Radnai, L.; Young, E. J.; Kikuti, C.; Hafenbreidel, M.; Stremel, R. F.; Lin, L.; Toth, K.; Pasetto, P.; Jin, X.; Patel, A.; Conlon, M.; Briggs, S.; Heidsleck, L.; Sweeney, L.; Sellers, J. R.; Krieger-Burke, T.; Rumbaugh, G.; Cameron, M. D.; Surman, M.; Houdusse, A.; Griffin, P. R.; Kamenecka, T. M.; Miller, C. A.

Non-muscle myosin II (NMII), a molecular motor that regulates critical processes such as cytokinesis and neuronal synaptic plasticity, has substantial therapeutic potential. However, translating this potential to in vivo use has been hampered by the lack of selective tools. The most prototypical non-selective inhibitor, blebbistatin inactivates both NMII and cardiac myosin II (CMII), a key regulator of heart function. Using rational drug design, we developed a series of NMII inhibitors that improve tolerability by selectively targeting NMII over CMII, including MT-228, which has excellent properties such as high brain penetration and efficacy in preclinical models of stimulant use disorder, which has no current FDA-approved therapies. The structure of MT-228 bound to myosin II provides insight into its 17-fold selectivity for NMII over CMII. MT-228's broad therapeutic window opens the door to new disease treatments and provides valuable tools for the scientific community, along with promising leads for future medication development.