Publications by authors named "Collen Masimirembwa"

Differences in the cervicovaginal microbiome may influence the persistence of HPV and therefore, the progression to cervical cancer. We aimed to analyze and compare the metatranscriptome of cervical cancers positive for HPV 16 and 18 with those positive for other HPV types to understand the microbiome's influence on oncogenicity. RNA sequencing data from a total of 222 invasive cervical cancer cases (HPV16/18 positive (n=42) and HPV "Other types" (n=180)) were subjected to taxonomy classification (Kraken 2) including bacteria, virus and fungi to the level of species.

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The advent of single-cell resolution sequencing and spatial transcriptomics has enabled the delivery of cellular and molecular atlases of tissues and organs, providing new insights into tissue health and disease. However, if the full potential of these technologies is to be equitably realised, ancestrally inclusivity is paramount. Such a goal requires greater inclusion of both researchers and donors in low- and middle-income countries (LMICs).

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Lack of equitable representation of global genetic diversity has hampered the implementation of genomic medicine in under-represented populations, including those on the African continent. Data from the multi-national Pre-emptive Pharmacogenomic Testing for Preventing Adverse Drug Reactions (PREPARE) study suggest that genotype guidance for prescriptions reduced the incidence of clinically relevant adverse drug reactions (ADRs) by 30%. In this study, hospital dispensary trends from a tertiary South African (SA) hospital (Steve Biko Academic Hospital; SBAH) were compared with the drugs monitored in the PREPARE study.

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We analyzed parentage data collected over a ten-year period in a Zimbabwean DNA testing laboratory. Parentage case types, prevalence, exclusion data, mutations rates and observed genotyping irregularities were analyzed. We report analysis results from 1303 cases.

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  • - The study examined how genetic variations in the CYP2D6 enzyme affect the pharmacokinetics of dextromethorphan and desipramine in healthy African volunteers, dividing subjects into three genetic cohorts.
  • - Results showed that participants with CYP2D6*17*17 and CYP2D6*29*29 genotypes exhibited significantly higher drug exposure levels compared to those with the CYP2D6*1/*2 variant, indicating they metabolize these medications much slower.
  • - Mild adverse effects were reported, with one instance of a moderately severe headache in a CYP2D6*17*17 individual, highlighting the need for careful dosage adjustments of CYP2D6-related drugs in African populations.
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Pharmacogenomic testing may be used to improve treatment outcomes and reduce the frequency of adverse drug reactions (ADRs). Population specific, targeted pharmacogenetics (PGx) panel-based testing methods enable sensitive, accurate and economical implementation of precision medicine. We evaluated the analytical performance of the GenoPharm® custom open array platform which evaluates 120 SNPs across 46 pharmacogenes.

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Pharmaceutical companies subject all new molecular entities to a series of in vitro metabolic characterizations that guide the selection and/or design of compounds predicted to have favorable pharmacokinetic properties in humans. Current drug metabolism research is based on liver tissue predominantly obtained from people of European origin, with limited access to tissue from people of African origin. Given the interindividual and interpopulation genomic variability in genes encoding drug-metabolizing enzymes, efficacy and safety of some drugs are poorly predicted for African populations.

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Dapsone is employed for both non-dermatological and dermatological indications but with non-existent population pharmacokinetics (popPK) data in Nigerians. This study was therefore designed to develop a popPK model in Nigerians. Non-compartmental analysis and nonlinear mixed effects modelling were utilized for data analysis.

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  • - A study was conducted to see if clinical guidelines for warfarin dosing could be practically applied to black Zimbabwean patients.
  • - Out of 62 patients, 62.90% did not get the recommended starting dose of warfarin according to guidelines from the Clinical Pharmacogenetics Implementation Consortium (CPIC).
  • - CPIC guidelines consider African-specific genetic variations, making them more suitable for Zimbabwean patients compared to US FDA and Dutch guidelines, which do not account for these variants.
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  • * A study involving 40 breast cancer patients in Zimbabwe found that many had genetic variants (polymorphisms) in CYP2D6 that affect drug metabolism, leading to lower endoxifen levels.
  • * Results showed that 55% of participants had endoxifen concentrations below the therapeutic threshold, highlighting a significant relationship between CYP2D6 genetic variations and endoxifen levels (with specific statistical significance).
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Pain is a common cause of hospitalization in sickle cell disease (SCD) patients. Failure to effectively control pain remains a challenge in patient care. The authors conducted a cross-sectional study to determine the effect of and polymorphisms on pain management in 106 Zimbabwean SCD patients.

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6-mercaptopurine usage is associated with myelotoxicity and increased risk in patients carrying metabolism-related genetic variations. This study aimed to determine the frequency of candidate gene polymorphisms and their association with 6-mercaptopurine intolerance. A total of 41 patients on acute lymphoblastic leukaemia treatment were genotyped for and  (rs116855232) alleles, and their association with dose intensity was analyzed.

