Antiretroviral effect of two different dose regimens of ritonavir and saquinavir on HIV-infected adults in a population-based setting

OBJECTIVE

To characterize the antiviral effect and tolerability of higher dose (HD, 600 mg two times daily) and lower dose (LD, 400 mg two times daily) combination regimens of ritonavir and saquinavir in British Columbia (BC), Canada.

DESIGN

Intent-to-treat analysis with suppression of plasma viral load to levels below 500 copies/ml as the main outcome measure.

PATIENTS

Adult human immunodeficiency virus (HIV)-positive individuals in the province of British Columbia prescribed ritonavir and saquinavir in combination between 1 September 1996 and 30 June 1997, with a minimum of two plasma viral loads, one at baseline and one after the initiation of therapy.

RESULTS

A total of 84 participants [27 HD (32%) and 57 LD (68%)] were prescribed ritonavir and saquinavir. There was no difference at baseline in the two groups with respect to age (P=0.466), CD4 cell count (P=0.373) and baseline plasma viral load (P=0.656). However, LD were more likely to have had prior protease experience than HD participants (65 versus 40%, P=0.037). The median follow-up time was 9 months. A total of 44 (52%) subjects demonstrated a decrease in plasma viral load to levels <500 copies/ml. After adjusting for length of follow-up, baseline CD4 cell count and prior AIDS diagnosis, HD participants were as likely to be suppressed to <500 copies/ml as LD individuals (P=0.760). HD participants did report more adverse effects (P=0.042) than LD subjects.

CONCLUSION

Our results provide confirmatory evidence that lower doses of ritonavir and saquinavir in combination are better tolerated and as effective as the standard doses of these drugs. This response, however, is seriously compromised by prior exposure to protease inhibitors.

Effect of simultaneous versus staggered dosing on pharmacokinetic interactions of protease inhibitors

OBJECTIVE

The aim of this study was to determine whether pharmacokinetic interactions between the protease inhibitors saquinavir soft gel, nelfinavir, and ritonavir are affected by the timing of administration.

STUDY DESIGN

We used an open-label, 6-period, incomplete Latin square crossover study in 18 human immunodeficiency virus-negative subjects. Each received single oral doses of 2 of the 3 protease inhibitors during each of 6 periods. Single doses were given either simultaneously or separated by 4 hours. The order of the periods was balanced, and periods were separated by 2 days. We measured protease inhibitor concentrations over a 24-hour period by HPLC and estimated pharmacokinetic parameters by noncompartmental methods.

RESULTS

Median saquinavir area under the curve (AUC) increased by 62-fold when ritonavir was coadministered, by 50-fold when ritonavir was given 4 hours earlier, and by 16-fold when saquinavir preceded ritonavir by 4 hours. Saquinavir AUC increased by 7-fold when nelfinavir was coadministered. Nelfinavir AUC increased by 2.5-fold with coadministration of ritonavir and by 1.8- and 2.1-fold when ritonavir was administered before nelfinavir and after nelfinavir, respectively. Ritonavir AUCs were unaffected by coadministration of the other drugs. The effect of ritonavir on the kinetics of saquinavir persisted for at least 48 hours after a single dose of ritonavir, suggesting the possibility of metabolic intermediates that form inhibitory complexes.

CONCLUSION

Except for saquinavir followed by ritonavir, there is little difference in protease inhibitor exposure for simultaneous or staggered doses. The persistent effect of ritonavir suggests the possibility that lower doses and longer dosing intervals might be effective when ritonavir is used to boost concentrations of other protease inhibitors.

Pharmacokinetic and tolerability profile of twice-daily saquinavir hard gelatin capsules and saquinavir soft gelatin capsules boosted with ritonavir in healthy volunteers

OBJECTIVE

To evaluate the pharmacokinetics and safety of a boosted saquinavir (SQV)/ritonavir (RTV) combination, administered as either the hard gelatin capsule (HGC) or soft gelatin capsule (SGC) formulation of SQV, in 24 healthy volunteers.

METHODS

This was a single-centre, open-label, randomized, 2 x 2 crossover study. Twelve subjects were randomized to receive SQV/RTV 1000 mg/100 mg twice daily (BID) orally for 10 days, as either the HGC or SGC formulation. The pharmacokinetic profile of SQV was determined on day 10. Subjects then crossed over to the opposite SQV formulation, and the pharmacokinetic profile was determined again on day 20. The primary analysis was the assessment of bioequivalence based on logarithmically transformed values for AUC(0-24 h) and Cmax for the two formulations.

