PARP inhibitors are employed to disturb the DDR and stall DNA replication to trigger apoptosis in cancers (also called synthetic lethality), specifically for cancers with homologous recombination deficiency (HRD), which refers to tumor BRCA, ATM, or other mutant, or a genomic instability score ≥42.482, 483. The gene discussed is PARP1; the disease is neoplasm.