Development of clinically viable non-muscle myosin II small molecule inhibitors

Non-muscle myosin II (NMII), a molecular motor that regulates critical processes such as cytokinesis and neuronal plasticity, has substantial therapeutic potential. However, translating this potential to in vivo use has been hampered by a lack of selective tools. The most prototypical non-selective inhibitor inactivates both NMII and cardiac muscle myosin II (CMII), a key regulator of heart function. Using rational drug design, we developed a series of NMII inhibitors that markedly improve tolerability by selectively targeting NMII over CMII, including MT-228 and clinical candidate MT-110. MT-228 and MT-110 have excellent properties, including high brain penetration and efficacy in preclinical models of methamphetamine use disorder (MUD), which has no current FDA-approved therapies. The structure of MT-228 bound to myosin II provides insight into its selectivity for NMII over CMII. The broad therapeutic windows of these NMII inhibitors provide valuable tools for the scientific community and a promising clinical candidate for the treatment of MUD.