EIF2AK3 and exocrine pancreatic insufficiency: Our previous results using the PERK kinase inhibitor, GSK2606414, similarly led to weight loss after chronic treatment in prion-diseased mice.10 PERK−/−-knockout mice show early postnatal lethality and exocrine pancreatic insufficiency,20 and it is predictable that the pancreas is vulnerable to PERK inhibition.