Cell disposition of raltegravir and newer antiretrovirals in HIV-infected patients: high inter-individual variability in raltegravir cellular penetration

Real-Life Therapeutic Concentration Monitoring of Long-Acting Cabotegravir and Rilpivirine: Preliminary Results of an Ongoing Prospective Observational Study in Switzerland

SHCS#879 is an ongoing Switzerland-wide multicenter observational study conducted within the Swiss HIV Cohort Study (SHCS) for the prospective follow-up of people living with HIV (PLWH) receiving long-acting injectable cabotegravir-rilpivirine (LAI-CAB/RPV). All adults under LAI-CAB/RPV and part of SHCS are enrolled in the project. The study addresses an integrated strategy of treatment monitoring outside the stringent frame of controlled clinical trials, based on relevant patient characteristics, clinical factors, potential drug-drug interactions, and measurement of circulating blood concentrations. So far, 91 blood samples from 46 PLWH have been collected. Most individuals are less than 50 years old, with relatively few comorbidities and comedications. The observed concentrations are globally in accordance with the available values reported in the randomized clinical trials. Yet, low RPV concentrations not exceeding twice the reported protein-adjusted 90% inhibitory concentration have been observed. Data available at present confirm a considerable between-patient variability overall. Based on the growing amount of PK data accumulated during this ongoing study, population pharmacokinetic analysis will characterize individual concentration-time profiles of LAI-CAB/RPV along with their variability in a real-life setting and their association with treatment response and tolerability, thus bringing key data for therapeutic monitoring and precision dosage adjustment of this novel long-acting therapy.

Raltegravir Inclusion Decreases CD4 T-Cells Intra-Cellular Viral Load and Increases CD4 and CD28 Positive T-Cells in Selected HIV Patients

Raltegravir (RLT) prevents the integration of HIV DNA in the nucleus, but published studies remain controversial, suggesting that it does not decrease proviral DNA. However, there are only a few studies focused on virus-targeted cells. We aimed our study on the impact of RLT inclusion on total intra-cellular viral DNA (TID) in cellular subsets and immune effects in patients with newly acquired undetectable plasmatic viral load (UVL). Six patients having UVL using an antiretroviral combination for 6 months and CD4 T-cells > 350/mL and <500/mL were selected to receive RLT for 3 months from M0 to M3. Patients had 7 sequential viro-immunological determinations from M-1 to M5. Immune phenotypes were determined by flow cytometry and TID quantification was performed using PCR assay on purified cells. TID (median values) at the initiation of RLT in CD4 T-cells was 117 copies/millions of cells, decreased to 27.5 on M3, and remained thereafter permanently under the cut-off (<10 copies/millions of cells) in 4 out of 6 patients. This was associated with an increase of CD4 and CD4 + CD28+ T-cells and a decrease of HLA-DR expression and apoptosis of CD4 T-cells. RLT inclusion led to decreases in the viral load along with positive immune reconstitution, mainly for CD4 T-cells in HIV patients.

An Integrated Spatial Dynamics-Pharmacokinetic Model Explaining Poor Penetration of Anti-retroviral Drugs in Lymph Nodes

Although combined anti-retroviral therapy (cART) suppresses plasma HIV viremia below the limit of detection in a majority of HIV patients, evidence is emerging that the distribution of the anti-retroviral drugs is heterogeneous in tissue. Clinical studies measuring antiretroviral drug concentrations in lymph nodes (LNs) revealed lower concentrations compared to peripheral blood levels suggesting poor drug penetration properties. Our current study is an attempt to understand this poor anti-retroviral drug penetration inside lymph node lobules through integrating known pharmacokinetic and pharmacodynamic (PK/PD) parameters of the anti-retroviral drugs into a spatial model of reaction and transport dynamics within a solid lymph node lobule. Simulated drug penetration values were compared against experimental results whenever available or matched with data that is available for other drugs in a similar class. Our integrated spatial dynamics pharmacokinetic model reproduced the experimentally observed exclusion of antivirals from lymphoid sites. The strongest predictor of drug exclusion from the lymphoid lobule, independent of drug class, was lobule size; large lobules (high inflammation) exhibited high levels of drug exclusion. PK/PD characteristics associated with poor lymphoid penetration include high cellular uptake rates and low intracellular half-lives. To determine whether this exclusion might lead to ongoing replication, target CD4+ T cell, infected CD4+ T cell, free virus, and intracellular IC50 values of anti-retroviral drugs were incorporated into the model. Notably, for median estimates of PK/PD parameters and lobule diameters consistent with low to moderate inflammation, the model predicts no ongoing viral replication, despite substantial exclusion of the drugs from the lymphoid site. Monte-Carlo studies drawn from the prior distributions of the PK/PD parameters predicts increases in site-specific HIV replication in a small fraction of the patient population for lobule diameters greater than 0.2 mm; this fraction increases as the site diameter/ inflammation level increases. The model shows that cART consisting of two nRTIs and one PI is the most likely treatment combination to support formation of a sanctuary site, a finding that is consistent with clinical observations.

