BCMA x CD3

Class

BCMA x CD3 T-cell engager

BCMA (B-cell maturation antigen) is a cell-surface protein expressed predominantly on plasma cells, the antibody-producing cells of the immune system, and is markedly overexpressed on malignant plasma cells in multiple myeloma. A BCMA x CD3 bispecific is an engineered antibody with two distinct binding arms: one recognizes BCMA on the tumor cell, the other recognizes CD3, a component of the T-cell receptor complex found on essentially all T cells. By binding both simultaneously, the molecule physically bridges a T cell to a myeloma cell, forming an immunological synapse that triggers T-cell activation independent of the T cell's native antigen specificity. This forces the immune system to attack tumor cells it would otherwise ignore, redirecting cytotoxic killing (via perforin and granzyme release) toward the cancer. The rationale for pairing BCMA with CD3 specifically is that BCMA's expression is largely confined to plasma cells, offering a reasonably selective tumor marker, while CD3 provides a universal handle on the T-cell compartment, allowing polyclonal T-cell recruitment without requiring prior tumor-specific immunity. This class of mechanism is broadly relevant to multiple myeloma and other plasma-cell disorders where BCMA is highly and consistently expressed.