PharmGKB summary: Efavirenz pathway, pharmacokinetics

Factors Associated With Long-term Retention in Antiretroviral Therapy Among People Living With HIV: Evidence From a Tertiary Hospital in Jakarta, Indonesia

OBJECTIVES

This study investigated factors associated with the retention of people living with human immunodeficiency virus (HIV) on antiretroviral therapy (ART) during the first 3 years of treatment.

METHODS

A retrospective study using electronic health records was conducted at a tertiary hospital in Jakarta, Indonesia. Adult HIV-positive patients who started ART from 2010 until 2020 were included. A binary logistic regression model was used to identify factors associated with ART retention in the first 3 years.

RESULTS

In total, 535 respondents were included in the analysis. The ART retention rates for the first, second, and third years were 83.7%, 79.1%, and 77.2%, respectively. The multivariate analysis revealed a negative association between CD4 count when starting ART and retention. Patients with CD4 counts >200 cells/mL were 0.65 times less likely to have good retention than those with CD4 counts ≤200 cells/mL. The year of starting ART was also significantly associated with retention. Patients who started ART in 2010-2013 or 2014-2016 were less likely to have good retention than those who started ART in 2017-2020, with adjusted odds ratios of 0.52 and 0.40, respectively. Patients who received efavirenz-based therapy were 1.69 times more likely to have good retention than those who received nevirapine (95% confidence interval, 1.05 to 2.72).

CONCLUSIONS

Our study revealed a decline in ART retention in the third year. The CD4 count, year of enrollment, and an efavirenz-based regimen were significantly associated with retention. Patient engagement has long been a priority in HIV programs, with interventions being implemented to address this issue.

Proposal of pharmacophore model for HIV reverse transcriptase inhibitors: Combined mutational effect analysis, molecular dynamics, molecular docking and pharmacophore modeling study

OBJECTIVES

Antiretroviral therapy (ART) efficacy is jeopardized by the emergence of drug resistance mutations in HIV, compromising treatment effectiveness. This study aims to propose novel analogs of Effavirenz (EFV) as potential direct inhibitors of HIV reverse transcriptase, employing computer-aided drug design methodologies.

METHODS

Three key approaches were applied: a mutational profile study, molecular dynamics simulations, and pharmacophore development. The impact of mutations on the stability, flexibility, function, and affinity of target proteins, especially those associated with NRTI, was assessed. Molecular dynamics analysis identified G190E as a mutation significantly altering protein properties, potentially leading to therapeutic failure. Comparative analysis revealed that among six first-line antiretroviral drugs, EFV exhibited notably low affinity with viral reverse transcriptase, further reduced by the G190E mutation. Subsequently, a search for EFV-similar inhibitors yielded 12 promising molecules based on their affinity, forming the basis for generating a pharmacophore model.

RESULTS

Mutational analysis pinpointed G190E as a crucial mutation impacting protein properties, potentially undermining therapeutic efficacy. EFV demonstrated diminished affinity with viral reverse transcriptase, exacerbated by the G190E mutation. The search for EFV analogs identified 12 high-affinity molecules, culminating in a pharmacophore model elucidating key structural features crucial for potent inhibition.

CONCLUSION

This study underscores the significance of EFV analogs as potential inhibitors of HIV reverse transcriptase. The findings highlight the impact of mutations on drug efficacy, particularly the detrimental effect of G190E. The generated pharmacophore model serves as a pivotal reference for future drug development efforts targeting HIV, providing essential structural insights for the design of potent inhibitors based on EFV analogs identified in vitro.

Effects of rifampicin, CYP2B6 and ABCB1 polymorphisms on efavirenz plasma concentration in Chinese patients living with HIV and tuberculosis

BACKGROUND

Tuberculosis (TB) is the leading opportunistic infection of people living with human immunodeficiency virus (HIV; PLWH). Cytochrome P450 (CYP) 2B6 and ATP-binding cassette sub-family B member 1 (ABCB1) are involved in the metabolism and transportation of efavirenz. The study was aimed to investigate the effects of rifampicin, CYP2B6 and ABCB1 polymorphisms on efavirenz exposure in Chinese PLWH co-infected with TB.

METHOD

PLWH were screened according to inclusion and exclusion criteria and divided into HIV group and HIV/TB group. Efavirenz plasma concentration (C₀) was determined, dose-adjusted concentration (C₀/D) was calculated, and genotypes of CYP2B6 516G>T, 785A>G, and ABCB1 2677G>T, 3435C>T were analyzed.

RESULTS

252 PLWH were enrolled, including 75 co-infected with TB and concomitant with rifampicin. Efavirenz C₀ and C₀/D were both higher in HIV group (1.94 μg/mL, 0.2007 (μg/ml)/(mg/kg/d)) compared with HIV/TB group (1.52 μg/mL, 0.1557 (μg/ml)/(mg/kg/d)) (p = .001). Efavirenz C₀/D was significantly higher in patients with variant genotypes of CYP2B6 516G>T and 785A>G (p<.001), and was significantly lower in HIV/TB group compared with HIV group among patients with CYP2B6 516 GG, TT, and 785 AA, AG genotypes (p < .05).

