Biological Activity
Torkinib (PP 242) is a selective and ATP-competitive mTOR inhibitor with an IC50 of 8 nM. PP242 inhibits both mTORC1 and mTORC2 with IC50s of 30 nM and 58 nM, respectively.
In Vitro
Torkinib (PP 242) potently inhibits mTOR (IC50=8 nM) but is much less active against other PI3K family members. Testing of Torkinib (PP 242) against 219 protein kinases reveals remarkable selectivity relative to the protein kinome: at a concentration 100-fold above its IC50 for mTOR, Torkinib (PP 242) inhibits only one kinase by more than 90% (Ret) and only three by more than 75% (PKCα, PKCβII and JAK2V617F)[1]. Torkinib (PP 242) has a dose-dependent effect on proliferation and at higher doses is much more effective than Rapamycin at blocking cell proliferation. The ability of Torkinib (PP 242) to block cell proliferation more efficiently than Rapamycin could be a result of its ability to inhibit mTORC1 and mTORC2, because Rapamycin can only inhibit mTORC1. In SIN1-/- mouse embryonic fibroblasts (MEFs), Rapamycin is also less effective at blocking cell proliferation than Torkinib. That Torkinib (PP 242) and Rapamycin exhibit very different anti-proliferative effects in SIN1-/- MEFs suggests that the two compounds differentially affect mTORC1[2].
In Vivo
In fat and liver, Torkinib (PP 242) is able to completely inhibit the phosphorylation of Akt at S473 and T308, consistent with its effect on these phosphorylation sites observed in cell culture. Surprisingly, Torkinib (PP 242) is only partially able to inhibit the phosphorylation of Akt in skeletal muscle and is more effective at inhibiting the phosphorylation of T308 than S473, despite it's ability to fully inhibit the phosphorylation of 4EBP1 and S6. These results will be confirmed by in vivo dose-response experiments, but, consistent with the partial effect of Torkinib (PP 242) on pAkt in skeletal muscle, a muscle-specific knockout of the integral mTORC2 component rictor resulted in only a partial loss of Akt phosphorylation at S473. These results suggest that a kinase other than mTOR, such as DNA-PK, may contribute to phosphorylation of Akt in muscle[2].
References & source
Published experimental findings depend on the model and assay conditions. They do not guarantee equivalent performance in every application. For laboratory research use only.
