Substantial effect of efavirenz monotherapy on bilirubin levels in healthy volunteers

Mechanistic Modeling of the Drug-Drug Interaction Between Efavirenz and Dolutegravir: Is This Interaction Clinically Relevant When Switching From Efavirenz to Dolutegravir During Pregnancy?

Following the 2021 World Health Organization's updated recommendations on the management of HIV infection, millions of people living with HIV are currently switched from efavirenz-based antiretroviral therapy to dolutegravir-based antiretroviral therapy. Pregnant individuals transitioning from efavirenz to dolutegravir might be at increased risk of insufficient viral suppression in the immediate postswitch period because both efavirenz- and pregnancy-related increases in hormone levels induce enzymes involved in dolutegravir metabolism, namely, cytochrome P450 3A4 and uridine 5'-diphospho-glucuronosyltransferase 1A1. This study aimed at developing physiologically based pharmacokinetic models to simulate the switch from efavirenz to dolutegravir in the late second and third trimester. To this end, the drug-drug interaction between efavirenz and the uridine 5'-diphospho-glucuronosyltransferase 1A1 substrates dolutegravir and raltegravir was first simulated in nonpregnant subjects. After successful validation, the physiologically based pharmacokinetic models were translated to pregnancy and dolutegravir pharmacokinetics following efavirenz discontinuation were predicted. Modeling results indicated that, at the end of the second trimester, both efavirenz concentrations and dolutegravir trough concentrations fell below respective pharmacokinetic target thresholds (defined as reported thresholds producing 90%-95% of the maximum effect) during the time interval from 9.75 to 11 days after dolutegravir initiation. At the end of the third trimester, this time interval spanned from 10.3 days to >4 weeks after dolutegravir initiation. These findings suggest that dolutegravir exposure in the immediate post-efavirenz switch period during pregnancy may be suboptimal, leading to HIV viremia and, potentially, resistance. The clinical implications of these findings remain to be substantiated by future studies.

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Comparison of Metabolic Effects of Three Different Treatment Combinations with Retrospective Real-life Data in People Living with HIV

INTRODUCTION

Comorbidities are increasing in people living with HIV (PLHIV), and different treatment options have advantages and disadvantages. It is important to compare information from real-life treated cases. The aim of this study was to retrospectively evaluate the data on efficacy and clinical and laboratory findings during different antiretroviral therapies.

METHODS

Retrospective file data of 47 PLHIV using Dolutegravir and Lamivudine (3TC/DTG), Tenofovir Alafenamide Emtricitabine and Elvitegravir Cobicistat (EVG/c/TAF/FTC) and Tenofovir Disoproxil Fumarate and Emtricitabine and Efavirenz (EFV/FTC/TDF) were analyzed. Data of the patients at baseline and 12 months after antiretroviral therapy (ART) were compared.

RESULTS

About 47 PLHIV were included in the study. Of the patients, 22 (46.8%) were in the 3TC/DTG group, 19 (40.4%) in the EVG/c/TAF/FTC, and 6 (12.8%) in the EFV/FTC/TDF group. After 12 months of treatment, BMI, HIV-RNA, CD4, WBC, hemoglobin, MCV, PDW, RDW, platelet count, creatinine, eGFR, HDL, AST, glucose values of the 3TC/DTG group were significantly different (p<0.05). After 12 months of treatment, BMI, HIV-RNA, CD4 count, MCV, creatinine, eGFR, HDL, LDL, TG, TC, AST, and HOMA-IR values of the EVG/c/TAF/FTC treatment group were significantly different (p<0.05). After 12 months of treatment, HIV RNA, total bilirubin, and LDL values in the EFV/FTC/TDF treatment group were statistically different (p<0.05).

CONCLUSION

All treatment groups showed a decrease in HIV-RNA and an increase in CD4 at the end of one year. While CD4 elevation is lower in EFV recipients than in integrase inhibitor (INSTI) recipients, weight gain is higher in INSTI recipients. While the lipid profile was more positively affected in the 3TC/DTG group, lipid profiles were more negatively affected in the EVG/c/TAF/FTC group, although liver and kidney functions were preserved.

