Initial testing of the multitargeted kinase inhibitor pazopanib by the Pediatric Preclinical Testing Program.

Pazopanib is an oral angiogenesis inhibitor targeting vascular growth factor receptor-1, -2, and -3, platelet derived growth factor receptor-α, platelet derived growth factor receptor-β, and KIT that has demonstrated activity against a variety of adult cancer xenografts. Pazopanib was tested against a panel of pediatric rhabdomyosarcoma and Ewing sarcoma xenografts at a dose of 108 mg/kg/day or 100 mg/kg twice daily, administered orally for 28 days. While no objective responses were observed, pazopanib induced statistically significant differences in event-free survival compared to controls in approximately one-half of the sarcoma xenograft models tested. Though well tolerated, pazopanib showed limited activity against the sarcoma models evaluated, with the best tumor responses being growth delay.