Background: The antibody-drug conjugate enfortumab vedotin (EV) releases a cytotoxic agent into tumor cells via binding to the membrane receptor NECTIN-4. EV has been recently approved for patients with metastatic urothelial carcinoma (mUC) without prior assessment of the tumor receptor status as ubiquitous NECTIN-4 expression is assumed.
Objective: To determine the prevalence of membranous NECTIN-4 protein expression in primary tumors (PRIM) and patient-matched distant metastases (MET).
Main outcomes and measures: Membranous NECTIN-4 protein expression was measured (H-score) by immunohistochemistry (IHC) in PRIM and corresponding MET (N=137) and in a multicenter EV-treated cohort (N=47). Progression-free survival (PFS) after initiation of EV treatment was assessed for the NECTIN-4 negative/weak (H-score 0-99) versus moderate/strong (H-score 100-300) subgroup. The specificity of the NECTIN-4 IHC staining protocol was validated by establishing CRISPR-Cas9-induced polyclonal NECTIN-4 knockouts.
Results: In our cohort, membranous NECTIN-4 expression significantly decreased during metastatic spread (Wilcoxon matched pairs P<0.001, median H-score=40, interquartile range (IQR): 0-140), with 39.4% of MET lacking membranous NECTIN-4 expression. In our multicenter EV cohort, absence or weak membranous NECTIN-4 expression (34.0% of the cohort) was associated with a significantly shortened PFS on EV (Log-rank P<0.001).
Conclusion: Membranous NECTIN-4 expression is frequently decreased or absent in mUC tissue. Of note, the clinical benefit of EV strongly depends on membranous NECTIN-4 expression. Thus, our results are of highest clinical relevance and argue for a critical reconsideration of the current practice and suggest that the NECTIN-4 receptor status should be determined (ideally in a metastatic/ progressive lesion) before initiation of EV.