CONCLUSION

Efavirenz exposure is reduced by co-administration with rifampicin, and related to genetic polymorphisms of CYP2B6.

Efavirenz: History, Development and Future

Efavirenz (Sustiva^®) is a first-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) used to treat human immunodeficiency virus (HIV) type 1 infection or to prevent the spread of HIV. In 1998, the FDA authorized efavirenz for the treatment of HIV-1 infection. Patients formerly required three 200 mg efavirenz capsules daily, which was rapidly updated to a 600 mg tablet that only required one tablet per day. However, when given 600 mg once daily, plasma efavirenz concentrations were linked not only to poor HIV suppression but also to toxicity. Clinical data suggested that the standard dose of efavirenz could be reduced without compromising its effectiveness, resulting in a reduction in side effects and making the drug more affordable. Therefore, ENCORE1 was performed to compare the efficiency and safeness of a reduced dose of efavirenz (400 mg) with the standard dose (600 mg) plus two NRTI in antiretroviral-naïve HIV-infected individuals. Nowadays, due to the emergence of integrase strand transfer inhibitors (INSTIs), some consider that it is time to stop using efavirenz as a first-line treatment on a global scale, in the parts of the world where that is possible. Efavirenz has been a primary first-line antiviral drug for more than 15 years. However, at this moment, the best use for efavirenz could be for pre-exposure prophylaxis (PrEP) and repurposing in medicine.

Frequency of CYP2B6 Alleles in Major Iranian Ethnicities, Affecting Response to Efavirenz

Introduction

Efavirenz is an antihuman immunodeficiency virus (HIV) drug metabolized by cytochrome P450 2B6 (CYP2B6) enzyme. Cytochrome P450 2B6 is an enzyme that in humans is encoded by the CYP2B6 gene. Polymorphisms of this gene play a crucial role in the metabolism of drugs such as Efavirenz. This study aims to evaluate the frequency of three clinically significant CYP2B6 polymorphisms (CYP2B6^∗6 (516G > T), CYP2B6^∗4 (785A > G), and CYP2B6^∗5 (1459C > T)) in three major Iranian ethnicities.

Methods

One hundred forty-seven participants from three main Iranian ethnicities were included in this study. After DNA extraction, CYP2B6^∗6 (516G > T), CYP2B6^∗4 (785A > G), and CYP2B6^∗5 (1459C > T) were genotyped using tetra-primer amplification refractory mutation system polymerase chain reaction (ARMS-PCR).

Results

The frequency of the mutated allele in the Iranian population for CYP2B6^∗6 (516G > T) was 41.50 (95% CI: 35.81, 47.36), which was significantly lower than in Kurds (59.62, 95% CI: 45.10, 72.99). Similarly, Kurds had a higher frequency of mutated allele of CYP2B6^∗5 (1459C > T) (46.15%, 95% CI: 32.23, 60.53) than in Iranians (24.49%, 95% CI: 19.68, 29.82). The frequency of A and G alleles of CYP2B6^∗4 (785A > G) was 62.59% (95% CI: 56.78, 68.13) and 37.41 (95% CI: 31.87, 43.22), respectively.

Conclusion

Kurds are at higher risk of adverse drug reactions (ADRs) and insufficient anti-HIV response compared to other Iranians.

CYP3A and CYP2B6 Genotype Predicts Glucose Metabolism Disorder among HIV Patients on Long-Term Efavirenz-Based ART: A Case-Control Study

Long-term antiretroviral treatment (cART) increases the risk of glucose metabolism disorders (GMDs). Genetic variation in drug-metabolizing enzymes and transporters may influence susceptibility to cART-associated GMDs. We conducted a case-control study to investigate the association of pharmacogenetic variations with cART-induced GMDs. A total of 240 HIV patients on long-term efavirenz-based cART (75 GMD cases and 165 controls without GMDs) were genotyped for CYP3A4*1B, CYP3A5 (*3,*6), CYP2B6*6, UGT2B7*2, ABCB1 (c.3435C>T, c.4036A>G), and SLCO1B1 (*1b, *5). GMD cases were defined as the presence of impaired fasting glucose, insulin resistance, or diabetes mellitus (DM). Case-control genotype/haplotype association and logistic regression analysis were performed by adjusting for age, sex, and BMI. The major CYP3A haplotype were CYP3A5*3 (53.8%), CYP3A4*1B (17.3%), combinations of CYP3A4*1B, and CYP3A5*6 (10.9%), and CYP3A wild type (7%). CYP3A5*6 allele (p = 0.005) and CYP3A5*6 genotype (p = 0.01) were significantly associated with GMD cases. Multivariate analysis indicated CYP3A haplotype as a significant predictor of GMD (p = 0.02) and IFG (p = 0.004). CYP2B6*6 significantly predicted DM (p = 0.03). CYP3A haplotype and CYP2B6*6 genotype are independent significant predictors of GMD and DM, respectively, among HIV patients on long-term EFV-based cART.

Pharmacogenetic predictors of variability in efavirenz pharmacokinetics in an admixed Brazilian HIV cohort

AIMS

To investigate the influence of pharmacogenetic polymorphisms on efavirenz (EFV) exposure and metabolism in HIV-infected Brazilians under treatment with EFV-containing antiretroviral (ART) regimens.

