Steady-state pharmacokinetics of atazanavir given alone or in combination with saquinavir hard-gel capsules or amprenavir in HIV-1-infected patients

OBJECTIVE

The aim of this pilot study was to examine the pharmacokinetics of atazanavir (ATV) when given in combination with amprenavir (APV) or saquinavir hard-gel capsules (SQV) to human immunodeficiency virus (HIV)-positive patients.

METHODS

Included in the study were 34 HIV-infected patients enrolled in the ATV Early Access Program, who were treated with unboosted ATV alone (group 1) or with the double protease inhibitor combinations, ATV plus APV (group 2) or ATV plus SQV (group 3). ATV was given at a daily dose of 400 mg q.d. with the morning meal with SQV 1200 mg per day or APV 1200 mg per day. Serial blood samples for steady-state ATV pharmacokinetics were collected before the morning dose and at 1, 2, 3, 6, 8 and 24 h post-dosing. ATV plasma concentrations were measured using a high-performance liquid chromatography method with ultraviolet detection.

RESULTS

Of the patients, 12 received ATV as a single protease inhibitor; 12 received ATV in combination with APV; and 10 in combination with SQV. Geometric mean (coefficient of variation) ATV C(trough) was 110 ng/ml (2.38), 86 ng/ml (0.84) and 149 ng/ml (2.01) in groups 1, 2 and 3, respectively. ATV C(trough) in both double protease inhibitor combination regimens was not significantly different from that as a single protease inhibitor [geometric mean ratio (GMR): 0.77; 95% confidence interval (CI): 0.38-1.58, P=not significant for group 2 versus group 1 and 1.34, 0.40-4.49, P=not significant, for group 3 versus group 1). Patients treated with ATV plus APV had a 40.2% lower ATV C(max) and a 30.8% smaller ATV AUC than the reference group treated with unboosted ATV alone: both these differences were statistically significant (GMR, 95% CI: 0.59, 0.41-0.85, P=0.005 and 0.69, 0.48-0.99, P=0.056, respectively). No difference was observed for either C(max) or AUC between the group treated with ATV plus SQV and the reference group (GMR, 95% CI: 0.78, 0.47-1.30, P=not significant and 1.24, 0.73-2.10, P=not significant, respectively).

CONCLUSION

ATV pharmacokinetics does not seem to be influenced by the concomitant administration of SQV, whereas APV significantly lowers plasma ATV levels.

HIV leucoencephalopathy and TNFalpha expression in neurones

BACKGROUND

Human immunodeficiency virus (HIV) leucoencephalopathy (HIVL) is an uncommon and rapidly progressive form of AIDS dementia complex (ADC) that has remained poorly understood. Tumour necrosis factor alpha (TNFalpha), which has been implicated in the pathogenesis of ADC, is predominantly localised in macrophages in the HIV infected brain, although in vitro studies indicate that neurones can express this cytokine.

OBJECTIVE

To examine the clinical/neuroradiological features of HIVL and the expression of TNFalpha in HIVL.

METHODS

Six patients who presented with rapidly progressive dementia within four to 12 weeks of the primary manifestation of their HIV infection were evaluated. Clinical history, treatment regimens, and imaging studies were reviewed, and brain samples from three of the patients were studied by means of immunohistochemistry.

RESULTS

Imaging studies showed diffuse bilateral deep white matter changes in all six patients. Clinical and imaging abnormalities improved in five of the six patients within weeks after initiation of antiretroviral treatment. Brain biopsies of two showed pronounced microglia/macrophage activation, but only scant viral protein (gp41) expression. Staining for TNFalpha was found in microglia/macrophages, and surprisingly, in neurones also. Postmortem analysis of a third patient also showed TNFalpha expression in neurones of the frontal cortex and basal ganglia.

CONCLUSION

This study provides the first demonstration of staining for TNFalpha in the neurones of the HIV infected brain, and suggests that the process underlying this rapidly progressive form of ADC may reflect indirect mechanisms mediated by host factors, particularly TNFalpha.

