The Effect of Gene Variants on Levonorgestrel Pharmacokinetics When Combined With Antiretroviral Therapy Containing Efavirenz or Nevirapine

Exploring the impact of pharmacogenetics on personalized medicine: A systematic review

INTRODUCTION

Pharmacogenetics evaluates how genetic variations influence drug responses. Nowadays, genetic tests have advanced, becoming more affordable, and its integration is supported by stronger clinical evidence. Guidelines such as those from CPIC (Clinical Pharmacogenetics Implementation Consortium) and resources like PharmGKB facilitate genotype-based prescribing; and organizations like the FDA promote genetic testing before initiating certain medications. Preventive pharmacogenetic panels seem promising, but further research on biomarkers and diverse populations is needed. The aim of this review is to analyze recent evidence on the genotype-drug response relationship to examine how the genetic profile of patients influences the clinical response to treatments, and analyze the areas of research that need further study to advance towards a genetic-based precision medicine.

MATERIALS AND METHODS

A systematic search was conducted on PubMed to identify articles investigating the genotype-drug response relationship. The search strategy included terms such as "pharmacogenetics", "personalized treatment", "precision medicine", "dose adjustment", "individualized dosing", "clinical routine" and "clinical practice." Clinical trials, observational studies, and meta-analyses published in English or Spanish between 2013 and 2023 were included. The initial search resulted in a total of 136 articles for analysis.

RESULTS

49 articles were included for the final analysis following review by two investigators. A relationship between genetic polymorphisms and drug response or toxicity was found for drugs such as opioids, GLP-1 agonists, tacrolimus, oral anticoagulants, antineoplastics, atypical antipsychotics, efavirenz, clopidogrel, lamotrigine, anti-TNF-α agents, voriconazole, antidepressants, or statins. However, for drugs like metformin, quetiapine, irinotecan, bisoprolol, and anti-VEGF agents, no statistically significant association between genotype and response was found.

CONCLUSION

The studies analyzed in this review suggest a strong correlation between genetic variability and individual drug responses, supporting the use of pharmacogenetics for treatment optimization. However, for certain drugs like metformin or quetiapine, the influence of genotype on their response remains unclear. More studies with larger sample sizes, greater ethnic diversity, and consideration of non-genetic factors are needed. The lack of standardization in analysis methods and accessibility to genetic testing are significant challenges in this field. As a conclusion, pharmacogenetics shows immense potential in personalized medicine, but further research is required.

Exploring the impact of pharmacogenetics on personalized medicine: A systematic review

INTRODUCTION

Pharmacogenetics evaluates how genetic variations influence drug responses. Nowadays, genetic tests have advanced, becoming more affordable, and its integration is supported by stronger clinical evidence. Guidelines such as those from CPIC (Clinical Pharmacogenetics Implementation Consortium) and resources like PharmGKB facilitate genotype-based prescribing; and organizations like the FDA promote genetic testing before initiating certain medications. Preventive pharmacogenetic panels seem promising, but further research on biomarkers and diverse populations is needed. The aim of this review is to analyze recent evidence on the genotype-drug response relationship to examine how the genetic profile of patients influences the clinical response to treatments, and analyze the areas of research that need further study to advance towards a genetic-based precision medicine.

MATERIALS AND METHODS

A systematic search was conducted on PubMed to identify articles investigating the genotype-drug response relationship. The search strategy included terms such as "pharmacogenetics", "personalized treatment", "precision medicine", "dose adjustment", "individualizing dosing", "clinical routine", and "clinical practice." Clinical trials, observational studies, and meta-analyses published in English or Spanish between 2013 and 2023 were included. The initial search resulted in a total of 136 articles for analysis.

RESULTS

49 articles were included for the final analysis following review by 2 investigators. A relationship between genetic polymorphisms and drug response or toxicity was found for drugs such as opioids, GLP-1 agonists, tacrolimus, oral anticoagulants, antineoplastics, atypical antipsychotics, efavirenz, clopidogrel, lamotrigine, anti-TNFα agents, voriconazole, antidepressants, or statins. However, for drugs like metformin, quetiapine, irinotecan, bisoprolol, and anti-VEGF agents, no statistically significant association between genotype and response was found.

CONCLUSION

The studies analyzed in this review suggest a strong correlation between genetic variability and individual drug responses, supporting the use of pharmacogenetics for treatment optimization. However, for certain drugs like metformin or quetiapine, the influence of genotype on their response remains unclear. More studies with larger sample sizes, greater ethnic diversity, and consideration of non-genetic factors are needed. The lack of standardization in analysis methods and accessibility to genetic testing are significant challenges in this field. As a conclusion, pharmacogenetics shows immense potential in personalized medicine, but further research is required.

Drug-drug interactions between antiretrovirals and hormonal contraception: An updated systematic review

OBJECTIVE

To summarize and update information regarding drug-drug interactions (DDIs) between antiretrovirals (ARVs) and hormonal contraceptives (HCs).

STUDY DESIGN

Systematic review.

RESULTS

We included 49 articles, with clinical, ARV, or HC PK outcomes reported by 39, 25, and 30 articles, respectively, with some articles reporting outcomes in two or more categories. Fifteen of 18 articles assessing DDIs between efavirenz and progestin implants, emergency contraception, or combined hormonal intravaginal rings found higher pregnancy rates, luteal progesterone levels suggesting ovulation, or reduced progestin PK values. Five studies documented that CYP2B6 single nucleotide polymorphisms exacerbated this DDI. One cohort detected doubled bone density loss with concomitant depot medroxyprogesterone acetate (DMPA) and tenofovir disoproxil fumarate (TDF)-containing ART use versus TDF alone. No other studies described DDIs impacting clinical outcomes. Few adverse events were attributed to ARV-HC use with none exceeding Grade 2. Evidence quality was generally moderate, with dis-similar treatment and control groups, identifying and controlling for confounding, and minimizing attrition bias in the study design being the most frequent limitations.

