Autologous T-cell therapies against cancer face disadvantages in terms of production cost, logistics, and compromised T-cell fitness. The use of allogeneic T cells can partially bypass these limitations, but it brings new challenges involving host-versus-graft (HvG) and graft-versus-host (GvH) reactions. Our aim is to develop a strategy to bypass these two obstacles by leveraging on the substantial flexibility of mRNA electroporation technology in engineering allogeneic mRNA TCR-T cells.
Instead of reducing allogeneic T cell immunogenicity through irreversible genetic approaches, we propose to prevent HvG reactions by transiently suppressing the host's immune system with a finite treatment of immunosuppression (tacrolimus). At the same time, the functionality of these allogeneic T cells will be preserved through the conferment of transient tacrolimus resistance by introducing a modified version of calcineurin B into the T cells through mRNA electroporation. Moreover, to minimize the risk of GvH disease, we propose to utilize different cytokine cocktails to expand T cells to produce TCR-T cell products with inherently reduced GvH potential.
Our in vitro data showed that tacrolimus can effectively suppress the HvG reactions with minimal impact on the functionality of the tacrolimus-resistant engineered allogeneic TCR-T cells. We also showed that expanding T cells with the addition of IL-4 and IL-7 resulted in allogeneic TCR-T cells with significantly lower GvH potential than conventional IL-2 expanded TCR-T cells, while maintaining both tumoricidal efficacy and electroporation efficiency. Transcriptomic and secretomic analysis of the new allogeneic TCR-T product also revealed that TCR-T cells expanded with the IL-2/4/7 cocktail, compared to the IL-2 expanded product, is less pro-inflammatory and less reactive to non-TCR mediated stimuli such as cytokines.
Taken together, our in vitro results showed that mRNA electroporation and T cell expansion procedures can be utilized in combination to develop a safe and effective ‘off-the-shelf’ allogeneic TCR-T cell therapy product.