Rocilinostat

Rocilinostat (ACY-1215) is a selective HDAC6 inhibitor with IC50 of 5 nM in a cell-free assay. It is >10-fold more selective for HDAC6 than HDAC1/2/3 (class I HDACs) with slight activity against HDAC8, minimal activity against HDAC4/5/7/9/11, Sirtuin1, and Sirtuin2. Phase 2. (In Vitro) :Ricolinostat (ACY-1215) has slight activity against HDAC8 (IC50=0.1 μM), and has minimal activity (IC50>1 μM) against HDAC4, HDAC5, HDAC7, HDAC9, HDAC11, Sirtuin1, and Sirtuin2. The effect of Ricolinostat (ACY-1215) on multiple myeloma (MM) cell viability is determined with MTT assays using MM cell lines. Exposure of MM cell lines for 48 hours results in dose-dependent decreased viability, with IC50 values ranging from 2-8μM. Ricolinostat (ACY-1215) demonstrates significant activity in the MM PS-341-resistant cell line (ANBL-6.BR), demonstrating the ability of Ricolinostat (ACY-1215) to overcome PS-341 resistance. (In Vivo) :Mice treated with Ricolinostat (ACY-1215), PS-341, or Ricolinostat plus PS-341 show a significant delay in tumor growth (P=0.01, P=0.006, and P<0.0001, respectively) . Combined treatment with Ricolinostat and PS-341 shows significant suppression of tumor growth and significantly prolonged overall survival (OS) compare with the control group (17 days in the control vs 40 days in the combination-treated group, P<0.0001) and the Ricolinostat (ACY-1215) -treated group (22 days in the PS-341 group vs 40 days in the combination-treated group, P<0.0001) . Weight loss in the combination-treated group is between 4% and 12% compare with the same-day control group values during treatment, with complete recovery after the last injection. As is observed in the plasmacytoma model, a significant therapeutic advantage is found by combining Ricolinostat with PS-341 compare with either agent alone.