An isoQC inhibitor of formula or a pharmaceutically acceptable salt, solvate or polymorph thereof, including all tautomers and stereoisomers thereof wherein: R 1 represents 1H-benzimidazolyl or wherein A represents an unbranched or branched C 1-6 alkylene chain and R 11, R 12 and R 13 independently represent H or C 1-2 alkyl; R 2 represents aryl, heteroaryl, phenyl substituted by phenyl, phenyl fused to heterocyclyl or R 2 and R 3 are joined to form a carbocyclyl ring which is fused to phenyl; the aforesaid aryl, heteroaryl, phenyl, heterocyclyl and carbocyclyl optionally being substituted by one or more groups selected from C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl, -SO 2 C 1-4 alkyl, C 1-6 alkoxy-, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, -C OH, -NH 2,-NHC 1-4 alkyl, -N(C 1-4 alkyl)(C 1-4 alkyl), -C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and -C NH(C 3-1 10 cycloalkyl); R 3 represents H or R 2 and R 3 are joined to form a carbocyclyl ring which is fused to phenyl; R 4 represents H; X represents O or S; and Y represents O or S; for use in the treatment and/or prevention of a disease or condition, selected from the group consisting of a. rheumatoid arthritis, atherosclerosis, restenosis, pancreatitis, osteoporosis, b. neuropathic pain, graft rejection/graft failure/graft vasculopathy, HIV infections/AIDS, gestosis, tuberous sclerosis, Guillain-Barré syndrome, chronic inflammatory demyelinising polyradiculoneuropathy and multiple sclerosis, c. neuroinflammation, and d. neurodegenerative diseases, e.g. mild cognitive impairment, Alzheimer's disease, neurodegeneration in Down Syndrome, Familial British Dementia, and Familial Danish Dementia, which may result from neuroinflammation. R 1 represents 1H-benzimidazolyl or wherein A represents an unbranched or branched C 1-6 alkylene chain and R 11, R 12 and R 13 independently represent H or C 1-2 alkyl; R 2 represents aryl, heteroaryl, phenyl substituted by phenyl, phenyl fused to heterocyclyl or R 2 and R 3 are joined to form a carbocyclyl ring which is fused to phenyl; the aforesaid aryl, heteroaryl, phenyl, heterocyclyl and carbocyclyl optionally being substituted by one or more groups selected from C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, C 1-6 haloalkyl, -C 1-6 thioalkyl, -SOC 1-4 alkyl, -SO 2 C 1-4 alkyl, C 1-6 alkoxy-, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, -SOC 3-6 cycloalkyl, C 3-6 alkenyloxy-, C 3-6 alkynyloxy-, -C C 1-6 alkyl, -C OC 1-6 alkyl, C 1-6 alkoxy-C 1-6 alkyl-, nitro, halogen, cyano, hydroxyl, -C OH, -NH 2,-NHC 1-4 alkyl, -N(C 1-4 alkyl)(C 1-4 alkyl), -C N(C 1-4 alkyl)(C 1-4 alkyl), -C NH 2, -C NH(C 1-4 alkyl) and -C NH(C 3-1 10 cycloalkyl); R 3 represents H or R 2 and R 3 are joined to form a carbocyclyl ring which is fused to phenyl; R 4 represents H; X represents O or S; and Y represents O or S; for use in the treatment and/or prevention of a disease or condition, selected from the group consisting of a. rheumatoid arthritis, atherosclerosis, restenosis, pancreatitis, osteoporosis, b. neuropathic pain, graft rejection/graft failure/graft vasculopathy, HIV infections/AIDS, gestosis, tuberous sclerosis, Guillain-Barré syndrome, chronic inflammatory demyelinising polyradiculoneuropathy and multiple sclerosis, c. neuroinflammation, and d. neurodegenerative diseases, e.g. mild cognitive impairment, Alzheimer's disease, neurodegeneration in Down Syndrome, Familial British Dementia, and Familial Danish Dementia, which may result from neuroinflammation. a. rheumatoid arthritis, atherosclerosis, restenosis, pancreatitis, osteoporosis, b. neuropathic pain, graft rejection/graft failure/graft vasculopathy, HIV infections/AIDS, gestosis, tuberous sclerosis, Guillain-Barré syndrome, chronic inflammatory demyelinising polyradiculoneuropathy and multiple sclerosis, c. neuroinflammation, and d. neurodegenerative diseases, e.g. mild cognitive impairment, Alzheimer's disease, neurodegeneration in Down Syndrome, Familial British Dementia, and Familial Danish Dementia, which may result from neuroinflammation.