The FDA approved Foundation Medicine’s FoundationOne CDx assay as a companion diagnostic to identify patients for Pfizer’s Talzenna plus Xtandi regimen in HRR-mutated metastatic castration-resistant prostate cancer. The tissue-based test analyzes 324 genes and includes genomic signatures such as microsatellite instability and tumor mutational burden. The approval links a specific biomarker selection strategy to a defined therapeutic combination, reinforcing the continued shift toward molecularly stratified oncology treatment pathways. It also adds another indication for FoundationOne CDx’s use in precision oncology programs. The decision helps streamline patient eligibility for a key prostate cancer regimen where HRR status can determine the therapeutic fit.