A compound of Formula (Ia): wherein R 1a is selected from the group consisting of bicyclic aryl, monocyclic and bicyclic heteroaryl, and monocyclic and bicyclic non-aromatic heterocycle, wherein bicyclic aryl, monocyclic and bicyclic heteroaryl, and monocyclic and bicyclic non-aromatic heterocycle can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 2a is selected from the group consisting of C 1-6 alkyl, -CH 2 OC 1-6 alkyl, - CH 2 Ar, and heteroaryl, wherein aryl (Ar) can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 3a is selected from the group consisting of -CH 2 OC 1-6 alkyl, - CH 2 C NHR 5a, and -CH 2 C R 5a; R 4a is selected from the group consisting of -C (CH 2) n Ph, - C CH 2 NR 6a R 7a, -SO 2 Ar, -SO 2 C 1-6 alkyl, -C (CH 2) n Het, -C C 1-6 alkyl, -C CF 3, heteroaryl, and -(CH 2) n NR 6a R 7a, wherein aryl (Ar) and heteroaryl (Het) can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 5a is selected from the group consisting of C 1-6 alkyl, C 1-6 alkoxy, non-aromatic heterocycle, and -CR 8a R 9a; R 6a, R 7a, R 8a, and R 9a are each independently selected from the group consisting of H, C 1-6 alkyl, and -(CH 2) k OH; or R 6a and R 7a are taken together with the nitrogen to which they are attached to form a piperidine, pyrrolidine, azepane, azetidine, or morpholine ring; or R 8a and R 9a are taken together with the carbon to which they are attached to form an oxetane ring; n is 0, 1, 2, or 3; and k is 1, 2, or 3, a pharmaceutically acceptable salt thereof or a solvate thereof. R 1a is selected from the group consisting of bicyclic aryl, monocyclic and bicyclic heteroaryl, and monocyclic and bicyclic non-aromatic heterocycle, wherein bicyclic aryl, monocyclic and bicyclic heteroaryl, and monocyclic and bicyclic non-aromatic heterocycle can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 2a is selected from the group consisting of C 1-6 alkyl, -CH 2 OC 1-6 alkyl, - CH 2 Ar, and heteroaryl, wherein aryl (Ar) can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 3a is selected from the group consisting of -CH 2 OC 1-6 alkyl, - CH 2 C NHR 5a, and -CH 2 C R 5a; R 4a is selected from the group consisting of -C (CH 2) n Ph, - C CH 2 NR 6a R 7a, -SO 2 Ar, -SO 2 C 1-6 alkyl, -C (CH 2) n Het, -C C 1-6 alkyl, -C CF 3, heteroaryl, and -(CH 2) n NR 6a R 7a, wherein aryl (Ar) and heteroaryl (Het) can be optionally substituted from 1 to 3 times with a substituent selected independently at each occurrence thereof from the group consisting of halogen, cyano, C 1-6 alkyl, and C 1-6 alkoxy; R 5a is selected from the group consisting of C 1-6 alkyl, C 1-6 alkoxy, non-aromatic heterocycle, and -CR 8a R 9a; R 6a, R 7a, R 8a, and R 9a are each independently selected from the group consisting of H, C 1-6 alkyl, and -(CH 2) k OH; or R 6a and R 7a are taken together with the nitrogen to which they are attached to form a piperidine, pyrrolidine, azepane, azetidine, or morpholine ring; or R 8a and R 9a are taken together with the carbon to which they are attached to form an oxetane ring; n is 0, 1, 2, or 3; and k is 1, 2, or 3,