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Fluoropyrimidines are commonly used in the treatment of colorectal cancer. They are, however, associated with adverse events (AEs), of which gastrointestinal, myelosuppression and palmar-plantar erythrodysesthesia are the most common. Clinical guidelines are used for fluoropyrimidine dosing based on dihydropyrimidine dehydrogenase () genetic polymorphism and have been shown to reduce these AEs in patients of European ancestry.

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  • Clinical outcomes of tamoxifen (TAM) treatment show high variability among individuals, influenced by genetic differences and other medications.
  • A study involving 229 South African Black women with breast cancer found that certain genetic variants (CYP2D6*17 and CYP2D6*29) significantly impact the metabolism of TAM and its active metabolites.
  • While antiretroviral therapy affected certain metabolite levels of TAM, the overall risk of significant drug interactions was considered low for patients undergoing TAM treatment.
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Tamoxifen (TAM) is widely used in the treatment of hormone receptor-positive breast cancer. TAM is metabolized into the active secondary metabolite endoxifen (ENDO), primarily by CYP2D6. We aimed to investigate the effects of an African-specific variant allele, 17, on the pharmacokinetics (PK) of TAM and its active metabolites in 42 healthy black Zimbabweans.

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Aims: Doxorubicin-induced cardiotoxicity (DIC) is a significant cause of mortality in cancer care. This study was conducted to establish the frequency of DIC in Zimbabwean breast cancer patients on doxorubicin and to test the DIC predictive power of genetic biomarkers.

Methods: A cohort of 50 Zimbabwean breast cancer patients treated with doxorubicin were followed up for 12 months with serial echocardiography and genotyped for UGTA1A6*4, SLC28A3 and RARG.

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Purpose: Women living with HIV (WLWH) and breast cancer (BC) have worse overall survival than HIV-negative women with BC, and poor adherence to prescribed tamoxifen is known to contribute to poor survival. We therefore investigated the association of HIV infection with adherence to adjuvant tamoxifen among women with localized hormone receptor (HR)-positive breast cancer in South Africa.

Methods: Among 4,097 women diagnosed with breast cancer at six hospitals in the prospective South African Breast Cancer and HIV Outcomes (SABCHO) cohort study between July 2015 and December 2020, we focused on black women with stages I-III HR-positive breast cancer who were prescribed 20 mg of adjuvant tamoxifen daily.

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The major challenges that delay the implementation of pharmacogenomics based clinical practice in the developing countries, primarily the low- and middle-income countries need to be recognized. This review was conducted to systematically review evidence of the cost-effectiveness for the conduct of pharmacogenomics testing in the developing countries. Studies that evaluated the cost-effectiveness of pharmacogenomics testing in the developing countries as defined by the United Nations were included in this study.

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Objective: Pharmacogenomics (PGx) is a clinically significant factor in the safe and efficacious use of medicines. While PGx knowledge is abundant for other populations, there are scarce PGx data on African populations and is little knowledge on drug-gene interactions for medicines used to treat diseases common in Africa. The aim of this study was to use a custom-designed open array to genotype clinically actionable variants in a Zimbabwean population.

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Pharmacogenomics is universally relevant for worldwide modern therapeutics and yet needs further development in resource-limited countries. While there is an abundance of genetic association studies in controlled medical settings, there is a paucity of studies with a naturalistic design in real-life clinical practice in patients with comorbidities and under multiple drug treatment regimens. African patients are often burdened with communicable and noncommunicable comorbidities, yet the application of pharmacogenomics in African clinical settings remains limited.

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Adverse drug reactions (ADRs) are one of the major causes of morbidity and mortality worldwide. It is well-known that individual genetic make-up is one of the causative factors of ADRs. Approximately 14 million single nucleotide polymorphisms (SNPs) are distributed throughout the entire human genome and every patient has a distinct genetic make-up which influences their response to drug therapy.

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  • Chloroquine and hydroxychloroquine are being discussed as potential COVID-19 treatments, but they carry warnings for individuals with G6PD deficiency.
  • Analysis of genetic data from 458 individuals in sub-Saharan Africa revealed significant variations in the G6PD gene, identifying nine variants, including one (rs1050828) known to cause G6PD deficiency.
  • The presence of these variants, particularly the common rs1050828, suggests that genetic differences among African sub-populations could impact clinical trials of these drugs for COVID-19.
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In this study, we aimed to evaluate the utility of endogenous 1β-hydroxy-deoxycholic acid/total deoxycholic acid ratio (1β-OH-DCA/ToDCA) in spot urine as a surrogate marker of cytochrome P450 3A (CYP3A) activity in the assessment inhibition-based drug-drug interactions in healthy volunteers. This was accomplished through an open-label, three-treatment parallel-arm study in healthy male volunteers from Zimbabwe. Each group received itraconazole (ITZ; 100 mg once daily; = 10), fluconazole (FKZ; 50 mg once daily; = 9), or alprazolam (APZ; 1 mg once daily; = 8) orally.

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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.

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Sub-Saharan Africa and other low- and middle-income countries (LMICs) have the highest rates of antimicrobial resistance (AMR) driven by high rates of antimicrobial utilization. This is a concern as AMR appreciably increases morbidity, mortality and costs. Pharmacogenetics (PGx) and precision medicine are emerging approaches to combat AMR.

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