TPP-45142—an Anti-HER2 T-cell Engager—Designed for Selective HER2-Low Cancer Immunotherapy

The standard of care for patients with HER2-positive cancers is well established, but a significant unmet need exists for patients with HER2-low tumors, who do not meet the eligibility criteria for trastuzumab, and for patients with HER2-positive tumors, who are refractory to trastuzumab treatment. Therefore, in this study, we developed a NANOBODY domain-based HER2-targeting, T-cell receptor αβ-based T-cell engager (TCE) molecule-TPP-45142; it recognizes a HER2 epitope distinct from that recognized by trastuzumab and pertuzumab and redirects T cells to kill HER2-low cancers such as breast, gastric, and gastroesophageal junction adenocarcinoma cancers. TPP-45142 mediated potent T cell-dependent cytotoxicity against HER2-low cancer cell lines in vitro and inhibited in vivo tumor growth of HER2-low breast cancer xenografts. TPP-45142 was highly selective toward tumor cells expressing low HER2 levels than toward normal cardiac cells and exhibited a favorable therapeutic index as per a cytokine release assay. Thus, TPP-45142, with an improved safety profile, is a promising next-generation TCE for treating challenging HER2-low cancers.