Unexpectedly low drug exposures among Ugandan patients with TB and HIV receiving high-dose rifampicin

We characterized the pharmacokinetics of standard- and high-dose rifampicin in Ugandan adults with tuberculosis and HIV taking dolutegravir- or efavirenz-based antiretroviral therapy. A liver model with saturable hepatic extraction adequately described the data, and the increase in exposure between high and standard doses was 4.7-fold. This was lower than what previous reports of dose-exposure nonlinearity would predict and was ascribed to 38% lower bioavailability of the rifampicin-only top-up formulation compared to the fixed-dose combination.

Untimed Efavirenz Drug Levels After Switching From Brand to Generic Formulations: A Short Communication

BACKGROUND

In British Columbia, antiretrovirals are distributed at no cost to patients via a publicly funded program, using generic formulations if available. A generic efavirenz-emtricitabine-tenofovir DF (EFV-FTC-TDF) combination pill became available in April 2018. The authors compared EFV untimed drug levels in subjects switching from brand to generic EFV-FTC-TDF.

METHODS

Archived plasma HIV viral load samples were identified for consenting participants who switched from brand to generic EFV-FTC-TDF; 3 preswitch and 2-3 postswitch samples, collected ≥1 month apart were assessed for each subject. "Untimed" EFV concentrations with unknown dosing and collection time were assessed using a validated liquid chromatography-tandem mass spectrometry method. Participants' mean, minimum, and maximum EFV levels were compared using the Wilcoxon signed rank test. Participants with EFV levels in the range associated with lower risks of virologic failure and central nervous system toxicity (1000-4000 ng/mL), preswitch and postswitch, were enumerated.

RESULTS

EFV levels were assessed in 297 preswitch and 249 postswitch samples from 99 participants, having exposure to brand and generic EFV for a median of 103 (Q1-Q3: 87-116) and 10.3 (Q1-Q3: 8.9-11.7) months, respectively. The final brand sample was collected at a median of 98 days preswitch; the first generic sample was collected at a median of 133 days postswitch. No significant differences were observed in participant mean EFV levels before (median 1968 ng/mL; Q1-Q3: 1534-2878 ng/mL) and after (median 1987 ng/mL; Q1-Q3: 1521-2834 ng/mL) switch (P = 0.85). Eighty participants had mean EFV levels within the 1000-4000 ng/mL range on the brand drug, of which 74 remained within this range postswitch.

CONCLUSIONS

There were no statistically significant differences between untimed EFV levels in patients switching from the brand to generic EFV combination pill. Given the long elimination half-life of EFV, untimed drug levels may be a convenient way to estimate product bioequivalence.

Therapeutic drug monitoring study on the switch from coformulated 600-mg efavirenz, tenofovir disoproxil fumarate, and emtricitabine to coformulated 400-mg efavirenz, tenofovir disoproxil fumarate, and lamivudine among HIV-positive patients with viral suppression

OBJECTIVES

This study evaluated the efavirenz (EFV) mid-dose plasma concentration (C12), clinical efficacy, and safety after the switch to a single-tablet regimen containing tenofovir disoproxil fumarate (TDF), lamivudine (3TC), and 400-mg EFV in virally suppressed HIV-positive Taiwanese who were receiving co-formulated TDF, emtricitabine (FTC), and 600-mg EFV.

METHODS

In this single-arm, open-label study, HIV-positive adults who had undetectable plasma HIV RNA load (<50 copies/ml) for 6 months or longer while receiving co-formulated TDF, FTC, and 600-mg EFV with EFV C12 of ≥1 mg/L were enrolled. The participants were switched to co-formulated TDF, 3TC, and 400-mg EFV and followed for 24 weeks. The primary endpoint was the proportion of participants with EFV C12 ≥ 1 mg/L at Week 4. The secondary endpoints included virologic response and change of CD4 lymphocyte count up to Week 24. Specific adverse effects associated with EFV were recorded before and after the switch.

RESULTS

From December 2018 to January 2019, 50 participants were enrolled. EFV C12 remained ≥1 mg/L in 48 (96.0%) participants with a median reduction of 38.9% (interquartile range 29.0-44.4) at Week 4 after switch. All participants had undetectable plasma HIV RNA by Week 12, whereas 96.0% of them remained so at Week 24. Significant increases of CD4 lymphocyte count were observed at Weeks 12 and 24. Thirty-three participants (66.0%) reported improvement of pre-existing adverse effects.

CONCLUSION

Switch to coformulated TDF, 3TC, and 400-mg EFV in virally suppressed HIV-positive Taiwanese maintained effective EFV concentration and viral suppression while the adverse effects were reduced.

Discovery of LYC-55716: A Potent, Selective, and Orally Bioavailable Retinoic Acid Receptor-Related Orphan Receptor-γ (RORγ) Agonist for Use in Treating Cancer

Retinoic acid receptor-related orphan receptor γ (RORc, RORγ, or NR1F3) is the nuclear receptor master transcription factor that drives the function and development of IL-17-producing T helper cells (Th17), cytotoxic T cells (Tc17), and subsets of innate lymphoid cells. Activation of RORγ+ T cells in the tumor microenvironment is hypothesized to render immune infiltrates more effective at countering tumor growth. To test this hypothesis, a family of benzoxazines was optimized to provide LYC-55716 (37c), a potent, selective, and orally bioavailable small-molecule RORγ agonist. LYC-55716 decreases tumor growth and enhances survival in preclinical tumor models and was nominated as a clinical development candidate for evaluation in patients with solid tumors.

Point-of-Care Detection of Nonadherence to Antiretroviral Treatment for HIV-1 in Resource-Limited Settings Using Drug Level Testing for Efavirenz, Lopinavir, and Dolutegravir: A Validation and Pharmacokinetic Simulation Study

BACKGROUND

Virological failure during antiretroviral treatment (ART) may indicate the presence of drug resistance, but may also originate from nonadherence. Qualitative detection of ART components using drug level testing may be used to differentiate between these scenarios. We aimed to validate and implement qualitative point-of-care drug level tests for efavirenz (EFV), lopinavir (LPV), and dolutegravir (DTG) in rural South Africa.

METHODS

Qualitative performance of immunoassays for EFV, LPV, and DTG was assessed by calculating limit of detection (LoD), region of uncertainty, and qualitative agreement with a reference test. Minimum duration of nonadherence resulting in a negative drug level test was assessed by simulation of treatment cessation using validated population pharmacokinetic models.

RESULTS

LoD was 0.05 mg/L for EFV, 0.06 mg/L for LPV, and 0.02 mg/L for DTG. Region of uncertainty was 0.01-0.06 mg/L for EFV, 0.01-0.07 mg/L for LPV, and 0.01-0.02 mg/L for DTG. Qualitative agreement with reference testing at the LoD in patient samples was 95.2% (79/83) for EFV, 99.3% (140/141) for LPV, and 100% (118/118) for DTG. After simulated treatment cessation, median time to undetectability below LoD was 7 days [interquartile range (IQR) 4-13] for EFV, 30 hours (IQR 24-36) for LPV, and 6 days (IQR 4-7) for DTG.

CONCLUSIONS

We demonstrate that qualitative ART drug level testing using immunoassays is feasible in a rural resource-limited setting. Implementation of this technology enables reliable detection of recent nonadherence and may allow for rapid and cost-effective differentiation between patients in need for adherence counseling and patients who require drug resistance testing or alternative treatment.

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.

Dosage Optimization of Efavirenz Based on a Population Pharmacokinetic-Pharmacogenetic Model of HIV-infected Patients in Thailand

PURPOSE

Efavirenz exhibits high interindividual variability in plasma concentrations, leading to unpredictable efficacy and toxicity. Polymorphism of CYP2B6 516G > T has been found to predominantly contribute to efavirenz variability. However, dosage recommendations incorporating CYP2B6 516G > T polymorphism have not been investigated in the Thai population. This study aimed to develop a population model of the pharmacokinetic properties of efavirenz, and to investigate the impact of patients' characteristics and CYP2B6 516G > T polymorphism on the pharmacokinetic properties of efavirenz. Model-based simulations were performed to provide genotype-based dosage optimization in a Thai population.

METHODS

Plasma efavirenz concentrations measured at 12 h post-dose in 360 Thai HIV-infected patients with and without tuberculosis were analyzed by the nonlinear mixed-effects modeling approach. A 1-compartment model with first-order absorption and elimination was used for describing the pharmacokinetic properties of efavirenz.

FINDINGS

The allele frequency of CYP2B6 516G > T was 34.17%. The efavirenz oral clearance were 11.9, 8.0, and 2.8 L/h in patients weighing 57 kg and having the CYP2B6 516 GG, 516 GT, and 516 TT genotypes, respectively. The use of rifampicin increased efavirenz oral clearance by 28%. The results from the simulations suggest that efavirenz dosages of 400, 300, and 100 mg once daily in Thai HIV mono-infected patients, and 800, 600, and 200 mg once daily in HIV/tuberculosis co-infected patients carrying CYP2B6 516 GG, 516 GT, and 516 TT, respectively.

IMPLICATION

The results from this study provide a rationale for efavirenz dose adjustment based on CYP2B6 516G > T polymorphism in Thai HIV-infected patients, which could help to improve treatment outcomes in this population. ClinicalTrials.gov identifier: NCT01138267.

Organogel Nanoparticles as a New Way to Improve Oral Bioavailability of Poorly Soluble Compounds

PURPOSE

The aim of the study was to evaluate organogel nanoparticles as a lipophilic vehicle to increase the oral bioavailability of poorly soluble compounds. Efavirenz (EFV), a Biopharmaceutical Classification System (BCS) Class II, was used as drug model.

