Effect of CYP2B6, ABCB1, and CYP3A5 polymorphisms on efavirenz pharmacokinetics and treatment response: an AIDS Clinical Trials Group study

Integrase Inhibitors are Associated with Neuropsychiatric Symptoms in Women with HIV

OBJECTIVE

Women with HIV(WWH) are more likely to discontinue/change antiretroviral therapy(ART) due to side effects including neuropsychiatric symptoms. Efavirenz and integrase strand transfer inhibitors(INSTIs) are particularly concerning. We focused on these ART agents and neuropsychiatric symptoms in previously developed subgroups of WWH that differed on key sociodemographic factors as well as longitudinal behavioral and clinical profiles. WWH from the Women's Interagency HIV Study were included if they had ART data available, completed the Perceived Stress Scale-10 and PTSD Checklist-Civilian. Questionnaires were completed biannually beginning in 2008 through 2016. To examine ART-symptom associations, constrained continuation ratio model via penalized maximum likelihood were fit within 5 subgroups of WWH. Data from 1882 WWH contributed a total of 4598 observations. 353 women were previously defined as primarily having well-controlled HIV with vascular comorbidities, 463 with legacy effects(CD4 nadir < 250cells/mL), 274 aged ≤ 45 with hepatitis, 453 between 35-55 years, and 339 with poorly-controlled HIV/substance users. INSTIs, but not efavirenz, were associated with symptoms among key subgroups of WWH. Among those with HIV legacy effects, dolutegravir and elvitegravir were associated with greater stress/anxiety and avoidance symptoms(P's < 0.01); dolutegravir was also associated with greater re-experiencing symptoms(P = 0.005). Elvitegravir related to greater re-experiencing and hyperarousal among women with well-controlled HIV with vascular comorbidities(P's < 0.022). Raltegravir was associated with less hyperarousal, but only among women aged ≤ 45 years(P = 0.001). The adverse neuropsychiatric effects of INSTIs do not appear to be consistent across all WWH. Key characteristics (e.g., age, hepatitis positivity) may need consideration to fully weight the risk-benefit ratio of dolutegravir and elvitegravir in WWH.

Genetic and non-genetic factors influencing efavirenz population pharmacokinetics among human immunodeficiency virus-1-infected children in Ethiopia

Despite the potential for efavirenz (EFV) to be an effective alternative antiretroviral agent, its sources of wide inter- and intra-individual pharmacokinetic (PK) variability are not well-characterized in children. We investigated the effects of genetic and non-genetic factors, including demographic, treatment duration, baseline clinical, and biochemical characteristics, on the PKs of EFV through population-PK modeling. Antiretroviral therapy (ART) naïve HIV infected children, 3-16 years (n = 100), were enrolled in Ethiopia and received EFV-based combination ART. EFV concentrations after the first dose and at steady-state collected over a span of 1 year were modeled using population-based methods. A one-compartment model with first-order absorption kinetics described the observed EFV data adequately. The CYP2B6*6 and ABCB1c.4036A>G genotypes were identified as major factors influencing EFV clearance. The typical estimates of oral clearance, volume of distribution, and absorption rate constant for typical 22 kg children with CYP2B6 *1/*1 and ABCB1c.4036G/G genotypes were 4.3 L/h, 124 L, and 0.776/h, respectively. Clearance was reduced by 28% and 72% in CYP2B6*1/*6 and CYP2B6*6/*6 genotypes, respectively. Compared to week 1, clearance was higher from weeks 8 and 12 in CYP2B6*1/*6 and CYP2B6*1/*1 genotypes, respectively. Simulations indicated that EFV 12-h concentrations were comparable across weight bands, but more than 80% of subjects with CYP2B6*6/*6 had EFV concentrations greater than 4 μg/mL. EFV PK variability among children is partly explained by body weight, treatment duration, CYP2B6*6, and ABCB1 rs3842 genotypes. Therefore, in addition to body weight, pediatric dosing of EFV should consider pharmacogenetic variability, duration of therapy, and individual treatment outcomes.

Influence of CYP2B6 and CYP3A4 polymorphisms on the virologic and immunologic responses of patients treated with efavirenz-containing regimen

OBJECTIVES

The main objective of this study was to evaluate the effect of CYP2B6 and CYP3A4 polymorphisms on the virological and immunologic responses of HIV patients. A total of 153 HIV-positive patients were enlisted for the study.

PATIENTS AND METHODS

Viral load and median CD4 T cell counts were evaluated at baseline and month 6 (M6). Samples were identified using TaqMan genotyping assays.

RESULTS

The AG in CYP2B6 rs2279343 was associated with VLS compared to homozygous AA. In the dominant model, the AG/GG genotypes were associated with VLS compared to the AA genotype. Moreover, in overdominant model, the AG genotype was associated with VLS compared to AA/GG. Regarding immunological response, only the AG in SNP rs2279343 CYP2B6 was associated with an increase in CD4 cell count between baseline and M6. In CYP2B6 rs3745274, the CD4 cell count at M6 was higher than that of baseline for GG carriers and for GT carriers. In CYP3A4 rs2740574, the TC carriers showed a higher median CD4 count at M6 compared to that of the baseline count, as well as for CC carriers. The best genotypes combination associated with CD4 cell count improvement were AA/AG in SNP rs2279343 and GG/GT in SNP rs3745274.

CONCLUSION

Our findings support the fact that CYP2B6 rs2279343 could help in the prediction of VLS and both SNPs rs3745274 and rs2279343 in CYP2B6 and CYP3A4 rs2740574 were associated with immune recovery in Malian HIV-positive patients.

The role of CYP2B6 516G>T polymorphism on efavirenz/nevirapine toxicity. Implications on treatment outcomes: Lessons from Botswana

The two non-nucleoside reverse transcriptase inhibitors (NNRTIs), efavirenz (EFV) and nevirapine (NVP), are currently the core antiretroviral drugs for treatment of HIV in sub-Saharan Africa including Botswana. The drugs are metabolized by Cytochrome P450 2B6 (CYP2B6) liver enzyme. The CYP2B6 gene that encodes for metabolism of these drugs is known to be highly polymorphic. One of the polymorphism in the CYP2B6 gene, 516G>T, particularly the 516T allele, is known to confer poor metabolism of EFV and NVP. This may lead to high levels of plasma drug concentrations and development of treatment toxicities, like central nervous system toxicities, and cutaneous and hepatic toxicities, for EFV and NVP, respectively. The CYP2B6 516G allele on the other hand is associated with an extensive metabolism of the two NNRTIs drugs. We sought to establish association between possible developments of NNRTIs toxicities with CYP2B6 516G>T variation in Botswana.A total of 316 peripheral blood mononuclear cells samples were used in a retrospective view. All the samples were from participants on EFV/NVP-containing regimen with known toxicity output. TaqMan Real-Time PCR approach was applied for assessing CYP2B6 516 allele variation in cases with treatment toxicity and those without. Analysis was performed by chi-square statistics and logistic regression analysis.The rate of poor metabolizers among participants with toxicity and those without toxicity was 18.4% and 15.1%, respectively. The CYP2B6 516 genotype distribution comparisons between the participants with toxicity and those without were not statistically different (chi-square = .326; P = .568).CYP2B6 516 variation was not associated with NNRTI toxicity. No other factors were associated with toxicity when considering age, baseline body mass index, baseline CD4, baseline HIV viral load and adherence. The results were discussed in the context of all the studies done in Botswana to date.

Polymorphisms at CYP enzymes, NR1I2 and NR1I3 in association with virologic response to antiretroviral therapy in Brazilian HIV-positive individuals

Virologic failure of antiretroviral therapy (ART) may be explained by single nucleotide polymorphisms (SNPs) in drug absorption and metabolism genes. Here, we characterized the associations between polymorphisms in cytochrome P450 enzymes' genes CYP2B6 and CYP3A4/A5, nuclear receptor genes NR1I2/3, and initial ART efficacy among 203 HIV-positive individuals from Rio de Janeiro. Association between SNPs and virologic control was evaluated after 6 and 12 months of follow-up using Cox regression models. The SNP rs2307424 (NR1I3) was associated with increased virologic response after 12 months of treatment, while rs1523127 (NR1I2), rs3003596, and rs2502815 (NR1I3) were associated with decreased response. Increased virologic response after 12 months (_adjHR = 1.54; p = 0.02) was also observed among carriers of the NR1I3 haplotype rs2502815G-rs3003596A-rs2307424A versus the reference haplotype G-A-G. Our results suggest that NR1I2 and NR1I3 variants are associated with virologic responses to ART among Brazilians.

