There is currently no information available on the transfer of the second-line anti-TB drug, rifapentine and its metabolite, into breastmilk. The subsequent implications to the breastfed infant, as well as consequences of long-term exposure to potentially sub-therapeutic drug levels with regards to the development of drug resistant bacteria is therefore not known. A liquid chromatography method with detection by mass spectrometry (LC-MS/MS) is described for the quantification of rifapentine and its metabolite, 25-O-desacetyl rifapentine in human breastmilk, using rifampicin-d3 as an internal standard. An AB Sciex 4000 mass spectrometer at unit resolution in the multiple reaction monitoring (MRM) mode was used to monitor the transition of the protonated precursor ions m/z 877.5, m/z 835.4 and m/z 827.4 to the product ions m/z 151.1, m/z 453.2 and m/z 151.200 for rifapentine, 25-Odesacetyl rifapentine and rifampicin-d3, respectively. Ions were produced using Electro spray ionisation (ESI) in the positive ionisation mode. An Agilent Poroshell 120 EC-C18 (4.6 x 50 mm, 2.7 μm) column was used for chromatographic separation using an isocratic method of acetonitrile containing 0.1% formic acid and water containing 10% methanol and 0.1% formic acid (55:45, v/v), at a flow rate of 450 µl per minute. The retention times for rifapentine, 25- O-desacetyl rifapentine and rifampicin-d3 were ≈2.67, ≈1.88 and ≈1.96 minutes, respectively. The method was developed and validated according to FDA guidelines. The extraction method consisted of a combination of protein precipitation and C18 solid phase extraction. Rifapentine and 25-O-desacetyl rifapentine showed no significant carry over on the Agilent autosampler. The method was reproducible when analysed with human breastmilk from six different sources from Western Cape Maternity Breastmilk Bank. Rifapentine mean extraction yield was 84.2% (%CV = 1.7) and that of 25-O-desacetyl rifapentine was 71.1% (%CV = 10.8). Rifapentine had a mean process efficiency of 80.4% (%CV = 4.7) and that of 25-O-desacetyl rifapentine was 95.7% (%CV = 5.7). Intra- and inter day validations over 3 days were performed. The calibration curves fit a quadratic regression with 1/x weighting over a concentration range of 2 - 2000 ng/ml for both rifapentine and 25-Odesacetyl rifapentine based on the analyte/internal standard peak area ratios, the accuracy ranged from 92.9% to 105.5% for both rifapentine and 25-O-desacetyl rifapentine standards. The Quality Controls accuracy ranged from 97.4% to 106.0% for both rifapentine and 25-Odesacetyl rifapentine. Stock solutions were shown to be stable for 69 days at -80°C. v Rifapentine and 25-O-desacetyl rifapentine were stable in human breastmilk for up to 72 hours at approximately -80°C and -20°C, on benchtop for ≈4.5 hours on ice and after three freeze-thaw cycles. Rifapentine and 25-O-desacetyl rifapentine were shown to be stable on the autosampler over a period of approximately 48 hours after which the entire batch could be reinjected. Autosampler stability revealed a decrease in peak area ratios, indicating that a partial batch cannot be reinjected after 48 hours in case of instrument failure. This method will be utilized in the analysis of patient samples from a clinical study in South Africa in breastfeeding women with tuberculosis.

Includes bibliographical references (leaves 42-48). / The objective of this study is to evaluate whether ARV TDM reduces mortality and morbidity of adult patients on cART.

No description available.

Background: The medical histories of patients are data picked up by a doctor by making inquiries of the patient and of other individuals who know the individual and can give a reasonable response. In clinical trials, obtaining an accurate medical and treatment history is also an important factor in establishing whether or not a person is an eligible participant, and thereafter supports the assessment of any change in health during the trial, for example, the assessment of adverse events (AEs). Study objectives: To understand discrepancies between the medical histories from online self-reports, electronic medical records, and in-depth interviews of those applying to be part of an adult volunteer database for clinical trials; explore ways of engaging with potential volunteers, such that self-reported medical histories are as comprehensive as possible; explore the feasibility of accessing electronic records for those responding to advertisements. Methodology: This study was designed as mixed methods, with sequential explanatory design collecting quantitative and qualitative data and nested in an existing adult volunteer database. people from the Cape Town community were invited to join the database, in response to an advertisement and through a link to the database website; particularly those who were potentially eligible for a typical healthy volunteer trial, and who reported different information to that obtained from the electronic records. Results: 38 people responded to the online questionnaire, the majority being female. According to the online self-report questionnaire, ten people (10/38; 26.3%) had chronic medical conditions; mostly HIV (7/10; 70%). We accessed the Western Cape electronic medical records for only 8/38 (21%). Comparing the online questionnaire with the medical records, it was found that 25% of respondents had no difference in information. 10/38 people (26.3%) agreed to participate and were available for an in-depth interview. The main findings were: 1) a very low response rate to the advertisement, 2) people in this community are willing to consider taking part in clinical research, but have different understandings of what that means, 3) there were discrepancies between online self-reported health and medication data and what was found in a pilot database of electronic public health records and during a face-to-face interview, 4) the reason for these differences, as perceived by participants, included forgetting some information, feeling it was not relevant or important to report because of the attributes of the online questionnaire and 5) these participants had no concerns about us accessing their electronic medical records. Conclusion: Our study provides some evidence for optimal places to advertise for an adult volunteer database, and the appropriate wording and format of both the advertisements and the online questionnaire. More efforts are needed to educate the general public on understand the meaning of clinical trials. Electronic medical records may be accessed to help understand potential participants’ eligibility for trials, but the feasibility of accessing such data timeously may need further negotiation.

