Combination therapy containing ritonavir plus saquinavir has superior short-term antiretroviral efficacy: a randomized trial

Synthetic routes and structure-activity relationships (SAR) of anti-HIV agents: A key review

The worldwide increase of AIDS, an epidemic infection in constant development has an essential and still requires potent antiretroviral chemotherapeutic agents for reducing the integer of deaths caused by HIV. Thus, there is an urgent need for new anti-HIV drug candidates with increased strength, new targets, superior pharmacokinetic properties, and compact side effects. From this viewpoint, we first review present strategies of anti-HIV drug innovation and the synthesis of heterocyclic or natural compound as anti-HIV agents for facilitating the development of more influential and successful anti-HIV agents.

Quadruple versus triple combination antiretroviral therapies for treatment naive people with HIV: systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effects of four drug (quadruple) versus three drug (triple) combination antiretroviral therapies in treatment naive people with HIV, and explore the implications of existing trials for clinical practice and research.

DESIGN

Systematic review and meta-analysis of randomised controlled trials.

DATA SOURCES

PubMed, EMBASE, CENTRAL, Web of Science, and the Cumulative Index to Nursing and Allied Health Literature from March 2001 to December 2016 (updated search in PubMed and EMBASE up to June 2018); and reference lists of eligible studies and related reviews.

STUDY SELECTION

Randomised controlled trials comparing quadruple with triple combination antiretroviral therapies in treatment naive people with HIV and evaluating at least one effectiveness or safety outcome.

REVIEW METHODS

Outcomes of interest included undetectable HIV-1 RNA, CD4 T cell count, virological failure, new AIDS defining events, death, and severe adverse effects. Random effects meta-analyses were conducted.

RESULTS

Twelve trials (including 4251 people with HIV) were eligible. Quadruple and triple combination antiretroviral therapies had similar effects on all relevant effectiveness and safety outcomes, with no point estimates favouring quadruple therapy. With the triple therapy as the reference group, the risk ratio was 0.99 (95% confidence interval 0.93 to 1.05) for undetectable HIV-1 RNA, 1.00 (0.90 to 1.11) for virological failure, 1.17 (0.84 to 1.63) for new AIDS defining events, 1.23 (0.74 to 2.05) for death, and 1.09 (0.89 to 1.33) for severe adverse effects. The mean difference in CD4 T cell count increase between the two groups was -19.55 cells/μL (-43.02 to 3.92). In general, the results were similar, regardless of the specific regimens of combination antiretroviral therapies, and were robust in all subgroup and sensitivity analyses.

CONCLUSION

In this study, effects of quadruple combination antiretroviral therapy were not better than triple combination antiretroviral therapy in treatment naive people with HIV. This finding lends support to current guidelines recommending the triple regimen as first line treatment. Further trials on this topic should be conducted only when new research is justified by adequate systematic reviews of the existing evidence. However, this study cannot exclude the possibility that quadruple cART would be better than triple cART when new classes of antiretroviral drugs are made available.

Changes in first-line cART regimens and short-term clinical outcome between 1996 and 2010 in The Netherlands

OBJECTIVES

Document progress in HIV-treatment in The Netherlands since 1996 by reviewing changing patterns of cART use and relating those to trends in patients' short-term clinical outcomes between 1996 and 2010.

DESIGN AND METHODS

1996-2010 data from 10,278 patients in the Dutch ATHENA national observational cohort were analysed. The annual number of patients starting a type of regimen was quantified. Trends in the following outcomes were described: i) recovery of 150 CD4 cells/mm(3) within 12 months of starting cART; ii) achieving viral load (VL) suppression ≤1,000 copies/ml within 12 months of starting cART; iii) switching from first-line to second-line regimen within three years of starting treatment; and iv) all-cause mortality rate per 100 person-years within three years of starting treatment.

RESULTS

Between 1996 and 2010, first-line regimens changed from lamivudine/zidovudine-based or lamivudine/stavudine-based regimens with unboosted-PIs to tenofovir with either emtricitabine or lamivudine with NNRTIs. Mortality rates did not change significantly over time. VL suppression and CD4 recovery improved over time, and the incidence of switching due to virological failure and toxicity more than halved between 1996 and 2010. These effects appear to be related to the use of new regimens rather than improvements in clinical care.

CONCLUSION

The use of first-line cART in the Netherlands closely follows changes in guidelines, to the benefit of patients. While there was no significant improvement in mortality, newer drugs with better tolerability and simpler dosing resulted in improved immunological and virological recovery and reduced incidences of switching due to toxicity and virological failure.

Feline immunodeficiency virus (FIV) as a model for study of lentivirus infections: parallels with HIV

FIV is a significant pathogen in the cat and is, in addition, the smallest available natural model for the study of lentivirus infections. Although divergent at the amino acid level, the cat lentivirus has an abundance of structural and pathophysiological commonalities with HIV and thus serves well as a model for development of intervention strategies relevant to infection in both cats and man. The following review highlights both the strengths and shortcomings of the FIV/cat model, particular as regards development of antiviral drugs.

The cost-effectiveness of counseling strategies to improve adherence to highly active antiretroviral therapy among men who have sex with men

OBJECTIVE

Inadequate adherence to highly active antiretroviral therapy (HAART) may lead to poor health outcomes and the development of HIV strains that are resistant to HAART. The authors developed a model to evaluate the cost-effectiveness of counseling interventions to improve adherence to HAART among men who have sex with men (MSM).

METHODS

The authors developed a dynamic compartmental model that incorporates HIV treatment, adherence to treatment, and infection transmission and progression. All data estimates were obtained from secondary sources. The authors evaluated a counseling intervention given prior to initiation of HAART and before all changes in drug regimens, combined with phone-in support while on HAART. They considered a moderate-prevalence and a high-prevalence population of MSM.

RESULTS

If the impact of HIV transmission is ignored, the counseling intervention has a cost-effectiveness ratio of $25,500 per quality-adjusted life year (QALY) gained. When HIV transmission is included, the cost-effectiveness ratio is much lower: $7400 and $8700 per QALY gained in the moderate- and high-prevalence populations, respectively. When the intervention is twice as costly per counseling session and half as effective as estimated in the base case (in terms of the number of individuals who become highly adherent, and who remain highly adherent), then the intervention costs $17,100 and $19,600 per QALY gained in the 2 populations, respectively.

CONCLUSIONS

Counseling to improve adherence to HAART increased length of life, modestly reduced HIV transmission, and cost substantially less than $50,000 per QALY gained over a wide range of assumptions but did not reduce the proportion of drug-resistant strains. Such counseling provides only modest benefit as a tool for HIV prevention but can provide significant benefit for individual patients at an affordable cost.

Molecular mechanisms of FIV infection

Feline immunodeficiency virus (FIV) is an important viral pathogen worldwide in the domestic cat, which is the smallest animal model for the study of natural lentivirus infection. Thus, understanding the molecular mechanisms by which FIV carries out its life cycle and causes an acquired immune deficiency syndrome (AIDS) in the cat is of high priority. FIV has an overall genome size similar to HIV, the causative agent of AIDS in man, and shares with the human virus genomic features that may serve as common targets for development of broad-based intervention strategies. Specific targets include enzymes encoded by the two lentiviruses, such as protease (PR), reverse transcriptase (RT), RNAse H, and integrase (IN). In addition, both FIV and HIV encode Vif and Rev elements essential for virus replication and also share the use of the chemokine receptor CXCR4 for entry into the host cell. The following review is a brief overview of the current state of characterization of the feline/FIV model and development of its use for generation and testing of anti-viral agents.

Unmeasured confounding caused slightly better response to HAART within than outside a randomized controlled trial

OBJECTIVE

To compare the outcome of highly active antiretroviral therapy (HAART) in HIV-infected patients initiating equivalent regimens within and outside a randomized controlled trial (RCT).

