In vitro anti-leukaemia activity of pyrrolo[1,2-b][1,2,5]benzothiadiazepines (PBTDs)

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized by unregulated growth of myeloid leukemia cells in the bone marrow and accumulation of these cells in the blood. CML represents approximately 15-20% of all adult leukemia and the disease development is clearly linked to the constitutively active tyrosine kinase of the chimeric protein BCR-ABL. It is encoded by the Bcr-Abl fusion gene sequence as the result of chromosome 9/22 translocation (Philadelphia chromosome) or other aberrant cytogenetic events. The development of targeted agents that specifically inhibit the tyrosine kinase (TK) activity of BCR-ABL has revolutionized the treatment of CML. Imatinib is now the first-line treatment for chronic phase CML, and several newer tyrosine kinase inhibitors (TKIs) such as dasatinib and nilotinib have been added to the pharmacologic compendium. Despite the proven efficacy of TKIs to induce hematological and cytogenetic remission, the large majority of patients still have molecularly detectable disease. Therefore, new options are needed to improve therapeutic success in the treatment of leukemia. Pyrrolo[1,2-b][1,2,5]benzothiadiazepine 5,5-dioxides (PBTDs) induced apoptosis in human BCR-ABL expressing leukemia cells. The apoptotic activity was also observed in primary leukemic blasts, obtained from CML patients at onset or from patients in blast crisis and who were imatinib- dasatinib- and nilotinib resistant. These results suggests that these compounds are promising agent for the treatment of leukemia. Due to the fact that the phenomenon of resistance to TKIs remains a major issue in the treatment of patients with CML, the identification of new drugs may be of clinical relevance. This review summarises patents and papers dealing with the present understanding of mechanism of action and the most relevant data concerning TKs inhibition.