Venetoclax monotherapy was permitted for the treatment of adult patients with CLL/SLL based on one phase I trial (NCT01328626) and two phase II trials (NCT02141282 and NCT01889186), which demonstrated the efficacy and safety profile of venetoclax in patients with previously untreated CLL harboring 17p deletion and relapsed or refractory CLL/SLL, including those with poor prognostic features or progressing on BTK inhibitors. This evidence concerns the gene BTK and B-cell chronic lymphocytic leukemia.