ACY-1215 is an inhibitor of histone deacetylase 6 (HDAC6; IC50 = 5 nM). It is at least 10-fold less active against other HDACs in enzymatic assays. ACY-1215 shows synergistic activity with the proteasome inhibitor bortezomib against multiple myeloma (MM) cells, inducing protracted endoplasmic reticulum stress and apoptosis. ACY-1215 combined with proteasome inhibitors suppresses tumor growth and increases survival in mice with MM and mantle cell lymphoma xenografts. A multicenter phase I trial examining ACY-1215 combined with the E3 ligase inhibitor lenalidomide and dexamethasone in multiple myeloma found inhibition of HDAC6 in vivo. ACY-1215 also diminishes liver cyst development and fibrosis in a rat model of polycystic liver disease.
