CD19×CD3 bispecific T cell engager treatment induces remission in experimental pemphigoid disease

Pemphigoid diseases (PDs) are autoimmune disorders marked by autoantibodies (Aab) against skin and mucous membrane proteins, causing muco-cutaneous blistering in predominantly elderly patients. Since current therapeutics are often insufficient, PDs impose a significant morbidity and mortality burden. CD19×CD3 bispecific T cell engagers (TCEs) - originally developed for B cell malignancies - have shown promise in treatment-refractory autoimmune diseases like systemic sclerosis and rheumatoid arthritis. To explore their potential in PDs, we tested a murine CD19×CD3 TCE in a mouse model of epidermolysis bullosa acquisita (EBA), a prototypical PD. The TCE selectively depleted B cells in blood and bone marrow, but not spleen, of healthy mice. Mice with clinically manifest immunization-induced EBA were randomized to receive either the CD19×CD3 TCE or control treatment upon reaching a predefined disease severity. After 13 weeks, 45% of TCE-treated mice achieved remission, versus 23% of controls. This improvement correlated with reduced antigen-specific B cells, though total and antigen-specific IgG levels were unchanged. These findings suggest that CD19×CD3 TCE preferentially target autoreactive B cells and may be effective at lower doses than those used in oncology. Our data support the potential of CD19×CD3 bispecific T cell engagers as a therapeutic strategy for PDs.