RESULTS

There was a statistically significant increase in the geometric means of all the pharmacokinetic variables evaluated for SQV-HGC/RTV compared with SQV-SGC/RTV. A mean AUC0-24 h-value of 15.798 micro g/mL/h was reported for the HGC formulation compared with 11.655 micro g/mL/h for the SGC formulation (P = 0.0043). The SQV-HGC/RTV combination was better tolerated in terms of gastrointestinal system disorders. Furthermore, no elevations in triglycerides or total cholesterol were reported with SQV/RTV during the entire study period.

CONCLUSION

In healthy volunteers, RTV boosting of SQV-HGC produces plasma exposures at least comparable to SQV-SGC, which is accompanied by an improvement in gastrointestinal system disorders.

Pharmacokinetics of once-daily saquinavir hard-gelatin capsules and saquinavir soft-gelatin capsules boosted with ritonavir in HIV-1-infected subjects

OBJECTIVE

To investigate the pharmacokinetics of once-daily saquinavir (SQV) hard-gelatin capsule (HGC)/ritonavir (RTV), 1600/100 mg, compared with once-daily SQV soft-gelatin capsule (SGC)/RTV, 1600/100 mg.

METHODS

We evaluated 13 randomly selected HIV-1-infected subjects taking once-daily SQV SGC/RTV, 1600/100 mg, plus dual nucleoside reverse transcriptase inhibitors (NRTIs) in this pharmacokinetic (PK) substudy. Subjects took 1 week of SQV HGC/RTV and NRTIs, followed by steady-state SQV PK determinations. Subjects then changed to SQV SGC/RTV and NRTIs for 1 week, followed again by steady-state SQV PK determinations. Area under the plasma concentration versus time curve (AUC), maximum concentration (C(max)), minimum concentration (C(min)), time to C(max), and elimination half-life were calculated.

RESULTS

There was no significant difference in AUC values between HGCs and SGCs, with a median (plus interquartile range [IQR]) of 50.0 (42.6-71.5) versus 35.5 (28.0-50.2) mg/L/h, respectively ( =.056). Intersubject variability resulted in 4 of 13 subjects on the SQV SGCs and 2 of 13 subjects on the SQV HGCs having a C(min) below the minimum effective concentration of 0.05 mg/L.

CONCLUSION

Once-daily SQV HGCs, 1600 mg, boosted with once-daily RTV, 100 mg, resulted in PK parameters that were similar to those observed with 1600 mg of SQV SGC/100 mg RTV once daily. Once-daily SQV HGC/RTV, 1600/100 mg, may be easier to use in developing countries and may increase access where drug costs can be less, the capsule size is smaller, and the need for refrigeration is lessened.

Effect of indinavir on the intestinal exsorption of amprenavir, saquinavir and nelfinavir after intravenous administration in rats

To elucidate drug interaction between human immunodeficiency virus (HIV) protease inhibitors (PIs), the effect of indinavir (IDV) on the intestinal exsorption of other HIV PIs, amprenavir (APV), saquinavir (SQV) and nelfinavir (NFV) was investigated in rats using an in situ single perfusion method. IDV in the intestinal perfusate inhibited the exsorption of rhodamine 123 (Rho123), a known P-glycoprotein (P-gp) substrate, from blood into intestinal lumen in a concentration-dependent manner, and the inhibitory potency of 10 micro M IDV in the perfusate was close to that of 10 micro M cyclosporin A (CsA) in the perfusate. Ten micro M of IDV in the intestinal perfusate also decreased significantly the exsorption clearance of Rho123 after intravenous administration. The IDV concentration in this system was not likely to cause hepatic interaction between HIV PIs, because the plasma IDV concentration was far below its inhibition constants for other HIV PIs in the liver microsomes. Thus, 10 micro M of IDV was chosen to investigate the effect of this inhibition on the exsorption of APV, SQV and NFV. IDV in the intestinal perfusate markedly increased the exsorbed amounts of SQV and NFV but not APV after intravenous administrations. Their exsorption clearances, however, showed only a slight increasing tendency or remained unchanged. These findings suggest that in addition to P-gp inhibition, other factors such as CYP3A inhibition might be important in the drug interaction of IDV with APV, SQV and NFV after intravenous administration in rat small intestine. The results obtained in this study will provide useful information to discuss the interactions among PIs when a double protease therapy is used for in HIV-infected patients.

