Carfilzomib. Molecular model of the cancer drug Carfilzomib. Carfilzomib is a proteasome inhibitor that is used in cancer treatment. This class of drugs inhibits the action of proteasomes, cellular complexes that break down proteins. Carfilzomib irreversibly binds to and inhibits the chymotrypsin-like activity of the 20S proteasome. It is used to treat multiple myeloma. Atoms are represented as spheres and are colour-coded: hydrogen (white), carbon (light blue), oxygen (red) and nitrogen (dark blue).