The present invention provides compounds of the formula: ##STR00001## and pharmaceutically acceptable isomers, salts, hydrates, solvates, and prodrug derivatives thereof, wherein R.sup.1, R.sup.6, R.sup.7, R.sup.8, Pg, and n are those defined herein. The present invention also provides pharmaceutical compositions comprising the same and methods for using the same. In particular, compounds of Formula I are useful in modulating TGF-.beta. activity.