Targeted Therapy
Research continues to search for and identify unique genes and proteins expressed in some cancers that give them dramatic advantages for growth and spread. These oncogenes or oncoproteins are so powerful that the affected cancers become “addicted” to them not just for growth and spread, but for survival. Drugs that target and block the function of such oncogenes or oncoproteins can incapacitate and kill addicted cancer cells much better than traditional therapies. In addition, these targeted drugs often block genes or proteins that are not expressed or not important to functioning of normal cells, which can mean very little toxicity to normal cells in the body.
The prototypical example of a revolutionary targeted therapy is Imatinib (Gleevec) for chronic myelogenous leukemia (CML). Imatinib and the class of similar drugs target the Bcr-Abl gene and its protein product, and in accelerated blast crisis of CML has converted a 100% fatal cancer into 70% curable condition. In GIST (gastrointestinal stromal tumors) Imatinib inhibits PDGFR and c-Kit protein function and has converted a chemotherapy-resistant cancer into a curable disease. Tarceva for the small fraction of non-small cell lung cancers with EGFR mutations can regress and stabilize metastatic cancer for up to 2 years, 6-8 times longer than with standard chemotherapies. Antiangiogenic drugs such as Avastin can starve tumors by reducing their blood supply while improving drug delivery into tumors, nearly doubling the effectiveness of chemotherapy for many cancer types.
Many targeted therapies are now combined with chemotherapy to improved outcomes for many cancers without increasing toxicity. In the future, targeted therapies perhaps in combination raise hope for minimally toxic cancer cures.
