Efficacy and safety of twice daily first-line ritonavir/indinavir plus double nucleoside combination therapy in HIV-infected individuals. German Ritonavir/Indinavir Study Group

The Cologne-Bonn cohort: lessons learned

Much of our knowledge about HIV infection has been obtained from cohort studies, including description of the natural history of infection, identification of CD4 count and viral load as good surrogate markers of clinical progression, identification of co-factors [including older age and viral infections (CMV, HCV)] for progression of HIV-related disease and assessment of impact of highly active antiretroviral therapy on clinical outcomes. The Cologne-Bonn cohort was founded by Gerd Fätkenheuer and Bernd Salzberger after introduction of combination antiretroviral therapy in 1996 and has delivered important findings which have helped to improve treatment strategies as well as quality of overall care in HIV infection in these two cities. Indeed, the first pivotal paper from the cohort reported on an unexpectedly high rate of virological treatment failure of protease inhibitor therapy in an unselected cohort of HIV-infected patients. The subsequent analysis of risk factors for virological failure initiated the development of more potent HIV combination therapy. This review summarizes some of the major findings and contributions from the Cologne-Bonn cohort since 1996.

Prevalence, severity, and duration of thrombocytopenia among HIV patients in the era of highly active antiretroviral therapy

Thrombocytopenia is a clinically relevant outcome in HIV. However, the epidemiology of this condition, including frequency, severity, and duration, has not been well-characterized in the era of highly active antiretroviral therapy (HAART). In this study, we describe the epidemiology of thrombocytopenia using two methods. We conducted a systematic review of the literature published between 1997 and 2009 to characterize the frequency of thrombocytopenia in different populations in the HAART era. Secondly, we examined the frequency, severity, and duration of thrombocytopenia among HIV patients in the Collaborations in HIV Outcomes Research/US (CHORUS) Cohort from 1997 to 2006 and among HIV patients participating in GlaxoSmithKline HIV Clinical Trials between 1996 and 2004. Prevalence estimates of thrombocytopenia (<150 000 platelets/µl) in the literature varied greatly but were generally above 10%. The thrombocytopenia prevalence estimates in the CHORUS Cohort and the HIV Clinical Trials were both 14%. In the CHORUS Cohort, the platelet count was ≤50 000/µl among 3.1% and ≤30 000/µl among 1.7%; in the HIV clinical trials database, the platelet count was ≤50 000/µl among 1.3% and ≤30 000/µl among 0.67%. Duration of severe thrombocytopenia varied greatly, with the medium duration to ≥75 000 platelets/µl taking 147 days in the CHORUS Cohort and 33 days in the HIV clinical trials database. Among 111 patients with severe thrombocytopenia in the CHORUS Cohort, 23% never achieved a higher platelet count over follow-up. In conclusion, while the prevalence of severe thrombocytopenia was low, it occurred at levels associated with bleeding and was persistent among a small proportion of patients despite receipt of HAART.

Stavudine or zidovudine in three-drug combination therapy for initial treatment of HIV infection in antiretroviral-naïve individuals

BACKGROUND

The introduction of highly active antiretroviral therapy (ART) as treatment for HIV infection has greatly improved mortality and morbidity for adults and children living with HIV around the world. Two common medications given in first-line antiretroviral therapy are the nucleoside reverse transcriptase inhibitors (NRTI) stavudine (d4T) or zidovudine (AZT).

OBJECTIVES

To assess the efficacy of d4T compared to AZT in combination with one NRTI and one non-nucleoside reverse transcriptase inhibitor (NNRTI), two additional NNRTIs, or one NRTI and one protease inhibitor (PI), as part of first-line ART for HIV-infected people in low-resource settings.

SEARCH STRATEGY

Standard Cochrane methods were used to search electronic databases and conference proceedings with relevant search terms without limits to language.

SELECTION CRITERIA

Randomised controlled trials of HIV-infected patients 5 years of age and older were included. Primary outcomes of interest included mortality, severe adverse events, virologic response to ART, and adherence/tolerance/retention. Secondary outcomes included immunologic response to ART, development of ART drug resistance, and prevention of sexual transmission of HIV.

DATA COLLECTION AND ANALYSIS

Two authors assessed each reference for inclusion and exclusion criteria established a priori. Data were abstracted independently using a standardised abstraction form.

MAIN RESULTS

Nine randomised controlled trials were identified as meeting the inclusion criteria. The nine trials enrolled 2,159 participants but looked at a multiplicity of drug combinations. Despite this, a reasonably robust literature suggests no statistically significant difference between the two drug combinations, including severe adverse events and adherence/tolerance/retention. The quality of the literature was found overall to be low to very low for all key outcomes. Only one study reported on drug resistance, and no studies reported on sexual transmission of HIV. The length of follow-up time and study settings varied greatly.