Long-term efficacy and safety of twice-daily saquinavir soft gelatin capsules (SGC), with or without nelfinavir, and three times daily saquinavir-SGC, in triple combination therapy for HIV infection: 100-week follow-up

OBJECTIVES

To evaluate the long-term efficacy and safety of saquinavir soft gelatin capsules (SQV-SGC) (Fortovase) in twice-daily, with or without nelfinavir (NFV), and three-times-daily regimens. This was an extension of a 48-week study, with follow-up to 100 weeks.

DESIGN

Patients were randomized to one of three treatment arms: arm A, SQV-SGC 1200 mg three times daily plus two nucleoside reverse transcriptase inhibitors (NRTIs); arm B, SQV-SGC 1,600 mg twice daily plus two NRTIs; or arm C, SQV-SGC 1200 mg twice daily plus NFV 1250 mg twice daily plus one NRTI. At week 48, patients could either withdraw or continue in the study to the common study closure date. Antiretroviral activity was assessed by changes in HIV-1 RNA values and CD4 cell counts from 48 weeks until 100 weeks.

RESULTS

In the modified intention-to-treat population, the proportion of patients with HIV-1 RNA values <400 copies/ml was statistically different between arms A and C (49 vs 28%, P=0.017), and arms B and C (48 vs 28%, P=0.027). Continued suppression of HIV-1 replication (HIV-1 RNA <400 copies/ml) was observed through 100 weeks in 83% (30/36), 73% (29/40) and 62% (16/26) of patients in treatment arms A, B and C, respectively, in the on-treatment (OT) population. At 100 weeks, sustained increases were achieved in mean CD4 cell counts of +361, +273 and +309 cells/mm3, respectively (OT population). No additional adverse events or increase in the proportion of patients reporting adverse events were observed from 48 weeks to 100 weeks.

CONCLUSIONS

This study demonstrates the long-term efficacy and safety of SQV-SGC twice daily, with or without NFV, and three times daily, in triple combination therapy for HIV-1-infected patients. However, the evidence suggests that long-term treatment with SQV-SGC plus NFV may be less acceptable to patients.

Saquinavir/low-dose ritonavir: its use in HIV infection

Exposure to saquinavir can be increased considerably by pharmacokinetic enhancement with ritonavir, without having a substantial impact on tolerability. Clinical trials indicate that both once-daily and twice-daily saquinavir/ritonavir treatment regimens, generally at dosages of 1,600 mg/100 mg once daily and 1,000 mg/100 mg twice daily, provide potent and sustained viral suppression and are well tolerated. In addition, data suggest that "double-boosting" strategies, including the combination of saquinavir with lopinavir/ritonavir, provide valuable treatment options in the salvage setting.

Pharmacokinetics of saquinavir co-administered with cimetidine

The present study evaluated the effect of cimetidine, a histamine H(2) receptor antagonist able to inhibit cytochrome P450 metabolism, on the steady-state pharmacokinetics of saquinavir soft gel. Twelve healthy volunteers (eight males and four females) participated in an open-label, double-phase pharmacokinetic study. Volunteers took saquinavir soft gel 1200 mg three times a day for 13 days and then saquinavir soft gel 1200 mg twice a day with cimetidine 400 mg twice a day from day 14 to 26. The pharmacokinetics of saquinavir on days 13 and 26 were compared. All 12 volunteers completed the study. The association of cimetidine with saquinavir soft gel 1200 mg twice a day resulted in a significant increase in saquinavir AUC(0-24) (120%; P = 0.023) and C(max) (179%; P = 0.019), whereas C(trough) did not differ significantly (32% increase; P = 0.272). Increased exposure to saquinavir was observed in healthy volunteers after co-administration with cimetidine. The most significant increase involved C(max). Further pharmacokinetic studies in HIV-infected subjects are warranted to confirm the boosting effect of cimetidine and to investigate any impact that the increase in saquinavir C(max) may have on intracellular accumulation of the drug.