STUDY DESIGN AND SETTING

The Danish Protease Inhibitor Study (DAPIS) was a national multicenter RCT comparing initial treatment with indinavir, ritonavir, or saquinavir/ritonavir during 96 weeks. From the Danish HIV Cohort Study we identified all patients initiating one of these protease-inhibitor-based HAART regimens: 425 patients within DAPIS and 677 outside the trial. We compared viral load, CD4 count response, and mortality.

RESULTS

At weeks 96 and 240, trial participants were more likely than nonparticipants to have undetectable viral load (adjusted odds ratio [adOR] 1.28 [95% CI=0.94-1.74] and 1.70 [95% CI=1.16-2.50]) and a CD4 increase > or =100 cells/microl (adOR 1.37 [95% CI=1.03-1.82] and 1.53 [95% CI=1.04-2.25]). For antiretroviral-experienced, but not for antiretroviral-naïve patients, trial participants had a lower risk of death (mortality rate ratio [MRR]=0.46 [95% CI=0.27-0.77]) than nonparticipants. This effect was moderated in adjusted analyses (MRR=0.60 [0.33-1.07]).

CONCLUSIONS

Compared to nontrial patients, trial participants had better response to HAART. The differences were small defying the notion that results obtained in RCTs are unachievable in routine clinical practice.

An HIV-preventive intervention for youth living with HIV

As the number of youth infected with HIV rises, secondary prevention programs are needed to help youth living with HIV meet three goals: (a) increase self-care behaviors, medical adherence, and health-related interactions; (b) reduce transmission acts; and (c) enhance their quality of life. This article describes an intervention program for youth living with HIV. Youth engage in small-group activities with other infected peers to modify their behavioral patterns. The intervention aims to (a) reduce substance use and sexual behaviors that may transmit or enhance transmission of the HIV virus; (b) reduce negative impacts of substance use on seeking and utilizing health care, assertiveness, and adherence to health regimens; and (c) enhance the quality of life to maintain behavior changes over time. Interventions that target youth living with HIV are warranted. A variety of delivery strategies are discussed for secondary interventions.

[Recommendations from the GESIDA/Spanish AIDS Plan regarding antiretroviral treatment in adults with human immunodeficiency virus infection (update January 2007)]

OBJECTIVE

This consensus document is an update of antiretroviral therapy (ART) recommendations for adult patients infected with the human immunodeficiency virus (HIV-1).

METHODS

To formulate these recommendations, a panel composed of members of the Grupo de Estudio de Sida (GESIDA; AIDS Study Group) and the Plan Nacional sobre el Sida (PNS; Spanish AIDS Plan) reviewed the advances in the current understanding of the pathophysiology of HIV, the safety and efficacy findings from clinical trials, and the results from cohort and pharmacokinetic studies published in biomedical journals or presented at scientific meetings over the last years. Three levels of evidence were defined according to the source of the data: randomized studies (level A), cohort or case-control studies (level B), and expert opinion (level C). The decision to recommend, consider or not recommend ART was established in each situation.

RESULTS

Currently, the treatment of choice for chronic HIV infection is the combination of three drugs of two different classes, including 2 nucleosides or nucleotide analogs (NRTI) plus 1 non-nucleoside (NNRTI) or 1 boosted protease inhibitor (PI/r). Initiation of ART is recommended in patients with symptomatic HIV infection. In asymptomatic patients, initiation of ART is recommended on the basis of CD4+ lymphocyte counts and plasma viral load, as follows: 1) therapy should be started in patients with CD4+ counts of < 200 cells/microl; 2) therapy should be started in most patients with CD4+ counts of 200-350 cells/microl, although it can be delayed when CD41 count persists at around 350 cells/microL and viral load is low, and 3) initiation of therapy can be delayed in patients with CD4+ counts of > 350 cells/microL. The initial objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining the antiviral response. Therapeutic options are limited with the development of cross resistance and ART failure. Genotype studies are useful in these cases. More information regarding the studies analyzed and the panel recommendations for adherence, toxicity, treatment during pregnancy, patients with hepatitis B or C virus co-infection, and post-exposure prophylaxis can be accessed at www.gesida.seimc.org.

CONCLUSIONS

CD4+ lymphocyte count is the most important reference factor for initiating ART in asymptomatic patients. The large number of available drugs, the increased sensitivity of tests to monitor viral load, and the ability to determine viral resistance is leading to a more individualized approach to therapy.

Updated clinical pharmacologic considerations for HIV-1 protease inhibitors

Many data associate low protease inhibitor plasma concentrations with suboptimal virologic responses, whereas fewer data associate high plasma concentrations with toxicity. Knowledge of relationships between concentrations and virologic response is important because significant variability in concentrations exists among patients. For antiretroviral-naïve patients, target trough concentrations have been suggested on the basis of retrospective associations with virologic responses. Two prospective studies demonstrated improved virologic responses when indinavir and nelfinavir doses were managed based on these troughs. Investigations among antiretroviral-experienced patients have identified a relationship between the trough concentration and the in-vitro susceptibility of the patient's virus with virologic outcome. However, differences in virologic response may further depend on other pharmacologic factors, such as protein binding, intracellular kinetics, function of drug transporters, and the activity of other drugs in the regimen. In the future, dosing strategies that accommodate the variability in pharmacokinetics and pharmacodynamics may improve virologic outcomes.

Declining risk of triple-class antiretroviral drug failure in Danish HIV-infected individuals

OBJECTIVES

To analyse the incidence, prevalence, and predictors for development of triple-class antiretroviral drug failure (TCF) in individuals infected with HIV.

DESIGN

Population-based observational cohort study from 1 January 1995 to 31 December 2003, focusing on all 2722 recipients of highly active antiretroviral therapy (HAART) in Denmark.

METHODS

We used person-years analysis, Kaplan-Meier survival curves and Cox regression analysis. TCF was defined as a minimum of 120 days with viral load > 1000 copies/ml on treatment with each of the three major drug classes.

RESULTS

We observed 177 TCFs, yielding a crude incidence rate (IR) of 1.8 per 100 person-years [95% confidence interval (CI), 1.6-2.1]. Seven years after initiation of HAART, 17.2% (95% CI, 14.5-20.5) of antiretroviral (ART)-experienced patients, but only 7.0% (95% CI, 4.3-11.2) of ART-naive patients were estimated to have failed. After an initial rise, the IR from the third to the sixth year of HAART declined significantly for ART-experienced patients [incidence rate ratio (IRR), 0.80 per year (95% CI, 0.66-0.97); P = 0.022], and non-significantly for ART-naive patients [IRR, 0.79 per year (95% CI, 0.53-1.18); P = 0.255]. The IR for all patients being followed each year declined from 1997 to 2003 [IRR, 0.88 (95% CI, 0.81-0.96); P = 0.002]. The prevalence of TCF remained stable at less than 7% after 2000. Predictors of TCF at commencement of HAART were a CD4 cell count below 200, a previous AIDS-defining event, previous antiretroviral exposure, earlier year of HAART initiation, and young age.

CONCLUSIONS

The risk of TCF is declining in Denmark and the prevalence remains stable.

Cost-effectiveness of screening for HIV in the era of highly active antiretroviral therapy

BACKGROUND

The costs, benefits, and cost-effectiveness of screening for human immunodeficiency virus (HIV) in health care settings during the era of highly active antiretroviral therapy (HAART) have not been determined.