Tuberculosis continues to claim millions of lives each year despite enormous efforts to control the epidemic over the past century. It remains the leading cause of death worldwide from a curable infectious disease. Tuberculosis is a significant cause of maternal mortality and morbidity, but little is known about the effect of pregnancy on anti-TB drugs concentrations. A critical challenge to the global efforts to control the tuberculosis epidemic is the spreading of drug resistance to first-line tuberculosis drugs. The treatment of drug-resistant tuberculosis relies on both new anti-tuberculosis agents such as bedaquiline, delamanid, and pretomanid and repurposed drugs, such as linezolid and clofazimine. In this thesis, we employed nonlinear mixed-effects modelling to evaluate the pharmacokinetics of first-line tuberculosis drugs isoniazid, pyrazinamide, and ethambutol in pregnancy. We assessed the pharmacokinetics and pharmacodynamics of pretomanid, clofazimine, and linezolid in African tuberculosis patients. Reassuringly, we found no significant pregnancy effect on the exposure of these antituberculosis agents, thus confirming the suitability of current doses in pregnancy. For pretomanid, we found that in spite of exposure being reduced by 44% with rifampicin coadministration, the drug levels were within the efficacy range observed in previous trials, provided that pretomanid doses are administered with food. Clofazimine exposure was found to accumulate more slowly in women, an effect driven by sex-related differences in the proportion of body fat. We characterised the effect of clofazimine concentration on QT interval prolongation. We investigated alternative dosing regimen to optimise clofazimine treatment and suggested that a 2-week loading dose may support treatment shortening by safely enabling more rapid attainment of efficacy targets. For linezolid model, we characterised population pharmacokinetic parameters in African tuberculosis patients, assessed probability of target attainment and related toxicity following different doses administration. We showed that population modelling could maximize information from collected data, and have a significant impact on advancing patients care especially in places with limited resources.

The global scale-up of tuberculosis treatment administered with antiretroviral therapy (ART) is the primary contributor to the 11 million averted deaths among individuals living with HIV observed between 2000 and 2019 in adults and children. Unfortunately, not all patients in need could fully benefit from these recent improvements in treatment because neglected populations are often excluded from clinical trials, including pregnant and breastfeeding women, children, adolescents, those with co-morbidities requiring additional drug treatments, and those with drug-resistant strains. This leaves many unanswered questions surrounding the management of TB, HIV, and TB/HIV in these vulnerable subpopulations. In this thesis, we utilise population pharmacokinetics and pharmacodynamic modelling to improve TB and HIV treatment in neglected populations using data from patients with TB or/and HIV. We analyse the pharmacogenomics, pharmacokinetics, and drug-drug interaction of efavirenz, isoniazid, and bedaquiline in pregnant women and characterise the pharmacokinetics and pharmacodynamics of high dose isoniazid in adults with multidrugresistant tuberculosis. We found that isoniazid and efavirenz exposures were reduced during pregnancy, but the main determinants of drug concentration were N-acetyltransferase 2 and CYP2B6 genotypes, which resulted in a 5-fold difference for both drugs between rapid and slow metabolisers. Bedaquiline exposures were lower during both postpartum and antepartum compared to historical data in non-pregnant patients. For high dose isoniazid, we observed markedly lower isoniazid exposures in participants on combination MDR-TB treatment compared to monotherapy and identified saturable kinetics at doses >10 mg/kg. We suggest that dosing isoniazid based on N-acetyltransferase 2 acetylator status might help patients attain effective exposures against inhA-mutated isolates.