Pharmacokinetics of saquinavir hard gel/ritonavir (1000/100 mg twice daily) when administered with tenofovir diproxil fumarate in HIV-1-infected subjects

AIMS

To investigate whether the administration of tenofovir diproxil fumarate 300 mg once daily alters the plasma pharmacokinetics of the saquinavir hard gel/ritonavir combination in HIV-1 infected individuals.

METHODS

On day 1, 12 h pharmacokinetic profiles for saquinavir/ritonavir (1000/100 mg given twice daily) were obtained for 18 subjects. All subjects were receiving ongoing treatment with a saquinavir/ritonavir-containing regimen. Tenofovir diproxil fumarate 300 mg given once daily was then added to the regimen and blood sampling was repeated at days 3 and 14. Saquinavir and ritonavir concentrations were measured by HPLC-MS/MS, and tenofovir concentrations by HPLC with UV detection.

RESULTS

Following the addition of tenofovir diproxil fumarate to the regimen, saquinavir and ritonavir plasma concentrations were not significantly different compared with day 1. Thus the geometric mean ratios (95% confidence intervals) for the area under the concentration-time curve were 1.16 (0.97, 1.59) and 0.99 (0.87, 1.30) for saquinavir and 1.05 (0.92, 1.28) and 1.08 (0.97, 1.30) for ritonavir, on days 3 and 14, respectively.

CONCLUSIONS

Tenofovir diproxil fumarate did not alter the pharmacokinetics of saquinavir hard gel/ritonavir.

Atazanavir plus ritonavir or saquinavir, and lopinavir/ritonavir in patients experiencing multiple virological failures

OBJECTIVE

To evaluate atazanavir/ritonavir (ATV/RTV) (300/100 mg) once daily, atazanavir/saquinavir (ATV/SQV) (400/1200 mg) once daily, and lopinavir/ritonavir (LPV/RTV) (400/100 mg) twice daily, each with tenofovir (300 mg) once daily and a nucleoside reverse transcriptase inhibitor in treatment-experienced HIV-infected patients.

METHODS

Randomized, open-label, 48-week multicenter trial of 358 randomized adult patients who had failed two or more prior HAART regimens with baseline HIV RNA > or = 1000 copies/ml and CD4 cell count > or = 50 x 10(6) cells/l.

RESULTS

The primary efficacy endpoint [plasma HIV RNA reduction assessed by time-averaged difference (TAD)] was similar for ATV/RTV and LPV/RTV [TAD 0.13; 97.5% confidence interval, -0.12 to 0.39] at 48 weeks. Mean reductions from baseline for ATV/RTV and LPV/RTV were comparable at 1.93 and 1.87 log10 copies/ml, respectively. Mean CD4 cell count increases were 110 and 121 x 10(6) cells/l for ATV/RTV, and LPV/RTV, respectively. The efficacy of ATV/SQV was lower than LPV/RTV by both these parameters. Declines in total cholesterol and fasting triglycerides were greater with ATV/RTV and ATV/SQV than with LPV/RTV (P < or = 0.005). Lipids in the LPV/RTV arm at week 48 generally increased from baseline. Lipid-lowering agents were used more frequently in the LPV/RTV arm than in the ATV arms (P < 0.05 versus ATV/RTV), as were antidiarrheal agents (P < or = 0.04 versus both ATV treatments). No new or unique safety findings emerged.

CONCLUSIONS

ATV boosted with RTV is as effective and well tolerated as LPV/RTV in treatment-experienced patients, with a more favorable impact on serum lipids. Pharmacokinetically enhanced ATV provides a suitable choice for therapy of treatment-experienced HIV-infected patients.