METHODS

We developed a Markov model of costs, quality of life, and survival associated with an HIV-screening program as compared with current practice. In both strategies, symptomatic patients were identified through symptom-based case finding. Identified patients started treatment when their CD4 count dropped to 350 cells per cubic millimeter. Disease progression was defined on the basis of CD4 levels and viral load. The likelihood of sexual transmission was based on viral load, knowledge of HIV status, and efficacy of counseling.

RESULTS

Given a 1 percent prevalence of unidentified HIV infection, screening increased life expectancy by 5.48 days, or 4.70 quality-adjusted days, at an estimated cost of 194 dollars per screened patient, for a cost-effectiveness ratio of 15,078 dollars per quality-adjusted life-year. Screening cost less than 50,000 dollars per quality-adjusted life-year if the prevalence of unidentified HIV infection exceeded 0.05 percent. Excluding HIV transmission, the cost-effectiveness of screening was 41,736 dollars per quality-adjusted life-year. Screening every five years, as compared with a one-time screening program, cost 57,138 dollars per quality-adjusted life-year, but was more attractive in settings with a high incidence of infection. Our results were sensitive to the efficacy of behavior modification, the benefit of early identification and therapy, and the prevalence and incidence of HIV infection.

CONCLUSIONS

The cost-effectiveness of routine HIV screening in health care settings, even in relatively low-prevalence populations, is similar to that of commonly accepted interventions, and such programs should be expanded.

Assessment of FIV-C infection of cats as a function of treatment with the protease inhibitor, TL-3

Background

The protease inhibitor, TL-3, demonstrated broad efficacy in vitro against FIV, HIV and SIV (simian immunodeficiency virus), and exhibited very strong protective effects on early neurologic alterations in the CNS of FIV-PPR infected cats. In this study, we analyzed TL-3 efficacy using a highly pathogenic FIV-C isolate, which causes a severe acute phase immunodeficiency syndrome, with high early mortality rates.

Results

Twenty cats were infected with uncloned FIV-C and half were treated with TL-3 while the other half were left untreated. Two uninfected cats were used as controls. The general health and the immunological and virological status of the animals was monitored for eight weeks following infection. All infected animals became viremic independent of TL-3 treatment and seven of 20 FIV-C infected animals developed severe immunodepletive disease in conjunction with significantly (p ≤ 0.05) higher viral RNA loads as compared to asymptomatic animals. A marked and progressive increase in CD8⁺ T lymphocytes in animals surviving acute phase infection was noted, which was not evident in symptomatic animals (p ≤ 0.05). Average viral loads were lower in TL-3 treated animals and of the 6 animals requiring euthanasia, four were from the untreated cohort. At eight weeks post infection, half of the TL-3 treated animals and only one of six untreated animals had viral loads below detection limits. Analysis of protease genes in TL-3 treated animals with higher than average viral loads revealed sequence variations relative to wild type protease. In particular, one mutant, D105G, imparted 5-fold resistance against TL-3 relative to wild type protease.

Conclusions

The findings indicate that the protease inhibitor, TL-3, when administered orally as a monotherapy, did not prevent viremia in cats infected with high dose FIV-C. However, the modest lowering of viral loads with TL-3 treatment, the greater survival rate in symptomatic animals of the treated cohort, and the lower average viral load in TL-3 treated animals at eight weeks post infection is indicative of a therapeutic effect of the compound on virus infection.

Resolution and prevention of feline immunodeficiency virus-induced neurological deficits by treatment with the protease inhibitor TL-3

In vivo tests were performed to assess the influence of the protease inhibitor TL-3 on feline immunodeficiency virus (FIV)-induced central nervous system (CNS) deficits. Twenty cats were divided into four groups of five animals each. Group 1 received no treatment, group 2 received TL-3 only, group 3 received FIV strain PPR (FIV-PPR) only, and group 4 received FIV-PPR and TL-3. Animals were monitored for immunological and virological status, along with measurements of brain stem auditory evoked potential (BAEP) changes. Groups 1 and 2 remained FIV negative, and groups 3 and 4 became virus positive and seroconverted by 3 to 5 weeks postinoculation. No adverse effects were noted with TL-3 only. The average peak viral load for the virus-only group 3 animals was 1.32 x 10(6) RNA copies/ml, compared to 6.9 x 10(4) copies/ml for TL-3-treated group 4 cats. Group 3 (virus-only) cats exhibited marked progressive delays in BAEPs starting at 2 weeks post virus exposure, which is typical of infection with FIV-PPR. In contrast, TL-3-treated cats of group 4 exhibited BAEPs similar to those of control and drug-only cats. At 97 days postinfection, treatments were switched; i.e., group 4 animals were taken off TL-3 and group 3 animals were treated with TL-3. BAEPs in group 3 animals returned to control levels, while BAEPs in group 4 animals remained at control levels. After 70 days on TL-3, group 3 was removed from the drug treatment regimen. Delays in BAEPs immediately increased to levels observed prior to TL-3 treatment. The findings show that early TL-3 treatment can effectively eliminate FIV-induced changes in the CNS. Furthermore, TL-3 can counteract FIV effects on the CNS of infected cats, although continued treatment is required to maintain unimpaired CNS function.

Clinical trial methodology and clinical cohorts: the importance of complete follow-up in trials evaluating the virological efficacy of anti-HIV medicines

PURPOSE OF REVIEW

It has been common practice in randomized trials of HIV medicines to classify switches away from the original therapy as failures in analyses of virological effect, in line with an HIV-RNA measurement above a given level of quantification. This approach precludes the ability to identify the possible effects of a given therapy on those of a subsequent therapy. This review explores whether there have been changes in the reporting of randomized trials since the importance of continuous follow-up throughout the study period was initially raised 2 years ago.

RECENT FINDINGS

Follow-up is still likely to be discontinued at a premature switch from study medication in a large number of the randomized trials published in 2002-2003. However, some studies, all initiated by investigators, did follow patients throughout the study period. In three of the studies, the proportions of patients with virological failure assessed with and without data after the premature discontinuation of randomized therapy could be elicited. Substantial differences were seen in the comparisons of two highly active antiretroviral therapy regimens according to the choice of analytical approach. In all three studies significant differences were observed between the regimens according to one approach, but not to the other.

SUMMARY

The notation of treatment switch equals failure leads to an imprecise measurement of virological effect, and complete follow-up throughout the study period should be strongly encouraged, thus enabling several supplementary analyses of the virological effect of the treatment strategies being compared.

Evolving therapeutic paradigms for HIV and HCV

The continued development of enabling molecular technologies that can be employed to better understand viral replication and the action of currently available therapeutic agents promises to lead to the development of the next generation of drugs with improved therapeutic utility against human immunodeficiency virus (HIV) and hepatitis C virus (HCV). New therapeutic approaches have been developed for treating HIV and HCV infections, but key technical and therapeutic challenges must be addressed to further advance treatment options in each of these areas.

A Randomized Trial Comparing Initial Haart Regimens of Nelfinavir/Nevirapine and Ritonavir/Saquinavir in Combination with Two Nucleoside Reverse Transcriptase Inhibitors

Background

A triple-class HAART regimen may be associated with a better virological effect than conventional regimens, but may also lead to toxicity and more profound resistance.

Methods

Randomized, controlled, open-label trial of 233 protease inhibitor- and non-nucleoside reverse transcriptase inhibitor-naive HIV-infected patients allocated to a regimen of nelfinavir and nevirapine (1250/200 mg twice daily; n=118) or ritonavir and saquinavir (400/400 mg twice daily; n=115), both in combination with two nucleoside reverse transcriptase inhibitors. The primary end-point was HIV RNA ≤20 copies/ml after 48 weeks (missing value=failure). Patients remained under follow-up also in case of switch from the randomized therapy.

