Targeted Therapies for Cancer
Targeted cancer therapies have been developed that interfere with a variety of other cellular processes. Some targeted therapies block specific enzymes and growth factor receptors involved in cancer cell proliferation. These drugs are also called signal transduction inhibitors. FDA-approved targeted therapies are listed below:
- Imatinib mesylate (Gleevec®) is approved to treat gastrointestinal stromal tumor (a rare cancer of the gastrointestinal tract), certain kinds of leukemia, dermatofibrosarcoma protuberans, myelodysplastic/myeloproliferative disorders, and systemic mastocytosis. It targets several members of a class of proteins called tyrosine kinase enzymes that participate in signal transduction. These enzymes are overactive in some cancers, leading to uncontrolled growth. It is a small-molecule drug, which means that it can pass through cell membranes and reach targets inside the cell.
- Dasatinib (Sprycel®) is approved to treat some patients with CML or acute lymphoblastic leukemia. It is a small-molecule inhibitor of several tyrosine kinase enzymes.
- Nilotinib (Tasigna®) is approved to treat some patients with CML. It is another small-molecule tyrosine kinase inhibitor.
- Trastuzumnab (Herceptin®) is approved for the treatment of certain types of breast cancer as well as some types of gastric or gastroesophageal junction adenocarcinoma. It is a monoclonal antibody that binds to the human epidermal growth factor receptor 2 (HER-2). HER-2, a receptor with tyrosine kinase activity, is expressed at high levels in some breast cancers and also some other types of cancer. The mechanism by which trastuzumab acts is not completely understood, but one likely possibility is that by binding to HER-2 on the surface of tumor cells that express high levels of HER-2, it prevents HER-2 from sending growth-promoting signals. Trastuzumab may have other effects as well, such as inducing the immune system to attack cells that express high levels of HER-2.
- Lapatinib (Tykerb®) is approved for the treatment of certain types of advanced or metastatic breast cancer. This small-molecule drug inhibits several tyrosine kinases, including the tyrosine kinase activity of HER-2. Lapatinib treatment prevents HER-2 signals from activating cell growth
- Gefitinibo (Iressa®) is approved to treat patients with advanced non-small cell lung cancer. Its use is restricted to patients who, in the opinion of their treating physician, are currently benefiting, or have previously benefited, from gefitinib treatment. This small-molecule drug inhibits the tyrosine kinase activity of the epidermal growth factor receptor (EGFR), which is overproduced by many types of cancer cells.
- Erlotinib (Tarceva®) is approved to treat metastatic non-small cell lung cancer and pancreatic cancer that cannot be removed by surgery or has metastasized. This small-molecule drug inhibits the tyrosine kinase activity of EGFR.
- Cetuximab (Erbitux®) is a monoclonal antibody that is approved for treating some patients with squamous cell carcinoma of the head and neck or colorectal cancer. It binds to the external portion of EGFR, thereby preventing the receptor from being activated by growth signals, which may inhibit signal transduction and lead to antiproliferative effects.
- Panitumumab (Vectibix®) is approved to treat some patients with metastatic colon cancer. This monoclonal antibody attaches to EGFR and prevents it from sending growth signals.
- Temsirolimus (Torisel®) is approved to treat patients with advanced renal cell carcinoma. This small-molecule drug is a specific inhibitor of a serine/threonine kinase called mTOR that is activated in tumor cells and stimulates their growth and proliferation.
- Everolimus (Afinitor®) is approved to treat patients with advanced kidney cancer whose disease has progressed after treatment with other therapies or patients with subependymal giant cell astrocytoma who also have tuberous sclerosis and are unable to have surgery. This small-molecule drug binds to a protein called immunophilin FK binding protein-12, forming a complex that in turn binds to and inhibits the mTOR kinase.