The ARIEL2 ovarian cancer trial evaluated the use of the poly-(ADP-ribose) polymerase (PARP) inhibitor, rucaparib, in previously treated patients and found that patients with wild-type BRCA1 or BRCA2 (BRCA1/2) genes and high levels of gLOH were more likely to respond to PARP inhibition and had longer progression-free survival compared to patients with non-elevated gLOH levels19,20. The gene discussed is BRCA1; the disease is ovarian cancer.