Controversies about immunoglobulin replacement therapy in HSCT recipients with hypogammaglobulinemia

The efficacy of immunoglobulin replacement therapy (IgRT) has been demonstrated for primary immune deficiency diseases and hematological malignancies such as chronic lymphocytic leukemia (CLL) or multiple myeloma with hypogammaglobulinemia. Clinical development of anti-B cell therapies including a monoclonal antibody, bispecific antibody, or chimeric antigen receptor T-cell therapy which could result in severe hypogammaglobulinemia accelerates the argument of prophylactic use of IgRT. Clinical guidelines for CLL describe immunoglobulin administration in patients with a low IgG who have experienced a severe/repeated bacterial infection. The utility in hematopoietic stem-cell transplantation (HSCT) remains unknown. Although an early randomized trial demonstrated that IgRT decreased infection risk and transplant-related mortality after HSCT, subsequent clinical trials could not validate the benefit. Consequently, a meta-analysis did not show the benefit of IgRT in HSCT. Most of the available data derives from matched-related HSCT using myeloablative regimen, and the impact in haploidentical and cord blood transplantation, or reduced-intensity HSCT remains unknown. One crucial issue is that no studies exist for patients with only hypogammaglobulinemia after HSCT. Other challenges are heterogeneous patient characteristics, or immunoglobulin formulation, dosage, schedule, route and duration of IgRT. Without evidence in HSCT, it would be reasonable to follow the guidelines for other diseases with hypogammaglobulinemia.