An adaptive prospective international multicentre platform clinical trial designed to evaluate the safety and efficacy of novel agents for the treatment of children, adolescents, and young adults (CAYA) with relapsed and/or refractory B-cell non-Hodgkin Lymphoma (r/r BNHL). The platform consists of three parallel treatment arms, each one investigating a different novel agent. The platform allows the testing of a pipeline of novel agents in each treatment arm consecutively.