VLX1570 (CAS: 1431280-51-1) is a competitive inhibitor of proteasome DUB activity with IC50 ranging from 4.2 uM to 8.6 uM. VLX1570 specifically binds to both USP14 and UCHL5, thereby blocking their deubiquitylating activity. This blocks the ubiquitin proteasome degradation pathway, prevents the degradation of defective proteins, and leads to an accumulation of poly-ubiquitylated proteins. This induces the unfolded protein response (UPR) and results in both the induction of tumor cell apoptosis and the inhibition of tumor cell growth.