A class of 4-oxo-tetrahydroindazole-3-carboxamides is disclosed. The compoun ds bind selectively to GABAA .alpha.-5 receptors, and are useful in therapy whe re cognition enhancement is required, for example in the treatment of Alzheimer 's disease. The compounds are represented by formula (I) wherein R1 and R4 are independently chosen from hydrogen, halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1-6 haloalkyl, C2-6 haloalkenyl and C2-6 haloalkynyl; R2 is hydrog en or C1-6 alkyl; and Ar is phenyl, a 5-membered heterocyclic group containing 1,2,3 or 4 heteroatoms chosen from N, O and S, no more than one of which is O or S, or a 6-membered heterocyclic group containing one or two nitrogen atom s, each of which groups Ar is unsubstituted or substituted by from one to three groups independently chosen from halogen, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C3-7 cycloalkyl, C1-6 alkoxy, C2-6 alkenyloxy, C2-6 alkynylnoxy, C3 -7 cycloalkoxy, C1-6 haloalkyl, C2-6 haloalkenyl, C2-6 haloalkynyl, amino, C1-6 alkylamino, di(C1-6)alkylamino, hydroxy, hydroxy C1-6 alkyl, cyano, nitro, amino C1-6 alkyl, C1-6 alkylaminoC1-6 alkyl, di(C1-6 alkyl)aminoC1-6alkyl or C1-6alkoxycarbonylaminoC1-6alkyl.
TETRAHYDROINDAZOLE DERIVATIVES AS LIGANDS FOR GABA-A ALPHA 5RECEPTORS