A compound of Formula or a pharmaceutically acceptable salt thereof: wherein: each R is independently H or C CH 3; R 1 and R 2 are independently selected from the group consisting of: H, C 1-6 alkyl, C 2-6 alkenyl, C 1-6 alkoxy, -(CH 2) n -cyclopropyl and -(CH 2) n -cyclobutyl wherein n is 0, 1,2, 3 or 4; or R 1 and R 2 may be joined together with the nitrogen atom to which they are attached to form azetidine, pyrrolidine, piperidine or isoxazolidine, said C 1-6 alkyl, C 2-6 alkenyl, C 1-6 alkoxy, -(CH 2) n -cyclopropyl, -(CH 2) n -cyclobutyl, azetidine, pyrrolidine, piperidine and isoxazolidine optionally mono-substituted with fluoro, hydroxy or methyl; R3 is selected from the group consisting of: C 1-8 alkyl, C 2-8 alkenyl, C 2-8 alkynyl, C 3-6 cycloalkyl, aryl and heteroaryl, each optionally mono-substituted with fluoro or OH; R 4 is selected from the group consisting of: H, F, C 1-8 alkyl, C 2-8 alkenyl and C 2-8 alkynyl, each, apart from H or F, optionally mono-substituted with fluoro or OH; or R 3 and R 4 and the carbon atom to which they are attached may join together to form vinyl or a 3 to 7-membered carbocyclic or heterocyclic ring, said 3 to 7-membered carbocyclic or heterocyclic ring optionally containing a double bond and optionally mono-substituted with fluoro or OH; or a compound of Formula (Ia) or a pharmaceutically acceptable salt thereof: wherein: R 1 and R 2 are independently selected from the group consisting of: H, C 1-6 alkyl and cyclopropylmethyl; or R 1 and R 2 may be joined together with the nitrogen atom to which they are attached to form azetidine or pyrrolidine, said C 1-6 alkyl, cyclopropylmethyl, azetidine or pyrrolidine optionally substituted with 1 to 3 substituents selected from fluoro and methyl; R3 is selected from the group consisting of: C 1-8 alkyl, C 2-8 alkenyl, C 2-8 alkynyl and C 3-6 cycloalkyl, each optionally substituted with 1 to 3 substituents selected from fluoro and OH; and R 4 is selected from the group consisting of: H, F, C 1-8 alkyl, C 2-8 alkenyl and C 2-8 alkynyl, each excluding hydrogen optionally substituted with 1 to 3 substituents selected from fluoro and OH; or R 3 and R 4 and the carbon atom to which they are attached may join together to form a 5-membered carbocyclic ring optionally containing a double bond and optionally substituted with 1 to 3 substituents selected from fluoro and OH; R5 is selected from H, F, OH and OC CH 3; with the proviso that when R 4 is F then R 5 is other than OH and OC CH 3. each R is independently H or C CH 3; R 1 and R 2 are independently selected from the group consisting of: H, C 1-6 alkyl, C 2-6 alkenyl, C 1-6 alkoxy, -(CH 2) n -cyclopropyl and -(CH 2) n -cyclobutyl wherein n is 0, 1,2, 3 or 4; or R 1 and R 2 may be joined together with the nitrogen atom to which they are attached to form azetidine, pyrrolidine, piperidine or isoxazolidine, said C 1-6 alkyl, C 2-6 alkenyl, C 1-6 alkoxy, -(CH 2) n -cyclopropyl, -(CH 2) n -cyclobutyl, azetidine, pyrrolidine, piperidine and isoxazolidine optionally mono-substituted with fluoro, hydroxy or methyl; R3 is selected from the group consisting of: C 1-8 alkyl, C 2-8 alkenyl, C 2-8 alkynyl, C 3-6 cycloalkyl, aryl and heteroaryl, each optionally mono-substituted with fluoro or OH; R 4 is selected from the group consisting of: H, F, C 1-8 alkyl, C 2-8 alkenyl and C 2-8 alkynyl, each, apart from H or F, optionally mono-substituted with fluoro or OH; or R 3 and R 4 and the carbon atom to which they are attached may join together to form vinyl or a 3 to 7-membered carbocyclic or heterocyclic ring, said 3 to 7-membered carbocyclic or heterocyclic ring optionally containing a double bond and optionally mono-substituted with fluoro or OH; R 1 and R 2 are independently selected from the group consisting of: H, C 1-6 alkyl and cyclopropylmethyl; or R 1 and R 2 may be joined together with the nitrogen atom to which they are attached to form azetidine or pyrrolidine, said C 1-6 alkyl, cyclopropylmethyl, azetidine or pyrrolidine optionally substituted with 1 to 3 substituents selected from fluoro and methyl; R3 is selected from the group consisting of: C 1-8 alkyl, C 2-8 alkenyl, C 2-8 alkynyl and C 3-6 cycloalkyl, each optionally substituted with 1 to 3 substituents selected from fluoro and OH; and R 4 is selected from the group consisting of: H, F, C 1-8 alkyl, C 2-8 alkenyl and C 2-8 alkynyl, each excluding hydrogen optionally substituted with 1 to 3 substituents selected from fluoro and OH; or R 3 and R 4 and the carbon atom to which they are attached may join together to form a 5-membered carbocyclic ring optionally containing a double bond and optionally substituted with 1 to 3 substituents selected from fluoro and OH; R5 is selected from H, F, OH and OC CH 3;