A compound of Formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is (C1-6)alkyl, (C3-7)cycloalkyl, -C X or -S 2 X, the (C1-6)alkyl and (C3-7)cycloalkyl groups being optionally substituted with one or more substituents independently selected from OH, (C1-4)alkyloxy, (C1-4)alkylsulfonyl, C -NR 9 R 10, C -OR 9, S 2 -NR 9 R 10, CN and halogen, the (C1-4)alkyloxy and (C1-4)alkylsulfonyl groups being optionally substituted with one or more fluoros; X, when present, is (C1-6)alkyl or NR 9 R 10, the (C1-6)alkyl group being optionally substituted with one or more substituents independently selected from OH, (C1-4)alkyloxy, CN and halogen; R 2 and R 3 are independently selected from H, fluoro and (C1-4)alkyl, the (C1-4)alkyl being optionally substituted with one or more fluoros; L is a linker-CR 7 R 8 - or L is absent; R 7 and R 8 are independently selected from H and (C1-4)alkyl or R 7 and R 8, together with the carbon atom to which they are bonded, form a cyclopropyl, cyclobutyl or cyclopentyl group; A is selected from a 6-membered aromatic ring, a 6-membered heteroaromatic ring that contains one to three N atoms, a 5-membered heteroaromatic ring that contains 1 to 3 heteroatoms selected from O, S and N, a fused 10-membered bicyclic aromatic ring system or heteroaromatic ring system that contains one to three N atoms, a fused 9-membered bicyclic heteroaromatic ring system that contains 1 to 3 heteroatoms selected from O, S and N, and a fused 9- or 10- membered bicyclic ring system that contains an aromatic or heteroaromatic ring fused to a non-aromatic carbocyclic or heterocyclic ring; wherein A is optionally substituted with one or more substituents independently selected from (C1-4)alkyl, (C1-4)alkyloxy, (C1-4)alkylsulfonyl, C -NR 9 R 10,S 2 -NR 9 R 10, OH, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy and (C1-4)alkylsulfonyl groups being optionally substituted with one or more fluoros; R 4 and R 6 are independently selected from H, (C1-4)alkyl, (C1-4)alkyloxy, CN and halogen, the (C1-4)alkyl and (C1-4)alkyloxy groups being optionally substituted with one or more fluoros; R 5 is selected from H, (C1-4)alkyl, (C1-4)alkyloxy, -O-(CH 2) n -O-(CH 2) m CH 3, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy and -O-(CH 2) n -O-(CH 2) m CH 3 groups being optionally substituted with OH or one or more fluoros; Y and Z are independently selected from N and CR 11; each R 11, when present, is independently selected from H, (C1-4)alkyl, (C1-4)alkyloxy, -O-(CH 2) n -O-(CH 2) m CH 3, (C1-4)alkylsulfonyl, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy, (C1-4)alkylsulfonyl and -O-(CH 2) n -O-(CH 2) m CH 3, groups being optionally substituted with OH or one or more fluoros; each n is, independently, 1, 2, 3 or 4; each m is, independently, 0 or 1; and each R 9 and R 10, when present, is independently selected from H and (C1-6)alkyl. R 1 is (C1-6)alkyl, (C3-7)cycloalkyl, -C X or -S 2 X, the (C1-6)alkyl and (C3-7)cycloalkyl groups being optionally substituted with one or more substituents independently selected from OH, (C1-4)alkyloxy, (C1-4)alkylsulfonyl, C -NR 9 R 10, C -OR 9, S 2 -NR 9 R 10, CN and halogen, the (C1-4)alkyloxy and (C1-4)alkylsulfonyl groups being optionally substituted with one or more fluoros; X, when present, is (C1-6)alkyl or NR 9 R 10, the (C1-6)alkyl group being optionally substituted with one or more substituents independently selected from OH, (C1-4)alkyloxy, CN and halogen; R 2 and R 3 are independently selected from H, fluoro and (C1-4)alkyl, the (C1-4)alkyl being optionally substituted with one or more fluoros; L is a linker-CR 7 R 8 - or L is absent; R 7 and R 8 are independently selected from H and (C1-4)alkyl or R 7 and R 8, together with the carbon atom to which they are bonded, form a cyclopropyl, cyclobutyl or cyclopentyl group; A is selected from a 6-membered aromatic ring, a 6-membered heteroaromatic ring that contains one to three N atoms, a 5-membered heteroaromatic ring that contains 1 to 3 heteroatoms selected from O, S and N, a fused 10-membered bicyclic aromatic ring system or heteroaromatic ring system that contains one to three N atoms, a fused 9-membered bicyclic heteroaromatic ring system that contains 1 to 3 heteroatoms selected from O, S and N, and a fused 9- or 10- membered bicyclic ring system that contains an aromatic or heteroaromatic ring fused to a non-aromatic carbocyclic or heterocyclic ring; wherein A is optionally substituted with one or more substituents independently selected from (C1-4)alkyl, (C1-4)alkyloxy, (C1-4)alkylsulfonyl, C -NR 9 R 10,S 2 -NR 9 R 10, OH, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy and (C1-4)alkylsulfonyl groups being optionally substituted with one or more fluoros; R 4 and R 6 are independently selected from H, (C1-4)alkyl, (C1-4)alkyloxy, CN and halogen, the (C1-4)alkyl and (C1-4)alkyloxy groups being optionally substituted with one or more fluoros; R 5 is selected from H, (C1-4)alkyl, (C1-4)alkyloxy, -O-(CH 2) n -O-(CH 2) m CH 3, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy and -O-(CH 2) n -O-(CH 2) m CH 3 groups being optionally substituted with OH or one or more fluoros; Y and Z are independently selected from N and CR 11; each R 11, when present, is independently selected from H, (C1-4)alkyl, (C1-4)alkyloxy, -O-(CH 2) n -O-(CH 2) m CH 3, (C1-4)alkylsulfonyl, CN and halogen, the (C1-4)alkyl, (C1-4)alkyloxy, (C1-4)alkylsulfonyl and -O-(CH 2) n -O-(CH 2) m CH 3, groups being optionally substituted with OH or one or more fluoros; each n is, independently, 1, 2, 3 or 4; each m is, independently, 0 or 1; and each R 9 and R 10, when present, is independently selected from H and (C1-6)alkyl.