METHODS

HIV-positive adults (n=82) on stable ART regimens containing 600 mg EFV once daily for at least 6 months were recruited at two university hospitals. Blood samples collected at mid-dose interval were used to quantify the plasma concentrations of EFV (denoted [EFV]), its major metabolite 8-OH-EFV ([8-OH-EFV]) and [8-OH-EFV]/[EFV] metabolic ratio, and to genotype single nucleotide polymorphisms (SNPs) in CYP2B6 (rs3745274, c.516G>T; rs28399499, c.983T>C) and ABCB1 (rs3842, c.4036G>A). CYP2B6 metabolic phenotypes were inferred from the CYP2B6 diplotypes. Linear regression modeling was applied to identify sociodemographic, clinical and pharmacogenetic predictors of [EFV] and [8-OH-EFV]/[EFV] metabolic ratio.

RESULTS

Wide (50-fold) interindividual variation in [EFV], [8-OH-EFV] and [8-OH-EFV]/[EFV] was observed; 69.5% of participants had [EFV] within the nominal therapeutic range (1000-4000 ng/ml), while 19.5%, and 11.0% had [EFV] below and above this range, respectively. Multiple regression modeling retained only CYP2B6 metabolic phenotypes or the combined rs3745274 and rs28399499 genotypes, as significant predictors of [EFV] and [8-OH-EFV]/[EFV].

CONCLUSION

EFV exposure and disposition varied widely among HIV-infected Brazilians under stable treatment with EFV-containing ART regimens. About one-tenth of the participants had [EFV] exceeding nominal supratherapeutic concentration (4000 ng/mL), but reported tolerance to the ARV regimens, while one fifth of participants had nominal subtherapeutic [EFV] (<1000 ng/ml) but adequate virological response. Genotype for the two CYP2B6 SNPs studied explained 48% of variation in [EFV] and 35% of variation in [8-OH-EFV]/[EFV].

Brief Report: Nicotine Metabolism Ratio Increases in HIV-Positive Smokers on Effective Antiretroviral Therapy: A Cohort Study

BACKGROUND

People with HIV (PWH) smoke tobacco at much higher rates than the general population. Previous research has shown that PWH have faster nicotine metabolism than HIV-uninfected individuals, which may underlie this disparity, but the cause is unknown. We investigated whether higher nicotine metabolite ratio (NMR; 3-hydroxycotinine:cotinine), a validated biomarker of nicotine metabolism through CYP2A6, was associated with antiretroviral use among HIV-infected smokers.

METHODS

We conducted a retrospective cohort study of HIV-positive smokers in the University of Pennsylvania Center for AIDS Research cohort. We compared the NMR before viral suppression (>10,000 copies/mL) and after viral suppression on antiretroviral therapy (<200 copies/mL). We used mixed-effects linear regression to analyze the change in NMR after viral suppression and assessed for effect modification by efavirenz use.

RESULTS

Eighty-nine individuals were included in the study. We observed effect modification by efavirenz use (interaction term for efavirenz use, P < 0.001). Among those on nonefavirenz regimens, the mean NMR increased by 0.14 (95% confidence interval: 0.05 to 0.23, P = 0.002). Among those on efavirenz-containing regimens, the mean NMR increased by 0.53 (95% confidence interval: 0.39-0.66, P < 0.001).

CONCLUSIONS

We observed a clinically and statistically significant increase in NMR after viral suppression among smokers with HIV, which more than doubled among those on efavirenz-based regimens. Higher NMR among HIV-positive smokers on antiretroviral therapy may help explain the higher rates of tobacco use and lower quit rates among PWH in care. These findings suggest that regimen choice and other modifiable factors may be targets for future attempts to increase success rates for tobacco cessation among PWH.

Pharmacogenetics and Precision Medicine Approaches for the Improvement of COVID-19 Therapies

Many drugs are being administered to tackle coronavirus disease 2019 (COVID-19) pandemic situations without establishing clinical effectiveness or tailoring safety. A repurposing strategy might be more effective and successful if pharmacogenetic interventions are being considered in future clinical studies/trials. Although it is very unlikely that there are almost no pharmacogenetic data for COVID-19 drugs, however, from inferring the pharmacokinetic (PK)/pharmacodynamic(PD) properties and some pharmacogenetic evidence in other diseases/clinical conditions, it is highly likely that pharmacogenetic associations are also feasible in at least some COVID-19 drugs. We strongly mandate to undertake a pharmacogenetic assessment for at least these drug–gene pairs (atazanavir–UGT1A1, ABCB1, SLCO1B1, APOA5; efavirenz–CYP2B6; nevirapine–HLA, CYP2B6, ABCB1; lopinavir–SLCO1B3, ABCC2; ribavirin–SLC28A2; tocilizumab–FCGR3A; ivermectin–ABCB1; oseltamivir–CES1, ABCB1; clopidogrel–CYP2C19, ABCB1, warfarin–CYP2C9, VKORC1; non-steroidal anti-inflammatory drugs (NSAIDs)–CYP2C9) in COVID-19 patients for advancing precision medicine. Molecular docking and computational studies are promising to achieve new therapeutics against SARS-CoV-2 infection. The current situation in the discovery of anti-SARS-CoV-2 agents at four important targets from in silico studies has been described and summarized in this review. Although natural occurring compounds from different herbs against SARS-CoV-2 infection are favorable, however, accurate experimental investigation of these compounds is warranted to provide insightful information. Moreover, clinical considerations of drug–drug interactions (DDIs) and drug–herb interactions (DHIs) of the existing repurposed drugs along with pharmacogenetic (e.g., efavirenz and CYP2B6) and herbogenetic (e.g., andrographolide and CYP2C9) interventions, collectively called multifactorial drug–gene interactions (DGIs), may further accelerate the development of precision COVID-19 therapies in the real-world clinical settings.

