I promised to post the story of imatinib (trade name: Gleevec), the wonderdrug for chronic myeloid leukemia (CML) that we talked about in class last week.
Before the discovery of imatinib, CML was basically a death sentence. Although CML is a chronic leukemia, and therefore has a relatively good prognosis (compared to acute leukemias), it is more aggressive than most other chronic leukemias, with an overall prognosis on the order of a few years. Before imatinib, the best treatment available was bone marrow transplant, and the results were pretty grim.
Enter imatinib. Imatinib is a tyrosine kinase inhibitor – but a really specific tyrosine kinase inhibitor, and it happens to act on the tyrosine kinase made by the hybrid bcr-abl gene in CML (the gene that results from the translocation between chromosomes 9 and 22). This is important, because you can’t just go around inhibiting any and all tyrosine kinases, because we have tons of normal tyrosine kinases in all different types of cells in our body!
So imatinib blocks the tyrosine kinase made by the malignant cells in CML, preventing it from stimulating cell growth. This means that the tumor cells no longer have the capacity to proliferate uncontrollably, and the disease is held in check. The results were so amazing in early clinical trials that the drug was released for use in record time, because it would have been inhumane to withhold the drug for bureaucratic purposes.
Now, imatinib is standard, first-line therapy for CML, and it works incredibly well in most patients. It is being used for other malignancies that have similar tyrosine kinases, with excellent results. And it has sparked interest (and research) around chemotherapeutic agents that act against unique tumor cell features like the mutated tyrosine kinase in CML. This is a whole different way of attacking tumors, and it’s so much more selective and effective than the method used by traditional chemotherapeutic agents, which involves simply killing all dividing cells.
When you have time, you might want to check out this New York Times article about the inventor of imatinib. It’s rare to see such a happy story in the area of leukemia therapy – so I wanted to be sure you knew about it!