Treatment response and durability of a double protease inhibitor therapy with saquinavir and ritonavir in an observational cohort of HIV-1-infected individuals

Clinical therapeutics in pregnancy

Most drugs are not tested for use during pregnancy, consequently, labeling, which may include information about fetal safety, includes nothing about dosing, efficacy, or maternal safety. Yet these are concerns of health care providers considering treatment of disease during pregnancy. Therefore, the practitioner treats the pregnant woman with the same dose recommended for use in adults (typically men) or may decide not to treat the disease at all. However, is the choice of not treating a woman during pregnancy better than dealing with the challenges which accompany treatment? This paper, which summarizes metabolic and physiologic changes induced by pregnancy, illustrates that standard adult dosing is likely to be incorrect during pregnancy.

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.

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.

Effect of Chronic Administration of Ritonavir on Function of Cytochrome P450 3A and P-Glycoprotein in Rats

Ritonavir (RTV) is well known as an inhibitor of many drugs that are metabolized by cytochrome P450 (CYP) 3A or fluxed via P-glycoprotein (Pgp), although it is also reported that RTV is a potent inducer for them. In this study, to elucidate these contradictory phenomena, functional changes of CYP3A or Pgp during chronic administration of RTV were examined in rats. After pretreatment with RTV for indicated days (day 3-day 14), rats were used in the experiments. The area under the plasma drug concentration vs. time curve (AUC(0-infinity)) after oral administration of RTV (20 mg/kg) to these rats showed an RTV-treatment period-dependent decrease, and the mean AUC(0-infinity) of RTV in Day 14 rats decreased significantly by 57% as compared to the control. The AUC(0-infinity) after intravenous (i.v.) administration of RTV to Day 3 and Day 5 rats increased significantly by 28% and 22%, respectively, while there were no significant changes in the AUC(0-infinity) in Day 7 and Day 14 rats as compared to the control. As for i.v. administration of erythromycin (EM) or midazolam (MDZ) to RTV-treated rats, the AUC(0-infinity)in Day 3 and Day 5 rats increased significantly as compared to the control, while in Day 7 rats and rifampicin-treated rats, the AUC(0-infinity) of EM decreased significantly by 82% and 42%, respectively, as compared to the control. For MDZ, there were no significant changes in the AUC(0-infinity) in Day 7 or Day 14 rats. After i.v. administration of rhodamine123 (Rho123), the excretion clearances from blood circulation to the intestinal lumen and the biliary excretion clearances in Day 14 rats increased markedly by 2.2-fold and 2.6-fold as compared to the control. It has been confirmed that RTV is not only a potent inhibitor but also a potent inducer of CYP3A, and that RTV is a potent inducer of intestinal Pgp. This property of RTV is responsible for regulating the oral bioavailability of drugs that are mediated by CYP3A and Pgp.

Directly observed antiretroviral therapy to reduce genital tract and plasma HIV-1 RNA in women with poor adherence

Six women with substance abuse and poor adherence histories received daily antiretroviral directly observed therapy (DOT). Cervicovaginal lavage (CVL) and plasma HIV-1-RNA levels were measured at baseline, 1 month, 3 months, and 6 months. All subjects had undetectable (below 2.6 log10 copies/ml) CVL HIV-1-RNA levels by 3 months and undetectable plasma HIV-1-RNA levels by 6 months. The mean CD4 cell increase was 76 cells/mm3. DOT appears effective and may reduce infectiousness in this high-risk population.

