The present application describes compounds according to Formula I, pharmaceutical
compositions comprising at least one compound according to Formula I and optionally
one or more additional therapeutic agents and methods of treatment using the compounds
according to Formula I both alone and in combination with one or more additional
therapeutic agents. The compounds have the general Formula I
##STR1##
including all prodrugs, pharmaceutically acceptable salts and stereoisomers,
R1, R2, R3, and R4 are described herein.