Association of CYP2B6 Genetic Variation with Efavirenz and Nevirapine Drug Resistance in HIV-1 Patients from Botswana

Purpose

CYP2B6 liver enzyme metabolizes the two non-nucleoside reverse transcriptase inhibitors Efavirenz (EFV) and Nevirapine (NVP) used in the antiretroviral therapy (ART) regimens for HIV-infected individuals. Polymorphisms of the CYP2B6 gene influence drug levels in plasma and possibly virological outcomes. The aim of this study was to explore the potential impact of CYP2B6 genotype and haplotype variation on the risk of developing EFV/NVP drug resistance mutations (DRMs) in HIV-1 patients receiving EFV-/NVP-containing regimens in Botswana.

Patients and Methods

Participants were a sub-sample of a larger study (Tshepo study) conducted in Gaborone, Botswana, among HIV-infected individuals taking EFV/NVP containing ART. Study samples were retrieved and assigned to cases (with DRMs) and controls (without DRMs). Four single-nucleotide polymorphisms (SNPs) in the CYP2B6 gene (−82T>C; 516G>T; 785A>G; 983T>C) were genotyped, the haplotypes reconstructed, and the metabolic score assigned. The possible association between drug resistance and several independent factors (baseline characteristics and CYP2B6 genotypes) was assessed by Binary Logistic Regression (BLR) analysis. EFV/NVP resistance status and CYP2B6 haplotypes were also analyzed using Z-test, chi-square and Fisher’s exact test statistics.

Results

Two hundred and twenty-seven samples were analysed (40 with DRMs, 187 without DRMs). BLR analysis showed an association between EFV/NVP resistance and CYP2B6 516G allele (OR: 2.26; 95% CI: 1.27–4.01; P=0.005). Moreover, haplotype analysis revealed that the proportion of EFV/NVP-resistant infections was higher among CYP2B6 fast than extensive/slow metabolizers (30.8% vs 16.8%; P=0.035), with the 516G allele more represented in the haplotypes of fast than extensive/slow metabolizers (100.0% vs 53.8%; P<0.001).

Conclusion

We demonstrated that the CYP2B6 516G allele, and even more when combined in fast metabolic haplotypes, is associated with the presence of EFV/NVP resistance, strengthening the need to assess the CYP2B6 genetic profiles in HIV-infected patients in order to improve the virologic outcomes of NNRTI containing ART.

Pharmacodynamics of efavirenz 400 mg in treatment-naïve Chinese HIV-infected patients in a prospective cohort study

BACKGROUND

The plasma concentration of patients treated with efavirenz (EFV) 600 mg was found to exceed the upper limit of the proposed therapeutic window in most Chinese HIV-infected individuals; thus, dosage reduction of EFV to 400 mg daily warranted consideration. This study aimed to assess the pharmacodynamics of EFV 400 mg for HIV-1-infected patients in China.

METHOD

Twenty cART-naïve individuals were enrolled in this study. EFV 400 mg combined with tenofovir (TDF) and lamivudine (3TC) as an initial antiretroviral regimen was administered for 48 weeks. EFV concentration and T cell subsets as well as HIV RNA load were evaluated at baseline and at 4, 12, 24, and 48 weeks. Moreover, neuropsychiatric adverse effects were also assessed by the Hamilton depression (HAMD) scale and Pittsburgh sleep quality index (PSQI).

RESULTS

Eighteen males and two females whose median age was 26 (interquartile range [IQR]: 23-32) years completed 48 weeks of follow-up. The median EFV concentrations were 1.88 (IQR: 1.54-2.42), 1.74 (IQR: 1.36-1.93), 1.93 (IQR: 1.66-2.22), and 1.85 (IQR: 1.54-2.14) mg/L at weeks 4, 12, 24, and 48, respectively. The viral load was 4.59 (IQR: 4.10-5.19) log₁₀ copies/mL at baseline, and it decreased by 4.6 (IQR: 3.98-5.18) log₁₀ copies/mL from baseline to week 48. Three of 20 (15%), 10 of 20 (50.0%), 17 of 20 (85%), and 18 of 19 (95%) participants had a plasma viral load less than 50 copies/mL at weeks 4, 12, 24, and 48, respectively. The median CD4 cell count was 330 (IQR: 237-410) cells/μL at baseline, and it increased to 473 (IQR: 344-574) cells/μL at 48 weeks. The HAMD score was 5 (IQR: 3-9.8) and 3 (IQR: 2.25-4) at baseline and 48 weeks, respectively. The PSQI score was 4 (IQR: 2-5.8) and 3 (IQR: 2-4) at baseline and 48 weeks, respectively. Dizziness was the most common event, occurring in 70% of patients within the first 2 weeks of treatment.

CONCLUSION

Patients prescribed with EFV 400 mg-containing agents demonstrated favourable virological and immunological responses. And the plasma EFV concentration was within the recommended therapeutic range, with fewer adverse reactions than with EFV 600 mg. EFV 400 mg was effective and safe in Chinese HIV-infected patients.

TRIAL REGISTRATION

NCT04596488 ; Registered 21 October, 2020; Retrospectively registered.

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.

Pharmacogenomics and pharmacokinetics of efavirenz 400 or 600 mg in 184 treatment-naive HIV-infected patients in China

Background: The pharmacogenomics and pharmacokinetics/pharmacodynamics of 400 mg efavirenz have rarely been reported. Materials & methods: A total of 184 treatment-naive HIV-infected patients were randomly assigned (1:1) to receive a lower dose (tenofovir disoproxil 200 mg, efavirenz 400 mg and lamivudine) or a standard dose regimen. Relationships between pharmacogenomics and efavirenz pharmacokinetics/pharmacodynamics were explored at 48 weeks. Results: There was no relationship between pharmacogenomics and adverse reactions of the central nervous system and antiretoviral efficacy. CYP2B6 516G>T, 785A>G, 18492C>T and ABCB1 3435C>T T/C were associated with higher efavirenz plasma levels in the standard but not the lower dose group. No relationship was found between pharmacogenomics and antiretoviral efficacy. Patients who were <60 kg had higher efavirenz concentration compared with those with weight ≥60 kg when using 600 mg efavirenz, this was not observed with 400 mg efavirenz. Conclusion: The effect of pharmacogenomics and body weight on the efavirenz concentration was significant in the 600 mg group but not in the 400 mg group.

Adverse Drug Reactions Associated with CYP 2B6 Polymorphisms in HIV/AIDS-Treated Patients in Yaoundé, Cameroon

PURPOSE

The metabolism of antiretroviral drugs is subject to individual variations of the CYP 2B6 gene. The objective of this study was to evaluate the prevalence of CYP 2B6 516 G>T and 983 T>C polymorphisms and investigate their association with the development of adverse drug reactions (ADRs) in people living with HIV/AIDS in Cameroon.

PATIENTS AND METHODS

A total number of 122 patients, attending the Yaoundé Central Hospital HIV Day Clinic, consented to take part in this study. Blood specimens were collected and DNA was extracted using the Chelex method. Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) was performed for the detection of CYP 2B6 Single-Nucleotide Polymorphisms (SNPs). Genotype frequencies were compared between groups with or without ADRs. Logistic regression analysis was performed to assess association between genotype and adverse effects of antiretroviral therapy (ART).

RESULTS

Three types of metabolizers were identified: extensive, intermediate and slow. For the 516G>T polymorphism, prevalences of 8.2% GG, 65.6% GT and 26.2% TT were obtained. For the 983T>C polymorphism, 89.3% TT, 4.1% CT and 6.6% CC prevalences were obtained. Those homozygous for the wild-type allele (516GG) were less likely to develop ADR with a statistically significant difference (OR=0.885, P=0.029). For the CYP2B6 T983C SNP, homozygous mutants (CC) may present a higher risk (threefold) of developing adverse reactions (OR=2.677, P=0.164).

CONCLUSION

These findings demonstrate that ADRs among HIV/AIDS patients under ART may be associated with the genetic variability of the metabolizing enzyme CYP 2B6. Genotyping for this gene may guide the better administration of Efavirenz and Nevirapine to Cameroonian patients.

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.

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.

Impact of Efavirenz Metabolism on Loss to Care in Older HIV+ Africans

BACKGROUND AND OBJECTIVE: Efavirenz is commonly used in Africa and is frequently associated with neurocognitive toxicity, which may compromise clinical outcomes. Older individuals are at increased risk for drug toxicity and clinical outcomes may be worse in older age, particularly among those individuals with cytochrome P450 (CYP) 2B6 polymorphisms associated with slower efavirenz metabolism. The aim of this study was to determine if the CYP2B6 polymorphisms differentially impacts loss to care in older people.

