Pharmacokinetic interaction between TMC114/ritonavir and tenofovir disoproxil fumarate in healthy volunteers

Limited Weight Impact After Switching From Boosted Protease Inhibitors to Dolutegravir in Persons With Human Immunodeficiency Virus With High Cardiovascular Risk: A Post Hoc Analysis of the 96-Week NEAT-022 Randomized Trial

BACKGROUND

In the NEAT022 trial, virologically suppressed persons with human immunodeficiency virus (HIV) at high cardiovascular risk switching from protease inhibitors to dolutegravir either immediately (DTG-I) or after 48 weeks (DTG-D) showed noninferior virological suppression and significant lipid and cardiovascular disease risk reductions on switching to dolutegravir relative to continuing protease inhibitors.

METHODS

In post hoc analysis, major endpoints were 48-week and 96-week weight and body mass index (BMI) changes. Factors associated with weight/BMI changes within the first 48 weeks of DTG exposure, proportion of participants by category of percentage weight change, proportions of BMI categories over time, and impact on metabolic outcomes were also assessed.

RESULTS

Between May 2014 and November 2015, 204 (DTG-I) and 208 (DTG-D) participants were included. Weight significantly increased (mean, +0.810 kg DTG-I arm, and +0.979 kg DTG-D arm) in the first 48 weeks postswitch, but remained stable from 48 to 96 weeks in DTG-I arm. Switching from darunavir, White race, total to high-density lipoprotein cholesterol ratio <3.7, and normal/underweight BMI were independently associated with higher weight/BMI gains. The proportion of participants with ≥5% weight change increased similarly in both arms over time. The proportions of BMI categories, use of lipid-lowering drugs, diabetes and/or use of antidiabetic agents, and hypertension and/or use of antihypertensive agents did not change within or between arms at 48 and 96 weeks.

CONCLUSIONS

Switching from protease inhibitors to dolutegravir in persons with HIV with high cardiovascular risk led to modest weight gain limited to the first 48 weeks, which involved preferentially normal-weight or underweight persons and was not associated with negative metabolic outcomes.

CLINICAL TRIALS REGISTRATION

NCT02098837 and EudraCT 2013-003704-39.

Tenofovir alafenamide vs. tenofovir disoproxil fumarate: an updated meta-analysis of 14 894 patients across 14 trials

BACKGROUND

Both tenofovir disoproxil fumarate (TDF)/emtricitabine and tenofovir alafenamide (TAF)/emtricitabine demonstrate excellent efficacy and safety overall, but concerns remain over specific changes in markers of bone and renal function. Lower plasma tenofovir concentrations are seen with TAF and in unboosted regimens. We assess TAF vs. TDF safety with and without booster coformulation.

METHODS

A previous systematic review was updated with recent clinical trials. TAF vs. TDF efficacy and safety were compared in boosted and unboosted subgroups. Efficacy was measured by viral suppression. Key safety endpoints included all adverse events, serious adverse events, Grades 3-4 adverse events and adverse event discontinuation. Further specific renal and bone markers were also assessed.

RESULTS

A total of 14 clinical trials comparing TDF and TAF regimens were identified. A significant difference (P = 0.0004) in efficacy was shown in the boosted subgroup in favour of TAF, but no difference was seen in the unboosted subgroup. There were no significant differences between TAF and TDF for any of the key safety endpoints analysed. No differences were seen for the bone markers analysed. No difference was found for renal tubular events. There was a difference in risk for discontinuation due to renal adverse events when boosted (P = 0.03), but none when unboosted.

CONCLUSION

Across all main safety endpoints, no differences between TAF and TDF are seen. Boosted TDF regimens were associated with lesser comparative efficacy than boosted TAF and a higher risk of renal event discontinuation. However, modern antiretroviral regimens are more commonly unboosted. This study finds no difference in efficacy or safety in unboosted TAF vs. TDF.

Effect of Pregnancy and Concomitant Antiretrovirals on the Pharmacokinetics of Tenofovir in Women With HIV Receiving Tenofovir Disoproxil Fumarate-Based Antiretroviral Therapy Versus Women With HBV Receiving Tenofovir Disoproxil Fumarate Monotherapy

Tenofovir disoproxil fumarate (TDF) is recommended as part of antiretroviral therapy (ART) for pregnant women with HIV and as monotherapy for pregnant women with hepatitis B virus (HBV) monoinfection at high risk of transmitting infection to their infants. Tenofovir (TFV) plasma exposures are reduced during pregnancy; however, concomitant antiretrovirals and the viral infection itself can also influence TFV pharmacokinetics. Our aim was to compare TFV pharmacokinetics in pregnant women receiving TDF‐based ART, with or without a ritonavir‐boosted protease inhibitor (r/PI), to pregnant women with HBV receiving TDF monotherapy. Non‐r/PI regimens were primarily integrase strand transfer inhibitors or nonnucleoside reverse transcriptase inhibitor–based regimens. Data were combined from a pharmacokinetic study of pregnant women with HIV on ART (PANNA), and a study assessing TFV pharmacokinetics in pregnant women with HBV (iTAP). A total of 196 pregnant women, 59 with HIV (32 receiving r/PIs) and 137 with HBV monoinfection were included. Intraindividual TFV area under the plasma concentration–time curve from time 0 to 24 hours was 25%, 26%, and 21% lower during the third trimester compared to 1 month postpartum in women with HIV using TDF and an r/PI or TDF and non‐r/PI and women with HBV receiving TDF monotherapy, respectively. TFV area under the plasma concentration–time curve from time 0 to 24 hours was similar in pregnant women receiving non‐r/PI to pregnant women with HBV receiving TDF monotherapy (1.84 vs 1.86 µg • h/mL); however, pregnant women receiving TDF with an r/PI had higher exposures (2.41 µg • h/mL; P < .01). Pregnancy reduces TFV exposure and the relative size was not impacted by concomitant antiretroviral drugs or viral infection, but a drug‐drug interaction between TDF and r/PI remains during pregnancy, leading to higher exposures than those on TDF and non‐r/PI or TDF monotherapy.

