Compounds having the following formula I:or a stereoisomer or pharmaceutically-acceptable salt thereof, where all substituents are as defined herein, are useful in the modulation of IL-12, IL-23 and/or IFNα, by acting on Tyk-2 to cause signal transduction inhibition.本發明係關於具有以下式I之化合物:或其立體異構體或醫藥學上可接受之鹽,其中所有取代基如本文所定義,其係適用於藉由作用於Tyk-2以抑制信號轉導來調節IL-12、IL-23及/或IFNα。