Integration of In Silico and In Vitro ADMET properties in lead identification and optimization of compounds for the treatment of parasitic diseases

Parasitic infections are the major causes of illness and death in tropical regions especially in Africa. The main parasitic diseases include leishmaniasis, filariasis, malaria, river blindness, Chagas disease and schistosomiasis. With the absence of vaccines, treatment relies mainly on chemotherapy hence the need for efficacious and safe medicines. Many of the medicines currently used have low efficacy and cause side effects. Some are also being lost to drug resistance. To address the inadequacy of treatment options for infectious diseases, a number of initiatives have been started to promote drug discovery and development in Africa. In parallel they have been collaboration between African institutions and leading pharmaceutical companies as well as other relevant R & D organizations. This has led to the need to modernize African approaches to drug discovery and development with respect to the integration of medicinal chemistry, pharmacology and pharmacokinetics as reflected in the processes of Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET). However, scientific and technological expertise in pharmacokinetics for drug discovery is under developed in Africa

DNA paternity testing in Zimbabwe - Emerging paternal discrepancy trends and demographic patterns

Paternal discrepancy is a major cause of marital and legal challenges in society. Data on its prevalence in most countries is however  limited. This study reviews 851 DNA paternity tests conducted from 2014 to 2019 using 16 and 21 STR marker kits on the Thermo Fisher platform in Zimbabwe. The average paternal discrepancy was 32.8 %, and of these cases 83.21 % were revealed through peace of mind tests whilst 16.79 % were court ordered tests. Of the 851 tests, 66.22 % were male children, suggesting stronger interest by social fathers in ascertaining paternity of males compared to females. The 31-44 years age group had the highest number of tested putative fathers. The age difference between the fathers and mothers was within the population average of 12.2 years. Trends observed provide baseline design data for research on the scientific, cultural, ethical and legal issues relating to paternity testing in Zimbabwe. Keywords: DNA test, paternity discrepancy, low paternity confidence&nbsp

OC 8510 BIOTRANSFORMATION OF PRAZIQUANTEL FOR THE PHARMACOKINETIC OPTIMISATION OF PRAZIQUANTEL USE IN MASS DRUG ADMINISTRATION AND DEVELOPMENT OF NEW PAEDIATRIC FORMULATIONS

BackgroundPraziquantel (PZQ) is the only drug available for the treatment of all forms of schistosomiasis. New paediatric formulations for the active enantiomer R-PZQ and the racemate PZQ are currently under development. There is however limited drug metabolism and pharmacokinetic data on PZQ available to support these initiatives. Detailed knowledge of PZQ metabolism will enable the use of PBPK modelling to determine appropriate doses for the new formulations in paediatric patients and to predict risks for drug-drug interactions in mass drug administration.MethodsBiotransformation studies on PZQ were conducted in human liver microsomes and recombinant Cytochrome P450s (CYPs). Structure elucidation was inferred from mass spectra. Enzyme kinetic studies to determine the Michaelis-Menten kinetics, Km and Vmax, of the formation of the main metabolites and analysis of clinical samples were determined by LC-MS/MS.ResultsCYP reaction phenotyping studies with HLM and r-CYPs indicate major involvement of CYP1A2, 2 C19, 2D6 and 3A4/5 in the metabolism of R- and S-PZQ. Biotransformation studies showed that PZQ is metabolised to cis-4-OH-PZQ mainly by CYP1A2 and CYP2C19. CYP3A4/5 metabolises PZQ to a mono-hydroxyl metabolite (X-OH-PZQ) whilst CYP2D6 metabolises PZQ to minor novel mono-hydroxyl metabolite (Y-OH-PZQ) both pending structural elucidation by nuclear magnetic resonance. R-PZQ was more rapidly cleared than S–PZQ with variable interindividual AUC and Cmax.Discussion and conclusionThe differential role of CYP1A2 and CYP2C19 and of CYP3A4 and CYP3A5 in the formation the 4-OH-PZQ and the novel X-OH-PZQ respectively are intriguing findings as this has not been reported before in humans. In vitro, cis and not trans 4-OH-PZQ formation has been observed contrary in vivo reports in humans which indicate trans 4-OH-PZQ as the main metabolite. The data will enable us to understand the rapid clearance of PZQ and predict potential drug-drug-gene interactions which mayexplain the inter-individual variability of PZQ pharmacokinetics

Community burden of undiagnosed HIV infection among adolescents in Zimbabwe following primary healthcare-based provider-initiated HIV testing and counselling: A cross-sectional survey.

