This class of drug, proteasome inhibitors, stops proteasomes, which are large protein complexes.

Bortezomib was the first Proteasome inhibitor to be approved for use, and the maker, Millenium Pharmaceuticals, brags on its website that the drug was approved very quickly, only 4 and a half years after the start of clinical trials.

The word proteasome refers to a protein complex present in all cells. In cellular metabolism, the ubiquitin-proteasome pathway is involved in degrading proteins in cell cycle contol and growth of tumors. The idea of proteasome inhibitors is to put a roadblock in this pathway and encourage the cells to die - a process called apoptosis.

Inhibitors are a unique class of anti-cancer drugs and they are under development, particularly for advanced cancer.