20. The compound of claim 1, which is selected from the compound: 12-benzhydryl-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(bis(3-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(bis(4-chlorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(bis(3-chlorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(bis(4-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

13-benzhydryl-4-hydroxy-8,9,10,11-tetrahydro-7H,13H-pyridazino[1′,6′:4,5][1,2,4]triazino[1,2-a][1,2]diazepine-3,5-dione;

13-(bis(3-fluorophenyl)methyl)-4-hydroxy-8,9,10,11-tetrahydro-7H,13H-pyridazino[1′,6′:4,5][1,2,4]triazino[1,2-a][1,2]diazepine-3,5-dione;

(R)-12-(bis(3-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(S)-12-(bis(3-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(9aR,10S)-10-benzhydryl-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10R)-10-benzhydryl-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aS,10R)-10-benzhydryl-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aS,10S)-10-benzhydryl-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-fluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10R)-10-(bis(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aS,10R)-10-((S)-(3-chlorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(10aS,11R)-11-benzhydryl-4-hydroxy-7,8,10a,11-tetrahydro-10 OH-pyridazino[1′,6′:4,5]pyrazino[2, 1-c][1,4]oxazine-3,5-dione;

12-benzhydryl-7-hydroxy-3,4,12,12a-tetrahydro-2H-pyridazino[1′,6′:4,5]pyrazino[2, 1-b][1,3]oxazine-6,8-dione;

11-(bis(3-fluorophenyl)methyl)-4-hydroxy-8,9-dihydro-7H,11H-pyrazolo[1,2-a]pyridazino[1,6-d][1,2,4]triazine-3,5-dione;

12-(1,1-diphenylethyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a: 1′,6′-d][1,2,4]triazine-3,5-dione;

12-(bis(2-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-benzhydryl-4-hydroxy-10-methyl-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a: 1′,6′-d][1,2,4]triazine-3,5-dione;

12-benzhydryl-4-hydroxy-7-methyl-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a: 1′,6′-d][1,2,4]triazine-3,5-dione;

12-benzhydryl-4-hydroxy-7,10-dimethyl-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(6,11-dihydrodibenzo[b,e]thiepin-11-yl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(6,11-dihydrodibenzo[b,e]oxepin-11-yl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

12-(7,8-difluoro-6,11-dihydrodibenzo[b,e]thiepin-11-yl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(S)-12-benzhydryl-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(S)-12-(bis(4-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(R)-12-(bis(4-fluorophenyl)methyl)-4-hydroxy-7,8,9,10-tetrahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazine-3,5-dione;

(9aR,10S)-10-((R)-(2-fluorophenyl)(phenyl)methyl)-4-hydroxy-8, 9, a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl)(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,4-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,5-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(4-fluoro-2-methylphenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,4-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2-fluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,5-difluorophenyl)(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(4-fluoro-2-methylphenyl) (2-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2-fluorophenyl)(2-methoxyphenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2-fluorophenyl)(o-tolyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,5-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,6-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,6-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,6-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3-fluorophenyl)(3,4,5-trifluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2-fluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,4-difluorophenyl)(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,5-difluorophenyl)(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2-fluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(4-fluoro-2-methylphenyl)(2-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(4-fluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3-fluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,6-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,6-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,6-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-fluorophenyl)(3,4,5-trifluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,3-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(4-fluorophenyl)(o-tolyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10R)-10-((S)-(4-fluorophenyl)(o-tolyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(4-fluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,4-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(4-fluoro-2-methylphenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,3-difluorophenyl)(2,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10R)-10-(bis(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,3-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,5-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,4-difluorophenyl)(3,5-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(3,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(2,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,5-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,5-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,5-difluorophenyl)(3,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3,5-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,5-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,4-difluorophenyl)(3,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(4-fluorophenyl)(o-tolyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,4-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,4-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,4-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2,3-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,3-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(4-fluoro-2-methylphenyl) (4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl) (4-fluorophenyl)methyl)-4-hydroxy-2-(hydroxymethyl)-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,3-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,4-difluorophenyl)(3,5-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,5-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,5-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,5-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,5-difluorophenyl)(3,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3,5-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,4-difluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,4-difluorophenyl)(phenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,4-difluorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2,4-difluorophenyl)(3,4-difluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

