Immunomodulatory strategies for ex vivo immune cell expansion in adoptive cell therapy: translational and regulatory considerations for clinical manufacturing

Ex vivo expansion is a fundamental yet challenging step in the manufacturing of adoptive cell therapies (ACT), as therapeutic success relies on generating enough functional immune cells while maintaining their phenotype, metabolic fitness, and persistence. This review provides a comprehensive overview of immunomodulatory strategies designed to enhance cell yield during ex vivo expansion, categorizing them into cell-intrinsic and cell-extrinsic approaches. Cell-intrinsic strategies, including gene editing and gene transfer technologies, enable precise modulation of survival pathways, proliferation, metabolic state, and resistance to exhaustion. These tools support the production of more potent and durable immune cell products. In contrast, cell-extrinsic strategies shape immune cell behavior through cytokine supplementation, checkpoint blockade, nutrient and metabolic modulation, feeder cell systems, synthetic activation platforms, and biophysical cues such as oxygen tension and bioreactor-controlled environments. Together, these strategies provide coordinated signals that direct activation, differentiation, and persistence during expansion in culture. The review also highlights key regulatory considerations, including distinctions between genetically and non-genetically modified products, risk assessments associated with human and animal-derived materials, ancillary material qualification, and process scalability for clinical translation. By integrating biological, engineering, and regulatory perspectives, this paper outlines principles for scalable immunomodulation platforms designed with regulatory considerations in mind to advance next-generation ACT manufacturing.