Evaluation of arsenic trioxide by the pediatric preclinical testing program with a focus on Ewing sarcoma.

Arsenic trioxide was tested against the PPTP in vitro panel (1.0 nM to 10 µM) and against the PPTP Ewing sarcoma in vivo panel administered intraperitoneally at a dose of 2.5 mg/kg daily × 5 per week for a planned treatment duration of 3 weeks. Arsenic trioxide showed a median relative IC(50) value of 0.9 µM, with Ewing sarcoma cell lines having IC(50) values similar to those of the remaining PPTP cell lines. Arsenic trioxide did not induce significant differences in EFS distribution compared to control in any of the Ewing sarcoma xenografts studied, and no objective responses were observed.