Assessing safety and efficacy of directed P-glycoprotein inhibition to improve the pharmacokinetic properties of saquinavir coadministered with ritonavir

Using a mouse model, we tested the effects of in vivo P-glycoprotein inhibition to enhance the oral uptake and penetration into pharmacological sanctuary sites of the human immunodeficiency virus protease inhibitor (HPI) saquinavir. The HPI ritonavir is frequently coadministered with saquinavir to improve saquinavir plasma levels since it strongly reduces the cytochrome P450 3A4-mediated metabolism of saquinavir. Previously, we demonstrated that ritonavir is not an efficient P-glycoprotein inhibitor in vivo, evidenced by the limited oral uptake of saquinavir and its penetration into brain and fetus. Increasing drug concentrations in these sites using more effective P-gp inhibitors might improve therapy but could also lead to toxicity. We orally coadministered ritonavir and saquinavir to mice, with or without the potent P-glycoprotein inhibitor N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918). Upon GF120918 coadministration, two of seven P-glycoprotein-deficient animals died. Using a decreased ritonavir dose, GF120918 coadministration led to a 4.4-fold increase in the saquinavir plasma area under the curve in wild-type mice, whereas no such effect was observed in P-glycoprotein-deficient mice. Despite the decreased ritonavir dose, all mice did suffer from impaired gastric emptying. Including GF120918 in a multiple (twice daily) dosing regimen, we found continued accumulation of saquinavir in brain over several days, resulting in 10-fold higher levels compared with vehicle-treated mice. Transient ritonavir-related neurotoxicity, however, was observed after the fourth and final drug dosing. Clinical attempts to efficiently inhibit P-glycoprotein function for improved HPI disposition may therefore be feasible, but they should be performed without ritonavir and monitored carefully for unexpected toxicities.

The role of observational data in monitoring trends in antiretroviral treatment and HIV disease stage: results from the Australian HIV observational database

OBJECTIVES

To illustrate how human immunodeficiency virus (HIV) observational databases may be used to monitor trends in HIV treatment and HIV disease outcomes through data reported from the Australian HIV Observational Database (AHOD).

METHODS

Time trends in the use of antiretroviral treatment, and changes in treatment strategies were calculated in patients recruited to AHOD from HIV specialist clinics including hospitals, sexual health clinics and general practices. These results were then compared to trends reported from other observational cohorts.

RESULTS

By September 2001, 1961 patients were recruited to AHOD. Since entering AHOD, 3% of patients have been diagnosed with an AIDS defining illness, and 2% of patients have died, of which, 54% were non-HIV related deaths. The proportion of patients receiving antiretroviral therapy increased from 66% between January and June 1998 and 77% between July and September 2001. The most commonly received treatment regimen was triple therapy including a protease inhibitor (PI), ranging between 36% in January and June 1998 and 31% in July to September 2001. Triple therapy including a non-nucleoside reverse transcriptase inhibitor (NNRTI) more than doubled to 32% between July and September 2001. The proportion of patients receiving either stavudine (d4T) or zidovudine (AZT) treatment regimens decreased from 92% between January and June 1998 to 76% between July and September 2001. Patients receiving ritonavir in combination with another PI increased, as did the proportion of patients interrupting therapy for more than 3 months.

CONCLUSION

These findings suggest there have been changes in the way antiretroviral treatments have been used in Australia, and are consistent with the current literature. Furthermore, these findings demonstrate the usefulness of observational cohorts as a surveillance tool monitoring trends in treatment and disease progression.

Selection of high-level resistance to human immunodeficiency virus type 1 protease inhibitors

Protease inhibitors represent some of the most potent agents available for therapeutic strategies designed to inhibit human immunodeficiency virus type 1 (HIV-1) replication. Under certain circumstances the virus develops resistance to the inhibitor, thereby negating the benefits of this therapy. We have carried out selections for high-level resistance to each of three protease inhibitors (indinavir, ritonavir, and saquinavir) in cell culture. Mutations accumulated over most of the course of the increasing selective pressure. There was significant overlap in the identity of the mutations selected with the different inhibitors, and this gave rise to high levels of cross-resistance. Virus particles from the resistant variants all showed defects in processing at the NC/p1 protease cleavage site in Gag. Selections with pairs of inhibitors yielded similar patterns of resistance mutations. A virus that could replicate at near-toxic levels of the three protease inhibitors combined was selected. The pro sequence of this virus was similar to that of the viruses that had been selected for high-level resistance to each of the drugs singly. Finally, a molecular clone carrying the eight most common resistance mutations seen in these selections was characterized. The sequence of this virus was relatively stable during selection for revertants in spite of displaying poor processing at the NC/p1 site and having significantly reduced fitness. These results reveal patterns of drug resistance that extend to near the limits of attainable selective pressure with these inhibitors and confirm the patterns of cross-resistance for these three inhibitors and the attenuation of virion protein processing and fitness that accompanies high-level resistance.