Predictors of Efavirenz Plasma Exposure, Auto-Induction Profile, and Effect of Pharmacogenetic Variations among HIV-Infected Children in Ethiopia: A Prospective Cohort Study

(1) Background: Efavirenz plasma concentration displays wide between-patient variability partly due to pharmacogenetic variation and autoinduction. Pediatric data on efavirenz pharmacokinetics and the relevance of pharmacogenetic variation are scarce, particularly from sub-Saharan Africa, where >90% of HIV-infected children live and population genetic diversity is extensive. We prospectively investigated the short- and long-term effects of efavirenz auto-induction on plasma drug exposure and the influence of pharmacogenetics among HIV-infected Ethiopian children. (2) Method: Treatment-naïve HIV-infected children aged 3-16 years old (n = 111) were enrolled prospectively to initiate efavirenz-based combination antiretroviral therapy (cART). Plasma efavirenz concentrations were quantified at 4, 8, 12, 24, and 48 weeks of cART. Genotyping for CYP2B6, CYP3A5, UGT2B7, ABCB1, and SLCO1B1 common functional variant alleles was performed. (3) Results: The efavirenz plasma concentration reached a peak at two months, declined by the 3rd month, and stabilized thereafter, with no significant difference in geometric mean over time. On average, one-fourth of the children had plasma efavirenz concentrations ≥4 µg/mL. On multivariate analysis, CYP2B6*6 and ABCB1c.3435 C > T genotypes and low pre-treatment low-density lipoprotein (LDL) were significantly associated with higher plasma efavirenz concentration regardless of treatment duration. Duration of cART, sex, age, nutritional status, weight, and SLCO1B, CYP3A5, UGT2B7, and ABCB1 rs3842 genotypes were not significant predictors of efavirenz plasma exposure. (4) Conclusion: Pre-treatment LDL cholesterol and CYP2B6*6 and ABCB1c.3435 C > T genotypes predict efavirenz plasma exposure among HIV-infected children, but treatment-duration-dependent changes in plasma efavirenz exposure due to auto-induction are not statistically significant.

Large variability in plasma efavirenz concentration in Papua New Guinea HIV/AIDS patients associated with high frequency of CYP2B6 516T allele

Papua New Guinea (PNG) has a high HIV/AIDS prevalence and very high frequency of the CYP2B6 c.516G>T (rs3745274) variant. We have conducted the first investigation of the impact of c.516G>T and patient demographics on plasma efavirenz (EFV) and 8‐hydroxyefavirenz (8OH‐EFV) concentrations, metabolic ratio (8OH‐EFV/EFV) (MR), and their association with adverse effects, in PNG patients with HIV/AIDS. For 156 PNG patients with HIV/AIDS taking EFV 600 mg/day (for 3–156 months), plasma EFV and 8OH‐EFV concentrations were quantified, CYP2B6 c.516G>T genotyped, and demographic and self‐reported adverse effects data recorded. Genotype differences in EFV and 8OH‐EFV concentrations, MR, and percent within therapeutic range (1000–4000 ng/ml) were examined, in addition to EFV and 8OH‐EFV concentration differences between patients experiencing adverse effects. CYP2B6 c.516T allele frequency was 53%. Plasma EFV (p < 0.0001), 8OH‐EFV (p < 0.01), and MR (p < 0.0001) differed significantly between genotypes, with genotype explaining 38%, 10%, and 50% of variability, respectively. Plasma EFV concentrations were significantly higher in T/T (median = 5168 ng/ml) than G/G (1036 ng/ml, post hoc p < 0.0001) and G/T (1502 ng/ml, p < 0.0001) genotypes, with all patients above therapeutic range (n = 23) being T/T genotype (p < 0.0001). EFV and 8OH‐EFV concentrations were not significantly higher in patients experiencing adverse effects. In PNG HIV/AIDS population where the 516T frequency is very high, it explains a substantial portion of variability (38%) in EFV disposition; however, at least for the patients receiving EFV long term, this does not translate into significant side effects.

