Research Summary

Obexelimab Reduced IgG4-Related Disease Flares vs Placebo in Phase 3 Trial

Anthony Calabro, MA

Key Highlights

  • Obexelimab significantly reduced the risk of IgG4-related disease flare requiring rescue therapy vs placebo over 52 weeks.
  • Flares occurred in 26.8% of patients receiving obexelimab and 54.6% receiving placebo.
  • Complete remission at week 52 was more frequent with obexelimab than placebo, at 37.1% vs 19.6%.
  • Cumulative glucocorticoid rescue therapy exposure was lower with obexelimab than placebo.

Weekly subcutaneous obexelimab significantly lowered the risk of disease flare and reduced glucocorticoid exposure among patients with active immunoglobulin G4–related disease (IgG4-related disease), according to phase 3 findings published in The New England Journal of Medicine.

IgG4-related disease is a chronic, immune-mediated fibroinflammatory disorder that can affect virtually any organ system. Glucocorticoids remain a cornerstone of treatment, but their use is limited by toxic effects, and relapse is common after discontinuation. Obexelimab is a bifunctional monoclonal antibody designed to inhibit B-cell activity through coengagement of CD19 and FcγRIIb without inducing B-cell depletion.

Researchers conducted the INDIGO trial, a phase 3, double-blind, randomized, placebo-controlled study of adults with active IgG4-related disease. Patients received subcutaneous obexelimab 250 mg or placebo once weekly for 52 weeks. In both groups, glucocorticoids were tapered according to a standardized schedule to discontinuation at week 8. The primary end point was time to first IgG4-related disease flare requiring rescue therapy, as determined by both the investigator and an independent adjudication committee.

Study Findings

From January 2023 through November 2024, 194 patients underwent randomization, with 97 assigned to obexelimab and 97 assigned to placebo. Overall, 172 patients completed the 52-week double-blind treatment period. The mean age was 59.1 years, 66.5% of patients were men, 66.5% had recurrent disease, and 93.3% had 2 or more affected organs.

Obexelimab significantly prolonged time to first disease flare requiring rescue therapy compared with placebo (hazard ratio, 0.44; 95% CI, 0.28-0.71; P < .001). Flares were reported in 26 patients in the obexelimab group (26.8%) and 53 patients in the placebo group (54.6%). Obexelimab also demonstrated benefit across key secondary end points, including investigator-determined time to first flare (hazard ratio, 0.41; 95% CI, 0.26-0.66; P < .001), adjusted annualized adjudicated flare rate requiring rescue therapy (0.34 vs 0.70 flares per year), complete remission at week 52 (37.1% vs 19.6%; P = .005), and cumulative glucocorticoid rescue therapy dose through week 52 (least-squares mean, 329.5 mg vs 929.8 mg; P = .004).

Adverse events occurred in 97.9% of patients receiving obexelimab and 95.9% receiving placebo. Events reported at least 4 percentage points more often with obexelimab included arthralgias, nasopharyngitis, hypersensitivity, diarrhea, pyrexia, and urticaria. Serious adverse events occurred in 10.3% of patients in the obexelimab group and 18.6% in the placebo group.

Clinical Implications

According to the study authors, the findings suggest that obexelimab offers a distinct B-cell–targeted approach for IgG4-related disease by inhibiting B-cell activation without sustained B-cell depletion. The authors also stated that the glucocorticoid-sparing potential of obexelimab is of particular interest because glucocorticoids are part of current standard treatment despite their toxic-effect burden.

In an editorial published in The New England Journal of Medicine, Thomas Dörner, MD noted that despite its effectiveness, the cumulative toxic effects of glucocorticoids are considerable, and durable disease control remains challenging, which makes the study results by Delle-Torre and colleagues all the more significant.

“This phase 3 INDIGO trial of obexelimab is notable, not only because it showed a significantly lower risk of disease flare and significantly less glucocorticoid exposure than placebo, but also because it advances a mechanistically distinct approach to pathogenic B-cell responses,” Dr. Dörner wrote.2

The authors noted that the 52-week treatment period does not establish long-term durability of effect or fully characterize the safety profile or economic implications of extended treatment. They also reported imbalances in racial and regional distribution between trial groups, which may affect generalizability.

Expert Commentary

In this phase 3 trial, treatment with obexelimab led to a significantly lower risk of disease flare and significantly less glucocorticoid exposure among patients with IgG4-related disease than placebo, without increasing the risk of serious adverse events,” the authors concluded. “As a B-cell–inhibiting agent with a distinct mechanism of action and a subcutaneous formulation suitable for self-administration, obexelimab may offer a valuable addition to the treatment options for this chronic disease.”

References

  1. Della-Torre E, Baker MC, Zhang W, et al; INDIGO Trial Investigators. Obexelimab for the treatment of IgG4-related disease. N Engl J Med. Published June 2, 2026. doi:10.1056/NEJMoa2601337
  2. Dörner T. Obexelimab and the Promise of Nondepleting B-Cell Therapy in IgG4-Related Disease. N Engl J Med. Published online June 2, 2026. doi:10.1056/NEJMe2605617