Alterations in cellular pharmacokinetics and pharmacodynamics of elvitegravir in response to ethanol exposure in HIV-1 infected monocytic (U1) cells

Ethanol consumption is negatively associated with antiretroviral therapy (ART) adherence and general health in HIV positive individuals. Previously, we demonstrated ethanol-mediated alterations to metabolism of elvitegravir (EVG) in human liver microsomes. In the current study, we investigated ethanol influence on the pharmacokinetic and pharmacodynamic interactions of EVG in HIV infected monocytic (U1) cells. U1 cells were treated with 5 μM EVG, 2 μM Cobicistat (COBI), a booster drug, and 20 mM ethanol for up to 24 hours. EVG, HIV p24 levels, alterations in cytochrome P450 (CYP) 3A4, MRP1, and MDR1 protein expressions were measured. Presence of ethanol demonstrated a significant effect on the total exposures of both EVG and EVG in combination with COBI. Ethanol also increased the HIV replication despite the presence of drugs and this elevated HIV replication was reduced in the presence of MRP1 and MDR1 inhibitors. Consequently, a slight increase in EVG concentration was observed in the presence of MRP1 inhibitor but not with MDR1 inhibitor. Furthermore, CYP3A4, MRP1 and MDR1 protein levels were significantly induced in treatment groups which included ethanol compared to those with no treatment. In summary, these findings suggest that Ethanol reduces intra cellular EVG exposure by modifying drug metabolism and transporter protein expression. This study provides valuable evidence for further investigation of ethanol effects on the intracellular concentration of EVG in ex vivo or in vivo studies.

P-glycoprotein (ABCB1) activity decreases raltegravir disposition in primary CD4+P-gphigh cells and correlates with HIV-1 viral load

Objectives

To evaluate the role of P-glycoprotein (P-gp) and multidrug-resistant-protein 1 (MRP1) on raltegravir intracellular drug disposition in CD4+ T cells, investigate the effect of HIV-1 infection on P-gp expression and correlate HIV-1 viraemia with P-gp activity in primary CD4+ T cell subsets.

Methods

The cellular accumulation ratio of [³H]raltegravir was quantified in CD4+ T cell lines overexpressing either P-gp (CEM-P-gp) or MRP1 (CEM-MRP1) and in primary CD3+CD4+ T cells with high (P-gp^high) and low P-gp activity (P-gp^low); inhibition of efflux transporters was confirmed by the intracellular retention of calcein-AM. The correlation of P-gp activity with HIV-1 viraemia was assessed in naive and memory T cell subsets from 21 HIV-1-infected treatment-naive subjects.

Results

[³H]Raltegravir cellular accumulation ratio decreased in CEM-P-gp cells (P < 0.0001). XR9051 (a P-gp inhibitor) and HIV-1 PIs reversed this phenomenon. Primary CD4+P-gp^high cells accumulated less raltegravir (38.4% ± 9.6%) than P-gp^low cells, whereas XR9051 also reversed this effect. In vitro HIV-1 infection of PBMCs and stimulation of CD4+ T cells increased P-gp mRNA and P-gp activity, respectively, while primary CD4+P-gp^high T cells sustained a higher HIV-1 replication than P-gp^low cells. A significant correlation between HIV-1 viraemia and P-gp activity was found in different CD4+ T cell subsets, particularly memory CD4+ T cells (r = 0.792, P < 0.0001).

Conclusions

Raltegravir is a substrate of P-gp in CD4+ T cells. Primary CD4+P-gp^high T cells eliminate intracellular raltegravir more readily than P-gp^low cells and HIV-1 viraemia correlates with P-gp overall activity. Specific CD4+P-gp^high T cell subsets could facilitate the persistence of viral replication in vivo and ultimately promote the appearance of drug resistance.