AUTHORS' CONCLUSIONS

While ideally future research would focus on direct comparison of standard therapeutic combinations of d4T+3TC+an NNRTI and AZT+3TC+an NNRTI to compare these regimens more directly, it is unlikely that additional trials will be mounted. Observational studies should focus on understanding outcomes, including toxicity and tolerability, in low- and middle-income countries.

Benefit of therapeutic drug monitoring of protease inhibitors in HIV-infected patients depends on PI used in HAART regimen--ANRS 111 trial

As a result of high inter-patient variability, and efficacy-concentration and toxicity-concentration relationships, optimization of HIV-protease inhibitor (PI) doses based on plasma concentrations could be beneficial. During a 48-week open prospective non-randomized interventional study of 115 protease inhibitor-naïve patients initiating an indinavir/ritonavir- or lopinavir/ritonavir-, or nelfinavir-containing therapy, protease inhibitor dose was modified when plasma trough concentrations (C(trough)) at weeks 2, 8, 16 and 24 were outside predefined optimal concentration ranges. Failure of the strategy was defined as the proportions of patients with HIV-RNA above 200 copies/mL from weeks 24 to 48 and/or experiencing grades 2, 3 or 4 PI-related adverse events during the study; proportion of patients with last C(trough) measurement outside the concentration range was determined at each visit. Virological failure and/or occurrence of adverse event were observed in 37/94 assessable patients (39%; 95% CI: 29.4-50.0). In the on-treatment analysis, failure of the strategy was noted in 16% of indinavir/r- or lopinavir/r-treated patients (8/51; 95% CI: 7.0-28.6; virological failure: 2; adverse event: 6) but in 44% of nelfinavir-treated patients (11/25; 95% CI: 24.4-65.1; virological failure: 10; adverse event: 1); C(trough) concentrations outside the range were less frequent at the last measurement than at W2 (41% vs. 66%; P < 0.05), with proportions of 35% for indinavir/r- or lopinavir/r-treated patients, but 57% for nelfinavir-treated patients. The proposed strategy of therapeutic drug monitoring may be beneficial to indinavir/r- and lopinavir/r-treated patients, but failed to move concentrations into the predefined range and to produce the expected virological success for nelfinavir-treated patients.

Antiretroviral therapy with a twice-daily regimen containing 400 milligrams of indinavir and 100 milligrams of ritonavir in human immunodeficiency virus type 1-infected women during pregnancy

We evaluated the safety and efficacy of a twice daily regimen containing 400 mg of indinavir and 100 mg of ritonavir in 32 human immunodeficiency virus (HIV)-infected women during pregnancy. The median indinavir trough concentration was 208 ng/ml during the third trimester. At delivery, 26 of 28 women on indinavir-ritonavir had HIV RNA levels of <200 copies/ml. No infant was HIV infected. These data are encouraging for the use of this combination for prevention of mother-to-child transmission of HIV.

Maintenance of indinavir by dose adjustment in HIV-1-infected patients with indinavir-related toxicity

OBJECTIVE

Treatment with indinavir/ritonavir (IDV/RTV) is very effective but hampered by frequent development of IDV-associated adverse events (mainly nephrotoxicity and skin changes). We tested whether dose reduction of IDV guided by therapeutic drug monitoring resulted in improved tolerability without compromising antiviral efficacy.

PATIENTS

HIV-infected patients with any IDV/RTV regimen who suffer from IDV-related adverse events were included. Viral load had to be adequately controlled for at least 2 months prior to inclusion. Dose reduction from 800 mg to 600 or 400 mg IDV b.i.d. followed a specified protocol. IDV-related toxicity and IDV plasma concentrations were monitored for 24 weeks. IDV concentrations were quantified with a validated high performance liquid chromatography method.

RESULTS

Twenty patients were included. Reasons for inclusion were: skin abnormalities 11, nephrotoxicity five, metabolic disturbances three, and hypertension one. IDV dose could be lowered to 400 mg b.i.d. in 13, to 600 mg b.i.d. in two patients. Five patients discontinued the treatment. Overall tolerability improved with respect to incidence and severity of adverse events. Median trough concentrations decreased from 1.02 mg/l (range 0.08-7.1) at baseline to 0.48 mg/l (0.11-1.4) after 24 weeks (p = 0.03) and remained above the critical threshold of 0.1 mg/l at any time after dose reduction. There was no change of CD4 cell counts or viral suppression. There were no significant changes in other laboratory parameters (creatinine, bilirubin, triglycerides, cholesterol, blood count, and urinalysis).

CONCLUSION

Dose reduction of IDV improved tolerability of IDV-containing highly active antiretroviral treatment (HAART). Sufficient IDV trough concentrations were maintained in all patients as was virologic control.

Comparison of two indinavir/ritonavir regimens in the treatment of HIV-infected individuals

BACKGROUND

Pharmacokinetic enhancement of protease inhibitors (PIs) with low-dose ritonavir (RTV) for salvage therapy is increasingly common. The purpose of this study was to compare the pharmacokinetics, safety, and tolerability of indinavir (IDV)/RTV at 800/200 mg (arm A) and 400/400 mg (arm B) administered twice daily in HIV-infected subjects failing their first PI-based regimen.

