protein kinase inhibitor (PROH-teen KY-nays in-HIH-bih-ter)
A substance that blocks the action of enzymes called protein kinases. There are many different types of protein kinases and they take part in many cell functions. These include cell signaling, growth, and division. Blocking certain protein kinases may help keep cancer cells from growing. Some protein kinase inhibitors, such as imatinib, vemurafenib, and gefitinib, are used to treat cancer.