A rapid spin through oil results in higher cell-associated concentrations of antiretrovirals compared with conventional cell washing

BACKGROUND

Determination of cell-associated antiretroviral drug concentrations is necessary for research into reservoirs of HIV. Variation exists in cell-associated drug concentrations among research groups. One cause for this may be washing cells during processing. We explored spinning cells through oil to minimize this variability.

METHODS & RESULTS

Raltegravir, atazanavir, darunavir, efavirenz, lopinavir and ritonavir concentrations were assessed in CEM.ss T cells washed with HBSS and oil-spun cells. Oil-spun cells had significantly higher concentrations for all drugs compared with samples washed with HBSS.

CONCLUSION

The decline in cell-associated drug concentrations with saline washes compared with a single spin through oil shows the utility of a spin through oil. Oil centrifugation results in high cell-associated drug concentrations, and can be done in a fast, efficient manner.

Physiologically Based Pharmacokinetic Modelling to Inform Development of Intramuscular Long-Acting Nanoformulations for HIV

BACKGROUND AND OBJECTIVES

Antiretrovirals are currently used for the treatment and prevention of HIV infection. However, poor adherence and low tolerability of some existing oral formulations can hinder their efficacy. Long-acting (LA) injectable nanoformulations could help address these complications by simplifying antiretroviral administration. The aim of this study is to inform the optimisation of intramuscular LA formulations for eight antiretrovirals through physiologically based pharmacokinetic (PBPK) modelling.

METHODS

A whole-body PBPK model was constructed using mathematical descriptions of molecular, physiological and anatomical processes defining pharmacokinetics. These models were validated against available clinical data and subsequently used to predict the pharmacokinetics of injectable LA formulations

RESULTS

The predictions suggest that monthly intramuscular injections are possible for dolutegravir, efavirenz, emtricitabine, raltegravir, rilpivirine and tenofovir provided that technological challenges to control their release rate can be addressed.

CONCLUSIONS

These data may help inform the target product profiles for LA antiretroviral reformulation strategies.

Mucosal tissue pharmacokinetics of the integrase inhibitor raltegravir in a humanized mouse model: Implications for HIV pre-exposure prophylaxis

Orally administered anti-retroviral drugs show considerable promise for HIV/AIDS pre-exposure prophylaxis (PrEP). For the success of these strategies, pharmacokinetic (PK) data defining the optimal concentration of the drug needed for protection in relevant mucosal exposure sites is essential. Here we employed a humanized mouse model to derive comprehensive PK data on the HIV integrase inhibitor raltegravir (RAL), a leading PrEP drug candidate. Under steady state conditions following oral dosing, plasma and multiple mucosal tissues were sampled simultaneously. RAL exhibited higher drug exposure in mucosal tissues relative to that in plasma with one log higher exposure in vaginal and rectal tissue and two logs higher exposure in intestinal mucosa reflecting the trends seen in the human studies. These data demonstrate the suitability of RAL for HIV PrEP and validate the utility of humanized mouse models for deriving important preclinical PK-PD data.

Correlation between plasma, intracellular, and cervical tissue levels of raltegravir at steady-state dosing in healthy women

Raltegravir is an antiretroviral with potential value for preexposure prophylaxis (PrEP) against HIV, but the intracellular pharmacokinetics in genital tissue have not been described. In this study, healthy, HIV-uninfected nonpregnant women took 400 mg of raltegravir twice daily for 22 days. On day 8, 15, and 22, blood was collected 0, 4, 6, 8, and 12 h and cervical biopsy specimens taken 0, 6, and 12 h after raltegravir dosing. Plasma and intracellular raltegravir concentrations in peripheral blood mononuclear cells (PBMC) and cervical tissue were measured by tandem mass spectrometry. Linear mixed effects models evaluated correlations between different sample types, as well as differences in concentration between phases of the menstrual cycle. Ten women were enrolled: 9 completed all three visits and 1 completed two visits. The age (mean ± standard deviation) of participants was 30 ± 8 years. Trough plasma concentrations of raltegravir 12 h after a directly observed dose were above the HIV 95% inhibitory concentration (IC95) of 33 nM (14.6 ng/ml) in 96% of measurements, compared to 67% of PBMC and 89% of cervical tissue trough values. Across all measurements, only 2% (3/135) of plasma values fell below the IC95, compared to 10% (13/135) for PBMC and 6% (5/81) for cervical tissue. There was no impact of menstrual phase on raltegravir concentrations. In conclusion, cervical tissue raltegravir concentrations were no greater than plasma concentrations, and ∼10% of all cervical tissue trough values were below the IC95, making the current twice-daily formulation of raltegravir impractical for PrEP.

