The disclosure relates to a pyrazoloquinoline derivatives or pharmacologically acceptable salt of formula (I). These compounds have an inhibitory effect on PDE9 and may have use in treating Alzheimer&rsquos disease. Example compounds include: (-)-7-(6-methoxy-2,4-dimethylpyridin-3-yl)-1-(tetrahydrofuran-3-yl)-IHpyrazolo[4,3-c]quinolin-4(5H)-one, (S)-8-fluoro-7-(2-methoxy-4,6-dimethylpyridin-3-yl)-1-(tetrahydrofuran-3-yl)-1H-pyrazolo[4,3-c]quinolin-4(5H)-one (S)-7-(6-ethoxy-2,4-dimethylpyridin-3-yl)-1-(tetrahydrofuran-3-yl)-1Hpyrazolo[4,3-c]quinolin-4(5H)-one (S)-8-fluoro-7-(6-methoxy-2,4-dimethylpyridin-3-yl)-I-(tetrahydrofuran-3-yl)-1H-pyrazolo[4,3-c]quinolin-4(5H)-one and (S)-7-(2-methoxy-3,5-dimethylpyridin-4-yl)-1-(tetrahydrofuran-3-yl)-1Hpyrazolo[4,3-c]quinolin-4(5H)-one.