Influence of SULT1A1*2 Polymorphism on Plasma Efavirenz Concentration in Thai HIV-1 Patients

Purpose

Plasma efavirenz (EFV) concentrations within therapeutic levels are essential to successfully treat patients suffering from human immunodeficiency virus (HIV) type 1. In addition to the drug-metabolizing enzyme CYP2B6, other phase II drug-metabolizing enzymes and transporters may have an important role in the pharmacokinetics of EFV. Thus, the influence of phase II drug-metabolizing enzymes and drug transporters on plasma EFV levels was investigated in Thai HIV patients receiving EFV.

Patients and Methods

Genotyping was performed by TaqMan^® real-time PCR in 149 HIV-infected Thai adults, and plasma efavirenz concentration was measured by a validated high-performance liquid chromatography in 12 hours after dosing steady-state plasma samples at week 12 and 24.

Results

Patients with three or more copies of SULT1A1 had significantly lower median plasma EFV concentrations than those carrying two copies at week 12 (p=0.046) and SULT1A1*2 (c.638G>A) carriers had significantly lower median plasma EFV concentrations compared to those not carrying the variant at week 24 (p=0.048). However, no significant association was found after adjusting for CYP2B6 genotype.

Conclusion

Genetic variation in a combination of SULT1A1*2 and SULT1A1 copy number may contribute to variability in EFV metabolism and thereby may impact drug response. The influence of a combination between the SULT1A1 and CYP2B6 genotype on EFV pharmacokinetics should be further investigated in a larger study population.

Once-daily Doravirine for Initial Treatment of Adults Living With Human Immunodeficiency Virus-1: An Integrated Safety Analysis

BACKGROUND

A prespecified integrated safety analysis was conducted for 3 doravirine (DOR) double-blind trials (Phase IIb: P007 [NCT01632345]; Phase III: DRIVE-FORWARD [NCT02275780] and DRIVE-AHEAD [NCT02403674]).

METHODS

DOR (100 mg) arms from these trials were compared with darunavir plus ritonavir (DRV+r) in DRIVE-FORWARD and efavirenz (EFV) in P007 and DRIVE-AHEAD. Background therapies were emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) in P007; abacavir/lamivudine (ABC/3TC) or FTC/TDF in DRIVE-FORWARD; and 3TC/TDF for DOR and FTC/TDF for EFV in DRIVE-AHEAD. The primary endpoint was the proportion of participants discontinuing due to adverse events (AEs) through Week 48.

RESULTS

Discontinuation rates due to AEs were similar for participants on DOR and DRV+r (2.5% vs 3.1%, respectively) and lower for those on DOR than for those on EFV (2.5% vs 6.6%, respectively). Rates of drug-related AEs for DOR, DRV+r, and EFV were 30.9%, 32.1%, and 61.4%, respectively. In an analysis of DOR versus EFV, the treatment difference for discontinuations due to AEs was -3.4%, favoring DOR (95% confidence interval -6.2 to -0.8; P = .012). Fewer participants experienced neuropsychiatric AEs on DOR than on EFV (25.0% vs 55.9%, respectively), and fewer experienced diarrhea on DOR than on DRV+r (12.4% vs 22.5%, respectively). Changes from baseline in most lipid parameters also favored DOR.

CONCLUSIONS

At Week 48, DOR at 100 mg had a favorable safety profile compared with EFV or DRV+r and a favorable tolerability profile compared with EFV.

CLINICAL TRIALS REGISTRATION

NCT01632345; NCT02275780 and NCT02403674.

Influence of Uridine Diphosphate Glucuronosyltransferase Family 1 Member A1 and Solute Carrier Organic Anion Transporter Family 1 Member B1 Polymorphisms and Efavirenz on Bilirubin Disposition in Healthy Volunteers

