– Phase 3 INDIGO open-label extension findings demonstrated sustained clinical activity of obexelimab –

– Additional analyses of secondary endpoints showed that significantly fewer patients experienced clinically meaningful cumulative glucocorticoid toxicity at week 52 –

– Initial open-label extension sub-study findings demonstrated vaccine responses following a treatment-free window –

– These new findings add to the clinical evidence supporting obexelimab’s investigational role as a reversible, steroid-sparing, B-cell inhibitor for the treatment of IgG4-RD –

WALTHAM, Mass., Oct. 12, 2026 (GLOBE NEWSWIRE) -- Zenas BioPharma, Inc. ("Zenas" or the "Company") (NASDAQ:ZBIO), a clinical-stage global biopharmaceutical company advancing therapies for patients living with autoimmune and inflammatory diseases, today announced new obexelimab data in immunoglobulin G4-related disease (IgG4-RD) presented at the 6th International Symposium on IgG4-Related Disease, held October 8-10, 2026, in Cambridge, Massachusetts. The presentations included longer-term flare protection and safety data from the Phase 3 INDIGO open-label extension, initial findings from an associated vaccine response sub-study, and an analysis of glucocorticoid-associated toxicity from the randomized, controlled period of INDIGO.

Phase 3 INDIGO Open-Label Extension Data

Participants who completed the 52-week randomized, controlled period of the Phase 3 INDIGO study could enter the open-label extension and receive 250 mg obexelimab subcutaneously once weekly. The open-label extension evaluated longer-term flare protection and safety of continued obexelimab treatment in patients with IgG4-RD.

  • The 12-month probability of remaining flare-free was 0.93 based upon investigator- and adjudication committee-confirmed flares requiring rescue therapy, and 0.87 based upon investigator-determined flares requiring rescue therapy, with five patients pending adjudication at the time of the data cutoff.
  • The median and mean cumulative glucocorticoid rescue doses were 0 mg and 105 mg, respectively.
  • Adverse event rates were comparable to or lower than those observed during the randomized, controlled period.
     

Glucocorticoid-Associated Toxicity Results

This Phase 3 INDIGO trial sub-analysis evaluated glucocorticoid-associated toxicity in patients with IgG4-RD using the Glucocorticoid Toxicity Index (GTI).

  • Obexelimab significantly reduced cumulative glucocorticoid toxicity versus placebo at week 52 (GTI Cumulative Worsening Score difference: -11.4; p=0.021).
  • Fewer patients receiving obexelimab reached clinical thresholds for cumulative glucocorticoid toxicity versus placebo.

Influenza and COVID-19 Vaccine Sub-Study Results

Initial analyses from the ongoing sub-study of the INDIGO open-label extension assessed immune responses to vaccination during a planned treatment-free window. In addition, the preservation of pre-existing influenza and SARS-COV-2 immunity following long-term obexelimab exposure was evaluated.

  • Vaccination during the treatment-free window resulted in seroimmunity to influenza in 6 of 7 (86%) participants and seroimmunity to COVID-19 in 4 of 4 (100%) participants.
  • No disease flares were observed during the treatment-free vaccination window, lasting an average of 34.6 days.
  • Participants (n=7) maintained pre-existing markers of immunity following long-term obexelimab treatment (71% for influenza and 50% for COVID-19).