The present invention relates to compounds of formula I: and pharmaceutically acceptable salts thereof, wherein R1, R2, R3, R4, R5, R6 and R7 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化合物,及其醫藥上可接受之鹽,其中R1、R2、R3、R4、R5、R6及R7係如本文中所定義。本發明亦係關於包含該等化合物之醫藥組合物、使用該等化合物治療各種疾病及病症之方法、製備該等化合物之方法及可用於該等方法中之中間體。