10-(bis(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

4-((R)-(3-fluorophenyl)((9aR,10S)-4-hydroxy-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-10-yl)methyl)benzonitrile;

(9aR,10S)-10-((S)-(4-chlorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-chlorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(2-bromophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(2-bromophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3-fluorophenyl)(o-tolyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((S)-(3-chlorophenyl)(3-fluorophenyl)methyl)-4-hydroxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-chlorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-((R)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7,7-dimethyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10R)-10-((S)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7,7-dimethyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(7S,9aR,10S)-10-((R)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7-methyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(7S,9aR,10R)-1-((S)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7-methyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(7R,9aR,10S)-10-((R)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7-methyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(7R,9aR,10R)-10-((S)-(3-fluorophenyl)(4-fluorophenyl)methyl)-4-hydroxy-7-methyl-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(8S,9aR,10S)-10-(bis(3-fluorophenyl)methyl)-4-hydroxy-8-methoxy-8,9,9a, 10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(8R,9aR,10S)-10-(bis(3-fluorophenyl)methyl)-4-hydroxy-8-methoxy-8,9,9a,10-tetrahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(10aR,11S)-11-benzhydryl-4-hydroxy-7,8,10a,11-tetrahydro-10 OH-pyridazino[1′,6′:4,5]pyrazino[2, 1-c][1,4]oxazine-3,5-dione;

11-benzhydryl-4-hydroxy-7,8,9, 10,10a,11-hexahydropyrido[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

11-(bis(3-fluorophenyl)methyl)-4-hydroxy-7,8,9, 10,10a,11-hexahydropyrido[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

11-benzhydryl-4-hydroxy-7,8,10a,11-tetrahydro-1 OH-pyridazino[1′,6′:4,5]pyrazino[2, 1-c][1,4]oxazine-3,5-dione;

11-benzhydryl-4-hydroxy-7-methyl-7,8,9, 10,10a,11-hexahydropyrido[1′,2′:4,5]pyrazino[1,2-b]pyridazine-3,5-dione;

(9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl 3-methylbutanoate;

(9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl 3-methylbutanoate;

(9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl acetate;

(9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl isobutyrate;

(9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl isopropyl carbonate;

1-(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)ethyl ethyl carbonate;

(S)-((12-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,7,8,9,10-hexahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazin-4-yl)oxy)methyl ethyl carbonate;

(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl (2-methoxyethyl) carbonate;

1-(((9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)ethyl ethyl carbonate;

(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl methyl carbonate;

(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl ethyl carbonate;

(((9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl methyl carbonate;

(((9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl ethyl carbonate;

(((9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl isopropyl carbonate;

(((9aR,10S)-10-((R)-(4-fluorophenyl)(phenyl)methyl)-3,5-dioxo-3,5,8,9,9a, 10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl methyl carbonate;

(((9aR,10S)-10-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl pivalate;

(S)-((12-(bis(3-fluorophenyl)methyl)-3,5-dioxo-3,5,7,8,9,10-hexahydro-12H-dipyridazino[1,2-a:1′,6′-d][1,2,4]triazin-4-yl)oxy)methyl methyl carbonate;

(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl L-valinate;

(9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl dimethylcarbamate;

(((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methyl ethyl(methyl)carbamate;

methyl 2-(((((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a, 10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy) (ethoxy)phosphoryl)oxy)acetate;

and

methyl 2-((((((9aR,10S)-10-(bis(4-fluorophenyl)methyl)-3,5-dioxo-3,5,8,9,9a,10-hexahydro-7H-pyrrolo[1′,2′:4,5]pyrazino[1,2-b]pyridazin-4-yl)oxy)methoxy)carbonyl)oxy)-2-methylpropanoate;

and a pharmaceutically acceptable salt thereof.