Instability of Efavirenz Metabolites Identified During Method Development and Validation

Accurate quantification of efavirenz metabolites in patient samples is required to investigate their potential contribution to efavirenz adverse events. This study aimed to validate a LC-MS/MS method to quantify and investigate the stability of efavirenz and metabolites in human plasma. Compounds were extracted from plasma by supported liquid extraction and resolved on a C18 column. Validation was performed following FDA bioanalytical method validation guidelines. Stability under common conditions of sample pre-treatment and storage were assessed. Efavirenz and 8-hydroxyefavirenz were stable for all conditions tested. 7-Hydroxyefavirenz and 8,14-dihydroxyefavirenz were not stable in plasma at room temperature for 24 h (46%-69% loss), -20°C for 90 days (17%-50% loss), or 60°C for 1 h (90%-95% loss). Efavirenz and 8-hydroxyefavirenz concentrations in HIV/AIDS patient (n=5) plasma prepared from pre-treated (60°C for 1 h) whole blood varied from 517-8564 ng/mL and 131-813 ng/mL, respectively. 7-Hydroxyefavirenz and 8,14-dihydroxyefavirenz concentrations were below validated lower limits of quantification (0.25 and 0.5 ng/mL, respectively), most likely due to sample pre-treatment. This is the first report of 7-hydroxyefavirenz and 8,14-dihydroxyefavirenz instability under conditions commonly used in preparation of samples from HIV/AIDS patients. Alternative biosafety measures to heat pre-treatment must therefore be used for accurate quantification of plasma 7-hydroxyefavirenz and 8,14-dihydroxyefavirenz.

Particle Forming Amorphous Solid Dispersions: A Mechanistic Randomized Pharmacokinetic Study in Humans

Amorphous solid dispersions (ASDs) are a promising drug-delivery strategy to overcome poor solubility through formulation. Currently, the understanding of drug absorption mechanisms from ASDs in humans is incomplete. Aiming to gain insights in this matter, we conducted a randomized cross-over design open-label clinical study (NCT03886766) with 16 healthy male volunteers in an ambulatory setting, using micro-dosed efavirenz as a model drug. In three phases, subjects were administered (1) solid ASD of efavirenz 50 mg or (2) dissolved ASD of efavirenz 50 mg or (3) a molecular solution of efavirenz 3 mg (non-ASD) as a control in block-randomized order. Endpoints were the pharmacokinetic profiles (efavirenz plasma concentration vs. time curves) and derived pharmacokinetic parameters thereof (AUC_0–t, C_max, t_max, and k_a). Results showed that the dissolved ASD (intervention 2) exhibited properties of a supersaturated solution (compared to aqueous solubility) with rapid and complete absorption of the drug from the drug-rich particles. All interventions showed similar AUC_0–t and were well tolerated by subjects. The findings highlight the potential of particle forming ASDs as an advanced drug-delivery system for poorly soluble drugs and provide essential insights into underlying mechanisms of ASD functioning in humans, partially validating current conceptual models.

Pharmacogenomics and COVID-19: clinical implications of human genome interactions with repurposed drugs

The outbreak of Coronavirus disease 2019 (COVID-19) has evolved into an emergent global pandemic. Many drugs without established efficacy are being used to treat COVID-19 patients either as an offlabel/compassionate use or as a clinical trial. Although drug repurposing is an attractive approach with reduced time and cost, there is a need to make predictions on success before the start of therapy. For the optimum use of these repurposed drugs, many factors should be considered such as drug–gene or dug–drug interactions, drug toxicity, and patient co-morbidity. There is limited data on the pharmacogenomics of these agents and this may constitute an obstacle for successful COVID-19 therapy. This article reviewed the available human genome interactions with some promising repurposed drugs for COVID-19 management. These drugs include chloroquine (CQ), hydroxychloroquine (HCQ), azithromycin, lopinavir/ritonavir (LPV/r), atazanavir (ATV), favipiravir (FVP), nevirapine (NVP), efavirenz (EFV), oseltamivir, remdesivir, anakinra, tocilizumab (TCZ), eculizumab, heme oxygenase 1 (HO-1) regulators, renin–angiotensin–aldosterone system (RAAS) inhibitors, ivermectin, and nitazoxanide. Drug-gene variant pairs that may alter the therapeutic outcomes in COVID-19 patients are presented. The major drug variant pairs that associated with variations in clinical efficacy include CQ/HCQ (CYP2C8, CYP2D6, ACE2, and HO-1); azithromycin (ABCB1); LPV/r (SLCO1B1, ABCB1, ABCC2 and CYP3A); NVP (ABCC10); oseltamivir (CES1 and ABCB1); remdesivir (CYP2C8, CYP2D6, CYP3A4, and OATP1B1); anakinra (IL-1a); and TCZ (IL6R and FCGR3A). The major drug variant pairs that associated with variations in adverse effects include CQ/HCQ (G6PD; hemolysis and ABCA4; retinopathy), ATV (MDR1 and UGT1A1*28; hyperbilirubinemia; and APOA5; dyslipidemia), NVP (HLA-DRB1*01, HLA-B*3505 and CYP2B6; skin rash and MDR1; hepatotoxicity), and EFV (CYP2B6; depression and suicidal tendencies).