METHODS

Organogel nanoparticles loaded with EFV were formulated with sunflower oil, 12-hydroxystearic acid (HSA) and polyvinyl alcohol (PVA). Various parameters have been investigated in the current study such as (i) the release profile of organogel assessed by USP 4 cell flow dialysis, (ii) the impact of organogel on intestinal absorption, using Caco-2 cells as in vitro model and jejunum segments as ex vivo assay and (iii) the bioavailability of organogel following oral pharmacokinetic study.

RESULTS

250-300 nm spherical particles with a final concentration of 4.75 mg/mL drug loading were obtained, corresponding to a thousand fold increase in EFV solubility, combined to a very high encapsulation efficiency (>99.8%). Due to rapid diffusion, drug was immediately released from the nanoparticles. The biopharmaceutical evaluation on ex vivo jejunum segments demonstrated an increased absorption of EFV from organogel nanoparticles compare to a native EFV suspension. In vitro assays combining Caco-2 cell cultures with TEM and confocal microscopy demonstrated passive diffusion, while paracellular integrity and endocytosis activity remain expelled. Oral pharmacokinetics of EFV organogel nanoparticles improve oral bioavailability (F_r: 249%) and quick absorption compared to EFV suspension.

CONCLUSION

Organogel nanoparticles increase the bioavailability of BCS Class II drugs. The main phenomena is simply oil transfer from the gelled particles through the cell membrane.

Influence of a herbal preparation on the pharmacokinetics of highly active antiretroviral therapy drugs in rats

Shenlin Fuzheng Capsule (SLFZC) is a herbal preparation used for HIV/AIDS in Guangxi, China. This study was designed to evaluate the influence of SLFZC on the pharmacokinetics of highly active antiretroviral therapy (HAART) drugs, zidovudine (3'-azido-3'-deoythymidine, AZT), 2',3'-dideoxy-3'-thiacytidine (3TC) and efavirenz (EFV). Thirty-six male SD rats were divided into three groups. Group A was given a combination of AZT, 3TC and EFV (AZT/3TC/EFV). Group B rats were given AZT/3TC/EFV simultaneously with SLFZC. Group C rats were given AZT/3TC/EFV 2h prior to SLFZC. Blood samples were collected at fixed time intervals. Plasma concentration of each antiretroviral drug was tested for calculation of pharmacokinetic parameters. There was significant difference among groups with respect to t1/2 for AZT (F=3.371, P<0.05), but the Student-Newman-Keuls (SNK) pairwise multiple comparison procedure showed no statistical differences in all pairwise comparisons (P>0.05). There were no significant differences among groups in terms of C_max, T _max, AUC_0-12h and CL for AZT, and t_1/2, C_max, T_max, AUC_0-12h and CL for 3TC and EFV, respectively. The results indicate that SLFZC has little impact on pharmacokinetic properties of AZT, 3TC and EFV.

Safety and pharmacokinetics of dolutegravir in pregnant mothers with HIV infection and their neonates: A randomised trial (DolPHIN-1 study)

BACKGROUND

The global transition to use of dolutegravir (DTG) in WHO-preferred regimens for HIV treatment is limited by lack of knowledge on use in pregnancy. Here we assessed the relationship between drug concentrations (pharmacokinetics, PK), including in breastmilk, and impact on viral suppression when initiated in the third trimester (T3).

METHODS AND FINDINGS

In DolPHIN-1, HIV-infected treatment-naïve pregnant women (28-36 weeks of gestation, age 26 (19-42), weight 67kg (45-119), all Black African) in Uganda and South Africa were randomised 1:1 to dolutegravir (DTG) or efavirenz (EFV)-containing ART until 2 weeks post-partum (2wPP), between 9th March 2017 and 16th January 2018, with follow-up until six months postpartum. The primary endpoint was pharmacokinetics of DTG in women and breastfed infants; secondary endpoints included maternal and infant safety and viral suppression. Intensive pharmacokinetic sampling of DTG was undertaken at day 14 and 2wPP following administration of a medium-fat breakfast, with additional paired sampling between maternal plasma and cord blood, breastmilk and infant plasma. No differences in median baseline maternal age, gestation (31 vs 30 weeks), weight, obstetric history, viral load (4.5 log10 copies/mL both arms) and CD4 count (343 vs 466 cells/mm3) were observed between DTG (n = 29) and EFV (n = 31) arms. Although DTG Ctrough was below the target 324ng/mL (clinical EC90) in 9/28 (32%) mothers in the third trimester, transfer across the placenta (121% of plasma concentrations) and into breastmilk (3% of plasma concentrations), coupled with slower elimination, led to significant infant plasma exposures (3-8% of maternal exposures). Both regimens were well-tolerated with no significant differences in frequency of adverse events (two on DTG-ART, one on EFV-ART, all considered unrelated to drug). No congenital abnormalities were observed. DTG resulted in significantly faster viral suppression (P = 0.02) at the 2wPP visit, with median time to <50 copies/mL of 32 vs 72 days. Limitations related to the requirement to initiate EFV-ART prior to randomisation, and to continue DTG for only two weeks postpartum.

CONCLUSION

Despite low plasma DTG exposures in the third trimester, transfer across the placenta and through breastfeeding was observed in this study, with persistence in infants likely due to slower metabolic clearance. HIV RNA suppression <50 copies/mL was twice as fast with DTG compared to EFV, suggesting DTG has potential to reduce risk of vertical transmission in mothers who are initiated on treatment late in pregnancy.

TRIAL REGISTRATION

clinicaltrials.gov NCT02245022.

Role of efavirenz plasma concentrations on long-term HIV suppression and immune restoration in HIV-infected children

Background

To access the long term relationship between efavirenz plasma concentrations and evolution of HIV RNA loads and CD4 cell counts in children.

Methods

Retrospective analysis of data from HIV-infected children on first line efavirenz-containing regimen. A population pharmacokinetic-pharmacodynamic (PK-PD) model was developed to describe the evolution of HIV RNA load and CD4 cell count (efficacy outcomes) in relation to efavirenz plasma concentration. Individual CYP2B6 516 G>T genotype data were not available for this analysis. A score (IS_EFV) quantifying the effect of efavirenz concentrations on the long-term HIV replication was calculated from efavirenz concentrations and PD parameters and, a value of IS_EFV below which HIV replication is likely not suppressed was determined. Cox proportional hazards regression models were used to assess the association of the risk of viral replication with IS_EFV, and with efavirenz mid-dose concentration(C₁₂).

Results

At treatment initiation, median (interquartile range, IQR) age was 8 years (5 to 10), body weight 17 kg (14 to 23), HIV RNA load 5.1 log₁₀ copies/mL (4.6 to 5.4), and CD4 cell count 71 cells/mm³. A model of PK-PD viral dynamics assuming that efavirenz decreases the rate of infected host cells adequately described the relationship of interest. After adjusting for age, baseline HIV RNA load and CD4 cell counts an IS_EFV <85% was significantly associated with a higher risk of viral replication (p-value <0.001) while no significant association was observed with C₁₂ <1.0 mg/L.

Conclusion

The IS_EFV score was a good predictor of viral replication in children on efavirenz-based treatment.

Doravirine and the Potential for CYP3A-Mediated Drug-Drug Interactions

Identifying and understanding potential drug-drug interactions (DDIs) are vital for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. This article discusses DDIs between doravirine, a nonnucleoside reverse transcriptase inhibitor (NNRTI), and cytochrome P450 3A (CYP3A) substrates and drugs that modulate CYP3A activity. Consistent with previously published in vitro data and DDI trials with the CYP3A substrates midazolam and atorvastatin, doravirine did not have any meaningful impact on the pharmacokinetics of the CYP3A substrates ethinyl estradiol and levonorgestrel. Coadministration of doravirine with CYP3A inhibitors (ritonavir or ketoconazole) increased doravirine exposure approximately 3-fold. However, these increases were not considered clinically meaningful. Conversely, previously published trials showed that coadministered CYP3A inducers (rifampin and rifabutin) decreased doravirine exposure by 88% and 50%, respectively (K. L. Yee, S. G. Khalilieh, R. I. Sanchez, R. Liu, et al., Clin Drug Investig 37:659-667, 2017 [https://doi.org/10.1007/s40261-017-0513-4]; S. G. Khalilieh, K. L. Yee, R. I. Sanchez, R. Liu, et al., J Clin Pharmacol 58:1044-1052, 2018 [https://doi.org/10.1002/jcph.1103]), while doravirine exposure following prior efavirenz administration led to an initial reduction in doravirine exposure of 62%, but the reduction became less pronounced with time (K. L. Yee, R. I. Sanchez, P. Auger, R. Liu, et al., Antimicrob Agents Chemother 61:e01757-16, 2017 [https://doi.org/10.1128/AAC.01757-16]). Overall, the coadministration of doravirine with CYP3A inhibitors and substrates is, therefore, supported by these data together with efficacy and safety data from clinical trials, while coadministration with strong CYP3A inducers, such as rifampin, cannot be recommended. Concomitant dosing with rifabutin (a CYP3A inducer less potent than rifampin) is acceptable if doravirine dosing is adjusted from once to twice daily; however, the effect of other moderate inducers on doravirine pharmacokinetics is unknown.