CONCLUSION

TDF-DMPA DDIs warrant longer-term study on bone health and consideration of alternate combinations. For efavirenz-based ART, client counseling on relative risks, including both potential increase in pregnancy rate with concomitant efavirenz and implant use and lower pregnancy rates compared to other HCs even with concomitant efavirenz use, should continue to allow users comprehensive method choice.

IMPLICATIONS

Most ARVs and HCs may be used safely and effectively together. Efavirenz-based ART requires careful counseling and data for possible interactions between HCs and new ARV classes are anticipated.

A Physiologically-Based Pharmacokinetic Simulation to Evaluate Approaches to Mitigate Efavirenz-Induced Decrease in Levonorgestrel Exposure with a Contraceptive Implant

Background: Levonorgestrel implant is a highly effective hormonal contraceptive, but its efficacy may be compromised when used with cytochrome enzyme inducers such as efavirenz. The primary aim of this study was to evaluate methods of mitigating the drug interaction. Methods: Using a physiologically-based pharmacokinetic (PBPK) model for levonorgestrel that we developed within the Simcyp® program, we evaluated a higher dose of levonorgestrel implant, a lower dose of efavirenz, and the combination of both, as possible methods to mitigate the interaction. In addition, we investigated the impact on levonorgestrel total and unbound concentrations of other events likely to be associated with efavirenz coadministration: changes in plasma protein binding of levonorgestrel (as with displacement) and high variability of efavirenz exposure (as with genetic polymorphism of its metabolism). The range of fraction unbound tested was 0.6% to 2.6%, and the range of efavirenz exposure ranged from the equivalent of 200 mg to 4800 mg doses. Results: Levonorgestrel plasma concentrations at any given time with a standard 150 mg implant dose are predicted to be approximately 68% of those of control when given with efavirenz 600 mg and 72% of control with efavirenz 400 mg. With double-dose levonorgestrel, the predictions are 136% and 145% of control, respectively. A decrease in levonorgestrel plasma protein binding is predicted to primarily decrease total levonorgestrel plasma concentrations, whereas higher efavirenz exposure is predicted to decrease total and unbound concentrations. Conclusions: Simulations suggest that doubling the dose of levonorgestrel, particularly in combination with 400 mg daily efavirenz, may mitigate the drug interaction. Changes in levonorgestrel plasma protein binding and efavirenz genetic polymorphism may help explain differences between model predictions and clinical data but need to be studied further.

Potential biomarkers to predict return to fertility after discontinuation of female contraceptives-looking to the future

Nowadays there are multiple types of contraceptive methods, from reversible to permanent, for those choosing to delay pregnancy. Misconceptions about contraception and infertility are a key factor for discontinuation or the uptake of family planning methods. Regaining fertility (the ability to conceive) after contraceptive discontinuation is therefore pivotal. Technical studies to date have evaluated return to fertility by assessing pregnancy as an outcome, with variable results, or return to ovulation as a surrogate measure by assessing hormone levels (such as progesterone, LH, FSH) with or without transvaginal ultrasound. In general, relying on time to pregnancy as an indicator of return to fertility following contraceptive method discontinuation can be problematic due to variable factors independent of contraceptive effects on fertility, hormone clearance, and fertility recovery. Since the ability to conceive after contraceptive method discontinuation is a critical factor influencing product uptake, it is important to have robust biomarkers that easily and accurately predict the timing of fertility return following contraception and isolate that recovery from extrinsic and circumstantial factors. The main aim of this review is to summarize the current approaches, existing knowledge, and gaps in methods of evaluating return-to-fertility as well as to provide insights into the potential of new biomarkers to more accurately predict fertility restoration after contraceptive discontinuation. Biomarker candidates proposed in this document include those associated with folliculogenesis, cumulus cell expansion, follicular rupture and ovulation, and endometrial transport and receptivity which have been selected and scored on predefined criteria meant to evaluate their probable viability for advancement. The review also describes limitations, regulatory requirements, and a potential path to clinically testing these selected biomarkers. It is important to understand fertility restoration after contraceptive method discontinuation to provide users and health providers with accurate evidence-based information. Predictive biomarkers, if easy and low-cost, have the potential to enable robust evaluation of RTF, and provide potential users the information they desire when selecting a contraceptive method. This could lead to expanded uptake and continuation of modern contraception and inform the development of new contraceptive methods to widen user's family planning choices.

Pharmacogenetic interactions of efavirenz or rifampin and isoniazid with levonorgestrel emergency contraception during treatment of HIV or tuberculosis

OBJECTIVE

In AIDS Clinical Trials Group study A5375, a pharmacokinetic trial of levonorgestrel emergency contraception, double-dose levonorgestrel (3 mg, versus standard dose 1.5 mg) offset the induction effects of efavirenz or rifampin on plasma levonorgestrel exposure over 8 h post-dose (AUC 0-8h ). We characterized the pharmacogenetics of these interactions.

METHODS

Cisgender women receiving efavirenz- or dolutegravir-based HIV therapy, or on isoniazid-rifampin for tuberculosis, were followed after a single oral dose of levonorgestrel. Linear regression models, adjusted for BMI and age, characterized associations of CYP2B6 and NAT2 genotypes (which affect plasma efavirenz and isoniazid exposure, respectively) with levonorgestrel pharmacokinetic parameters.

RESULTS

Of 118 evaluable participants, 17 received efavirenz/levonorgestrel 1.5 mg, 35 efavirenz/levonorgestrel 3 mg, 34 isoniazid-rifampin/levonorgestrel 3 mg, and 32 (control group) dolutegravir/levonorgestrel 1.5 mg. There were 73 Black and 33 Asian participants. Regardless of genotype, women on efavirenz and isoniazid-rifampin had higher levonorgestrel clearance. In the efavirenz/levonorgestrel 3 mg group, CYP2B6 normal/intermediate metabolizers had levonorgestrel AUC 0-8h values similar to controls, while CYP2B6 poor metabolizers had AUC 0-8h values of 40% lower than controls. In the isoniazid-rifampin group, NAT2 rapid/intermediate acetylators had levonorgestrel AUC 0-8h values similar to controls, while NAT2 slow acetylators had AUC 0-8h values 36% higher than controls.

