Identification and benchmarking of Myokinasib-II as a highly selective and potent chemical probe for exploring MLCK1 inhibition

Deciphering functional relevance of every protein is crucial to developing a better (patho)physiological understanding of human biology. Discovery and use of quality chemical probes propel exciting developments for developing drugs in therapeutic areas with unmet clinical needs. Myosin Light Chain Kinase (MLCK) serves as a possible therapeutic target in a plethora of diseases, including inflammatory diseases, cancer etc. Recent years have seen substantial increase in interest in exploring MLCK biology. However, there is only one widely used MLCK modulator, namely ML-7, that too with a narrow working concentration window and high toxicity profile leading to limited insights. Herein, we report the identification of a potent and highly selective chemical probe, Myokinasib-II, from the synthesis and structure-activity relationship studies of a focussed indotropane-based compound collection. Notably, it is structurally distinct from ML-7 and hence, meets the need for an alternative inhibitor to study MLCK biology as per the recommended best practices. Moreover, our extensive benchmarking studies demonstrate that Myokinasib-II displays better potency, better selectivity profile and no non-specific interference in relevant assays as compared to other known MLCK inhibitors.