METHODS

We conducted a prospective cohort study of 914 treatment-naïve HIV+ adults initiating efavirenz-based antiretroviral treatment at public HIV clinics in Gaborone, Botswana between 2009 and 2013. Older age, defined as age ≥ 50 years, was the primary exposure and loss to care at 6 months was the primary outcome. Interaction between age and CYP2B6 516G>T and 983T>C polymorphisms, defined as extensive, intermediate, and slow metabolism, was assessed. Neurocognitive toxicity was measured using a symptom questionnaire. Age-stratified logistic regression was performed to identify factors associated with loss to care.

RESULTS

Older age was associated with loss to care (OR 1.95, 95% CI 1.30-2.92). Age modified the effect of CYP2B6 genotype on loss to care with older, slow metabolizers at over four-fold higher risk when compared to older, intermediate metabolizers (OR 4.06 95% CI 1.38-11.89); neurocognitive toxicity did not mediate this risk. CYP2B6 metabolism genotype did not increase risk of loss to care in younger participants.

CONCLUSION

Older age was associated with loss to care, especially among those with slow efavirenz metabolism. Understanding the relationship between older age and CYP2B6 genotype will be important to improving outcomes in an aging population initiating efavirenz-based ART in similar settings.

Occurrence of CYP2B6 516G>T polymorphism in patients with ARV-associated hepatotoxicity

Background

Hepatic enzyme cytochrome P450 2B6 (CYP2B6) plays a role in the metabolism of efavirenz drugs. CYP2B6 516G>T variation showed an implication for HIV treatment.

Methods

CYP2B6 516G>T polymorphism was genotyped in a total 165 HIV patients that include 34 with and 131 without hepatotoxicity and 155 healthy individuals by the PCR‐RFLP.

Results

In patients with hepatotoxicity, the prevalence of CYP2B6 516TT genotype was higher as compared to healthy individuals (35.3% vs. 30.5%, OR = 1.74). Patients with hepatotoxicity using tobacco had a higher prevalence of genotypes CYP2B6 516GT, 516TT, 516GT+TT as compared to healthy individuals (28.57% vs. 25.93%; 57.14% vs. 29.63%; 85.71% vs. 55.56%). Likewise, hepatotoxicity in patients consuming alcohol showed higher distributions of CYP2B6 516GT, 516TT, 516GT+TT genotypes (57% vs. 25.93%; 42.86% vs. 33.33%; 71.43% vs. 59.26%). Nevirapine users with hepatotoxicity overrepresented genotypes CYP2B6 TT and 516GT+TT as compared to efavirenz users (47.83% vs. 45.45%, OR = 6.88, 65.22% vs. 54.55%, OR = 1.56). Similarly, in nevirapine +alcohol users with hepatotoxicity, the frequency of CYP2B6 516GT, 516GT+TT genotypes was higher than with nevirapine +alcohol nonusers (40.0% vs. 11.11%, OR = 8.00, 80.0% vs. 27.78%, OR = 4.00). In HIV patients, nevirapine users had higher frequency of CYP2B6 516GT, 516GT+TT genotypes as compared to efavirenz users (42.02% vs. 25.00%, OR = 2.53; 72.27% vs. 58.33%, OR = 1.86). Likewise, in HIV patients, genotypes CYP2B6 516GT, 516GT+TT were predominant with nevirapine +alcohol users as compared to nevirapine +alcohol nonusers (57.89% vs. 34.57%, OR = 2.46; 78.95% vs. 69.14%, OR = 1.67). In multivariate logistic regression, taking nevirapine had a protection for severity of ARV‐associated hepatotoxicity (OR = 0.23, p = 0.005).

Conclusions

No significant association was detected between CYP2B6 516G>T polymorphism and susceptibility to ARV‐associated hepatotoxicity.

Population pharmacokinetics and dosing regimen optimisation of lopinavir in Chinese adults infected with HIV

Lopinavir (LPV) is a protease inhibitor (PI) for the treatment of human immunodeficiency virus (HIV) infections. Current studies on LPV are mainly focused on Caucasians, and none have investigated the population pharmacokinetics (PPK) of LPV in Chinese population. The present study aimed to develop a PPK model for oral LPV in Chinese adults who are HIV-infected. A total of 460 LPV concentrations from 174 Chinese patients who received LPV/ritonavir (LPV/r) 400/100 mg orally every 12 hours (q12h) were analysed using the non-linear mixed-effects modelling approach. Simulations of the LPV concentration profile were performed with different dosing regimens. A one-compartment model with first-order absorption and elimination process described the data. The estimated apparent clearance (CL/F) and volume of distribution (V/F) (% relative standard error [RSE]) for oral LPV were 5.9 L/h (3%) and 117 L (8%), respectively. Body-weight was identified as a covariate on CL/F. In patients who weighed between 45 and 115 kg and received the standard 400/100 mg q12h regimen, the probability of achieving target trough concentration (C_trough ) of 1 mg/L was >98% for PI-naïve patients and the probability of achieving target C_trough of 4 mg/L was <80% for PI-pretreated patients. This is the first population pharmacokinetic study to characterise the PK of LPV in Chinese patients with HIV infection. There were no obvious ethnic differences in the PK of LPV between the Chinese population and Caucasian population. The simulations demonstrated that the standard dosing regimen of 400/100 mg q12h (LPV/r tablets) appears to be sufficient for PI-naïve patients but suboptimal for PI-pretreated patients. Therefore, the regimen of 800/200 mg q12h was recommended for PI-pretreated patients. Further investigation of dosage recommendation could be helpful in optimising LPV therapy for HIV infections.

CYP2B6 Genetic Polymorphisms, Depression, and Viral Suppression in Adults Living with HIV Initiating Efavirenz-Containing Antiretroviral Therapy Regimens in Uganda: Pooled Analysis of Two Prospective Studies

Single-nucleotide polymorphisms (SNPs) in CYP2B6 have been shown to predict variation in plasma efavirenz concentrations, but associations between these SNPs and efavirenz-mediated depression and viral suppression are less well described. We evaluated three SNPs in CYP2B6 (rs3745274, rs28399499, and rs4803419) in Ugandan persons living with HIV. To define exposure, we used previously published pharmacokinetic modeling data to categorize participants as normal, intermediate, and poor efavirenz metabolizers. Our outcomes were probable depression in the first 2 years after antiretroviral therapy (ART) initiation (mean score of >1.75 on the Hopkins Symptom Depression Checklist) and viral suppression 6 months after ART initiation. We fit generalized estimating equation and modified Poisson regression models adjusted for demographic, clinical, and psychosocial characteristics with or without individuals with depression at the time of ART initiation. Among 242 participants, there were no differences in the pre-ART depression or viral load by efavirenz metabolism strata (p > .05). Participants were classified as normal (32%), intermediate (50%), and poor (18%) metabolizers. Seven percent (56/242) of follow-up visits met criteria for depression. Eighty-five percent (167/202) of participants who completed a 6-month visit achieved viral suppression. CYP2B6 metabolizer strata did not have a statistically significant association with either depression [adjusted risk ratio (aRR) comparing intermediate or poor vs. normal, 1.46; 95% confidence interval (CI), 0.72-2.95] or 6-month viral suppression (aRR, 1.01; 95% CI, 0.88-1.15). However, in analyses restricted to participants without pre-ART depression, poorer CYP2B6 metabolism was associated with increased odds of depression (adjusted odds ratio, 4.11; 95% CI, 1.04-16.20). Efavirenz-metabolizing allele patterns are strongly associated with risk of incident depression. Future work should elucidate further region-specific gene-environment interactions and whether alternate polymorphisms may be associated with efavirenz metabolism.

Drug metabolism and transport gene polymorphisms and efavirenz adverse effects in Brazilian HIV-positive individuals

Objectives

There are limited data regarding efavirenz pharmacogenetics in admixed populations. The Brazilian population is highly admixed. In a Brazilian cohort, we sought to characterize associations between efavirenz adverse effects (all-cause and CNS) and polymorphisms in seven genes known or suspected to affect efavirenz metabolism and transport.

Methods

We studied 225 HIV-positive individuals who had been prescribed efavirenz-containing regimens at a hospital in Rio de Janeiro, Brazil. Eighty-nine cases had efavirenz adverse effects, including 43 with CNS adverse effects, while 136 controls had no adverse effect of any antiretroviral after treatment for at least 6 months. A total of 67 candidate polymorphisms in ABCB1, CYP2A6, CYP2B6, CYP3A4, CYP3A5, NR1I2 and NR1I3 genes were selected for association analysis. Admixture was assessed using 28 ancestry-informative polymorphisms previously validated for the Brazilian population. Associations were evaluated with logistic regression models adjusted for sex and genetic ancestry.

