Positive allosteric modulators of the muscarinic acetylcholine receptor m4

Disclosed herein are tricyclic compounds, including pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine-8-amine, pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine-4-amine, pyrazino[2′,3′:4,5]thieno[3,2-d]pyrimidin-4-amine, pyrido[3′,2′:4,5]furo[3, 2-d]pyrimidin-4-amine, and pyrimido[4′,5′:4,5]furo[2,3-c]pyridazin-8-amine compounds, which may be useful as positive allosteric modulators of the muscarinic acetylcholine receptor M 4 (mAChR M 4 ). Also disclosed herein are methods of making the compounds, pharmaceutical compositions comprising the compounds, and methods of treating neurological and psychiatric disorders associated with muscarinic acetylcholine receptor dysfunction using the compounds and compositions.