Drug-Drug Interaction Studies Between Hepatitis C Virus Antivirals Sofosbuvir/Velpatasvir and Boosted and Unboosted Human Immunodeficiency Virus Antiretroviral Regimens in Healthy Volunteers

Background

Combining antiviral regimens in the hepatitis C virus (HCV)/human immunodeficiency virus (HIV)-coinfected population can be complex as they share overlapping mechanisms for elimination that may result in drug interactions. The pharmacokinetics, safety, and tolerability of sofosbuvir/velpatasvir (SOF/VEL) with multiple antiretroviral (ARV) regimens were evaluated.

Methods

Healthy volunteers were enrolled into 2 phase 1, open-label, randomized, multiple-dose, cross-over studies. SOF/VEL and ARV regimens were administered alone and in combination; ARVs (and pharmacokinetic enhancers) included atazanavir (ATV), cobicistat (COBI), darunavir (DRV), dolutegravir (DTG), efavirenz (EFV), elvitegravir (EVG), emtricitabine (FTC), lopinavir (LPV), raltegravir (RAL), rilpivirine (RPV), ritonavir (RTV), tenofovir alafenamide (TAF), and tenofovir disoproxil fumarate (TDF). Geometric least squares means ratios (coadministration:alone) and 90% confidence intervals were constructed for area under the plasma concentration-time curve over the dosing interval, maximum concentration, and trough, for all analytes. Safety and tolerability were also evaluated.

Results

In total, 237 participants were enrolled. No clinically relevant differences in the pharmacokinetics (PK) of SOF, SOF metabolite GS-331007, or VEL were observed other than an approximate 50% decrease in VEL exposure when administered with EFV/FTC/TDF. No clinically relevant differences in the PK of ARVs were observed when administered with SOF/VEL. Study treatments were well tolerated, including no observed creatinine clearance changes during evaluation of TDF-containing regimens.

Conclusions

SOF/VEL and ARV regimens including ATV, COBI, DRV, DTG, EVG, FTC, LPV, RAL, RPV, RTV, TAF, or TDF may be coadministered without dose adjustment. Use of SOF/VEL with EFV-containing regimens is not recommended due to an approximate 50% reduction in VEL exposure.

Tenofovir Diphosphate in Dried Blood Spots Is Strongly Associated With Viral Suppression in Individuals With Human Immunodeficiency Virus Infections

BACKGROUND

Although tenofovir diphosphate (TFV-DP) in dried blood spots (DBS) is a predictor of adherence and pre-exposure prophylaxis efficacy, its utility in human immunodeficiency virus (HIV) treatment remains unknown.

METHODS

DBS for TFV-DP were collected up to 3 times over 48 weeks in persons living with HIV (PLWH) who were receiving TFV disoproxil fumarate (TDF)-based therapy. Log-transformed baseline TFV-DP was compared using t-tests or analyses of variance; generalized estimating equations were used to estimate the adjusted odds ratio (aOR) of viral suppression (<20 copies/mL) based on the TFV-DP concentration at the study visit.

RESULTS

We analyzed 1199 DBS from 532 participants (76 female; 101 Black, 101 Hispanic). Among the virologically-suppressed participants at baseline (n = 347), TFV-DP was lower in Blacks (geometric mean 1453, 95% confidence interval [CI] 1291-1635) vs Whites (1793, 95% CI 1678-1916; P = .002) and Hispanics (1760, 95% CI 1563-1982; P = .025); in non-boosted (1610, 95% CI 1505-1723) vs. boosted (1888, 95% CI 1749-2037; P = .002) regimens; and in non-nucleoside reverse transcription inhibitor-based (1563, 95% CI 1432-1707) vs. boosted protease inhibitor-based (1890, 95% CI 1704-2095; P = .006) and multiclass-based (1927, 95% CI 1650-2252; P = .022) regimens. The aOR of virologic suppression, after adjusting for age, gender, race, body mass index, estimated glomerular filtration rate, CD4+ T-cell count, antiretroviral drug class and duration of therapy, was 73.5 (95% CI 25.7-210.5; P < .0001) for a TFV-DP concentration ≥1850 fmol/punch compared to <350 fmol/punch.

CONCLUSIONS

TFV-DP in DBS is strongly associated with virologic suppression in PLWH on TDF-based therapy and is associated with certain participant characteristics. Further research is required to evaluate this drug adherence and exposure measure in clinical practice.

CLINICAL TRIALS REGISTRATION

NCT02012621.

Tenofovir alafenamide versus tenofovir disoproxil fumarate: is there a true difference in efficacy and safety?

BACKGROUND

Higher plasma tenofovir concentrations are associated with higher risks of renal and bone adverse events. The pharmacokinetic boosters ritonavir (RTV) and cobicistat (COBI) significantly increase plasma area under the curve (AUC) concentrations of tenofovir disoproxil fumarate (TDF), by 25-37%. When combined with RTV or COBI, the dose of tenofovir alafenamide (TAF) is lowered from 25 mg to 10 mg daily, but the TDF dose is maintained at 300 mg daily.

OBJECTIVE

To assess the differences in safety and efficacy between tenofovir alafenamide (TAF) and tenofovir disoproxil fumarate (TDF) in regimens with and without the pharmacokinetic boosters RTV and COBI.

METHODS

A PubMed/Embase search inclusive of dates up to 17 July 2017 identified 11 randomised head-to-head trials (8111 patients) of TDF versus TAF. The Mantel-Haenszel method was used to calculate pooled risk differences and 95% confidence intervals using random-effects models. A pre-defined sub-group analysis compared TAF with TDF, either when boosted with RTV or COBI, or when unboosted.

RESULTS

Nine clinical trials compared TAF and TDF for treatment of HIV-1 and two were for hepatitis B treatment. The eleven clinical trials documented 4574 patients with boosting RTV or COBI in both arms, covering 7198 patient-years of follow-up. Some 3537 patients received unboosted regimens, totalling 3595 patient-years of follow-up. Boosted TDF-treated patients showed borderline lower HIV RNA suppression <50 copies/mL (P=0.05), more bone fractures (P=0.04), larger decreases in bone mineral density (P<0.001), and more discontinuations for bone (P=0.03) or renal (P=0.002) adverse events. By contrast, there were no significant differences in HIV RNA suppression rates or clinical safety endpoints between unboosted TAF and unboosted TDF.

