IgG4-related disease - treatment with anti-CD20, anti-CD19 antibodies, and other new drugs.

BACKGROUND: IgG4-related disease (IgG4-RD) can affect any tissue. Characteristic symptoms include tumor-like swelling of one or more organs, lymphadenopathy, involvement of the pancreatic and/or bile ducts, aortitis and retroperitoneal fibrosis, inflammatory swelling of the lacrimal or salivary glands, and nephropathy. Laboratory changes include hyperproteinemia, increased IgG4 concentration, eosinophilia, and elevated circulating plasmablasts. Presence of any of these symptoms should prompt a differential diagnosis focused on IgG4-RD. GOAL: International recommendations for treatment of IgG4-RD were published in 2015, and since then, numerous studies and meta-analyses of new treatment approaches have been published. These indicate that, in 2026, the treatment of choice is monoclonal anti-CD20 antibodies, rituximab or obinutuzumab, or alternatively, the anti-CD19 antibody inebilizumab. Rituximab achieves a significantly higher number of treatment responses and has fewer side effects than the previously used prednisone, whether in monotherapy or in combination with oral immunosuppressants. However, even after rituximab treatment, the rate of early relapses is around 16-20%. Therefore, maintenance therapy with rituximab is recommended. Another approach to achieving a longer-lasting treatment response is the combination of rituximab with cyclophosphamide. In 2025, the anti-CD19 monoclonal antibody inebilizumab was approved in the United States and Europe for the treatment of IgG4-RD. It targets a broader range of B cells than rituximab and induces a longer-lasting therapeutic response. The efficacy of other drugs (obexelimab, abatacept, daratumumab, dupilumab, and others) is documented through case reports and small patient series or phase II clinical trials, and we are awaiting the results of phase III registration studies. CONCLUSION: Anti-CD20 and anti-CD19 antibodies represent the treatment of choice for IgG4-RD. They achieve a high number of complete treatment responses; however, the treatment does not end there, as it is necessary to prevent disease relapses, which are common without maintenance therapy.