METHODS

A phase I/II, randomized, open-label, 24-week study was conducted. Formal 12-hour pharmacokinetic evaluations were performed, and study visits occurred at baseline; at weeks 1, 2, and 4; and every 4 week thereafter for 24 weeks. Clinical symptoms and laboratory assessments were collected. Subjects were allowed to switch arms because of toxicity.

RESULTS

Forty-four subjects were enrolled (22 per arm). IDV predose concentration, maximum plasma concentration and area under the curve were significantly higher in arm A. Fifty-five percent and 45% of subjects in arms A and B responded (<200 copies/mL at week 24; P = 0.76), respectively. CD4 cell responses were similar. All subjects had IDV-sensitive virus at baseline and at virologic failure. Tolerability was comparable, but all grade 3 or higher triglyceride increases occurred in arm B and more subjects in arm B switched because of toxicity (5 vs. 1 triglyceride increases).

CONCLUSIONS

This is the largest formal pharmacokinetic evaluation of 2 dosage combinations of IDV/RTV in HIV-infected individuals. Pharmacokinetic parameters were consistent with previous results in patients but lower than in seronegative controls. Both regimens exhibited similar tolerability and response rates. High toxicity with a low response suggests that the optimum IDV/RTV combination would include an RTV dose <400 mg and an IDV dose <800 mg in this population.

[Therapeutic strategies for HIV infection: tolerance to boost antiproteases]

As tolerance not only depends on protease inhibitors (PI) dosing but also on their trough concentrations, the enhanced exposure associated with PI boosting goes together with a reduced tolerance, especially at the biological level. Moreover, the toxicity associated with the low doses ritonavir used in boosting seems to compromise, at least partly, the favourable metabolic profile of certain PI. Eventually, boosted lopinavir tolerance is similar to that of other PI. Even if the advantage/risk ratio of lopinavir or other boosted PI globally seems favourable, the final choice belongs to the physician in charge of evaluating the individual risk of a lesser, especially metabolic tolerance, for his or her patient.

Lopinavir/ritonavir vs. indinavir/ritonavir in antiretroviral naive HIV-infected patients: immunovirological outcome and side effects

We compared immunovirological outcomes and toxicities of HAART regimens including LPV/r and IDV/r in antiretroviral naïve HIV-1 patients. We retrospectively selected 55 patients starting LPV/r and 52 starting IDV/r as first-line HAART. Immunovirological and metabolic parameters were recorded at baseline and every 3 months as were side effects, AIDS-defining events and deaths. Demographic characteristics and NRTIs included in the regimens were comparable. Both groups reached undetectable HIV-RNA plasma viremia from third month and maintained during follow-up. However, patients receiving IDV/r had a lower probability to obtain virological success (RH: 0.46). Patients receiving IDV/r patients showed a greater increase of total cholesterol (P = 0.01). Three patients on LPV/r and 21 on IDV/r discontinued the drug for toxicity, leading to a 8.40 higher risk of discontinuation in the latter group. In our clinical setting IDV/r showed to be less effective and more toxic than LPV/RTV as first-line HAART.

Prediction of virological response to lopinavir/ritonavir using the genotypic inhibitory quotient

The predictive value of virological response to lopinavir (LPV)/ritonavir (r) was assessed in 126 HIV-infected patients who failed antiretroviral therapy and had begun a rescue intervention based on LPV/r. At 3 months, subjects with < or =6 protease (PRO) resistance mutations showed a higher rate of virological response (HIV-RNA drop > 1 log or to <50 copies/ml) than patients with >6 PRO resistance mutations (77% versus 48%; p = 0.01). On the other hand, virological responders had greater mean LPV plasma trough levels than nonresponders (6.4 versus 3.9 microg/ml; p = 0.02). A positive correlation was found between LPV trough concentration and viral load reductions at 3 months under LPV/r (r = 0.23; p = 0.017). Overall, virological response was seen in 80.8% of patients with LPV trough levels >4.8 microg/ml while in only 52.5% of patients with lower LPV trough concentrations (p = 0.002). In the multivariate analysis, both < or =6 PRO resistance mutations and LPV trough levels >4.8 microg/ml were independent predictors of virological response to salvage therapy with LPV/r. A genotypic inhibitory quotient (GIQ) was estimated for each patient based on the ratio between LPV trough levels and the number of PRO resistance mutations. A positive strong correlation was found between GIQ and viral load reductions (r = 0.42; p = 0.002). Virological response was seen in 78% of patients with a GIQ >0.7 but only in 41.6% of those with lower GIQ (p = 0.004). When LPV trough levels >4.8 microg/ml, PRO resistance mutations < or =6, and GIQ >0.7 were all included in a stepwise multivariate analysis, GIQ remained as the main independent predictor of response to LPV/r.

