Naptumomab (ABR-217620) is a tumor-targeted superantigen (TTS) fusion protein consisting of a Fab fragment targeting the 5T4 oncofetal antigen and a modified staphylococcal enterotoxin A (SEA/E-120). This product specifically recognizes 5T4 protein expressed on various solid tumors via the Fab fragment and potently activates T cells (primarily by binding to the TCR Vβ chain) through the superantigen component, inducing T cell-mediated cytotoxicity against tumor cells. It bypasses major histocompatibility complex (MHC) restriction to directly recruit and activate a large number of effector T cells into the tumor microenvironment.

Human

Monoclonal

Unconjugated