Results

At baseline, the median CD4 cell counts were 126 (range: 0–942) (nelfinavir/nevirapine) and 150 (0–642) (ritonavir/saquinavir) cells/mm3, and HIV RNA measurements 5.0 copies/ml (1.3–6.4) in both groups. A total of 102 (86%) and 101 (88%) were antiretroviral-naive. Within 48 weeks, 35 and 44% discontinued randomized therapy; P=0.13. Of these, 80 and 73% switched therapy due to adverse events; P=0.99. At week 48, 69 and 56%, respectively, had a HIV RNA ≤20 copies/ml; P=0.037.

Conclusion

A regimen of nelfinavir/nevirapine had a favourable virological effect and tolerability over a 48-week period compared with ritonavir/saquinavir, when administered in combination with two nucleoside reverse transcriptase inhibitors. However, more extensive follow-up is required to determine the long-term consequences of triple class HAART regimens, including the development of broad drug resistance.

Therapeutic management of HIV

Highly active antiretroviral therapy (HAART) has been used to treat HIV for several years with a reduction in mortality and morbidity. However, some patients fail to achieve complete viral suppression. Durability of therapy cannot be guaranteed and cross-resistance may arise, making second-line therapy a complex issue. Toxicity and pharmacokinetic interactions with other drugs may complicate long-term efficacy of regimens. The reduction of viral burden can prevent progressive immunodeficiency and may decrease the risk of selecting resistant viruses. Triple therapy with a protease inhibitor showed a decrease in morbidity, mortality and durability, but protease-sparing therapies might yield fewer side-effects. Lipid-related toxicity of protease inhibitors has resulted in the use of nonnucleoside reverse transcriptase inhibitors (NNRTI) in HAART. However, a single mutation for an NNRTI can confer cross-class resistance that limits further options for second-line therapy. When choosing HAART it is crucial to achieve durability and to structure doses to suit the patient's lifestyle, and it is important for patients to initiate therapy when they are ready. The decision to change drug regimens following treatment failure or rebound will depend on the initial choice of HAART. Viral load reduction occurs rapidly in most patients on HAART but immune reconstitution is slow and occurs almost unaided. Therefore prophylaxis against opportunistic infections should not be stopped prematurely.

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.

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.

"In vitro" antifungal activity of protease inhibitors

In the last five years, as HAART has become standard therapy in HIV seropositive or AIDS patients, changes have been noted in the numbers and types of opportunistic fungal infections in these cohorts of patients. Particularly, oropharyngeal candidiasis have become rare in HIV infected patients since the introduction of new anti-HIV drugs of the protease inhibitors type. At the Immunology Institute of the Universidad Central de Venezuela the most frequent protease inhibitors (PIs) used for the treatment of these patients have been: Nelfinavir (Viracept, Roche), Indinavir (Crixivan Merck), Ritonavir (Norvir, Abbott), Saquinavir (Fortovase, Roche). Recently, we observed that recurrent candidiasis was less frequent and no Candida could be isolated in our patients. A direct relation to the PIs was suspected. In order to assess the "in vitro" antifungal activity of the afore mentioned protease inhibitors on Candida sp., we used both the well diffusion test and the NCCLS broth microdilution test to assay 100 Candida sp. isolates from HIV seropositive or AIDS patients with syntomatic oropharyngeal Candida infection. In general, the data obtained with the well diffusion test were in agreement with those obtained by the broth microdilution test. All 100 isolates were susceptible to Saquinavir and 32 were susceptible to Indinavir using the NCCLS microdilution test, while 97 were susceptible to Saquinavir and 52 to Indinavir by the well diffusion test. From 17 C. albicans resistant to fluconazole, all were susceptible to Saquinavir by the NCCLS micromethod and 16 by the well diffusion test. Our results showed anticandidal activity "in vitro" of PIs, mainly Saquinavir.

[Recommendations of the Spanish AIDS Study Group (GESIDA) and the National Aids Plan (PNS) for antiretroviral treatment in adult patients with human immunodeficiency virus infection in 2002]

OBJECTIVE

To provide an update of recommendation on antiretroviral treatment (ART) in HIV-infected adults.Methods. These recommendations have been agreed by consensus by a committee of the spanish AIDS Study Group (GESIDA) and the National AIDS Plan. To do so, advances in the physiopathology of AIDS and the results on efficacy and safety in clinical trials, cohort and pharmacokinetics studies published in biomedical journals or presented at congresses in the last few years have been reviewed. Three levels of evidence have been defined according to the data source: randomized studies (level A), case-control or cohort studies (level B) and expert opinion (level C). Whether to recommend, consider, or not to recommend ART has been established for each situation.

RESULTS

Currently, ART with combinations of at least three drugs constitutes the treatment of choice in chronic HIV infection. In patients with symptomatic HIV infection, initiation of ART is recommended. In asymptomatic patients initiation of ART should be based on the CD41/mL lymphocyte count and on the plasma viral load (PVL): a) in patients with CD41 lymphocytes < 200 cells/mL, initiation of ART is recommended; b) in patients with CD41 lymphocytes between 200 and 300 cells/mL, initiation of ART should, in most cases, be recommended; however, it could be delayed when the CD41 lymphocyte count remains close to 350 cells/mL and the PVL is low, and c) in patients with CD41 lymphocytes > 350 cells/mL, initiation of ART can be delayed. The aim of ART is to achieve an undetectable PVL. Adherence to ART plays a role in the durability of the antiviral response. Because of the development of cross-resistance, the therapeutic options in treatment failure are limited. In these cases, genotypic analysis is useful. Toxicity limits ART. The criteria for ART in acute infection, pregnancy and postexposure prophylaxis and in the management of coinfection with HIV and hepatitis C and B virus are controversial.

CONCLUSIONS

The current approach to initiating ART is more conservative than in previous recommendations. In asymptomatic patients, the CD41 lymphocyte count is the most important reference factor for initiating ART. Because of the considerable number of drugs available, more sensitive monitoring methods (PVL) and the possibility of determining resistance, therapeutic strategies have become much more individualized.

Ritonavir/Saquinavir plus One Nucleoside Reverse Transcriptase Inhibitor (NRTI) versus Indinavir plus Two Nrtis in Protease Inhibitor-Naive HIV-1-Infected Adults (Iris Study)

Objectives

To compare the efficacy, tolerability and safety of a ritonavir 400 mg/saquinavir hard gel fomulation 400 mg twice daily versus an indinavir 800 mg once every 8 h containing first-line protease inhibitor (PI) treatment regimen.

Methods

Open, randomized, multicentre clinical trial. PI-naive patients received either ritonavir/saquinavir and one nucleoside reverse transcriptase inhibitor (NRTI) or indinavir and two NRTIs. Intention-to-treat (ITT) and on-treatment (OT) analyses were performed.

Results

The baseline characteristics of the study participants were similar in both arms, 67 patients (37%) were naive to antiretroviral treatment. The proportion of patients who achieved a plasma viral load below the level of detection of 400 copies/ml at week 48 was 43% (39/90) in the ritonavir/saquinavir arm and 63% (57/90) in the indinavir arm ( P=0.005, ITT analysis). Using an OT analysis, these percentages were 84% and 88%, respectively ( P=0.6). There were more drop-outs in the ritonavir/saquinavir arm than in the indinavir arm (35.6% (32/90) versus 15.6% (14/90), P=0.002), mainly due to gastro-intestinal side-effects. Abnormal liver tests and increased lipids levels were more frequently reported in the ritonavir/saquinavir arm than in the indinavir arm.

Conclusion

In PI-naive patients, indinavir in combination with two NRTIs was more effective and better tolerated than ritonavir/saquinavir plus one NRTI. Both treatments were very effective for patients who were able to tolerate them.

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.

