Small Molecules: Big Changes in the Cancer Treatment Paradigm

Small molecules, a growing class of targeted therapies, have flourished over the last decade. With increased knowledge on molecular cell signaling, targeted therapy has been refined to targeting molecular targets upstream from the nucleus that are key players in the communication system that regulates cancer cell growth. This article reviews the mechanisms of small molecules with a particular emphasis on tyrosine kinase inhibitors, as well as the literature that supports the current clinical use in the treatment of a variety of solid and hematological malignancies.

Treatment Options in Imatinib-Resistant Chronic Myelogenous Leukemia

Objective:

To discuss new therapeutic options available in the treatment of chronic myelogenous leukemia (CML) in patients who (ailed or were intolerant to imatinib therapy.

Data Sources:

Literature was accessed via MEDLINE (1966–May 2007). EMBASE (199l–3rd quarter 2007). the Proceedings of the American Society of Hematology (2000–2006), and the Proceedings of the American Society of Clinical Oncology (2000–2007). Search terms included imatinib, dasatinib, nilotinib. and chronic myelogenous leukemia.

Study Selection and Data Extraction:

Meeting abstracts and studies that reported preclinical and Phase 1, 2, and 3 trials published in English are included.

Data Synthesis:

Imatinib is the standard of care for CML; however, some patients develop resistance or are intolerant to the drug. Phase 1 and 2 clinical data for the more potent tyrosine kinase inhibitors, dasatinib and nilotinib, are promising. Hematologic and cytogenetic responses are reported with both. There does not appear to be cross-resistance between the drugs, although neither is effective against all mutations ol the hallmark molecular marker, the Philadelphia chromosome. Novel agents are also being examined for the treatment of patients with CML, including aurora kinase and farnesyl transferase inhibitors, as well as combination therapies.

Conclusions:

Dasatinib and nilotinib are second-tine options for patients who have CML and are resistant or intolerant to imatinib. Toxicity profiles between agents may differ. Clinical trials with these drugs and others are ongoing.