Academic CAR T-cell manufacturing is rapidly expanding across Europe, but cryopreservation practices remain heterogeneous, raising concerns about product comparability. While cryopreservation is essential for later infusion, storage of surplus cells, or treatment postponement, no specific harmonized guidelines exist for CAR T-cell products. An EBMT survey (52 academic centers) revealed wide variability in freezing timing, cryomedium composition, device choice, storage temperatures, and post-thaw quality control. To address these gaps, EBMT organized a workshop using its harmonisation methodology. A panel of experts reviewed survey data, literature, and professional experience to draft consensus recommendations. Key recommendations include: performing cryopreservation as soon as possible after manufacturing (preferably ≤48 h), initiating freezing within 30 min of cryomedium addition, and using controlled-rate freezing to at least −80 °C, with long-term storage below −120 °C whenever feasible. Retention samples, post-thaw viability, identity testing, and validated transportation procedures are considered mandatory. Liquid nitrogen and Peltier-based controlled-rate freezing systems were regarded as technically equivalent, while −80 °C passive freezing has been used successfully and may serve as a back-up method, local confirmation of suitability in a formal method validation provided. These consensus-based recommendations seek to establish technical recommendations for CAR-T cryopreservation for groups currently establishing academic manufacturing of CAR-T products.