CONCLUSIONS

TDF boosted with RTV or COBI was associated with higher risks of bone and renal adverse events, and lower HIV RNA suppression rates, compared with TAF. By contrast, when ritonavir and cobicistat were not used, there were no efficacy differences between TAF and TDF, and marginal differences in safety. The health economic value of TAF versus low-cost generic TDF may be limited when these drugs are used without cobicistat or ritonavir.

Effect of Cobicistat on Tenofovir Disoproxil Fumarate (TDF): What Is True for TAF May Also Be True for TDF

BACKGROUND

The dose of tenofovir alafenamide is reduced from 25 to 10 mg daily when given with boosting agents. However, such dose reduction has never been adopted for tenofovir disoproxil fumarate (TDF). In this study, we aim to quantify the effect of cobicistat (COBI) both on tenofovir concentrations and TDF durability in real life setting.

METHODS

HIV-positive patients receiving TDF-containing antiretroviral therapies with at least 1 assessment of tenofovir plasma trough concentrations were included in the study. Univariate and multivariate regression analyses were performed considering tenofovir concentration as the dependent variable and clinical characteristics as independent covariates. Subsequently, survival and Cox analyses were performed considering as the primary outcome TDF discontinuation for any reasons.

RESULTS

Patients were given TDF with protease inhibitors/ritonavir (n = 212), non-nucleoside reverse transcriptase inhibitors (n = 176), integrase inhibitors (dolutegravir or raltegravir, n = 46), or with elvitegravir/COBI (ELV/COBI) (n = 76). By multivariate analysis, concomitant antiretroviral therapies resulted significantly associated with tenofovir levels, with the highest drug concentrations measured in patients given ELV/COBI. By survival analysis, we found that patients given TDF with ELV/COBI had the lowest rate of drug durability. Overall, these patients had a 2.3-fold increased risk to experience TDF discontinuation.

CONCLUSIONS

Coadministration with COBI resulted in significantly higher tenofovir concentrations and higher TDF discontinuation compared with other antiretroviral regimens. Accordingly, the possibility that the lack of proper dose adjustment for TDF when given with COBI might have biased the safety comparisons with tenofovir alafenamide during registrative trials cannot be ruled out.

Pharmacogenetics-based population pharmacokinetic analysis of tenofovir in Thai HIV-infected patients

AIM

To develop a population pharmacokinetic model and identify sources of variability, genetic and nongenetic factors, of tenofovir.

METHODS

The ABCC2 and ABCC4 polymorphisms were genotyped in 342 patients. A nonlinear mixed effects model was used to develop the population pharmacokinetic model and investigate the influence of these polymorphisms and other patient specific covariates on the pharmacokinetics of tenofovir.

RESULTS

The estimated glomerular filtration rate calculated by the Cockcroft and Gault equation, concomitant use of lopinavir/ritonavir and ABCC4 3463A>G polymorphism were associated with tenofovir apparent oral clearance (CL/F). The use of lopinavir/ritonavir decreased tenofovir CL/F by 25%. Patients carrying ABCC4 3463 AG or GG had a tenofovir CL/F 11% higher than those with genotype AA.

CONCLUSION

Renal function, co-medication and genetic variation impact the pharmacokinetics of tenofovir. These factors should be taken into consideration to guide the individual tenofovir disoproxil fumarate dosage regimen in Thai HIV-infected patients.

Pharmacokinetics and Safety of Tenofovir Alafenamide in HIV-Uninfected Subjects with Severe Renal Impairment

Tenofovir alafenamide (TAF) is an oral prodrug of tenofovir (TFV) that has greater stability in plasma than TFV disoproxil fumarate (TDF) and circulates as intact TAF, resulting in the direct and higher lymphatic loading of and exposure to TFV diphosphate, the active moiety. Unlike TFV, TAF is minimally eliminated in urine. The pharmacokinetics (PK) of TAF and TFV in HIV-uninfected subjects with severe renal impairment and matched healthy controls were evaluated. Subjects with severe renal impairment (RI; estimated glomerular filtration rate [eGFR], 15 to 29 ml/min) and controls (eGFR, ≥90 ml/min) matched for age, gender, and body mass index received a single dose of TAF at 25 mg. Blood and urine samples for TAF and TFV PK determinations were collected over 7 days postdosing, and subjects were followed up at 14 days. A total of 14 renally impaired subjects and 13 control subjects enrolled and completed the study. The TAF maximum observed concentration in plasma (Cmax) and the area under the concentration-versus-time curve (AUC) extrapolated to infinite time (AUCinf) were 79% and 92% higher, respectively, in subjects with severe RI than the controls, primarily due to higher absorption. The TFV Cmax and AUCinf were 2.8-fold and 5.7-fold higher, respectively, in subjects with severe RI than the controls. In subjects with severe RI, TAF at 25 mg provided a TFV AUC 10 to 40% lower than that from historical TDF-based TFV exposures in subjects with normal renal function. There were no discontinuations due to adverse events. In subjects with severe RI receiving TAF at 25 mg, TAF exposures were higher than those for the controls; these differences are unlikely to be clinically meaningful. TFV exposures were higher than those for the controls but lower than the exposures in nonrenally impaired subjects on TDF-based regimens.

Choice of antiretroviral drugs for continued treatment scale-up in a public health approach: what more do we need to know?

INTRODUCTION

There have been several important developments in antiretroviral treatment in the past two years. Randomized clinical trials have been conducted to evaluate a lower dose of efavirenz (400 mg once daily). Integrase inhibitors such as dolutegravir have been approved for first-line treatment. A new formulation of tenofovir (alafenamide) has been developed and has shown equivalent efficacy to tenofovir in randomized trials. Two-drug combination treatments have been evaluated in treatment-naïve and -experienced patients. The novel pharmacokinetic booster cobicistat has been compared to ritonavir in terms of pharmacokinetics, efficacy and safety. The objective of this commentary is to assess recent developments in antiretroviral drug treatment to determine whether new treatments should be included in new international guidelines.

