Intracellular and plasma pharmacokinetics of saquinavir-ritonavir, administered at 1,600/100 milligrams once daily in human immunodeficiency virus-infected patients

The Effect of Rifampicin on Darunavir, Ritonavir, and Dolutegravir Exposure within Peripheral Blood Mononuclear Cells: a Dose Escalation Study

Ritonavir-boosted darunavir (DRV/r) and dolutegravir (DTG) are affected by induction of metabolizing enzymes and efflux transporters caused by rifampicin (RIF). This complicates the treatment of people living with HIV (PLWH) diagnosed with tuberculosis. Recent data showed that doubling DRV/r dose did not compensate for this effect, and hepatic safety was unsatisfactory. We aimed to evaluate the pharmacokinetics of DRV, ritonavir (RTV), and DTG in the presence and absence of RIF in peripheral blood mononuclear cells (PBMCs). PLWH were enrolled in a dose-escalation crossover study with 6 treatment periods of 7 days. Participants started with DRV/r 800/100 mg once daily (QD), RIF and DTG were added before the RTV dose was doubled, and then they received DRV/r 800/100 twice daily (BD) and then 1,600/200 QD or vice versa. Finally, RIF was withdrawn. Plasma and intra-PBMC drug concentrations were measured through validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Seventeen participants were enrolled but only 4 completed all study phases due to high incidence of liver toxicity. Intra-PBMC DRV trough serum concentration (C_trough) after the addition of RIF dropped from a median (interquartile range [IQR]) starting value of 261 ng/mL (158 to 577) to 112 ng/mL (18 to 820) and 31 ng/mL (12 to 331) for 800/100 BD and 1,600/200 QD DRV/r doses, respectively. The DRV intra-PBMC/plasma ratio increased significantly (P = 0.003). DTG and RIF intra-PBMC concentrations were in accordance with previous reports in the absence of RIF or DRV/r. This study showed a differential impact of enzyme and/or transporter induction on DRV/r concentrations in plasma and PBMCs, highlighting the usefulness of studying intra-PBMC pharmacokinetics with drug-drug interactions. (This study has been registered at ClinicalTrials.gov under registration no. NCT03892161.)

Relationship between plasma and intracellular concentrations of bedaquiline and its M2 metabolite in South African patients with rifampin-resistant TB

Bedaquiline is recommended for the treatment of all patients with rifampin-resistant tuberculosis (RR-TB). Bedaquiline accumulates within cells, but its intracellular pharmacokinetics have not been characterized, which may have implications for dose optimization. We developed a novel assay using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure the intracellular concentrations of bedaquiline and its primary metabolite M2 in patients with RR-TB in South Africa. Twenty-one participants were enrolled and underwent sparse sampling of plasma and peripheral blood mononuclear cells (PBMCs) at months 1, 2, and 6 of treatment and at 3 and 6 months after bedaquiline treatment completion. Intensive sampling was performed at month 2. We used noncompartmental analysis to describe plasma and intracellular exposures and a population pharmacokinetic model to explore the relationship between plasma and intracellular pharmacokinetics and the effects of key covariates. Bedaquiline concentrations from month 1 to month 6 of treatment ranged from 94.7 to 2,540 ng/ml in plasma and 16.2 to 5,478 ng/ml in PBMCs, and concentrations of M2 over the 6-month treatment period ranged from 34.3 to 496 ng/ml in plasma and 109.2 to 16,764 ng/ml in PBMCs. Plasma concentrations of bedaquiline were higher than those of M2, but intracellular concentrations of M2 were considerably higher than those of bedaquiline. In the pharmacokinetic modeling, we estimated a linear increase in the intracellular-plasma accumulation ratio for bedaquiline and M2, reaching maximum effect after 2 months of treatment. The typical intracellular-plasma ratios 1 and 2 months after start of treatment were 0.61 (95% confidence interval [CI]: 0.42 to 0.92) and 1.10 (95% CI: 0.74 to 1.63) for bedaquiline and 12.4 (95% CI: 8.8 to 17.8) and 22.2 (95% CI: 15.6 to 32.3) for M2. The intracellular-plasma ratios for both bedaquiline and M2 were decreased by 54% (95% CI: 24 to 72%) in HIV-positive patients compared to HIV-negative patients. Bedaquiline and M2 were detectable in PBMCs 6 months after treatment discontinuation. M2 accumulated at higher concentrations intracellularly than bedaquiline, supporting in vitro evidence that M2 is the main inducer of phospholipidosis.

Emerging Role of the Spleen in the Pharmacokinetics of Monoclonal Antibodies, Nanoparticles and Exosomes

After being absorbed, drugs distribute in the body in part to reach target tissues, in part to be disposed in tissues where they do not exert clinically-relevant effects. Therapeutically-relevant effects are usually terminated by drug metabolism and/or elimination. The role that has been traditionally ascribed to the spleen in these fundamental pharmacokinetic processes was definitely marginal. However, due to its high blood flow and to the characteristics of its microcirculation, this organ would be expected to be significantly exposed to large, new generation drugs that can hardly penetrate in other tissues with tight endothelial barriers. In the present review, we examine the involvement of the spleen in the disposition of monoclonal antibodies, nanoparticles and exosomes and the possible implications for their therapeutic efficacy and toxicity. The data that we will review lead to the conclusion that a new role is emerging for the spleen in the pharmacokinetics of new generation drugs, hence suggesting that this small, neglected organ will certainly deserve stronger attention by pharmacologists in the future.