Synthesis of poly(ethylene glycol)-based saquinavir prodrug conjugates and assessment of release and anti-HIV-1 bioactivity using a novel protease inhibition assay

Various poly(ethylene glycol)(PEG)-based prodrug conjugates of the HIV-1 protease inhibitor (PI) saquinavir (SQV) were prepared using several types of chemical groups potentially capable of modifying its pharmacokinetic properties. These prodrug conjugates included SQV-cysteine-PEG3400, SQV-cysteine-PEG3400-biotin, SQV-cysteine(R.I.CK-Tat9) [a cationic retro-inverso-cysteine-lysine-Tat nonapeptide]-PEG3400, and SQV-cysteine(R.I.CK(stearate)-Tat9)-PEG3400. SQV was linked to cysteine to form a releasable SQV-cysteine ester bond in all of the conjugates. The amino group of the cysteine moiety provided an attachment site for a slower-degrading amide bond with N-hydroxysuccinimide-activated forms of PEG- and PEG-biotin. Disulfide bonds were used to attach the cationic peptides, R.I.CK-Tat9 and R.I.CK(stearate)-Tat9 to the cysteine moiety in order to provide cell-specific release. An assay was established and validated for measuring the activity of SQV and other protease inhibitors in biological samples. In this assay, cleavage of an internally quenched fluorescent substrate, Arg-Glu(EDANS)-Ser-Gln-Asn-Tyr-Pro-Ile-Val-Gly-Lys(DABCYL)-Arg by HIV-1 protease was inhibited by SQV in a dose-dependent manner at concentrations of 0.05-0.5 microM. All prodrug conjugates were shown to be inactive in this assay until the ester bond was cleaved and active SQV was released. The prodrug reconversion half-lives in 0.1 N HCl, phosphate-buffered saline (PBS) at pH 7.4 and in spiked plasma at 37 degrees C were 9, 14, and 0.9 h, respectively. The anti-HIV-1 activity (ED(50)) of the PEG-based SQV prodrug conjugates was evaluated in MT-2 cells using an MTT assay. The activity of conjugated SQV was reduced (ED(50) = 900 nM) for the PEG only conjugate, but restored with the addition of biotin (ED(50) = 125 nM), R.I.CK-Tat9 (ED(50) = 15 nM), and R.I.CK(stearate)-Tat9 (ED(50) = 62 nM) as compared to maximum achievable anti-HIV-1 activity (unconjugated SQV, control, ED(50) = 15 nM), suggesting enhanced cellular uptake of conjugates. Cytotoxicity (LD(50)) was assessed for all prodrug conjugates using non-HIV-1 infected cells and was found to be in the micromolar range. The difference between the LD(50) and ED(50) suggests a favorable therapeutic index for the prodrug conjugates. In conclusion, these promising initial results demonstrate that the reconversion of the conjugate prodrugs was complete and that active SQV was released. Since the major delivery advantages of PEG prodrug conjugates can only be observed in vivo, issues of reconversion and elimination half-lives in plasma will have to be further studied in an in vivo model. The current results also demonstrate that the protease inhibition assay is a simple yet effective bioanalytical tool that can be used to assess the release and anti-HIV-1 activity of HIV-1 PIs from their prodrug forms.

Boosted saquinavir hard gel formulation exposure in HIV-infected subjects: ritonavir 100 mg once daily versus twice daily

OBJECTIVES

The amount of ritonavir needed to enhance saquinavir hard gel (hg) plasma concentrations is unclear. Reduced ritonavir dosing may help to reduce ritonavir-related side effects and costs. This study examined the pharmacokinetics of twice-daily saquinavir-hg (1000 mg) in the presence of ritonavir 100 mg, dosed twice-daily and once-daily on one single occasion.

METHODS

Eighteen HIV-infected adults taking saquinavir/ritonavir 1000/100 mg twice-daily underwent pharmacokinetic (PK) assessment of saquinavir/ritonavir on day 1 following a morning saquinavir/ritonavir dose. On day 2, PK assessment was repeated when subjects took saquinavir without ritonavir. Drug intake (with a standard meal containing 20 g of fat) was timed on days -1, 1 and 2. Geometric mean ratios (GMR) and 95% confidence intervals (CI) were calculated to assess changes in saquinavir PK parameters.

