Novel targets and inhibitors of the Mycobacterium tuberculosis cytochrome bd oxidase to foster anti-tuberculosis drug discovery

Introduction: Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is the most devastating bacterial disease. Multidrug-resistant Mtb strains are spreading worldwide, underscoring the need for new anti-TB targets and inhibitors. The respiratory chain complexes, including the cytochrome bd oxidase (cyt-bd), have been identified as an attractive target for drug development. Recent novel structural and mechanistic insight as well as inhibitors of Mtb’s cyt-bd brought this enzyme into the focus. Areas covered: In this review, the authors describe conditions that stimulate the biogenesis of Mtb cyt-bd, its structural-, mechanistic-, and substrate-binding traits. They discuss the present Mtb cyt-bd inhibitors, novel targets within the enzyme and structure activity relationship features that are required for mycobacterial cyt-bd inhibition and augment their understanding on improving the potency of cyt-bd inhibitors. Expert opinion: A deeper structure-mechanistic understanding of Mtb’s cyt-bd is a prerequisite for in silico efforts to: (i) identify pathogen specific targets for the design of novel nontoxic hit molecules, forming the platform for the development of new leads, (ii) design mechanism of action studies, (iii) perform medicinal chemistry of existing inhibitors to improve their potency and pharmacokinetic/-dynamic properties. Phase studies with such optimized cyt-bd inhibitors in combination with anti-TB compounds targeting the oxidative phosphorylation pathway is recommended.