Tyrosine kinase inhibitors and the dawn of molecular cancer therapeutics

The clinical application of tyrosine kinase inhibitors for cancer treatment represents a therapeutic breakthrough. The rationale for developing these compounds rests on the observation that tyrosine kinase enzymes are critical components of the cellular signaling apparatus and are regularly mutated or otherwise deregulated in human malignancies. Novel tyrosine kinase inhibitors are designed to exploit the molecular differences between tumor cells and normal tissues. Herein, we will review the current state-of-the-art using agents that target as prototypes Bcr-Abl, platelet-derived growth factor receptor (PDGFR), KIT (stem cell factor receptor), and epidermal growth factor receptor (EGFR). These compounds are remarkably effective in treating diverse cancers that are highly resistant to conventional treatment, including various forms of leukemia, hypereosinophilic syndrome, mast cell disease, sarcomas, and lung cancer. It is now clear that the molecular defects underlying cancer can be targeted with designer drugs that yield striking salutary effects with minimal toxicity.