Pharmacokinetics of Dasatinib in a Patient with Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia During Treatment with Anti-Tuberculosis Therapy

Dasatinib is a second generation protein-tyrosine kinase inhibitor (TKI) indicated for first line treatment of chronic myeloid leukemia (CML) and second line treatment of Philadelphia chromosome-positive acute lymphoblastic leukemia (ALL) in patients who are imatinib resistant or intolerant.

In this study, we present the case of a patient with Philadelphia chromosome- positive ALL, intolerant to imatinib, who developed reactivated tuberculosis (TB) while receiving dasatinib during maintenance chemotherapy. The purpose of our study was to determine the effects of concomitant anti-TB therapy on dasatinib exposure by measuring plasma dasatinib levels using three different oral doses of the drug in this patient.

The patient was treated with isoniazid, rifampin, ethambutol, pyrazinamide and pyridoxine for 2 months, followed by isoniazid, rifampin and pyridoxine for an additional 4 months. Dasatinib therapy was continued at the initiation of TB therapy using 100 mg po od, and titrated by 50 mg increments to 200 mg po od. Dasatinib plasma levels were measured prior to initiating anti-TB treatment and at regular intervals during concomitant treatment using three different dasatinib doses.

Eight days after initiation of anti-tuberculosis therapy, the apparent clearance of dasatinib had increased from 1410 to 2174 L/h at 100 mg. However, at 150 mg and 200 mg doses, apparent clearance had decreased to levels lower than baseline. As expected, the direction of peak plasma concentration changes was inverse to the changes in apparent clearance: C_max values were 30 at baseline, and 22, 46, 102 ng/mL for the 3 doses of dasatinib during anti-TB therapy, respectively.

Our findings suggest dasatinib clearance is increased by approximately 50% shortly after initiating anti-tuberculosis treatment and increasing the dose of dasatinib during anti-TB therapy was able to restore dasatinib plasma levels to those observed before initiation of anti-TB therapy.

(This work was supported by an unrestricted grant from Bristol Myers Squib)

No relevant conflicts of interest to declare.