This is exemplified by PARPi used to treat breast, prostate, pancreatic or ovarian cancers with defects in the HR pathway, controlled by the tumour suppressors including (but not exclusive to) BRCA1, BRCA2, PALB2, RAD51C and RAD51D [10, 11, 12, 13]. The gene discussed is BRCA1; the disease is ovarian cancer.