Torin 1 is a potent inhibitor of mTORC1/2 with IC50 of 2 nM/10 nM in cell-free assays; exhibits 1000-fold selectivity for mTOR than PI3K.

In vitro: Torin1 inhibits phosphorylation of mTORC1 and mTORC2 substrates in cells at concentrations of 2 and 10 nM, respectively. Moreover, Torin1 exhibits 1000-fold selectivity for mTOR over PI3K (EC50 = 1800 nM) and exhibits 100-fold binding selectivity relative to 450 other protein kinases. Torin1 causes cell cycle arrest through a rapamycin-resistant mechanism that is also independent of mTORC2. Torin1 disrupts mTORC1-dependent phenotypes more completely than rapamycin. Rapamycin-resistant functions of mTORC1 are required for cap-dependent translation. In a recent study, it is reported Torin1 increases neurotensin secretion and gene expression through activation of the MEK/ERK/c-Jun pathway in the human endocrine cell line BON.

In vivo: Torin1 is efficacious at a dose of 20 mg/kg in a U87MG xenograft model and demonstrates good pharmacodynamic inhibition of downstream effectors of mTOR in tumor and peripheral tissues.

1. Guertin and Sabatini (2009) The pharmacology of mTOR inhibition. Sci.Signal. 2 pe24.

2. Thoreen et al (2009) An ATP-competitive mammalian target of rapamycin inhibitor reveals rapamycin-resistant functions of mTORC1. J.Biol.Chem. 284 8023.