Targeting of PI3K/AKT/mTOR pathway to inhibit T cell activation and prevent graft-versus-host disease development


Graft-versus-host disease (GvHD) remains the major obstacle to successful allogeneic hematopoietic stem cell transplantation, despite of the immunosuppressive regimens administered to control T cell alloreactivity. PI3K/AKT/mTOR pathway is crucial in T cell activation and function and, therefore, represents an attractive therapeutic target to prevent GvHD development. Recently, numerous PI3K inhibitors have been developed for cancer therapy. However, few studies have explored their immunosuppressive effect.


The effects of a selective PI3K inhibitor (BKM120) and a dual PI3K/mTOR inhibitor (BEZ235) on human T cell proliferation, expression of activation-related molecules, and phosphorylation of PI3K/AKT/mTOR pathway proteins were analyzed. Besides, the ability of BEZ235 to prevent GvHD development in mice was evaluated.


Simultaneous inhibition of PI3K and mTOR was efficient at lower concentrations than PI3K specific targeting. Importantly, BEZ235 prevented naïve T cell activation and induced tolerance of alloreactive T cells, while maintaining an adequate response against cytomegalovirus, more efficiently than BKM120. Finally, BEZ235 treatment significantly improved the survival and decreased the GvHD development in mice.


These results support the use of PI3K inhibitors to control T cell responses and show the potential utility of the dual PI3K/mTOR inhibitor BEZ235 in GvHD prophylaxis.

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S2247 Buparlisib (BKM120, NVP-BKM120) Buparlisib (BKM120, NVP-BKM120) is a selective PI3K inhibitor of p110α/β/δ/γ with IC50 of 52 nM/166 nM/116 nM/262 nM in cell-free assays, respectively. Reduced potency against VPS34, mTOR, DNAPK, with little activity to PI4Kβ. Phase 2. (137) (6)

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