RESULTS

Geometric mean saquinavir AUC(0-12), C(trough), C(max) and elimination half-life on days 1 and 2 were 14 389 and 9590 ng.h/mL, 331 and 234 ng/mL, 2503 and 1893 ng/mL and 2.80 and 2.82 h, respectively. The GMR (95% CI) for these parameters were 0.67 (0.53-0.84), 0.71 (0.48-1.04), 0.76 (0.58-0.98) and 1.01 (0.86-1.18), respectively.

CONCLUSIONS

Withholding a ritonavir dose significantly reduces overall saquinavir exposure and C(max), but had no impact on the elimination half-life. These data establish the need to administer saquinavir and ritonavir simultaneously.

The 48-week efficacy of once-daily saquinavir/ritonavir in patients with undetectable viral load after 3 years of antiretroviral therapy

OBJECTIVES

To evaluate the efficacy and safety of once-daily saquinavir-soft-gel-capsules/ritonavir (SQV-SGC/RTV) 1600 mg/100 mg plus dual nucleoside reverse transcriptase inhibitors (NRTIs) in HIV-infected patients with plasma viral load (pVL) <50 HIV-1 RNA copies/mL following 3 years of antiretroviral therapy.

METHODS

A total of 69 patients with pVL <50 copies/mL after 162 weeks of antiretroviral treatment started SQV-SGC/RTV 1600 mg/100 mg once-daily while continuing dual NRTIs. Previous treatment consisted of 66 weeks of treatment with a half/full dose of zidovudine (ZDV)/zalcitabine (ddC), followed by 2 years of SQV-SGC twice a day (bid) plus ZDV/lamivudine (3TC) or didanosine (ddI)/stavudine (d4T). Efficacy (pVL), safety and immunological changes (CD4 cell counts) were evaluated after 48 weeks in this open-label, single-arm prospective study.

RESULTS

SQV-SGC/RTV once-daily was well tolerated. No patient changed regimens or was lost to follow-up. After 48 weeks, 63 of 69 patients (91%) had pVL <50 copies/mL (five of the six remaining patients had pVL <400 copies/mL, and one patient had an unexplained rise to 39 500 copies/mL, which decreased to <50 copies/mL 12 weeks later). Median CD4 count increased from 534 cells/muL at the start of the SQV-SGC/RTV once-daily treatment to 664 cells/muL (P<0.001). Compared to the preceding 48 weeks on bid SQV-SGC, the CD4 cell count improved significantly on once-daily SQV-SGC/RTV (P<0.001).

CONCLUSIONS

These data support the use of SQV-SGC/RTV 1600 mg/100 mg once-daily with two NRTIs as a convenient, safe and cost-saving regimen to maintain viral suppression and CD4 counts for 48 weeks in this preselected cohort on highly active antiretroviral therapy (HAART) with pVL <50 copies/mL. The CD4 count rise may be a result of continued immune reconstitution in patients with well-controlled infection.

Short-course induction with boosted saquinavir monotherapy for naive patients with late-stage infection

This study assessed the efficacy of short-course induction treatment with saquinavir/ritonavir as boosted protease inhibitor monotherapy in antiretroviral-naive patients, before switching to conventional highly active antiretroviral therapy. Twenty-eight patients were enrolled, with baseline CD4 cell counts of 26 cells/microl and HIV RNA 5.5 log10 copies/ml. There was a median 2.5 log10 reduction in HIV RNA and 115 cell increase in CD4 cell counts after 4-8 weeks of saquinavir/ritonavir monotherapy. This treatment strategy should be evaluated further.