Comparison of Two Reduced-Dose Regimens of Indinavir (600 Mg Vs 400 Mg Twice Daily) and Ritonavir (100 Mg Twice Daily) in Healthy Volunteers (Coredir)

Objective

To assess the pharmacokinetics and tolerability of reduced dosages of twice daily indinavir (IDV) boosted by low-dose ritonavir (RTV) in healthy volunteers.

Methods

Pharmacokinetics and tolerability of IDV/RTV twice daily (600/100 mg and 400/100 mg) were assessed in a randomized crossover design in 16 healthy volunteers. Each dosage was taken twice daily for 2 weeks before 12 h pharmacokinetics were obtained.

Results

Sixteen subjects were included, with a mean age ±SD of 30 ±4 years; seven female, nine male. Fifteen subjects completed the study. After dose reduction of IDV AUC, Cmax and Cmin decreased significantly. In the 400 mg group three out of 15 subjects had IDV levels below 0.10 mg/l vs none in the 600 mg group. All subjects reported mild to moderate side effects throughout the study period, which were more severe in the 600 mg group (mostly renal, dry skin/lips, paresthesias/oral discomfort). In the 600 mg group four subjects reported dysuria and one subject discontinued because of flank pain, whereas two subjects reported dysuria and no subject discontinued in the 400 mg group, respectively. Eight subjects developed crystalluria without a significant difference between both groups. No significant change in serum creatinine was observed.

Conclusions

IDV/RTV 400/100 mg twice daily resulted in significant lower IDV exposure, with three out of 15 subjects revealing Cmin values below the recommended threshold for wild-type virus of 0.10 mg/l. Tolerability, however, was lower in the 600 mg IDV group. Therapeutic drug monitoring in the individual patient appears to be necessary to guarantee appropriate drug levels and simultaneously minimize toxicity. Presented in part at the 6th International Congress on Drug Therapy in HIV Infection. Glasgow, Scotland, UK, November 2002. Abstract P182.

Correlation between lopinavir plasma levels and lipid abnormalities in patients taking lopinavir/ritonavir

Lopinavir (LPV)/ritonavir (RTV) used in combination, is a potent antiretroviral drug. However, its benefit is limited by its inherent effect on lipid metabolism, causing dislypemia in a large proportion of treated patients. Fasting triglyceride (TG) and cholesterol levels were assessed in 126 HIV-infected patients who initiated salvage therapy based on LPV/RTV. Both TG and cholesterol significantly increased from baseline to month 3. A positive correlation was found between the percentage increase in TG and LPV trough levels (r = 0.32; p = 0.003). Moreover, patients with TG elevations above the median (27%) showed higher LPV Ctrough levels than those with lower TG elevations (7.1 vs. 4.7 microg/ml, p = 0.004). In contrast, no correlation was found between LPV Ctrough and increases in cholesterol levels. Cholesterol elevations were positively correlated with RTV Ctrough concentrations (r = 0.32; p = 0.003).

Continued indinavir versus switching to indinavir/ritonavir in HIV-infected patients with suppressed viral load

OBJECTIVE

To compare continued indinavir (IDV) 8-hourly (q8h) with switching to indinavir/ritonavir (IDV/RTV) 12-hourly (q12h) in HIV-positive patients having suppressed viral load with IDV q8h plus two nucleoside reverse transcriptase inhibitors (NRTI).

DESIGN

Multicentre, international, randomized, open-label study enrolling HIV-1 infected patients on IDV 800 mg q8h plus two NRTI with CD4 cell counts > or = 100 x 106/l and plasma HIV RNA < 500 copies/ml for > or = 3 months.

METHODS

Patients were randomized to continue on the same regimen or to switch to IDV plus liquid RTV (IDV/RTV 800 mg/100 mg q12h). Primary endpoint was the proportion of patients remaining < 500 copies/ml at 48 weeks.

RESULTS

A total of 323 patients (IDV/RTV, 162; IDV, 161) were evaluable. At 48 weeks, the proportions of patients with plasma HIV RNA < 500 copies/ml were 93%, 88% and 58% in the IDV/RTV arm versus 92% (P = 1), 86% (P = 0.87) and 74% (P = 0.003) in the IDV arm using on-treatment (OT) and intent-to-treat (ITT) [switches included (ITT, S = I) and switches = failure (ITT, S = F)] analyses respectively. Mean increase in CD4 cell count was 88 x 106/cells/l (IDV/RTV arm) and 60 x 106 cells/l (IDV arm) (P = 0.08). More patients discontinued study medication due to adverse events in the IDV/RTV arm than in the IDV arm (P < 0.001).

CONCLUSIONS

Equivalence of continuing IDV q8h versus switching to IDV/RTV (liquid) q12h in suppressed stable patients was demonstrated by OT and ITT S = I analyses. However, the IDV q8h arm performed better when discontinuations were classified as failures. IDV/RTV q12h can be convenient and equally effective for patients able to tolerate it.

