Computational design of optimized and preferentially paired human TCR constant regions for improved T-cell function
2Department of Biomolecular Sciences, Weizmann Institute of Science
Adoptive Cell Transfer (ACT) utilizes peripheral blood mononuclear cells (PBMCs) obtained from patients. Through a transduction process, we endow the cells with specific, previously identified TCRs, providing the T-cells the ability to recognize the cancer cells. However, several factors limit the effectiveness of this approach.
The solutions for overcoming the technical obstacles of introducing exogenous TCRs to cells that already express an endogenous TCR are either aimed at removing the endogenous TCRs, modifying the exogenous TCRs, or a combination of the two. Some of these techniques, however, are not currently viable in clinical settings, produce only a minor benefit, or are restricted to a single TCR. Our goal was to increase the anti-cancer function of T-cells by increasing the stability of the constant region of the TCR and generating improved versions of several widely used TCRs. Using our modified TCRs in therapeutic settings will not require changing the well-established protocols currently in use.
Stabilization of the TCR was achieved by modifying selected amino acids in the constant region. Our method combines previously described modifications with an evolution-guided atomistic design to improve protein stability. Many designs were tested in vitro and ranked based on their cytokine secretion.
The combination of several known and novel approaches resulted in an increased exogenous TCR expression, which is directly correlated to an increase in function and expression of activation-associated differentiation clusters CD137, CD69, and CD25. Additionally, we have noted a substantial increase in cytokine secretion, ranging from a three-fold increase to a sixteen-fold increase, depending on the TCR and the targeted cell line, as well as enhanced killing of cancer cells.
Overall, these findings provide the basis for a more rational design of improved TCR constant regions that enable the enhancement of TCR-gene transfer-based treatments. These mutations can be applied to a plethora of TCRs that target various cancer and viral antigens.