Analysis of Virological Efficacy in Trials of Antiretroviral Regimens: Drawbacks of Not Including Viral Load Measurements after Premature Discontinuation of Therapy

Objectives

To compare two analytic approaches to assess the virological effect of HAART according to the intention-to-treat (ITT) principle.

Material

Data from 2318 patients enrolled in 10 randomised clinical trials (RCTs) and from 3091 patients followed in an observation cohort (EuroSIDA) starting their first HAART regimen.

Methods

Two classifications of defining virological response 48 weeks after starting the therapy to be evaluated were compared: 1) only patients remaining on the therapy and having a plasma viral load (pVL) below a given cut-off level at week 48 were classified as responders (ITT/s=f); and 2) patients with a pVL below a given cut-off at week 48 whether they remained on initial assigned therapy or switched therapy were responders (ITT/s incl). In both analyses, patients with missing data at week 48 were classified as failures (i.e., non-responders).

Results

According to ITT/s=f, 22–70% of the patients starting a HAART regimen in a RCT experienced a virological response at week 48. Only two RCTs had complete follow-up data ( n=424): between 29 and 62% achieved a virological response at week 48 in the six treatment arms evaluated in the studies according to ITT/s=f, and 41–72% according to ITT/s incl. Among those who discontinued the therapy to be evaluated in these two trials, 13–45% (cohort: 39–74%) subsequently experienced a virological response at week 48. The subsequent response rates were associated with the reason for discontinuation (toxicity versus confirmed virological failure: 63 vs 33%), varied largely across regimens and were not associated with the discontinuation rate.

Conclusions

Discontinuation of follow-up at switch from the therapy to be evaluated remains common in anti-retroviral treatment trials, but leads to an imprecise and incomplete assessment of the intrinsic effect of a given regimen. Complete follow-up of all patients should be encouraged strongly as this will allow for several complementary analytic approaches and a focus on optimal treatment strategies rather than specific regimens.

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 1600 mg twice-daily, plus two NRTIs (arm B); saquinavir SGC 1200 mg twice-daily and nelfinavir 1250 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.

Systematic review and meta-analysis of evidence for increasing numbers of drugs in antiretroviral combination therapy

OBJECTIVE

To assess the evidence for the effectiveness of increasing numbers of drugs in antiretroviral combination therapy.

DESIGN

Systematic review, meta-analysis, and meta-regression of fully reported randomised controlled trials. All studies included compared quadruple versus triple therapy, triple versus double therapy, double versus monotherapy, or monotherapy versus placebo or no treatment.

PARTICIPANTS

Patients with any stage of HIV infection who had not received antiretroviral therapy.

MAIN OUTCOME MEASURES

Changes in disease progression or death (clinical outcomes); CD4 count and plasma viral load (surrogate markers).

SEARCH STRATEGY

Six electronic databases, including Medline, Embase, and the Cochrane Library, searched up to February 2001.

RESULTS

54 randomised controlled trials, most of good quality, with 66 comparison groups were included in the analysis. For both the clinical outcomes and surrogate markers, combinations with up to and including three (triple therapy) were progressively and significantly more effective. The odds ratio for disease progression or death for triple therapy compared with double therapy was 0.6 (95% confidence interval 0.5 to 0.8). Heterogeneity in effect sizes was present in many outcomes but was largely related to the drugs used and trial quality.

CONCLUSIONS

Evidence from randomised controlled trials supports the use of triple therapy. Research is needed on the effectiveness of quadruple therapies and the relative effectiveness of specific combinations of drugs.

Plasma drug levels, genotypic resistance, and virological response to a nelfinavir plus saquinavir-containing regimen

OBJECTIVE

To determine the importance of resistance and drug levels in the response to a dual-protease inhibitor (PI) combination.

METHODS

Prospective study of 62 HIV-positive patients who switched to a salvage regimen including nelfinavir plus saquinavir. Virological response was defined as a decrease in viraemia > 0.5 log10 after 24 weeks. Optimal PI levels were defined as those above the protein binding-corrected 95% inhibitory concentration (IC95), as estimated in the presence of 50% human serum.

RESULTS

Baseline median HIV load was 4.78 log10 copies/ml. The median number of mutations in the protease gene was nine (range, 2-25), predominantly at residues 82 (52%), and 90 (40%). After 24 weeks, 45% of patients had responded and 19% were < 50 copies/ml. A higher number of mutations in the protease gene (12 versus 8;P = 0.001), and the L90M mutation (36% versus 67%; P = 0.001) were associated with treatment failure. Trough levels of nelfinavir and saquinavir were two- and fivefold, respectively, greater than those reached when used as the only PI (2480 and 260 ng/ml, respectively), and they were above the estimated protein-corrected IC95 in 96% and 32% of cases. Thus, the Cmin : IC95 ratio ranged from 0.1 to 10 for nelfinavir and from 0.12 to 3.24 for saquinavir. Suboptimal PI levels were associated with a poorer response, but there was no correlation between optimal drug levels and a better response.

CONCLUSION

Genotypic resistance predicts the virological response to a nelfinavir-saquinavir salvage regimen. Our data suggest that higher than optimal drug levels could be necessary to control the replication of many PI-resistant viruses.

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.

Ritonavir-saquinavir dual protease inhibitor compared to ritonavir alone in human immunodeficiency virus-infected patients

The objective of this study was to evaluate the antiretroviral efficacy and safety of ritonavir (600 mg twice a day [b.i.d.])-saquinavir (400 mg b.i.d.) compared to ritonavir (600 mg b.i.d.) in patients pretreated and receiving continued treatment with two nucleoside analogs. The study was placebo controlled, randomized, and double blind. Inclusion criteria included protease inhibitor naive status and a viral load of >10,000 copies/ml. The main end point was viral load at week 24. Forty-seven patients were included (25 given ritonavir and 22 given ritonavir-saquinavir) and monitored until week 48. At inclusion, 23% had had at least one AIDS-defining event. Previous treatment durations (mean and standard deviation) were 42 +/- 25 and 37 +/- 23 months, viral loads were 4.75 +/- 0.62 and 4.76 +/- 0.50 log(10) copies/ml, and CD4 cell counts were 236 +/- 126 and 234 +/- 125/mm(3) in the ritonavir and ritonavir-saquinavir groups, respectively. At week 24, viral loads were 2.81 +/- 1.48 and 2.08 +/- 1.14 log(10) copies/ml (P = 0.04) and CD4 cell counts were 330 +/- 151 and 364 +/- 185/mm(3) (P = 0.49) in the ritonavir and ritonavir-saquinavir groups, respectively. Similar results were observed at week 48. Moreover, at week 48, 40 and 68% (P = 0.05) and 28 and 59% (P = 0.03) of patients achieved viral suppression at below 200 and 50 copies/ml in the ritonavir and ritonavir-saquinavir groups, respectively. At week 24, six patients in the ritonavir group but only one in the ritonavir-saquinavir group had key mutations conferring resistance to protease inhibitors. Clinical and biological tolerances were similar in both groups. In nucleoside analog-pretreated patients, ritonavir-saquinavir has higher antiretroviral efficacy than and is as well tolerated as ritonavir alone.

Viral evolution in response to the broad-based retroviral protease inhibitor TL-3

TL-3 is a protease inhibitor developed using the feline immunodeficiency virus protease as a model. It has been shown to efficiently inhibit replication of human, simian, and feline immunodeficiency viruses and therefore has broad-based activity. We now demonstrate that TL-3 efficiently inhibits the replication of 6 of 12 isolates with confirmed resistance mutations to known protease inhibitors. To dissect the spectrum of molecular changes in protease and viral properties associated with resistance to TL-3, a panel of chronological in vitro escape variants was generated. We have virologically and biochemically characterized mutants with one (V82A), three (M46I/F53L/V82A), or six (L24I/M46I/F53L/L63P/V77I/V82A) changes in the protease and structurally modeled the protease mutant containing six changes. Virus containing six changes was found to be 17-fold more resistant to TL-3 in cell culture than was wild-type virus but maintained similar in vitro replication kinetics compared to the wild-type virus. Analyses of enzyme activity of protease variants with one, three, and six changes indicated that these enzymes, compared to wild-type protease, retained 40, 47, and 61% activity, respectively. These results suggest that deficient protease enzymatic activity is sufficient for function, and the observed protease restoration might imply a selective advantage, at least in vitro, for increased protease activity.

