Discovery of 7-Methyl-5- (1-3- (trifluoromethyl) phenylacetyl-2, 3-dihydro-1H-indol-5-yl) -7H-pyrrolo2, 3-dpyrimidin-4-amine (GSK2606414), a Potent and Selective First-in-Class Inhibitor of Protein Kinase R (PKR) -like Endoplasmic Reticulum Kinase (PERK) | Synapse