Illumina Inc. and Merck & Co. Inc. are partnering to commercialize tests identifying genetic mutations used in the assessment of homologous recombination deficiency (HRD). Patients whose tumors are HRD-positive may be eligible for targeted chemotherapy treatment by a class of precision medicines called PARP inhibitors. The companies will develop tests utilizing Illumina's Trusight Oncology 500 assay for genomic profiling, which is designed to identify 523 known and emerging tumor biomarkers.