Phase I clinical trial - Pédiatrie Tumeurs cérébrales

This study consists of 2 parts: Dose Escalation Part 1 and Dose Expansion Part 2. The Dose Escalation Part 1 will evaluate the safety and tolerability of Avelumab in combination with Lenvatinib and determine the recommended Avelumab and Lenvatinib dose for expansion. Dose Expansion Part 2 will assess the efficacy of Avelumab in combination with Lenvatinib by Progression-free Survival in participants with pre-defined primary central nervous system (CNS) tumors.