DISCUSSION

The use of first-line treatment with tenofovir and efavirenz at the standard 600 mg once-daily dose should remain the first-choice standard of care treatment. Evidence supporting a switch to efavirenz 400 mg once daily or integrase inhibitors is sufficient to consider these drugs as alternative first-line options, but more data are needed on their use in pregnant women and people with TB co-infection. The use of new formulations of tenofovir is currently too preliminary to justify immediate adoption and scale-up across HIV programmes in low- and middle-income countries. The evidence supporting use of two-drug combinations is not considered strong enough to justify changed recommendations from use of standard triple drug combinations. Cobicistat does not offer significant safety advantages over ritonavir as a pharmacokinetic booster.

CONCLUSIONS

For continued scale-up of antiretroviral treatment in low- and middle-income countries, use of first-line triple combinations including efavirenz 600 mg once daily is supported by the largest evidence base. Additional studies are underway to evaluate new treatments in key populations, and these results may justify changes to these recommendations.

Less Bone Loss With Maraviroc- Versus Tenofovir-Containing Antiretroviral Therapy in the AIDS Clinical Trials Group A5303 Study

BACKGROUND

There is a need to prevent or minimize bone loss associated with antiretroviral treatment (ART) initiation. We compared maraviroc (MVC)- to tenofovir disoproxil fumarate (TDF)-containing ART.

METHODS

This was a double-blind, placebo-controlled trial. ART-naive subjects with human immunodeficiency virus type 1 RNA load (viral load [VL]) >1000 copies/mL and R5 tropism were randomized to MVC 150 mg or TDF 300 mg once daily (1:1), stratified by VL <100 000 or ≥100 000 copies/mL and age <30 or ≥30 years. All subjects received darunavir 800 mg, ritonavir 100 mg, and emtricitabine 200 mg daily. Dual-energy X-ray absorptiometry scanning was done at baseline and week 48. The primary endpoint was percentage change in total hip bone mineral density (BMD) from baseline to week 48 in the as-treated population.

RESULTS

We enrolled 262 subjects. A total of 259 subjects (130 MVC, 129 TDF) contributed to the analyses (91% male; median age, 33 years; 45% white, 30% black, 22% Hispanic). Baseline median VL was 4.5 log10 copies/mL and CD4 count was 390 cells/µL. The decline in hip BMD (n = 115 for MVC, n = 109 for TDF) at week 48 was less with MVC (median [Q1, Q3] of -1.51% [-2.93%, -0.11%] vs -2.40% [-4.30%, -1.32%] for TDF (P < .001). Lumbar spine BMD decline was also less with MVC (median -0.88% vs -2.35%; P < .001). Similar proportions of subjects in both arms achieved VL ≤50 copies/mL in as-treated and ITT analyses.

CONCLUSIONS

MVC was associated with less bone loss at the hip and lumbar spine compared with TDF. MVC may be an option to attenuate ART-associated bone loss.

CLINICAL TRIALS REGISTRATION

NCT01400412.

Cobicistat-boosted darunavir in HIV-1-infected adults: week 48 results of a Phase IIIb, open-label single-arm trial

Background

Cobicistat is an alternative pharmacoenhancer to ritonavir. In healthy volunteers, darunavir exposure was comparable when darunavir 800 mg once daily was co-administered with cobicistat 150 mg once daily (as single agents or a fixed-dose combination) vs. with ritonavir 100 mg once daily.

Methods

This 48-week, Phase IIIb, single-arm, US multicenter study (NCT01440569) evaluated safety, efficacy and pharmacokinetics of darunavir/cobicistat 800/150 mg once daily (as single agents) plus two investigator-selected nucleoside/tide reverse transcriptase inhibitors (N[t]RTIs) in HIV-1-infected adults. Patients had no darunavir resistance-associated mutations (RAMs), plasma viral load (VL) ≥1000 HIV-1 RNA copies/ml, eGFR ≥80 ml/min and genotypic sensitivity to the two N[t]RTIs. The primary endpoint was any treatment-emergent grade 3 or 4 adverse events (AEs) through Week 24.

Results

The majority of the 313 intent-to-treat patients were treatment-naïve (295/313; 94%), male (89%), White (60%) and received a tenofovir-based regimen (99%). Median baseline VL and CD4⁺ count overall were 4.8 log₁₀ HIV-1 RNA copies/ml and 361 cells/mm³, respectively. Overall, 86% of patients (268/313) completed the study. The majority of discontinuations were for AEs (15/313; 5%). The incidence of treatment-emergent grade 3 or 4 AEs regardless of causality was 6% through Week 24 and 8% through Week 48. Most common AEs through Week 48 were diarrhea (27%) and nausea (23%), which were grade 1 or 2 in severity. Week 48 virologic response rates (% with VL <50 HIV-1 RNA copies/ml; Snapshot analysis) were 81% overall and 83% in treatment-naïve patients; median increases in CD4⁺ count at 48 weeks were 167 and 169 cells/mm³, respectively. Of 15/313 patients who met the criteria for resistance analysis, one developed a darunavir RAM as a mixture with wild-type (I84I/V), without phenotypic resistance to darunavir. The mean population pharmacokinetic-derived darunavir areas under the plasma concentration–time curve were 102,000 overall and 100,620 ng•h/ml in treatment-naïve patients. No clinically relevant relationships were seen between darunavir exposure and virologic response, AEs or laboratory parameters.

Conclusion

Darunavir/cobicistat 800/150 mg once daily was generally well tolerated through Week 48, with no new safety concerns. Pharmacokinetics, virologic and immunologic responses for darunavir/cobicistat were similar to previous data for darunavir/ritonavir 800/100 mg once daily.