Model-based analysis of the pharmacokinetic interactions between ritonavir, nelfinavir, and saquinavir after simultaneous and staggered oral administration

Eighteen healthy human immunodeficiency virus-negative subjects participated in an open-label, six-period, incomplete Latin-square crossover pharmacokinetic study. Each subject received two of the three possible pair-wise combinations of single-dose oral ritonavir (R) (400 mg), nelfinavir (N) (750 mg), and saquinavir (S) (800 mg), each pair on three occasions (simultaneous or staggered administration), each occasion at least 2 days after the last. A model-based analysis reveals the following major drug interactions under the conditions of this study: 1). R given simultaneously with S decreases S hepatic intrinsic clearance almost 50-fold relative to that predicted for S given alone and increases its gut bioavailability 90% (but decreases its rate of absorption 40%) relative to when N is given simultaneously; 2). N given simultaneously with S decreases S hepatic intrinsic clearance 10-fold relative to that predicted for S given alone; and 3) R inhibits S hepatic intrinsic clearance even after R plasma levels have become undetectable (>48 h after dosing), implying that R, when used as a pharmacokinetic enhancer, can be dosed less frequently than might be predicted from the duration of detectable systemic concentrations.

Intracellular concentration of protease inhibitors in HIV-1-infected patients: correlation with MDR-1 gene expression and low dose of ritonavir

BACKGROUND

Protease inhibitors (PIs) are substrates for the P-glycoprotein (P-gp/170) encoded by the multi-drug resistance gene (MDR-1). HIV infection is associated with increased expression of P-gp. The role of MDR gene overexpression in clinical pharmacokinetics is not known.

METHOD

We determined by HPLC, at trough and peak levels, the current PI concentrations in plasma (P) and in peripheral blood mononuclear cells (PBMCs) (intracellular concentration [IC]) from 49 HIV-infected patients receiving different treatment combinations: nelfinavir ([NFV] n = 12); indinavir ([IDV] n = 10); amprenavir ([APV] n = 5); ritonavir (RTV) 100 bid/IDV 800 mg bid (n = 6); RTV 400 bid/IDV 400 mg bid (n = 3); RTV 100 bid/saquinavir (SQV) 600 mg tid (n = 9); APV 600 bid/RTV 100 mg bid (n = 4). We determined the mean ratio of intracellular/plasma PI concentration for each treatment group. The MDR-1 gene expression was determined by a semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). HIV viral load was simultaneously measured.

RESULTS

49 patients (mean age 41 +/- 8.7 years; mean CD4 cell count 418 [57-972]; mean HIV RNA 2.1 +/- 0.8 log(10)) were included in the study. Patients who overexpressed the MDR-1 gene had significantly lower trough intracellular PI levels (p =.02) or lower intracellular accumulation of PI (p =.042). Patients treated with low-dose RTV in combined regimens with detectable RTV intracellular concentration showed lack of MDR-1 gene expression (p =.01). Patients with HIV RNA < 40 copies/mL had significantly higher RTV intracellular accumulation (p =.029).

CONCLUSION

In HIV-infected patients, IC of PI is inversely correlated with MDR-1 gene overexpression. Undetectable viral load was associated with the use of low-dose RTV, probably linked to better intracellular accumulation of the drug. Nevertheless, further investigation is needed to confirm these results.

Clinical lipoatrophy in HIV-1 patients on HAART is not associated with increased abdominal girth, hyperlipidaemia or glucose intolerance

OBJECTIVE

To compare information on body fat changes from questionnaire and clinical examination and to study lipoatrophy in HIV-1 patients on highly active antiretroviral therapy (HAART).

METHODS

The study was cross-sectional within a randomized trial. One hundred and sixty-eight male HIV-1 patients were examined by questionnaire and clinical examination. Clinical lipoatrophy was studied and defined as fat wasting in the face, legs and/or arms. Fasting blood samples reflecting lipid and glucose metabolism were taken and the role of indinavir, ritonavir (RTV) and RTV/saquinavir (SQV) on lipoatrophy was investigated.

RESULTS

After a median of 17 months on HAART, concordance rates between information on changes in body fat from questionnaire and clinical examination were significant and varied from 70 to 96%. With a positive criteria of lipoatrophy in both assessments, 14% of patients had lipoatrophy. These patients had lower weight (P = 0.0007), weight loss from baseline (P = 0.003), lower circumferences at all measurements (P < 0.01), lower plasma triglycerides and low-density lipoprotein (LDL) (P < 0.05) and longer treatment with stavudine (P = 0.0009). Homeostasis model assessment (HOMA) estimates for insulin resistance and beta-cell function were comparable. Plasma cholesterol, triglycerides and very low-density lipoprotein (VLDL) were higher in patients receiving RTV or RTV/SQV (P < 0.03).