Intracellular accumulation of Praziquantel in T lymphoblastoid cell lines, CEM (parental) and CEMVBL(P-gp-overexpressing)

Background

Praziquantel (PZQ) is an antihelminthic drug whose P-glycoprotein (P-gp) substrate specificity has not been conclusively characterized. We investigated its specificity by comparing its in vitro intracellular accumulation in CEM (parental), and CEMvbl cells which over express P-gp, a drug efflux transporter. Saquinavir (SQV), a known substrate of efflux transporters was used as control.

Methods

A reversed phase liquid chromatography method was developed to simultaneously quantify PZQ and SQV in cell culture media involving involved a liquid - liquid extraction followed by ultra-high performance liquid chromatography using a Hypurity C₁₈ column and ultraviolet detection set at a wavelength of 215 nm. The mobile phase consisted of ammonium formate, acetonitrile and methanol (57:38:5 v/v). Separation was facilitated via isocratic elution at a flow rate of 1.5 ml/min, with clozapine (CLZ) as internal standard. This was validated over the concentration range of 1.6 to 25.6 μM for all analytes. Intracellular accumulation of SQV in CEMvbl was significantly lower compared to that in CEM cells (0.1 ± 0.031 versus 0.52 ± 0.046, p = 0.03 [p <0.05]).

Results

Accumulation of PZQ in both cell lines cells were similar (0.05 ± 0.005 versus 0.04 ± 0.009, p = 0.4) suggesting that it is not a substrate of P-gp in CEM cells. In presence tariquidar, a known inhibitor of P-gp, the intracellular accumulation of SQV in CEMvbl cells increased (0.52 ± 0.068 versus 0.61 ± 0.102, p = 0.34 in CEM cells and 0.09 ± 0.015 versus 0.56 ± 0.089, p = 0.029 [p < 0.05] in CEMvbl cells). PZQ did not significantly affect the accumulation of SQV in either CEM (0.52 ± 0.068 versus 0.54 ± 0.061, p = 0.77), or in CEMvbl cells (0.09 ± 0.015 versus 0.1 ± 0.031, p = 0.89) cells compared to tariquidar, implying that PZQ is not an inhibitor of P-gp in CEMvbl cells.

Conclusions

PZQ is neither a substrate nor an inhibitor of the efflux drug transporter P-gp in T-lymphoblastoid cells, CEM and CEMvbl. We also report a simple, accurate and precise method for simultaneous quantification of PZQ and SQV.

UHPLC-MS/MS method with automated on-line solid phase extraction for the quantification of entecavir in peripheral blood mononuclear cells of HBV+ patients

To date five nucleoside analogs are used in the treatment of chronic hepatitis B: among these, entecavir is the most used. Nevertheless a few information about its distribution in tissues is currently known. Since the determination of entecavir disposition in the hepatocytes is impracticable because of its invasiveness, the quantification in an "easier-to-obtain" cellular model could be a good choice. In this work, we developed and validated an ultra performance liquid chromatography-tandem mass spectrometry assay based on an automated on-line SPE, to quantify entecavir concentrations in peripheral blood mononucleated cells (PBMCs), in both its phosphorylated and un-phosphorylated forms. To achieve this, each PBMC isolate was divided in two aliquots, one was treated with acid phosphatase to convert entecavir phosphorylated metabolites into free form, the other one was not-treated. Standards and quality controls were prepared in PBMCs, isolated from healthy donors, and underwent the same process. 20 μL of the resulting solutions were injected in the on-line SPE system. Thymidine was used as internal standard. Calibration curves fitted a linear model for entecavir levels in a range from 0.039 ng to 5 ng (mean r(2)=0.998). Accuracy, intra-day and inter-day precision of the method fitted FDA guidelines recommendations. Moreover, recovery was consistent and matrix effect resulted low and reproducible. We tested this method by monitoring entecavir concentrations in PBMCs from 28HBV mono-infected patients, confirming its reliability and suitability for the evaluation of intracellular entecavir penetration.

Quantification of cell-associated atazanavir, darunavir, lopinavir, ritonavir, and efavirenz concentrations in human mononuclear cell extracts

An ultrasensitive assay utilizing high-pressure liquid chromatography and mass spectrometry detection was developed and validated for the quantification of the antiretrovirals atazanavir (ATV), darunavir (DRV), lopinavir (LPV), ritonavir (RTV), and efavirenz (EFV) in human mononuclear cell (MNC) extracts. The assay utilizes 20 μl of cellular extract that contains as few as 50,000 MNCs. The analytical range of the assay is 0.0200 to 10.0 fmol/μl for ATV, 0.0500 to 25.0 fmol/μl for DRV, LPV, and RTV, and 0.200 to 100 fmol/μl for EFV. The assay has proven to be a clinically useful tool for investigating antiretroviral drug concentrations in virologic sanctuaries where harvested cell numbers are extremely low. The assay provides a tool for investigators to explore the clinical pharmacology of strategies for prevention, treatment, and cure in pathophysiologically relevant sites.

Saquinavir inhibits early events associated with establishment of HIV-1 infection: potential role for protease inhibitors in prevention

The maturation of newly formed human immunodeficiency virus type 1 (HIV-1) virions is a critical step for the establishment of productive infection. We investigated the potential of saquinavir (SQV), a protease inhibitor (PI) used in highly active antiretroviral therapy (HAART), as a candidate microbicide. SQV inhibited replication of clade B and clade C isolates in a dose-dependent manner in all cellular models tested: PM-1 CD4 T cells, peripheral blood mononuclear cells (PBMCs), monocyte-derived macrophages (MDMs), and immature monocyte-derived dendritic cells (iMDDCs). SQV also inhibited production of infectious virus in cervical, penile, and colorectal explants cocultured with T cells. Moreover, SQV demonstrated inhibitory potency against trans infection of T cells by in vitro-derived dendritic cells and by primary dendritic cells that emigrate from penile and cervical tissue explants. No cellular or tissue toxicity was detected in the presence of SQV, suggesting that this drug could be considered for development as a component of an effective microbicide, capable of blocking viral maturation and transmission of HIV-1 at mucosal surfaces.

