P22077 is a potent and selective USP7 inhibitor that was recently identified using an Ub-CHOP reporter assay. It was shown to have potent and selective inhibitory activity against USP7 and closely related USP47 at ~5 μM, but not other DUBs (at ~15-45 μM). USP7, also known as HAUSP, plays an important role in cancer progression as it affects the stability of p53. The inhibition of USP7 is predicted to destabilize HDM2 and stabilize p53, and USP7 exerts both p53-dependent and p53-independent effects on controlling cell proliferation and apoptosis.