CONCLUSION

Questionnaire and clinical assessment provide concordant information on changes in body fat. Lipoatrophic patients on HAART with neither increase in abdominal circumference, nor hyperlipidaemia nor glucose intolerance may have side-effects to protease inhibitor treatment, to nucleoside reverse transcriptase inhibitor treatment (stavudine) or suffer from a drug-independent condition.

Ritonavir plus saquinavir versus single protease inhibitor therapy in protease inhibitor-naive HIV-infected patients: the Swiss HIV Cohort Study

OBJECTIVES

To compare the response to ritonavir (RTV) plus saquinavir (SQV) with single protease inhibitor (PI) therapies among PI-naive HIV-1 infected individuals.

METHODS

Response to treatment was analysed according to the intent-to-treat principle in a prospective observational cohort study of 177 patients who between May 1995 and March 2000 started a double PI therapy with RTV and SQV (nonboosting dosages) plus at least one nucleoside reverse transcriptase inhibitor (NRTI) and 2,214 patients with a single PI therapy plus two NRTIs. We used survival analysis and Cox's proportional hazard regression methods. The primary endpoint was the time to a plasma viral load of < 400 copies/mL. Secondary endpoints were taken as a gain in the CD4 count of >100 cells/microL, and change of initial PI for any reason.

RESULTS

Baseline characteristics in both treatment groups were balanced. Median follow-up in both groups was 10.4 months. Time to an HIV-1 viral load of < 400 copies/mL and an increase in the CD4 count of >100 x 10(6) cells/L was shorter for RTV plus SQV compared with single PI regimens (log rank test for each endpoint P < 0.05). The adjusted hazard ratios of RTV plus SQV compared with single PI regimens were 1.21 (95% confidence interval 0.99-1.47) for achieving an HIV-1 viral load of < 400 copies/mL, 1.12 (0.88-1.42) for an increase in the CD4 count of > 100 cells/microL, and 0.90 (0.73-1.11) for change of first PI regimen.

CONCLUSIONS

Treatment with RTV plus SQV compared with single PI regimens appeared to give similar results for virological or immunological response.

Rheumatoid arthritis after 9 years of human immunodeficiency virus infection: possible contribution of tritherapy

Infection by human immunodeficiency virus (HIV) may affect joints in different ways. It usually increases the severity of reactive arthritis. Conversely, when rheumatoid arthritis (RA) is seen in association with HIV infection, remission of RA has been observed in some cases. We describe a patient who developed 3 successive forms of joint manifestations: early HIV related arthralgias followed by drug related arthritis, and more recently by typical RA. The first signs of joint manifestations started one year after HIV seroconversion and resolved when antiviral treatment with AZT was started. The second episode ended when lamivudine dosage was reduced. Finally, after 9 years of infection, the diagnosis of seropositive RA was made in this HLA-DR1 positive patient. The symptoms started when the immune status reached normal CD4 T cell levels, in response to antiviral tritherapy. This observation indicates the complex effect of HIV on joint inflammation.

Intracellular accumulation of human immunodeficiency virus protease inhibitors

Intracellular accumulation of the protease inhibitors (PIs) saquinavir (SQV), ritonavir (RTV), and indinavir (IDV) was determined in 50 human immunodeficiency virus-positive patients. Following extraction, PIs were quantified by mass spectrometry. Paired plasma and intracellular samples were collected over a full dosing interval from patients (13 on SQV, 6 on RTV, 8 on IDV, 16 on SQV plus RTV, 7 on IDV plus RTV) with a plasma viral load of <400 copies/ml. Data were expressed as intracellular/plasma drug concentration ratios. A hierarchy of intracellular accumulation was demonstrated by the following medians: 9.45 for SQV > 1.00 for RTV > 0.51 for IDV. Coadministration of RTV did not boost ratios of SQV or IDV within the cell or in plasma, although absolute plasma and intracellular SQV concentrations were increased by RTV. Seven individuals receiving SQV in hard-gel capsule form (median, 32 months) had higher intracellular/plasma drug ratios than all other patients receiving SQV (median, 17.62 versus 4.83; P = 0.04), despite consistently low plasma SQV concentrations. How this occurs may provide insight into the mechanisms that limit adequate drug penetration into sanctuary sites.