Inhibition of autoprocessing of natural variants and multidrug resistant mutant precursors of HIV-1 protease by clinical inhibitors

Self-cleavage at the N terminus of HIV-1 protease from the Gag-Pol precursor (autoprocessing) is crucial for stabilizing the protease dimer required for onset of mature-like catalytic activity, viral maturation, and propagation. Among nine clinical protease inhibitors (PIs), darunavir and saquinavir were the most effective in inhibiting wild-type HIV-1 group M precursor autoprocessing, with an IC(50) value of 1-2 μM, 3-5 orders of magnitude higher than their binding affinities to the corresponding mature protease. Accordingly, both group M and N precursor-PI complexes exhibit T(m)s 17-21 °C lower than those of the corresponding mature protease-PI complexes suggestive of markedly reduced stabilities of the precursor dimer-PI ensembles. Autoprocessing of group N (natural variant) and three group M precursors bearing 11-20 mutations associated with multidrug resistance was either weakly responsive or fully unresponsive to inhibitors at concentrations up to a practical limit of approximately 150 μM PI. This observation parallels decreases of up to 8 × 10(3)-fold (e.g., 5 pM to 40 nM) in the binding affinity of darunavir and saquinavir to mature multidrug resistant proteases relative to wild type, suggesting that inhibition of some of these mutant precursors will occur only in the high μM to mM range in extreme PI-resistance, which is an effect arising from coordinated multiple mutations. An extremely darunavir-resistant mutant precursor is more responsive to inhibition by saquinavir. These findings raise the questions whether clinical failure of PI therapy is related to lack of inhibition of autoprocessing and whether specific inhibitors can be designed with low-nM affinity to target autoprocessing.

Intracellular and plasma steady-state pharmacokinetics of raltegravir, darunavir, etravirine and ritonavir in heavily pre-treated HIV-infected patients

AIM

To study the steady-state plasma and intracellular pharmacokinetics of raltegravir, etravirine, darunavir and ritonavir in heavily pre-treated patients.

METHODS

Patients on a salvage regimen containing raltegravir, etravirine, darunavir and ritonavir were eligible for inclusion. During a 12 h dosing interval plasma and peripheral blood mononuclear cells were collected. Drug concentrations were measured using a validated LC-MS/MS assay and pharmacokinetic analysis was performed using non-linear mixed effect modelling.

RESULTS

Irregular absorption was observed with raltegravir and darunavir, which may be caused by enterohepatic cycling. Relative bioavailability of ritonavir was low, when compared with other ritonavir regimens. Raltegravir plasma pharmacokinetics showed wide interpatient variability, while intracellular raltegravir concentrations could not be detected (<0.001 mg l(-1) in cell lysate). The intracellular to plasma ratios for etravirine, darunavir and ritonavir were 12.9, 1.32 and 7.72, respectively, and the relative standard error of these estimates were 16.3%, 12.3% and 13.0%.

CONCLUSIONS

The observed distinct intracellular accumulation indicated that these drugs have different affinity for the cellular compartment. The relatively high intracellular accumulation of etravirine may explain its efficacy and its previously described absence of PK-PD relationships in the therapeutic concentration range, when compared with other non-nucleoside reverse transcriptase inhibitors. Lastly, the intracellular concentrations of ritonavir seem sufficient for inhibition of viral replication in the cellular compartment in PI-naive patients, but not in patients with HIV harbouring PI resistance.

Ultra-fast analysis of plasma and intracellular levels of HIV protease inhibitors in children: a clinical application of MALDI mass spectrometry

HIV protease inhibitors must penetrate into cells to exert their action. Differences in the intracellular pharmacokinetics of these drugs may explain why some patients fail on therapy or suffer from drug toxicity. Yet, there is no information available on the intracellular levels of HIV protease inhibitors in HIV infected children, which is in part due to the large amount of sample that is normally required to measure the intracellular concentrations of these drugs. Therefore, we developed an ultra-fast and sensitive assay to measure the intracellular concentrations of HIV protease inhibitors in small amounts of peripheral blood mononuclear cells (PBMCs), and determined the intracellular concentrations of lopinavir and ritonavir in HIV infected children. An assay based on matrix-assisted laser desorption/ionization (MALDI) - triple quadrupole mass spectrometry was developed to determine the concentrations of HIV protease inhibitors in 10 µL plasma and 1×10⁶ PBMCs. Precisions and accuracies were within the values set by the FDA for bioanalytical method validation. Lopinavir and ritonavir did not accumulate in PBMCs of HIV infected children. In addition, the intracellular concentrations of lopinavir and ritonavir correlated poorly to the plasma concentrations of these drugs. MALDI-triple quadrupole mass spectrometry is a new tool for ultra-fast and sensitive determination of drug concentrations which can be used, for example, to assess the intracellular pharmacokinetics of HIV protease inhibitors in HIV infected children.

Impact of ATP-binding cassette transporters on human immunodeficiency virus therapy

Even though potent antiretrovirals are available against human immunodeficiency virus (HIV)-1 infection, therapy fails in a significant fraction of patients. Among the most relevant reasons for treatment failure are drug toxicity and side effects, but also the development of viral resistance towards the drugs applied. Efflux by ATP-binding cassette (ABC-) transporters represents one major mechanism influencing the pharmacokinetics of antiretroviral drugs and particularly their distribution, thus modifiying the concentration within the infected cells, that is, at the site of action. Moreover, drug-drug interactions may occur at the level of these transporters and modulate their activity or expression thus influencing the efficacy and toxicity of the substrate drugs. This review summarizes current knowledge on the interaction of antiretrovirals used for HIV-1 therapy with ABC-transporters and highlights the impact of ABC-transporters for cellular resistance and therapeutic success. Moreover, the suitability of different cell models for studying the interaction of antiretrovirals with ABC-transporters is discussed.