Role of P-glycoprotein in the efflux of raltegravir from human intestinal cells and CD4+ T-cells as an interaction target for anti-HIV agents

Cellular efflux and uptake transports of several anti-HIV agents are mediated by plasma membrane-localized solute transporters. However, transporters involved in raltegravir disposition have not been fully characterized. Here, we performed in vitro studies to identify transporters mediating transcellular transport of raltegravir. Transepithelial raltegravir transport was examined using porcine kidney epithelial cell line (LLC-PK1) and LLC-PK1 cells stably transfected with P-glycoprotein (also known as Multiple drug resistance 1) (L-MDR1). Transepithelial transport of raltegravir in Caco-2 cell monolayers, and intracellular accumulation of raltegravir in the MT-2 and MT-4 (CD4+ T-) cells were measured in the presence or absence of anti-HIV agents. The uptake of raltegravir was investigated in HEK-293 cells expressing each of several solute carrier family transporters. The apical-to-basal raltegravir transport was significantly decreased in L-MDR1 as compared to that in LLC-PK1 monolayers. In HEK-293 cells expressing breast cancer resistance protein (BCRP), raltegravir accumulation was lower than that in the mock-transfected cells. In Caco-2 cells, protease inhibitors including nelfinavir, ritonavir and lopinavir enhanced the apical-to-basal transport of raltegravir. By contrast, reverse transcriptase inhibitors such as zidovudine, efavirenz, and nevirapine, had no effect on raltegravir transport. The cellular accumulation of raltegravir in MT-2 cells, which express P-glycoprotein, was significantly increased in the presence of protease inhibitors. By contrast, protease inhibitors only marginally increased the accumulation of raltegravir in MT-4 cells, in which P-glycoprotein is not expressed. The present findings suggest that raltegravir is a substrate of both P-glycoprotein and BCRP. Protease inhibitors increase the absorptive transport of raltegravir in Caco-2 cells, and the cellular accumulation in T-cells, at least in part, by P-glycoprotein-mediated interaction.

Variability of raltegravir plasma levels in the clinical setting

Therapeutic drug monitoring of raltegravir Ctrough levels was carried out in the setting of the Raltegravir Switch for Toxicity or Adverse events (RASTA) trial, a randomized pilot study exploring a 48-week safety and efficacy of treatment switch to raltegravir associated with tenofovir/emtricitabine or abacavir/lamivudine in patients with regimens with optimal virologic control. Blood sampling for measurement of raltegravir plasma levels was carried out at weeks 4, 12, 24, 36 and 48. Plasma samples were analysed by a recently developed and validated UPLC-MS method. A total of 164 samples from 39 patients were assayed. Analysis for intra- and inter-subject variability was restricted to those patients with 4 or more determinations, including 30 patients and 142 determinations. The intra- and inter-subject variability measures were 85.9 and 124.6%, respectively, with an intra-/inter-subject variability ratio of 69%. We also analysed data from a subset of patients with well-documented adherence to protocol, defined as protocol compliant population, including 21 patients and 93 determinations. In this subpopulation, we estimated intra- and inter-subject variability of 79.87% and 110%, respectively, with an intra-/inter-subject variability ratio of 72.6%. This study confirms the notion that raltegravir is a highly variable drug according to the European Medicines Agency criteria. While this condition does not favour the adoption of therapeutic drug monitoring in the clinical practice, the latter is deemed useful in patients with drug plasma concentrations below or near the threshold level of efficacy (since intracellular raltegravir levels might be as low as 5% of the corresponding plasma levels), or to identify drug-drug interactions of potential clinical relevance.

Pharmacogenetics-based population pharmacokinetic analysis of etravirine in HIV-1 infected individuals

OBJECTIVES

Etravirine (ETV) is metabolized by cytochrome P450 (CYP) 3A, 2C9, and 2C19. Metabolites are glucuronidated by uridine diphosphate glucuronosyltransferases (UGT). To identify the potential impact of genetic and non-genetic factors involved in ETV metabolism, we carried out a two-step pharmacogenetics-based population pharmacokinetic study in HIV-1 infected individuals.

