Enhanced activity of ABT-737 combined to bortezomib in a xenograft SCID-beige mouse model of MCL (HBL-2). The combination of intraperitoneal ABT-737 (A) at 75 mg/kg per day for 10 days plus intraperitoneal bortezomib (B) at 0.5 mg/kg on day 1 and 0.75 mg/kg on days 5 and 10 has shown the best activity, with 2 complete responses from day 8. (B) A multiple comparison analysis of the average AUCs (left panel) at day 52, showed statistical significant tumor shrinkage (starting from day 41) for the combination of ABT-737 plus bortezomib (0.5 mg/kg on day 1 and 0.75 mg/kg on days 5 and 10) compared to the single drugs and the control (right panel, P values for all comparisons are provided, P < .018, in bold). All significance testing is done at the P < .05 level.