Predicting Efavirenz Concentrations in the Brain Tissue of HIV-Infected Individuals and Exploring their Relationship to Neurocognitive Impairment

Sparse data exist on the penetration of antiretrovirals into brain tissue. In this work, we present a framework to use efavirenz (EFV) pharmacokinetic (PK) data in plasma, cerebrospinal fluid (CSF), and brain tissue of eight rhesus macaques to predict brain tissue concentrations in HIV-infected individuals. We then perform exposure-response analysis with the model-predicted EFV area under the concentration-time curve (AUC) and neurocognitive scores collected from a group of 24 HIV-infected participants. Adult rhesus macaques were dosed daily with 200 mg EFV (as part of a four-drug regimen) for 10 days. Plasma was collected at 8 time points over 10 days and at necropsy, whereas CSF and brain tissue were collected at necropsy. In the clinical study, data were obtained from one paired plasma and CSF sample of participants prescribed EFV, and neuropsychological test evaluations were administered across 15 domains. PK modeling was performed using ADAPT version 5.0 Biomedical Simulation Resource, Los Angeles, CA) with the iterative two-stage estimation method. An eight-compartment model best described EFV distribution across the plasma, CSF, and brain tissue of rhesus macaques and humans. Model-predicted median brain tissue concentrations in humans were 31 and 8,000 ng/mL, respectively. Model-predicted brain tissue AUC was highly correlated with plasma AUC (γ = 0.99, P < 0.001) but not CSF AUC (γ = 0.34, P = 0.1) and did not show any relationship with neurocognitive scores (γ < 0.05, P > 0.05). This analysis provides an approach to estimate PK the brain tissue in order to perform PK/pharmacodynamic analyses at the target site.

Effect of Rifampin-Isoniazid-Containing Antituberculosis Therapy on Efavirenz Pharmacokinetics in HIV-Infected Children 3 to 14 Years Old

We compared efavirenz pharmacokinetic (PK) parameters in children with tuberculosis (TB)/human immunodeficiency virus (HIV) coinfection on and off first-line antituberculosis therapy to that in HIV-infected children. Children 3 to 14 years old with HIV infection, with and without TB, were treated with standard efavirenz-based antiretroviral therapy without any efavirenz dose adjustments. The new World Health Organization-recommended antituberculosis drug dosages were used in the coinfected participants. Steady-state efavirenz concentrations after 4 weeks of antiretroviral therapy were measured using validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) assays. Pharmacokinetic parameters were calculated using noncompartmental analysis. Between groups, PK parameters were compared by Wilcoxon rank-sum test and within group by signed-rank test. Of the 105 participants, 43 (41.0%) had TB coinfection. Children with TB/HIV coinfection compared to those with HIV infection were younger, had lower median weight-for-age Z score, and received a higher median efavirenz weight-adjusted dose. Geometric mean (GM) efavirenz peak concentration (Cmax), concentration at 12 h (C12h), Cmin, and total area under the curve from time 0 to 24 h (AUC0-24h) values were similar in children with HIV infection and those with TB/HIV coinfection during anti-TB therapy. Geometric mean efavirenz C12h, Cmin, and AUC0-24h values were lower in TB/HIV-coinfected patients off anti-TB therapy than in the children with HIV infection or TB/HIV coinfection on anti-TB therapy. Efavirenz clearance was lower and AUC0-24h was higher on than in patients off anti-TB therapy. Reduced efavirenz clearance by first-line anti-TB therapy at the population level led to similar PK parameters in HIV-infected children with and without TB coinfection. Our findings do not support modification of efavirenz weight-band dosing guidelines based on TB coinfection status in children. (The study was registered with ClinicalTrials.gov under registration number NCT01704144.).

A Mechanism-Based Population Pharmacokinetic Analysis Assessing the Feasibility of Efavirenz Dose Reduction to 400 mg in Pregnant Women

BACKGROUND

Reducing the dose of efavirenz can improve safety, reduce costs, and increase access for patients with HIV infection. According to the World Health Organization, a similar dosing strategy for all patient populations is desirable for universal roll-out; however, it remains unknown whether the 400 mg daily dose is adequate during pregnancy.

METHODS

We developed a mechanistic population pharmacokinetic model using pooled data from women included in seven studies (1968 samples, 774 collected during pregnancy). Total and free efavirenz exposure (AUC24 and C12) were predicted for 400 (reduced) and 600 mg (standard) doses in both pregnant and non-pregnant women.

RESULTS

Using a 400 mg dose, the median efavirenz total AUC24 and C12 during the third trimester of pregnancy were 91 and 87% of values among non-pregnant women, respectively. Furthermore, the median free efavirenz C12 and AUC24 were predicted to increase during pregnancy by 11 and 15%, respectively.

CONCLUSIONS

It was predicted that reduced-dose efavirenz provides adequate exposure during pregnancy. These findings warrant prospective confirmation.

Effect of Antiretroviral Therapy on Plasma Concentrations of Chloroquine and Desethyl-chloroquine

The effect of antiretroviral therapy (ART) on chloroquine and desethyl-chloroquine plasma concentrations was evaluated in clinical trial participants. Concentrations did not differ among participants receiving protease inhibitor-based ART (n = 9), efavirenz-based ART (n = 15), or other ART (n = 8) and those not receiving ART (n = 31). Efavirenz seemed to inhibit chloroquine desethylation.

Safety, efficacy, and dose response of the maturation inhibitor GSK3532795 (formerly known as BMS-955176) plus tenofovir/emtricitabine once daily in treatment-naive HIV-1-infected adults: Week 24 primary analysis from a randomized Phase IIb trial

GSK3532795 (formerly known as BMS-955176) is a second-generation maturation inhibitor targeting a specific Gag cleavage site between capsid p24 and spacer peptide 1 of HIV-1. Study 205891 (previously AI468038) investigated the efficacy, safety, and dose response of GSK3532795 in treatment-naive, HIV-1-infected participants. Study 205891 (NCT02415595) was a Phase IIb, randomized, active-controlled, double-blind, international trial. Participants were randomized 1:1:1:1 to one of three GSK3532795 arms at doses 60 mg, 120 mg or 180 mg once daily (QD), or to efavirenz (EFV) at 600 mg QD, each in combination with tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) (300/200 mg QD). Primary endpoint was proportion of participants with plasma HIV-1 RNA <40 copies/mL at Week 24. Between May 2015 and May 2016, 206 participants received treatment. At Week 24, 76–83% participants receiving GSK3532795 and 77% receiving EFV achieved HIV-1 RNA <40 copies/mL. Fifteen participants receiving GSK3532795 and one receiving EFV met resistance testing criteria; 10/15 receiving GSK3532795 had emergent substitutions at reverse transcriptase positions M184, and one at position K65, while the participant receiving EFV did not have any nucleoside reverse transcriptase inhibitor (NRTI)/non-NRTI mutations. EFV, relative to GSK3532795, had more serious adverse events (9% versus 5%) and adverse events leading to discontinuation (17% versus 5%). However, 3–4-fold higher rates of gastrointestinal adverse events were observed with GSK3532795 relative to EFV. GSK3532795 combined with TDF/FTC is efficacious with 24 weeks of therapy. However, GSK3532795 showed a higher rate of gastrointestinal intolerability and treatment-emergent resistance to the NRTI backbone relative to EFV.

Trial registration: ClinicalTrials.gov NCT02415595.

Noncovalent PEG Coating of Nanoparticle Drug Carriers Improves the Local Pharmacokinetics of Rectal Anti-HIV Microbicides

Antiretroviral drug nanocarriers hold great promise for developing anti-human immunodeficiency virus (HIV) rectal microbicides. However, challenges remain, namely, concerning which properties are more suited for enhancing colorectal distribution and retention of microbicide compounds. In this work, we developed and assessed the in vitro and in vivo performance of poly(lactic- co-glycolic acid) (PLGA)-based nanoparticles (NPs) as carriers for the model drug efavirenz (EFV). We particularly focused on the effect of noncovalent poly(ethylene glycol) coating of PLGA NPs (PEG-PLGA NPs) conferring a mucus-diffusive behavior on the pharmacokinetics (PK) of EFV following rectal administration to mice. Drug-loaded PLGA NPs and PEG-PLGA NPs (200-225 nm) were obtained by nanoprecipitation. Both types of systems were able to retain native antiretroviral activity of EFV in vitro, while featuring lower cytotoxicity against different epithelial cell lines and HIV target cells. Also, PLGA NPs and PEG-PLGA NPs were readily taken up by colorectal cell lines and mildly reduced EFV permeation while increasing membrane retention in Caco-2 and Caco-2/HT29-MTX cell monolayer models. When administered intrarectally to CD-1 mice in phosphate-buffered saline (pH 7.4), EFV-loaded PEG-PLGA NPs consistently provided higher drug levels in colorectal tissues and lavages, as compared to free EFV or drug-loaded PLGA NPs. Mean values for the area-under-the-curve between 15 min and 12 h following administration were particularly higher for PEG-PLGA NPs in distal and middle colorectal tissues, with relative bioavailability values of 3.7 and 29, respectively, as compared to free EFV (2.2 and 6.0 over PLGA NPs, respectively). Systemic exposure to EFV was reduced for all treatments. NPs were further shown safe after once-daily administration for 14 days, as assessed by histological analysis of colorectal tissues and chemokine/cytokine assay of rectal lavages. Overall, PEG-PLGA NPs demonstrated to be safe carriers for rectal microbicide drug delivery and able to provide enhanced local PK that could be valuable in preventing rectal HIV transmission.