Efficacy of a twice-daily antiretroviral regimen containing 100 mg ritonavir/400 mg indinavir in HIV-infected patients

OBJECTIVE

To evaluate the pharmacokinetics, efficacy and tolerability of a low-dose boosted indinavir (IDV)/ritonavir (RTV) regimen [100 mg RTV/400 mg IDV twice daily (bid)] in patients previously receiving a standard IDV regimen [800 mg three times a day (tid)].

METHODS

In a prospective, open-label, cross-over trial, patients with plasma HIV RNA < 200 copies/ml receiving an IDV-containing regimen (800 mg tid) were switched to an RTV/IDV (100/400 mg bid)-containing regimen. Minimal and maximal IDV plasma concentrations ( Cmin and Cmax ) were determined before the switch (day 0), at week 2 and week 4 after the switch. The CD4 cell count and plasma HIV RNA were determined at day 0, week 2 and week 4, then every 8 weeks. The primary end-point was the percentage of patients with plasma HIV RNA below 200 copies ml at week 48.

RESULTS

Twenty patients were enrolled. At baseline, on IDV 800 mg tid, median IDV Cmin was 194 ng/ml and median IDV Cmax was 8449 ng/ml. On RTV/IDV (100/400 mg), median IDV Cmin increased to 536 ng/ml at week 2 and 475 ng/ml at week 4, while Cmax decreased to 2983 ng/ml at week 2 and 2997 ng/ml at week 4 ( P < 0.001). The median area under the IDV plasma concentration-time curve measured in seven patients was 25 126 ng.h/ml, and the IDV half-life (t1/2 ) was 4.4 h. All patients had plasma HIV RNA remaining < 200 copies/ml at week 48. Tolerability of RTV/IDV was excellent.

CONCLUSION

RTV/IDV (100/400 mg bid) yields significantly higher IDV plasma Cmin and lower IDV Cmax values relative to the standard IDV regimen, thereby improving both tolerability and efficacy.

Overcoming resistance: virologic response to a salvage regimen with the combination of ritonavir plus indinavir

PURPOSE

To explore the possibility of overcoming resistance to protease inhibitors (PIs) and to determine the resistance cutoff values that continue to predict treatment failure with a dual PI regimen.

METHOD

We performed a prospective study of 53 patients who had failed in several PIs and who were included in a ritonavir (RTV) plus indinavir (IDV) salvage regimen. Median HIV RNA level decrease was evaluated according to resistance assays and indinavir trough levels.

RESULTS

Eighty-seven percent of patients had previously failed on an IDV-containing regimen. Overall, median HIV RNA decrease was -1.25 log(10) copies/mL after 3 months on therapy. A significant blunted virologic response was observed only in isolates with more than 12 substitutions including the V82A (-0.75 vs. -1.3 log(10) copies/mL; p =.04), or in isolates with more than 30 fold-increase in the IC(50) (-0.43 vs. -1.2 log(10) copies/mL). Higher drug levels were observed in patients with resistant isolates who achieved an HIV RNA decrease greater than 1 log (1742 vs. 1100 ng/mL).

CONCLUSION

Our preliminary data suggest the possibility of overcoming resistance with the combination of RTV plus IDV. They also suggest the need for establishing new resistance cutoff values when using PIs in combination.

First-line ritonavir/indinavir 100/800 mg twice daily plus nucleoside reverse transcriptase inhibitors in a German multicentre study: 48-week results

OBJECTIVES

To evaluate safety and efficacy of the protease inhibitor combination ritonavir/indinavir 100/800 mg twice daily plus 2-3 nucleoside reverse transcriptase inhibitors (NRTI) in antiretroviral-naive patients.

METHODS

Within this open-label, uncontrolled multicentre trial, antiretroviral-naive patients (n = 57) with median baseline HIV-RNA of 308,000 copies/mL (range 170-3.01 million copies/mL) and median CD4 cell count of 50 cells/microL (range 0-853 cells/microL) were started on 2-3 NRTIs plus ritonavir/indinavir 100/800 mg twice daily. CD4 cell counts and HIV-RNA were determined at weeks 0, 4, 8, 12, 16, 20, 24 and 48. Statistical analysis was performed on treatment as well as intent-to-treat.

RESULTS

Viral load decreased by a median of 3.79 log10 copies/mL (range 2.0-4.60 log10 copies/mL) until week 48. At week 48, 23/57 (40%, intent-to-treat) patients showed a viral load </= 80 copies/mL. In parallel, median CD4 cell counts increased by a median of 149 cells/microL (range -60-420 cells/microL). Median triglycerides and cholesterol increased from baseline 160 mg/dL (range 33-364 mg/dL) to 218 mg/dL (range 110-527 mg/dL) at week 48 and from 166 mg/dL (range 63-262 mg/dL) to 233 mg/dL (range 95-359 mg/dL), respectively. Twenty-seven of fifty-seven patients (47%) discontinued study medication, 19 (33%) due to nephrolithiasis. Two patients changed their antiretroviral regimen after failing virologically.