Includes bibliographical references. / Sub-Saharan Africa is overwhelmed by dual epidemics of human immunodeficiency virus (HIV) and tuberculosis (TB) infection. Non-nucleoside reverse-transcriptase inhibitor (NNRTI)-based antiretroviral therapy (ART) is recommended for first-line treatment in adult HIV treatment programmes in resource-limited settings [1]. Many South African HIV-infected patients initiate ART while on TB treatment, 38 percent in one local study [2]. In addition, although ART reduces the incidence of TB, incidence in patients on ART is higher than in the HIV uninfected population [3], therefore incident TB on ART requiring concomitant treatment is very common. Efavirenz is regarded as the NNRTI of choice for TB co-infected patients [1] as outcomes are superior compared to those achieved with nevirapine-based ART [4] and concomitant TB treatment does not significantly reduce efavirenz concentrations [5]. However nevirapine is cheaper than efavirenz and is used extensively used in lower income countries with limited access to efavirenz [1]. Data characterising the extent to which concomitant rifampicin-based TB treatment decreases nevirapine plasma concentration therefore remain important.

Rationale Esomeprazole is a proton pump inhibitor with preclinical efficacy data showing it lowers concentrations of soluble fms like tyrosine kinase 1 (sFlt-1) and soluble endoglin (sEng), pathognomonic biomarkers identified in preeclampsia. A randomized controlled trial, Preeclampsia Intervention with Esomeprazole (PIE) trial, was conducted in South African women diagnosed with early-onset preeclampsia to investigate efficacy, but it found no change in clinical outcome or biomarker concentrations. It was hypothesized that the 40 mg daily oral dose was not enough to achieve therapeutic exposure. This study investigated the pharmacokinetics of esomeprazole in patients with early- onset preeclampsia with the aim to optimize the dose for future clinical trials. Methods Pharmacokinetic data from ten pregnant patients with early-onset preeclampsia from the PIE trial, median (range) age 30 (21-43) years, weight 98.8 (56-126) kg, and gestational age 29 (26- 31) weeks, were included for model development. In addition, pharmacokinetic data from non- pregnant healthy volunteers consisted of a pooled dataset of 26 male and female subjects, median (range) age of 21 (18-27) years and weight 69 (54-89) kg, who received 40 mg esomeprazole daily. Analysis of the pharmacokinetic data in pregnant patients was performed using nonlinear mixed-effects modelling with allometric scaling on clearance (CL) and volume of distribution (Vd). Metabolite to parent area under the time-concentration curve (AUCsulf/AUCeso and AUChyd/AUCeso) ratios were compared between pregnant and non-pregnant to assess metabolic changes in pregnancy. Simulations were performed with the model to determine the nonlinear increase in AUC with higher doses and with repeated dosing in the pregnant patients. Simulation results were compared with the preclinical target unbound concentration (0.917 mg/L) and preclinical target unbound AUC0-24 (9.29 mg·h/L). Results A one compartment pharmacokinetic model with first-order elimination and transit compartment absorption best described the data. Model estimated apparent CL and apparent Vd (95% CI) were 19.2 (14.2-26) L/h and 44.2 (29.9-56.6) L, respectively. Median AUCsulf/AUCeso (IQR) for pregnant patients, 2.00 (1.35-2.61) , was significantly higher than that for non-pregnant subjects on day1, 0.700 (0.636-1.00) , and day5, 1.18 (0.981- 1.58) . Median AUChyd/AUCeso (IQR) for pregnant patients, 0.0543 (0.0500-0.0914) , was not significantly different from that of non-pregnant subjects on day5, 0.0777 (0.0569-0.108) but lower than that of non-pregnant subjects on day1, 0.188 (0.156- 0.227). Simulation results showed that predicted steady state unbound Cmax is between 0.0949 and 0.398 mg/L while the predicted unbound AUC0-24 in pregnant patients with the highest dose of esomeprazole used clinically, i.e.120 mg BID, is between 0.696 and 2.92 mg·h/L. Discussion/Conclusion Model estimated CL/F and Vd/F are higher than values previously reported by other population pharmacokinetic models. AUCm/AUCp comparisons showed that esomeprazole metabolism in pregnancy appears to have shifted to the CYP3A4 pathway. This means that the nonlinear AUC increase expected with dose escalation and with repeated dosing are not as significant as in nonpregnant. Simulations indicate that pregnant patients are unlikely to achieve the target concentration and exposure with the highest dose of esomeprazole registered. Further research is necessary to determine the target site of action of esomeprazole in preeclampsia, and the pharmacokinetic metric that correlates with efficacy.