A randomized trial to evaluate lopinavir/ritonavir versus saquinavir/ritonavir in HIV-1-infected patients: the MaxCmin2 trial

OBJECTIVE

To assess the rate of protocol-defined treatment failure and safety of lopinavir/ritonavir (LPV/r) and saquinavir/ritonavir (SAQ/r).

DESIGN

Open-label, prospective, randomized (1:1), international multi-centre trial.

METHODS

Adult HIV-1-infected patients were assigned LPV/r 400/100 mg twice daily or SAQ/r 1000/100 mg twice daily with two or more nucleoside reverse transcriptase inhibitors (NRTIs)/non-NRTIs. All patients, whether on or off the assigned treatment, were followed for 48 weeks.

RESULTS

Of 339 randomized patients, 324 initiated assigned treatment (intention-to-treat/exposed [ITT/e] population). At 48 weeks, treatment failure occurred in 29/163 (18%) and 53/161 (33%) of patients in the LPV/r and SAQ/r arms, respectively (ITT/e, P = 0.002, log rank test). In an analysis that also considered those patients who discontinued treatment as having failed treatment (ITT/e/discontinuation = failure), 40/161 (25%) LPV/r-treated individuals versus 63/161 (39%) SAQ/R-treated individuals failed treatment (P = 0.005, log rank test). Discontinuation of the assigned treatment occurred in 23/163 (14%) patients in the LPV/r-treated group, compared with 48/161 (300%) in the SAQ/r-treated group (ITT/e; P = 0.001). The primary reasons for premature discontinuation were non-fatal adverse events (LPV/r: 12/163; SAQ/r: 21/161) and patients' choice (LPV/r: 7/163; SAQ/r: 8/161). In the on-treatment analysis of time to treatment failure, no difference was observed between the two arms (P = 0.27, log rank test).

CONCLUSION

LPV/r had better antiretroviral effects compared with SAQ/r at the doses and in the formulations studied. This may have been a result of patients' preferences and ability to adhere to assigned therapy, rather than a result of differences in the intrinsic potency of the study protease inhibitors.

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/microl and HIV RNA 50 118 (4.7 log10) copies/mi. 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/microl. 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.

Saquinavir 500 mg film-coated tablets demonstrate bioequivalence to saquinavir 200 mg hard capsules when boosted with twice-daily ritonavir in healthy volunteers

OBJECTIVE

To establish the bioequivalence of a 500 mg film-coated tablet of saquinavir mesylate (FCT SQV) to the 200 mg hard-capsule saquinavir mesylate (HC SQV), both boosted with ritonavir and administered under fed conditions.

METHODS

We carried out a multi-centre, open-label, randomized, two-sequence, four-period, two-treatment, replicated crossover study in 93 healthy men and 7 healthy women. Individuals were randomly assigned to receive sequential single doses of saquinavir in one of two treatment sequences: ABAB or BABA. Individuals received 100 mg ritonavir twice daily for 24 days. On days 14,17, 20 and 23, study participants took 1000 mg of HC SQV (five 200 mg capsules, treatment A) or FCT SQV (two 500 mg tablets, treatment B) with a high-fat, high-calorie breakfast, and pharmacokinetic analyses were carried out over the next 24 hours. Area under the saquinavir concentration-time curve (AUC0-alpha), maximum saquinavir plasma concentration (Cmax), time to Cmax and terminal half-life were calculated. The relative bioavailability of FCT SOV versus HC SQV was calculated as the ratio of the respective estimated mean saquinavir AUC0-alpha and Cmax. The calculation was based on an ANOVA including the factors site, sex, sequence, period, treatment and study participant to the log-transformed parameters log(AUC0-alpha) and log(Cmax); the relative bioavailability and the 90% confidence intervals (CIs) were estimated using the treatment contrasts of the ANOVA. Bioequivalence was concluded as for both parameters, AUC0-alpha and Cmax, the 90% CIs for the relative bioavailability were entirely included in the reference region [0.80-1.25].

