Effects of Khat (Catha edulis) use on catalytic activities of major drug-metabolizing cytochrome P450 enzymes and implication of pharmacogenetic variations

En un estudio cruzado unidireccional, investigamos el efecto del Khat, una planta psicoestimulante natural similar a las anfetaminas, en las actividades catalíticas de cinco importantes enzimas del citocromo P450 (CYP) que metabolizan las drogas. Tras una semana de abstinencia de Khat, se fenotipó a 63 varones voluntarios etíopes utilizando drogas de sonda de cóctel (cafeína, losartán, dextrometorfano, omeprazol). El fenotipado se repitió después de una semana de uso diario de 400 g de hojas frescas de Khat. Se hizo el genotipado para CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A5. Se cuantificaron las concentraciones de catinona y fenilpropanolamina urinarias, y de drogas de sonda de plasma y metabolitos mediante LC-MS/MS. Se evaluó el efecto del Khat en las actividades enzimáticas comparando las proporciones metabólicas (MR) de cafeína/paraxantina (CYP1A2), losartán/ácido carboxílico losartán (CYP2C9), omeprazol/5-hidroxiomeprazol (CYP2C19), dextrometorfano/dextrorfano (CYP2D6) y dextrometorfano/3-metoximorfano (CYP3A4) antes y después del uso del Khat. La prueba del par de Wilcoxon indicó un aumento significativo en la mediana de la RM de CYP2D6 (41%, p < 0,0001), y un aumento marginal en la RM de CYP3A4 y CYP2C19 por el Khat. La medida repetida ANOVA indicó el impacto del genotipo CYP1A2 y CYP2C19 en las interacciones de las enzimas Khat-CYP. La mediana de la RM aumentó un 35% en CYP1A2*1/*1 (p = 0,07) y un 40% en los portadores de alelos CYP2C19 defectuosos (p = 0,03). Las proporciones logarítmicas de catinona/fenilpropanolamina en la orina se correlacionaron significativamente con el genotipo CYP2D6 (p = 0,004) y la RM de CYP2D6 (p = 0,025). El khat inhibe significativamente el CYP2D6, inhibe marginalmente el CYP3A4 y, dependiendo del genotipo, inhibe las actividades enzimáticas del CYP2C19 y el CYP1A2.In a one-way cross-over study, we investigated the effect of Khat, a natural amphetamine-like psychostimulant plant, on catalytic activities of five major drug-metabolizing cytochrome P450 (CYP) enzymes. After a one-week Khat abstinence, 63 Ethiopian male volunteers were phenotyped using cocktail probe drugs (caffeine, losartan, dextromethorphan, omeprazole). Phenotyping was repeated after a one-week daily use of 400 g fresh Khat leaves. Genotyping for CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP3A5 were done. Urinary cathinone and phenylpropanolamine, and plasma probe drugs and metabolites concentrations were quantified using LC-MS/MS. Effect of Khat on enzyme activities was evaluated by comparing caffeine/paraxanthine (CYP1A2), losartan/losartan carboxylic acid (CYP2C9), omeprazole/5-hydroxyomeprazole (CYP2C19), dextromethorphan/dextrorphan (CYP2D6) and dextromethorphan/3-methoxymorphinan (CYP3A4) metabolic ratios (MR) before and after Khat use. Wilcoxon-matched-pair-test indicated a significant increase in median CYP2D6 MR (41%, p < 0.0001), and a marginal increase in CYP3A4 and CYP2C19 MR by Khat. Repeated measure ANOVA indicated the impact of CYP1A2 and CYP2C19 genotype on Khat-CYP enzyme interactions. The median MR increased by 35% in CYP1A2*1/*1 (p = 0.07) and by 40% in carriers of defective CYP2C19 alleles (p = 0.03). Urinary log cathinone/phenylpropanolamine ratios significantly correlated with CYP2D6 genotype (p = 0.004) and CYP2D6 MR (P = 0.025). Khat significantly inhibits CYP2D6, marginally inhibits CYP3A4, and genotype-dependently inhibit CYP2C19 and CYP1A2 enzyme activities.• Swedish Research Council. Proyecto VR 2015–03295 • Instituto de Salud Carlos III-Sara Borrell. Programa CD13/00348, para Fernando de Andrés SegurapeerReviewe