Efavirenz and Lopinavir Levels in HIV-Infected Women and Their Nursing Infants, in Mali

Limited data are currently available on antiretroviral pharmacokinetics in breast milk (BM) and in breastfed infants' blood. To explore these parameters in patients in Mali, we measured plasma antiretroviral levels in human immunodeficiency virus (HIV)-infected mothers and their breastfed infants over 6 months. We specifically analyzed the concentrations of efavirenz (EFV) and lopinavir (LPV) in the plasma of mothers living with HIV and their breastfed infants. Blood samples were collected at delivery and at month 1, 3, and 6 postpartum. EFV and LPV concentrations were measured by liquid chromatography-tandem mass spectrometry. HIV-1 RNA load was measured by Abbott M2000RT RealTime System at delivery and 6 months postpartum for mothers, and at 3 and 6 months postbirth for infants. The median duration of antiretroviral therapy at study inclusion was 57 months [interquartile range (IQR), 0-168 months]. The median EFV ratios of infant plasma/maternal plasma (MP) were 0.057 at month 1, 0.072 at month 3, and 0.048 at month 6. During the study period, the median BM/MP ratio of EFV was 1.16 (IQR, 0.96-20.62), which corresponds to a relative infant dose of 2.46% of the recommended weight-adjusted pediatric EFV dose at month 6. The apparent infant clearance of EFV was 0.146 l/h per kilogram at month 6. The LPV concentrations in the plasma of all infants were undetectable. No drug-related adverse reaction or toxicity was observed in any of the infants. The two women who presented a viral load of >50 copies/ml at month 6 had undetectable plasma drug concentrations at the same period. This study showed that breastfed infants received a low level of EFV but not LPV from their treated mothers.

Effects of rolapitant administered orally on the pharmacokinetics of dextromethorphan (CYP2D6), tolbutamide (CYP2C9), omeprazole (CYP2C19), efavirenz (CYP2B6), and repaglinide (CYP2C8) in healthy subjects

Purpose

Rolapitant is a neurokinin-1 receptor antagonist indicated in combination with other antiemetic agents in adults for the prevention of delayed chemotherapy-induced nausea and vomiting. We evaluated the effects of rolapitant oral on the pharmacokinetics of probe substrates for cytochrome P450 (CYP) 2D6 (dextromethorphan), 2C9 (tolbutamide), 2C19 (omeprazole), 2B6 (efavirenz), and 2C8 (repaglinide) in healthy subjects.

Methods

This open-label, multipart, randomized, phase 1 study assessed cohorts of 20–26 healthy subjects administered dextromethorphan, tolbutamide plus omeprazole, efavirenz, or repaglinide with and without single, oral doses of rolapitant. Maximum plasma analyte concentrations (C_max) and area under the plasma analyte concentration–time curves (AUC) were estimated using noncompartmental analysis, and geometric mean ratios (GMRs) and 90% confidence intervals for the ratios of test (rolapitant plus probe substrate) to reference (probe substrate alone) treatment were calculated.

Results

Rolapitant significantly increased the systemic exposure of dextromethorphan in terms of C_max and AUC_0–inf by 2.2- to 3.3-fold as observed in GMRs on days 7 and 14. Rolapitant did not affect systemic exposure of tolbutamide, and minor excursions outside of the 80–125% no effect limits were detected for omeprazole, efavirenz, and repaglinide.

Conclusions

Inhibition of dextromethorphan by a single oral dose of rolapitant 180 mg is clinically significant and can last at least 7 days. No clinically significant interaction was observed between rolapitant and substrates of CYP2C9, CYP2C19, CYP2B6, or CYP2C8. CYP2D6 substrate drugs with a narrow therapeutic index may require monitoring for adverse reactions if given concomitantly with rolapitant.

Variants in the CYP2B6 3'UTR Alter In Vitro and In Vivo CYP2B6 Activity: Potential Role of MicroRNAs

CYP2B6*6 and CYP2B6*18 are the most clinically important variants causing reduced CYP2B6 protein expression and activity. However, these variants do not account for all variability in CYP2B6 activity. Emerging evidence has shown that genetic variants in the 3'UTR may explain variable drug response by altering microRNA regulation. Five 3'UTR variants were associated with significantly altered efavirenz AUC0-48 (8-OH-EFV/EFV) ratios in healthy human volunteers. The rs70950385 (AG>CA) variant, predicted to create a microRNA binding site for miR-1275, was associated with a 33% decreased CYP2B6 activity among normal metabolizers (AG/AG vs. CA/CA (P < 0.05)). In vitro luciferase assays were used to confirm that the CA on the variant allele created a microRNA binding site causing an 11.3% decrease in activity compared to the AG allele when treated with miR-1275 (P = 0.0035). Our results show that a 3'UTR variant contributes to variability in CYP2B6 activity.

Development of Guanfacine Extended-Release Dosing Strategies in Children and Adolescents with ADHD Using a Physiologically Based Pharmacokinetic Model to Predict Drug-Drug Interactions with Moderate CYP3A4 Inhibitors or Inducers

BACKGROUND

Guanfacine extended-release (GXR) is an orally administered, non-stimulant treatment for children and adolescents with attention-deficit/hyperactivity disorder (ADHD) and is primarily metabolized by the 3A4 isozyme of cytochrome P450 (CYP3A4). The results of clinical pharmacokinetic (PK) studies indicate that guanfacine is sensitive to drug-drug interactions (DDIs) perpetrated by strong inhibitors and inducers of CYP3A4.

OBJECTIVE

The aim was to provide guidance on the possible requirement for GXR dose adjustment in children and adolescents with ADHD by predicting DDIs following co-administration with moderate CYP3A4 inhibitors and inducers.

METHODS

A physiologically based PK model for GXR orally administered to healthy adults was developed based on physicochemical, in vitro and clinical PK data. The model was validated using clinical PK data for co-administration of GXR with ketoconazole (strong CYP3A4 inhibitor) or rifampicin (strong CYP3A4 inducer).

RESULTS

Model predictions indicated that co-administration of GXR with the moderate CYP3A4 inhibitors erythromycin 500 mg three times a day or fluconazole 200 mg daily (q.d.) increased the guanfacine area under the plasma concentration-time curve (AUC) by 2.31-fold or 1.98-fold, respectively, compared with GXR monotherapy. The moderate CYP3A4 inducer efavirenz 400 mg or 600 mg q.d. was predicted to reduce guanfacine AUC to 58 or 33% of its value for GXR monotherapy, respectively.

CONCLUSION

Without the requirement for additional clinical studies, the following GXR dose recommendations were developed and approved for US labeling for use in children and adolescents with ADHD: (1) decrease GXR to 50% of the usual target dose when it is co-administered with strong or moderate CYP3A4 inhibitors; (2) consider titrating GXR up to double the usual target dose over 1-2 weeks when it is co-administered with strong or moderate CYP3A4 inducers.

Development and validation of reversed-phase HPLC gradient method for the estimation of efavirenz in plasma

Efavirenz is an anti-viral agent of non-nucleoside reverse transcriptase inhibitor category used as a part of highly active retroviral therapy for the treatment of infections of human immune deficiency virus type-1. A simple, sensitive and rapid reversed-phase high performance liquid chromatographic gradient method was developed and validated for the determination of efavirenz in plasma. The method was developed with high performance liquid chromatography using Waters X-Terra Shield, RP18 50 x 4.6 mm, 3.5 μm column and a mobile phase consisting of phosphate buffer pH 3.5 and Acetonitrile. The elute was monitored with the UV-Visible detector at 260 nm with a flow rate of 1.5 mL/min. Tenofovir disoproxil fumarate was used as internal standard. The method was validated for linearity, precision, accuracy, specificity, robustness and data obtained were statistically analyzed. Calibration curve was found to be linear over the concentration range of 1-300 μg/mL. The retention times of efavirenz and tenofovir disoproxil fumarate (internal standard) were 5.941 min and 4.356 min respectively. The regression coefficient value was found to be 0.999. The limit of detection and the limit of quantification obtained were 0.03 and 0.1 μg/mL respectively. The developed HPLC method can be useful for quantitative pharmacokinetic parameters determination of efavirenz in plasma.

Population Pharmacokinetics Modeling of Unbound Efavirenz, Atazanavir, and Ritonavir in HIV-Infected Subjects With Aging Biomarkers

Unbound drug is the pharmacodynamically relevant concentration. This study aimed to determine if chronologic age or markers of biologic aging, such as the frailty phenotype and p16INK4a gene expression, altered unbound pharmacokinetics (PKs) of efavirenz (EFV) and atazanavir/ritonavir (ATV/RTV). Sixty human immunodeficiency virus (HIV)-infected participants receiving EFV and 31 receiving ATV/RTV provided 1 to 11 samples to quantify total and unbound plasma concentrations. Population PK models with total and unbound concentrations simultaneously described are developed for each drug. The unbound fractions for EFV, ATV, and RTV are 0.65%, 5.67%, and 0.63%, respectively. Covariate analysis suggests RTV unbound PK is sensitive to body size; unbound fraction of RTV is 34% lower with body mass index (BMI) above 30 kg/m2 . No alterations in drug clearance or unbound fraction with age, frailty, or p16INK4a expression were observed. Assessing functional and physiologic aging markers to inform potential PK changes is necessary to determine if drug/dosing changes are warranted in the aging population.

