Pharmacokinetics of Venetoclax in Patients With Acute Myeloid Leukemia

Venetoclax has been approved in combination with azacitidine or decitabine or low-dose cytarabine for the treatment of newly-diagnosed acute myeloid leukemia (AML) in adults who are age 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapy. There are several clinical trials of Venetoclax for the treatment of AML. In trial M14-358 (NCT02203773), 91% of the combination of venetoclax and azacitidine were Caucasian, while about 87% of the the combination of Venetoclax and decitabine were Caucasian. In another trial M14-387 (NCT02287233), up to 94.9% of the combination of venetoclax and low-dose cytarabine group were Caucasian. However, the actual proportion of Asian or other races is unknown in both trials. Therefore, there is not enough data from Chinese other Asian races regarding its efficacy or adverse reactions in clinical trials.

According to a venetoclax population pharmacokinetic study published in 2016, which integrated 505 subjects from 8 clinical trials, concluded that race was not a covariate that affect venetoclax PK. However, only 6 Asians (1.19%) were included, and most of the subjects were chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL) or non-Hodgkin's lymphoma (NHL), and the results may not be directly generalized to AML patients. The pharmacokinetics of Venetoclax is affected by many factors, and the most influential factors may be fat content from dietary and concomitant use of CYP3A inhibitors or inducers. In particular, patients with hematological malignancies often require antifungal agents (such as voriconazole, posaconazole) as prophylaxis or treatment of fungal infections during chemotherapy. Therefore, these two factors will be considered in this study.

The most common side effect after using venetoclax is cytopenia. About 40% of patients developed severe neutropenia, 4.7% required interruption of treatment, and 3.7% required dosage reduction in phase 2 clinical trials. Although no patient requires permanent venetoclax treatment discontinuation because of neutropenia, 9% of patients need to discontinue venetoclax treatment due to infection. The incidence of severe thrombocytopenia and anemia is 18% and 15%. Recent studies have found that the incidence of neutropenia and infection seems to be inversely related to the blood concentration of venetoclax, that is, the higher the blood concentration of venetoclax, the lower the incidence of neutropenia and infection.

This observational study is designed to examine the plasma concentration of venetoclax in patients with CLL or AML, to create a pharmacokinetic model of venetoclax in Chinese population, and to analyze the extent to which CYP enzyme inhibitors and inducers may have effect on venetoclax plasma concentration. Moreover, the association between therapeutic effectiveness, adverse events, and venetoclax plasma concentration will also be analyzed in this study, and the final purpose is to establish the principle of clinical dose adjustment in the future.