The LIT – Leibniz Institute for Immunotherapy (foundation under civil law) is a research institute dedicated to the development of novel, curative immunotherapies for the treatment of cancer, chronic inflammation, and autoimmune disease. Within the scope of its international activities, the LIT is coordinating a European collaborative project, T-FITNESS, which is embedded in Europe’s Horizon EIC Pathfinder challenge “Emerging technologies in cell and gene therapy”. The aim of this project is to develop a groundbreaking technology based on microRNA-based logic circuits to enable CAR T cells to become refractory to functional exhaustion once they reach the tumor sites.