Efficacy, safety and pharmacokinetic of once-daily boosted saquinavir (1500/100 mg) together with 2 nucleos(t)ide reverse transcriptase inhibitors in real life: a multicentre prospective study

Background

Ritonavir-boosted saquinavir (SQVr) is nowadays regarded as an alternative antiretroviral drug probably due to several drawbacks, such as its high pill burden, twice daily dosing and the requirement of 200 mg ritonavir when given at the current standard 1000/100 mg bid dosing. Several once-daily SQVr dosing schemes have been studied with the 200 mg SQV old formulations, trying to overcome some of these disadvantages. SQV 500 mg strength tablets became available at the end of 2005, thus facilitating a once-daily regimen with fewer pills, although there is very limited experience with this formulation yet.

Methods

Prospective, multicentre study in which efficacy, safety and pharmacokinetics of a regimen of once-daily SQVr 1500/100 mg plus 2 NRTIs were evaluated under routine clinical care conditions in either antiretroviral-naïve patients or in those with no previous history of antiretroviral treatments and/or genotypic resistance tests suggesting SQV resistance. Plasma SQV trough levels were measured by HPLV-UV.

Results

Five hundred and fourteen caucasian patients were included (47.2% coinfected with hepatitis C and/or B virus; 7.8% with cirrhosis). Efficacy at 52 weeks (plasma RNA-HIV <50 copies/ml) was 67.7% (CI₉₅: 63.6 - 71.7%) by intention-to-treat, and 92.2% (CI₉₅: 89.8 - 94.6%) by on-treatment analysis. The reasons for failure were: dropout or loss to follow-up (18.4%), virological failure (7.8%), adverse events (3.1%), and other reasons (4.6%). The high rate of dropout may be explained by an enrollement and follow-up under routine clinical care condition, and a population with a significant number of drug users. The median SQV Cmin (n = 49) was 295 ng/ml (range, 53-2172). The only variable associated with virological failure in the multivariate analysis was adherence (OR: 3.36; CI95, 1.51-7.46, p = 0.003).

Conclusions

Our results suggests that SQVr (1500/100 mg) once-daily plus 2 NRTIs is an effective regimen, without severe clinical adverse events or hepatotoxicity, scarce lipid changes, and no interactions with methadone. All these factors and its once-daily administration suggest this regimen as an appropriate option in patients with no SQV resistance-associated mutations.

The complexities of antiretroviral drug-drug interactions: role of ABC and SLC transporters

Treatment of human immunodeficiency virus (HIV) infection involves a combination of several antiviral agents belonging to different pharmacological classes. This combination is referred to as highly active antiretroviral therapy (HAART). This treatment has proved to be very effective in suppressing HIV replication, but antiretroviral drugs have complex pharmacokinetic properties involving extensive drug metabolism and transport by membrane-associated drug carriers. Combination drug therapy often introduces complex drug-drug interactions that can result in toxic or sub-therapeutic drug concentrations, compromising treatment. This review focuses on the role of ATP-binding cassette (ABC) membrane-associated efflux transporters and solute carrier (SLC) uptake transporters in antiretroviral drug disposition, and identifies clinically important antiretroviral drug-drug interactions associated with changes in drug transport.

Once-daily treatment with saquinavir mesylate (2000 mg) and ritonavir (100 mg) together with a fixed-dose combination of abacavir/lamivudine (600/300 mg) or tenofovir/emtricitabine (245/200 mg) in HIV-1-infected patients

OBJECTIVES

To investigate the feasibility and pharmacokinetics of a once-daily regimen of 2000 mg saquinavir mesylate boosted with 100 mg ritonavir.

PATIENTS AND METHODS

Patients successfully treated with 1000 mg saquinavir boosted with 100 mg ritonavir twice daily together with two nucleoside or nucleotide reverse transcriptase inhibitors [N(t)RTIs] who were switched to 2000 mg saquinavir with 100 mg ritonavir once daily with unchanged N(t)RTI therapy were analysed. CD4 cells, HIV-RNA PCR and metabolic parameters were compared between baseline and 3, 6, 9 and 12 months after the switch. Saquinavir and ritonavir drug levels were measured before and a median of 3 weeks after switching from twice to once daily at 0, 1, 2, 4, 6, 9, 12 and 24 h after intake of the medication. The area under the serum concentration-time curve from 0 to 24 h (AUC(0-24)) was calculated using the trapezoidal rule.

RESULTS

Eighteen patients (16 males, median age of 41 years) with a median CD4 cell count of 464 cells/mm(3) were analysed. HIV-RNA PCR remained <500 copies/mL for all patients. After switching from 100 mg twice daily to 100 mg once daily, the AUC(0-24) for ritonavir decreased significantly [21 874 to 10 267 ng.h/mL, geometric mean ratio (GMR) = 0.47; P < 0.001], whereas the AUC(0-24) for saquinavir decreased only marginally from 35 000 to 34 490 ng.h/mL (GMR = 0.99; P = 0.426). The CD4 cell count and the fasting metabolic parameters remained unchanged.

CONCLUSIONS

Once-daily treatment with ritonavir-boosted saquinavir was well tolerated and resulted in similar saquinavir drug exposure despite much lower ritonavir concentrations when compared with a twice-daily dosing schedule.