MATERIALS AND METHODS

The study population included 144 individuals contributing 289 ETV plasma concentrations and four individuals contributing 23 ETV plasma concentrations collected in a rich sampling design. Genetic variants [n=125 single-nucleotide polymorphisms (SNPs)] in 34 genes with a predicted role in ETV metabolism were selected. A first step population pharmacokinetic model included non-genetic and known genetic factors (seven SNPs in CYP2C, one SNP in CYP3A5) as covariates. Post-hoc individual ETV clearance (CL) was used in a second (discovery) step, in which the effect of the remaining 98 SNPs in CYP3A, P450 cytochrome oxidoreductase (POR), nuclear receptor genes, and UGTs was investigated.

RESULTS

A one-compartment model with zero-order absorption best characterized ETV pharmacokinetics. The average ETV CL was 41 (l/h) (CV 51.1%), the volume of distribution was 1325 l, and the mean absorption time was 1.2 h. The administration of darunavir/ritonavir or tenofovir was the only non-genetic covariate influencing ETV CL significantly, resulting in a 40% [95% confidence interval (CI): 13-69%] and a 42% (95% CI: 17-68%) increase in ETV CL, respectively. Carriers of rs4244285 (CYP2C19*2) had 23% (8-38%) lower ETV CL. Co-administered antiretroviral agents and genetic factors explained 16% of the variance in ETV concentrations. None of the SNPs in the discovery step influenced ETV CL.

CONCLUSION

ETV concentrations are highly variable, and co-administered antiretroviral agents and genetic factors explained only a modest part of the interindividual variability in ETV elimination. Opposing effects of interacting drugs effectively abrogate genetic influences on ETV CL, and vice-versa.

HIV protease inhibitors disrupt lipid metabolism by activating endoplasmic reticulum stress and inhibiting autophagy activity in adipocytes

BACKGROUND

HIV protease inhibitors (PI) are core components of Highly Active Antiretroviral Therapy (HAART), the most effective treatment for HIV infection currently available. However, HIV PIs have now been linked to lipodystrophy and dyslipidemia, which are major risk factors for cardiovascular disease and metabolic syndrome. Our previous studies have shown that HIV PIs activate endoplasmic reticulum (ER) stress and disrupt lipid metabolism in hepatocytes and macrophages. Yet, little is known on how HIV PIs disrupt lipid metabolism in adipocytes, a major cell type involved in the pathogenesis of metabolic syndrome.

METHODOLOGY AND PRINCIPAL FINDINGS

Cultured and primary mouse adipocytes and human adipocytes were used to examine the effect of frequently used HIV PIs in the clinic, lopinavir/ritonavir, on adipocyte differentiation and further identify the underlying molecular mechanism of HIV PI-induced dysregulation of lipid metabolism in adipocytes. The results indicated that lopinavir alone or in combination with ritonavir, significantly activated the ER stress response, inhibited cell differentiation, and induced cell apoptosis in adipocytes. In addition, HIV PI-induced ER stress was closely linked to inhibition of autophagy activity. We also identified through the use of primary adipocytes of CHOP(-/-) mice that CHOP, the major transcriptional factor of the ER stress signaling pathway, is involved in lopinavir/ritonavir-induced inhibition of cell differentiation in adipocytes. In addition, lopinavir/ritonavir-induced ER stress appears to be associated with inhibition of autophagy activity in adipocytes.

CONCLUSION AND SIGNIFICANCE

Activation of ER stress and impairment of autophagy activity are involved in HIV PI-induced dysregulation of lipid metabolism in adipocytes. The key components of ER stress and autophagy signaling pathways are potential therapeutic targets for HIV PI-induced metabolic side effects in HIV patients.

Patterns of adherence to raltegravir-based regimens and the risk of virological failure among HIV-infected patients: the RALTECAPS cohort study

Adherence patterns and their influence on virologic outcome are well characterized for protease inhibitor (PI)- and non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens. We aimed to determine how patterns of adherence to raltegravir influence the risk of virological failure. We conducted a prospective multicenter cohort following 81 HIV-infected antiretroviral-naive or experienced subjects receiving or starting twice-a-day raltegravir-based antiretroviral therapy. Their adherence patterns were monitored using the Medication Events Monitoring System. During follow-up (188 days, ±77), 12 (15%) of 81 subjects experienced virological failure. Longer treatment interruption [adjusted odds ratio per 24-hour increase: 2.4; 95% confidence interval: 1.2 to 6.9; P < 0.02] and average adherence (odds ratio per 5% increase: 0.68; 95% confidence interval: 0.46 to 1.00, P < 0.05) were both independently associated with virological failure controlling for prior duration of viral suppression. Timely interdose intervals and high levels of adherence to raltegravir are both necessary to control HIV replication.