CONCLUSION

CYP2B6 poor metabolizer genotypes exacerbate the efavirenz-levonorgestrel interaction, likely by increased CYP3A induction with higher efavirenz exposure, making the interaction more difficult to overcome. NAT2 slow acetylator genotypes attenuate the rifampin-levonorgestrel interaction, likely by increased CYP3A inhibition with higher isoniazid exposure.

Pharmacokinetics of dose-adjusted levonorgestrel emergency contraception combined with efavirenz-based antiretroviral therapy or rifampicin-containing tuberculosis regimens

OBJECTIVES

To determine if double-dose levonorgestrel emergency contraception (EC) in combination with efavirenz or rifampicin, 2 drugs known to decrease levonorgestrel exposure, resulted in similar pharmacokinetics compared to standard-dose levonorgestrel EC without drug-drug interactions.

STUDY DESIGN

We conducted a phase 2, open-label, multicenter, partially randomized, 4 parallel group trial in pre-menopausal females ≥16 years old without an indication for EC and not on hormonal contraception. Participants on dolutegravir-based antiretroviral therapy (ART) received levonorgestrel 1.5 mg (control group); those on rifampicin-containing tuberculosis therapy received levonorgestrel 3 mg; those on efavirenz-based ART were randomized 1:2 to levonorgestrel 1.5 mg or 3 mg. Plasma was collected through 48 hours post-dose to assess levonorgestrel pharmacokinetics. Area under the concentration-time curve (AUC) over 8 hours was the primary outcome. Levonorgestrel pharmacokinetic parameters were compared between groups using geometric mean ratios (GMR) with 90% confidence intervals.

RESULTS

The median (Q1, Q3) age for all participants (n = 118) was 34 (27, 41) years and BMI was 23.2 (20, 26.3) kg/m2. Participants receiving levonorgestrel 1.5mg plus efavirenz (n = 17) had 50% lower AUC0-8h compared to the control group (n = 32) [0.50 (0.40, 0.62)]. Participants receiving levonorgestrel 3 mg had a similar AUC0-8h when receiving either efavirenz (n = 35) [0.99 (0.81, 1.20)] or rifampicin (n = 34) [1.16 (0.99, 1.36)] compared to control. Levonorgestrel 3 mg resulted in similar or higher maximum concentration with either efavirenz [1.17 (0.96, 1.41)] or rifampicin [1.27 (1.09, 1.49)] compared to the control group.

CONCLUSIONS

Doubling the dose of levonorgestrel EC successfully increased levonorgestrel exposure over the first 8 hours in participants receiving either efavirenz-based ART or rifampicin-containing tuberculosis therapy.

IMPLICATIONS

Adjusting levonorgestrel emergency contraception from 1.5 mg to 3 mg improves levonorgestrel pharmacokinetic exposure in participants receiving either efavirenz-based antiretroviral regimens or rifampicin-containing tuberculosis therapy. These data support guideline recommendations to double the dose of levonorgestrel emergency contraception in persons on medications that decrease levonorgestrel exposure by inducing levonorgestrel metabolism.

Effect of double-dose levonorgestrel subdermal implant in women taking efavirenz-based antiretroviral therapy: The DoubLNG pharmacokinetic study

OBJECTIVE

We evaluated the pharmacokinetics of double-dose levonorgestrel (LNG) implants to overcome the drug-drug interaction with efavirenz-based antiretroviral therapy (ART).

STUDY DESIGN

We conducted a nonrandomized, open-label, parallel-group, longitudinal pharmacokinetic study among Ugandan women ages 18-45 years. Participants with HIV on ART containing efavirenz 600 mg received 300 mg of LNG implants (Jadelle®, Bayer, New Zealand): 300LNG+ART group. We compared our outcomes with women without HIV using standard dose, 150 mg of LNG implants: 150LNG group. The implant was placed on day zero in both groups, and we quantified plasma LNG concentrations over 48 weeks post implant insertion. LNG pharmacokinetic parameters were estimated using noncompartmental techniques. Our primary outcome was the geometric mean ratio with 90% confidence intervals of LNG area under the concentration-time curve over 24 weeks (AUC_0-24w) between groups. Demographic data were described as median (interquartile range). A secondary outcome compared between-group percent of LNG concentrations ≥300 pg/mL, a minimum threshold selected a priori based on observed pregnancies in Ugandan women on standard-dose LNG implants plus efavirenz.

RESULTS

We enrolled 27 women in the 300LNG+ART group (34 [28.0 to 40.5] years and 61.0 [49.8-66.0] kg) and 19 women in the 150LNG group (33 [30.0 to 34.5] years and 64.9 [59.0 to 74.5] kg). LNG AUC_0-24w was 34% lower for 300LNG+ART versus 150LNG (geometric mean 9998 vs. 15,231 pg*week/mL, respectively [geometric mean ratio 0.66 (90% confidence intervals, 0.54 to 0.80)]). The percentage of participants with LNG concentrations ≥300 pg/mL was not statistically different between groups at week 24 (300LNG+ART: 74.1%; 150LNG: 89.5%; p = 0.27).

CONCLUSION

Double-dose LNG implant did not completely overcome the drug-drug interaction with efavirenz.

IMPLICATION

In women using ART containing efavirenz, placing two implant systems (300 mg) did not normalize LNG pharmacokinetics compared with the standard-dose implant (150 mg), and some women had evidence of ovulatory activity. Alternative ART without drug-drug interactions, such as dolutegravir, is recommended with contraceptive implants.

Magnitude of Drug–Drug Interactions in Special Populations

Drug–drug interactions (DDIs) are one of the most frequent causes of adverse drug reactions or loss of treatment efficacy. The risk of DDIs increases with polypharmacy and is therefore of particular concern in individuals likely to present comorbidities (i.e., elderly or obese individuals). These special populations, and the population of pregnant women, are characterized by physiological changes that can impact drug pharmacokinetics and consequently the magnitude of DDIs. This review compiles existing DDI studies in elderly, obese, and pregnant populations that include a control group without the condition of interest. The impact of physiological changes on the magnitude of DDIs was then analyzed by comparing the exposure of a medication in presence and absence of an interacting drug for the special population relative to the control population. Aging does not alter the magnitude of DDIs as the related physiological changes impact the victim and perpetrator drugs to a similar extent, regardless of their elimination pathway. Conversely, the magnitude of DDIs can be changed in obese individuals or pregnant women, as these conditions impact drugs to different extents depending on their metabolic pathway.

