Emerging drugs in chronic myelogenous leukaemia

Dasatinib, a multikinase inhibitor: therapy, safety, and appropriate management of adverse events

Tyrosine kinase inhibitors are the standard of care for the treatment of chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia. Dasatinib is a second-generation tyrosine kinase inhibitor that has been shown to be efficacious in treatment of patients with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia who are resistant or intolerant to frontline imatinib. In clinical trials of dasatinib, the adverse events that arise during therapy are mostly mild to moderate in severity and are usually reversible and manageable with appropriate intervention. Cytopenias can be treated with dose modification or interruption. Pleural effusions can be effectively managed with prompt delivery of supportive care and dose modification. Patients at risk of cardiac abnormalities or bleeding-related events require careful monitoring. Pharmacokinetic analysis of dasatinib indicates interactions with a number of other agents and a complete treatment history should be taken before initiating therapy because mitigating drug-drug interactions are critical for patient safety.

Use of inhibitors in the study of MAP kinases

The mitogen-activated protein (MAP) kinases are ubiquitous intracellular signaling proteins that respond to a variety of extracellular signals and regulate most cellular functions including proliferation, apoptosis, migration, differentiation, and secretion. The four major MAP kinase family members, which include the ERK1/2, JNK, p38, and ERK5 proteins, coordinate cellular responses by phosphorylating and regulating the activity of dozens of substrate proteins involved in transcription, translation, and changes in cellular architecture. Uncontrolled activation of the MAP kinases has been implicated in the initiation and progression of a variety of cancers and inflammatory disorders. As such, the ability to manipulate the activity of MAP kinase proteins with specific pharmacological inhibitors has received much attention as research tools for understanding basic mechanisms of cellular functions and for clinical tools to treat diseases. A variety of pharmacological inhibitors have been developed to selectively block MAP kinases directly or indirectly through targeting upstream regulators. This chapter will provide an overview of some of the current inhibitors that target MAP kinase signaling pathways and provide methodology on how to use selective MAP kinase inhibitors and immunoblotting techniques to monitor and quantify phosphorylation of MAP kinase substrates.

New dosing schedules of dasatinib for CML and adverse event management

Resistance to imatinib in patients with chronic myelogenous leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) has emerged as a significant clinical issue. Dasatinib is a tyrosine kinase inhibitor that has 325-fold greater in vitro activity against native BCR-ABL (breakpoint cluster region-Abelson leukemia virus) compared with imatinib and can overcome primary (intrinsic) and secondary (acquired) imatinib resistance. Here, we review the clinical profile of dasatinib in imatinib-resistant and -intolerant patients and share clinical approaches for managing adverse events (AEs) to ensure maximum patient benefit. References were obtained through literature searches on PubMed as well as from the Proceedings of Annual Meetings of the American Society of Clinical Oncology, the American Society of Hematology, and European Hematology Association. Phase II and III studies of dasatinib in patients with imatinib-resistant or -intolerant CML in any phase or Ph+ ALL were selected for discussion. Dasatinib is currently indicated for the treatment of patients with imatinib-resistant or -intolerant CML or Ph+ ALL. AEs associated with dasatinib are typically mild to moderate, and are usually resolved with temporary treatment interruption and/or dose adjustments. A Phase III dose optimization study showed that in patients with chronic phase (CP) CML, 100 mg once-daily dasatinib improves the safety profile, particularly pleural effusion and thrombocytopenia, while maintaining efficacy compared with the previously recommended dose of 70 mg twice-daily. Dasatinib has a manageable safety profile. For patients with CP CML, a new recommended starting dose of 100 mg once daily has recently been approved. The recommended dose for patients with advanced CML or Ph+ ALL remains 70 mg twice daily.

Strategies for overcoming imatinib resistance in chronic myeloid leukemia

Imatinib was the first treatment for chronic myeloid leukemia (CML) that specifically targeted the causative BCR-ABL oncoprotein, and represented a major therapeutic advance in this disease; however, some patients develop resistance or intolerance. Resistance can be classified as BCR-ABL-dependent (e.g., mutation in the BCR-ABL gene) or BCR-ABL-independent (alternative pathways of disease progression, e.g., SRC-family tyrosine kinases). The investigation of therapeutic options post-imatinib failure resulted in the development and regulatory approval of dasatinib, a BCR-ABL and SRC-family kinase inhibitor. Dasatinib is active across all phases of CML and Philadelphia chromosome-positive acute lymphoblastic leukemia, and demonstrates activity in almost all imatinib-resistant mutations. Other therapeutic options are also under investigation, with nilotinib being the most clinically advanced. Nilotinib is an analog of imatinib with similar multiple kinase targets, but without inhibition of SRC, and reduced in vitro activity against BCR-ABL P-loop mutations compared with dasatinib. Similar to dasatinib, nilotinib has no activity against T315I mutations. The availability of dasatinib and development of other tyrosine kinase inhibitors provide positive prospects for patients with imatinib-resistant or -intolerant CML. Here, we discuss several of these new strategies for treating patients after imatinib failure.

Rituximab associated to imatinib for coexisting therapy-related chronic myeloid leukaemia and relapsed non-Hodgkin lymphoma

Philadelphia positive (Ph+) chronic myeloid leukaemia (CML) presenting synchronously or following non-Hodgkin lymphoma (NHL) has only rarely been reported. Herein, we refer on a case of Ph+ CML occurring after a breast cancer and a NHL with multiple relapses. After obtaining complete cytogenetic remission with imatinib, the patient presented a new NHL relapse, that was treated with rituximab concomitantly to imatinib. Therapy was well tolerated and the patient is presently alive in complete remission of either NHL and CML. We also reviewed the literature relating the uncommon association of these two unrelated diseases.