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

Bidirectional Associations among Nicotine and Tobacco Smoke, NeuroHIV, and Antiretroviral Therapy

People living with HIV (PLWH) in the antiretroviral therapy (ART) era may lose more life-years to tobacco use than to HIV. Yet, smoking rates are more than twice as high among PLWH than the general population, contributing not just to mortality but to other adverse health outcomes, including neurocognitive deficits (neuroHIV). There is growing evidence that synergy with chronic inflammation and immune dysregulation that persists despite ART may be one mechanism by which tobacco smoking contributes to neuroHIV. This review will summarize the differential effects of nicotine vs tobacco smoking on inflammation in addition to the effects of tobacco smoke components on HIV disease progression. We will also discuss biomarkers of inflammation via neuroimaging as well as biomarkers of nicotine dependence (e.g., nicotine metabolite ratio). Tobacco smoking and nicotine may impact ART drug metabolism and conversely, certain ARTs may impact nicotine metabolism. Thus, we will review these bidirectional relationships and how they may contribute to neuroHIV and other adverse outcomes. We will also discuss the effects of tobacco use on the interaction between peripheral organs (lungs, heart, kidney) and subsequent CNS function in the context of HIV. Lastly, given the dramatic rise in the use of electronic nicotine delivery systems, we will discuss the implications of vaping on these processes. Despite the growing recognition of the importance of addressing tobacco use among PLWH, more research is necessary at both the preclinical and clinical level to disentangle the potentially synergistic effects of tobacco use, nicotine, HIV, cognition and immune dysregulation, as well as identify optimal approaches to reduce tobacco use. Graphical Abstract Proposed model of the relationships among HIV, ART, smoking, inflammation, and neurocognition. Solid lines represent relationships supported by evidence. Dashed lines represent relationships for which there is not enough evidence to make a conclusion. (a) HIV infection produces elevated levels of inflammation even among virally suppressed individuals. (b) HIV is associated with deficits in cognition function. (c) Smoking rates are higher among PLWH, compared to the general population. (d) The nicotine metabolite ratio (NMR) is associated with smoking behavior. (e) HIV and tobacco use are both associated with higher rates of psychiatric comorbidities, such as depression, and elevated levels of chronic stress. These factors may represent other mechanisms linking HIV and tobacco use. (f) The relationship between nicotine, tobacco smoking, and inflammation is complex, but it is well-established that smoking induces inflammation; the evidence for nicotine as anti-inflammatory is supported in some studies, but not others. (g) The relationship between tobacco use and neurocognition may differ for the effects of nicotine (acute nicotine use may have beneficial effects) vs. tobacco smoking (chronic use may impair cognition). (h) Elevated levels of inflammation may be associated with deficits in cognition. (i) PLWH may metabolize nicotine faster than those without HIV; the mechanism is not yet known and the finding needs validation in larger samples. We also hypothesize that if HIV-infection increases nicotine metabolism, then we should observe an attenuation effect once ART is initiated. (j) It is possible that the increase in NMR is due to ART effects on CYP2A6. (k) We hypothesize that faster nicotine metabolism may result in higher levels of inflammation since nicotine has anti-inflammatory properties.

Pharmacokinetics and phenotyping properties of the Basel phenotyping cocktail combination capsule in healthy male adults

AIMS

We compared the phenotyping metrics of a combination capsule formulation to its individual components of the newly composed Basel phenotyping cocktail. Moreover, we investigated a reduced sampling regimen for clinical applications.

METHODS

We performed in vitro experiments and a crossover pharmacokinetic study in twelve healthy male subjects to compare the Basel phenotyping cocktail capsule containing 6 cytochrome P450 (CYP) probe drugs with individual administration of the same drugs. Parent compounds and selected metabolites were determined by liquid chromatography-tandem mass spectrometry. Metabolic ratios (MR) for are under the curve (AUC) and single time point measurements and their correlation were determined.

RESULTS

Experiments with human liver microsomes and primary human hepatocytes in 3D co-culture confirmed that flurbiprofen is a suitable CYP2C9 substrate. Both cocktail formulations (capsule and individual probe drug administration) were well-tolerated and yielded reproducible MRs, which were almost identical. Correlations between single time point ratios and the corresponding AUC ratios depended on the sampling time point and the concentration time curve of the probe drugs. The MR of the capsule (Spearman rank correlation coefficient, R_s : 0.77-0.97) as well as the individual components (R_s : 0.69-0.99) correlated best at 6 h post-treatment considering all 6 CYPs. Moreover, the 2-h time points of the capsule agreed suitably with the AUC; however, the MR of omeprazole could not be determined for 10 out of 12 subjects.

CONCLUSION

The capsule is easy to swallow, well tolerated and provides reliable estimates for CYP activity. The optimal sampling point for the capsule formulation is 6 h after intake.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2B6 and Efavirenz-Containing Antiretroviral Therapy

The HIV type-1 nonnucleoside reverse transcriptase inhibitor, efavirenz, is widely used to treat HIV type-1 infection. Efavirenz is predominantly metabolized into inactive metabolites by cytochrome P450 (CYP)2B6, and patients with certain CYP2B6 genetic variants may be at increased risk for adverse effects, particularly central nervous system toxicity and treatment discontinuation. We summarize the evidence from the literature and provide therapeutic recommendations for efavirenz prescribing based on CYP2B6 genotypes.

