[CAS NO. 1255517-76-0]  PF-4708671

PF-4708671 is a piperazinyl-pyrimidine analogue and the first S6K1-specific inhibitor. PF-4708671 does not significantly inhibit the activity of the closely related S6K2 isoform or a number of other AGC kinases (Akt1, Akt2, PKA, PKCα, PKCϵ, PRK2, ROCK2, RSK1, RSK2 or SGK1) . PF-4708671 prevents the S6K1-mediated phosphorylation of S6 protein in response to IGF-1 (insulin-like growth factor 1), while having no effect upon the PMA-induced phosphorylation of substrates of the highly related RSK (p90 ribosomal S6 kinase) and MSK (mitogen- and stress-activated kinase) kinases. PF-4708671 is also found to induce phosphorylation of the T-loop and hydrophobic motif of S6K1, an effect that is dependent upon mTORC1 (mTOR complex 1). PF-4708671 does not affect activity of mTORC1.