Background: Among individuals treated for HIV-1 infection, renal toxicity is more likely with tenofovir disoproxil fumarate (TDF) than with tenofovir alafenamide (TAF). Limited previous studies suggest potential genetic associations with TDF-associated renal toxicity. We hypothesized that polymorphisms in genes of potential relevance to tenofovir, TDF and TAF disposition are associated with renal toxicity in people living with HIV in Southern Africa. Material and Methods: Adult participants randomized to initiate TAF or TDF (each given with emtricitabine) in the dolutegravir arms of the ADVANCE trial had the option to co-enrol in a pharmacogenetic sub-study. We assessed changes from week 4 (to minimize impact of early dolutegravir-induced increases in creatinine) to week 48 in estimated glomerular filtration rate (eGFRCKD-EPI), and log-transformed changes from baseline to week 48 in urine retinol binding protein and urine β2-microglobulin, each adjusted for urinary creatinine (uRBP/Cr and uB2M/Cr, respectively). Genotyping was done using Illumina MEGAEX, followed by imputation with TOPMed. Genetic associations with each renal outcome (eGFR, uRBP/Cr and uB2M/Cr) were assessed using multivariable linear regression models adjusting for age, sex, treatment group, and screening body mass index, CD4 count, and log10 HIV-1 RNA. Primary analyses prioritized 14 polymorphisms previously reported to be associated with tenofovir disposition or renal tubular dysfunction, and all polymorphisms (+/- 50 kB) in selected genes of interest: ABCB1, ABCC2, ABCC4, ABCC10, ABCG2, AK2, AK3, CES1, CYP3A4, NME1, SLC22A2, SLC22A6, SLC22A8 and SLC22A11. We also explored associations genome-wide. Results: In ADVANCE, 336 participants randomized to either TAF or TDF consented to genetic testing. All were Black-African, 63% were female, median age was 32 years, CD4 count 292 cells/μL, and log10 HIV-1 RNA 4.4 copies/mL. Among the 14 polymorphisms of primary interest, the lowest Pvalues for change in eGFR, uRBP/Cr and uB2M/Cr were ABCC4 rs899494 (P = 0.021), ABCC10 rs2125739 (P = 0.07), and ABCC4 rs1059751 (P = 0.0087), respectively. Among genes of interest, the lowest P-values for change in eGFR, uRBP/Cr and uB2M/Cr were ABCC4 rs4148481 (P = 1.5x10-4 ), rs691857 (P = 3.2x10-4 ), and PKD2 rs72659631 (P = 8.6x10-4 ), respectively. In genome-wide analyses, the lowest P-values for change in eGFR, uRBP/Cr, and uB2M/Cr were COL27A1 rs1687402 (P = 3.2x10-9 ), CDH4 rs66494466 (P = 3.4 x 10-8 ), and ITGA4 rs3770126 (P = 4.5 x10-7 ), respectively. Conclusions: Among Southern African participants in a randomized trial of dolutegravir plus either TAF/emtricitabine or TDF/emtricitabine, two polymorphisms previously associated with TDF renal toxicity, ABCC4 rs899494 and ABCC4 rs1059751, were nominally associated with change in eGFR and uB2M/Cr, respectively, but did not withstand correction for multiple testing (nor did associations in genes of interest). A polymorphism in COL27A1, which encodes collagen type XXVII alpha 1 chain, was genome-wide associated with change in eGFR. These findings enhance our understanding of the impact of human genetics on tenofovir-associated renal toxicity.

Background: Dolutegravir, a component of the preferred first-line antiretroviral therapy (ART) regimen has been associated with increased weight gain, which is markedly higher when combined with tenofovir alafenamide (TAF), the newer tenofovir prodrug instead of tenofovir disoproxil fumarate (TDF). South Africa has a high prevalence of obesity, especially among women. Understanding dolutegravir exposure in the patients with obesity is important for dose optimisation. Aims: We compared the pharmacokinetic parameters of dolutegravir in Southern African adults living with HIV with and without obesity. Methods: Blood samples were collected at various time points over a 24 hour-period for dolutegravir assays. Non-compartmental analysis was conducted and geometric mean ratios (GMRs), with 90% confidence intervals (CIs), were generated to compare dolutegravir pharmacokinetic parameters between the groups. Regression analyses to assess predictors of dolutegravir exposure were done. Results: 40 participants were enrolled, 26 were women and 10 had obesity. Dolutegravir area under the concentration-time curve to 24-hours (AUC0-24hr) and the maximum concentrations (Cmax) were marginally lower in participants with obesity: GMR 0.91 (90% CI, 0.71-1.16) and GMR 0.86 (90% CI, 0.68-1.07), respectively. In a multivariate linear regression analysis adjusting for age, sex, body mass index (BMI), creatinine clearance and randomisation arm (TAF or TDF), a unit increase in BMI was associated with 1.2% lower dolutegravir AUC0-24h, (P = 0.035). Conclusion: Dolutegravir exposure was marginally lower in participants with obesity, but this is not clinically significant. Our findings suggest that there is no need to dose adjust dolutegravir in people with obesity.