Phase I studies subsequently demonstrated good safety and tolerability up to a dose of 400 mg twice daily, with dose limiting toxicities of grade 4 thrombocytopenia and grade 3 somnolence, and also showed early signals of antitumor activity with a response rate of up to 46% in heavily pre-treated BRCA1/2-mutant cancers [14,15]. The gene discussed is BRCA1; the disease is cancer.