title: Towards Selective Mycobacterial ClpP1P2 Inhibitors with Reduced Activity against the Human Proteasome.
abstract: Mycobacterium tuberculosisis responsible for the greatest number of deaths worldwide due to a bacterial agent. We recently identified bortezomib (Velcade; compound 1) as a promising antituberculosis (anti-TB) compound. We showed that compound 1 inhibits the mycobacterial caseinolytic proteases P1 and P2 (ClpP1P2) and exhibits bactericidal activity, and we established compound 1 and ClpP1P2 as an attractive lead/target couple. However, compound 1 is a human-proteasome inhibitor currently approved for cancer therapy and, as such, exhibits significant toxicity. Selective inhibition of the bacterial protease over the human proteasome is desirable in order to maintain antibacterial activity while reducing toxicity. We made use of structural data in order to design a series of dipeptidyl-boronate derivatives of compound 1. We tested these derivatives for whole-cell ClpP1P2 and human-proteasome inhibition as well as bacterial-growth inhibition and identified compounds that were up to 100-fold-less active against the human proteasome but that retained ClpP1P2 and mycobacterial-growth inhibition as well as bactericidal potency. The lead compound, compound 58, had low micromolar ClpP1P2 and anti-M. tuberculosisactivity, good aqueous solubility, no cytochrome P450 liabilities, moderate plasma protein binding, and low toxicity in two human liver cell lines, and despite high clearance in microsomes, this compound was only moderately cleared when administered intravenously or orally to mice. Higher-dose oral pharmacokinetics indicated good dose linearity. Furthermore, compound 58 was inhibitory to only 11% of a panel of 62 proteases. Our work suggests that selectivity over the human proteasome can be achieved with a drug-like template while retaining potency against ClpP1P2 and, crucially, anti-M. tuberculosisactivity.
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Moreira
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.|Department of Pharmacy, National University of Singapore, Singapore.
authors.forename: Sridhar
authors.initials: S
authors.lastname: Santhanakrishnan
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Grace J Y
authors.initials: GJY
authors.lastname: Ngan
authors.affiliation: Experimental Therapeutics Center, Agency for Science, Technology and Research (A*STAR), Singapore.
authors.forename: Choon Bing
authors.initials: CB
authors.lastname: Low
authors.affiliation: Experimental Therapeutics Center, Agency for Science, Technology and Research (A*STAR), Singapore.
authors.forename: Kanda
authors.initials: K
authors.lastname: Sangthongpitag
authors.affiliation: Experimental Therapeutics Center, Agency for Science, Technology and Research (A*STAR), Singapore.|Department of Chemistry, National University of Singapore, Singapore.
authors.forename: Anders
authors.identifier: 0000-0002-2790-9340
authors.initials: A
authors.lastname: Poulsen
authors.affiliation: Department of Pharmacy, National University of Singapore, Singapore bwdnus@gmail.com.
authors.forename: Brian W
authors.identifier: 0000-0002-2374-5756
authors.initials: BW
authors.lastname: Dymock
authors.affiliation: Department of Microbiology and Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Thomas
authors.identifier: 0000-0002-9604-9452
authors.initials: T
authors.lastname: Dick
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D000069286:Bortezomib / Q000493:pharmacokinetics / Q000494:pharmacology*; D015195:Drug Design; D049071:Endopeptidase Clp / Q000037:antagonists & inhibitors* / Q000235:genetics; D051379:Mice; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D020102:Mycobacterium smegmatis / Q000187:drug effects* / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D012697:Serine Endopeptidases / Q000235:genetics; D014397:Tuberculosis, Pulmonary / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D061988:Proteasome Inhibitors; D000069286:Bortezomib; C119658:ClpP2 protein, bacteria; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp
keywords: antimycobacterial; caseinolytic protease; dipeptidyl boronic acid