Olaparib, an inhibitor of oral poly ADP-ribose polymerase (PARP), is increasingly being demonstrated in clinical studies to be effective in HRD gene-deficient cell lines, such as those lacking ATM, in addition to providing sensitization in combination with chemotherapeutic agents and killing BRCA1 or BRCA2 gene-mutated tumor cells. The gene discussed is BRCA2; the disease is neoplasm.