Results

There was extensive African, European and Native American admixture in the cohort. Increased all-cause adverse effects were associated with the CYP2B6 genotype combination 15582CC-516TT-983TT (OR = 7.26, P = 0.003) and with the CYP2B6 slow metabolizer group 516TT or 516GT-983CT (OR = 3.10, P = 0.04). CNS adverse effects were nominally associated with CYP3A4 rs4646437 (OR = 4.63, P = 0.014), but not after adjusting for multiple comparisons.

Conclusions

In a highly admixed Brazilian cohort, the CYP2B6 slow metabolizer genotype was associated with an increased risk of efavirenz adverse effects.

Depression and Suicidal Ideation Among HIV-Infected Adults Receiving Efavirenz Versus Nevirapine in Uganda: A Prospective Cohort Study

BACKGROUND

Evidence regarding potential adverse neuropsychiatric effects of efavirenz is conflicting, and data from sub-Saharan Africa, where 70% of persons living with HIV (PLHIV) reside and efavirenz is used as first-line therapy, are limited.

OBJECTIVE

To estimate associations between efavirenz use and depression and suicidal ideation among PLHIV in Uganda.

DESIGN

Prospective observational cohort study. (ClinicalTrials.gov: NCT01596322).

SETTING

Mbarara, Uganda.

PARTICIPANTS

Adult PLHIV enrolled at the start of antiretroviral therapy (ART) and observed every 3 to 4 months from 2005 to 2015.

MEASUREMENTS

The exposure of interest was time-varying efavirenz use, defined as use during the 7 days and in 60 or more of the 90 days before a study visit, compared with nevirapine use. Self-reported outcomes were depression, defined as a mean score greater than 1.75 on the Hopkins Symptom Checklist depression subscale, and suicidal ideation. Multivariable-adjusted generalized estimating equations (GEE) logistic regression, Cox proportional hazards regression, and marginal structural models were fit to estimate the association between efavirenz use and the risk for depression and suicidal ideation.

RESULTS

694 participants (median age, 33 years; median pretreatment CD4+ count, 1.8 × 109 cells/L) contributed 1200 person-years of observation (460 person-years receiving efavirenz). No baseline differences in depression or suicidal ideation were found between patients ever exposed to efavirenz and those never exposed to efavirenz and receiving nevirapine (P > 0.80 for both). Of 305 participants ever-exposed to efavirenz, 61 (20.0%) and 19 (6.2%) had depression and suicidal ideation, respectively, on at least 1 follow-up visit, compared with 125 (32.1%) and 47 (12.1%) of the 389 who received nevirapine. In adjusted GEE models, efavirenz use was associated with decreased odds of depression compared with nevirapine use (adjusted odds ratio, 0.62 [95% CI, 0.40 to 0.96]) and was not significantly associated with suicidal ideation (adjusted odds ratio, 0.61 [CI, 0.30 to 1.25]). Time-to-event and marginal structural models yielded similar estimates.

LIMITATION

Nonrandom assignment to treatment and substantial differences between the efavirenz and nevirapine groups.

CONCLUSION

No evidence was found that use of efavirenz in first-line ART increased the risk for depression or suicidal ideation compared with nevirapine use among PLHIV in Uganda.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Brain neurotransmitter transporter/receptor genomics and efavirenz central nervous system adverse events

OBJECTIVE

We characterized associations between central nervous system (CNS) adverse events and brain neurotransmitter transporter/receptor genomics among participants randomized to efavirenz-containing regimens in AIDS Clinical Trials Group studies in the USA.

PARTICIPANTS AND METHODS

Four clinical trials randomly assigned treatment-naive participants to efavirenz-containing regimens. Genome-wide genotype and PrediXcan were used to infer gene expression levels in tissues including 10 brain regions. Multivariable regression models stratified by race/ethnicity were adjusted for CYP2B6/CYP2A6 genotypes that predict plasma efavirenz exposure, age, and sex. Combined analyses also adjusted for genetic ancestry.

RESULTS

Analyses included 167 cases with grade 2 or greater efavirenz-consistent CNS adverse events within 48 weeks of study entry, and 653 efavirenz-tolerant controls. CYP2B6/CYP2A6 genotype level was independently associated with CNS adverse events (odds ratio: 1.07; P=0.044). Predicted expression of six genes postulated to mediate efavirenz CNS side effects (SLC6A2, SLC6A3, PGR, HTR2A, HTR2B, HTR6) were not associated with CNS adverse events after correcting for multiple testing, the lowest P value being for PGR in hippocampus (P=0.012), nor were polymorphisms in these genes or AR and HTR2C, the lowest P value being for rs12393326 in HTR2C (P=6.7×10(-4)). As a positive control, baseline plasma bilirubin concentration was associated with predicted liver UGT1A1 expression level (P=1.9×10(-27)).

CONCLUSION

Efavirenz-related CNS adverse events were not associated with predicted neurotransmitter transporter/receptor gene expression levels in brain or with polymorphisms in these genes. Variable susceptibility to efavirenz-related CNS adverse events may not be explained by brain neurotransmitter transporter/receptor genomics.

Polymorphisms in cytochrome P450 are associated with extensive efavirenz pharmacokinetics and CNS toxicities in an HIV cohort in Botswana

Inter-individual variability in efavirenz (EFV) pharmacokinetics and dynamics are dominantly driven by the polymorphism in cytochrome P450 (CYP) isoenzyme 2B6 516G>T. We hypothesized that additional CYP polymorphisms mediate the relationship between CYP2B6 516G>T, EFV metabolism, and clinical events. We investigated 21 SNPs in 814 HIV-infected adults initiating EFV-based therapy in Botswana for population pharmacokinetics, CNS toxicities, and treatment outcomes. Two SNPs (rs28399499 and rs28399433) showed reduced apparent oral EFV clearance. Four SNPs (rs2279345, rs4803417, rs4802101, and rs61663607) showed extensive clearance. Composite CYP2B-mediated EFV metabolism was significantly associated with CNS toxicity (p=0.04), with extensive metabolizers reporting more and slow and very slow metabolizers reporting less toxicity after one month compared to intermediate metabolizers. Composite CYP2B6 metabolism was not associated with composite early treatment failure. In conclusion, our data suggest that CNS-related toxicities might not be solely the result of super-therapeutic parent EFV concentrations in HIV-infected individuals in patients of African ancestry.

Pharmacogenetic associations with cytochrome P450 in antiretroviral therapy: what does the future hold?

INTRODUCTION

Several antiretroviral drugs used to treat infection with the human immunodeficiency virus (HIV) are substrates of enzymes belonging to the cytochrome P450 (CYP) superfamily, which are polymorphically expressed. It may therefore be useful to take into account the genetic variation in these enzymes to predict the likelihood of anti-HIV treatment success, toxicity and the potential for drug-drug interactions. Areas covered: In this manuscript, the authors discuss the current state of knowledge regarding pharmacogenetic associations between CYP and all major antiretrovirals, as well as the importance of these associations. Expert opinion: While many pharmacogenetic associations for CYP have been described in the literature, replication studies are sometimes lacking. The implementation of this knowledge in clinical practice also remains difficult. Further efforts are required both to expand this field of knowledge and to enable its use in everyday clinical practice.

Precision medicine for HIV: where are we?

To date, antiretroviral therapy is highly effective in HIV-affected patients, but the individualization of such a life-long therapy may be advised. This review briefly summarizes the main factors involved in the potential personalization of antiretroviral treatment. Relevant articles in English were identified by PubMed and recent congresses’ abstracts. Foremost influences concerning pharmacodynamics, therapeutic drug monitoring, pharmacogenetics, comorbidities, immune recovery and viral characteristics affecting the healthcare of HIV-positive patients are listed here. Furthermore, pharmacoeconomic aspects are mentioned. Applying pharmacokinetic and pharmacogenetic knowledge may be informative and guide the better choice of treatment in order to achieve long-term efficacy and avoid adverse events. Randomized investigations of the clinical relevance of tailored antiretroviral regimens are needed in order to obtain a better management of HIV/AIDS-affected patients.

Race/ethnicity difference in the pharmacogenetics of bilirubin-related atazanavir discontinuation

BACKGROUND

Atazanavir causes plasma indirect bilirubin to increase. We evaluated associations between Gilbert's polymorphism and bilirubin-related atazanavir discontinuation stratified by race/ethnicity.

PATIENTS AND METHODS

Patients had initiated atazanavir/ritonavir-containing regimens at an HIV primary care clinic in the southeastern USA, and had at least 12 months of follow-up data. Metabolizer group was defined by UGT1A1 rs887829 C→T. Genome-wide genotype data were used to adjust for genetic ancestry in combined population analyses.