RESULTS

Saquinavir plasma concentration-time profiles for the two formulations were similar. Geometric mean AUC0-alpha and Cmax values were clearly increased for FCT SQV (26 826 versus 24 430 h*ng/ml; and 3644 versus 3064 ng/ml, respectively); ratios of mean exposures were estimated to be 1.10 for AUC0-alpha and 1.19 for Cmax of saquinavir. However, the corresponding two-sided 90% CIs (1.04-1.16 and 1.14-1.25, respectively) all fell within the limits set for equivalence (0.80, 1.25). The adverse event profile for FCT SQV was similar to that for HC SQV.

CONCLUSION

The new 500 mg FCT SQV formulation is bioequivalent to the 200 mg HC SQV formulation, at the dose of 1000 mg, in combination with 100 mg ritonavir under fed conditions. The 500 mg FCT SQV formulation reduces pill count for boosted saquinavir (SQV/r) from six capsules to three tablets twice daily. This may increase patient acceptability of SQV/r, particularly in less treatment-experienced patients.

Steady-state pharmacokinetics of a double-boosting regimen of saquinavir soft gel plus lopinavir plus minidose ritonavir in human immunodeficiency virus-infected adults

Management of treatment-experienced human immunodeficiency virus patients has become complex, and therapy may need to include two protease inhibitors at therapeutic doses. The objective of this study was to characterize the pharmacokinetics in serum of saquinavir (1,000 mg twice daily [b.i.d.]), lopinavir (400 mg b.i.d.), and ritonavir (100 mg b.i.d.) in a multidrug rescue therapy study and to investigate whether steady-state pharmacokinetics of lopinavir-ritonavir are affected by coadministration of saquinavir. Forty patients were included (25 given ritonavir, lopinavir, and saquinavir and 15 given ritonavir and lopinavir). The median pharmacokinetic parameters of lopinavir were as follows: area under the concentration-time curve from 0 to 12 h (AUC(0-12)), 85.1 microg/ml . h; maximum concentration of drug in serum (C(max)), 10.0 microg/ml; trough concentration of drug in serum (C(trough)), 7.3 microg/ml; and minimum concentration of drug in serum (C(min)), 5.5 microg/ml. Lopinavir concentrations were similar in patients with and without saquinavir. The median pharmacokinetic parameters for saquinavir were as follows: AUC(0-12), 22.9 microg/ml . h; C(max), 2.9 microg/ml; C(trough), 1.6 microg/ml; and C(min), 1.4 microg/ml. There was a strong linear correlation between lopinavir and ritonavir and between saquinavir and ritonavir concentrations in plasma. The correlation between lopinavir and saquinavir levels was weaker. We found higher saquinavir concentrations in women than in men, with no difference in lopinavir levels. Only patients with very high body weight presented lopinavir and saquinavir concentrations lower than the overall group. Ritonavir has a double-boosting function for both lopinavir and saquinavir, and in terms of pharmacokinetics, the drug doses selected seemed appropriate for combining these agents in a dual protease inhibitor-based antiretroviral regimen for patients with several prior virologic failures.

Atazanavir: a new protease inhibitor to treat HIV infection

PURPOSE

The pharmacology, pharmacokinetics, and clinical trials of and drug interactions and formulary considerations associated with atazanavir, the newest protease inhibitor (PI) to treat human immunodeficiency virus (HIV) infection, are evaluated.