Pharmacogenetics of interaction between depot medroxyprogesterone acetate and efavirenz, rifampicin, and isoniazid during treatment of HIV and tuberculosis

OBJECTIVE

In AIDS Clinical Trials Group study A5338, concomitant rifampicin, isoniazid, and efavirenz was associated with more rapid plasma medroxyprogesterone acetate (MPA) clearance compared to historical controls without tuberculosis or HIV therapy. We characterized the pharmacogenetics of this interaction.

METHODS

In A5338, women receiving efavirenz-based HIV therapy and rifampicin plus isoniazid for tuberculosis underwent pharmacokinetic evaluations over 12 weeks following a 150-mg intramuscular injection of depot MPA. Data were interpreted with nonlinear mixed-effects modelling. Associations between individual pharmacokinetic parameters and polymorphisms relevant to rifampicin, isoniazid, efavirenz, and MPA were assessed.

RESULTS

Of 62 A5338 participants in four African countries, 44 were evaluable for pharmacokinetic associations, with 17 CYP2B6 normal, 21 intermediate, and 6 poor metabolizers, and 5 NAT2 rapid, 20 intermediate, and 19 slow acetylators. There were no associations between either CYP2B6 or NAT2 genotype and MPA Cmin at week 12, apparent clearance, Cmax, area under the concentration-time curve (AUC) or half-life, or unexplained interindividual variability in clearance, and uptake rate constant or mean transit time of the slow-release fraction (P > 0.05 for each). In exploratory analyses, none of 28 polymorphisms in 14 genes were consistently associated with MPA pharmacokinetic parameters, and none withstood correction for multiple testing.

CONCLUSIONS

Study A5338 suggested that more frequent depot MPA dosing may be appropriate for women receiving rifampicin, isoniazid, and efavirenz. The present results suggest that knowledge of CYP2B6 metabolizer or NAT2 acetylator status does not inform individualized DMPA dosing in this setting.

PharmVar GeneFocus: CYP2B6

The Pharmacogene Variation Consortium (PharmVar) catalogs star (*) allele nomenclature for the polymorphic human CYP2B6 gene. Genetic variation within the CYP2B6 gene locus impacts the metabolism or bioactivation of clinically important drugs. Of particular importance are efficacy and safety concerns regarding: efavirenz, which is used for the treatment of HIV type-1 infection; methadone, a mainstay in the treatment of opioid use disorder and as an analgesic; ketamine, used as an antidepressant and analgesic; and bupropion, which is prescribed to treat depression and for smoking cessation. This GeneFocus provides a comprehensive overview and summary of CYP2B6 and describes how haplotype information catalogued by PharmVar is utilized by the Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC).

Influence of selected polymorphisms in disposition genes on lumefantrine pharmacokinetics when coadministered with efavirenz

BACKGROUND

Coadministration of artemether-lumefantrine and efavirenz has been shown to result in significant interactions. The influence of functional genetic polymorphisms in selected CYPs on the magnitude of this interaction was investigated in pregnant and nonpregnant adults.

METHOD

A standard 3-day regimen of artemether-lumefantrine was administered to each patient on steady-state efavirenz-based antiretroviral therapy (ART). Pharmacokinetic parameters were obtained from intensive plasma concentration-time data. Genotyping data were tested for compliance with Hardy-Weinberg equilibrium by Chi-square test. Linear regressions, Mann-Whitney U-test or Kruskal-Wallis tests were conducted to examine the association of lumefantrine plasma level with CYP2B6 c.516G>T, NR1I3 152c-1089T>C, CYP2B6 c.983T>C, CYP3A5*3 and CYP3A4*22.

RESULTS

Among a total of 69 malaria-HIV coinfected patients (34 nonpregnant and 35 pregnant), median (interquartile range) age was 33 (27-36.5) years and body weight was 59.5 (50-67.5) kg. In nonpregnant group, CYP2B6 c.516G>T was significantly associated with lower log Cday 7 of lumefantrine using multivariate linear regressions (β = -0.239; P = 0.013). In 59% of women with CYP2B6 c.516T, Cday 7 of lumefantrine was below the target of 280 ng/mL compared to 47% in the noncarriers. CYP2B6 c.983T>C significantly associated with higher log Cday 7 of desbutyl lumefantrine in both pregnant (β = 0.383; P = 0.033) and nonpregnant (β = 0.395; P = 0.023) groups. Composite genotypes for both CYP2B6 Single-nucleotide polymorphisms strongly associated with lumefantrine plasma concentration. An associative trend between lumefantrine pharmacokinetics and NR1I3 152c-1089T>C genotypes indicated that 70% of the Cday 7 of lumefantrine in those with NR1I3 152c-1089TT genotype was below 280 ng/mL compared to 53% in those with NR1I3 152c-1089CC or CT genotype.

CONCLUSION

The findings revealed that the efavirenz-lumefantrine interaction was accentuated in the group with CYP2B6 c.516T, c.983C and NR1I3 152c-1089T alleles. This warrants further investigations of other drug-drug interactions for optimising dosing in genetically defined subgroups, particularly during drug development.

Effect of efavirenz on levonorgestrel concentrations among Malawian levonorgestrel implant users for up to 30 months of concomitant use: a subanalysis of a randomized clinical trial

Objectives

Our primary objective was to compare geometric mean levonorgestrel concentrations between levonorgestrel implant users who were or were not taking the antiretroviral efavirenz, for up to 30 months after implant initiation. Our secondary objective was to evaluate the pregnancy rate among levonorgestrel implant users on efavirenz.

Study design

We performed a subanalysis of 42 Malawian women randomized to initiate the levonorgestrel implant as part of a parent randomized clinical trial. Our subset included 30 HIV-infected women taking efavirenz and 12 HIV-uninfected women not taking efavirenz. They underwent urine pregnancy testing every 3 months and serum levonorgestrel testing at day 3 and months 1, 3, 6, 12, 18, 24, 27 and 30 after implant initiation. Geometric mean levonorgestrel concentrations were calculated for efavirenz users and non-efavirenz users at each time point.