Early or deferred initiation of efavirenz during rifampicin‐based TB therapy has no significant effect on CYP3A induction in TB‐HIV infected patients

Background and Purpose: In TB‐HIV co‐infection, prompt initiation of TB therapy is recommended but anti‐retroviral treatment (ART) is often delayed due to potential drug–drug interactions between rifampicin and efavirenz. In a longitudinal cohort study, we evaluated the effects of efavirenz/rifampicin co‐treatment and time of ART initiation on CYP3A induction. / Experimental Approach: Treatment‐naïve TB‐HIV co‐infected patients (n = 102) were randomized to efavirenz‐based‐ART after 4 (n = 69) or 8 weeks (n = 33) of commencing rifampicin‐based anti‐TB therapy. HIV patients without TB (n = 94) receiving efavirenz‐based‐ART only were enrolled as control. Plasma 4β‐hydroxycholesterol/cholesterol (4β‐OHC/Chol) ratio, an endogenous biomarker for CYP3A activity, was determined at baseline, at 4 and 16 weeks of ART. / Key Results: In patients treated with efavirenz only, median 4β‐OHC/Chol ratios increased from baseline by 269% and 275% after 4 and 16 weeks of ART, respectively. In TB‐HIV patients, rifampicin only therapy for 4 and 8 weeks increased median 4β‐OHC/Chol ratios from baseline by 378% and 576% respectively. After efavirenz/rifampicin co‐treatment, 4β‐OHC/Chol ratios increased by 560% of baseline (4 weeks) and 456% of baseline (16 weeks). Neither time of ART initiation, sex, genotype nor efavirenz plasma concentration were significant predictors of 4β‐OHC/Chol ratios after 4 weeks of efavirenz/rifampicin co‐treatment. / Conclusion and Implications: Rifampicin induced CYP3A more potently than efavirenz, with maximum induction occurring within the first 4 weeks of rifampicin therapy. We provide pharmacological evidence that early (4 weeks) or deferred (8 weeks) ART initiation during anti‐TB therapy has no significant effect on CYP3A induction

Role of pharmacogenetics in rifampicin pharmacokinetics and the potential effect on TB–rifampicin sensitivity among Ugandan patients

BACKGROUND: Suboptimal anti-TB drugs exposure may cause multidrug-resistant TB. The role of African predominant SLCO1B1 variant alleles on rifampicin pharmacokinetics and the subsequent effect on the occurrence of Mycobacterium tuberculosis-rifampicin sensitivity needs to be defined. We describe the rifampicin population pharmacokinetics profile and investigate the relevance of SLCO1B1 genotypes to rifampicin pharmacokinetics and rifampicin-TB sensitivity status. METHODS: Fifty patients with TB (n=25 with rifampicin-resistant TB and n=25 with rifampicin-susceptible TB) were genotyped for SLOC1B1 rs4149032 (g.38664C>T), SLOC1B1*1B (c.388A>G) and SLOC1B1*5 (c.521 T>C). Steady state plasma rifampicin levels were determined among patients infected with rifampicin-sensitive TB. Data were analysed using NONMEM to estimate population rifampicin pharmacokinetics as well as the effect of SLOC1B1 genotypes on rifampicin pharmacokinetics and on rifampicin-TB sensitivity status. RESULTS: Overall allele frequencies of SLOC1B1 rs4149032, *1B and *5 were 0.66, 0.90 and 0.01, respectively. Median (IQR) Cmax and Tmax were 10.2 (8.1-12.5) mg/L and 1.7 (1.125-2.218) h, respectively. Twenty-four percent of patients exhibited Cmax below the recommended 8-24 mg/L range. SLOC1B1 genotypes, gender and age did not influence rifampicin pharmacokinetics or TB-rifampicin sensitivity. CONCLUSIONS: Although SLOC1B1 genotype, age and gender do not influence either rifampicin pharmacokinetics or rifampicin-TB sensitivity status, one in every four Ugandan TB patients achieve subtherapeutic plasma rifampicin concentrations

Liver Enzyme Abnormalities and Associated Risk Factors in HIV Patients on Efavirenz-Based HAART with or without Tuberculosis Co-Infection in Tanzania.