The unbound percentage of saquinavir and indinavir remains constant throughout the dosing interval in HIV positive subjects

AIMS

To measure the unbound plasma concentrations of saquinavir (SQV) and indinavir (IDV) and to relate them to the total plasma concentrations in order to establish the unbound percentage of protease inhibitors in vivo during a full dosage interval profile.

METHODS

HIV-infected subjects (n = 35; median CD4 cell count = 340 x 10(6) cells l-1, range: 120-825; viral load < 50 copies ml-1 in 22/35) treated with SQV or IDV containing regimens were studied. Plasma drug samples were collected at 0, 2, 4, 8 and 12 h postdose for the twice daily regimens and 0, 1, 2, 4 and 8 h for the three times daily regimens. Ultra-filtration was used to separate unbound IDV and SQV in plasma and their respective concentrations were measured by a fully validated method using high performance liquid chromatography-mass spectometry (h.p.l.c.-MS/MS).

RESULTS

Based on the ratio AUCunbound/AUCtotal, the median unbound percentage (95% CI for differences) of SQV and IDV from all the samples studied was 1.19% (0.99, 1.58%) and 36.3% (35.1, 44.2%), respectively. No significant difference was seen in the percentage binding of SQV between patients receiving SQV alone (median = 1.49%) or with ritonavir (median = 1.09%; P = 0.141; 95% CI for difference between medians = -0.145, 0.937) over the pharmacokinetic profile. Similarly, no significant difference was seen in the percentage binding of IDV in patients receiving IDV alone (median 35.2%) or with ritonavir (median = 41.3%; P = 0.069; 95% CI for difference between medians = -0.09, 15.4). The unbound concentrations of SQV (P < 0.0001; 95% CI for r(2) = 0.634, 0.815) and IDV (P < 0.0001; 95% CI for r(2) = 0.830, 0.925) remained constant as a proportion of total concentration over the full dosing profile.

CONCLUSIONS

These in vivo data confirm previously published in vitro measurements of SQV and IDV protein binding. The unbound percentage of both protease inhibitors remained constant over the dosing interval.

Efficacy and safety of twice-daily versus three-times daily saquinavir soft gelatin capsules as part of triple combination therapy for HIV-1 infection

OBJECTIVE

The objective of this study was to determine whether a triple therapy regimen incorporating twice-daily saquinavir is as effective as a three-times daily regimen.

METHODS

This was an open-label, Phase III, multicentre, 48-week study involving 837 HIV-1-infected patients randomised to one of the following: saquinavir soft gel capsule (SGC) 1200 mg three-times daily, plus two nucleoside reverse transcriptase inhibitors (NRTIs) (arm A); saquinavir SGC 1,600 mg twice-daily, plus two NRTIs (arm B); saquinavir SGC 1,200 mg twice-daily and nelfinavir 1,250 mg twice-daily, plus a single NRTI (arm C). The primary outcome measure was the virological response in arm A versus B and in arm A versus C with respect to the percentage of patients whose plasma HIV-1 RNA levels fell below the level of quantification for the Amplicor assay (<400 copies/ml) at weeks 24 and 48.

RESULTS

At 48 weeks, the percentage of patients with plasma HIV-1 RNA levels <400 copies/ml was 47.1% (arm A), 45.3% (arm B) and 42.7% (arm C) in the intention-to-treat analysis. The treatment difference between arm B-arm A was -1.8% (95% confidence intervals -10.1, 6.5) and for arm C-arm A was -4.5% (95% confidence intervals -12.7, 3.7) in the intention-to-treat analysis. These differences fell within the maximum allowable difference (+/- 12%) for arm B compared with arm A. At week 24, the percentage of patients with HIV-1 RNA levels <400 copies/ml was 59.6% (arm A), 57.6% (arm B) and 51.3% (arm C).

CONCLUSIONS

A twice-daily triple therapy regimen incorporating saquinavir SGC plus two NRTIs was of equivalent efficacy to the three-times daily regimen studied. All regimens were generally well tolerated.