A mass spectrometry based imaging method developed for the intracellular detection of HIV protease inhibitors

Mass spectrometry imaging is a promising technique for measuring drugs and drug metabolites in cells and tissues. In this manuscript we describe a method for the imaging of HIV protease inhibitors. As a model system we used Mono Mac 6 cells cultured with the HIV protease inhibitors saquinavir and nelfinavir deposited on glass slides using a cytocentrifuge. A sublimation/deposition device for homogeneous matrix deposition was constructed which allows imaging of these HIV protease inhibitors at clinically relevant concentrations. Using this matrix sublimation/deposition method, glass slides containing the cytocentrifuged cells can be measured and analyzed by two types of mass spectrometry techniques, viz. matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and MALDI Fourier transform ion cyclotron resonance (FTICR), and this makes it possible to perform imaging rapidly (MALDI-TOF) and with a very high selectivity (MALDI-FTICR).

Quantification of HIV protease inhibitors and non-nucleoside reverse transcriptase inhibitors in peripheral blood mononuclear cell lysate using liquid chromatography coupled with tandem mass spectrometry

For pharmacokinetic monitoring, measurement of antiretroviral agents in plasma is the gold standard. However, human immunodeficiency virus protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) exert their action within the infected cell. Cell-associated concentrations may therefore more adequately reflect therapy outcome. Therefore, for the quantification of nine PIs (amprenavir, atazanavir, darunavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir and tipranavir), 1 active PI metabolite (nelfinavir M8) and 2 NNRTIs (efavirenz and nevirapine) in lysate of peripheral blood mononuclear cells (PBMCs) an assay was developed and validated, using liquid chromatography coupled with tandem mass spectrometry. Analytes were extracted from a PBMC pellet by means of a one-step extraction with 50% methanol containing the internal standards D6-indinavir, D5-saquinavir, 13C6-efavirenz and dibenzepine. Chromatographic separation was performed on a reversed phase C18 column (150mmx2.0mm, particle size 5microm) with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.25mL/min. The analytical run time was 10min. The triple quadrupole mass spectrometer was operated in the positive ion-mode and multiple reaction monitoring was used for drug quantification. The method was validated over a range of 1-500ng/mL in PBMC lysate for all analytes. The method was proven to be specific, accurate, precise and robust. The mean precision and accuracy was less than +/-12% at all concentration levels. Using the developed assay and a previously developed assay for these analytes in plasma, the relationship between plasma and intracellular pharmacokinetics and their relationship with therapy outcome can now be determined.

Pharmacokinetic analysis to assess forgiveness of boosted saquinavir regimens for missed or late dosing

OBJECTIVES

One potential concern of once-daily protease inhibitor administration is low trough concentrations and ultimately the 'forgiveness' or robustness in comparison with the originally licensed twice-daily dose. To give an estimation of 'forgiveness', we determined the length of time plasma drug concentrations were below target in HIV-infected patients receiving saquinavir/ritonavir regimens.

METHODS

Seventy-seven pharmacokinetic profiles (saquinavir/ritonavir 1000/100 mg twice daily, n = 34; 1600/100 mg once daily, n = 26; 2000/100 mg once daily, n = 17) from five studies were combined, presented as twice- and once-daily percentiles (P10-P90) and compared. At percentiles where trough concentrations fell below the alleged minimum effective concentration (MEC; 100 ng/mL), the length of time below MEC was determined.

RESULTS

Saquinavir concentrations were below MEC at P10 for 0.7 h for twice-daily saquinavir/ritonavir when compared with 8.6 and 6.6 h for 1600/100 and 2000/100 mg once daily, respectively. At P25, 1600/100 mg once daily produced suboptimal concentrations for 5.5 h in contrast to 0.5 h for 2000/100 mg once daily.

CONCLUSIONS

Here, we provide substantive data that indicate once-daily saquinavir, in particular 1600/100 mg, is not as robust as the twice-daily regimen based on a population of UK patients; this raises concern over late or missed doses. However, pharmacokinetic data can only ever be a guide to the impact on long-term efficacy.

Antiretroviral drug concentrations and HIV RNA in the genital tract of HIV-infected women receiving long-term highly active antiretroviral therapy

OBJECTIVE

Our objective was to determine antiretroviral drug concentrations and human immunodeficiency virus (HIV) RNA rebound in cervicovaginal fluid (CVF) in relation to blood plasma (BP) in women receiving suppressive highly active antiretroviral therapy (HAART).

METHODS

Thirty-four HIV-infected women who had plasma HIV RNA levels < or =80 copies/mL for at least 6 months were enrolled. Sixty-eight paired CVF and BP drug concentrations and HIV RNA levels were determined before and 3-4 h after drug administration. For each woman and antiretroviral drug, the CVF:BP drug concentration ratios before and after drug administration were calculated. The nonparametric Wilcoxon rank sum test was used to determine if these ratios were different from 1.0.

RESULTS

Lamivudine (administered to 20 patients) and tenofovir (administered to 16) had significantly higher concentrations in CVF than in BP before drug administration, with mean CVF:BP concentration ratios of 3.19 (95% confidence interval, 1.2-8.5) and 5.2 (95% confidence interval, 1.2-22.6), respectively. Efavirenz (administered to 13 patients) and lopinavir (administered to 6) had significantly lower concentrations in CVF, with mean CVF:BP concentration ratios of 0.01 (95% confidence interval, 0.00-0.03) and 0.03 (0.01-0.11), respectively. During the study visit (median time after enrollment, 6 months), BP and CVF detectable HIV RNA levels were observed 7 patients (20.6%) and 1 patient (2.9%), respectively.

