The Pseudo Natural Product Myokinasib Is a Myosin Light Chain Kinase 1 Inhibitor with Unprecedented Chemotype.

Small-molecule chemotypes with unexpected bioactivity may be identified by combining strategies built on the biological relevance of, e.g., natural products (NPs), such as biology-oriented synthesis, with principles that enable efficient coverage of chemical space, such as fragment-based compound design. Evaluation in target-agnostic phenotypic assays and target identification may link biologically relevant chemotypes to unexpected and unknown targets. We describe the phenotypic identification of an unprecedented kinase inhibitor chemotype obtained by synthetic combination of two biosynthetically unrelated NP fragment types. Target identification and biological characterization revealed that the inhibitor, termed Myokinasib, impairs cytokinesis, induces formation of multinucleated cells, and reduces phosphorylated myosin II light chain abundance on stress fibers by selective inhibition of myosin light chain kinase 1. • De novo combination of natural product fragments yields bioactive small molecules • Target-agnostic phenotypic assays identified the MLCK inhibitor Myokinasib • Indotropanes induce cytokinesis failure and multinucleated cells • Myokinasib defines an unprecedented chemotype for kinase inhibition Schneidewind et al. present Myokinasib, a truly unique chiral kinase inhibitor with unprecedented chemotype. It promises to be a tool for the analysis of cellular processes mediated by its target MLCK1. [ABSTRACT FROM AUTHOR]