ATR and hypoparathyroidism-retardation-dysmorphism syndrome: Although PARP inhibitors are mainly used in BRCA + tumors, recent studies also suggest high responses in non-BRCA mutated cells, including genes like ATM, ATR, RAD51, and BARD1 that are related to genomic instability generation and indicative of homologous recombination deficiency (HRD).