Measurement of plasma and intracellular concentrations of raltegravir in patients with HIV infection

Paired plasma and intracellular samples were obtained from 12 HIV-infected adults taking raltegravir twice daily (b.i.d.), and after switching to once daily. With b.i.d. dosing, no plasma trough concentrations were below the IC95, in contrast to 33% for once daily dosing. Fifty percent of the once daily group had intracellular trough concentrations below the inhibitory concentration 95 (IC95), 25% in the b.i.d. group. Lower plasma and intracellular concentrations may contribute to inferior virologic suppression rates observed with once daily raltegravir dosing.

Population pharmacokinetic analysis and pharmacogenetics of raltegravir in HIV-positive and healthy individuals

The objectives of this study were to characterize raltegravir (RAL) population pharmacokinetics in HIV-positive (HIV(+)) and healthy individuals, identify influential factors, and search for new candidate genes involved in UDP glucuronosyltransferase (UGT)-mediated glucuronidation. The pharmacokinetic analysis was performed with NONMEM. Genetic association analysis was performed with PLINK using the relative bioavailability as the phenotype. Simulations were performed to compare once- and twice-daily regimens. A 2-compartment model with first-order absorption adequately described the data. Atazanavir, gender, and bilirubin levels influenced RAL relative bioavailability, which was 30% lower in HIV(+) than in healthy individuals. UGT1A9*3 was the only genetic variant possibly influencing RAL pharmacokinetics. The majority of RAL pharmacokinetic variability remains unexplained by genetic and nongenetic factors. Owing to the very large variability, trough drug levels might be very low under the standard dosing regimen, raising the question of a potential relevance of therapeutic drug monitoring of RAL in some situations.

Plasma and intracellular pharmacokinetics of darunavir/ritonavir once daily and raltegravir once and twice daily in HIV-infected individuals

OBJECTIVES

To investigate the pharmacokinetics of darunavir/ritonavir and raltegravir, in HIV-infected subjects, in both plasma and at the intracellular (IC) site of action.

METHODS

HIV-infected patients on antiretroviral therapy received raltegravir 400 mg twice daily for 21 days (period 1); darunavir/ritonavir 800/100 mg once daily was added for 14 days (period 2), and patients were randomized to continue raltegravir twice daily (group 1) or to switch to 800 mg once daily (group 2), then they all stopped raltegravir intake and continued darunavir/ritonavir once daily for 14 days (period 3). Drug concentrations in plasma and cells (peripheral blood mononuclear cell) were measured, and differences in geometric mean ratios (GMR) and 90% confidence intervals (CI) between period 2 versus period 3 and period 2 versus period 1 were assessed.

RESULTS

Twenty-four patients completed the study. Group 1 GMR (90% CI) of darunavir area under the curve (AUC) with and without raltegravir was 1.24 (1.13 to 1.45) for plasma and 1.24 (1.07 to 1.73) for cells and for group 2 was 1.14 (1.07 to 1.24) and 1.03 (0.94 to 1.16). GMR (90% CI) of raltegravir AUC without and with darunavir/ritonavir (plasma and cells) for group 1 was 0.90 (0.73 to 1.44) and 1.02 (0.81 to 1.67) and for group 2 was 1.21 (1.03 to 1.77) and 1.27 (1.07 to 1.94). Geometric mean IC to plasma AUC ratios were 5.3 and 4.9 for darunavir in groups 1 and 2 when darunavir/ritonavir was given alone and 4.9 and 5.6 for raltegravir when given alone. These ratios were not altered by the coadministered drug.

CONCLUSIONS

No remarkable interactions between darunavir/ritonavir and raltegravir in plasma or cells were seen. Raltegravir IC concentrations are higher than previously reported; the difference being due to modified cell isolation procedures that reduced drug loss caused by washing.

A sensitive liquid chromatography coupled with mass spectrometry method for the intracellular and plasma quantification of raltegravir after solid-phase extraction

INTRODUCTION

Liquid chromatography coupled with mass spectrometry for the quantification of raltegravir in human plasma and peripheral blood mononuclear cells has been developed.

METHODS

Sample preparations were based on a fully automated solid-phase extraction process. Mass spectrometric data were acquired in a single-ion monitoring method. Raltegravir and quinoxaline, the internal standard, were well separated in a gradient mode over 15 min.

KEY FINDINGS

Validation study exhibited excellent linearity, with good intra- and inter-day precision and accuracy.

CONCLUSIONS

The assay was successfully applied to the raltegravir quantification in HIV-infected patients.