A compound of Formula I, or a stereoisomer thereof, wherein X 1 is nitrogen; X 2 is nitrogen; m is 2; n is 1; o is 1; a is a single bond; b is a single bond; c is a double bond; R 1 is selected from the group consisting of hydrogen, methyl, and ethyl; R 2 is absent; R 3 is selected from the group consisting of isoxazolyl, pyrazolyl, oxazolyl, thiazolyl, imidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridinyl, pyrazinyl, pyridazinyl, pyrimidinyl, triazinyl, quinolinyl, isoquinolinyl, tetrahydroisoquinolinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, indazolyl, indolyl, 2-indolonyl, benzisoxazolyl, benzoisothiazolyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, furopyridinyl, oxazolopyridinyl, thienopyridinyl, thienopyrimidinyl, isothiazolopyridinyl, thiazolopyridinyl, thiazolopyridinonyl, thiazolopyrazinyl, thiazolopyrimidinyl, triazolopyridinyl, triazolopyrazinyl, imidazopyridinyl, pyrrolopyrimidinyl, pyrrolotriazinyl, 5,6-dihydrobenzo[h]quinazolinyl, 5H-chromeno[4,3-d]pyrimidinyl, 6,7-dihydro-5H-cyclopenta[d]pyrimidinyl, 5,6,7,8-tetrahydroquinazolinyl, 7,8-dihydroquinazolin-5 -onyl, and tetrahydrobenzothiazolyl, and is substituted with 0-3 substituents independently selected from the group consisting of C 1-4 alkyl, C 3-7 cycloalkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, C 3-7 cycloalkoxy, C 1-4 alkylthio, phenoxy, benzyloxy, halo, hydroxy, cyano, nitro, C 1-4 alkylsulfonyl, NR 4 R 5, pyrrolidinonyl, methylenedioxy, furyl, thienyl, pyrazolyl, imidazolyl, thiazolyl, triazolyl, pyrazinyl, pyrimidinyl, naphthyl, C 1-4 alkylamido, CONR 4 R 5, pyridyl, phenyl, and benzyl, and where imidazolyl, pyridyl, phenyl and benzyl are substituted with 0-2 substituents independently selected from the group consisting of halo, C 1-4 alkyl, C 1-4 alkoxy, C 1-4 haloalkyl, C 1-4 haloalkoxy, and NR 4 R 5; R 4 is hydrogen, C 1-4 alkyl, C 1-4 hydroxyalkyl, or C 1-4 aminoalkyl; and R 5 is hydrogen, C 1-4 alkyl, C 1-4 hydroxyalkyl, or C 1-4 aminoalkyl; or R 4 and R 5 taken together with the nitrogen atom to which they are attached is azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, N-(C 1-4 alkyl)piperazinyl, morpholinyl, or homopiperidinyl; or a pharmaceutically acceptable salt thereof. X 1 is nitrogen; X 2 is nitrogen; m is 2; n is 1; o is 1; a is a single bond; b is a single bond; c is a double bond; R 1 is selected from the group consisting of hydrogen, methyl, and ethyl; R 2 is absent; R 3 is selected from the group consisting of isoxazolyl, pyrazolyl, oxazolyl, thiazolyl, imidazolyl, oxadiazolyl, thiadiazolyl, triazolyl, pyridinyl, pyrazinyl, pyridazinyl, pyrimidinyl, triazinyl, quinolinyl, isoquinolinyl, tetrahydroisoquinolinyl, quinazolinyl, quinoxalinyl, naphthyridinyl, indazolyl, indolyl, 2-indolonyl, benzisoxazolyl, benzoisothiazolyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, furopyridinyl, oxazolopyridinyl, thienopyridinyl, thienopyrimidinyl, isothiazolopyridinyl, thiazolopyridinyl, thiazolopyridinonyl, thiazolopyrazinyl, thiazolopyrimidinyl, triazolopyridinyl, triazolopyrazinyl, imidazopyridinyl, pyrrolopyrimidinyl, pyrrolotriazinyl, 5,6-dihydrobenzo[h]quinazolinyl, 5H-chromeno[4,3-d]pyrimidinyl, 6,7-dihydro-5H-cyclopenta[d]pyrimidinyl, 5,6,7,8-tetrahydroquinazolinyl, 7,8-dihydroquinazolin-5 -onyl, and tetrahydrobenzothiazolyl, and is substituted with 0-3 substituents independently selected from the group consisting of C 1-4 alkyl, C 3-7 cycloalkyl, C 1-4 haloalkyl, C 1-4 alkoxy, C 1-4 haloalkoxy, C 3-7 cycloalkoxy, C 1-4 alkylthio, phenoxy, benzyloxy, halo, hydroxy, cyano, nitro, C 1-4 alkylsulfonyl, NR 4 R 5, pyrrolidinonyl, methylenedioxy, furyl, thienyl, pyrazolyl, imidazolyl, thiazolyl, triazolyl, pyrazinyl, pyrimidinyl, naphthyl, C 1-4 alkylamido, CONR 4 R 5, pyridyl, phenyl, and benzyl, and where imidazolyl, pyridyl, phenyl and benzyl are substituted with 0-2 substituents independently selected from the group consisting of halo, C 1-4 alkyl, C 1-4 alkoxy, C 1-4 haloalkyl, C 1-4 haloalkoxy, and NR 4 R 5; R 4 is hydrogen, C 1-4 alkyl, C 1-4 hydroxyalkyl, or C 1-4 aminoalkyl; and R 5 is hydrogen, C 1-4 alkyl, C 1-4 hydroxyalkyl, or C 1-4 aminoalkyl; or R 4 and R 5 taken together with the nitrogen atom to which they are attached is azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, N-(C 1-4 alkyl)piperazinyl, morpholinyl, or homopiperidinyl; or a pharmaceutically acceptable salt thereof.