Inhibitor of two 19S regulatory-particle–associated deubiquitinases (DUBs), ubiquitin C-terminal hydrolase 5 (UCHL5) and ubiquitin-specific peptidase 14 (USP14) showing tumor growth inhibition in vivo. NSC 687852 shows IC50 values of 0.5 μM and 2.1 μM in cathepsin-dependent caspase-cleavage and in purified 19S proteasome Ub-AMC cleavage assays, respectively. NSC 687852 induced tumor cell apoptosis that was insensitive to TP53 status and overexpression of the apoptosis inhibitor BCL2. NSC 687852 does not inhibit the non proteasomeal DUBs UCHL-1/3, USP-2/7/8 and BAP1.