Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa

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dc.contributor.advisorWiesner, Lubbe
dc.contributor.advisorMcllleron, Helen
dc.contributor.authorKatundu, Precious Ngwalero
dc.date.accessioned2026-06-23T07:53:04Z
dc.date.available2026-06-23T07:53:04Z
dc.date.issued2026
dc.date.updated2026-06-23T07:34:09Z
dc.description.abstractBoth bedaquiline (approved by the FDA for use in pulmonary MDR-TB) and its metabolite, M2, exhibit intracellular antimycobacterial activity against tuberculosis. Understanding their intracellular pharmacokinetics is useful in elucidating the drug exposure-efficacy and exposure-toxicity relationships. LC-MS/MS assays were developed to quantify total bedaquiline and M2 in human plasma and peripheral blood mononuclear cells (PBMCs) and their unbound fractions in human plasma. Bedaquiline and M2 were extracted from both matrices by precipitation and solid phase extraction and quantified by LC-MS/MS. Unbound fractions of both analytes were isolated from the plasma by ultracentrifugation and quantified by a slightly adjusted method. The methods were validated over plasma ranges of 20.0–5000 ng/mL and 10.0–500 ng/mL and intracellular ranges of 2.5–200 pg/million cells and 12.5–1000 pg/million cells for bedaquiline and M2, respectively, and over a range of 0.100–5.00 ng/mL for both unbound fractions. Bedaquiline and M2 were measured in plasma and PBMC samples, prepared from blood samples collected by sparse and intensive sampling in the PROBeX clinical study in which 21 participants received bedaquiline-containing regimens for the treatment of RR-TB. A non- compartmental analysis described plasma and intracellular drug exposures, and a population pharmacokinetic model explored the relationship between total plasma and intracellular drug pharmacokinetics. Total plasma concentrations were higher for bedaquiline than for M2, whereas intracellular concentrations were higher for M2 than for bedaquiline, supporting in vitro evidence that M2 is the main inducer of phospholipidosis within the cells. The intracellular-plasma accumulation ratio for bedaquiline and M2 increased linearly, peaking after 2 months of treatment. Intracellular-plasma ratios for both bedaquiline and M2 were lower in HIV-positive than in HIV-negative patients. Bedaquiline and M2 were detectable in PBMCs 6 months after treatment discontinuation. Unbound concentrations of bedaquiline and M2 were higher than those reported in the literature. This finding requires further investigation. This first-time investigation into intracellular bedaquiline and M2 concentrations gives insight into bedaquiline pharmacokinetics, particularly in the context of RR-TB treatment. Our method for quantifying unbound bedaquiline and M2 in human plasma provides a foundation for further research into similar highly protein-bound and lipophilic drugs.
dc.identifier.apacitationKatundu, P. N. (2026). <i>Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa</i>. (). University of Cape Town ,Faculty of Health Sciences ,Department of Medicine. Retrieved from http://hdl.handle.net/11427/43355en_ZA
dc.identifier.chicagocitationKatundu, Precious Ngwalero. <i>"Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa."</i> ., University of Cape Town ,Faculty of Health Sciences ,Department of Medicine, 2026. http://hdl.handle.net/11427/43355en_ZA
dc.identifier.citationKatundu, P.N. 2026. Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa. . University of Cape Town ,Faculty of Health Sciences ,Department of Medicine. http://hdl.handle.net/11427/43355en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Katundu, Precious Ngwalero AB - Both bedaquiline (approved by the FDA for use in pulmonary MDR-TB) and its metabolite, M2, exhibit intracellular antimycobacterial activity against tuberculosis. Understanding their intracellular pharmacokinetics is useful in elucidating the drug exposure-efficacy and exposure-toxicity relationships. LC-MS/MS assays were developed to quantify total bedaquiline and M2 in human plasma and peripheral blood mononuclear cells (PBMCs) and their unbound fractions in human plasma. Bedaquiline and M2 were extracted from both matrices by precipitation and solid phase extraction and quantified by LC-MS/MS. Unbound fractions of both analytes were isolated from the plasma by ultracentrifugation and quantified by a slightly adjusted method. The methods were validated over plasma ranges of 20.0–5000 ng/mL and 10.0–500 ng/mL and intracellular ranges of 2.5–200 pg/million cells and 12.5–1000 pg/million cells for bedaquiline and M2, respectively, and over a range of 0.100–5.00 ng/mL for both unbound fractions. Bedaquiline and M2 were measured in plasma and PBMC samples, prepared from blood samples collected by sparse and intensive sampling in the PROBeX clinical study in which 21 participants received bedaquiline-containing regimens for the treatment of RR-TB. A non- compartmental analysis described plasma and intracellular drug exposures, and a population pharmacokinetic model explored the relationship between total plasma and intracellular drug pharmacokinetics. Total plasma concentrations were higher for bedaquiline than for M2, whereas intracellular concentrations were higher for M2 than for bedaquiline, supporting in vitro evidence that M2 is the main inducer of phospholipidosis within the cells. The intracellular-plasma accumulation ratio for bedaquiline and M2 increased linearly, peaking after 2 months of treatment. Intracellular-plasma ratios for both bedaquiline and M2 were lower in HIV-positive than in HIV-negative patients. Bedaquiline and M2 were detectable in PBMCs 6 months after treatment discontinuation. Unbound concentrations of bedaquiline and M2 were higher than those reported in the literature. This finding requires further investigation. This first-time investigation into intracellular bedaquiline and M2 concentrations gives insight into bedaquiline pharmacokinetics, particularly in the context of RR-TB treatment. Our method for quantifying unbound bedaquiline and M2 in human plasma provides a foundation for further research into similar highly protein-bound and lipophilic drugs. DA - 2026 DB - OpenUCT DP - University of Cape Town KW - N-desmethyl bedaquiline KW - TB patients KW - HIV infection KW - South Africa LK - https://open.uct.ac.za PB - University of Cape Town PY - 2026 T1 - Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa TI - Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa UR - http://hdl.handle.net/11427/43355 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/43355
dc.identifier.vancouvercitationKatundu PN. Investigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa. []. University of Cape Town ,Faculty of Health Sciences ,Department of Medicine, 2026 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/43355en_ZA
dc.language.isoen
dc.language.rfc3066eng
dc.publisher.departmentDepartment of Medicine
dc.publisher.facultyFaculty of Health Sciences
dc.publisher.institutionUniversity of Cape Town
dc.subjectN-desmethyl bedaquiline
dc.subjectTB patients
dc.subjectHIV infection
dc.subjectSouth Africa
dc.titleInvestigating the relationship between plasma and intracellular concentrations of bedaquiline and its metabolite N-desmethyl bedaquiline (M2) in drug resistant-TB patients with and without HIV infection in South Africa
dc.typeThesis / Dissertation
dc.type.qualificationlevelDoctoral
dc.type.qualificationlevelPhD
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