Metformin is an oral anti-diabetes medication that activates AMP-activated protein kinase (AMPK). Recent data from in vitro and in vivo experiments, as well as epidemiologic retrospective analyses, suggest that metformin has anti-cancer activity. Vincristine, irinotecan, and temozolomide (VIT) is a combination of chemotherapeutic agents that have different mechanisms of action as well as disparate side effect profiles. Two recent phase 1 trials have demonstrated that this regimen is safe and well-tolerated in children with relapsed and refractory solid tumors.