CONCLUSION

Ritonavir/indinavir 100/800 mg twice daily appears to be effective up to 48 weeks despite high baseline viraemia and low CD4 cell count in antiretroviral-naive patients. However, discontinuation due to adverse events, especially nephrotoxicity, is frequent and limits treatment duration. Therefore, extra hydration appears inevitable with this combination.

Efficacy and Safety of Ritonavir/Indinavir 100/400 Mg Twice Daily in Combination with Two Nucleoside Analogues in Antiretroviral Treatment-Naive HIV-Infected Individuals

Objective

To evaluate the efficacy and tolerability of indinavir/ritonavir (IDV/RTV) 400/100 mg twice daily in combination with two nucleoside reverse transcriptase inhibitors in antiretroviral-naive patients.

Design and methods

Antiviral therapy-naive patients with plasma HIV-1 RNA >5000 copies/ml were enrolled in this pilot, single-arm study. CD4 cell count and viral load were evaluated at weeks (W) 4, 12, 24 and every 3 months until W48. The primary end-point was the percentage (%) of patients with viral load <400 copies/ml at W48. Intent-to-treat (ITT) (missing values or change in treatment equalled failure) and on-treatment (OT) analyses were performed.

Results

Forty patients were enrolled. Baseline median viral load was 5.36 log10 copies/ml, median CD4 count was 84 cells/mm3. At W48 by ITT analysis, the % patients with viral load <400 copies/ml was 65% (95% CI: 48–79) and 50% (95% CI: 35–65) with viral load <50 copies/ml, and 96% (26/27) (95% CI: 89–100) and 74% (95% CI: 57–91], respectively, by OT analysis. The median decrease in viral load at W48 was –3.83 log10 copies/ml (–0.1; –5.19) and the median increase in CD4 was +167 cells/mm3 (6–474 cell/mm3). At W4 (34/40), the median IDV Cmin was 500 ng/ml (range 5–8100) with 91% of patients with an adequate IDV Cmin >150 ng/ml. Ten patients discontinued the study treatment before W48: adverse events (eight), patient's will (one) and simplification of therapy (one). Three patients were lost to follow-up. Only one virological failure occurred and was associated with poor compliance and sub-optimal concentrations of IDV/RTV.

Conclusions

IDV/RTV 400/100 mg twice daily is an effective and safe first-line antiretroviral therapy. The simplicity and the low cost of IDV/RTV is of major interest particularly in countries with limited resources.

Hepatotoxicity associated with antiretroviral therapy containing dual versus single protease inhibitors in individuals coinfected with hepatitis C virus and human immunodeficiency virus

To determine the rates of patients coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) who discontinued therapy as a result of protease inhibitor (PI)-related hepatotoxicity, a retrospective review was conducted. Baseline CD4 counts, plasma HIV RNA levels, and duration of therapy were comparable between single- and dual-PI-treated subjects and between subjects receiving ritonavir-containing therapy and those receiving ritonavir-sparing therapy. The proportions of patients with elevations in alanine aminotransferase level to > or =5 times the upper limit of normal (19% versus 26%) and hyperbilirubinemia (30% versus 38%) were similar between the dual-PI (n=27) and single-PI treatment groups (n=39), respectively. No difference in these characteristics was observed between ritonavir-containing (n=34) and ritonavir-sparing (n=32) treatment arms. Rates of treatment discontinuation due to hepatotoxicity were similar for single-PI and dual-PI therapy and for ritonavir-containing and ritonavir-sparing regimens. Dual-PI therapy and inclusion of ritonavir do not seem to increase the rates of hepatotoxicity in PI-treated, HIV-HCV coinfected subjects.

Quantification of plasma and intracellular levels of the HIV protease inhibitor ritonavir by competitive ELISA

The HIV protease inhibitor ritonavir (Norvir; ABT-578), currently used in combination with nucleoside analogs and other protease inhibitors in anti-HIV therapy, has previously been quantified by an HPLC procedure. Here, we report the first convenient one-step competitive ELISA for measuring plasma and intracellular ritonavir in HIV patients. Anti-ritonavir antibody was raised in rabbits using ritonavir-KLH conjugate as immunogen, and the enzymatic tracer was prepared by coupling the drug to acetylcholine esterase. Samples for analysis were first extracted with methanol. Bound/free separation was achieved in a microtiter plate previously coated with anti rabbit IgG monoclonal antibody. Fifty percent inhibition was observed at 1 ng/ml ritonavir and the method accurately and specifically detected as little as 3-4 ng/ml of plasma ritonavir as well as intracellular drug in the peripheral blood mononuclear cells of patients undergoing ritonavir therapy. Within-run and day to day coefficients of variation were below 10% and the drugs currently used in HIV therapy did not interfere with the test. The ELISA was applied to the measurement of plasma ritonavir and to the determination of the extracellular/intracellular drug level ratios in HIV patients receiving long-term multidrug therapy.

