Development and application of methods for pharmacokinetics (PK) analysis in PNG HIV/AIDS patients

Abstract

HIV is an infectious disease affecting millions of people around the world, mainly in low-income countries (e.g. Papua New Guinea-PNG). HIV has become a lifelong chronic disease, so treatment should be readily managed. Nevertheless, antiretrovirals have noted side effects, often with narrow therapeutic ranges and high variability between and within patients, which makes them good candidates for Therapeutic Drug Monitoring (TDM). Variability in drug concentrations can be due to non-genetic and genetic factors, therefore their study is required to ensure the patient is getting maximum benefits and minimum negative outcomes from the drug use. PNG has a high prevalence of HIV and unique pharmacogenetics profile, however nothing is known on pharmacokinetics or adverse effects. Therefore, studying this population is important to ensure maximum benefits of the treatment are achieved. TDM requires precise, accurate and selective methods for quantification of the drugs, so Chapter 2, describes the development and validation of a method for the quantification of efavirenz (EFV) and metabolites, showing for the first time the significant instability of two metabolites in plasma samples at high temperatures (samples are heated for virus inactivation). Chapter 3 investigated if CYP2B6 c.516T allele and demographic factors affected plasma EFV and 8-hydroxy-EFV variability, and their association with adverse effects in 156 HIV/AIDS patients from PNG. The frequency of 516T allele was 53%. Genotype per se explained 38% of EFV variability and all patients with EFV plasma concentrations above the therapeutic range (> 4 μg mL-1) carried the TT genotype. Even though c.516TT genotype is a strong predictor of high plasma EFV concentrations, it did not translate into increased incidence of side effects, most likely due to drug tolerance. The current first-line treatment for HIV in PNG consists of a combination of dolutegravir (DTG), tenofovir (TNF) and lamivudine (3TC). Simultaneous drug analysis saves time and consumables, so Chapter 4 reports an attempt at the simultaneous quantification of TNF, 3TC and DTG. Due to differences in chemical properties of the drugs, two separate methods had to be developed. Besides the development and validation of a method to simultaneously quantify TNF and 3TC, Chapter 5 brings the application of the developed assay in PNG HIV patients and the association of TNF and 3TC plasma concentrations variability with demographic factors and patient’s kidney function. The method was successfully applied to 121 patient samples and only a small proportion (TNF 8 %, 3TC 6 %) of the variability was explained by these parameters. Chapter 6 describes the development of an assay to quantify DTG in microsampling devices, which are used as an alternative to conventional sampling (venous blood), particularly for their advantage regarding to transportation of samples. In summary, methods for the quantification of HIV drugs in biological samples were developed and validated. Association of genetic and non-genetic factors with drug concentration variability was explored, however most of the variability was not explained by the parameters investigated. Therefore, future studies are needed to explore novel factors to predict HIV drug concentrations variability and its association with side effects.