Abstract:The authors present a case of a 57-year-old patient with chronic myeloid leukemia who was treated with ponatinib and subsequently treated with dasatinib. The patient showed a major molecular response; however, the BCR-ABL1 signal increased with low ponatinib and dasatinib trough concentrations. Cobicistat was used as a pharmacokinetic booster to increase ponatinib and dasatinib exposure, as opposed to increasing the dose. However, ponatinib exposure was not sufficiently increased by cobicistat. The peak dasatinib concentration was successfully increased with cobicistat treatment. Dasatinib and cobicistat cotreatment induced a response in BCR-ABL1 PCR signal, was well tolerated, and led to a substantial reduction in drug costs.