A novel multicolor fluorescent spot assay for the functional assessment of chimeric antigen receptor (CAR) T-cell products

Background aims: Chimeric antigen receptor (CAR) T-cell (CAR-T) therapies have revolutionized the treatment of B-cell lymphomas. Unfortunately, relapses after CD19-targeted CAR-T are relatively common and, therefore, there is a critical need for assays able to assess the function and potency of CAR-T products preinfusion, which will hopefully help to optimize CAR-T therapies. We developed a novel multicolor fluorescent spot assay (MFSA) for the functional assessment of CAR-T products on a single-cell level, combining the numerical assessment of CAR-T products with their functional characterization. Methods: We first used a standard single-cell interferon (IFN)-g enzyme-linked immune absorbent spot assay to measure CD19-targeted CAR-T responses to CD19-coated beads. We then developed, optimized and validated an MFSA that simultaneously measures the secretion of combinations of different cytokines on a single CAR-T level. Results: We identified IFN-g/tumor necrosis factor-a/granzyme B as the most relevant cytokine combination, and we used our novel MFSA to functionally and numerically characterize two clinical-grade CAR-T products. Conclusions: In conclusion, we have developed a novel assay for the quantitative and functional potency assessment of CAR-T products. Our optimized MFSA is cost-effective, easy to perform, reliable, can be performed overnight, allowing for a fast delivery of the product to the patient, and requires relatively minimal maintenance and training. The clinical value of our novel assay will be assessed in studies correlating the pre-infusion assessment of CAR-T products with the patients' outcome in a prospective fashion. (c) 2024 International Society for Cell & Gene Therapy. Published by Elsevier Inc. All rights reserved.