1. A compound of the formula:
or a pharmaceutically acceptable salt thereof, in which:
A, along with X and the carbon atom to which it is attached, forms a (C6-C10)aryl or a 5- to 10-membered heteroaryl moiety, in which said aryl or heteroaryl moiety is optionally substituted with up
to 4 substituents, each independently selected from the group consisting of C3-C6 cycloalkyl, oxo, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 alkoxy, hydroxy, cyano, halo, NR5R6, C(O)NR5R6, NHC(O)R5, C(O)OR5, (C1-C6)alkyl-(C3-C6)cycloalkyl, a 4- to 6-membered heterocyclic moiety, phenyl, and benzyl;
X is represented by N or C, and
R5 and R6 are each optionally and independently represented by hydrogen or C1-C6 alkyl.