RecruitingDrug trialHEM-iSMART-C: Ruxolitinib + Venetoclax + Dexamethasone + Cyclophosphamide and Cytarabine in Pediatric Patients 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 C is a phase I/II trial evaluating the safety and efficacy of ruxolitinib and venetoclax in combination with dexamethasone, cyclophosphamide and cytarabine in children and AYA with R/R ped ALL/LBL whose tumor present with alterations in the IL7R/JAK-STAT pathway.