CONCLUSION

Despite lower CVF concentrations of key HAART components, such as efavirenz and lopinavir, virologic rebound was rare. The high concentrations of tenofovir and lamivudine in CVF may have implications for the prevention of sexual transmission during HAART and for pre-exposure or postexposure prophylaxis.

Current role of LC-MS in therapeutic drug monitoring

The role of liquid chromatography coupled with mass spectrometry (LC-MS) techniques in routine therapeutic drug monitoring activity is becoming increasingly important. This paper reviews LC-MS methods published in the last few years for certain classes of drugs subject to therapeutic drug monitoring: immunosuppressants, antifungal drugs, antiretroviral drugs, antidepressants and antipsychotics. For each class of compounds, we focussed on the most interesting methods and evaluated the current role of LC-MS in therapeutic drug monitoring.

Clinical and pharmacokinetic data support once-daily low-dose boosted saquinavir (1,200 milligrams saquinavir with 100 milligrams ritonavir) in treatment-naive or limited protease inhibitor-experienced human immunodeficiency virus-infected patients

We evaluated the plasma and intracellular pharmacokinetics, clinical efficacy, and safety of once-daily low-dose boosted saquinavir (SQVr; 1,200 of saquinavir [SQV] with 100 mg of ritonavir) plus two nucleotide reverse transcriptase inhibitors in treatment-naive or limited protease inhibitor (PI)-experienced human immunodeficiency virus (HIV)-infected patients. A prospective study without entry restrictions on the plasma HIV-RNA (VL) or CD4 cell count was carried out. Plasma and intracellular SQV levels were measured by high-performance liquid chromatography. Efficacy was evaluated by an intention-to-treat analysis; treatment failure was defined as virological failure (a VL of >50 copies/ml after 24 weeks or a confirmed rebound to >50 copies/ml) or interruption for any reason. A total of 151 patients were included in the study (106 of them either had never received PI or had no previous virological failure on PIs) and could be characterized as follows: previous C3 stage, 28.9%; injection-drug users, 69.1%; subjects with chronic viral hepatitis, 53%; and subjects with cirrhosis, 10%. The median baseline CD4 level was 184/mul, and the median VL was 4.8 log(10) copies/ml. Median C(max), area under the concentration-time curve from 0 to 24 h, and C(min) plasma and intracellular SQV levels were 3,672 and 10,105 ng/ml, 34,283 and 99,535 ng.h/ml, and 359 and 1,062 ng/ml, respectively. The efficacy as determined by intention to treat at 52 weeks was 69.7% (96% in the on-treatment analysis), with similar results regardless of the baseline VL and CD4 counts. Only five patients had virological failure despite adequate C(min) levels, but with a poor adherence (the only variable related to virological failure). Adverse events caused the withdrawal of the treatment in four patients (2.6%). In conclusion, given the pharmacokinetic profile, efficacy, and tolerability of this regimen, once-daily low-dose SQVr may be considered a treatment option in treatment-naive or limited PI-experienced HIV-infected patients, with the additional benefit of being currently the least-expensive PI-based regimen available.

Are Plasma Levels Valid Surrogates for Cellular Concentrations of Antiretroviral Drugs in HIV-infected Patients?

Total plasma concentrations are currently measured for therapeutic drug monitoring of HIV protease inhibitors (PIs) and nonnucleoside reverse transcriptase inhibitors (NNRTIs). However, the pharmacological target of antiretroviral drugs reside inside cells. To study the variability of their cellular accumulation, and to determine to which extent total plasma concentrations (TPC) correlate with cellular concentrations (CC), plasma and peripheral blood mononuclear cells (PBMCs) were simultaneously collected at single random times after drug intake from 133 HIV infected patients. TPC levels were analysed by high-performance liquid chromatography with ultraviolet detection and CC by LC-MS/MS from peripheral blood mononuclear cells. The best correlations between TPC and CC were observed for nelfinavir (NFV, slope=0.93, r=0.85), saquinavir (SQV, slope=0.76, r=0.80) and lopinavir (LPV, slope=0.87, r=0.63). By contrast, TPC of efavirenz (EFV) exhibited a moderate correlation with CC (slope=0.69, r=0.58), while no correlation was found for nevirapine (NVP, slope=-0.3, r=0.1). Interindividual variability in the CC/TPC ratio was lower for protease inhibitors (coefficients of variation 76%, 61%, and 80% for SQV, NFV and LPV, respectively) than for nonnucleoside reverse transcriptase inhibitors (coefficients of variation 101% and 318%, for EFV and NVP). As routine CC measurement raises practical difficulties, well-correlated plasma concentrations (ie, NFV, SQV and LPV) can probably be considered as appropriate surrogates for cellular drug exposure. For drugs such as EFV or NVP, there may be room for therapeutic drug monitoring improvement using either direct CC determination or other predictive factors such as genotyping of transporters or metabolizing enzyme genes.

Analysis of genotypic and phenotypic clinical cut-off levels for ritonavir-boosted saquinavir

There is a need for new, clinically relevant interpretation algorithms for genotypic and phenotypic resistance for ritonavir-boosted saquinavir (SQV/r) at the current approved dosage [1000/100 mg twice a day (bid)]. Clinical cut-off levels, which correlate baseline measures of resistance with HIV RNA responses in large cohorts or clinical trials, are the ideal reference for developing such algorithms. Cut-off levels previously developed for unboosted saquinavir may no longer apply, as the plasma drug levels with SQV/r are significantly higher and may be able partially to overcome protease inhibitor-resistant HIV. Clinical cut-off levels for SQV/r, assessed in several cohort studies and clinical trials, also suggest that multiple genotypic mutations are required for complete loss of virological response. For phenotypic analysis of resistance, saquinavir cut-off levels 10-11-fold higher than the wild-type IC50 have best distinguished responders from non-responders in cohort studies. Using Virtual Phenotype, a 12.3-fold upper cut-off level was determined from analysis of large cohort databases. These genotypic and phenotypic algorithms need to be validated in larger prospective studies.

