Comprehensive SAR analysis of actomyolytics, drug candidates targeting the actomyosin complex

There is a long-standing need for inhibitors that selectively target the actomyosin complex, the terminal effector of diverse processes that involve movement in the cells or the body. Such compounds, we term as actomyolytics , hold promise for treating numerous conditions with minimum adverse effects. In this study, we developed efficient synthesis pathways and conducted a detailed structure-activity relationship (SAR) analysis of 144 potential actomyolytics (referred to as the MPH-family) targeting the blebbistatin binding site on myosin-2. The analysis was performed across all muscle and non-muscle myosin-2 isoforms along 2 dimensions, IC50 and maximum response (Emax). This approach led to the identification of isoform-selective inhibitors with the potential to further reduce side effects, as well as elucidation of their distinct mechanisms of selectivity. Notably, we discovered several skeletal muscle myosin-2 selective actomyolitics with therapeutic potential. One molecule from this family, MPH-220, which was previously reported by Gyimesi et al. (2020), is currently undergoing phase 2 clinical trials in humans. In summary, our findings lay the groundwork for future drug development efforts aimed at targeting the final effectors of diverse physiological motor functions. • We developed a novel family of myosin-2 inhibitors targeting the blebbistatin site. • New synthesis routes facilitate combined modifications of the blebbistatin scaffold. • Efficiency was improved by substituting the D-ring and modifying the A-ring. • We achieved a new type of isoform selectivity, based on maximum effect. • Our compounds enable selective modulation of the activity of individual isoforms.