To investigate the timing, incidence, clinical presentation, pharmacokinetics and pharmacogenetic predictors for antiretroviral and anti-tuberculosis drug induced liver injury (DILI) in HIV patients with or without TB co-infection. A total of 473 treatment naïve HIV patients (253 HIV only and 220 with HIV-TB co-infection) were enrolled prospectively. Plasma efavirenz concentration and CYP2B6*6, CYP3A5*3, *6 and *7, ABCB1 3435C/T and SLCO1B1 genotypes were determined. Demographic, clinical and laboratory data were collected at baseline and up to 48 weeks of antiretroviral therapy. DILI case definition was according to Council for International Organizations of Medical Sciences (CIOMS). Incidence of DILI and identification of predictors was evaluated using Cox Proportional Hazards Model. The overall incidence of DILI was 7.8% (8.3 per 1000 person-week), being non-significantly higher among patients receiving concomitant anti-TB and HAART (10.0%, 10.7 per 1000 person-week) than those receiving HAART alone (5.9%, 6.3 per 1000 person-week). Frequency of CYP2B6*6 allele (p = 0.03) and CYP2B6*6/*6 genotype (p = 0.06) was significantly higher in patients with DILI than those without. Multivariate cox regression model indicated that CYP2B6*6/*6 genotype and anti-HCV IgG antibody positive as significant predictors of DILI. Median time to DILI was 2 weeks after HAART initiation and no DILI onset was observed after 12 weeks. No severe DILI was seen and the gain in CD4 was similar in patients with or without DILI. Antiretroviral and anti-tuberculosis DILI does occur in our setting, presenting early following HAART initiation. DILI seen is mild, transient and may not require treatment interruption. There is good tolerance to HAART and anti-TB with similar immunological outcomes. Genetic make-up mainly CYP2B6 genotype influences the development of efavirenz based HAART liver injury in Tanzanians

Blue Skies research is essential for ending the Tuberculosis pandemic and advancing a personalized medicine approach for holistic management of Respiratory Tract infections

Objectives: Investments into ‘blue skies’ fundamental TB research in low- and middle-income countries (LMICs) have not been forthcoming. We highlight why blue skies research will be essential for achieving global TB control and eradicating TB. // Methods: We review the historical background to early TB discovery research and give examples of where investments into basic science and fundamental ‘blue skies research’ are delivering novel data and approaches to advance diagnosis, management and holistic care for patients with active and latent TB infection. // Findings: The COVID-19 pandemic has shown that making available adequate funding for priority investments into ‘Blue skies research’ to delineate scientific understanding of a new infectious diseases threat to global health security can lead to rapid development and rollout of new diagnostic platforms, treatments, and vaccines. Several advances in new TB diagnostics, new treatments and vaccine development are underpinned by basic science research. // Conclusions: Basic science research focused can pave the way for a personalized medicine approach for management of TB and other Respiratory Tract Infections and preventing long-term functional disability. Transfer of skills and resources by wealthier nations is required to empower researchers in LMICs countries to engage in and lead basic science ‘blue skies research

Importance of Ethnicity, CYP2B6 and ABCB1 Genotype for Efavirenz Pharmacokinetics and Treatment Outcomes: A Parallel-group Prospective Cohort Study in two sub-Saharan Africa Populations.