Results

The geometric mean levonorgestrel concentrations were lower for efavirenz users than non-efavirenz users at every time point; the geometric mean ratio for efavirenz users:non-efavirenz users ranged from 0.60 [90% confidence interval (CI) 0.46–0.79] at 1 month to 0.27 (90% CI 0.12–0.61) at 30 months after implant insertion. No pregnancies occurred over 60 woman-years of concomitant levonorgestrel implant and efavirenz use, although 11 women had levonorgestrel concentrations < 180 pg/mL (the previously suggested minimum threshold concentration for efficacy).

Conclusions

Efavirenz users had lower levonorgestrel concentrations than non-efavirenz users, and one third of our concomitant efavirenz and levonorgestrel implant users had concentrations < 180 pg/mL. Continued evaluation of the contraceptive efficacy of the levonorgestrel implant may be needed for efavirenz users.

Implications

Among 42 Malawian women using the levonorgestrel implant for contraception, women who were taking the antiretroviral efavirenz had lower serum levonorgestrel concentrations than women who were not taking efavirenz. However, none of the women who were taking efavirenz became pregnant over 60 women-years of follow-up.

Pharmacogenetic interactions between antiretroviral drugs and vaginally administered hormonal contraceptives

OBJECTIVE

In AIDS Clinical Trials Group study A5316, efavirenz lowered plasma concentrations of etonogestrel and ethinyl estradiol, given as a vaginal ring, while atazanavir/ritonavir increased etonogestrel and lowered ethinyl estradiol concentrations. We characterized the pharmacogenetics of these interactions.

METHODS

In A5316, women with HIV enrolled into control (no antiretrovirals), efavirenz [600 mg daily with nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs)], and atazanavir/ritonavir (300/100 mg daily with NRTIs) groups. On day 0, a vaginal ring was inserted, releasing etonogestrel/ethinyl estradiol 120/15 μg/day. Intensive plasma sampling for antiretrovirals was obtained on days 0 and 21, and single samples for etonogestrel and ethinyl estradiol on days 7, 14, and 21. Seventeen genetic polymorphisms were analyzed.

RESULTS

The 72 participants in this analysis included 25, 24 and 23 in the control, efavirenz, and atazanavir/ritonavir groups, respectively. At day 21 in the efavirenz group, CYP2B6 genotype was associated with increased plasma efavirenz exposure (P = 3.2 × 10), decreased plasma concentrations of etonogestrel (P = 1.7 × 10), and decreased ethinyl estradiol (P = 6.7 × 10). Compared to controls, efavirenz reduced median etonogestrel concentrations by at least 93% in CYP2B6 slow metabolizers versus approximately 75% in normal and intermediate metabolizers. Efavirenz reduced median ethinyl estradiol concentrations by 75% in CYP2B6 slow metabolizers versus approximately 41% in normal and intermediate metabolizers.

CONCLUSION

CYP2B6 slow metabolizer genotype worsens the pharmacokinetic interaction of efavirenz with hormonal contraceptives administered by vaginal ring. Efavirenz dose reduction in CYP2B6 slow metabolizers may reduce, but will likely not eliminate, this interaction.

Meta-analysis of the effect of CYP2B6, CYP2A6, UGT2B7 and CAR polymorphisms on efavirenz plasma concentrations

BACKGROUND

Efavirenz primary metabolism is catalysed by CYP2B6 with minor involvement of CYP2A6. Subsequently, phase I metabolites are conjugated by UGT2B7, and constitutive androstane receptor (CAR) has been shown to transcriptionally regulate many relevant enzymes and transporters. Several polymorphisms occurring in the genes coding for these proteins have been shown to impact efavirenz pharmacokinetics in some but not all studies.

OBJECTIVES

A meta-analysis was performed to assess the overall effect of CYP2B6 rs3745274, CYP2A6 (rs28399454, rs8192726 and rs28399433), UGT2B7 (rs28365062 and rs7439366) and NR1I3 (rs2307424 and rs3003596) polymorphisms on mid-dose efavirenz plasma concentrations.

METHODS

Following a literature review, pharmacokinetic parameters were compiled and a meta-analysis for these variants was performed using Review Manager and OpenMetaAnalyst. A total of 28 studies were included.

RESULTS

Unsurprisingly, the analysis confirmed that individuals homozygous for the T allele for CYP2B6 rs3745274 had significantly higher efavirenz concentrations than those homozygous for the G allele [weighted standard mean difference (WSMD) = 2.98; 95% CI 2.19-3.76; P < 0.00001]. A subgroup analysis confirmed ethnic differences in frequency but with a similar effect size in each ethnic group (P = 0.96). Associations with CYP2A6 and UGT2B7 variants were not statistically significant, but T homozygosity for CAR rs2307424 was associated with significantly lower efavirenz concentrations than in C homozygotes (WSMD = -0.32; 95% CI -0.59 to -0.06; P = 0.02).

CONCLUSIONS

This meta-analysis provides the overall effect size for the impact of CYP2B6 rs3745274 and NR1I3 rs2307424 on efavirenz pharmacokinetics. The analysis also indicates that some previous associations were not significant when interrogated across studies.

Effect of patient genetics on etonogestrel pharmacokinetics when combined with efavirenz or nevirapine ART

BACKGROUND

We previously demonstrated that etonogestrel concentrations were 82% lower in women using etonogestrel contraceptive implants plus efavirenz-based ART compared with women not receiving ART.

OBJECTIVES

To investigate the genetic contribution to this previously observed drug-drug interaction through studying SNPs in genes known to be involved in efavirenz, nevirapine or etonogestrel metabolism in the same group of women.

