FDA approval cleared Foundation Medicine CDx assays as companion diagnostics for Pfizer’s Talzenna plus Xtandi regimen in metastatic castration-resistant prostate cancer. The decision authorizes FoundationOne CDx to identify patients with homologous recombination repair (HRR) gene mutations for treatment selection. The paired approval reinforces the growing role of genomic companion testing in prostate cancer therapeutics, especially as PARP inhibitor-based combinations expand. For manufacturers and clinical labs, it also emphasizes the need for consistent assay performance across patient populations and real-world workflow constraints. Clinically, the approval supports a more streamlined biomarker-and-therapy pathway for HRR-mutant patients moving into treatment, with potential downstream effects on utilization patterns for next-generation sequencing panels used in CDx settings.