Efavirenz dissolution enhancement III: Colloid milling, pharmacokinetics and electronic tongue evaluation

Efavirenz (EFV), a non-nucleoside reverse transcriptase inhibitor (NNRTI), is part of first-line therapy for the treatment of human immunodeficiency virus type 1 infection (HIV-1/AIDS). This drug shows relatively low oral absorption and bioavailability, as well as high intra- and inter-subject variability. Several studies have shown that treatment failure and adverse effects are associated with low and high EFV plasma concentrations, respectively. Some studies suggest different EFV formulations to minimize inter-patient variability and improve its solubility and dissolution; however, all of these formulations are complex, using for instance, cyclodextrins, dendrimers and polymeric nanoparticles, rendering them inviable industrially. The aim of this work was to prepare simple and low-cost suspensions of EFV for improvement of solubility and dissolution rate by using colloid mill, spray or freeze-drying, and characterization of the powders obtained. The results demonstrated an increase in the dissolution rate of EFV, using 0.2% of sodium lauryl sulfate (SLS) and 0.2% of hydroxypropylcellulose (HPC) or hydroxypropylmetilcellulose (HPMC) in both freeze and spray dried powders. The pharmacokinetic studies demonstrated improved pharmacokinetic parameters for the formulation containing SLS and HPC. The powders obtained, which present enhanced dissolution properties, can be incorporated in a solid dosage form for treatment of AIDS in paediatric patients with promising results.

Efavirenz Has the Highest Anti-Proliferative Effect of Non-Nucleoside Reverse Transcriptase Inhibitors against Pancreatic Cancer Cells

Background

Cancer prevention and therapy in HIV-1-infected patients will play an important role in future. The non-nucleoside reverse transcriptase inhibitors (NNRTI) Efavirenz and Nevirapine are cytotoxic against cancer cells in vitro. As other NNRTIs have not been studied so far, all clinically used NNRTIs were tested and the in vitro toxic concentrations were compared to drug levels in patients to predict possible anti-cancer effects in vivo.

Methods

Cytotoxicity was studied by Annexin-V-APC/7AAD staining and flow cytometry in the pancreatic cancer cell lines BxPC-3 and Panc-1 and confirmed by colony formation assays. The 50% effective cytotoxic concentrations (EC50) were calculated and compared to the blood levels in our patients and published data.

Results

The in vitro EC50 of the different drugs in the BxPC-3 pancreatic cancer cells were: Efavirenz 31.5μmol/l (= 9944ng/ml), Nevirapine 239μmol/l (= 63786ng/ml), Etravirine 89.0μmol/l (= 38740ng/ml), Lersivirine 543μmol/l (= 168523ng/ml), Delavirdine 171μmol/l (= 78072ng/ml), Rilpivirine 24.4μmol/l (= 8941ng/ml). As Efavirenz and Rilpivirine had the highest cytotoxic potential and Nevirapine is frequently used in HIV-1 positive patients, the results of these three drugs were further studied in Panc-1 pancreatic cancer cells and confirmed with colony formation assays. 205 patient blood levels of Efavirenz, 127 of Rilpivirine and 31 of Nevirapine were analyzed. The mean blood level of Efavirenz was 3587ng/ml (range 162–15363ng/ml), of Rilpivirine 144ng/ml (range 0-572ng/ml) and of Nevirapine 4955ng/ml (range 1856–8697ng/ml). Blood levels from our patients and from published data had comparable Efavirenz levels to the in vitro toxic EC50 in about 1 to 5% of all patients.

Conclusion

All studied NNRTIs were toxic against cancer cells. A low percentage of patients taking Efavirenz reached in vitro cytotoxic blood levels. It can be speculated that in HIV-1 positive patients having high Efavirenz blood levels pancreatic cancer incidence might be reduced. Efavirenz might be a new option in the treatment of cancer.

The effect of malnutrition on the pharmacokinetics and virologic outcomes of lopinavir, efavirenz and nevirapine in food insecure HIV-infected children in Tororo, Uganda

BACKGROUND

Malnutrition may impact the pharmacokinetics (PKs) of antiretroviral medications and virologic responses in HIV-infected children. The authors therefore evaluated the PK of nevirapine (NVP), efavirenz (EFV) and lopinavir (LPV) in associations with nutritional status in a cohort of HIV-infected Ugandan children.

METHODS

Sparse dried blood spot samples from Ugandan children were used to estimate plasma concentrations. Historical PK data from children from 3 resource-rich countries (RRC) were utilized to develop the PK models.

RESULTS

Concentrations in 330 dried blood spot from 163 Ugandan children aged 0.7-7 years were analyzed in reference to plasma PK data (1189 samples) from 204 children from RRC aged 0.5-12 years. Among Ugandan children, 48% was malnourished (underweight, thin or stunted). Compared to RRC, Ugandan children exhibited reduced bioavailability of EFV and LPV; 11% (P=0.045) and 18% (P=0.008), respectively. In contrast, NVP bioavailability was 46% higher in Ugandan children (P<0.001) with a trend toward greater bioavailability when malnourished. Children receiving LPV, EFV or NVP had comparable risk of virologic failure. Among children on NVP, low height and weight for age Z scores were associated with reduced risk of virologic failure (P=0.034, P=0.068, respectively).

CONCLUSIONS

Ugandan children demonstrated lower EFV and LPV and higher NVP exposure compared to children in RRC, perhaps reflecting the consequence of malnutrition on bioavailability. In children receiving NVP, the relation between exposure, malnutrition and outcome turned out to be marginally significant. Further investigations are warranted using more intensive PK measurements and adequate adherence assessments, to further assess causes of virologic failure in Ugandan children.

Combined effect of CYP2B6 and NAT2 genotype on plasma efavirenz exposure during rifampin-based antituberculosis therapy in the STRIDE study

In STRIDE, slow metabolizer CYP2B6 and NAT2 genotypes were each associated with increased plasma efavirenz concentrations during antituberculosis therapy. Concentrations were greater on therapy than off therapy in 58% with CYP2B6 and 93% with NAT2 slow metabolizer genotypes. Individuals with slow metabolizer genotypes in both genes had markedly elevated concentrations.

Pharmacokinetics of efavirenz and treatment of HIV-1 among pregnant women with and without tuberculosis coinfection

BACKGROUND

Pregnancy and tuberculosis treatment or prophylaxis can affect efavirenz pharmacokinetics, maternal human immunodeficiency virus type 1 (HIV-1) treatment outcomes, and mother-to-child transmission (MTCT) risk.

METHODS

We evaluated a prospective cohort of pregnant, HIV-infected women with and without tuberculosis in Soweto, South Africa. Pharmacokinetic sampling was performed at gestation week 37 and during the postpartum period. Efavirenz trough concentrations (Cmin) were predicted using population pharmacokinetic models. HIV-viral load was measured at delivery for mothers and at 6 weeks of age for infants.

RESULTS

Ninety-seven women participated; 44 had tuberculosis. Median efavirenz Cmin during pregnancy was 1.35 µg/mL (interquartile range [IQR], 0.90-2.07 µg/mL; 27% had an efavirenz Cmin of < 1 µg/mL), compared with a median postpartum value of 2.00 µg/mL (IQR, 1.40-3.59 µg/mL; 13% had an efavirenz Cmin of < 1 µg/mL). A total of 72% of pregnant women with extensive CYP2B6 genotypes had an efavirenz Cmin of <1 µg/mL. Rifampin did not reduce the efavirenz Cmin. Isoniazid (for prophylaxis or treatment), though, reduced the rate of efavirenz clearance. At delivery, median durations of ART were 13 weeks (IQR, 9-18 weeks) and 21 weeks (IQR, 13-64 weeks) for women with and those without tuberculosis, respectively; 55% and 83%, respectively, had a viral load of <20 copies/mL (P = .021). There was 1 case of MTCT.

CONCLUSIONS

Pregnancy increased the risk of low efavirenz concentrations, but MTCT was rare. A detectable HIV-viral load at delivery was more common among pregnant women with tuberculosis, in whom ART was generally initiated later.

Structural features of β2 adrenergic receptor: crystal structures and beyond

The beta2-adrenergic receptor (β2AR) family, which is the largest family of cell surface receptors in humans. Extra attention has been focused on the human GPCRs because they have been studied as important protein targets for pharmaceutical drug development. In fact, approximately 40% of marketed drugs directly work on GPCRs. GPCRs respond to various extracellular stimuli, such as sensory signals, neurotransmitters, chemokines, and hormones, to induce structural changes at the cytoplasmic surface, activating downstream signaling pathways, primarily through interactions with heterotrimeric G proteins or through G-protein independent pathways, such as arrestin. Most GPCRs, except for rhodhopsin, which contains covalently linked 11 cis-retinal, bind to diffusible ligands, having various conformational states between inactive and active structures. The first human GPCR structure was determined using an inverse agonist bound β2AR in 2007 and since then, more than 20 distinct GPCR structures have been solved. However, most GPCR structures were solved as inactive forms, and an agonist bound fully active structure is still hard to obtain. In a structural point of view, β2AR is relatively well studied since its fully active structure as a complex with G protein as well as several inactive structures are available. The structural comparison of inactive and active states gives an important clue in understanding the activation mechanism of β2AR. In this review, structural features of inactive and active states of β2AR, the interaction of β2AR with heterotrimeric G protein, and the comparison with β1AR will be discussed.

A phase II trial evaluating the efficacy and safety of efavirenz in metastatic castration-resistant prostate cancer

BACKGROUND

Preclinical studies demonstrated that non-nucleoside reverse transcriptase inhibitors used for the treatment of HIV could antagonize tumor development. This led us to assess the efficacy of efavirenz in patients with metastatic castration-resistant prostate cancer (mCRPC) in a multicenter phase II study.

METHODS

We used a Simon two-stage design and a 3-month prostate-specific antigen (PSA) nonprogression rate of 40% as a primary objective. Patients received 600 mg efavirenz daily with the possibility of a dose increase in case of PSA progression. Exploratory analyses included pharmacokinetics of efavirenz plasma concentrations and correlations with clinical outcomes.

