Provided is 5-(3-chloro-4-fluorophenyl)-7-cyclopropyl-3-(2-(3-fluoro-3-methylazetidin-1-yl)-2-oxoethyl)-3,7-dihydro-4H-pyrrolo[2,3-d]pyrimidin-4-one and pharmaceutically acceptable salts thereof, and their uses in the treatment of psychiatric, neurological, and neurodevelopmental disorders, as well as diseases of the nervous system.