Effect of mTORC1/mTORC2 inhibition on T cell function: potential role in graft-versus-host disease control

The mechanistic target of rapamycin (mTOR) pathway is crucial for the activation and function of T cells, which play an essential role in the development of graft-versus-host disease (GvHD). Despite its partial ability to block mTOR pathway, the mTORC1 inhibitor rapamycin has shown encouraging results in the control of GvHD. Therefore, we considered that simultaneous targeting of both mTORC1 and mTORC2 complexes could exert a more potent inhibition of T cell activation and, thus, could have utility in GvHD control. To assess this assumption, we have used the dual mTORC1/mTORC2 inhibitors CC214-1 and CC214-2. In vitro studies confirmed the superior ability of CC214-1 versus rapamycin to block mTORC1 and mTORC2 activity and to reduce T cell proliferation. Both drugs induced a similar decrease in Th1/Th2 cytokine secretion, but CC214-1 was more efficient in inhibiting naive T cell activation and the expression of T-cell activation markers. In addition, CC214-1 induced specific tolerance against alloantigens, while preserving anti-cytomegalovirus response. Finally, in a mouse model of GvHD, the administration of CC214-2 significantly improved mice survival and decreased GvHD-induced damages. In conclusion, the current study shows, for the first time, the immunosuppressive ability of CC214-1 on T lymphocytes and illustrates the role of CC214-2 in the allogeneic transplantation setting as a possible GvHD prophylaxis agent.