Gemcitabine-Cisplatin Chemotherapy Induces Nectin-4 Downregulation and Enfortumab Vedotin Resistance in Bladder Cancer.

Antibody-drug conjugates (ADCs), particularly enfortumab vedotin (EV) in combination with pembrolizumab, have emerged as transformative treatments for advanced bladder cancer (BC). However, platinum-based chemotherapy, especially gemcitabine-cisplatin (GC), remains a widely used, first-line standard globally. This study investigated the impact of GC-therapy on subsequent ADC responsiveness. Using novel, patient-derived BC models, in vitro selection for acquired GC-resistance consistently resulted in downregulation of the EV target, Nectin-4, and corresponding EV cross-resistance in GC-resistant (GC/R) cells. This decrease in membranous Nectin-4 expression was validated in two independent human BC cohorts: (1) matched transurethral resections and radical cystectomy/lymph node specimens during neoadjuvant therapy and (2) primary tumors and distant metastases during adjuvant GC chemotherapy. Transcriptomic profiling indicated that GC-resistance and Nectin-4 downregulation were linked to a transcriptional shift toward an epithelial-to-mesenchymal transition (EMT)-like phenotype. Large-scale drug screening and transcriptomic data highlighted potential vulnerabilities in GC/R cells, notably associated with the transforming growth factor beta (TGF-beta) signaling pathway. These findings suggest that platinum-based chemotherapy may promote EMT-like transcriptional reprogramming in BC, associated with Nectin-4 loss and EV resistance. As such, assessing membranous Nectin-4 expression prior to EV therapy might be particularly relevant in postplatinum settings. Additionally, identifying alternative, chemotherapy-induced druggable vulnerabilities can inform more effective treatment strategies.