Enfortumab vedotin (EV), an antibody drug conjugate directed against Nectin-4, a cell-adhesion molecule highly expressed in urothelial carcinomas, has become a major therapeutic advance. By delivering a microtubule-disrupting payload selectively to tumor cells, EV provides significant survival benefits and durable responses in previously treated patients. However, the mechanisms of action (MoA) and resistance (MoR) underlying EV activity remain only partially understood. As part of the UNLOCK translational research program, which integrates clinical and preclinical approaches to elucidate MoA and MoR of innovative anticancer agents, we established and comprehensively characterized a large panel of Patient-derived xenografts (PDX) models generated from EV-treated urothelial cancer patients.

Fresh tumor biopsies were prospectively collected at different time points: at baseline prior to EV initiation and at the time of disease progression following acquired resistance to EV. PDX models were generated in NOD Scid Gamma mice and underwent extensive characterization including immunohistochemistry, whole exome sequencing, bulk RNA sequencing, and pharmacological validation.

To date, 28 tumor biopsies have been obtained from 25 patients, including 17 baseline samples and 11 progression samples. We successfully established 14 PDX models (10 baseline and 4 resistant) corresponding to an overall 50% engraftment rate. These PDX faithfully recapitulate the genetic, transcriptional, phenotypic, and pharmacologic features of the respective patient tumors, providing a robust and physiologically relevant preclinical platform. Immunohistochemistry revealed cell-surface expression of additional clinically actionable ADC targets includingTROP2, HER3, and HER2 in both patient samples and corresponding PDX. Furthermore, in tumors harboring activating FGFR3 mutation, the combination of EV with FGFR3 inhibitors demonstrated encouraging synergistic activity in pharmacologic assays.

The UNLOCK program provides a unique preclinical resource to dissect the MoA and MoR to Enfortumab Vedotin and to support the development of novel therapeutic strategies for urothelial cancer.