We evaluated the importance of ethnicity and pharmacogenetic variations in determining efavirenz pharmacokinetics, auto-induction and immunological outcomes in two African populations. ART naïve HIV patients from Ethiopia (n = 285) and Tanzania (n = 209) were prospectively enrolled in parallel to start efavirenz based HAART. CD4+ cell counts were determined at baseline, 12, 24 and 48 weeks. Plasma and intracellular efavirenz and 8-hydroxyefvairenz concentrations were determined at week 4 and 16. Genotyping for common functional CYP2B6, CYP3A5, ABCB1, UGT2B7 and SLCO1B1 variant alleles were done. Patient country, CYP2B6*6 and ABCB1 c.4036A>G (rs3842A>G) genotype were significant predictors of plasma and intracellular efavirenz concentration. CYP2B6*6 and ABCB1 c.4036A>G (rs3842) genotype were significantly associated with higher plasma efavirenz concentration and their allele frequencies were significantly higher in Tanzanians than Ethiopians. Tanzanians displayed significantly higher efavirenz plasma concentration at week 4 (p<0.0002) and week 16 (p = 0.006) compared to Ethiopians. Efavirenz plasma concentrations remained significantly higher in Tanzanians even after controlling for the effect of CYP2B6*6 and ABCB1 c.4036A>G genotype. Within country analyses indicated a significant decrease in the mean plasma efavirenz concentration by week 16 compared to week 4 in Tanzanians (p = 0.006), whereas no significant differences in plasma concentration over time was observed in Ethiopians (p = 0.84). Intracellular efavirenz concentration and patient country were significant predictors of CD4 gain during HAART. We report substantial differences in efavirenz pharmacokinetics, extent of auto-induction and immunologic recovery between Ethiopian and Tanzanian HIV patients, partly but not solely, due to pharmacogenetic variations. The observed inter-ethnic variations in efavirenz plasma exposure may possibly result in varying clinical treatment outcome or adverse event profiles between populations

Cytochrome 1A1 and 1B1 gene diversity in the Zanzibar islands

Amodiaquine (AQ) is a 4-aminoquinoline widely used in the treatment of malaria as part of the artemisinin combination therapy (ACT). AQ is metabolised towards its main metabolite desethylamodiaquine mainly by cytochrome P450 2C8 (CYP2C8). CYP1A1 and CYP1B1 play a minor role in the metabolism but they seem to be significantly involved in the formation of the short-lived quinine-imine. To complete the genetic variation picture of the main genes involved in AQ metabolism in the Zanzibar population, previously characterised for CYP2C8, we analysed in this study CYP1A1 and CYP1B1 main genetic polymorphisms. The results obtained show a low frequency of the CYP1A1*2B/C allele (2.4%) and a high frequency of CYP1B1*6 (approximately 42%) followed by CYP1B1*2 (approximately 27%) in Zanzibar islands. Genotype data for CYP1A1 and CYP1B1 show a low incidence of fast metabolisers, revealing a relatively safe genetic background in Zanzibars population regarding the appearance of adverse effects.Portuguese Foundation for Science and Technology [SFRH/BPD/34152/2006, IBB/CBME, LA, FEDER/POCI 2010]info:eu-repo/semantics/publishedVersio

Profiles of patients on warfarin anticoagulation therapy in a leading tertiary referral hospital in Kenya; findings and implications for Kenya

Background: Patients’ profiles affect the outcome with warfarin; however, this data, and its implications, is scarce in resource-poor countries without access to pharmacogenetics or regular INR testing. Objectives: To characterize the profiles of patients on long-term warfarin therapy and subsequently use these to guide future anticoagulation management. Methods: Cross-sectional study among 180 adult patients receiving warfarin therapy in at a leading referral hospital in Kenya. Sociodemographic characteristics were obtained through face-to-face interviews. Details of warfarin therapy, concomitant medication and comorbidities were retrieved from medical records. Associations between patients’ profiles and the clinical indications of anticoagulation were computed at p ≤ 0.05. Results: Warfarin maintenance dose was 6.17 (±2.75) mg per day. Venous thromboembolism (56.6%) amongst obese patients (p = 0.0019) and cardioembolic events (48.3%) among males (p = 0.0316) aged ≤50 years (p = 0.0436) whose body mass indices were ≤ 25 (p < 0.0001) were the most common indications. Two-fifths and 45.0% of the patients had at least one other disease and concomitant medications. Conclusions: Long term warfarin therapy among Kenyans is mainly for overweight or lean middle-aged individuals suffering from venous or cardioembolic diseases. Studies should correlate patients’ profiles with warfarin response to guide future management