RESULTS

Among 53 assessable patients, we observed 15 instances of PSA nonprogression at 3 months, corresponding to a nonprogression rate of 28.3% (95% confidence interval: 16.8%-42.3%). The exploratory analysis revealed that for the 7 patients in whom optimal plasma concentration of efavirenz was achieved, PSA progression was observed in only 28.6% compared with 81.8% of patients with suboptimal plasma concentrations of efavirenz.

CONCLUSION

Although 600 mg efavirenz did not statistically improve the PSA nonprogression rate, our exploratory analysis suggests that higher plasma concentrations of this drug (i.e., use of increased dosages) may be of potential benefit for the treatment of mCRPC.

Enhanced oral bioavailability of efavirenz by solid lipid nanoparticles: in vitro drug release and pharmacokinetics studies

Solid lipid nanoparticle is an efficient lipid based drug delivery system which can enhance the bioavailability of poorly water soluble drugs. Efavirenz is a highly lipophilic drug from nonnucleoside inhibitor category for treatment of HIV. Present work illustrates development of an SLN formulation for Efavirenz with increased bioavailability. At first, suitable lipid component and surfactant were chosen. SLNs were prepared and analyzed for physical parameters, stability, and pharmacokinetic profile. Efavirenz loaded SLNs were formulated using Glyceryl monostearate as main lipid and Tween 80 as surfactant. ESLN-3 has shown mean particle size of 124.5 ± 3.2 nm with a PDI value of 0.234, negative zeta potential, and 86% drug entrapment. In vitro drug release study has shown 60.6-98.22% drug release in 24 h by various SLN formulations. Optimized SLNs have shown good stability at 40°C ± 2°C and 75 ± 5% relative humidity (RH) for 180 days. ESLN-3 exhibited 5.32-fold increase in peak plasma concentration (C max) and 10.98-fold increase in AUC in comparison to Efavirenz suspension (ES).

Are lopinavir and efavirenz serum concentrations in HIV-infected children in the therapeutic range in clinical practice?

BACKGROUND

In antiretroviral treatment the role of therapeutic drug monitoring via measurement of serum levels remains unclear, especially in children.

AIM

To quantify exposure to LPV and EFV in children receiving therapy in a routine clinical setting in order to identify risk factors associated with inadequate drug exposure.

METHOD

A prospective study was conducted in a routine clinical setting in Tygerberg Children's Hospital, South Africa. A total of 53 random serum levels were analyzed. Serum concentrations were determined by an established high-performance liquid chromatography method.

RESULTS

Of 53 HIV-infected children treated with lopinavir (n = 29, median age 1·83 y) or efavirenz (n = 24, median age 9·3 years), 12 showed serum levels outside the therapeutic range (efavirenz) or below Cmin (lopinavir). Low bodyweight, rifampicin co-treatment, and significant comorbidity were potential risk factors for inadequate drug exposure.

CONCLUSION

These findings, together with previous studies, indicate that therapeutic drug monitoring can improve the management of antiretroviral therapy in children at risk.

Plasma concentrations, efficacy and safety of efavirenz in HIV-infected adults treated for tuberculosis in Cambodia (ANRS 1295-CIPRA KH001 CAMELIA trial)

OBJECTIVE

To assess efavirenz plasma concentrations and their association with treatment efficacy and tolerance of efavirenz 600 mg daily in HIV-tuberculosis co-infected patients.

METHODS

HIV-infected adults with CD4+ T cell count ≤ 200/mm(3) received standard 6-month tuberculosis treatment and antiretroviral therapy including a daily-dose of 600 mg of efavirenz, irrespective of their body weight. Mid-dose blood samples were drawn both on tuberculosis treatment (week +2 and week +6 after antiretroviral therapy initiation, and week 22 of follow-up) and off tuberculosis treatment (week 50 of follow-up). Considered therapeutic range was 1,000 to 4,000 ng/mL. Multivariate analysis was performed to evaluate the association between efavirenz concentration below 1,000 ng/mL and virological failure. Linear regression was used to test the association between efavirenz exposure and CD4+ T cell gain. Severe side effects potentially related to efavirenz were described and their association with efavirenz exposure was tested by multivariate analysis.

RESULTS

Efavirenz plasma concentrations were available in 540 patients. Median [interquartile range] efavirenz concentrations were 2,674 ng/mL [1,690-4,533], 2,667 ng/mL [1,753-4,494] and 2,799 ng/mL [1,804-4,744] at week +2, week +6, week 22, respectively, and 2,766 ng/mL [1,941-3,976] at week 50. Efavirenz concentrations were lower at week 50 (off rifampicin) compared to week 22 (on rifampicin) (p<0.001). Late attendance to study visit and low hemoglobinemia were the only factors associated with an increased risk of efavirenz concentration below 1,000 ng/mL. Efavirenz concentration below 1,000 ng/mL was not associated with treatment failure. Efavirenz concentration above 4,000 ng/mL was associated with higher risk of central nervous system side effects (p<0.001) and of hepatotoxicity (p<0.001).

CONCLUSION

Body weight and tuberculosis treatment were not associated with low efavirenz concentrations or treatment failure, supporting the 600 mg daily-dose of efavirenz in HIV-tuberculosis co-infected patients. High efavirenz concentrations were related to a higher risk of central nervous system side effects and hepatotoxicity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01300481.

Plasma concentrations of efavirenz and nevirapine among HIV-infected patients with immunological failure attending a tertiary hospital in North-western Tanzania

BACKGROUND

Sub-therapeutic and supra-therapeutic plasma concentrations of antriretrovirals are the significant causes of treatment failure and toxicity respectively among HIV-infected patients. We conducted this study to determine the pattern of efavirenz and nevirapine plasma drug concentrations among adult HIV-infected patients with immunological failure attending at a tertiary hospital in North-western Tanzania.

MATERIALS AND METHODS

A cross-sectional study was conducted among adult HIV-infected patients with immunological failure who have been on either efavirenz or nevirapine based antiretroviral regimen for more than 6 months. Patients were serially enrolled through routine Care and Treatment Clinic (CTC) activities. Plasma drug concentrations for efavirenz and nevirapine were determined by high performance liquid chromatography (HPLC) and Gas Chromatography (GC) respectively. Demographic, clinical and laboratory data such as viral load and CD4 counts were collected. Data analysis was done using STATA 12.

RESULTS

Of the 152 patients with immunological failure enrolled, the sub-therapeutic, therapeutic and supra-therapeutic plasma antiretroviral drug concentrations were found in 43/152 (28.3%), 76/152 (50.0%) and 33/152 (21.7%) respectively. Half of the patients were outside therapeutic window with either sub-therapeutic or supra-therapeutic plasma ARV drug concentrations. There was a significant difference in distribution of ARV adherence (p-value<0.001), NRTI backbone (p-value = 0.039), HIV stage (p-value = 0.026) and viral load (p-value = 0.007) within sub-therapeutic, therapeutic and supra-therapeutic ARV plasma drug concentrations.

CONCLUSION

There is a wide inter-individual variability of plasma ARV concentrations among HIV patients with immunological failure, with a large proportion of patients being outside therapeutic window. This variability is significant based on ARV adherence, NRTI backbone, viral load and HIV stage. Routine therapeutic drug monitoring (TDM) could assist identifying these patients early and making timely correction to avoid virological failure, poor immunological outcome and prevent associated drug toxicities. Nonetheless, ARV adherence should be strictly emphasized on HIV patients with immunological failure.

Hair and plasma data show that lopinavir, ritonavir, and efavirenz all transfer from mother to infant in utero, but only efavirenz transfers via breastfeeding

BACKGROUND

As efforts intensify to eliminate perinatal HIV transmission, understanding kinetics of maternal-to-child transfer of antiretrovirals during pregnancy and breastfeeding is critical. Antiretroviral levels in plasma, cord blood, and breastmilk reflect exposure over short intervals. Hair concentrations reflect cumulative exposure and can uniquely quantify in utero transfer of maternal medications to infants. We measured plasma and hair antiretroviral levels in HIV-infected Ugandan mothers and their infants at delivery and during breastfeeding to assess transfer.

METHODS

HIV-infected pregnant women were randomized to lopinavir/ritonavir- or efavirenz-based therapy in a larger trial (the Prevention of Malaria and HIV disease in Tororo, PROMOTE). At 0, 8, and 12 weeks postpartum, plasma antiretroviral levels were measured in 117 mother-infant pairs; hair levels were assayed at 12 weeks. Ratios and correlations of infant:maternal concentrations were calculated.

RESULTS

By 12 weeks, 90.4% of mothers reported exclusive breastfeeding. Hair and plasma levels over time suggest moderate (47%) to extensive (87%) in utero transfer of lopinavir and ritonavir, respectively, but negligible transfer of either via breastfeeding. Moderate transfer of efavirenz occurs during pregnancy and breastfeeding (40% cumulative; 15% during breastfeeding). Despite differences in exposure, no infant seroconversions or correlations between infant hair/plasma antiretroviral levels and adverse effects were observed.

CONCLUSIONS

Using a unique approach combining hair and plasma data, we found that different antiretrovirals have distinct kinetics of mother-to-infant transfer. Efavirenz transfers during both pregnancy and breastfeeding, whereas lopinavir and ritonavir transfer only in utero. Further study of the degree and timing of maternal-to-child transfer by antiretroviral will help optimize strategies that protect infants and minimize toxicities during periods of risk.

