pending Phase 1 data, Zenas expects to advance development of ZB021 for rheumatic and/or dermatologic diseases. In addition, subject to IND clearance, Zenas expects to initiate Phase 1 clinical development for ZB022, a potentially best-in-class brain penetrant TYK2 inhibitor, in 2026. Pending Phase 1 data, Zenas expects to advance development of ZB022 for neurologic diseases.
According to Lonnie Moulder, Founder and Chief Executive Officer of Zenas, obexelimab may have an important role as a first line therapy in the long-term management of IgG4-RD. Moulder added that IgG4-RD represents a significant commercial opportunity for obexelimab and Zenas, and today’s data support obexelimab as a potential franchise molecule for rheumatic diseases.
John Stone, M.D., M.P.H., Professor of Medicine at Harvard Medical School and the Edward A. Fox Chair in Medicine at Massachusetts General Hospital, said the INDIGO study results suggest that obexelimab, with its intriguing mechanism of action – emphasizing B cell inhibition rather than B cell depletion – and self-administration by patients, may be an important new therapy for people living with IgG4-RD.
Lisa von Moltke, M.D., Head of Research and Development and Chief Medical Officer of Zenas, said these INDIGO trial results build upon the highly positive results observed in the company’s Phase 2 MoonStone trial in Relapsing Multiple Sclerosis and further validate obexelimab’s mechanism of action, optimized subcutaneous dosing and its potential to address the unmet medical needs of patients living with autoimmune diseases.
Immunoglobulin G4-Related Disease (IgG4-RD) is a chronic fibro-inflammatory disease that can affect virtually all organ systems.
Zenas will host a conference call and webcast today, January 5, 2026, at 8:00 a.m. ET to discuss the positive results from the Phase 3 INDIGO trial of obexelimab in IgG4-RD.
Investor and Media Contact:
Argot Partners
Zenas@argotpartners.com
Source: Zenas BioPharma