Pharmacokinetics and pharmacodynamics of boosted once-daily darunavir

The ability to dose antiretroviral agents once daily simplifies the often complex therapeutic regimens required for the successful treatment of HIV infection. Thus, once-daily dosing can lead to improved patient adherence to medication and, consequently, sustained virological suppression and reduction in the risk of emergence of drug resistance. Several trials have evaluated once-daily darunavir/ritonavir in combination with other antiretrovirals (ARTEMIS and ODIN trials) or as monotherapy (MONET, MONOI and PROTEA trials) in HIV-1-infected adults. Data from ARTEMIS and ODIN demonstrate non-inferiority of once-daily darunavir/ritonavir against a comparator and, together with pharmacokinetic data, have established the suitability of once-daily darunavir/ritonavir for treatment-naive and treatment-experienced patients with no darunavir resistance-associated mutations. The findings of ARTEMIS and ODIN have led to recent updates to treatment guidelines, whereby once-daily darunavir/ritonavir, given with other antiretrovirals, is now a preferred treatment option for antiretroviral-naive adult patients and a simplified treatment option for antiretroviral-experienced adults who have no darunavir resistance-associated mutations. Once-daily dosing with darunavir/ritonavir is an option for treatment-naive and for treatment-experienced paediatric patients with no darunavir resistance-associated mutations based on the findings of the DIONE trial and ARIEL substudy. This article reviews the pharmacokinetics, efficacy, safety and tolerability of once-daily boosted darunavir. The feasibility of darunavir/ritonavir monotherapy as a treatment approach for some patients is also discussed. Finally, data on a fixed-dose combination of 800/150 mg of darunavir/cobicistat once daily are presented, showing comparable darunavir bioavailability to that obtained with 800/100 mg of darunavir/ritonavir once daily.

Effects of a protein-rich drink or a standard meal on the pharmacokinetics of elvitegravir, cobicistat, emtricitabine and tenofovir in healthy Japanese male subjects: a randomized, three-way crossover study

This study investigated the effects of ingested food types on the pharmacokinetics of elvitegravir, cobicistat, emtricitabine, and tenofovir as a single-tablet regimen (STR) in Japanese HIV-negative healthy subjects. In this open-label, randomized, three-way crossover study, the pharmacokinetic profiles of elvitegravir, cobicistat, emtricitabine, and tenofovir were evaluated when administered with a standard breakfast, under fasting conditions, or with a nutritional protein-rich drink. All subjects (N = 11) received a single morning dose of elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (150/150/200/300 mg). Administration under fasting conditions resulted in decreases in the mean AUCinf of elvitegravir and tenofovir by 50% and 28%, respectively, relative to administration with a standard breakfast, whereas the bioavailabilities of elvitegravir and tenofovir were comparable when administered with a standard breakfast or a nutritional protein-rich drink. Under fasting conditions, it appears that the bioavailabilities of elvitegravir and tenofovir were not equivalent to those when they were administered with either type of food, although they were bioequivalent to each other under fed conditions. Cobicistat and emtricitabine were bioequivalent under all conditions. These findings suggest that elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate should be administered with food, and that the bioavailability of elvitegravir and tenofovir is not affected by the type of meal ingested.

Pharmacokinetic study of dual therapy with raltegravir 400 mg twice daily and Darunavir/Ritonavir 800/100 mg once daily in HIV-1-infected patients

BACKGROUND

Combinations of new classes of antiretroviral drugs are attractive options to avoid toxicity associated with nucleoside reverse transcriptase inhibitors (NRTIs) and to provide a full active regimen in patients with some degree of resistance to NRTIs. However, data on the pharmacokinetic (PK) profiles of these regimens are limited. We explore the plasma PK profile of raltegravir (RAL) at a dose of 400 mg twice a day plus darunavir/ritonavir (DRV/RTV) at a dose of 800/100 mg once a day in HIV-1-infected patients.

METHODS

This was a pilot, open-label, fixed-sequence, prospective, single-center single-arm PK study. The treating physician chose an NRTI-sparing regimen because of toxicity or resistance mutations to NRTIs, which included DRV/RTV 800/100 mg once daily plus RAL 400 mg twice daily. All patients were RAL and DRV naive and had no evidence of protease inhibitor mutations. After at least 15 days on therapy, patients were admitted for a 24-hour PK study. Laboratory tests to assess efficacy and safety were performed at all study visits.

RESULTS

Fifteen patients were included. The geometric mean values for DRV were AUC0-24 68,730 ng·h·mL [95% confidence interval (CI): 58,970-86,480], Ctrough 1330 ng/mL (95% CI: 1110-1760; IC-50 for wild-type and resistant HIV-1 strains was 55 and 550 ng/mL, respectively), Cmax 7630 ng/mL (95% CI: 6740-9000), and t1/2 10.9 hours (95% CI: 9.20-13.99). Geometric mean values for RAL were AUC0-12 3050 ng·h·mL (95% CI: 2530-5180); Ctrough 40 ng/mL (95% CI: 30-80), Cmax 970 ng/mL (95% CI: 840-2270), t1/2 2.68 hours (95% CI: 1.97-4.40). No adverse effects including rash or laboratory test abnormalities were noted. At week 24, the HIV-1 viral load was below 37 copies/mL in all patients.

CONCLUSIONS

Our data suggest that dual therapy with RAL 400 mg twice daily plus DRV/RTV 800/100 mg once daily had a favorable PK profile for both drugs and that short-term efficacy and tolerability of this combination were adequate.

Review and management of drug interactions with boceprevir and telaprevir

Boceprevir (BOC) and telaprevir (TPV), when added to pegylated interferon and ribavirin for the treatment of chronic hepatitis C virus (HCV) infection, increase the rates of sustained virologic response in treatment-naïve persons to approximately 70%. Though these agents represent an important advance in the treatment of chronic HCV, they present new treatment challenges to the hepatology community. BOC and TPV are both substrates and inhibitors of the hepatic enzyme, cytochrome P450 3A, and the drug transporter, P-glycoprotein, which predisposes these agents to many drug interactions. Identification and appropriate management of potential drug interactions with TPV and BOC is critical for optimizing therapeutic outcomes during hepatitis C treatment. This review highlights the pharmacologic characteristics and drug-interaction potential of BOC and TPV and provides guidance on the management of drug interactions with these agents.

