The present invention relates to compounds of formula (I):or pharmaceutically acceptable salts thereof, wherein R1, R2, X, Y, and HET are as defined herein. The invention also relates to pharmaceutical compositions comprising these compounds, methods of using these compounds in the treatment of various diseases and disorders, processes for preparing these compounds and intermediates useful in these processes.本發明係關於式(I)之化合物,或其醫藥學上可接受之鹽,其中R1、R2、X、Y及HET如本文所定義。本發明亦關於包含此等化合物之醫藥組合物、將此等化合物用於治療各種疾病及病症之方法、製備適用於此等方法之此等化合物及中間物的方法。