GDF-8 inhibitors

A compound of the formula

• or a pharmaceutically acceptable salt thereof, wherein
• X is N;
• R1 is halogen, cyano, nitro, C1-6alkyl, C1-6haloalkyl, C3-8cycloalkyl, C3-8cycloalkenyl, heterocyclyl, aryl, heteroaryl, —R10, or —C1-6alkyl-R10, wherein
• R10 is —OR, —SR, —NRaRa, —C(O)R, —C(O)OR, —C(O)NRaRa, —S(O)2NRaRa, —OC(O)R, —N(R)C(O)R, —OC(O)OR, —O(CH2)mC(O)NRaRa, —N(R)C(O)OR, —N(R)C(O)NRaRa, —N(R)S(O)2NRaRa or —N(R)S(O)2R;
• R2 is hydrogen, halogen, cyano, nitro, C1-6alkyl, C1-6haloalkyl, C3-8cycloalkyl, C3-8cycloalkenyl, heterocyclyl, aryl, heteroaryl, —R10, or —C1-6alkyl-R10, wherein R10 is —OR, —SR, —NRaRa, —C(O)R, —C(O)OR, —C(O)NRaRa, —S(O)2NRaRa, —OC(O)R, —N(R)C(O)R, —OC(O)OR, —O(CH2)mC(O)NRaRa, —N(R)C(O)OR, —N(R)C(O)NRaRa, —N(R)S(O)2NRaRa or —N(R)S(O)2R;
• or when R1 and R2 are attached to adjacent carbon atoms they are optionally taken together with the atoms to which they are attached to form a 5- or 6-membered ring optionally substituted with one or two groups that are each independently halogen, oxo, oxime, imino, C1-6alkyl, C1-6haloalkyl, or R10;
• each Ra is independently R or, two Ra together with the nitrogen atom to which they are attached form a 3-8 membered heterocyclyl group, optionally including 1-4 additional heteroatoms selected from O, N and S and optionally substituted with 1-4 R groups;
• each Rb is independently halogen, cyano, oxo, C1-6alkyl, C1-6haloalkyl, or —OR;
• m is 0, 1 or 2;
• n is 1, 2, 3 or 4;
• R5 and R6 are each independently hydrogen, halogen, C1-6alkyl optionally substituted with 1-3 Rb, C1-6haloalkyl, C3-8cycloalkyl optionally substituted with one or two Rb, heteroaryl optionally substituted with one or two Rb, aryl optionally substituted with one or two Rb, heterocyclyl(C1-6alkyl) optionally substituted with one or two Rb, —OR, —SR, —NRaRa, —OC(O)R, —C(O)NRaRa, —OC(O)NRaRa, —C(O)OR, —N(R)C(O)R, —N(R)S(O)2R, or R5 and R6 are optionally taken together with the atoms to which they are attached to form a 5- or 6-membered ring optionally including 1-3 additional heteroatoms selected from O, N and S and optionally substituted with 1-4 Rb;
• Z is (a) a fused bicyclic ring of the formula,
• wherein
• ring A is a phenyl or 5- or 6-membered heteroaryl,
• ring B is a 5- or 6-membered heterocyclyl or 5- or 6-membered heteroaryl;
• or (b) pyridinyl or pyrimidinyl,
• wherein
• Z is optionally substituted by one or two groups that are each independently halogen, C1-6alkyl, C1-6haloalkyl, C3-8cycloalkyl, heterocyclyl, aryl, heteroaryl, C3-8cycloalkyl(C1-6alkyl), heterocyclyl(C1-6alkyl), aryl(C1-6alkyl), heteroaryl(C1-6alkyl), —RZ, or —C1-6alkyl-RZ, wherein the C3-8cycloalkyl, heterocyclyl, aryl, heteroaryl, C3-8cycloalkyl(C1-6alkyl), heterocyclyl(C1-6alkyl), aryl(C1-6alkyl), and heteroaryl(C1-6alkyl) are each optionally substituted by one or two groups that are each independently halogen, C1-6alkyl, or RZ;
• and RZ is cyano, —CF3, —OR, —SR, —NRaRa, —C(O)R, —C(O)OR, —C(O)NRaRa, —S(O)2NRaRa, —S(O)2R0, —OC(O)R, —N(R)C(O)R, —OC(O)OR, —OC(O)NRaRa, —N(R)C(O)OR, —N(R)C(O)NRaRa, —N(R)S(O)2R, or —OP(O)(OR)2;
• or Z is (c) phenyl substituted with 1, 2, 3, 4, or 5 groups that are each independently a halogen;
• wherein each R is independently hydrogen, C1-6alkyl, C1-6haloalkyl, C3-8cycloalkyl, heterocyclyl, aryl, heteroaryl, heteroaryl(heteroaryl)-, heterocyclyl(aryl)-, heteroaryl(heterocyclyl)-, C3-8cycloalkyl(C1-6alkyl), heterocyclyl(C1-6alkyl), aryl(C1-6alkyl), or heteroaryl(C1-6alkyl), each optionally substituted by 1-5 groups that are each independently Rb, —OR0, —SR0, —N(R0)2, —C(O)R0, —C(O)OR0, —C(O)N(R0)2, —S(O)2N(R0)2, —OC(O)R0, —N(R0)C(O)R0, —OC(O)OR0, —O(CH2)mC(O)N(R0)2, —N(R0)C(O)OR0, —N(R0)C(O)N(R0)2, or —N(R0)S(O)2R0
• and each R0 is independently hydrogen, C1-6haloalkyl, C1-6alkyl optionally substituted with 1-3 Rb, C3-8cycloalkyl optionally substituted with one or two Rb or, alternatively two R0 together with a nitrogen atom to which they are bound form a 3-8 membered heterocyclyl group, optionally including 1-4 additional heteroatoms selected from O, N and S and optionally substituted with 0-3 Rb and R groups.