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BACKGROUND AIMS: Chimeric antigen receptor (CAR) T-cell products are commonly generated using lentiviral vector (LV) transduction. Optimal final formulation buffer (FFB) supporting LV stability during cryostorage is crucial for cost-effective manufacturing. METHODS: To identify the ideal LV FFB composition for ex vivo CAR-T production, primary human T cells were transduced with vesicular stomatitis virus G-protein (VSV-G) -pseudotyped LVs (encoding a reporter gene or an anti-CD19-CAR). The formulations included phosphate-buffered saline (PBS), HEPES, or X-VIVOTM 15, and stabilizing excipients. The functional and viral particle titers and vector copy number were measured after LV cryopreservation and up to 24 h post-thaw incubation. CAR-Ts were produced with LVs in selected FFBs, and the resulting cells were characterized. RESULTS: Post-cryopreservation, HEPES-based FFBs provided higher LV functional titers than PBS and X-VIVOTM 15, and 10% trehalose-20 mM MgCl2 improved LV transduction efficiency in PBS and 50 mM HEPES. Thawed vectors remained stable at +4°C, while a ≤ 25% median decrease in the functional titer occurred during 24 h at room temperature. Tested excipients did not enhance LV post-thaw stability. CAR-Ts produced using LVs cryopreserved in 10% trehalose- or sucrose-20 mM MgCl2 in 50 mM HEPES showed comparable transduction rates, cell yield, viability, phenotype, and in vitro functionality. CONCLUSION: A buffer consisting of 10% trehalose-20 mM MgCl2 in 50 mM HEPES provided a feasible FFB to cryopreserve a VSV-G -pseudotyped LV for CAR-T-cell production. The LVs remained relatively stable for at least 24 h post-thaw, even at ambient temperatures. This study provides insights into process development, showing LV formulation data generated using the relevant target cell type for CAR-T-cell manufacturing.
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BACKGROUND: Adoptive T-cell therapy offers new options for cancer treatment. Clinical results suggest that T-cell persistence, depending on T-cell memory, improves efficacy. The use of interleukin (IL)-2 for in vitro T-cell expansion is not straightforward because it drives effector T-cell differentiation but does not promote the formation of T-cell memory. We have developed a cost-effective expansion protocol for chimeric antigen receptor (CAR) T cells with an early memory phenotype. METHODS: Lymphocytes were transduced with third-generation lentiviral vectors and expanded using CD3/CD28 microbeads. The effects of altering the IL-2 supplementation (0-300 IU/mL) and length of expansion (10-20 days) on the phenotype of the T-cell products were analyzed. RESULTS: High IL-2 levels led to a decrease in overall generation of early memory T cells by both decreasing central memory T cells and augmenting effectors. T memory stem cells (TSCM, CD95+CD45RO-CD45RA+CD27+) were present variably during T-cell expansion. However, their presence was not IL-2 dependent but was linked to expansion kinetics. CD19-CAR T cells generated in these conditions displayed in vitro antileukemic activity. In summary, production of CAR T cells without any cytokine supplementation yielded the highest proportion of early memory T cells, provided a 10-fold cell expansion and the cells were functionally potent. DISCUSSION: The number of early memory T cells in a T-cell preparation can be increased by simply reducing the amount of IL-2 and limiting the length of T-cell expansion, providing cells with potentially higher in vivo performance. These findings are significant for robust and cost-effective T-cell manufacturing.