Combination of Protease Inhibitors for the Treatment of HIV-1-Infected Patients: A Review of Pharmacokinetics and Clinical Experience

The use of highly active antiretroviral therapy, the combination of at least three different antiretroviral drugs for the treatment of HIV-1 infection, has greatly improved the prognosis for HIV-1-infected patients. The efficacy of a combination of a protease inhibitor (PI) plus two nucleoside analogue reverse transcriptase inhibitors has been well established over a period of up to 3 years. However, virological treatment failure has been reported in 40–60% of unselected patients within 1 year after initiation of a PI-containing regimen. This observation may, at least in part, be attributed to the poor pharmacokinetic characteristics of the PIs. Given as a single agent the PIs have several pharmacokinetic limitations; relatively short plasma-elimination half-lives and a modest and variable oral bioavailability, which is, for some of the PIs, influenced by food. To overcome these suboptimal pharmacokinetics, high doses (requiring large numbers of pills) must be ingested, often with food restrictions, which complicates patient adherence to the prescribed regimen.

Positive drug–drug interactions increase the exposure to the PIs, allowing administration of lower doses at reduced dosing frequencies with less dietary restrictions. In addition to increasing the potency of an antiretroviral regimen, combinations of PIs may enhance patient adherence, both of which will contribute to a more durable suppression of viral replication. The favourable pharmacokinetics of PIs in combination are a result of interactions through cytochrome P450 3A4 (CYP3A4) isoenzymes and, possibly, the multi-drug transporting P-glycoprotein (P-gp). Antiretroviral synergy between PIs and non-overlapping primary resistance patterns in the HIV-1 protease genome may further enhance the anti-retroviral potency and durability of combinations of PIs. Many combinations contain ritonavir because this PI has the most pronounced inhibiting effects on CYP3A4. The combination of saquinavir and ritonavir, both in a dose of 400 mg twice-a-day, is the most studied double PI combination, with clinical experience extending over 3 years. Combination of a PI with a low dose of ritonavir (≤400 mg/day), only to boost its pharmacokinetic properties, seems an attractive option for patients who cannot tolerate higher doses of ritonavir. A recently introduced PI, lopinavir, has been co-formulated with low-dose ritonavir, which allows for a convenient three-capsules, twice-a-day dosing regimen. In an attempt to prolong suppression of viral replication combinations of PIs are becoming increasingly popular. However, further clinical studies are needed to identify the optimal combinations for treatment of antiretroviral naive and experienced HIV-1-infected patients. This review covers combinations of saquinavir, indinavir, nelfinavir, amprenavir and lopinavir with different doses of ritonavir, as well as the combinations of saquinavir and indinavir with nelfinavir.

High indinavir Cmin is associated with higher toxicity in patients on indinavir-ritonavir 800/100 mg twice-daily regimen

We retrospectively evaluated the incidence of side effects and treatment intervention according to indinavir trough concentration in 63 patients taking indinavir-ritonavir 800/100 mg twice daily. Median indinavir trough concentration was 1446 ng/mL at 800/100 mg twice daily associated with 60% of measured toxicity. Among patients with indinavir trough concentration >500 ng/mL, 46 of 49 had a dosage adjustment and 17 have had more than two dosage adjustments. The primary reason for dosage adjustment was toxicity in 69% (43 cases). Renal and cutaneous toxicity were predominant.After dosage adjustment, median indinavir trough concentration was 459 ng/mL, which was associated with 8% of toxicity. Trough concentrations >500 ng/mL were correlated with increased toxicity (p <.05) and more treatment intervention (p =.02). In conclusion, achievement of indinavir trough concentrations <500 ng/mL appears to be safe, and an optimal concentration range for indinavir trough concentration could be 150 to 500 ng/mL for an indinavir-ritonavir twice daily regimen.

HIV-1 protease inhibitors in development

Several pharmaceutical companies have developed an increasing number of second generation protease inhibitors (PI) during the last few years. Many of these compounds have been in preclinical trials and some are now in clinical use. All drugs in this category have been designed to be well absorbed and overcome the crucial problem of cross-resistance within this class of compounds. Taking into account the rapid occurrence of PI cross-resistance, clinicians who are treating patients with the HIV-1 infection will need new active PIs in the near future. The clinical and antiviral efficacy of the new molecules versus the older PIs will be investigated through comparative trials that are likely to be completed over the next 12 months. These third-generation PIs currently in development will be the subject of our review.

