Allosteric inhibitors of Bcr-Abl: towards novel myristate-pocket binders

Among the currently available options for the treatment of chronic myeloid leukemia (CML), ATP-competitive tyrosine kinases inhibitors (Gleevec(®), Dasatinib(®) and Nilotinib(®)) represent one of the most promising therapeutic approaches developed in the last 10-15 years. However, the initial enthusiasm generated by the high response rate to these drugs has been dampened by the development of resistance. The T315I mutation at the gatekeeper residue is very frequent in advanced phases of the disease and is one of the main causes of resistance, disrupting important contact points between the inhibitors and the enzyme. Different strategies have been implemented to overcome this resistance, such as the recent development of more selective non-ATP competitive inhibitors targeting sites outside the ATP-binding cleft. Some of these allosteric inhibitors alter the kinase conformation, while others directly compete with the protein substrates. Another interesting family of allosteric inhibitors is represented by those compounds targeting the myristate-pocket of Bcr-Abl (myristate-pocket binders). The binding of these inhibitors blocks the Bcr-Abl kinase in the inactive conformation and provides an advantage in overcoming drug resistance due to kinase mutations. This review reports the last findings in the development of novel myristate-pocket binders of Bcr-Abl as promising anti-leukemia agents.