RESULTS

Among 321 evaluable patients, 15 (4.6%) had bilirubin-related atazanavir discontinuation within 12 months. Homozygosity for rs887829 T/T was present in 28.1% of Black, 21.4% of Hispanic, and 8.6% of White patients. Among all patients the hazard ratio (HR) for bilirubin-related discontinuation with T/T versus C/C genotype was 7.3 [95% confidence interval (CI): 1.7-31.5; P=0.007]. Among 152 White patients the HR was 14.4 (95% CI: 2.6-78.7; P=0.002), but among 153 Black patients the HR was 0.8 (95% CI: 0.05-12.7; P=0.87).

CONCLUSION

Among patients who initiated atazanavir/ritonavir-containing regimens, UGT1A1 slow metabolizer genotype rs887829 T/T was associated with increased bilirubin-related discontinuation of atazanavir in White but not in Black patients, this despite T/T genotype being more frequent in Black patients.

Genetic Polymorphisms Affecting the Pharmacokinetics of Antiretroviral Drugs

BACKGROUND

Antiretroviral treatment is highly effective in enhancing HIV-positive patients' survival and quality of life. Despite an increased tolerability in recent years, a substantial amount of patients experience side effects. Antiretrovirals' efficacy and tolerability have been associated with plasma concentrations and single nucleotide polymorphisms in selected genes involved in drug disposition.

OBJECTIVE

Our aim was to review the current knowledge in genetic polymorphisms affecting plasma, intracellular or compartmental concentrations of antiretrovirals.

METHODS

A search of the PubMed database was conducted to identify relevant articles, using the following terms: 'pharmacogenetics' or 'pharmacogenomics' or 'single nucleotide polymorphisms' or 'genetic/allelic variants' and 'pharmacokinetics' or 'concentrations' and 'HIV' or 'antiretroviral'. Abstracts from the main HIV conferences during 2015 and 2016 were also searched using the same keywords. Abstracts were manually checked and, if relevant, full papers were obtained. Only articles published in English were selected.

RESULTS

Several genetic polymorphisms in genes coding enzymes involved in drug metabolism (cytochrome P450 isoenzymes and uridine diphosphate glucuronosyltransferases) and transport (P-glycoprotein, anionic and cationic transporters, other transporters), as well as nuclear receptors (pregnane X receptor and the constitutive androstane receptor), have been associated with concentrations of antiretrovirals. The extent of such influence, the conflicting data, and the potential clinical relevance are discussed in the main section of this article.

CONCLUSION

Genetic polymorphisms may affect antiretroviral disposition, as well as both efficacy and toxicity. Despite a large amount of data, such precious knowledge has seldom been applied in patients. Studies on the clinical relevance and cost effectiveness of tailoring antiretroviral regimens to patients' genetic assets are lacking, but their importance may grow with the increasing age and complexity of persons living with HIV/AIDS.

Brief Report: CYP2B6 516G>T Minor Allele Protective of Late Virologic Failure in Efavirenz-Treated HIV-Infected Patients in Botswana

BACKGROUND

CYP2B6 polymorphisms that affect efavirenz (EFV) concentrations are common, but the effect of this polymorphism on HIV virologic failure in clinical practice settings has not fully been elucidated. Our objective was to investigate the relationship between the CYP2B6 516G>T genotype and late virologic failure in patients treated with EFV in Gaborone, Botswana.

SETTING

We performed a case-control study that included 1338 HIV-infected black Batswana on EFV-based antiretroviral therapy (ART). Patients were approached for enrollment during regular visits at one of the outpatient HIV clinics between July 2013 and April 2014.

METHODS

Cases experienced late HIV failure, defined as plasma HIV RNA >1000 copies/mL after maintaining viral suppression (<400 copies/mL) for at least 6 months. For each case, a total of 4 control patients were randomly sampled from the same population. Controls had plasma HIV RNA <400 copies/mL on ART for at least 6 months. Logistic regression was used to determine the adjusted odds of late HIV failure by 516G>T genotype.

RESULTS

After adjustment for the confounding variables age and CD4 count, the CYP2B6 516 T-allele was protective against late HIV virologic breakthrough, adjusted OR 0.70; 95% CI: 0.50 to 0.97.

CONCLUSION

The CYP2B6 516 T-allele was protective against late virologic breakthrough in patients with initial (6 month) HIV RNA suppression on EFV-based ART. Future studies are needed to assess long-term viral benefits of identifying and offering EFV containing ART to black African HIV-infected patients with CYP2B6 T-alleles, especially given the wider availability of a single pill EFV in this setting.

Antiretroviral dose optimization: the future of efavirenz 400 mg dosing

PURPOSE OF REVIEW

Antiretroviral (ARV) therapy costs in low-income and middle-income countries are major concerns, and lower doses of first-line treatment components, when possible, would save millions of dollars, which could be used to treat more people living with HIV.

RECENT FINDINGS

The Encore-1 study, followed by a detailed pharmacokinetic analysis of efavirenz 400 versus 600 mg once daily, produced enough information for the most recent ARV treatment WHO guidelines to include efavirenz 400 mg among agents used for first-line treatment. However, data on efavirenz 400 mg plasma concentrations during pregnancy and when coadministered with rifampicin-containing antituberculosis (TB) treatment are not yet available as formal pharmacokinetic studies under these circumstances are ongoing.

SUMMARY

Although efavirenz at a daily dose of 400 mg once daily in combination with tenofovir disoproxil fumarate and emtricitabine has shown noninferiority to the approved 600 mg once-daily dose, large global uptake has been delayed by the lack of data on drug exposure during pregnancy and anti-TB treatment. Knowledge on efavirenz 400 mg exposure in these scenarios will arise in mid-late 2017.

Multiphenotype association study of patients randomized to initiate antiretroviral regimens in AIDS Clinical Trials Group protocol A5202

Supplemental Digital Content is available in the text.

Background

High-throughput approaches are increasingly being used to identify genetic associations across multiple phenotypes simultaneously. Here, we describe a pilot analysis that considered multiple on-treatment laboratory phenotypes from antiretroviral therapy-naive patients who were randomized to initiate antiretroviral regimens in a prospective clinical trial, AIDS Clinical Trials Group protocol A5202.

Participants and methods

From among 5 9545 294 polymorphisms imputed genome-wide, we analyzed 2544, including 2124 annotated in the PharmGKB, and 420 previously associated with traits in the GWAS Catalog. We derived 774 phenotypes on the basis of context from six variables: plasma atazanavir (ATV) pharmacokinetics, plasma efavirenz (EFV) pharmacokinetics, change in the CD4+ T-cell count, HIV-1 RNA suppression, fasting low-density lipoprotein-cholesterol, and fasting triglycerides. Permutation testing assessed the likelihood of associations being by chance alone. Pleiotropy was assessed for polymorphisms with the lowest P-values.

Results

This analysis included 1181 patients. At P less than 1.5×10⁻⁴, most associations were not by chance alone. Polymorphisms with the lowest P-values for EFV pharmacokinetics (CYPB26 rs3745274), low-density lipoprotein -cholesterol (APOE rs7412), and triglyceride (APOA5 rs651821) phenotypes had been associated previously with those traits in previous studies. The association between triglycerides and rs651821 was present with ATV-containing regimens, but not with EFV-containing regimens. Polymorphisms with the lowest P-values for ATV pharmacokinetics, CD4 T-cell count, and HIV-1 RNA phenotypes had not been reported previously to be associated with that trait.

Conclusion

Using data from a prospective HIV clinical trial, we identified expected genetic associations, potentially novel associations, and at least one context-dependent association. This study supports high-throughput strategies that simultaneously explore multiple phenotypes from clinical trials’ datasets for genetic associations.

CYP2B6 genotypes and early efavirenz-based HIV treatment outcomes in Botswana

OBJECTIVES

To determine the association between cytochrome p450 2B6 genotypes and efavirenz-based HIV treatment outcomes.

DESIGN

Observational cohort study of HIV-infected adults initiating efavirenz-based regimens in Botswana.

METHODS

The primary endpoint was a composite of death or loss to care or HIV RNA more than 25 copies/ml at 6 months. CYP2B6 516G>T and 983T>C genotyping was done with Taqman Open Array platform. Adverse experiences were measured by using the Subject Experience Questionnaire. Metabolism alleles were included in logistic regression models of the composite endpoint.