Clinical Pharmacologic Considerations for HIV-1 Protease Inhibitors

Many data associate low protease inhibitor plasma concentrations with suboptimal virologic responses, whereas relatively few data associate high plasma concentrations with increased likelihood of toxicity. Knowledge of relationships between concentrations and virologic response is important because significant variability in plasma concentrations exists among HIV-infected persons. Unfortunately, a prospectively confirmed therapeutic range that reduces the risk of virologic failure has not been established for the protease inhibitors. Recent investigations have identified a relationship between the measured minimum plasma concentration, the in vitro susceptibility of the subject's virus, and virologic outcome. However, differences in virologic response may further depend on other pharmacologic factors such as protein binding, intracellular kinetics, expression of drug transporters, and drug synergies or antagonisms. In the future, dosing strategies that accommodate the variability in both pharmacokinetics and pharmacodynamics may improve virologic outcomes. In summary, clinical pharmacologic considerations for protease inhibitors can be used to promote their optimal use.

Comparison of virologic, immunologic, and clinical response to five different initial protease inhibitor-containing and nevirapine-containing regimens

CONTEXT

The effectiveness of different protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors outside the setting of clinical trials has not been well described.

OBJECTIVES

To compare five different PI-and nevirapine (NVP)-containing regimens on virologic, immunologic, and clinical outcomes and treatment discontinuation.

DESIGN AND SETTING

Observational cohort study based on an HIV clinic in London.

PATIENTS

A total of 690 patients who received either saquinavir hard gel (SQV HG) (n = 183), indinavir (IDV) (n = 189), nelfinavir (NFV) (n = 109), ritonavir (RTV) (n = 42), ritonavir with saquinavir hard gel (RTV/SQV HG) (n = 45), or NVP (n = 122) as part of an initial PI-or NVP-containing treatment regimen between November 1994 and December 1998. A total of 351 (51%) patients had prior exposure to nucleoside reverse transcriptase inhibitors (NRTIs).

MAIN OUTCOME MEASURES

The main outcome measures were virologic undetectability, subsequent virologic rebound, CD4 cell count rise, development of AIDS, and treatment discontinuation. All analyses were stratified for year of initiation of the PI-or NVP-containing regimen.

RESULTS

Overall, 63% of patients attained an undetectable viral load (VL) within 6 months of starting their PI or NVP regimen. The adjusted relative hazard (95% confidence interval [CI]) for an undetectable VL relative to SQV HG was (in rank order): 2.77 (CI: 1.84-4.17) for NFV, 2.54 (CI: 1.81-3.57) for IDV, 2.43 (CI: 1.52-3.87) for RTV, 2.08 (CI: 1.28-3.37) for RTV/SQV HG, and 1.96 (CI: 1.35-2.85) for NVP. Forty-nine percent of patients experienced VL rebound within 12 months of initial attainment of undetectability, but relative to SQV HG, this did not differ significantly across the different PI and NVP regimens. The CD4 cell count response and rate of AIDS events were also similar across the different regimens. No independent predictors of VL undetectability were identified, but prior NRTI exposure was associated with VL rebound, and a lower baseline VL and CD4 cell count were associated with a reduced CD4 count response. The frequency (95% CI) of treatment discontinuation differed across the regimens; at 6 months, it was lowest for NFV (18% [CI: 13%-24%]), IDV (25% [CI: 22%-29%]), and NVP (28% [CI: 22%-34%]) and highest for RTV (41% [CI: 31%-52%]) and SQV HG (52% [CI: 48%-57%]).

CONCLUSIONS

Although PI- and NVP-containing regimens were similar in their CD4 cell count response and rates of subsequent VL rebound, differences were observed in time to VL undetectability and discontinuation rates relative to SQV HG. SQV HG was consistently inferior to the other PIs and NVP. The use of NFV and IDV was associated with the highest rates of undetectability, and together with NVP, the lowest rates of discontinuation.

The effect of nevirapine in combination with nelfinavir in heavily pretreated HIV-1-infected patients: a prospective, open-label, controlled, randomized study

The purpose of the current study was to determine the efficacy and safety of nevirapine combined with nelfinavir and two nucleoside reverse transcriptase inhibitors (NRTIs) in patients previously exposed to highly active antiretroviral therapy (HAART). In a prospective, open-label, randomized study, 56 HIV-infected adults who had received HAART, including saquinavir hard gel capsule, ritonavir, or indinavir, were randomly assigned to receive nevirapine in addition to nelfinavir and two NRTIs. The proportion of patients who achieved an undetectable viral load (plasma HIV-RNA <200 copies/ml) at weeks 24 and 36 was significantly higher in the nevirapine group than in the control group (55% and 52% vs. 22% and 22%; p =.015 and p =.047). No differences in CD4 cell count or clinical outcome were observed. In the nevirapine group, 17% of patients discontinued treatment because of rashes. We conclude that the addition of nevirapine, when switching from one protease inhibitor-containing regimen to one containing nelfinavir, has a substantial effect on viral suppression.

Timing of antiretroviral therapy. Use of Markov modeling and decision analysis to evaluate the long-term implications of therapy

BACKGROUND

The timing of initiation of antiretroviral therapy is controversial. Current guidelines are heavily based on the principle of 'hit early, hit hard', although the long-term implications of this approach are unknown.

METHODS

Using Markov modeling and decision analysis we modeled the virologic outcomes over 10 years in a hypothetical population of 10 000 HIV-infected patients in which therapy (with the possibility of three sequential regimens before the development of multidrug-resistant virus) is started immediately versus starting progressively at rates of 5, 10, 15, 20 or 30% of the original population each year. The model used inputs from available clinical trial data: virologic success rate and durability of the response of the first and subsequent regimens. We performed one-way and two-way sensitivity analysis to evaluate changes in the input variables.

RESULTS

If therapy is started immediately in all patients, by 10 years 57% would be undetectable, but 38% would have detectable multidrug-resistant virus. In contrast, the population as a whole would have had better virologic outcomes if one waited before starting treatment at any progression rate; for example, initiating therapy in 10% of the subjects per year results in 64% of patients being undetectable and 24% with multidrug-resistant virus. Two-way sensitivity analysis demonstrates that immediate initiation should be at least 15 to 20% better than delayed antiretroviral therapy to justify immediate initiation of therapy over a wide range of success rates of the delayed start.

CONCLUSION

Our analysis, utilizing optimistic outcomes based on short-term clinical trials, provides a theoretical basis for questioning the current aggressive early use of therapy and should help prompt studies that look at when and how to start antiretroviral therapy.