Therapeutic Drug Monitoring and Human Immunodeficiency Virus (HIV) Antiretroviral Therapy

Treatment with antiretroviral drugs such as the HIV protease inhibitors and non-nucleoside reverse transcriptase inhibitors have contributed to the improvement of life of many HIV-infected patients in recent years, but antiretroviral therapy is not without problems. In some patients, treatment is not effective and suppression of viral replication is not achieved. Other patients experience toxicity and have to stop treatment or change to a less effective treatment. Several studies have demonstrated a relationship between plasma concentrations of the protease inhibitors and non-nucleoside reverse transcriptase inhibitors and viral suppression and toxicity. Therapeutic drug monitoring uses drug concentrations to individualize and optimise therapy by dosage adjustments and many clinicians have advocated for the use of therapeutic drug monitoring in HIV antiretroviral therapy. Evidence from a number of randomized clinical trials supports the use of therapeutic drug monitoring, but the studies have limitations and might not apply to all the antiretroviral drugs. However, the consensus is that certain patients are very likely to benefit from therapeutic drug monitoring. Additionally, the combination of therapeutic drug monitoring and genotypic or phenotypic resistance testing might further improve antiretroviral therapy.

Once-Daily Regimen of Saquinavir, Ritonavir, Didanosine, and Lamivudine in HIV-Infected Patients With Standard Tuberculosis Therapy (TBQD Study)

OBJECTIVES

To assess the efficacy and safety of a once-daily regimen with didanosine, lamivudine, saquinavir, and low-dose ritonavir in antiretroviral (ARV)-naive patients with tuberculosis treated with rifampin and the influence of rifampin on plasma trough concentration (Ctrough) of saquinavir.

METHODS

Single-arm, prospective, multicenter, open-label pilot study, including 32 adult ARV-naive subjects with HIV infection and tuberculosis under standard treatment that included rifampin (600 mg q.d.) and isoniazid (300 mg q.d.). After 2 months of tuberculosis treatment, patients were started on once-daily ARV therapy, consisting of didanosine, lamivudine, ritonavir (200 mg), and saquinavir soft gel capsules (1600 mg). HIV RNA level, CD4 cell count, clinical and laboratory toxicity, and saquinavir Ctrough during and after antituberculosis therapy were analyzed.

RESULTS

After 48 weeks of follow-up, 20 of 32 patients (62.5%; 95% CI: 45.8% to 79.2%) in the intent-to-treat population and 20 of 28 (71.4%; 95% CI: 54.4% to 88.4%) in the on-treatment population had an HIV RNA level <50 copies/mL. Treatment tolerance was acceptable in all patients except for 2 with biologic hepatic toxicity leading to discontinuation. Seven patients had virologic failure. In 10 patients (36%), saquinavir Ctrough was <0.05 microg/mL during tuberculosis therapy and 5 of them had virologic failure. The median saquinavir Ctrough was 44% lower (interquartile range: 19% to 71%) with coadministration of rifampin than without.

CONCLUSION

The combination of didanosine, lamivudine, saquinavir, and ritonavir may be a useful treatment regimen for patients with tuberculosis in whom a once-daily protease inhibitor-containing regimen is considered indicated. Nevertheless, on the basis of pharmacokinetic profile the dose of 1600/200 mg of saquinavir/ritonavir cannot be recommended. Further studies with higher doses of saquinavir (2000 mg) boosted with ritonavir are warranted.

Once-daily antiretroviral therapy: Spanish Consensus Statement

BACKGROUND

Administration of antiretroviral therapy (ART) once daily is creating extraordinary interest among the members of the scientific community and also among those who receive the therapy. However, in clinical practice, some doubts remain about its use.

OBJECTIVES

This document examines the characteristics and possibilities of treatment administered once daily.

METHODS

Consensus of 248 Spanish experts in the field.

RESULTS

Once-daily dosing is considered an added value which could favour adherence and, therefore, efficacy, as well as the quality of life of certain patients, however, the objective of adequate adherence in the long term is often difficult to achieve regardless of the treatment used. In theory, any patient can receive once-daily therapy, although some patients could particularly benefit from it, e.g. those with unfavourable social or personal circumstances, including drug users, patients whose treatment must be supervised, patients receiving multiple medications, or those who need rescue therapy after multiple treatment failures. At present, it is possible to design once-daily ART using some of the combinations of drugs considered as first-choice in national and international recommendations for antiretroviral therapy, but the options are still limited. The marketing of new drugs with this characteristic could allow us to increase the number and types of patient who can benefit from once-daily regimens, including those patients who need rescue therapy.

CONCLUSIONS

Once-daily ART is a good alternative to regimens administered several times each day when a potent combination of active drugs is available.

Intracellular and plasma pharmacokinetics of efavirenz in HIV-infected individuals

OBJECTIVES

The site of action of efavirenz is inside HIV-infected cells. Measurement of intracellular (IC) concentrations of efavirenz may therefore provide further understanding of therapeutic failure, especially where virological rebound occurs despite adequate plasma levels, and a lack of detectable viral resistance. Here, we determined IC and plasma pharmacokinetics of efavirenz and their relationship with plasma protein binding and P-glycoprotein (P-gp, an active drug efflux transporter) expression.