RESULTS

A total of 801 individuals included 406 (51%) men, median age 37 years, median baseline CD4 cell count 195 cells/μl, and plasma HIV RNA 4.9 log10 copies/ml. 288 (36%) reached the endpoint, including 34 (4%) deaths, 151 (19%) lost to care, 11 (1%) lost to the study, but alive and in care, and 92 (11%) with plasma HIV RNA more than 25 copies/ml. Metabolism variant alleles were common with 396 (49%) intermediate and 192 (24%) slow metabolizers. There were no statistically significant associations between metabolism and treatment endpoints. However, slower metabolism was associated with fewer adverse experiences.

CONCLUSION

Slow metabolism alleles were associated with lower efavirenz clearance but not any of the treatment endpoints. Slow efavirenz metabolism did not exacerbate central nervous system toxicity. These results should allay concern that slow efavirenz metabolism adversely impacts individuals in sub-Saharan African settings in which these alleles are common.

Genetic variants in CYP2B6 and CYP2A6 explain interindividual variation in efavirenz plasma concentrations of HIV-infected children with diverse ethnic origin

Background

Approximately 2.6 million children live with HIV globally, and efavirenz (EFV) is one of the most widely used antiretroviral agents for HIV treatment in children and adults. There are concerns about the appropriateness of current EFV dosing and it has been discussed whether EFV dosing should be adapted according to genotype in children as suggested for adults.

Aim

To investigate if pediatric EFV dosing should be guided by genetic variation in drug metabolizing enzymes rather than by body weight.

Method

EFV plasma concentrations measured for clinical purposes from all children less than 18 years old at Karolinska University Hospital, Stockholm, Sweden, treated with EFV were collected retrospectively. They were genotyped for eleven polymorphisms in genes coding for drug-metabolizing enzymes and P-glycoprotein, of potential importance for EFV disposition. Data on country of origin, sex, age, weight, HIV RNA, viral resistance patterns, CD4 cells, adherence to treatment, subjective health status and adverse events were collected from their medical records.

Results

Thirty-six patients and 182 (mean 5 samples/patient) EFV plasma concentration measurements from children of African, Asian and Latin American origin were included. EFV plasma concentration varied 21-fold between measurements (n = 182) (0.85–19.3 mg/L) and 9-fold measured as mean EFV plasma concentration across the subjects (1.55–13.4 mg/L). A multivariate mixed-effects restricted maximum likelihood regression model, including multiple gene polymorphisms, identified CYP2B6*6 T/T (p < 0.0005), CYP2B6*11 G/G (p < 0.0005), CYP2A6*9 A/C (p = 0.001) genotypes, age at treatment initiation (p = 0.002) and time from treatment initiation (p < 0.0005) as independent factors significantly related to log_e concentration/(dose/weight). The contribution of the model to the intra- and interindividual variation were 6 and 75%, respectively (Bryk/Raudenbush R-squared level).

Conclusion

Genetic polymorphisms in CYP2B6 and CYP2A6 explained a significant proportion of variability in EFV plasma concentration in HIV-infected children in a multi-ethnic outpatient clinic. Knowledge about individual variants in key drug metabolizing enzyme genes could improve clinical safety and genotype directed dosing could achieve more predictable EFV plasma concentrations in HIV-infected children.

Impact of Single Nucleotide Polymorphisms on Plasma Concentrations of Efavirenz and Lopinavir/Ritonavir in Chinese Children Infected with the Human Immunodeficiency Virus

Single nucleotide polymorphisms (SNPs) in the genes that encode the cytochrome P450 (CYP) drug metabolizing enzymes and drug transporters have been reported to influence antiretroviral drug pharmacokinetics. Although primarily metabolized by CYP2B6 and -3A, efavirenz (EFV) and lopinavir/ritonavir (LPV/r) are substrates of P-glycoprotein and the solute carrier organic (SLCO) anion transporter, respectively. We investigated the association between SNPs and efavirenz (EFV) or lopinavir/ritonavir (LPV/r) concentrations in Chinese children infected with the human immunodeficiency virus (HIV). Genotyping was performed on CYP2B6 516G→T, -1459C→T, and -983T→C, ABCB1 3435C→T, and SLCO1B1 521T→C in 229 HIV-infected Chinese pediatric patients (age range 4.0 to 17.5 yrs). Plasma concentrations of EFV and LPV/r were measured using validated high-performance liquid chromatography coupled with the mass spectrum method among 39 and 69 children who received EFV- and LPV/r-containing regimens, respectively. The frequencies of CYP2B6 516G→T in the study participants were 71%, 25%, and 4% for the G/G, G/T, and T/T genotypes, respectively. Among the children under therapeutic drug monitoring, 21% and 39% experienced EFV and LPV concentrations, respectively, above the upper threshold of the therapeutic window. CYP2B6 516G→T was significantly associated with EFV concentrations (p<0.001). Older children (older than 10 yrs) were more likely to have significantly higher EFV concentrations than the younger ones (p=0.0314). CYP2B6 genotyping and EFV concentration monitoring may help optimize antiretroviral therapy in pediatric patients who initiate an EFV-based regimen.

Race/Ethnicity and the Pharmacogenetics of Reported Suicidality With Efavirenz Among Clinical Trials Participants

Background

We examined associations between suicidality and genotypes that predict plasma efavirenz exposure among AIDS Clinical Trials Group study participants in the United States.

Methods

Four clinical trials randomly assigned treatment-naive participants to efavirenz-containing regimens; suicidality was defined as reported suicidal ideation or attempted or completed suicide. Genotypes that predict plasma efavirenz exposure were defined by CYP2B6 and CYP2A6 polymorphisms. Associations were evaluated with weighted Cox proportional hazards models stratified by race/ethnicity. Additional analyses adjusted for genetic ancestry and selected covariates.

Results

Among 1833 participants, suicidality was documented in 41 in exposed analyses, and 34 in on-treatment analyses. In unadjusted analyses based on 12 genotype levels, suicidality increased per level in exposed (hazard ratio, 1.11; 95% confidence interval, .96-1.27) and on-treatment 1.16; 1.01-1.34) analyses. In the on-treatment analysis, the association was strongest among white but nearly null among black participants. Considering 3 metabolizer levels (extensive, intermediate and slow), slow metabolizers were at increased risk. Results were similar after baseline covariate-adjustment for genetic ancestry, sex, age, weight, injection drug use history, and psychiatric history or recent psychoactive medication.

Conclusions

Genotypes that predict higher plasma efavirenz exposure were associated with increased risk of suicidality. Strength of association varied by race/ethnicity.

Pharmacogenetics of efavirenz discontinuation for reported central nervous system symptoms appears to differ by race

BACKGROUND

Efavirenz frequently causes central nervous system (CNS) symptoms. We evaluated genetic associations with efavirenz discontinuation for CNS symptoms within 12 months of treatment initiation.

METHODS

Patients had initiated efavirenz-containing regimens at an HIV primary care clinic in the Southeastern United States and had at least 12 months of follow-up data. Polymorphisms in CYP2B6 and CYP2A6 defined efavirenz metabolizer categories. Genome-wide genotyping enabled adjustment for population stratification.

RESULTS

Among 563 evaluable patients, 99 (17.5%) discontinued efavirenz within 12 months, 29 (5.1%) for CNS symptoms. The hazard ratio (HR) for efavirenz discontinuation for CNS symptoms in slow versus extensive metabolizers was 4.9 [95% confidence interval (CI): 1.9-12.4; P=0.001]. This HR in Whites was 6.5 (95% CI: 2.3-18.8; P=0.001) and 2.6 in Blacks (95% CI: 0.5-14.1; P=0.27). Considering only slow metabolizers, the HR in Whites versus Blacks was 3.1 (95% CI: 0.9-11.0; P=0.081). The positive predictive value of slow metabolizer genotypes for efavirenz discontinuation was 27% in Whites and 11% in Blacks.

CONCLUSION

Slow metabolizer genotypes were associated significantly with efavirenz discontinuation for reported CNS symptoms. This association was considerably stronger in Whites than in Blacks.

Cytochrome 2B6 polymorphism and efavirenz-induced central nervous system symptoms : a substudy of the ANRS ALIZE trial

OBJECTIVES

Single nucleotide polymorphisms in the cytochrome P450 (CYP) 2B6 gene have been associated with high interindividual variation in efavirenz pharmacokinetics. However, clinical data on the relationship of CYP2B6 polymorphisms with the occurrence of efavirenz-induced central nervous system (CNS) symptoms are limited.

METHODS

We analysed four polymorphisms in the CYP2B6 (516 G>T), CYP3A5 (6986 A>G) and ATP-binding cassette, sub-family B, member 1 (ABCB1) (2677 G>T/A and 3435 C>T) genes in HIV-infected adults virologically suppressed on a protease inhibitor-based regimen who switched to a regimen containing emtricitabine, didanosine and efavirenz in the setting of the ANRS ALIZE trial. Kaplan-Meier methods and Cox regression analysis were used to investigate their association with efavirenz plasma levels and CNS events up to 48 months after switching.

