ACY-1215 in combination with bortezomib induces significant anti-MM activity in vivo. (A) CB17 SCID mice were treated with saline (n = 7), ACY-1215 (50 mg/kg n = 7), bortezomib (0.5 mg/kg, n = 6), or the combination of ACY-1215 plus bortezomib (n = 7) for 3 weeks. Tumor growth was significantly inhibited in the combination-treated group compared with controls (P < .0001). (B) Using Kaplan-Meier and log-rank analysis, the median OS of animals treated with combination therapy was significantly prolonged (22 days in the control group vs 34 days in the treated group, P < .0011). WB analysis of tumors taken from mice after 3 days of treatment showed a significant accumulation of polyubiquitinated proteins in the group treated with the combination of ACY-1215 plus bortezomib compared with either agent alone (bottom panel). (C) Treatment with ACY-1215 or ACY-1215 plus bortezomib did not significantly affect the body weight of the animals. (D) SCID-beige mice were inoculated intravenously with MM.1S-LucNeo cells and then treated with saline (n = 10), ACY-1215 (n = 10), bortezomib (n = 10), or the combination of ACY-1215 plus bortezomib (n = 10) for 2 weeks. Combined treatment with ACY-1215 and bortezomib induced significant suppression of tumor growth, as demonstrated by bioluminescence imaging (log scale). (E) Treatment with ACY-1215 and ACY-1215 plus bortezomib induces between 4% and 12% of body weight loss. (F) Combined treatment with ACY-1215 and bortezomib significantly prolonged survival (17 days in the control group vs 40 days in the combination-treated group, P < .0001).