Disclosed herein are pyrido[3′,2′:4,5]thieno[3,2-d]pyrimidine and pyrimido[4′,5′:4,5]thieno[2,3-c]pyridazine compounds, which may be useful as positive allostenc modulators of the muscarinic acetylcholine receptor M4 (mAChR M4). 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.