Fig. 1.

The overview of UPS and inhibitors in clinical trials to target UPS. UPS is representative process for protein degradation consisting of ubiquitinating enzyms (E1, 32, and E3), 26S proteasome, and deubiquitinating enzymes. A number of small molecule inhibitors targeting the components of UPS are developed for cancer therapeutics. P phase, *phase completed, #FDA approved but under phase I–IV for another indication