PATIENTS AND METHODS

Here, we present a secondary analysis evaluating SNPs involved in efavirenz, nevirapine and etonogestrel metabolism and associated etonogestrel pharmacokinetics among 57 women, 19 not receiving ART (control group), 19 receiving efavirenz- (600 mg daily) based ART and 19 receiving nevirapine- (200 mg twice daily) based ART. Associations between patient genotype and etonogestrel pharmacokinetic parameters were determined through univariate and multivariate linear regression. This study was registered at clinicaltrials.gov (NCT02082652).

RESULTS

Within the control group, CYP2B6 983 T>C was associated with 27% higher etonogestrel Cmax and 28% higher AUC0-24weeks. In the efavirenz group CYP2B6 516 G>T was associated with 43% lower etonogestrel Cmin and 34% lower AUC0-24weeks. For participants receiving nevirapine, NR1I2 63396 C>T was associated with 39% lower etonogestrel Cmin and 37% lower AUC0-24weeks.

CONCLUSIONS

This study demonstrates the influence of pharmacogenetics on the extent of drug-drug interactions between etonogestrel and efavirenz- or nevirapine-based ART. Efavirenz plus the etonogestrel contraceptive implant results in a detrimental drug-drug interaction irrespective of patient genetics, which is worsened in women possessing variant alleles for these CYP2B6 SNPs.

Interactions between Hormonal Contraception and Anti-Retroviral Therapy: An Updated Review

Purpose of review

Hormonal contraception provides women living with HIV the ability to control their fertility and avoid pregnancy-related morbidity. Due to shared metabolic pathways, there has been concern over drug-drug interactions between hormonal contraception and anti-retroviral therapy, which may affect the drugs' safety and efficacy. This article aims to provide an updated review of the most recent data around hormonal contraceptives and anti-retroviral therapy.

Recent findings

Prior data have suggested possible pharmacologic interactions between certain hormonal contraceptives and anti-retroviral therapy. The most significant interactions implicated include those between progestin-based contraceptive implants and efavirenz as well as between combined hormonal contraceptives and protease inhibitors. Most past studies, however, feature small sample sizes with few clinical outcomes reported.

Summary

Recent data since 2017 have largely affirmed prior studies on this topic, showing possible pharmacokinetic relationships between certain contraceptives and anti-retrovirals. Notably, while the effectiveness of progestin-based contraceptives, specifically the implant, appears reduced with efavirenz use, the overall effectiveness may remain higher than most other contraceptive methods. Larger studies are needed to provide further guidance before contraceptive-prescribing recommendations can be changed.

A pharmacokinetic and pharmacogenetic evaluation of contraceptive implants and antiretroviral therapy among women in Kenya and Uganda

OBJECTIVES

To evaluate pharmacokinetics and pharmacogenetics of contraceptive implant progestin concentrations in HIV-positive women initiating efavirenz (EFV)-containing or nevirapine (NVP)-containing antiretroviral therapy (ART).

DESIGN

We analyzed stored samples from women self-reporting implant use in the Partners PrEP Study.

METHODS

Plasma samples collected every 6 months were analyzed for levonorgestrel and etonogestrel concentrations. Progestin concentrations from samples collected after ART initiation were compared with pre-ART concentrations for intraindividual comparisons. We used adjusted linear mixed models to compare hormone concentrations between individuals on EFV and NVP to a no ART group. We then evaluated whether possessing certain alleles with known or possible influences on EFV, NVP, or progestin metabolism were associated with changes in progestin concentrations or modified the association between ART use and progestin concentrations.

RESULTS

Our analysis included 11 women who initiated EFV, 13 who initiated NVP, and 36 who remained ART-naive. In the EFV group, the adjusted geometric mean ratio (aGMR) of levonorgestrel was 0.39 [90% confidence intervals (0.31, 0.49); P < 0.001] and the etonogestrel aGMR was 0.51 (0.34, 0.76; P = 0.006) compared with the control group. No difference was observed in the NVP group compared with controls [levonorgestrel 0.93 (0.74, 1.18); P = 0.64; etonogestrel 1.07 (0.77, 1.50); P = 0.73]. Possession of four allele variants were found to result in further reductions in progestin concentrations among those receiving EFV.

CONCLUSION

Concomitant use of EFV significantly reduces levonorgestrel or etonogestrel concentrations by 61 and 49%, respectively, compared with no ART use. We also report allelic variants in hepatic enzymes that influenced the extent of the observed drug-interaction between progestins and EFV.

CYP2B6 Genotype-Dependent Inhibition of CYP1A2 and Induction of CYP2A6 by the Antiretroviral Drug Efavirenz in Healthy Volunteers

We investigated the effect of efavirenz on the activities of cytochrome P450 (CYP)1A2, CYP2A6, xanthine oxidase (XO), and N-acetyltransferase 2 (NAT2), using caffeine as a probe. A single 150 mg oral dose of caffeine was administered to healthy volunteers (n = 58) on two separate occasions; with a single 600 mg oral dose of efavirenz and after treatment with 600 mg/day efavirenz for 17 days. Caffeine and its metabolites in plasma and urine were quantified using liquid chromatography/tandem-mass spectrometry. DNA was genotyped for CYP2B6*4 (785A>G), CYP2B6*9 (516G>T), and CYP2B6*18 (983T>C) alleles using TaqMan assays. Relative to single-dose efavirenz treatment, multiple doses of efavirenz decreased CYP1A2 (by 38%) and increased CYP2A6 (by 85%) activities (P < 0.05); XO and NAT2 activities were unaffected. CYP2B6*6*6 genotype was associated with lower CYP1A2 activity following both single and multiple doses of efavirenz. No similar association was noted for CYP2A6 activity. This is the first report showing that efavirenz reduces hepatic CYP1A2 and suggesting chronic efavirenz exposure likely enhances the elimination of CYP2A6 substrates. This is also the first to report the extent of efavirenz-CYP1A2 interaction may be efavirenz exposure-dependent and CYP2B6 genotype-dependent.