Long-term efficacy and safety of ritonavir/indinavir at 400/400 mg twice a day in combination with two nucleoside reverse transcriptase inhibitors as first line antiretroviral therapy

OBJECTIVE

To determine the long-term antiretroviral efficacy and tolerability of dual protease inhibitor (PI) therapy with indinavir (IDV)/ritonavir (RTV) at 400/400 mg twice a day (BID) in combination with two nucleoside reverse trancriptase inhibitors (NRTIs).

DESIGN AND METHODS

In an open-label, uncontrolled multicentre clinical trial, antiretroviral therapy naive patients (n = 93) with a high median baseline HIV-1 RNA level of 210 000 copies/mL (range 17 000-2 943 000) and a median CD4 cell count of 195 copies/microL (range 4-656 copies/microL) were started on a regimen of either zidovudine (ZDV)/lamivudine (3TC) (49%), stavudine (d4T)/3TC (38%) or d4T/didanosine (ddI) (14%) plus RTV and IDV, each at 400 mg BID. CD4 cell counts and HIV RNA were determined at 4-week intervals for a duration of 72 weeks. Statistical analysis was performed on treatment as well as by intent to treat, where missing values were counted as failures.

RESULTS

HIV RNA levels below the limit of detection were achieved in 59.5% (< 80 copies/mL) and 63% (< 500 copies/mL) of patients according to the intent to treat analysis at week 72. In the on treatment analysis, the proportion of patients reaching an undetectable viral load was 94.5% (< 80 copies/mL) and 100% (< 500 copies/mL), respectively. Apart from diarrhoea and nausea, serum lipid abnormalities were identified as the most prominent adverse reaction. No cases of nephrotoxicity occurred during the entire observation period of 72 weeks.

CONCLUSIONS

Our results demonstrate that quadruple therapy with RTV/IDV and two NRTIs induces potent, durable and safe HIV suppression and might be particularly beneficial as a first line therapy for patients with a high baseline viral load.

Pharmacokinetic profile and tolerability of indinavir-ritonavir combinations in healthy volunteers

This was a randomized, double-blind, placebo-controlled parallel study in human immunodeficiency virus type 1 (HIV-1)-uninfected healthy subjects to investigate the pharmacokinetic interaction between indinavir (IDV) and ritonavir (RTV). Subjects were allocated to treatment groups of IDV given with RTV in the following milligram doses twice daily: 800 mg of IDV-100 mg of RTV (800-100 mg), 800-200, 800-400, and 400-400 mg, placebo of IDV with RTV doses of 100, 200, and 400 mg, and placebo of both IDV and RTV. Doses of both drugs were administered for 14 days with a low-fat meal and one dose on day 15 with a high-fat meal. Blood was obtained for drug concentration measurements on days 14 and 15. Seventy-three volunteers enrolled in the study: 29 men and 44 women. Fifty-three volunteers completed the study. When compared to standard historical data for 800 mg of IDV every 8 h (q8h), the IDV area under the concentration-time curve for 24 h (AUC(24)) of IDV-RTV regimens 400-400, 800-100, and 800-200 mg were at least 1.4, 2.3, and 3.3 times higher, respectively, regardless of meal. The concentrations at the end of the dosing interval were 10 to 25 times higher than that observed in the standard regimen of 800 mg of IDV q8h for IDV-RTV 800-100 and 800-200 mg regimens, respectively. RTV at 200 mg maximally enhanced the IDV profile. Improved tolerability was associated with IDV-RTV 800-100 mg versus IDV-RTV 800-200, 800-400, and 400-400 mg q12h. The advantages of IDV-RTV twice daily over 800 mg of IDV q8h include no food restrictions and twice-daily dosing. Also, the regimens achieve levels of IDV that may be helpful in suppressing strains of HIV-1 that have reduced susceptibility to IDV or other protease inhibitors.

Dual protease inhibitor therapy in the management of the HIV-1

Throughout the first 20 years of the HIV-1 epidemic, there have been tremendous advances in the development of antiretroviral therapy (ART). In 1995, the availability of protease inhibitors (PI) as part of triple drug regimens resulted in durable viral suppression with an associated decline in HIV-1-related morbidity and mortality. Despite this early success, limitations of therapy have become apparent. In particular, the need for highly potent antiviral regimens, the importance of outstanding adherence to therapy, drug-related toxicity and the increasing problem of drug-drug and drug-food interactions. Dual PI therapy has been investigated with the hope of overcoming these problems. Select PI combinations may result in synergistic antiviral activity with enhanced viral suppression. Moreover, the ability of select agents to inhibit the cytochrome P450 (CYP450) system results in pharmacologic enhancement that allows for dosing with fewer pills on a less frequent basis, both of which can enhance drug adherence. Furthermore, these pharmacologic interactions can overcome drug-drug and drug-food interactions. Finally, the ability to increase drug levels using certain PI combinations may allow for drug concentrations to exceed those needed to inhibit resistant strains of HIV-1. The rationale for using dual PI therapy, along with the results of clinical trials using various PI combinations in treatment-naïve and experienced patients, is reviewed in this article.