Everolimus in combination with vandetanib in children, adolescents, and young adults: a phase I study

Background: Combined use of inhibitors of mammalian target of rapamycin (mTOR) and vascular endothelial growth factor (VEGF-2) receptors is a potential strategy to overcome resistance to either class of drugs when used alone. Patients and methods: We designed a phase 1 trial to test the drug combination of a multikinase VEGF receptor 2 inhibitor, vandetanib, and an mTOR inhibitor, everolimus, in a pediatric and young adult patient cohort with advanced cancers. Exceptional responders were probed for tumor mutational profile to explore possible molecular mechanisms of response. Results: Among 21 enrolled patients, clinical benefit was observed in 38% (one patient with partial response and eight patients with stable disease) with a median progression-free survival of 3.3 months. The most common treatment-related adverse event was rash (n = 13). Other treatment-related toxicities included diarrhea, fatigue, hypertension, QT prolongation, hypertriglyceridemia/hypercholesterolemia, transaminitis, thrombocytopenia, and weight loss. None of the patients experienced dose-limiting toxicities. Three exceptional responders were analyzed and were found to harbor genetic alterations including kinase insert domain receptor (KDR) Q472H mutation, EWSR1-CREB3L1, CDKN2A/B loss, and ASPL/ASPSCR1-TFE3 fusion. Conclusions: The combination of vandetanib and everolimus showed early activity and tolerable toxicity profile in pediatric patients with advanced cancers.