Meta-analysis of the associations of CYP2B6-516G>T polymorphisms with efavirenz-induced central nervous system side effects and virological outcome in HIV-infected adults

Clinical data on the relationships of cytochrome P450 (CYP2) B6 516G>T polymorphisms with efavirenz-induced central nervous system (CNS) side effects and virological response in HIV-infected adults are controversial. We sought to analyze the associations by meta-analysis. To identify eligible studies, we systematically searched PubMed, Embase, ScienceDirect, and Web of Science. The strength of the associations was measured by odds ratio (OR) and effect size (ES) with 95% confidence interval (CI). Seventeen studies comprising a total of 3598 HIV-infected adults were included. The results showed that the CYP2B6-516 GG genotype was significantly associated with a decreased risk of efavirenz-induced CNS side effects compared with the GT and TT genotypes (GG + GT vs. TT: OR = 0.60, 95% CI = 0.41-0.87, P = 0.006; GG vs. GT + TT: OR = 0.68, 95% CI = 0.51-0.91, P = 0.008; GG vs. GT: OR = 0.70, 95% CI = 0.51-0.94, P = 0.018), and there was no significant association between the genetic variants GT and TT (GT vs. TT: OR = 0.82, 95% CI = 0.54-1.26, P = 0.372). However, there was no significant association between CYP2B6-516 GG and GT + TT genotypes in virological response (GT + TT vs. GG: ES = 1.06, 95% CI = 0.95-1.18, P = 0.321; OR = 1.01, 95% CI = 0.65-1.58, P = 0.963). Taken together, our results demonstrated that compared with the normal efavirenz clearance genotype CYP2B6-516 GG, the slow and very slow efavirenz clearance genotypes GT and TT were significantly associated with an increased risk of efavirenz-induced CNS side effects but not an increased virological response. To promote the tolerance of efavirenz, it is better to adjust the dosage of efavirenz according to the polymorphisms of CYP2B6-516 in HIV-infected adults.

Antiretroviral therapy and vaginally administered contraceptive hormones: a three-arm, pharmacokinetic study

BACKGROUND

Drug-drug interactions between orally administered antiretroviral therapy (ART) and hormones released from an intravaginal ring are not known. We hypothesised that ART containing either efavirenz or ritonavir-boosted atazanavir would alter plasma concentrations of vaginally administered etonogestrel and ethinylestradiol but that ART concentrations would be unchanged during use of an intravaginal ring.

METHODS

We did a parallel, three-group, pharmacokinetic evaluation at HIV clinics in Asia (two sites), South America (five), sub-Saharan Africa (three), and the USA (11) between Dec 30, 2014, and Sept 12, 2016. We enrolled women with HIV who were either ART-naive (control group; n=25), receiving efavirenz-based ART (n=25), or receiving atazanavir-ritonavir-based ART (n=24). Women receiving ART were required to be on the same regimen for at least 30 days, with 400 copies or less per mL of plasma HIV-1 RNA; women not receiving ART had CD4 counts of 350 cells per μL or less. We excluded participants who had a bilateral oophorectomy or conditions that were contraindicated in the intravaginal ring product labelling. An intravaginal ring releasing etonogestrel and ethinylestradiol was inserted at entry (day 0). Single plasma samples for hormone concentrations were collected on days 7, 14, and 21 after intravaginal ring insertion. The primary outcome was the plasma concentration of etonogestrel and ethinylestradiol on day 21. Etonogestrel and ethinylestradiol concentrations were compared between each ART group and the control group by geometric mean ratio (GMR) with 90% CIs and Wilcoxon rank-sum test. As secondary outcomes, efavirenz or ritonavir-boosted atazanavir concentrations were assessed by 8-h intensive pharmacokinetic sampling at entry before intravaginal ring insertion and before intravaginal ring removal on day 21. Antiretroviral areas under the concentration-time curve (AUC0-8 h) were compared before and after intravaginal ring insertion by GMR (90% CI) and Wilcoxon signed-rank test. This study is registered with ClinicalTrials.gov, number NCT01903031.

FINDINGS

Between Dec 30, 2014, and Sept 12, 2016, we enrolled 84 participants in the study; ten participants were excluded from the primary hormone analysis. 74 participants met the primary endpoint: 25 in the control group, 25 in the efavirenz group, and 24 in the atazanavir group. On day 21 of intravaginal ring use, participants receiving efavirenz had 79% lower etonogestrel (GMR 0·21, 90% CI 0·16-0·28; p<0·0001) and 59% lower ethinylestradiol (0·41, 0·32-0·52; p<0·0001) concentrations compared with the control group. By contrast, participants receiving ritonavir-boosted atazanavir had 71% higher etonogestrel (1·71, 1·37-2·14; p<0·0001), yet 38% lower ethinylestradiol (0·62, 0·49-0·79; p=0·0037) compared with the control group. The AUC0-8 h of efavirenz or atazanavir did not differ between the groups.

INTERPRETATION

Hormone exposure was significantly lower when an intravaginal ring contraceptive was combined with efavirenz-based ART. Further studies designed to examine pharmacodynamic endpoints, such as ovulation, when intravaginal ring hormones are combined with efavirenz are warranted.

FUNDING

National Institutes of Health, through the AIDS Clinical Trials Group and the International Maternal Pediatric Adolescent AIDS Clinical Trials Network, National Institute of Allergy and Infectious Diseases, Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute of Mental Health.

Physiologically based pharmacokinetic modelling prediction of the effects of dose adjustment in drug-drug interactions between levonorgestrel contraceptive implants and efavirenz-based ART

Background

HIV-positive women receiving efavirenz-based ART and levonorgestrel contraceptive implants are at risk of low levonorgestrel exposure and unintended pregnancy.

Objectives

To investigate clinically applicable dose-adjustment strategies to overcome the known drug-drug interaction (DDI) between levonorgestrel and efavirenz, using a physiologically based pharmacokinetic (PBPK) modelling-based approach.

Methods

A PBPK model was qualified against clinical data to predict levonorgestrel plasma concentrations when standard-dose (150 mg) levonorgestrel implants were administered alone (control group), as well as when standard-dose or increased-dose (300 mg) levonorgestrel implants were coadministered with either 600 or 400 mg of efavirenz.