RESULTS

In total, 191 patients with a median age of 41 years, who were 87% male and 85% Caucasian, were enrolled in the study. Variant allelic frequencies were 0.49, 0.93, 0.59 and 0.63 for CYP2B6 516, CYP3A5 392, ABCB1 2677 and ABCB1 3435, respectively. The median efavirenz plasma concentration (MEPC) was 2.2 mg/L [interquartile range (IQR) 1.7-2.8 mg/L] and was significantly higher in patients with the deficient CYP2B6 516T. Overall, 242 CNS events were reported in 104 individuals (54%). No correlation was found between MEPC and CNS events. The occurrence of a first CNS event was lower in patients with the CYP2B6 516 G/G genotype vs. CYP2B6 516 T genotypes [50% (IQR: 40-60%) vs. 66% (IQR: 56-75%), respectively; P = 0.02]. In an adjusted Cox regression model, there was a tendency towards a higher risk of a first CNS event among carriers of the variant CYP2B6 516 T allele (relative risk 1.4 [95% CI, 0.99-2.1]; P?=?.06), compared with noncarriers.

CONCLUSIONS

The deficient CYP2B6 516 T allele is associated with higher efavirenz plasma drug levels and more frequent CNS-related symptoms.

Role of Cytochrome P450 2B6 Pharmacogenomics in Determining Efavirenz-Mediated Central Nervous System Toxicity, Treatment Outcomes, and Dosage Adjustments in Patients with Human Immunodeficiency Virus Infection

For treatment-naive patients with human immunodeficiency virus infection, efavirenz (EFV), together with tenofovir and emtricitabine, was once widely prescribed given its efficacy and ease of administration in a combination pill. However, the high rate of central nervous system (CNS) toxicities from EFV prompted the U.S. Department of Health and Human Services to move the EFV-based regimen from the recommended to the alternative category. For patients who do meet the criteria for newer recommended antiretroviral treatments, EFV is a viable option and often the mainstay of treatment outside the United States because newer antiretroviral treatments are more expensive. CNS toxicity occurring with the recommended standard dose of EFV remains a challenge and may in part be attributable to polymorphisms in cytochrome P450 (CYP) 2B6, the enzyme involved in the major metabolic pathway for converting EFV to inactive metabolites. Functionally deficient alleles of CYP2B6 such as CYP2B6*6, *18, and *22 may be responsible for significantly higher therapeutic concentrations of EFV at a standard dose of 600 mg/day. We conducted a thorough review of the reported studies to elucidate the relationship between polymorphisms in CYP2B6 with adverse events and treatment response, including virologic suppression, immunologic response, resistance, and discontinuation of treatment. Compelling evidence exists to support the case for CYP2B6 genotype-guided EFV therapy while acknowledging the need for prospective controlled clinical trials to evaluate its clinical utility.

Individualization of antiretroviral therapy--pharmacogenomic aspect

Combination therapy with three drug regimens for human immunodeficiency virus (HIV) infection significantly suppresses the viral replication. However, this therapeutic impact is restricted by adverse drug events and response in terms of short and long term efficacy. There are multiple factors involved in different responses to antiretrovirals (ARVs) such as age, body weight, disease status, diet and heredity. Pharmacogenomics deals with individual genetic make-up and its role in drug efficacy and toxicity. In depth genetic research has provided evidence to predict the risk of developing certain toxicities for which personalized screening and surveillance protocols may be developed to prevent side effects. Here we describe the use of pharmacogenomics for optimal use of HAART (highly active antiretroviral therapy).

Single Nucleotide Polymorphisms in Cellular Drug Transporters Are Associated with Intolerance to Antiretroviral Therapy in Brazilian HIV-1 Positive Individuals

Adverse reactions are the main cause of treatment discontinuation among HIV+ individuals. Genes related to drug absorption, distribution, metabolism and excretion (ADME) influence drug bioavailability and treatment response. We have investigated the association between single nucleotide polymorphisms (SNPs) in 29 ADME genes and intolerance to therapy in a case-control study including 764 individuals. Results showed that 15 SNPs were associated with intolerance to nucleoside and 11 to non-nucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs), and 8 to protease inhibitors (PIs) containing regimens under alpha = 0.05. After Bonferroni adjustment, two associations remained statistically significant. SNP rs2712816, at SLCO2B1 was associated to intolerance to NRTIs (OR_GA/AA = 2.37; p = 0.0001), while rs4148396, at ABCC2, conferred risk of intolerance to PIs containing regimens (OR_CT/TT = 2.64; p = 0.00009). Accordingly, haplotypes carrying rs2712816A and rs4148396T alleles were also associated to risk of intolerance to NRTIs and PIs, respectively. Our data reinforce the role of drug transporters in response to HIV therapy and may contribute to a future development of personalized therapies.

Insights into CYP2B6-mediated drug-drug interactions

Mounting evidence demonstrates that CYP2B6 plays a much larger role in human drug metabolism than was previously believed. The discovery of multiple important substrates of CYP2B6 as well as polymorphic differences has sparked increasing interest in the genetic and xenobiotic factors contributing to the expression and function of the enzyme. The expression of CYP2B6 is regulated primarily by the xenobiotic receptors constitutive androstane receptor (CAR) and pregnane X receptor (PXR) in the liver. In addition to CYP2B6, these receptors also mediate the inductive expression of CYP3A4, and a number of important phase II enzymes and drug transporters. CYP2B6 has been demonstrated to play a role in the metabolism of 2%–10% of clinically used drugs including widely used antineoplastic agents cyclophosphamide and ifosfamide, anesthetics propofol and ketamine, synthetic opioids pethidine and methadone, and the antiretrovirals nevirapine and efavirenz, among others. Significant inter-individual variability in the expression and function of the human CYP2B6 gene exists and can result in altered clinical outcomes in patients receiving treatment with CYP2B6-substrate drugs. These variances arise from a number of sources including genetic polymorphism, and xenobiotic intervention. In this review, we will provide an overview of the key players in CYP2B6 expression and function and highlight recent advances made in assessing clinical ramifications of important CYP2B6-mediated drug–drug interactions.

Pharmacogenetics of unboosted atazanavir in HIV-infected individuals in resource-limited settings: a sub-study of the AIDS Clinical Trials Group (ACTG) PEARLS study (NWCS 342)

OBJECTIVES

The multinational PEARLS (ACTG A5175) study, conducted mainly in resource-limited settings, identified an increased treatment failure rate among HIV-infected individuals randomized to once-daily unboosted atazanavir, didanosine-EC, and emtricitabine compared with efavirenz-based regimens. We evaluated associations between selected human genetic polymorphisms and atazanavir pharmacokinetics in PEARLS.

METHODS

Polymorphisms in CYP3A5, ABCB1, SLCO1B1 and NR1I2 were genotyped in PEARLS participants randomized to atazanavir plus didanosine-EC plus emtricitabine in Peru, South Africa and the USA, who also consented to genetic analysis. Non-linear mixed-effects population pharmacokinetic modelling was used to predict atazanavir oral clearance (CL/F) and concentration at 24 h (C24). Atazanavir mono-oxidation metabolites M1 and M2 were quantified from the same single-point plasma sample used to quantify the parent drug. Data were log10 transformed for statistical analysis using unpaired t-tests and one-way ANOVA and are presented as geometric mean (95% CI).

RESULTS

Eighty-four HIV-infected participants were genotyped, including 44 Black Africans or African Americans and 28 women. Median age was 34 years. We identified 56 CYP3A5 expressers and 28 non-expressers. Atazanavir CL/F and C24 did not differ between CYP3A5 expressers and non-expressers: 13.2 (12.1-14.4) versus 12.7 L/h (11.7-13.9), P = 0.61, and 75.3 (46.1-123.0) versus 130.9 ng/mL (86.9-197.2), P = 0.14, respectively. M1/atazanavir and M2/atazanavir ratios were higher in expressers than in non-expressers: 0.0083 (0.0074-0.0094) versus 0.0063 (0.0053-0.0075), P = 0.008, and 0.0065 (0.0057-0.0073) versus 0.0050 (0.0042-0.0061), P = 0.02, respectively.

CONCLUSIONS

Expression of CYP3A5 appears to be associated with increased M1 and M2 atazanavir metabolite formation, without significantly affecting parent compound pharmacokinetics.

