The present invention provides a compound of Formula (I) or a salt thereof; and therapeutic uses of these compounds. The present invention further provides pharmaceutical compositions comprising these compounds, and compositions comprising these compounds with a therapeutic co-agent.本發明提供一種式(I)化合物或其鹽;及此等化合物之治療用途。本發明進一步提供包含此等化合物之醫藥組合物,及包含此等化合物及治療輔劑之組合物。