Importance of ethnicity, CYP2B6 and ABCB1 genotype for efavirenz pharmacokinetics and treatment outcomes: a parallel-group prospective cohort study in two sub-Saharan Africa populations

Objectives

We evaluated the importance of ethnicity and pharmacogenetic variations in determining efavirenz pharmacokinetics, auto-induction and immunological outcomes in two African populations.

Methods

ART naïve HIV patients from Ethiopia (n = 285) and Tanzania (n = 209) were prospectively enrolled in parallel to start efavirenz based HAART. CD4+ cell counts were determined at baseline, 12, 24 and 48 weeks. Plasma and intracellular efavirenz and 8-hydroxyefvairenz concentrations were determined at week 4 and 16. Genotyping for common functional CYP2B6, CYP3A5, ABCB1, UGT2B7 and SLCO1B1 variant alleles were done.

Result

Patient country, CYP2B6*6 and ABCB1 c.4036A>G (rs3842A>G) genotype were significant predictors of plasma and intracellular efavirenz concentration. CYP2B6*6 and ABCB1 c.4036A>G (rs3842) genotype were significantly associated with higher plasma efavirenz concentration and their allele frequencies were significantly higher in Tanzanians than Ethiopians. Tanzanians displayed significantly higher efavirenz plasma concentration at week 4 (p<0.0002) and week 16 (p = 0.006) compared to Ethiopians. Efavirenz plasma concentrations remained significantly higher in Tanzanians even after controlling for the effect of CYP2B6*6 and ABCB1 c.4036A>G genotype. Within country analyses indicated a significant decrease in the mean plasma efavirenz concentration by week 16 compared to week 4 in Tanzanians (p = 0.006), whereas no significant differences in plasma concentration over time was observed in Ethiopians (p = 0.84). Intracellular efavirenz concentration and patient country were significant predictors of CD4 gain during HAART.

Conclusion

We report substantial differences in efavirenz pharmacokinetics, extent of auto-induction and immunologic recovery between Ethiopian and Tanzanian HIV patients, partly but not solely, due to pharmacogenetic variations. The observed inter-ethnic variations in efavirenz plasma exposure may possibly result in varying clinical treatment outcome or adverse event profiles between populations.

A sensitive and selective liquid chromatography/tandem mass spectrometry method for quantitative analysis of efavirenz in human plasma

A selective and a highly sensitive method for the determination of the non-nucleoside reverse transcriptase inhibitor (NNRTI), efavirenz, in human plasma has been developed and fully validated based on high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). Sample preparation involved protein precipitation followed by one to one dilution with water. The analyte, efavirenz was separated by high performance liquid chromatography and detected with tandem mass spectrometry in negative ionization mode with multiple reaction monitoring. Efavirenz and ¹³C₆-efavirenz (Internal Standard), respectively, were detected via the following MRM transitions: m/z 314.20243.90 and m/z 320.20249.90. A gradient program was used to elute the analytes using 0.1% formic acid in water and 0.1% formic acid in acetonitrile as mobile phase solvents, at a flow-rate of 0.3 mL/min. The total run time was 5 min and the retention times for the internal standard (¹³C₆-efavirenz) and efavirenz was approximately 2.6 min. The calibration curves showed linearity (coefficient of regression, r>0.99) over the concentration range of 1.0-2,500 ng/mL. The intraday precision based on the standard deviation of replicates of lower limit of quantification (LLOQ) was 9.24% and for quality control (QC) samples ranged from 2.41% to 6.42% and with accuracy from 112% and 100-111% for LLOQ and QC samples. The inter day precision was 12.3% and 3.03-9.18% for LLOQ and quality controls samples, and the accuracy was 108% and 95.2-108% for LLOQ and QC samples. Stability studies showed that efavirenz was stable during the expected conditions for sample preparation and storage. The lower limit of quantification for efavirenz was 1 ng/mL. The analytical method showed excellent sensitivity, precision, and accuracy. This method is robust and is being successfully applied for therapeutic drug monitoring and pharmacokinetic studies in HIV-infected patients.

24-Month adherence, tolerance and efficacy of once-a-day antiretroviral therapy with didanosine, lamivudine, and efavirenz in African HIV-1 infected children: ANRS 12103/12167

BACKGROUND

There is no data on long-term benefit of once-a-day antiretroviral therapy (ART) with combination of DDI, 3TC and EFV to allow its use in future therapeutic strategies.

OBJECTIVES

To assess 24-month immuno-virological, adherence, tolerance, and effectiveness of a once-a-day ART with DDI, 3TC and EFV.

METHODS

A phase 2 open trial including 51 children aged from 30 months to 15 years, monitored a once-a-day regimen for 24 months from 2006 to 2008 in the Departement de Pediatrie du CHUSS, at Bobo-Dioulasso in Burkina Faso. We tested immunological and virological response, adherence, tolerance and resistance of the treatment.

RESULTS

Children with CD4 >25% at 24 months were 67.4% (33/49) CI 95% [54%, 80%]. The proportion of children with viral plasma RNA <300 cp / ml at 24 months of treatment was 81.6 % (40/49) CI [68.0% 91.2%]. Good adherence was obtained with more than 88% adherence > 95% over the 24 months. Drugs were well tolerated.

CONCLUSIONS

Given the limited number of antiretroviral drugs available in Africa and the inadequacy of laboratory monitoring in support program, once-a-day treatment and especially the DDI-based combination strategies could be an attractive operational option.

Significant pharmacokinetic interactions between artemether/lumefantrine and efavirenz or nevirapine in HIV-infected Ugandan adults

OBJECTIVES

Co-administration of artemether/lumefantrine with antiretroviral therapy has potential for pharmacokinetic drug interactions. We investigated drug-drug interactions between artemether/lumefantrine and efavirenz or nevirapine.

METHODS

We performed a cross-over study in which HIV-infected adults received standard six-dose artemether/lumefantrine 80/480 mg before and at efavirenz or nevirapine steady state. Artemether, dihydroartemisinin, lumefantrine, efavirenz and nevirapine plasma concentrations were measured and compared.

RESULTS

Efavirenz significantly reduced artemether maximum concentration (C(max)) and plasma AUC (median 29 versus 12 ng/mL, P < 0.01, and 119 versus 25 ng · h/mL, P < 0.01), dihydroartemisinin C(max) and AUC (median 120 versus 26 ng/mL, P < 0.01, and 341 versus 84 ng · h/mL, P < 0.01), and lumefantrine C(max) and AUC (median 8737 versus 6331 ng/mL, P = 0.03, and 280 370 versus 124 381 ng · h/mL, P < 0.01). Nevirapine significantly reduced artemether C(max) and AUC (median 28 versus 11 ng/mL, P < 0.01, and 123 versus 34 ng · h/mL, P < 0.01) and dihydroartemisinin C(max) and AUC (median 107 versus 59 ng/mL, P < 0.01, and 364 versus 228 ng · h/mL, P < 0.01). Lumefantrine C(max) and AUC were non-significantly reduced by nevirapine. Artemether/lumefantrine reduced nevirapine C(max) and AUC (median 8620 versus 4958 ng/mL, P < 0.01, and 66 329 versus 35 728 ng · h/mL, P < 0.01), but did not affect efavirenz exposure.

CONCLUSIONS

Co-administration of artemether/lumefantrine with efavirenz or nevirapine resulted in a reduction in artemether, dihydroartemisinin, lumefantrine and nevirapine exposure. These drug interactions may increase the risk of malaria treatment failure and development of resistance to artemether/lumefantrine and nevirapine. Clinical data from population pharmacokinetic and pharmacodynamic trials evaluating the impact of these drug interactions are urgently needed.

Efavirenz pharmacokinetics in cerebrospinal fluid and plasma over a 24-hour dosing interval

We determined the pharmacokinetics of efavirenz in plasma and cerebrospinal fluid (CSF) over a 24-h dosing interval in a patient who had undergone a lumbar drain because of cryptococcal meningitis. Drug concentrations were determined by high-performance liquid chromatography-tandem mass spectrometry in paired CSF (n = 24) and plasma (n = 25) samples. The median plasma efavirenz concentration was 3,718 ng/ml (range, 2,439 to 4,952), and the median CSF concentration was 16.3 ng/ml (range, 7.3 to 22.3). The CSF/plasma area-under-the-curve ratio was 0.0044 corresponding to a CSF penetration of 0.44% of plasma.

A single-nucleotide polymorphism in CYP2B6 leads to >3-fold increases in efavirenz concentrations in plasma and hair among HIV-infected women

BACKGROUND

Efavirenz exhibits marked interindividual variability in plasma levels and toxicities. Prior pharmacogenetic studies usually measure exposure via single plasma levels, examine limited numbers of polymorphisms, and rarely model multiple contributors. We analyzed numerous genetic and nongenetic factors impacting short-term and long-term exposure in a large heterogeneous population of human immunodeficiency virus (HIV)-infected women.

METHODS

We performed 24-hour intensive pharmacokinetic studies in 111 women receiving efavirenz under actual-use conditions and calculated the area-under-the-concentration-time curve (AUC) to assess short-term exposure; the efavirenz concentration in hair was measured to estimate long-term exposure. A total of 182 single-nucleotide polymorphisms (SNPs) and 45 haplotypes in 9 genes were analyzed in relationship to exposure by use of multivariate models that included a number of nongenetic factors.

RESULTS

Efavirenz AUCs increased 1.26-fold per doubling of the alanine aminotransferase level and 1.23-fold with orange and/or orange juice consumption. Individuals with the CYP2B6 516TT genotype displayed 3.5-fold increases in AUCs and 3.2-fold increases in hair concentrations, compared with individuals with the TG/GG genotype. Another SNP in CYP2B6 (983TT) and a p-glycoprotein haplotype affected AUCs without substantially altering long-term exposure.