BACKGROUND: Children living with HIV who are not diagnosed in infancy often remain undiagnosed until they present with advanced disease. Provider-initiated testing and counselling (PITC) in health facilities is recommended for high-HIV-prevalence settings, but it is unclear whether this approach is sufficient to achieve universal coverage of HIV testing. We aimed to investigate the change in community burden of undiagnosed HIV infection among older children and adolescents following implementation of PITC in Harare, Zimbabwe. METHODS AND FINDINGS: Over the course of 2 years (January 2013-January 2015), 7 primary health clinics (PHCs) in southwestern Harare implemented optimised, opt-out PITC for all attendees aged 6-15 years. In February 2015-December 2015, we conducted a representative cross-sectional survey of 8-17-year-olds living in the 7 communities served by the study PHCs, who would have had 2 years of exposure to PITC. Knowledge of HIV status was ascertained through a caregiver questionnaire, and anonymised HIV testing was carried out using oral mucosal transudate (OMT) tests. After 1 participant taking antiretroviral therapy was observed to have a false negative OMT result, from July 2015 urine samples were obtained from all participants providing OMTs and tested for antiretroviral drugs to confirm HIV status. Children who tested positive through PITC were identified from among survey participants using gender, birthdate, and location. Of 7,146 children in 4,251 eligible households, 5,486 (76.8%) children in 3,397 households agreed to participate in the survey, and 141 were HIV positive. HIV prevalence was 2.6% (95% CI 2.2%-3.1%), and over a third of participants with HIV were undiagnosed (37.7%; 95% CI 29.8%-46.2%). Similarly, among the subsample of 2,643 (48.2%) participants with a urine test result, 34.7% of those living with HIV were undiagnosed (95% CI 23.5%-47.9%). Based on extrapolation from the survey sample to the community, we estimated that PITC over 2 years identified between 18% and 42% of previously undiagnosed children in the community. The main limitation is that prevalence of undiagnosed HIV was defined using a combination of 3 measures (OMT, self-report, and urine test), none of which were perfect. CONCLUSIONS: Facility-based approaches are inadequate in achieving universal coverage of HIV testing among older children and adolescents. Alternative, community-based approaches are required to meet the Joint United Nations Programme on HIV/AIDS (UNAIDS) target of diagnosing 90% of those living with HIV by 2020 in this age group

Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial.

BACKGROUND: Child stunting reduces survival and impairs neurodevelopment. We tested the independent and combined effects of improved water, sanitation, and hygiene (WASH), and improved infant and young child feeding (IYCF) on stunting and anaemia in in Zimbabwe. METHODS: We did a cluster-randomised, community-based, 2 × 2 factorial trial in two rural districts in Zimbabwe. Clusters were defined as the catchment area of between one and four village health workers employed by the Zimbabwe Ministry of Health and Child Care. Women were eligible for inclusion if they permanently lived in clusters and were confirmed pregnant. Clusters were randomly assigned (1:1:1:1) to standard of care (52 clusters), IYCF (20 g of a small-quantity lipid-based nutrient supplement per day from age 6 to 18 months plus complementary feeding counselling; 53 clusters), WASH (construction of a ventilated improved pit latrine, provision of two handwashing stations, liquid soap, chlorine, and play space plus hygiene counselling; 53 clusters), or IYCF plus WASH (53 clusters). A constrained randomisation technique was used to achieve balance across the groups for 14 variables related to geography, demography, water access, and community-level sanitation coverage. Masking of participants and fieldworkers was not possible. The primary outcomes were infant length-for-age Z score and haemoglobin concentrations at 18 months of age among children born to mothers who were HIV negative during pregnancy. These outcomes were analysed in the intention-to-treat population. We estimated the effects of the interventions by comparing the two IYCF groups with the two non-IYCF groups and the two WASH groups with the two non-WASH groups, except for outcomes that had an important statistical interaction between the interventions. This trial is registered with ClinicalTrials.gov, number NCT01824940. FINDINGS: Between Nov 22, 2012, and March 27, 2015, 5280 pregnant women were enrolled from 211 clusters. 3686 children born to HIV-negative mothers were assessed at age 18 months (884 in the standard of care group from 52 clusters, 893 in the IYCF group from 53 clusters, 918 in the WASH group from 53 clusters, and 991 in the IYCF plus WASH group from 51 clusters). In the IYCF intervention groups, the mean length-for-age Z score was 0·16 (95% CI 0·08-0·23) higher and the mean haemoglobin concentration was 2·03 g/L (1·28-2·79) higher than those in the non-IYCF intervention groups. The IYCF intervention reduced the number of stunted children from 620 (35%) of 1792 to 514 (27%) of 1879, and the number of children with anaemia from 245 (13·9%) of 1759 to 193 (10·5%) of 1845. The WASH intervention had no effect on either primary outcome. Neither intervention reduced the prevalence of diarrhoea at 12 or 18 months. No trial-related serious adverse events, and only three trial-related adverse events, were reported. INTERPRETATION: Household-level elementary WASH interventions implemented in rural areas in low-income countries are unlikely to reduce stunting or anaemia and might not reduce diarrhoea. Implementation of these WASH interventions in combination with IYCF interventions is unlikely to reduce stunting or anaemia more than implementation of IYCF alone. FUNDING: Bill & Melinda Gates Foundation, UK Department for International Development, Wellcome Trust, Swiss Development Cooperation, UNICEF, and US National Institutes of Health.The SHINE trial is funded by the Bill & Melinda Gates Foundation (OPP1021542 and OPP113707); UK Department for International Development; Wellcome Trust, UK (093768/Z/10/Z, 108065/Z/15/Z and 203905/Z/16/Z); Swiss Agency for Development and Cooperation; US National Institutes of Health (2R01HD060338-06); and UNICEF (PCA-2017-0002)

