Zenas BioPharma (NASDAQ: ZBIO) has announced the completion of targeted enrollment in its Phase 3 INDIGO trial, evaluating obexelimab for the treatment of Immunoglobulin G4-Related Disease (IgG4-RD). This global, double-blind, placebo-controlled study, involving approximately 190 patients across 100 sites in 20 countries, represents the largest clinical trial ever conducted for this rare immune-mediated condition. Topline results are anticipated by the end of 2025.
Significance of the INDIGO Trial
The INDIGO trial (NCT05662241) is designed to assess the safety and efficacy of obexelimab in patients with active IgG4-RD. Participants were randomized 1:1 to receive either 250 mg of obexelimab or a placebo via subcutaneous injection every seven days for 52 weeks. Following this period, eligible patients can continue into an open-label extension where all receive obexelimab.
The primary efficacy endpoint is the time to first IgG4-RD flare, determined by the investigator and an adjudication committee. Secondary endpoints include the annualized flare rate, the proportion of patients achieving complete remission, and the use and quantity of rescue medication.
Obexelimab: A Novel Approach
Obexelimab is a bifunctional monoclonal antibody that binds to both CD19 and FcγRIIb, present across the B cell lineage. This mechanism aims to inhibit the activity of B cells implicated in autoimmune diseases without depleting them. The self-administered, subcutaneous injection regimen offers a potentially effective way to address the pathogenic role of B cells in chronic autoimmune diseases.
Obexelimab has been evaluated in five completed clinical trials involving 198 patients, demonstrating clinical activity and tolerability. Zenas BioPharma is currently conducting multiple Phase 2 and Phase 3 trials of obexelimab in autoimmune diseases, including Multiple Sclerosis, Systemic Lupus Erythematosus, and warm Autoimmune Hemolytic Anemia.
IgG4-RD: An Unmet Medical Need
IgG4-RD is a chronic fibro-inflammatory disease that can affect multiple organ systems, including the pancreas, biliary tract, salivary and lacrimal glands, lungs, and kidneys. It is estimated that the currently diagnosed population of IgG4-RD patients in the U.S. is approximately 20,000, with comparable prevalence rates globally.
Currently, there are no approved therapies for IgG4-RD, and the standard of care involves glucocorticoids, which often lead to complications and comorbidities. B cell-depleting agents like rituximab are sometimes used off-label, but they are associated with infections and can compromise a patient’s response to vaccinations.
Zenas BioPharma's Strategic Focus
Zenas BioPharma is dedicated to developing and commercializing transformative immunology-based therapies. The company's lead product candidate, obexelimab, represents a strategic focus on autoimmune diseases with significant unmet medical needs.