Measuring the Effectiveness of Antiretroviral Agents

Considerable progress has been made recently in developing effective antiretroviral combination therapy that can suppress viral replication and delay disease progression in individuals infected with HIV. A range of up to 15 approved antiretroviral agents is now available, which target two different viral enzymes, while several agents are in clinical development. The rapid development and approval of antiretroviral agents, driven by the urgency of clinical need as well as the complexity of possible combinations, has precluded the extensive comparative clinical testing of regimens, which is necessary to establish the relative efficacy of various different agents. The lack of an appropriate animal model for HIV disease also increases reliance on in vitro measures. Several different in vitro and in vivo parameters have been defined in an attempt to quantify the effectiveness of antiretroviral agents, most importantly the 50% inhibitory and effective concentrations (IC50 and EC50). However, the clinical relevance of these measures is uncertain. Additionally, considerable variation exists in the usage of the terms ‘IC50’ and ‘EC50’ in recent publications in the literature. These issues pose interpretation problems to clinicians seeking information on the relative clinical efficacy of the agents. In this brief review, we attempt to clarify the different measures available and their potential utility for clinical decision-making, focusing particularly on the example of HIV protease inhibitors. There are many different quantifiable parameters that give information regarding the effectiveness of an antiviral drug. These include: inhibition of the viral target enzyme (inhibition constant, Ki); selectivity for viral versus host enzymes; inhibition of viral replication in cell culture (IC50); ratio of efficacy to cytotoxicity in vitro (therapeutic index); inhibition of viral replication or symptoms in an appropriate animal model of the disease (EC50); and the effect on surrogate markers, such as viral load or CD4 cell count, after administration to humans ( in vivo EC50). Each of these different parameters gives valid information about the properties of an antiretroviral agent, which can help to build up a picture of its potential clinical utility relative to other drugs. However, to gain meaningful results, it is important to apply this information intelligently, understanding the limitations of each parameter.

Low body weight and type of protease inhibitor predict discontinuation and treatment-limiting adverse drug reactions among HIV-infected patients starting a protease inhibitor regimen: consistent results from a randomized trial and an observational cohort

OBJECTIVES

To assess predictors for discontinuation and treatment-limiting adverse drug reactions (TLADR) among patients starting their first protease inhibitor (PI).

METHODS

Data on patients starting a PI regimen (indinavir, ritonavir, ritonavir/saquinavir and saquinavir hard gel) in a randomized trial (RAS, n = 318) and an observational cohort (OBC, n = 505) were used to document reasons for discontinuation and TLADR. Risk factors for discontinuation of the initial PI/developing TLADR were assessed in Cox models.

RESULTS

A total of 43 (RAS) and 48% (OBC) discontinued the initial PI therapy within less than 2 years. In both populations TLADR were the most common reason for discontinuation. The incidence of TLADR in RAS was: 8.5 (indinavir), 66.0 (ritonavir), 15.6 (saquinavir hard gel) per 100 person-years of follow-up (P < 0.001). Body weight and type of PI initiated were independent risk factors for treatment discontinuation and TLADR in both groups. In OBC, the risk of developing TLADR increased by 12% per 5 kg lower body weight when starting the PI regimen [the relative hazard (RH) was 1.12 (95% confidence interval: 1.05-1.19) per 5 kg lighter], and starting ritonavir was associated with a three- to sixfold higher risk of TLADR relative to other PI regimens. Very similar results were documented in RAS [RH for body weight was 1.18 (1.07-1.29)].

CONCLUSIONS

Nearly half of the patients stopped treatment with the initial PI, most commonly as a result of adverse drug reactions. Low body weight and initiation of ritonavir relative to other PIs were associated with an increased risk of TLADRs. Very consistent results were found in a randomized trial and an observational cohort.

Combined therapy with saquinavir, ritonavir and stavudine in moderately to severely immunosuppressed HIV-infected protease inhibitor-naive patients

OBJECTIVE

To assess the short-term and long-term effect of a combination of saquinavir, ritonavir and stavudine in moderately to severely immunosuppressed protease inhibitor-naive patients.

DESIGN

Prospective open-label multicentre study.

PATIENTS AND METHODS

A total of 64 protease inhibitor-naive and stavudine-naive HIV-infected patients with a CD4 count of < 250 cells/microL and > 10 000 HIV-1 RNA copies/mL received saquinavir hard-gelatin capsules, ritonavir and stavudine. Full (drop in viraemia of > 2 log10 and/or < 500 copies/mL) and partial responders (drop to between 500 and 5000 viraemia copies/mL) at week 9 (end of phase I) entered the second phase (additional 12-month period).

RESULTS

Fifty-six patients completed phase I, 45 (70%) full responders and nine (14%) partial responders by intent-to-treat analysis. Thirty-nine patients completed phase II, 33 (52%) full responders and two (3%) partial responders. Six patients had < 50 HIV-1 RNA copies/mL at week 9, and 20 (31%) patients at month 12 of phase II. Mean CD4 cell counts increased significantly in the 56 patients from 89 to 184 cells/microL after 9 weeks and from 100 to 292 cells/microL in the 39 patients treated for another 12 months. Higher baseline viraemia and lower baseline CD4 cell counts were not associated with an unfavourable virological response at week 9 and month 12 of phase II. HIV DNA in peripheral blood monocytes decreased substantially (- 1.5 log10) but was detectable in all except one patient at the end of phase II.

CONCLUSION

In protease- and stavudine-naive HIV-infected patients with moderate to severe immunosuppression, saquinavir in combination with ritonavir and stavudine caused a substantial long-term decrease in plasma viral load in approximately half the participants and a substantial increase in CD4 cell counts.

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.

Antiretroviral therapy of HIV-1 infection: established treatment strategies and new therapeutic options

Recently, studies have shown that non-nucleoside reverse transcriptase inhibitors, such as efavirenz or nevirapine, in combination with two nucleoside analogues have an antiretroviral potency comparable to protease inhibitor containing regimens. Triple combination therapy that includes a non-nucleoside reverse transcriptase inhibitor can therefore be regarded as an effective alternative first-line treatment of HIV-1 infection.

Safety and pharmacokinetics of once-daily regimens of soft-gel capsule saquinavir plus minidose ritonavir in human immunodeficiency virus-negative adults

Human immunodeficiency virus type 1 (HIV-1) protease inhibitors have dramatically improved treatment options for HIV infection, but frequent dosing may impact adherence to highly active antiretroviral treatment regimens (HAART). Previous studies demonstrated that combined therapy with ritonavir and saquinavir allows a decrease in frequency of saquinavir dosing to twice daily. In this study, we evaluated the safety and pharmacokinetics of combining once-daily doses of the soft-gel capsule (SGC) formulation of saquinavir (saquinavir-SGC) and minidose ritonavir. Forty-four healthy HIV-negative volunteers were randomized into groups receiving once-daily doses of saquinavir-SGC (1,200 to 1,800 mg) plus ritonavir (100 to 200 mg) or a control group receiving only saquinavir-SGC (1,200 mg) three times daily. Saquinavir-SGC alone and saquinavir-SGC-ritonavir combinations were generally well tolerated, and there were no safety concerns. Addition of ritonavir (100 mg) to saquinavir-SGC (1,200 to 1,800 mg/day) increased the area under the concentration-time curve (AUC) for saquinavir severalfold, and the intersubject peak concentration in plasma and AUC variability were reduced compared to those achieved with saquinavir-SGC alone (3,600 mg/day), while trough saquinavir levels (24 h post-dose) were substantially higher than the 90% inhibitory concentration calculated from HIV-1 clinical isolates. Neither increasing the saquinavir-SGC dose to higher than 1,600 mg nor increasing ritonavir from 100 to 200 mg appeared to further enhance the AUC. These results suggest that an all once-daily HAART regimen, utilizing saquinavir-SGC plus a more tolerable low dose of ritonavir, may be feasible. Studies of once-daily saquinavir-SGC (1,600 mg) in combination with ritonavir (100 mg) in HIV-infected patients are underway.

