Study Objective: This research checks how well a drug called obexelimab works to stop flare-ups in people with IgG4-related disease, a condition where the immune system attacks the body's own tissues.

Study Length: The study lasts up to 116 weeks, including screening and follow-up periods. Initial treatment lasts 1 year, followed by an optional extra year.

Study Process: Participants will be randomly given either obexelimab or a placebo (a harmless, inactive substance) through injections. All participants will taper off steroid medication by the 8th week. Regular clinic visits will monitor any flares, which are sudden worsening of symptoms.

Inclusion Criteria: Adults 18+ with diagnosed IgG4-RD, showing active symptoms needing steroid treatment.

• Participation may last over 2 years.
• Regular clinic visits are required.
• Medication and health monitoring are part of the study process.

Exclusion Criteria: Individuals with certain conditions or recent treatments, like high steroid use or recent vaccinations, may not participate.