Comparative analysis of PknB inhibitors for reactivity and toxicity

Bacterial serine/threonine kinases are increasingly sought after as drug targets for new antibiotics. PknB, an essential kinase in Mycobacteria tuberculosis, is intensely targeted, and many inhibitors are in the developmental pipeline. These inhibitors typically are derived from screens of known kinase inhibitors and most share similar chemical properties as their parent compounds were all designed for optimal pharmacokinetic properties in the human body. Here, we investigate the reactivity and toxicity of a proposed PknB inhibitor, YH-8, which does not follow traditional drug design rules. We found that the compound is highly reactive with thiolating agents and has appreciable toxicity in a zebrafish animal model. Furthermore, we find minimal anti-mycobacterial activity with non-tubercular mycobacteria strains. These data suggest that further investigation is needed into its efficacy and physiochemical properties if it is to be further developed as an effective antibiotic.