Formulation, pharmacokinetics and pharmacodynamics of topical microbicides

The development of safe topical microbicides that effectively prevent human immunodeficiency virus (HIV) infection is a major goal in curbing the human immunodeficiency virus pandemic. A number of past failures resulting from mucosal toxicity or lack of efficacy have informed the field. Products that caused toxicity to the female genital tract mucosa, and thereby increased the likelihood of HIV acquisition, included nonoxynol 9, cellulose sulfate, and C31 G vaginal gel Savvy. Topical products that were ineffective in preventing HIV infection include BufferGel, Carraguard, and PRO 2000. Antiretroviral drugs such as tenofovir and dapivirine formulated into microbicide products have shown promise, but there is much to learn about ideal product formulation and acceptability, and drug distribution and disposition (pharmacokinetics). Current formulations for water-soluble molecules include vaginally or rectally applied gels, vaginal rings, films and tablets. Dosing strategies (e.g. coitally dependent or independent) will be based on the pharmacokinetics of the active ingredient and the tolerance for less than perfect adherence.

A multi-compartment, single and multiple dose pharmacokinetic study of the vaginal candidate microbicide 1% tenofovir gel

Background

Tenofovir (TFV) gel is being evaluated as a microbicide with pericoital and daily regimens. To inhibit viral replication locally, an adequate concentration in the genital tract is critical.

Methods and Findings

Forty-nine participants entered a two-phase study: single-dose (SD) and multi-dose (MD), were randomized to collection of genital tract samples (endocervical cells [ECC], cervicovaginal aspirate and vaginal biopsies) at one of seven time points [0.5, 1, 2, 4, 6, 8, or 24 hr(s)] post-dose following SD exposure of 4 mL 1% TFV gel and received a single dose. Forty-seven were randomized to once (QD) or twice daily (BID) dosing for 2 weeks and to collection of genital tract samples at 4, 8 or 24 hrs after the final dose, but two discontinued prior to gel application. Blood was collected during both phases at the seven times post-dose. TFV exposure was low in blood plasma for SD and MD; median C_max was 4.0 and 3.4 ng/mL, respectively (C≤29 ng/mL). TFV concentrations were high in aspirates and tissue after SD and MD, ranging from 1.2×10⁴ to 9.9×10⁶ ng/mL and 2.1×10² to 1.4×10⁶ ng/mL, respectively, and did not noticeably differ between proximal and distal tissue. TFV diphosphate (TFV-DP), the intracellular active metabolite, was high in ECC, ranging from 7.1×10³ to 8.8×10⁶ ng/mL. TFV-DP was detectable in approximately 40% of the tissue samples, ranging from 1.8×10² to 3.5×10⁴ ng/mL. AUC for tissue TFV-DP was two logs higher after MD compared to SD, with no noticeable differences when comparing QD and BID.

Conclusions

Single-dose and multiple-dose TFV gel exposure resulted in high genital tract concentrations for at least 24 hours post-dose with minimal systemic absorption. These results support further study of TFV gel for HIV prevention.

Trial registration

ClinicalTrials.gov NCT00561496

Steady-state pharmacokinetics of tenofovir-based regimens in HIV-infected pediatric patients

HIV-infected children are treated with tenofovir in combination with other, potentially interacting, antiretroviral agents. We report the pharmacokinetic parameters of tenofovir in combination with efavirenz, darunavir-ritonavir, or atazanavir-ritonavir in HIV-infected children. HIV-infected patients 8 to 18 years of age receiving a tenofovir (300 mg)-based regimen containing efavirenz (300 or 600 mg) once daily (group 1), darunavir (300 or 600 mg)-ritonavir (100 mg) twice daily (group 2), or atazanavir (150 to 400 mg)-ritonavir (100 mg) once daily (group 3) were enrolled. Plasma samples were collected over a 24-h time interval. The 90% confidence intervals (90% CI) of the geometric means for the area under the plasma concentration-time curve (AUC) and the minimum concentration of drug in serum (C(min)) of each antiretroviral were computed and checked for overlap with intervals bracketing published values obtained in adult or pediatric studies demonstrating safety and/or efficacy. Group 1 efavirenz plasma concentrations were observed to be higher in patients receiving fixed-dose combination tablets compared with subjects receiving the individual formulation. In group 2, tenofovir and darunavir exposure was observed to be lower than expected. In group 3, tenofovir and atazanavir administered concomitantly produced exposures similar to those published for adult patients. The 90% CI of AUC and C(min) for tenofovir overlapped the target range for all combinations. Informal comparisons of treatment groups did not indicate any advantage to any combination with respect to tenofovir exposure. Further study of exposures achieved with antiretrovirals administered in combination is warranted.

Pharmacokinetics of darunavir/ritonavir and rifabutin coadministered in HIV-negative healthy volunteers

The drug-drug interaction between rifabutin (RFB) and darunavir/ritonavir (DRV/r) was examined in a randomized, three-way crossover study of HIV-negative healthy volunteers who received DRV/r 600/100 mg twice a day (BID) (treatment A), RFB 300 mg once a day (QD) (treatment B), and DRV/r 600/100 mg BID plus RFB 150 mg every other day (QOD) (treatment C). The sequence of treatments was randomized, and each treatment period lasted 12 days. Full pharmacokinetic profiles were determined for DRV, ritonavir, and RFB and its active metabolite, 25-O-desacetylrifabutin (desRFB), on day 13. The DRV and ritonavir areas under the plasma concentration-time curve from zero to 12 h (AUC(12h)) increased by 57% and 66%, respectively, in the presence of RFB. The RFB exposure was comparable between treatment with RFB QD alone (treatment B) and treatment with DRV/r plus RFB QOD (treatment C); however, based on least-square means ratios, the minimum plasma concentration (C(min)) increased by 64% and the maximum plasma concentration (C(max)) decreased by 28%, respectively. The exposure (AUC within the dosage interval and at steady state [AUC(τ)]) to desRFB was considerably increased (by 881%) following treatment with DRV/r/RFB. The exposure to the parent drug plus the metabolite increased 1.6-fold in the presence of DRV/r. Adverse events (AEs) were more commonly reported during combined treatment (83% versus 44% for RFB and 28% for DRV/r); similarly, grade 3-4 AEs occurred in 17% versus 11% and 0%, respectively, of volunteers. Eighteen of 27 volunteers (66.7%) prematurely discontinued the trial; all volunteers discontinuing for safety reasons (n = 9) did so during RFB treatment phases. These results suggest that DRV/r may be coadministered with RFB with a dose adjustment of RFB to 150 mg QOD and increased monitoring for RFB-related AEs. Based on the overall safety profile of DRV/r, no dose adjustment of DRV/r is considered to be warranted. Given the safety profile seen with the combination of RFB with a boosted protease inhibitor in this and other studies, it is not recommended to conduct further studies with this combination in healthy volunteers.