PATIENTS AND METHODS

Venous blood samples from 10 HIV-infected patients receiving efavirenz (600 mg once a day plus two nucleoside reverse transcriptase inhibitors) were collected over the 24 h dosing interval. Plasma and peripheral blood mononuclear cells (PBMCs) were isolated. Plasma protein bound and unbound efavirenz were separated using ultrafiltration. IC (or cell-associated), total plasma and unbound plasma efavirenz levels were quantified using HPLC-UV. P-gp expression was measured by flow cytometry. Area under the concentration-time curves (AUC0-24) were then calculated using non-compartmental analyses and the IC accumulation expressed as a ratio of IC to plasma AUC0-24.

RESULTS

The median (range) % unbound and IC accumulation ratio was 0.6% (0.4-1.5%) and 1.3 (0.7-3.3), respectively. There was a linear relationship between IC and total AUC0-24 (r2= 0.59, P = 0.01) but not unbound AUC0-24 (r2= 0.13, P = 0.75). An inverse correlation between IC AUC0-24 and % unbound was observed (r2= 41, P = 0.05). There was no relationship between IC AUC0-24 and P-gp expression on the cell surface (r2< 0.01, P = 0.98).

CONCLUSIONS

There was a direct relationship between % bound efavirenz in plasma and IC accumulation implying that the IC accumulation of efavirenz is related to binding to IC proteins or other cellular constituents. Studies investigating the unbound concentration of antiretrovirals inside the cell are now required.

A Prospective Study of Efficacy and Safety of Once-Daily Saquinavir/Ritonavir plus Two Nucleoside Reverse Transcriptase Inhibitors in Treatment-Naive Thai Patients

Objective

To assess the efficacy and safety of first-line treatment with once-daily saquinavir/ritonavir with two nucleoside reverse transcriptase inhibitors (NRTIs), as induction therapy before enrollment in a randomized trial of structured treatment interruption strategies.

Design

Two-hundred antiretroviral-naive patients with CD4+ cell counts between 200–350 at screening were enrolled in this open-label 24week study.

Methods

Patients were followed up every 8 weeks for CD4+ cells, HIV RNA, and clinical and laboratory toxicities. Results: Two-hundred patients were enrolled with median baseline CD4+ cell count of 267 cells/μl and HIV RNA 50 118 (4.7 log10) copies/ml. After 24 weeks of treatment, 191 of 200 (96%) patients had below 400 copies/ml HIV RNA, with 177/200 (89%) below 50 copies/ml (intent to treat, missing equals failure method), with a median rise in CD4+ cell count of 122 cells/μl. There was no significant correlation between the minimum concentration of saquinavir and HIV RNA reductions at week 8 ( P=0.957) or absolute HIV RNA at week 24 ( P=0.77).

Conclusion

First-line highly active antiretroviral therapy (HAART) with once-daily saquinavir/ritonavir plus two NRTIs showed strong antiviral efficacy over 24 weeks, and should be evaluated in larger prospective randomized clinical trials.

Bioanalysis of HIV protease inhibitors in samples from sanctuary sites

The human immunodeficiency virus (HIV) is present in several sites inside the human body, which are hardly accessible to antiretroviral drugs, the so-called sanctuary sites. The most important sanctuary sites are cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMCs) and seminal plasma. The determination of drug concentrations in these sanctuary sites may form an important step in treatment optimisation of HIV-infected individuals. However, bioanalysis in these sites is hampered by several factors with regard to sample preparation, chromatography and detection. In this review, we will discuss these issues and give an overview of published methods using high-performance liquid chromatography (HPLC) for the bioanalysis of HIV protease inhibitors in CSF, PBMCs and seminal plasma.

Intracellular measurements of anti-HIV drugs indinavir, amprenavir, saquinavir, ritonavir, nelfinavir, lopinavir, atazanavir, efavirenz and nevirapine in peripheral blood mononuclear cells by liquid chromatography coupled to tandem mass spectrometry

A sensitive and accurate liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the intracellular determination of nine antiretroviral drugs in human peripheral blood mononuclear cells (PBMCs) is proposed. PBMCs are isolated by density gradient centrifugation using Vacutainer CPT tubes and cell count is performed with a Coulter instrument. Single-step extraction of drugs from PBMCs pellets is performed with MeOH 50% (with clozapine added as internal standard, I.S.) and the supernatant is injected onto a 2.1 mm x 30 mm SymmetryShield 3.5 microm-RP18 column equipped with a 2.1 x 10 mm guard column. Chromatographic separations are performed using a gradient program with a mixture of 2 mM ammonium acetate containing 0.1% formic acid and acetonitrile with 0.1% formic acid. Analytes quantification is performed by electro-spray ionisation-triple quadrupole mass spectrometry using the selected reaction monitoring (SRM) detection mode. The positive mode is used for the HIV protease inhibitors (PIs) indinavir, amprenavir, saquinavir, ritonavir, nelfinavir, lopinavir, atazanavir and the non-nucleoside reverse transcriptase inhibitors (NNRTIs) nevirapine, and the negative mode is applied for efavirenz. The calibration curves are prepared using blank PBMCs spiked with antiretroviral drugs at concentrations ranging from 0.5 to 100 ng/ml of cell extracts and fitted to a quadratic regression model weighted by 1/(concentration)(2). The lower limit of quantification is less than 0.5 ng/ml. The mean extraction recovery for all PIs/NNRTIs is always above 88%. The method is precise, with mean inter-day CV% within 0.6-10.2%, and accurate (range of inter-day deviation from nominal values -7.2 to +8.3%). This analytical method can be conveniently used in clinical research for the assessment of intracellular levels of all PIs/NNRTIs commercially available at present using a simple one-step cell extraction of PBMCs followed by liquid chromatography coupled with tandem triple quadripole mass detection.