In ARIEL2, Swisher et al23,24 showed that mutations in RAD51C/D were associated with genomic HRD (based on high genomic LOH) and response to the PARP inhibitor rucaparib in 5 of 7 patients (71.4%) with relapsed high-grade ovarian cancer, reaching a median progression-free survival similar to patients with mutated BRCA1/2. The gene discussed is BRCA1; the disease is ovarian cancer.