title: Efflux pump inhibitors: targeting mycobacterial efflux systems to enhance TB therapy.
abstract: The emergence of drug resistance continues to plague TB control, with a global increase in the prevalence of MDR-TB. This acts as a gateway to XDR-TB and thus emphasizes the urgency for drug development and optimal treatment options. Bedaquiline is the first new anti-TB drug approved by the FDA in 40 years and has been shown to be an effective treatment option for MDR Mycobacterium tuberculosis infection. Bedaquiline has also recently been included in clinical trials for new regimens with the aim of improving and shortening treatment periods. Alarmingly, efflux-mediated bedaquiline resistance, as well as efflux-mediated cross-resistance to clofazimine, has been identified in treatment failures. This mechanism of resistance results in efflux of a variety of anti-TB drugs from the bacterial cell, thereby decreasing the intracellular drug concentration. In doing so, the bacillus is able to render the antibiotic treatment ineffective. Recent studies have explored strategies to reverse the resistance phenotype conferred by efflux pump activation. It was observed that the addition of efflux pump inhibitors partially restored drug susceptibility in vitro and in vivo. This has significant clinical implications, especially in MDR-TB management where treatment options are extremely limited. This review aims to highlight the current efflux pump inhibitors effective against M. tuberculosis, the effect of efflux pump inhibitors on mycobacterial growth and the clinical promise of treatment with efflux pump inhibitors and standard anti-TB therapy.
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Pule
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa ssampson@sun.ac.za.
authors.forename: Samantha L
authors.initials: SL
authors.lastname: Sampson
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Warren
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Philippa A
authors.initials: PA
authors.lastname: Black
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Paul D
authors.initials: PD
authors.lastname: van Helden
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Tommie C
authors.initials: TC
authors.lastname: Victor
authors.affiliation: DST/NRF Centre of Excellence for Biomedical Tuberculosis Research, SAMRC Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: Gail E
authors.initials: GE
authors.lastname: Louw
mesh_terms: D000995:Antitubercular Agents / Q000378:metabolism / Q000494:pharmacology*; D001693:Biological Transport, Active / Q000187:drug effects*; D002991:Clofazimine / Q000378:metabolism / Q000494:pharmacology; D064687:Diarylquinolines / Q000378:metabolism / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000187:drug effects*
chemical_list: D000995:Antitubercular Agents; D064687:Diarylquinolines; D026901:Membrane Transport Proteins; C493870:bedaquiline; D002991:Clofazimine