[AIDS Study Group/Spanish AIDS Plan consensus document on antiretroviral therapy in adults with human immunodeficiency virus infection (updated January 2010)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy recommendations for adult patients with human immunodeficiency virus infection.

METHODS

To formulate these recommendations a panel made up of members of the Grupo de Estudio de Sida (Gesida, AIDS Study Group) and the Plan Nacional sobre el Sida (PNS, Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of human immunodeficiency virus (HIV) infection, the efficacy and safety of clinical trials, and cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings. Three levels of evidence were defined according to the data source: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not to recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r), but other combinations are possible. Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts below 350 cells/microl; 2) When CD4 counts are between 350 and 500 cells/microl, therapy should be started in case of cirrhosis, chronic hepatitis C, high cardiovascular risk, HIV nephropathy, HIV viral load above 100,000 copies/ml, proportion of CD4 cells under 14%, and in people aged over 55; 3) Therapy should be deferred when CD4 are above 500 cells/microl, but could be considered if any of previous considerations concurs. Treatment should be initiated in case of hepatitis B requiring treatment and should be considered for reduce sexual transmission. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures but undetectable viral loads maybe possible with the new drugs even in highly drug experienced patients. Genotype studies are useful in these situations. Drug toxicity of ART therapy is losing importance as benefits exceed adverse effects. Criteria for antiretroviral treatment in acute infection, pregnancy and post-exposure prophylaxis are mentioned as well as the management of HIV co-infection with hepatitis B or C.

CONCLUSIONS

CD4 cells counts, viral load and patient co-morbidities are the most important reference factors to consider when initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized therapy approach in order to achieve undetectable viral load under any circumstances.

Darunavir: in treatment-experienced pediatric patients with HIV-1 infection

Darunavir is a nonpeptidic HIV type 1 (HIV-1) protease inhibitor (PI) that binds with high affinity to the HIV-1 protease, including multi-drug resistant proteases. This drug is highly potent against a range of laboratory strains and clinical isolates of wild-type and multidrug-resistant HIV and has limited potential to cause cytotoxicity. Darunavir did not display cross-resistance with other PIs in vitro. The coadministration of a low boosting dose of ritonavir with darunavir (boosted darunavir) increases the bioavailablity of darunavir. The drug is also administered together with other highly active antiretroviral agents. The efficacy of twice-daily boosted darunavir (11-19 mg/kg plus ritonavir 1.5-2.5 mg/kg) in treatment-experienced pediatric patients (aged 6-17 years and weighing > or =20 kg; n = 80) was demonstrated in the phase II DELPHI trial, where a virologic response (HIV-1 RNA reduction from baseline of > or =1 log(10) copies/mL) at week 24 (primary endpoint) was achieved in 74% of patients, and 88% of these patients sustained this level of response at week 48. Boosted darunavir was generally well tolerated in the DELPHI trial, with a similar profile to that observed in adults. The mean triglyceride level at week 48 was lower than that at baseline, and cholesterol levels increased slightly but remained within the normal range.

Single-dose safety, pharmacokinetics, and food effects studies of compound naphthoquine phosphate tablets in healthy volunteers

The compound naphthoquine phosphate is a novel antimalaria drug tablet containing a fixed-dose combination of naphthoquine phosphate and artemisinin in a 1:2.5 ratio. A randomized, open study on the safety and tolerability was conducted in 28 healthy male volunteers using a single oral dose of 350 mg, 700 mg, 1400 mg, or 2100 mg of artemisinin-naphthoquine phosphate. Pharmacokinetics at the last 3 doses were examined in 30 volunteers. Food effects were also determined. Serial blood samples up to 216 hours after single oral dose administration were analyzed for plasma concentrations using a validated high-performance liquid chromatography-tandem mass spectrometry assay. The compound was well tolerated at single doses up to 2100 mg. Increased exposure to naphthoquine phosphate and artemisinin was less than dose proportional and linear. The half-life of naphthoquine phosphate was approximately 255 hours. The combination increased the AUC(0-t) and C(max) of both artemisinin (by 71% and 49%) and naphthoquine phosphate (by 135% and 104%) compared with monotherapy. Food intake greatly increased the AUC(0-t) of artemisinin with a ratio of 77% and reduced that of naphthoquine phosphate from 955 ± 352 µg·h/L under the fasted state to 446 ± 231 µg·h/L in the fed condition. The pharmacokinetics and safety profile of the drug support its continued investigation in future clinical studies.

Pharmacologic characteristics of investigational and recently approved agents for the treatment of HIV

PURPOSE OF REVIEW

Two agents from antiretroviral classes with novel mechanisms of action against HIV received regulatory approval in 2007. Maraviroc is the first in the class of chemokine coreceptor 5 antagonists and raltegravir is the first in the class of integrase inhibitors. There are other compounds in these two new classes in later stages of clinical development, as well as several protease inhibitors and nonnucleoside reverse transcriptase inhibitors that have been recently approved or are under investigation for use in treatment-experienced patients. The purpose of this article is to review the pharmacologic characteristics of these newly approved and investigational antiretroviral drugs, with particular emphasis on data presented or published within the past year.

RECENT FINDINGS

Several pivotal studies describing the efficacy, safety, and pharmacologic properties of maraviroc, vicriviroc, etravirine, rilpivirine, raltegravir, elvitegravir, darunavir/ritonavir, and tipranavir/ritonavir have begun to emerge.

SUMMARY

To date, these agents have demonstrated promising virologic activity with primarily excellent tolerability, but there is still much to learn about their pharmacology. Future studies should evaluate their potential for drug-drug interactions and elucidate their concentration-effect relationships. An appreciation for the pharmacology of these drugs is critical to their optimal use.

