USP7 and plasma cell myeloma: As disclosed in US 20160090351, P5091 displays a preference for USPs (Hedstrom et al., 2016) and another study (Pal et al., 2014) demonstrated that P5091 is a novel small-molecule inhibitor targeting USP7 and USP47, as well as functions as an active anticancer agent in various tumor models, including MM.1S multiple myeloma cells and HCT-116 colon cancer cells (Chauhan et al., 2012; Pal et al., 2014).