Predictors of treatment failure during highly active antiretroviral therapy (racing trial)

PURPOSE

To determine factors associated with virological failure during long-term treatment with the triple combination of saquinavir soft gel capsule, zalcitabine and zidovudine.

METHOD

Open-label, prospective, multicentre study undertaken in private practices and the outpatient department of the Auguste-Viktoria-Hospital. A total of 95 patients with plasma HIV RNA > 5000 copies/ml who had received no more than 6 months pre-treatment with NRTIs and no prior PI therapy received saquinavir soft gel, zalcitabine and zidovudine for 52 weeks, before being randomly assigned to either remain on therapy or switch to nelfinavir, lamivudine and zidovudine for further 52 weeks.

RESULTS

Combination therapy with saquinavir, zalcitabine and zidovudine was found to be effective and well tolerated, with virological response to therapy maintained for up to 2 years. In patients responding to therapy, switching to a novel triple regimen did not result in a virological or immunological worsening, but it did not confer an additional clinical benefit. Factors predictive of early treatment failure (virological failure within 16 weeks of treatment initiation) included high viral load and presence of RT mutations at baseline (OR: 0.30, 95% CI 0.11 0.83 and OR 0.13, 95% CI 0.03 0.52, respectively), with baseline viral load and the development of genotypic mutations on therapy being predictive of late treatment failure (16 52 weeks; OR: 0.15, 95% 0.05 0.46 and OR: 0.26, 95% CI < 0.001 1.16, respectively). Plasma saquinavir concentration < 50 mg/ml at 4 weeks was also found to be an independent risk factor for both early and late treatment failure (OR: 1.80, 95% CI 1.23 2.64 and OR: 1.16, 95% CI 0.84 1.60, respectively).

CONCLUSIONS

While antiretroviral drug resistance appears to be a principal cause of treatment failure, other factors such as inadequate drug plasma concentrations also play a role.

Safety and efficacy of saquinavir soft-gelatin capsules + zidovudine + optional lamivudine in pregnancy and prevention of vertical HIV transmission

BACKGROUND

The treatment of HIV infection during pregnancy significantly and substantially reduces the risk of mother-to-child transmission. Although triple therapy is the standard of care for management of HIV infection in adults, the safety of many approved antiretroviral agents in pregnancy is not currently established.

METHODOLOGY

An open-label pilot study conducted in Thailand and the UK of the safety of saquinavir soft-gel capsules 1200 mg three times daily administered in the second and third trimester of pregnancy in combination with local standard-of-care antiretroviral therapy. Infants received local standard-of-care antiretroviral therapy after delivery. Steady-state pharmacokinetics were performed in a subset of mothers at 4 weeks after the commencement of saquinavir therapy and paired samples collected from the mother and infant cord blood at delivery.

RESULTS

Eighteen antiretroviral-naive pregnant women with a mean viral load of 4.2 log10 and CD4 cell count of 481/mm(3) were recruited. All patients received zidovudine and 3 (all in the UK) received lamivudine. There were no serious adverse events and no discontinuations due to adverse events. Viral load declined by 1.6 log10 at week 4 and was less than 400 copies/mL at delivery in 16/17 mothers. Sixteen live births were recorded, with two in utero deaths-one secondary to an accident and the second due to antiphospholipid syndrome. Both deaths were considered by investigators to be unrelated to study therapy. All infants were HIV negative at subsequent follow-up and no fetal abnormalities were observed. Pharmacokinetic data suggested that mothers had relatively low exposures to saquinavir despite an excellent virologic response. Saquinavir was not detected in cord blood.

DISCUSSION

Saquinavir soft-gel capsules are well tolerated during pregnancy and are not associated in this small study with birth abnormalities. Transmission of HIV infection from mother to child was successfully prevented in all cases. Low maternal exposures of saquinavir were noted. However, these did not appear to affect virologic efficacy of the combination. Samples from cord blood indicate minimal fetal exposure to saquinavir.

Effect of coadministration of nelfinavir, indinavir, and saquinavir on the pharmacokinetics of amprenavir

OBJECTIVE

Pharmacokinetic interactions are expected when human immunodeficiency virus (HIV) protease inhibitors are coadministered because many are both substrates for and inhibitors of CYP3A4. The goal of this model-based pharmacokinetic analysis was to describe the differences observed in amprenavir pharmacokinetics among treatment arms in the Adult AIDS Clinical Trial Group (AACTG) study protocol 398 and to propose mechanisms to account for them.

