RecruitingDrug trialEuropean Proof-of-Concept Therapeutic Stratification Trial of Molecular Anomalies in Relapsed or Refractory TumorsThis proof-of-concept platform trial is designed to cover the targeting of several survival pathways in oncogenesis that are currently not adequately employed for pediatric patients in Europe (Geoerger 2017; Geoerger 2019). The aims of the trial are: 1. To determine the recommended phase II dose (RP2D) of a specific anticancer agent and/or a relevant combination in a pediatric population, to document its tolerability and 2. To explore first signals of activity in a molecularly enriched study population.