title: Mode of Action of Clofazimine and Combination Therapy with Benzothiazinones against Mycobacterium tuberculosis.
abstract: Clofazimine (CZM) is an antileprosy drug that was recently repurposed for treatment of multidrug-resistant tuberculosis. In Mycobacterium tuberculosis, CZM appears to act as a prodrug, which is reduced by NADH dehydrogenase (NDH-2), to release reactive oxygen species upon reoxidation by O2. CZM presumably competes with menaquinone (MK-4), a key cofactor in the mycobacterial electron transfer chain, for its reduction by NDH-2. We studied the effect of MK-4 supplementation on the activity of CZM against M. tuberculosis and found direct competition between CZM and MK-4 for the cidal effect of CZM, against nonreplicating and actively growing bacteria, as MK-4 supplementation blocked the drug's activity against nonreplicating bacteria. We demonstrated that CZM, like bedaquiline, is synergistic in vitro with benzothiazinones such as 2-piperazino-benzothiazinone 169 (PBTZ169), and this synergy also occurs against nonreplicating bacteria. The synergy between CZM and PBTZ169 was lost in an MK-4-rich medium, indicating that MK-4 is the probable link between their activities. The efficacy of the dual combination of CZM and PBTZ169 was tested in vivo, where a great reduction in bacterial load was obtained in a murine model of chronic tuberculosis. Taken together, these data confirm the potential of CZM in association with PBTZ169 as the basis for a new regimen against drug-resistant strains of M. tuberculosis.
authors.affiliation: Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors.forename: Benoit
authors.initials: B
authors.lastname: Lechartier
authors.affiliation: Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland stewart.cole@epfl.ch.
authors.forename: Stewart T
authors.initials: ST
authors.lastname: Cole
mesh_terms: D000818:Animals; D000995:Antitubercular Agents / Q000494:pharmacology*; D002991:Clofazimine / Q000494:pharmacology*; D064687:Diarylquinolines / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000379:methods; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D010879:Piperazines / Q000494:pharmacology*; D013843:Thiazines / Q000494:pharmacology*; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy; D024482:Vitamin K 2 / Q000494:pharmacology
chemical_list: D000995:Antitubercular Agents; D064687:Diarylquinolines; D010879:Piperazines; D013843:Thiazines; D024482:Vitamin K 2; C493870:bedaquiline; C000592783:macozinone; D002991:Clofazimine