Antiretroviral drug toxicity in relation to pharmacokinetics, metabolic profile and pharmacogenetics

INTRODUCTION

Besides therapeutic effectiveness, drug tolerability is a key issue for treatments that must be taken indefinitely. Given the high prevalence of toxicity in HIV therapy, the factors implicated in drug-induced morbidities should be identified in order to improve the safety, tolerability and adherence to the treatments. Current approaches have focused almost exclusively on parent drug concentrations; whereas recent evidence suggests that drug metabolites resulting from complex genetic and environmental influences can also contribute to treatment outcome. Pharmacogenetic variations have shown to play a relevant role in the variability observed in antiretroviral drug exposure, clinical response and sometimes toxicity. The integration of pharmacokinetic, pharmacogenetic and metabolic determinants will more probably address current therapeutic needs in patients.

AREAS COVERED

This review offers a concise description of three classes of antiretroviral drugs. The review looks at the metabolic profile of these drugs and gives a comprehensive summary of the existing literature on the influence of pharmacogenetics on their pharmacokinetics and metabolic pathways, and the associated drug or metabolite toxicity.

EXPERT OPINION

Due to the high prevalence of toxicity and the related risk of low adherence to the treatments, association of kinetic, genetic and metabolic markers predictive of therapeutic or toxicity outcomes could represent a more complete approach for optimizing antiretroviral therapy.

Patient willingness to undergo efavirenz dose reduction based on pharmacogenetic testing

AIM

Among HIV-infected adults receiving efavirenz fixed-dose combination tablets, genotyping could guide efavirenz dose reduction but would require more pills.

METHODS

We assessed willingness to dose reduce among 129 patients at an HIV primary care clinic in the southeastern USA.

RESULTS

When told that switching from one pill to two or three pills "might make you feel a little better", 47% expressed definite or possible willingness. This decreased to 9% if there was "a small chance it might not control your HIV as well". Clinical variables were not associated with willingness.

CONCLUSION

Many patients receiving a fixed-dose combination tablet may be willing to take more pills in order to dose reduce, guided by genetic testing, but only if virologic control is not compromised.

Dose Optimization of Efavirenz Based on Individual CYP2B6 Polymorphisms in Chinese Patients Positive for HIV

The purpose of this study was to investigate the impact of CYP2B6‐G516T polymorphisms on the pharmacokinetics (PKs) of efavirenz among the Chinese population and to propose doses for different genotypic populations that optimize therapeutic outcomes. Nonlinear mixed‐effect modeling was applied to describe PKs of efavirenz in Chinese patients with human immunodeficiency virus (HIV). Probabilities of successful treatment at different doses were obtained by simulations using the developed model to identify the optimal doses. The model was based on data from 163 individuals. Efavirenz clearance was found to be significantly influenced by CYP2B6‐G516T polymorphisms and body weight. The typical values of oral clearance were 10.2 L/h, 7.33 L/h, and 2.38 L/h and simulation results suggested that the optimal daily oral doses are 550 mg, 350 mg, and 100 mg for the GG, GT, and TT populations, respectively. The effect of CYP2B6‐G516T polymorphisms on efavirenz clearance was successfully quantified. Pharmacogenetics‐based dose individualization of efavirenz may optimize patient outcomes by promoting efficacy while minimizing central nervous system (CNS) side effects.

A pharmacist’s role in the individualization of treatment of HIV patients

The pharmacological treatment of HIV is complex and varies considerably among patients, as does the response of patients to therapy, requiring treatment plans that are closely tailored to individual needs. Pharmacists can take an active role in individualizing care by employing their knowledge of pharmacokinetics and pharmacogenetics and by interacting directly with patients in counseling sessions. These strategies promote the following: maintenance of plasma concentrations of antiretroviral agents within therapeutic ranges, prediction of pharmacological response of patients with certain genetic characteristics, and clinical control of HIV through the correct use of antiretroviral treatments. Together, these strategies can be used to tailor antiretroviral therapy to individual patients, thus improving treatment efficacy and safety.

Pharmacogenetics of drug-metabolizing enzymes in US Hispanics

Although the Hispanic population is continuously growing in the United States, they are underrepresented in pharmacogenetic studies. This review addresses the need for compiling available pharmacogenetic data in US Hispanics, discussing the prevalence of clinically relevant polymorphisms in pharmacogenes encoding for drug-metabolizing enzymes. CYP3A5*3 (0.245-0.867) showed the largest frequency in a US Hispanic population. A higher prevalence of CYP2C9*3, CYP2C19*4, and UGT2B7 IVS1+985 A>G was observed in US Hispanic vs. non-Hispanic populations. We found interethnic and intraethnic variability in frequencies of genetic polymorphisms for metabolizing enzymes, which highlights the need to define the ancestries of participants in pharmacogenetic studies. New approaches should be integrated in experimental designs to gain knowledge about the clinical relevance of the unique combination of genetic variants occurring in this admixed population. Ethnic subgroups in the US Hispanic population may harbor variants that might be part of multiple causative loci or in linkage-disequilibrium with functional variants. Pharmacogenetic studies in Hispanics should not be limited to ascertain commonly studied polymorphisms that were originally identified in their parental populations. The success of the Personalized Medicine paradigm will depend on recognizing genetic diversity between and within US Hispanics and the uniqueness of their genetic backgrounds.

Cost-effectiveness of CYP2B6 genotyping to optimize efavirenz dosing in HIV clinical practice

AIMS

To assess the cost-effectiveness of CYP2B6 genotyping to guide efavirenz dosing for initial HIV therapy in the USA.

METHODS

We used the Cost-Effectiveness of Preventing AIDS Complications (CEPAC) microsimulation model to project quality-adjusted life expectancy and lifetime costs (2014 US dollars) for efavirenz-based HIV therapy with or without CYP2B6 genotyping. We assumed that with genotyping 60% of patients would be eligible to receive lower doses.

RESULTS

Current care without CYP2B6 genotyping has an incremental cost-effectiveness ratio >$100,000/QALY compared with genotype-guided dosing, even if lower dosing reduces efficacy. When we assumed generic efavirenz availability, conclusions were similar unless lower dosing reduces efficacy by 6% or more.

CONCLUSION

CYP2B6 genotyping can inform efavirenz dosing and decrease HIV therapy cost.

Pharmacogenetics of non-nucleoside reverse transcriptase inhibitors (NNRTIs) in resource-limited settings: Influence on antiretroviral therapy response and concomitant anti-tubercular, antimalarial and contraceptive treatments

The burden of human immunodeficiency virus (HIV) is mainly concentrated to resources-limited countries where the response to available antiretroviral therapy is often limited by the occurrence of toxicity or by the emergence of HIV drug resistance. Efavirenz and nevirapine are the antiretroviral drugs most prescribed in resources-limited countries as part of antiretroviral combination therapy. Their metabolism and conjugation are largely influenced by enzymatic genetic polymorphisms. The genetic variability of their metabolism could be associated to different metabolic phenotypes causing reduced patients' adherence because of toxicity or drug-drug interactions with concomitant therapies. The purpose of this review is to summarize published evidence on pharmacogenetic and pharmacokinetic aspects related to efavirenz and nevirapine, the influence of concomitant anti-tubercular, anti-malarial or contraceptive treatments, and the impact of human genetic variation and drug-drug interaction on the virologic and immunologic response to antiretroviral therapy in resources-limited countries.

Genome-wide association study of virologic response with efavirenz-containing or abacavir-containing regimens in AIDS clinical trials group protocols

BACKGROUND

Efavirenz and abacavir are components of recommended first-line regimens for HIV-1 infection. We used genome-wide genotyping and clinical data to explore genetic associations with virologic failure among patients randomized to efavirenz-containing or abacavir-containing regimens in AIDS Clinical Trials Group (ACTG) protocols.

PARTICIPANTS AND METHODS

Virologic response and genome-wide genotype data were available from treatment-naive patients randomized to efavirenz-containing (n=1596) or abacavir-containing (n = 786) regimens in ACTG protocols 384, A5142, A5095, and A5202.

RESULTS

Meta-analysis of association results across race/ethnic groups showed no genome-wide significant associations (P < 5 × 10) with virologic response for either efavirenz or abacavir. Our sample size provided 80% power to detect a genotype relative risk of 1.8 for efavirenz and 2.4 for abacavir. Analyses focused on CYP2B genotypes that define the lowest plasma efavirenz exposure stratum did not show associations nor did analysis limited to gene sets predicted to be relevant to efavirenz and abacavir disposition.

CONCLUSION

No single polymorphism is associated strongly with virologic failure with efavirenz-containing or abacavir-containing regimens. Analyses to better consider context, and that minimize confounding by nongenetic factors, may show associations not apparent here.