Differences in the rate of nicotine metabolism among smokers with and without HIV

OBJECTIVE

HIV-infected smokers lose more life years to tobacco use than to HIV infection. The nicotine metabolite ratio (NMR), a biomarker of CYP2A6, represents individual variation in the rate at which nicotine is metabolized and is associated with response to smoking cessation treatments. We evaluated whether HIV-infected smokers metabolize nicotine faster than HIV-uninfected smokers, which may contribute to the disproportionate smoking burden and may have important treatment implications.

DESIGN

We analysed baseline data from two clinical trials (NCT01710137; NCT01314001) to compare the NMR in HIV-infected smokers (N = 131) to HIV-uninfected smokers (N = 199).

METHODS

Propensity scores were used to match the groups 2 : 1 on characteristics that influence NMR: sex, race, BMI and smoking rate. Nicotine metabolites were assessed via liquid chromatography-tandem mass spectrometry methods and the ratio of 3-hydroxycotinine:cotinine was used to compute the NMR.

RESULTS

HIV-infected smokers had significantly higher NMR (mean = 0.47, SEM = 0.02) and were more likely to be in the highest NMR quartile compared with HIV-uninfected smokers (mean = 0.34, SEM = 0.02; Ps < 0.001).

CONCLUSION

The higher NMR observed among HIV-infected smokers may partially explain higher smoking rates and lower response to transdermal nicotine therapy. Understanding the mechanisms by which HIV and/or ART contribute to faster nicotine metabolism may guide the use of the NMR to personalize tobacco cessation strategies in this underserved population.

Pharmacogenomics in Papua New Guineans: unique profiles and implications for enhancing drug efficacy while improving drug safety

Papua New Guinea (PNG) can be roughly divided into highland, coastal and island peoples with significant mitochondrial DNA differentiation reflecting early and recent distinct migrations from Africa and East Asia, respectively. Infectious diseases such as tuberculosis, malaria and HIV severely impact on the health of its peoples for which drug therapy is the major treatment and pharmacogenetics has clinical relevance for many of these drugs. Although there is generally little information about known single nucleotide polymorphisms in the population, in some instances, their frequencies have been shown to be higher than anywhere worldwide. For example, CYP2B6*6 is over 50%, and CYP2C19*2 and *3 are over 40 and 25%, respectively. Conversely, CYP2A6*9, 2B6*2, *3, *4 and *18, and 2C8*3 appear to be much lower than in Whites. CYP2D6 known variants are unclear, and for phase II enzymes, only UGT2B7 and UGT1A9 data are available, with variant frequencies either slightly lower than or similar to Whites. Although almost all PNG people tested are rapid acetylators, but which variant(s) define this phenotype is not known. For HLA-B*13:01, HLA-B*35:05 and HLA-C*04:01, the frequencies show some regioselectivity, but the clinical implications with respect to adverse drug reactions are not known. There are minimal phenotype data for the CYPs and nothing is known about drug transporter or receptor genetics. Determination of genetic variants that are rare in Whites or Asians but common in PNG people is a topic of both scientific and clinical importance, and further research needs to be carried out. Optimizing the safety and efficacy of infectious disease drug therapy through pharmacogenetic studies that have translation potential is a priority.

Brief Report: Rate of Nicotine Metabolism and Tobacco Use Among Persons With HIV: Implications for Treatment and Research

BACKGROUND

The nicotine metabolite ratio (NMR) is a biomarker that represents individual variation in the speed that nicotine is metabolized. The rate of nicotine metabolism alters smoking behavior (eg, amount) and has been validated for personalizing tobacco dependence medication selection to increase treatment efficacy and reduce treatment side effects in the general population of smokers. Although smoking rates are extremely high among those with HIV, the NMR has not been evaluated in this underserved population.

METHODS

We used baseline data from a smoking cessation clinical trial for smokers with HIV (N = 131) to examine associations between NMR and demographic, smoking, disease-related, and psychological characteristics. Pearson r and analysis of variance were used to identify univariate correlates of NMR, which were then entered into a multiple linear regression model.

RESULTS

In univariate analyses, a higher NMR (faster nicotine metabolism) was associated with being white, and more cigarettes per day, nicotine dependence, exhaled carbon monoxide, and symptoms of depression and anxiety, and using efavirenz. In a multiple regression model, a higher NMR was associated with more cigarettes per day, higher anxiety symptoms, and efavirenz use.

CONCLUSIONS

As in other populations, faster nicotine metabolism was associated with the use of more cigarettes and higher anxiety symptoms. Notably, efavirenz use was associated with faster metabolism, which might make it harder to quit smoking for people with HIV treated with that medication. These findings could help guide further study and the clinical use of the NMR to personalize nicotine dependence treatment in this underserved population.