The effect of the Pheroid delivery system on the in vitro metabolism and in vivo pharmacokinetics of artemisone

Objectives: The objectives were to determine the pharmacokinetics (PK) of artemisone and artemisone formulated in the Pheroid® drug delivery system in primates and to establish whether the formulation affects the in vitro metabolism of artemisone in human and monkey liver and intestinal microsomes. Methods: For the PK study, a single oral dose of artemisone was administered to vervet monkeys using a crossover design. Plasma samples were analyzed by means of liquid chromatography-tandem mass spectrometry. For the in vitro metabolism study, clearance was determined using microsomes and recombinant CYP3A4 enzymes, and samples were analyzed by means of ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry. Results: Artemisone and M1 plasma levels were unexpectedly low compared to those previously recorded in rodents and humans. The in vitro intrinsic clearance (CLint) of the reference formulation with monkey liver microsomes was much higher (1359.33 ± 103.24 vs 178.86 ± 23.42) than that of human liver microsomes. The in vitro data suggest that microsomal metabolism of artemisone is inhibited by the Pheroid delivery system. Conclusions: The in vivo results obtained in this study indicate that the Pheroid delivery system improves the PK profile of artemisone. The in vitro results indicate that microsomal metabolism of artemisone is inhibited by the Pheroid delivery systemSouth African Technology Innovation Agency (TIA), the Swiss South African Joint Research Project Initiative and the North-West Universit

Inhibitory effects of herbal medicines with claimed anticancer indications on cytochrome P450—An evaluation of drug-herb interactions risk

Herbs have the potential to interact with conventional medicines or each other upon concurrent administration. This can be at the level of absorption, distribution, metabolism and excretion (ADME). With an estimation that 80% of the population in poor regions of the world utilise herbal medicines for primary healthcare, there is a likelihood that some people will take both herbal and conventional medicines. This could present a risk for herb-drug interactions (HDI) at the various levels of the ADME process. Most common HDI have been observed at metabolism level involving inhibition or induction of the major drug metabolising liver enzymes called cytochrome P450s. In this study, we investigated the inhibitory effects of Parinari curatellifolia (MC), Fluggea virosa (ST), Garcinia livingstonei (MT), Pterocarpus angolensis (M), Tapinanthus quequensis (MF) and Cussonia arborea (GM) on recombinant CYP1A2, CYP2D6, CYP2C9 and CYP2C19. Plate based fluorescent assays were used to follow enzyme activity. Inhibition was determined at 5 mg/ml and 100 mg/ml of herbal extract, with IC50 determined for herbs that showed potent inhibition. A total of 10 out of 13 extracts showed significant inhibitory effects. Pterocarpus angolensis(bark), Fluggea virossa (leaf), Cussonia arborea(bark), Parinari curatellifollia (root) had very potent effects on CYP1A2 as indicated by an IC50 of <9.9 µg/ml. Based on the worst-case-scenario of complete absorption and exposure, these herbs are predicted to result in HDI if co-administered with medicines which depend on the affected CYPs for metabolism and elimination. Significance of the main findings: There is a potential threat of drug toxicities due to drug-herb interactions for patients undergoing chemotherapy or taking other medications where co-morbidities exist during chemotherapy. Drugs that are substrates of CYP1A2 should be administered with caution for patients who are taking the herbs which have been studied in this research as risk for drug toxicities may be high. The findings act as a guide to medical doctors and patients in evaluating potential for herb-drug interactions during prescribing medications which are substrates for the studied CYPs

