(R)-N-(1-(3-(8-Methyl-5-(methylamino)-8H-imidazo[4,5-d]thiazolo[5,4-b]pyridin-2-yl)phenyl)ethy

Tyk2-IN-3 is a Tyk2 pseudokinase inhibitor, with an IC50 of 485 nM.

Tyk2-IN-3 (compound 1) is very potent against the Tyk2 pseudokinase (99% inhibition at 1 μM) but lacks potency against all other kinases in the kinome assay panel except IKK (96% inhibition) and the JAK1 pseudokinase domain (99% inhibition at 1 μM). No evidence of binding to the catalytic domain of Tyk2 or any other JAK family kinase is evident at 1 μM, and subsequent enzymatic assays confirm the lack of activity against purified catalytic domains (IC50>>2 μM). The pseudokinase domains of JAK2 and JAK3 are not part of the kinome screening panel. In the IL-23-stimulated kit225 T cell assay, Tyk2-IN-3 inhibits the stimulated response with an IC50 of 485±143 nM (n=3)[1].

[1]. Tokarski JS, et al. Tyrosine Kinase 2-mediated Signal Transduction in T Lymphocytes Is Blocked by Pharmacological Stabilization of Its Pseudokinase Domain. J Biol Chem. 2015 Apr 24;290(17):11061-74.