Enfortumab Vedotin Induces Immunogenic Cell Death and Shows Enhanced Preclinical Antitumor Activity When Combined With a PD-1 Inhibitor

Enfortumab vedotin is a Nectin-4-directed antibody–drug conjugate designed to deliver the microtubule-disrupting agent monomethyl auristatin E (MMAE) in tumor cells. Using preclinical models of urothelial cancer (UC), we expand the understanding of the multifaceted mechanism of action for enfortumab vedotin that includes direct cytotoxicity on Nectin-4–positive tumor cells, indirect bystander effect on neighboring Nectin-4–negative tumor cells, and MMAE-mediated induction of immunogenic cell death (ICD) and associated increase in activated immune cells in the tumor microenvironment. Importantly, vaccination with enfortumab vedotin-treated tumor cells drives antitumor immunity and provides protection against rechallenge in mice. MMAE-mediated ICD induction modulates the tumor microenvironment in a complementary manner to immune checkpoint inhibition. Accordingly, enfortumab vedotin plus PD-1 inhibitor shows enhanced antitumor activity in vivo. These preclinical results demonstrate the underlying mechanisms consistent with the significantly improved clinical outcomes observed for enfortumab vedotin plus pembrolizumab relative to chemotherapy in the first-line treatment of la/mUC. T24-hNectin-4 cells were cultured as described and resuspended in 50% Matrigel before subcutaneous injection of 5×106 T24-hNectin-4 xenograft tumor cells (0.1 mL volume) in the flanks of athymic nude female mice (Envigo, BALB/cAnNHsd). Tumor pieces were passaged via trocar needle two times to establish consistent engraftment. On Day 15 post implantation, tumor volumes reached ~200 mm3 (calculated using 0.5 × [length] × [width]2), and the mice were treated with a single intraperitoneal (IP) dose of 3 mg/kg enfortumab vedotin. As a control, mice were treated with 3 mg/kg IgG-MMAE. Tumors were harvested 5 days after treatment and processed for RNA-seq (Illumina HiSeq platform),