Steady-state amprenavir and tenofovir pharmacokinetics after coadministration of unboosted or ritonavir-boosted fosamprenavir with tenofovir disoproxil fumarate in healthy volunteers

Objective An open-label, three-period pharmacokinetic study was conducted to investigate the drug interaction potential between fosamprenavir (FPV) and tenofovir disoproxil fumarate (TDF). Methods Thirty-six healthy subjects received TDF 300 mg once daily (qd) for 7 days (period 1), and then were randomized to 14 days of either FPV 1400 mg twice daily (bid) or FPV/ritonavir (RTV) 700/100 mg bid alone or with TDF (period 2). Subjects continued their randomized dose of FPV for 14 more days, adding or removing TDF based upon its receipt in period 2 (period 3). Twenty-four-hour pharmacokinetic sampling was carried out on day 7 of period 1 and on day 14 of periods 2 and 3. Steady-state plasma amprenavir (APV) and tenofovir (TFV) pharmacokinetics were assessed by noncompartmental analysis and parameter values observed with each regimen were compared using geometric mean ratios with 90% confidence intervals. Results After TDF coadministration, APV geometric mean minimum concentration (C(min)), maximum concentration (C(max)), and area under the plasma concentration-time curve (AUC) increased by 31, 3 and 7% above values observed with unboosted FPV alone; they also increased by 31, 4 and 16% above values observed with FPV/RTV alone. TFV C(min), C(max) and AUC decreased by 12, 25 and 15% after FPV coadministration and by 9, 18 and 7% after FPV/RTV coadministration. No significant changes in RTV pharmacokinetics were observed. No differences were noted in adverse events among dosing periods. Conclusions In this evaluation of the interaction between FPV and TDF, increases in APV exposures and modest decreases in TFV exposures were observed. These were unlikely to be clinically significant.

Pharmacokinetics and drug-drug interactions of antiretrovirals: an update

Current antiretroviral treatment has allowed HIV infection to become a chronic manageable condition with many HIV patients living longer. However, available antiretrovirals are not without limitations, for example the development of resistance and adverse effects. Consequently, new drugs in existing and novel classes are urgently required to provide viable treatment options to patients with few remaining choices. Darunavir, etravirine, maraviroc and raltegravir have been recently approved for treatment-experienced patients and other agents such as rilpivirine, vicriviroc and elvitegravir are currently under phase III study. Clinical studies are necessary to optimise potential treatment combinations and to manage drug-drug interactions to help avoid toxicity or therapy failure. This review aims to summarise the pharmacokinetics and key drug-drug interaction studies for newly available antiretrovirals and those in development. Further information regarding drug-drug interactions of well established antiretrovirals and those recently approved are readily available online at sites such as http://www.hiv-druginteractions.org, http://www.clinicaloptions.com/hiv, http://hivinsite.ucsf.edu. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of antiretroviral drug discovery and development, Vol 85, issue 1, 2010.

[Pharmacological interactions with darunavir]

Darunavir is a new HIV protease inhibitor that has been shown to be highly useful in HIV-infected patients. This drug is primarily metabolized by the liver through the cytochrome P450 3A4 (CYP3A4) isozyme and consequently coadministration with low doses of ritonavir markedly increases exposure and allows both daily doses and pill burden to be reduced. Both darunavir and ritonavir act as inhibitors and substrates of CYP3A4 and may therefore present pharmacological interactions with a large number of drugs commonly used in HIV-infected patients. The present review aims to summarize the main studies that have evaluated drug interactions and to provide recommendations on treatment with darunavir/ritonavir in clinical practice.

Drug interactions with new and investigational antiretrovirals

More than 20 individual and fixed-dose combinations of antiretrovirals are approved for the treatment of human immunodeficiency virus (HIV) infection. However, owing to the ongoing limitations of drug resistance and adverse effects, new treatment options are still required. A number of promising new agents in existing or new drug classes are in development or have recently been approved by the US FDA. Since these agents will be used in combination with other new and existing antiretrovirals, understanding the potential for drug interactions between these compounds is critical to their appropriate use. This article summarizes the drug interaction potential of new and investigational protease inhibitors (darunavir), non-nucleoside reverse transcriptase inhibitors (etravirine and rilpivirine), chemokine receptor antagonists (maraviroc, vicriviroc and INCB 9471), integrase inhibitors (raltegravir and elvitegravir) and maturation inhibitors (bevirimat).

Darunavir: Pharmacokinetics and Drug Interactions

Darunavir (TMC114) is a new HIV protease inhibitor that has demonstrated substantial antiretroviral activity against wild-type HIV-1 virus and multidrug-resistant strains. Darunavir inhibits and is primarily metabolized by cytochrome P450 3A (CYP3A) isoenzymes and is coadministered with low-dose ritonavir (darunavir/r); ritonavir is an inhibitor of CYP3A isoenzymes and pharmacologically enhances darunavir, resulting in increased plasma concentrations and allowing for a lower daily dose. The t1/2 (terminal elimination half-life) of darunavir is 15 h in the presence of ritonavir. An extensive darunavir/r drug-drug interaction programme has been undertaken, covering a wide range of therapeutic areas. Studies conducted in HIV-negative healthy volunteers and in HIV-infected patients show that the potential for interactions is well characterized and the interactions are manageable. For most drugs investigated, no dose adjustments of darunavir/r or the co-administered drug are required. This article reviews all the pharmacokinetic and drug-drug interaction studies conducted to date for darunavir/r, providing guidance on how to co-administer darunavir/r with many other antiretroviral or non-antiretroviral medications commonly used in HIV-infected individuals.

Review of tenofovir-emtricitabine

Highly active antiretroviral therapy has significantly reduced HIV-related morbidity and mortality. Increasingly, fixed-dose antiretroviral combinations with equal or greater potency than traditional antiretrovirals, along with fewer side effects, reduced toxicity, and simplified dosing convenience are being utilized. Tenofovir-emtricitabine (TDF-FTC) represents one of the more recent fixed-dose combinations. In combination with either a ritonavir-boosted protease inhibitor or a non-nucleoside reverse transcriptase inhibitor, TDF-FTC is a preferred choice in recent treatment guidelines on the basis of demonstrated potency in randomized clinical trials, one-pill-a-day dosing convenience, and relatively low toxicity. In addition, the drug is active against hepatitis B virus. Caution must be exercised in patients with renal insufficiency, or when the drug is used with certain other drugs. This manuscript reviews the use of TDF-FTC in the treatment of HIV.