Rubraca (rucaparib) is a cancer medication used to treat ovarian, fallopian tube, or primary peritoneal cancer in patients with an abnormal "BRCA" gene. It is also used for prostate cancer with the same genetic marker when the cancer has spread and other treatments have failed. Rubraca is a PARP inhibitor that works by blocking a protein that repairs DNA in cancer cells, causing the cells to die and the tumor to shrink.