Chronic administration of efavirenz is associated with decreased serum bilirubin levels, probably through induction of UGT1A1 We assessed the impact of efavirenz monotherapy and UGT1A1 phenotypes on total, conjugated, and unconjugated serum bilirubin levels in healthy volunteers. Healthy volunteers were enrolled into a clinical study designed to address efavirenz pharmacokinetics, drug interactions, and pharmacogenetics. Volunteers received multiple oral doses (600 mg/day for 17 days) of efavirenz. Serum bilirubin levels were obtained at study entry and 1 week after completion of the study. DNA genotyping was performed for UGT1A1 [*80 (C>T), *6 (G>A), *28 (TA₇), *36 (TA₅), and *37 (TA₈)] and for SLCO1B1 [*5 (521T>C) and *1b (388A>G] variants. Diplotype predicted phenotypes were classified as normal, intermediate, and slow metabolizers. Compared with bilirubin levels at screening, treatment with efavirenz significantly reduced total, conjugated, and unconjugated bilirubin. After stratification by UGT1A1 phenotypes, there was a significant decrease in total bilirubin among all phenotypes, conjugated bilirubin among intermediate metabolizers, and unconjugated bilirubin among normal and intermediate metabolizers. The data also show that UGT1A1 genotype predicts serum bilirubin levels at baseline, but this relationship is lost after efavirenz treatment. SLCO1B1 genotypes did not predict bilirubin levels at baseline or after efavirenz treatment. Our data suggest that efavirenz may alter bilirubin disposition mainly through induction of UGT1A1 metabolism and efflux through multidrug resistance-associated protein 2. SIGNIFICANCE STATEMENT: Efavirenz likely alters the pharmacokinetics of coadministered drugs, potentially causing lack of efficacy or increased adverse effects, as well as the disposition of endogenous compounds relevant in homeostasis through upregulation of UGT1A1 and multidrug resistance-associated protein 2. Measurement of unconjugated and conjugated bilirubin during new drug development may provide mechanistic understanding regarding enzyme and transporters modulated by the new drug.

Lipid Peroxidation and Altered Antioxidant Profiles with Pediatric HIV Infection and Antiretroviral Therapy in Addis Ababa, Ethiopia

HIV- and highly active antiretroviral therapy (HAART)-associated elevations in oxidative stress likely play a role in incomplete immune reconstitution, opportunistic infections and non-AIDS co-morbidities. We aimed to test the hypothesis that children living with HIV exhibit elevated markers of oxidative stress and reduced antioxidant profiles and that HAART-therapy will exacerbate these differences. HIV-positive HAART-naïve (n = 50) and HAART-treated (n = 50) and HIV-negative control (n = 50) participants, 3-15 years of age, were recruited from Black Lion Hospital in Ethiopia. Serum malondialdehyde (MDA) and bilirubin were higher and vitamin C and zinc were lower in HAART-naïve and HAART-treated compared with HIV-negative subjects and higher in HAART-treated compared with HAART-naïve subjects. Uric acid was higher in HAART-naïve compared with HAART-treated and HIV-negative subjects. Differences in MDA and several antioxidants were also observed across treatment regimens. Thus, children living with HIV exhibited systemic elevations in oxidative stress and reduction in antioxidants, which are exacerbated with HAART therapy.

The role of glucuronidation in drug resistance

The final therapeutic effect of a drug candidate, which is directed to a specific molecular target strongly depends on its absorption, distribution, metabolism and excretion (ADME). The disruption of at least one element of ADME may result in serious drug resistance. In this work we described the role of one element of this resistance: phase II metabolism with UDP-glucuronosyltransferases (UGTs). UGT function is the transformation of their substrates into more polar metabolites, which are better substrates for the ABC transporters, MDR1, MRP and BCRP, than the native drug. UGT-mediated drug resistance can be associated with (i) inherent overexpression of the enzyme, named intrinsic drug resistance or (ii) induced expression of the enzyme, named acquired drug resistance observed when enzyme expression is induced by the drug or other factors, as food-derived compounds. Very often this induction occurs via ligand binding receptors including AhR (aryl hydrocarbon receptor) PXR (pregnane X receptor), or other transcription factors. The effect of UGT dependent resistance is strengthened by coordinate action and also a coordinate regulation of the expression of UGTs and ABC transporters. This coupling of UGT and multidrug resistance proteins has been intensively studied, particularly in the case of antitumor treatment, when this resistance is "improved" by differences in UGT expression between tumor and healthy tissue. Multidrug resistance coordinated with glucuronidation has also been described here for drugs used in the management of epilepsy, psychiatric diseases, HIV infections, hypertension and hypercholesterolemia. Proposals to reverse UGT-mediated drug resistance should consider the endogenous functions of UGT.

NiO–ZrO2 nanocomposite modified electrode for the sensitive and selective determination of efavirenz, an anti-HIV drug

A highly sensitive NiO–ZrO₂ nanocomposite modified electrode was fabricated for trace analysis of efavirenz in pharmaceutical and biological samples.