RecruitingDrug trialHEM iSMART-D: Trametinib + Dexamethasone + Chemotherapy in Children With Relapsed or Refractory Hematological MalignanciesHEM-iSMART is a master protocol which investigates multiple investigational medicinal products in children, adolescents and young adults (AYA) with relapsed/refractory (R/R) ALL and LBL. Sub-protocol D is a phase I/II trial evaluating the safety and efficacy of trametinib in combination with dexamethasone, cyclophosphamide and cytarabine in children and AYA with R/R ped ALL/LBL whose tumor present with alterations in the RAS-RAF-MAPK pathway.