Chimeric antigen receptor (CAR)-T cells represent a recent clinically validated modality in cancer therapy and beyond. However, broad industrial implementation faces technological, logistical, regulatory and financial challenges. A major bottleneck is the ex vivo production process, where cytokines are essential and product-determining constituents. To better understand the complexity of cytokine utilization throughout the production process, we rigorously reviewed the existing literature, including extended manufacturing parameters from 292 available clinical reports. We found a progressive reduction of interleukin-2 exposure, driven by its association with unfavourable cell characteristics. Preclinically, this catalysed the evaluation of alternative cytokines with potential to preserve naive phenotypes, support cell expansion and enhance the efficacy of CAR-T cells. Here we illustrate the evolving use of cytokines, reveal non-standardized clinical CAR-T cell manufacturing parameters, and summarize preclinical and next-generation concepts, which may improve manufacturing efficiency, cost-effectiveness and therapeutic outcomes. Our observations may further guide the development of cytokine-armouring strategies to promote in-patient expansion and persistence, even as innovations such as shortened manufacturing and in vivo engineering techniques could reduce reliance on cytokines during ex vivo culture.

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Guaza-Lasheras, M., Nimmerfroh, J., Schwarz, D., de Grujil, T. D., Hartmann, J., Klein, C., Läubli, H., Lotem, M., Mittelstaet, J., Paget, C., Hadrup, S. R., Schallenberg, S., Thor Straten, P., Theurich, S., Venetz, D., Zippelius, A., Zitvogel, L., & Kobold, S. (2026). The evolving role of cytokines for CAR-T cell manufacturing and beyond. Nature Biomedical Engineering. doi:10.1038/s41551-026-01703-w