SUMMARY

Clinical and pharmacokinetic trials were identified through a MEDLINE search. In addition, all available literature citations and meeting abstracts were obtained from the drug's manufacturer. All articles identified from the data sources were evaluated, and all information deemed relevant was included in this review. Data on atazanavir for the treatment of HIV infection are limited to several phase II and III trials, one of which is still ongoing. Atazanavir has shown efficacy comparable with other PIs and the nonnucleoside reverse-transcriptase inhibitor efavirenz in reducing HIV RNA levels, increasing CD4+ lymphocyte counts, and increasing the percentage of patients achieving clinically undetectable HIV RNA levels when given as the sole PI in treatment-naive patients, in combination with saquinavir in treatment-experienced patients, and with ritonavir-boosting regimens in highly treatment-experienced patients. Treatment-naive patients receiving atazanavir commonly develop a protease enzyme mutation on codon 50, which decreases HIV's susceptibility to atazanavir but may increase the susceptibility of the virus to other PIs. When atazanavir is given to patients with preexisting PI-related mutations, the virus's susceptibility to atazanavir is greatly reduced. The occurrence of lipid abnormalities, which has been a major concern with previous PIs, has not been shown to be troublesome in patients receiving atazanavir.

CONCLUSION

Atazanavir may be used alone as a first-line PI, with saquinavir in treatment-experienced patients, or in combination with a ritonavir-boosting regimen in highly treatment-experienced patients as part of a salvage regimen.

Pharmacokinetic study of saquinavir hard gel caps/ritonavir in HIV-1-infected patients: 1600/100 mg once-daily compared with 2000/100 mg once-daily and 1000/100 mg twice-daily

OBJECTIVES

A pharmacokinetic comparison of three dosing regimens of saquinavir/ritonavir was carried out: 1600/100 mg once-daily with 1000/100 mg twice-daily, and 1600/100 mg once-daily with 2000/100 mg once-daily.

METHODS

Twenty patients on saquinavir hard gel caps/ritonavir 1600/100 mg once-daily in combination with two nucleoside reverse transcriptase inhibitors for at least 4 weeks were enrolled and randomized to either saquinavir hard gel caps/ritonavir 1000/100 mg twice-daily or 2000/100 mg once-daily. Two pharmacokinetic curves were plotted, at baseline (day 0) and 7 days after the switch. Plasma concentrations were measured at 0, 2, 4, 6, 8, 10, 12 (and 24 for once-daily dosing) hours after drug intake by validated high-performance liquid chromatographic assay (HPLC). The area under the plasma concentration-time curve (AUC0-24 or AUC0-12), maximum and minimum concentration (Cmax and Cmin) and elimination half-life were calculated using a non-compartmental model.

RESULTS

Compared with saquinavir/ritonavir 1600/100 mg once-daily dosing, the saquinavir AUC and Cmin improved significantly when dosed as 1000/100 mg twice-daily (53% and 299%, respectively), and as 2000/100 mg once-daily (71% and 65%, respectively). Low Cmin in three subjects at baseline was corrected after switch to the other dosages. Saquinavir/ritonavir 2000/100 mg once-daily was also associated with a significant increase in saquinavir Cmax (52%) compared with saquinavir/ritonavir 1600/100 mg once-daily.

CONCLUSIONS

Saquinavir/ritonavir when dosed as 2000/100 mg once-daily or 1000/100 mg twice-daily achieves higher saquinavir plasma levels compared with saquinavir/ritonavir 1600/100 mg once-daily. Taking the convenience of once-daily dosing into consideration, dosage of 2000/100 mg once-daily may be preferred.