Tryptophan metabolism and its relationship with central nervous system toxicity in people living with HIV switching from efavirenz to dolutegravir

The mechanisms underlying central nervous system (CNS) toxicities in antiretroviral-treated persons living with HIV (PLWH) remain elusive. We investigated the associations between markers of tryptophan metabolism and measurements of CNS toxicity in PLWH. In a prospective study, virologically suppressed PLWH receiving efavirenz-containing antiretroviral regimens with ongoing CNS toxicity were switched to dolutegravir-containing regimens and followed up for 12 weeks. Plasma tryptophan and kynurenine concentrations and the kynurenine/tryptophan ratio were calculated. Ten CNS toxicities were graded according to the ACTG adverse events scale. Scores ranged from 0 (none) to 3 (severe) and were summed, giving a total from 0 to 30. Paired-samples t tests and linear mixed model analyses were conducted to assess changes in, and relationships between, laboratory and clinical parameters. Mean kynurenine plasma concentration increased from baseline to week 12 (2.15 to 2.50 μmol/L, p = 0.041). No significant changes were observed for tryptophan (54.74 to 56.42 μmol/L, p = 1.000) or kynurenine/tryptophan ratio (40.37 to 41.08 μmol/L, p = 0.276). Mean CNS toxicity score decreased from 10.00 to 4.63 (p < 0.001). Plasma kynurenine concentration correlated with CNS toxicity score: for every 1 μmol/L increase in kynurenine concentration observed, a 1.7 point decrease was observed in CNS toxicity score (p < 0.038). A similar trend was observed for the kynurenine/tryptophan ratio: for every 1 μmol/mmol increase observed in kynurenine/tryptophan ratio, a 0.1 point decrease was observed in CNS toxicity score (p = 0.054). Switching from efavirenz to dolutegravir was associated with increases in plasma kynurenine concentration and improvements in CNS toxicity scores. Underlying mechanisms explaining the rise in kynurenine concentrations need to be established.

Long-term efavirenz pharmacokinetics is comparable between Tanzanian HIV and HIV/Tuberculosis patients with the same CYP2B6*6 genotype

The impact of anti-tuberculosis co-treatment on efavirenz (EFV) exposure is still uncertain as contradictory reports exist, and the relevance of CYP2B6*6 genetic polymorphism on efavirenz clearance while on-and-off anti-tuberculosis co-treatment is not well investigated. We investigated the determinants of long-term efavirenz pharmacokinetics by enrolling HIV (n = 20) and HIV/Tuberculosis (n = 36) subjects undergoing efavirenz and efavirenz/rifampicin co-treatment respectively. Pharmacokinetic samplings were done 16 weeks after initiation of efavirenz-based anti-retroviral therapy and eight weeks after completion of rifampicin-based anti-tuberculosis treatment. Population pharmacokinetic modeling was used to characterize variabilities and covariates of efavirenz pharmacokinetic parameters. CYP2B6*6 genetic polymorphism but not rifampicin co-treatment was the statistically significant covariate. The estimated typical efavirenz clearance in the HIV only subjects with the CYP2B6*1/*1 genotype was 23.6 L/h/70 kg, while it was 38% and 69% lower in subjects with the CYP2B6*1/*6 and *6/*6 genotypes, respectively. Among subjects with the same CYP2B6 genotypes, efavirenz clearances were comparable between HIV and HIV/Tuberculosis subjects. Typical efavirenz clearances before and after completion of anti-tuberculosis therapy were comparable. In conclusion, after 16 weeks of treatment, efavirenz clearance is comparable between HIV and HIV/Tuberculosis patients with the same CYP2B6 genotype. CYP2B6 genotyping but not anti-tuberculosis co-treatment should guide efavirenz dosing to optimize treatment outcomes.

Long-Term Effect of Rifampicin-Based Anti-TB Regimen Coadministration on the Pharmacokinetic Parameters of Efavirenz and 8-Hydroxy-Efavirenz in Ethiopian Patients

We compared the pharmacokinetic (PK) exposure parameters of efavirenz (EFV) and its major inactive metabolite, 8-hydroxy-efavirenz (8-OH-EFV), in an open-label, single-sequence, and parallel design of HIV-infected and tuberculosis (TB)-HIV-coinfected Ethiopian patients in the HIV-TB Pharmagene study with 20 and 33 patients, respectively. Both treatment groups underwent PK sampling following oral 600 mg EFV in week 16 of initiating EFV-based combination antiretroviral therapy. The TB-HIV-coinfected group repeated the PK sampling 8 weeks after stopping rifampin (RIF)-based anti-TB treatment. Between-treatment group analysis indicated no significant effect of RIF-based anti-TB cotreatment on PK exposure parameters of EFV, nor was there a significant effect after controlling for sex or CYP2B6 genotype. However, RIF-based therapy in TB-HIV-coinfected patients had significantly increased 8-OH-EFV PK exposure measures and metabolic ratio relative to HIV-only patients, AUC_0-24 greater by 79%. The effect was more prominent in women and CYP2B6*6 carriers in within-sex and CYP2B6 genotype comparisons. Within-subject comparisons for AUC_0-24 and C_max when "on" and "off" RIF-based anti-TB cotreatment showed geometric mean ratios (90% confidence intervals) of 100.5% (98.7%-102.3%) and 100.2% (98.1%-102.4%), respectively, for EFV and 98.6% (95.5%-101.7%-) and 97.6% (92.2%-103.0%), respectively, for 8-OH-EFV. We report no significant influence of RIF-based anti-TB cotherapy on the EFV PK exposure measures. The study also calls for caution related to higher exposure to 8-OH-EFV during simultaneous coadministration of EFV and RIF-based anti-TB regimens, which may be associated with neurotoxicity, particularly in female patients and CYP2B6*6 carriers.