HPN328 is a humanized, trispecific T-cell activating construct (TriTAC) targeting CD3 for T-cell engagement, HSA for half-life extension, and DLL3 on tumor cells. It induces potent T-cell-mediated cytotoxicity against DLL3-expressing small cell lung cancer (SCLC), leading to tumor regression and long-term anti-tumor immunity. M.W 53.06 kDa.