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

Ritonavir-boosted saquinavir (SQV/r) is currently licensed as a twice-daily regimen. Reducing the pill burden with once-daily dosing may improve adherence. Intracellular concentrations of drugs must be related to the clinical efficacy of protease inhibitors. The aims of the study were to determine the cellular and plasma saquinavir and ritonavir concentrations, to determine the half-lives (t(1/2)s) of the drugs in each compartment, and to examine relationships between drug accumulation and lymphocyte subset P glycoprotein (P-gp) expression. Venous blood samples from 12 human immunodeficiency virus-infected patients receiving a hard-gel formulation of SQV/r (1,600/100 mg once daily) were collected at 2, 6, 12, and 24 h after dosing. Peripheral blood mononuclear cells were separated by density gradient centrifugation, and P-gp expression was measured by dual-color flow cytometry. Plasma and intracellular (cell-associated) drug concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. The ratio of the intracellular drug area under the concentration-time curve from 0 to 24 h (AUC(0-24 h)) to plasma drug AUC(0-24 h) was calculated to determine cellular drug accumulation. The median (range) AUC(0-24 h) of saquinavir in plasma was 16.2 (5.7 to 39.3) mg. h. liter(-1), and that in cells was 46.3 (24.7 to 114.6) mg. h. liter(-1). Corresponding ritonavir values were 7.5 (1.5 to 14.6) mg. h. liter(-1) and 10.4 (3.2 to 13.7) mg. h. liter(-1), respectively. The median accumulation ratios of cellular AUC to plasma AUC for saquinavir and ritonavir were 3.31 (range, 1.49 to 6.69) and 1.46 (range, 0.83 to 4.15), respectively. Significant differences between the plasma and intracellular saquinavir t(1/2)s (4.5 h [range, 2.5 to 9.3 h] and 5.9 h [range, 4.0 to 17.7 h]; P = 0.034) and between the plasma and intracellular ritonavir t(1/2)s (4.1 h [range, 2.6 to 8.3 h] and 6.2 h [range, 3.9 to 18.6 h]; P = 0.032) were observed. No relationship was observed between the accumulation of saquinavir or ritonavir and lymphocyte subset P-gp expression. The intracellular t(1/2)s of saquinavir and ritonavir were longer than the plasma t(1/2)s, indicating that intracellular drug may be available at a time when concentrations in plasma are below the minimum effective concentration.

Therapeutic dose of HIV-1 protease inhibitor saquinavir does not permanently influence early insulin signaling

The introduction of HIV-1 protease inhibitor therapy has significantly improved the expectancy and quality of life for HIV-infected patients. Recent reports have highlighted the development of metabolic complications in patients taking protease inhibitors, including abnormalities in glucose metabolism such as impaired glucose tolerance and type 2 diabetes. The mechanisms by which protease inhibitors induce these metabolic syndromes are not well understood. The aim of this study was to determine whether treatment with the HIV-1 protease inhibitor, saquinavir, influences the early insulin signaling cascade in insulin-sensitive cell lines.

METHODS

Insulin-stimulated phosphorylation of insulin receptor (IR-beta), insulin receptor substrates (IRS-1 and IRS-2), association of phosphatidylinositol 3-kinase (PI 3-kinase), Ser 473-phosphorylation of Akt and Thr202/Tyr204-phosphorylated p44/42 MAP kinase in 3T3L1 adipocytes and FAO hepatoma cells incubated with increasing concentrations of saquinavir for 24, 36 hours, 2, 3 and 6 days were measured. Results. Phosphorylation of IR-beta, IRS-1 and IRS-2 was not permanently affected by incubation with therapeutic doses (2.5 microM) of saquinavir for 36 hours. After 24 hours we observed an increase of IR-beta and IRS-1 phosphorylation. However, this initial stimulation of IR-beta and IRS-1 phosphorylation was not permanent and did not result in an increased PI 3-kinase association. Phosphorylation of IRS-2 and MAP kinase as well as glucose transport activity was not altered by therapeutic doses. Doses of 10, 25 and 50 microM of saquinavir altered the early insulin signaling events in a dose-dependent manner. However, this effect was primarily due to the cytotoxic effect of higher saquinavir doses. Glucose transport activity was not significantly reduced in 3T3L1 cells treated with 2.5 microM saquinavir in comparison to the control cells stimulated with insulin.

CONCLUSION

Early insulin signaling cascade, essential for normal glucose metabolism, is not affected by therapeutic doses of saquinavir. The reduction of insulin-induced phosphorylation in higher concentrations is primarily related to cytotoxic effects. Other mechanisms than early insulin signaling must be primarily responsible for the metabolic alterations during saquinavir therapy.