METHODS

One hundred seventy-six HIV-positive subjects receiving 1200 mg amprenavir twice daily as part of AACTG protocol 398 were included in the pharmacokinetic study. All patients also received background medications efavirenz, adefovir dipivoxil, and abacavir and, depending on the study arm, placebo or one of the following protease inhibitors: nelfinavir, indinavir, or saquinavir. A population pharmacokinetic model was fitted to a total of 565 amprenavir concentration measurements. The blood samples for concentration measurements were drawn at week 2 (12-hour pharmacokinetic study, approximately 7 samples per study; 46 patients) and at week 24 (6-hour pharmacokinetic study, approximately 5 samples per study; 10 patients). In addition, samples were collected at 1 or more follow-up visits (population pharmacokinetic study, 1 to 3 occasions per patient; 150 patients).

RESULTS AND CONCLUSION

Amprenavir intrinsic clearance was significantly reduced relative to placebo by nelfinavir (-41%) and indinavir (-54%) but not by saquinavir. The absolute magnitude of amprenavir intrinsic clearance suggests that CYP3A4 inhibition by nelfinavir and indinavir is balanced by enzymatic induction in the presence of the background drug(s), most likely efavirenz. Amprenavir intrinsic clearance apparently increases by more than 30% between weeks 2 and 24, possibly because of the time course of CYP3A4 induction.

Dose-dependent increase of saquinavir bioavailability by the pharmaceutic aid cremophor EL

AIMS

Bioavailability of orally administered drugs depends on several factors including active excretion, e.g. by P-glycoprotein (PGP), and presystemic metabolism, e.g. by cytochrome P450 3A (CYP3A), in both gastrointestinal tract and liver. Many drugs including saquinavir are substrates of both PGP and CYP3A. It was the aim of this study to test whether the extremely low bioavailability of saquinavir can be increased dose-dependently in vivo by cremophor EL, an 'inactive' pharmaceutic aid known to inhibit PGP in vitro.

METHODS

In a randomized, placebo-controlled, double-blind, four phase cross-over design single doses of oral saquinavir (Invirase, 600 mg, without food) were administered with increasing single doses of oral cremophor EL (up to 5000 mg) to eight healthy, male individuals. Saquinavir plasma concentrations were determined by LC/MS/MS up to 48 h after intake. Main outcome measures were area under the plasma concentration time curve (AUC), peak concentration (Cmax), time to reach Cmax (tmax) and terminal elimination half-life (t(1/2)).

RESULTS

Cremophor EL dose-dependently increased Cmax, AUC(0,4 h), and AUC(0,infinity) of saquinavir. As compared with placebo, the increment observed after 5000 mg cremophor EL was 13-fold for both Cmax and AUC(0,4 h) and 5-fold for AUC(0,infinity). The terminal half-life and the time to reach Cmax (tmax) were unchanged.

CONCLUSIONS

Cremophor EL increased the systemic availability of saquinavir without affecting its elimination suggesting that cremophor EL is not devoid of pharmacological action and acts as a modulator of the absorption process, probably by inhibiting intestinal PGP.

A randomized, open-label, comparative trial of BID and TID dosing of saquinavir enhanced oral formulation as part of a triple therapy for advanced AIDS patients

OBJECTIVE

To compare the efficacy and safety of 1,400 mg BID and 1,200 mg TID of saquinavir soft gel given with zidovudine and lamivudine in antiretroviral-naïve, advanced AIDS patients.

METHOD

A randomized, open-label study conducted at a university hospital.

RESULTS

Forty cases were enrolled in the study, 20 cases in each group. The mean CD4 cell count was 29 cells/mm3. The mean log10 HIV-1 RNA was 5.27 copies/mL. Using an on-treatment analysis, the reduction in plasma log10HIV-1 RNA of BID and TID groups was not statistically significant at -2.44 vs -2.60 copies/mL (-0.16, 95% CI -0.63 to 0.30; p= 0.48). The mean increase in CD4 cell counts was not statistically significant at +144 and +159 cells/mm3 (11, 95% CI -75 to 97; p=0.79).

CONCLUSION

The preliminary data suggests that in antiretroviral-naïve, advanced AIDS patients, 1,400 mg BID of saquinavir soft gel given with two nucleoside analogues might be as effective as the standard 1,200 mg TID.