CONCLUSIONS

This comprehensive pharmacogenomics study showed that individuals with the CYP2B6 516TT genotype displayed >3-fold increases in both short-term and long-term efavirenz exposure, signifying durable effects. Pharmacogenetic testing combined with monitoring of hair levels may improve efavirenz outcomes and reduce toxicities.

Mechanism of efavirenz influence on methadone pharmacokinetics and pharmacodynamics

Mechanisms by which efavirenz diminishes methadone plasma concentrations are unknown. This investigation determined efavirenz influence on clinical methadone disposition and miosis, intravenous and oral alfentanil clearance (hepatic and intestinal cytochrome P450 3A4/5 (CYP3A4/5) activity), fexofenadine disposition (intestinal transporters activity), and efavirenz clearance and 8-hydroxylation (CYP2B6 activity), and human hepatocyte effects. Efavirenz induced systemic and oral alfentanil clearances two- to fivefold and induced efavirenz 8-hydroxylation. Efavirenz stereoselectively decreased methadone plasma concentrations 50-70%. Methadone systemic and oral clearances, hepatic clearance and extraction ratio, N-demethylation, and metabolite formation clearance were stereoselectively increased two- to threefold. Bioavailability decreased. Efavirenz shifted methadone concentration-miosis curves leftward and upward. Efavirenz induced hepatocyte CYP2B6 and CYP3A4 expression, activity, and methadone N-demethylation. Results show that efavirenz coinduced hepatic CYP2B6 and CYP3A4/5, coinduced hepatic and intestinal CYP3A4/5, and coinduced gastrointestinal CYP3A4/5 and efflux transporters. Methadone disposition was most consistent with efavirenz induction of hepatic CYP2B6-mediated methadone N-demethylation. Efavirenz may alter methadone pharmacodynamics.

Pharmacogenetic & pharmacokinetic biomarker for efavirenz based ARV and rifampicin based anti-TB drug induced liver injury in TB-HIV infected patients

BACKGROUND

Implication of pharmacogenetic variations and efavirenz pharmacokinetics in concomitant efavirenz based antiviral therapy and anti-tubercular drug induced liver injury (DILI) has not been yet studied. We performed a prospective case-control association study to identify the incidence, pharmacogenetic, pharmacokinetic and biochemical predictors for anti-tubercular and antiretroviral drugs induced liver injury (DILI) in HIV and tuberculosis (TB) co-infected patients.

METHODS AND FINDINGS

Newly diagnosed treatment naïve TB-HIV co-infected patients (n = 353) were enrolled to receive efavirenz based ART and rifampicin based anti-TB therapy, and assessed clinically and biochemically for DILI up to 56 weeks. Quantification of plasma efavirenz and 8-hydroxyefaviernz levels and genotyping for NAT2, CYP2B6, CYP3A5, ABCB1, UGT2B7 and SLCO1B1 genes were done. The incidence of DILI and identification of predictors was evaluated using survival analysis and the Cox Proportional Hazards Model. The incidence of DILI was 30.0%, or 14.5 per 1000 person-week, and that of severe was 18.4%, or 7.49 per 1000 person-week. A statistically significant association of DILI with being of the female sex (p = 0.001), higher plasma efavirenz level (p = 0.009), efavirenz/8-hydroxyefavirenz ratio (p = 0.036), baseline AST (p = 0.022), ALT (p = 0.014), lower hemoglobin (p = 0.008), and serum albumin (p = 0.007), NAT2 slow-acetylator genotype (p = 0.039) and ABCB1 3435TT genotype (p = 0.001).

CONCLUSION

We report high incidence of anti-tubercular and antiretroviral DILI in Ethiopian patients. Between patient variability in systemic efavirenz exposure and pharmacogenetic variations in NAT2, CYP2B6 and ABCB1 genes determines susceptibility to DILI in TB-HIV co-infected patients. Close monitoring of plasma efavirenz level and liver enzymes during early therapy and/or genotyping practice in HIV clinics is recommended for early identification of patients at risk of DILI.

Effects of WIN 55,212-2 mesylate (a synthetic cannabinoid) on the protective action of clonazepam, ethosuximide, phenobarbital and valproate against pentylenetetrazole-induced clonic seizures in mice

The aim of this study was to determine the effect of WIN 55,212-2 mesylate (WIN - a non-selective cannabinoid CB1 and CB2 receptor agonist) on the protective action of four classical antiepileptic drugs (AEDs: clonazepam [CZP], ethosuximide [ETS], phenobarbital [PB], and valproate [VPA]) in the mouse pentylenetetrazole (PTZ)-induced clonic seizure model. WIN (15 mg/kg, i.p.) significantly enhanced the anticonvulsant action of ETS, PB and VPA, but not that of CZP against PTZ-induced clonic seizures. The ED(50) values of ETS, PB and VPA were reduced from 148.0, 13.9 and 137.1mg/kg to 104.0, 8.3 and 85.6 mg/kg, respectively (P<0.05). WIN (5 and 10mg/kg, i.p.) had no impact on the anticonvulsant action of all studied AEDs against PTZ-induced clonic seizures. WIN (15 mg/kg, i.p.) significantly elevated total brain concentrations of ETS and VPA, but not those of CZP and PB in mice. Moreover, WIN combined with CZP, ETS, PB and VPA significantly impaired motor performance, long-term memory and muscular strength in mice subjected to the chimney, passive avoidance and grip-strength tests, respectively. Pharmacodynamic enhancement of the anticonvulsant action of PB by WIN against PTZ-induced clonic seizures is favorable from a preclinical viewpoint. Advantageous effects of WIN in combination with ETS and VPA against PTZ-induced seizures were pharmacokinetic in nature. However, WIN combined with CZP, ETS, PB and VPA impaired motor coordination and long-term memory as well as reduced skeletal muscular strength in the experimental animals.

Plasma efavirenz in HIV infected children treated with generic antiretroviral drugs in India

We measured plasma concentration of efavirenz (EFV) in 16 HIV-infected Indian children receiving antiretroviral treatment at Government ART centres. The mean 12 hour concentration was 2.39 ug/mL (range: 0.72- 7.82 ug/mL). The majority of children treated with generic EFV at currently recommended doses had blood levels within the therapeutic range.

Factors influencing lopinavir and atazanavir plasma concentration

BACKGROUND

The protease inhibitors lopinavir and atazanavir are both recommended for treatment of HIV-infected patients. Considerable inter-individual variability in plasma concentration has been observed for both drugs. The aim of this study was to evaluate which demographic factors and concomitant drugs are associated with lopinavir and atazanavir plasma concentration.

METHODS

Data from the Liverpool TDM (therapeutic drug monitoring) Registry were linked with the UK Collaborative HIV Cohort (CHIC) study. For each patient, the first measurement of lopinavir (twice daily) or atazanavir [once daily, ritonavir boosted (/r) or unboosted] plasma concentration was included. Linear regression was used to evaluate the association of dose, gender, age, weight, ethnicity and concomitant antiretroviral drugs or rifabutin with log-transformed drug concentration, adjusted for time since last intake.

RESULTS

Data from 439 patients on lopinavir (69% 400 mg/r, 31% 533 mg/r; 3% concomitant rifabutin) and 313 on atazanavir (60% 300 mg/r, 32% 400 mg/r, 8% 400 mg) were included. Multivariable models revealed the following predictors for lopinavir concentration: weight (11% decrease per additional 10 kg; P = 0.001); dose (25% increase for 533 mg/r; P = 0.024); and rifabutin (116% increase; P < 0.001). For atazanavir the predictors were dose (compared with 300 mg/r: 40% increase for 400 mg/r, 67% decrease for 400 mg; overall P < 0.001) and efavirenz (32% decrease; P = 0.016) but not tenofovir (P = 0.54).

CONCLUSIONS

This analysis confirms that efavirenz decreases atazanavir concentrations, and there was a negative association of weight and lopinavir concentrations. The strong impact of rifabutin on lopinavir concentration should be studied further.

Anticancer activity of CX-3543: a direct inhibitor of rRNA biogenesis

Hallmark deregulated signaling in cancer cells drives excessive ribosome biogenesis within the nucleolus, which elicits unbridled cell growth and proliferation. The rate-limiting step of ribosome biogenesis is synthesis of rRNA (building blocks of ribosomes) by RNA Polymerase I (Pol I). Numerous kinase pathways and products of proto-oncogenes can up-regulate Pol I, whereas tumor suppressor proteins can inhibit rRNA synthesis. In tumorigenesis, activating mutations in certain cancer-associated kinases and loss-of-function mutations in tumor suppressors lead to deregulated signaling that stimulates Pol I transcription with resultant increases in ribosome biogenesis, protein synthesis, cell growth, and proliferation. Certain anticancer therapeutics, such as cisplatin and 5-fluorouracil, reportedly exert, at least partially, their activity through disruption of ribosome biogenesis, yet many prime targets for anticancer drugs within the ribosome synthetic machinery of the nucleolus remain largely unexploited. Herein, we describe CX-3543, a small molecule nucleolus-targeting agent that selectively disrupts nucleolin/rDNA G-quadruplex complexes in the nucleolus, thereby inhibiting Pol I transcription and inducing apoptosis in cancer cells. CX-3543 is the first G-quadruplex interactive agent to enter human clinical trials, and it is currently under evaluation against carcinoid/neuroendocrine tumors in a phase II clinical trial.