Results

No difference was seen between in vivo clinical and PBPK-model-simulated levonorgestrel plasma concentrations (P > 0.05). Simulated levonorgestrel plasma concentrations were ∼50% lower at 48 weeks post-implant-placement in virtual individuals receiving standard-dose levonorgestrel with either 600 or 400 mg of efavirenz compared with the control group (efavirenz:control geometric mean ratio = 0.42 and 0.49, respectively). Conversely, increased-dose levonorgestrel in combination with either 600 or 400 mg of efavirenz was sufficient to restore levonorgestrel concentrations to levels similar to those observed in the 150 mg levonorgestrel control group 48 weeks post-implant-placement (efavirenz:control geometric mean ratio = 0.86 and 1.03, respectively).

Conclusions

These results suggest that the clinically significant DDI between efavirenz and levonorgestrel is likely to persist despite efavirenz dose reduction, whereas dose escalation of implantable levonorgestrel may represent a successful clinical strategy to circumvent efavirenz-levonorgestrel DDIs and will be of use to inform clinical trial design to assess coadministration of efavirenz and levonorgestrel implants.

Effect of Pregnancy on the Pharmacokinetic Interaction between Efavirenz and Lumefantrine in HIV-Malaria Coinfection

Artemether-lumefantrine is often coadministered with efavirenz-based antiretroviral therapy for malaria treatment in HIV-infected women during pregnancy. Previous studies showed changes in lumefantrine pharmacokinetics due to interaction with efavirenz in nonpregnant adults. The influence of pregnancy on this interaction has not been reported. This pharmacokinetic study involved 35 pregnant and 34 nonpregnant HIV-malaria-coinfected women receiving efavirenz-based antiretroviral therapy and was conducted in four health facilities in Nigeria. Participants received a 3-day standard regimen of artemether-lumefantrine for malaria treatment, and intensive pharmacokinetic sampling was conducted from 0.5 to 96 h after the last dose. Plasma efavirenz, lumefantrine, and desbutyl-lumefantrine were quantified using validated assays, and pharmacokinetic parameters were derived using noncompartmental analysis. The median middose plasma concentrations of efavirenz were significantly lower in pregnant women (n = 32) than in nonpregnant women (n = 32) at 1,820 ng/ml (interquartile range, 1,300 to 2,610 ng/ml) versus 2,760 ng/ml (interquartile range, 2,020 to 5,640 ng/ml), respectively (P = 0.006). The lumefantrine area under the concentration-time curve from 0 to 96 h was significantly higher in pregnant women (n = 27) at 155,832 ng · h/ml (interquartile range, 102,400 to 214,011 ng · h/ml) than nonpregnant women at 90,594 ng · h/ml (interquartile range, 58,869 to 149,775 ng · h/ml) (P = 0.03). A similar trend was observed for the lumefantrine concentration at 12 h after the last dose of lumefantrine, which was 2,870 ng/ml (interquartile range, 2,180 to 4,880 ng/ml) versus 2,080 ng/ml (interquartile range, 1,190 to 2,970 ng/ml) in pregnant and nonpregnant women, respectively (P = 0.02). The lumefantrine-to-desbutyl-lumefantrine ratio also tended to be lower in pregnant women than in nonpregnant women (P = 0.076). Overall, pregnancy tempered the extent of efavirenz-lumefantrine interactions, resulting in increased lumefantrine exposure. However, any consideration of dosage adjustment for artemether-lumefantrine to enhance exposure in this population needs to be based on data from a prospective study with safety and efficacy endpoints.

Genetic variations of the xenoreceptors NR1I2 and NR1I3 and their effect on drug disposition and response variability

NR1I2 (PXR) and NR1I3 (CAR) are nuclear receptors that are classified as xenoreceptors. Upon activation by various xenobiotics, including marketed drugs, they regulate the transcription level of major drug-metabolizing enzymes and transporters and facilitate the elimination of xenobiotics from the body. The modulation of the activity of these two xenoreceptors by various ligands is a major source of pharmacokinetic variability of environmental origin. NR1I2 and NR1I3 genetic polymorphisms can affect the pharmacokinetics and therapeutic response to many drugs, such as irinotecan, tacrolimus and atazanavir. This review provides an overview of NR1I2 and NR1I3 pharmacogenetic studies in various therapeutic fields (oncology, immunomodulation and infectiology) and discusses the implementation of NR1I2 and NR1I3 genetic polymorphism testing in the clinical routine.

Efavirenz decreases etonogestrel exposure: a pharmacokinetic evaluation of implantable contraception with antiretroviral therapy

OBJECTIVES

The primary objective of this study was to characterize the pharmacokinetics of etonogestrel (ENG) released from a contraceptive implant in Ugandan women living with HIV who were receiving efavirenz (EFV) or nevirapine (NVP)-based antiretroviral therapy (ART), compared with ART-naive women over 24 weeks.

DESIGN

Nonrandomized, parallel-group study with three arms: ART-naive, NVP, or EFV-based ART (N = 20/group).

METHODS

Sparse pharmacokinetic sampling of ENG, NVP, or EFV were performed at screening, entry, and then 1, 4, 12, and 24-week postimplant insertion. The primary endpoint was ENG concentrations at week 24, compared between the ART-naive group and each ART group, using geometric mean ratio (GMR) with 90% confidence intervals.

RESULTS

Sixty participants competed the 24-week study and data from 58 participants are included; one participant each was excluded from the NVP group and EFV group because of a sample processing error and ART nonadherence, respectively. At week 24, geometric mean ENG was 362, 341, and 66 pg/ml in the ART-naive, NVP, and EFV groups, respectively [GMR: NVP : ART-naive 0.94 (0.90-1.01); EFV : ART-naive 0.18 (0.17-0.20)]. NVP and EFV concentrations were lower at week 24 compared to preimplant [NVP: geometric mean 5.7 versus 6.8 mg/l, respectively, GMR 0.84 (0.83-0.85); EFV: geometric mean 3.6 versus 4.9 mg/l, respectively, GMR 0.73 (0.69-0.80)].

CONCLUSION

After 24 weeks of combined use, ENG exposure was 82% lower in women using EFV-based ART compared with ART-naive women. In contrast, NVP did not significantly impact ENG exposure. These results raise concerns about reduced effectiveness of implantable contraception for women taking EFV-based ART.