Saquinavir soft-gel capsule: an updated review of its use in the management of HIV infection

Saquinavir is a potent and highly selective HIV protease inhibitor. Initially formulated as a hard-gel capsule (HGC), saquinavir was the first protease inhibitor available commercially for the treatment of patients with HIV infection. The limited oral bioavailability of saquinavir HGC has been improved significantly with the introduction of a soft-gel capsule (SGC) formulation. Saquinavir SGC displays greater than dose-proportional pharmacokinetics and mean area under the plasma concentration-time curve (AUC) values are 8- to 10-fold higher with saquinavir SGC 1200 mg 3 times daily than with the HGC formulation 600 mg 3 times daily, the recommended dosages of the 2 formulations. In combination with other protease inhibitors (particularly "low dose" ritonavir), the oral bioavailability of saquinavir (as either the HGC or SGC formulation) is markedly increased, allowing for reduced dosing frequency and/or dosage. The efficacy and tolerability of once- or twice-daily saquinavir SGC/"low dose" ritonavir combinations are currently being evaluated in patients with HIV infection. Data (up to 48 weeks) from noncomparative and comparative clinical trials evaluating saquinavir SGC-containing combination regimens in adult patients with HIV infection, support and strengthen the clinical efficacy profile of the drug that was demonstrated in initial trials. In antiretroviral therapy-naive and -experienced patients, saquinavir SGC combined with > or =2 nucleoside reverse transcriptase inhibitors (NRTIs), or nelfinavir, or nelfinavir plus 2 NRTIs or nonnucleoside reverse transcriptase inhibitors (NNRTIs), markedly improved immunological and virological surrogate markers (increased mean CD4+ cell counts and decreased mean plasma HIV RNA levels) of HIV infection. Saquinavir SGC demonstrated a trend to greater antiviral efficacy (measured by improvements in surrogate markers) than the HGC formulation (not statistically significant); a significantly greater proportion of patients treated with saquinavir SGC had plasma HIV RNA levels <400 copies/ml than patients receiving the HGC formulation. In the first direct comparison of 2 protease inhibitors, saquinavir SGC plus 2 NRTIs demonstrated similar antiviral efficacy to indinavir plus 2 NRTIs in patients with HIV infection (almost all of whom were antiretroviral therapy-naive); at 24 weeks, a significantly greater increase in CD4+ cell count from baseline was obtained in the saquinavir SGC group compared with the indinavir group, although this difference was not apparent at week 32. Triple therapy with saquinavir SGC plus 2 NRTIs was as effective as nelfinavir-containing triple therapy, or quadruple therapy (saquinavir SGC plus 2 NRTIs plus nelfinavir) in markedly suppressing HIV RNA levels in antiretroviral therapy-experienced or -naive patients. Saquinavir SGC is generally well tolerated. Gastrointestinal disturbances (generally nausea, diarrhoea, abdominal pain, vomiting and dyspepsia of moderate or greater intensity) are the most common adverse events associated with saquinavir SGC-containing therapy. In comparative trials, saquinavir SGC-containing therapy was as well tolerated as indinavir- and nelfinavir-containing therapy; although there were no statistical differences between treatment groups, the incidence of diarrhoea was lower in patients receiving saquinavir SGC compared with nelfinavir, saquinavir SGC plus nelfinavir (all combined with 2 NRTIs) or saquinavir SGC plus nelfinavir without additional therapy. Compared with the HGC formulation, saquinavir SGC appears to be associated with a higher overall incidence of adverse events.

CONCLUSIONS

Clinical trial data have shown that as part of triple or quadruple combination therapy, saquinavir SGC is an effective and generally well tolerated protease inhibitor in antiretroviral therapy-naive or -experienced patients with HIV infection. (ABSTRACT TRUNCATED)

A randomised, open-label comparison of three highly active antiretroviral therapy regimens including two nucleoside analogues and indinavir for previously untreated HIV-1 infection: the OzCombo1 study

BACKGROUND

Highly active antiretroviral therapy (HAART) including two nucleoside analogues and a potent protease inhibitor is standard of care initial therapy for HIV-infected adults. The best-tolerated and most potent initial HAART regimen is unknown and was investigated in this study.

METHODS

One hundred and nine HIV-infected adults with no prior antiretroviral therapy, and CD4 lymphocyte counts < 500 x 10(6) cells/l or plasma HIV RNA > 30,000 copies/ml were randomized to zidovudine-lamivudine-indinavir (ZDV-3TC-IDV), stavudine-lamivudine-indinavir (d4T-3TC-IDV) or stavudine-didanosine-indinavir (d4T-ddI-IDV) for 52 weeks. The primary endpoints were plasma HIV RNA and drug-related adverse events. Other assessments were overall safety, adherence and adverse events, CD4 lymphocyte counts, cutaneous delayed type hypersensitivity (DTH) responses and quality of life (Euroqol).

RESULTS

Only 58% patients had HIV RNA < 50 copies/ml plasma at 12 months, with no significant difference between the three regimes (P = 0.34). Drug-related adverse events sufficiently severe to warrant drug discontinuation were less common (P = 0.06) in patients receiving d4T-3TC-IDV (18%) than in those receiving ZDV-3TC-IDV (34%) or d4T-ddI-IDV (41%). The percentages of patients who remained on their assigned therapy with plasma HIV RNA < 50 copies/ml at 52 weeks were 60% with d4T-3TC-IDV, 53% with ZDV-3TC-IDV and 35% with d4T-ddI-IDV. Virological failure at 52 weeks was more likely in those whose adherence was estimated to be < 100% in the first 4 weeks of therapy (P = 0.02), but not in those who developed grade 3 or 4 drug-related adverse events. At 52 weeks, the mean CD4 lymphocyte count increase was 200 x 10(6) cells/l with only 7% of patients having counts lower than at baseline; DTH responses improved but remained clinically impaired in most patients. Quality of life improved significantly in all groups.

CONCLUSIONS

Initial HAART regimens including IDV failed to suppress plasma HIV RNA to < 50 copies/ml in > 40% patients after only 12 months of therapy although there was significant overall improvement immunologically and in quality of life. The type of dual nucleoside combination used was less important in predicting virological failure than was imperfect adherence early in therapy. Consideration should be given to modifying a HAART regimen relatively early in non-adherent patients.

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

OBJECTIVE

To evaluate the virological efficacy and safety of quadruple therapy with two nucleoside analogues and ritonavir (400 mg twice daily) plus indinavir (400 mg twice daily) combination in antiretroviral therapy-naive patients.

DESIGN AND METHODS

An open-label, uncontrolled multicentre trial. Antiretroviral therapy-naive patients (n = 90) with high median baseline HIV RNA levels of 220,000 copies/ml (range, 36,000-2,943,000 copies/ml) and median CD4 cell count of 189 x 10(6)/l (range, 4-656 x 10(6)/l) were started on a twice daily regimen of either zidovudine/lamivudine (49%), stavudine/lamivudine (38%) or stavudine/didanosine (13%) plus ritonavir 400 mg twice daily and indinavir 400 mg twice daily combination therapy. CD4 cell counts and HIV RNA were determined at weeks 0, 4, 8, 12, 16, 20, and 24. Statistical analysis was performed on treatment as well as intent-to-treat, where missing values were accounted for as failure.

RESULTS

In the intent-to-treat analysis at week 24, the proportion of patients with HIV RNA of < 500 copies/ml, and < 80 copies/ml was 86.7% and 71.1%, respectively. In the on-treatment analysis at week 24, 80.0% of patients had undetectable viral load in the ultrasensitive assay (< 80 copies/ml; n = 80). The quadruple therapy was well tolerated except for mild diarrhoea, initial nausea and increased triglyceride levels. Treatment was stopped in seven (7.7%) patients because of adverse events and three (3.3%) were lost to follow-up.

CONCLUSIONS

Our preliminary data suggest that the protease inhibitor combination ritonavir/indinavir plus double nucleoside therapy appears to be effective and safe in short-term treatment (up to 24 weeks).