Molecular model of the drug Isofloxythepin (C23.H29.F.N2.O.S). This antipsychotic agent is used to treat agitated psychotic behaviour. It also has been shown to bind covalently to the SARS-CoV-2 main protease, offering a potent antiviral activity at nontoxic concentration. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red), fluorine (light blue) and sulphur (yellow).