Investigation of the differences in the pharmacokinetics of CYP2D6 substrates, desipramine and dextromethorphan in healthy African subjects carrying the allelic variants CYP2D6*17 and CYP2D6*29 when compared with normal metabolizers

This study investigated the differences in the pharmacokinetics (PK) of dextromethorphan and desipramine in African healthy volunteers to understand the effect of allelic variants of the human cytochrome-P450(CYP)2D6 enzyme namely, CYP2D6*1/*2 diplotypes, CYP2D6*17*17 and CYP2D6*29*29 genotypes. Overall, 28 adults were included through genotype screening into the three cohorts: CYP2D6*1/*2 (n=12), CYP2D6*17*17 (n=12), and CYP2D6*29*29 (n=4). Each subject received a single oral dose of dextromethorphan 30-mg syrup on Day 1 and desipramine 50-mg tablet on Day 8. The PK parameters, area under plasma concentration-time curve from time of dosing to time of last quantifiable concentration (AUClast) and extrapolated to infinity (AUCinf), and maximum plasma concentration (Cmax) were determined. For both dextromethorphan and desipramine, AUCinf and Cmax were higher in subjects of the CYP2D6*29*29 and CYP2D6*17*17 cohorts as compared with those reported in the CYP2D6*1/*2 diplotype cohort, and for normal metabolizers in literature. All PK parameters including AUCinf, Cmax, and elimination half-life followed a similar trend: CYP2D6*17*17 >CYP2D6*29*29 >CYP2D6*1/*2. The plasma and urinary drug/metabolite exposure ratios of both drugs were higher in subjects of the CYP2D6*17*17 and CYP2D6*29*29 cohorts when compared with those in the CYP2D6*1/*2 diplotype cohort. All adverse events were mild, except for one subject with CYP2D6*17*17 who had moderately severe headache with desipramine. These results indicated that subjects with CYP2D6*17*17 and CYP2D6*29*29 genotypes were 5–10 times slower metabolizers than those with CYP2D6*1/*2 diplotypes. These findings suggest that dose optimization may be required when administering CYP2D6 substrate drugs in African patients. Larger studies can further validate these findings

Clinically relevant enantiomer specific R‐ and S‐praziquantel pharmacokinetic drug‐drug interactions with efavirenz and ritonavir

Abstract We conducted a clinical study to determine the effect of efavirenz and ritonavir on the pharmacokinetics of R‐ and S‐PZQ in healthy male participants. This was toward evaluating the risk of drug‐drug interactions, which may occur after PZQ administration to HIV patients on efavirenz or ritonavir containing regimens. A non‐randomized, open‐label, single‐dose, one sequence crossover study with 2 arms was conducted. We gave 26 healthy volunteers a single oral dose of 40 mg/kg PZQ followed by a daily oral dose of either 400 mg efavirenz or 100 mg ritonavir for 14 consecutive days. On day 14, they ingested a single 40 mg/kg dose of PZQ. We measured plasma levels up to 12 h on day 1 and day 14. Samples were analyzed by LC‐MS. Pharmacokinetic analysis was conducted in WinNonlin to determine the primary endpoints (plasma T1/2, Cmin, and AUC). Efavirenz had a significant effect on the pharmacokinetics of PZQ (p < .05), reducing the AUC by 4‐fold (1213.15 vs. 281.35 h·ng/ml for R‐PZQ and 5669 vs. 871.84 h·ng/ml for S‐PZQ). Ritonavir had no significant effect on R‐PZQ but increased the AUC 2‐fold for S‐PZQ (p < .05) (4154.79 vs. 7291.05 h·ng/ml). Using PZQ in HIV patients needs investigation, as there is a risk of both treatment failure and adverse effects because of induction and inhibition, respectively