Abstract: A compound of formula I, or a stereoisomer, tautomer, or pharmaceutically acceptable salt thereof: wherein X1 is benzimidazolyl, substituted benzimidazolyl, azabenzimidazolyl, substituted azabenzimidazolyl, pyrazolyl, or substituted pyrazolyl; X2 is aryl, substituted aryl, arylalkyl, substituted arylalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, substituted heteroarylalkyl, cycloalkyl, substituted cycloalkyl, (cycloalkyl)alkyl, substituted (cycloalkyl)alkyl, heterocycloalkyl, substituted heterocycloalkyl, (heterocycloalkyl)alkyl, substituted (heterocycloalkyl)alkyl, alkyl, substituted alkyl, alkoxycarbonyl, substituted alkoxycarbonyl, dialkylaminocarbonyl, substituted dialkylaminocarbonyl, (heterocycloalkyl)carbonyl, or substituted (heterocycloalkyl)carbonyl; X3 is alkyl, substituted alkyl, alkenyl, substituted alkenyl, heterocycloalkyl, substituted heterocycloalkyl, (heterocycloalkyl)alkyl, substituted (heterocycloalkyl)alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, heter