Phenotypic analysis of peripheral blood gammadelta T lymphocytes and their targeting by human immunodeficiency virus type 1 in vivo

There is increasing evidence that a wider range of lymphoid cell types other than CD4(+) T helper lymphocytes are infected with HIV-1 in vivo, including CD8 lymphocytes, natural killer cells, and reticulodendritic cells. Each potentially contributes to the reservoir of infected cells that resist antiviral treatment and to the impairment of immune responses in AIDS. By quantitative PCR for HIV proviral sequences we have now obtained evidence for substantial infection of gammadelta lymphocytes, contributing 3-45% of the proviral load in peripheral blood. A large proportion of gammadelta lymphocytes constitutively expressed the chemokine receptors CCR5 and CXCR4, with evidence for marked up-regulation of CD8 in samples from HIV-infected individuals, corresponding to an activated phenotype. That gammadelta lymphocytes might be susceptible to HIV infection was investigated using in vitro infectivity assays of recombinant HIV-expressing green fluorescent protein, followed by flow cytometry. gammadelta, CD4, and CD8 lymphocytes were each productively infected, with gammadelta lymphocytes showing the greatest susceptibility. For each cell type, blocking assays with an anti-CD4 monoclonal antibody indicated that entry was CD4-dependent.

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.

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.

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.

Baseline antiretroviral drug susceptibility influences treatment response in patients receiving saquinavir-enhancing therapy

PURPOSE

To relate baseline plasma HIV genotypic and virtual phenotypic antiretroviral drug susceptibility to subsequent virological response in patients receiving saquinavir (SQV)-enhancing therapy. Individuals were randomized to receive stavudine (d4T), SQV, and one of ritonavir, nelfinavir, or delavirdine to enhance SQV blood levels.

METHOD

The protease and reverse transcriptase baseline sequences of 31 treatment-experienced patients were analyzed by genotype and virtual phenotype and were related to viral load at weeks 12 and 24. Genotypic resistance to SQV was defined by the presence of G48V and/or L90M mutations in the protease gene. Potential cross-resistance to d4T in zidovudine (ZDV)-experienced individuals was defined by the presence of thymidine-associated mutations in the reverse transcriptase gene.

RESULTS

ZDV-associated mutations did not affect the virological response at 24 weeks. Individuals who were sensitive to SQV at baseline as determined by either genotyping or virtual phenotyping showed a greater decrease in viral load at week 24 than those resistant to SQV, irrespective of treatment arm. By genotyping, SQV-sensitive individuals had a median log decrease of 1.12 compared to 0.32 for those individuals who were SQV resistant. By virtual phenotyping, SQV-sensitive individuals had a median log decrease of 1.0 compared to a rise of 0.08 in resistant individuals.

CONCLUSION

Thymidine analogue-associated mutations at baseline did not influence the response to subsequent therapy involving d4T. Individuals who were sensitive or resistant to SQV by genotyping or virtual phenotyping responded to SQV-enhancing regimens, but the virological response was greater in those who were sensitive.

Infection of the CD45RA+ (naive) subset of peripheral CD8+ lymphocytes by human immunodeficiency virus type 1 in vivo

To investigate the mechanism and functional significance of infection of CD8+ lymphocytes by human immunodeficiency virus type 1 (HIV-1) in vivo, we determined frequencies of infection, proviral conformation, and genetic relationships between HIV-1 variants infecting naive (CD45RA+) and memory (CD45RO+) peripheral blood CD4+ and CD8+ lymphocytes. Infection of CD3+ CD8+ CD45RA+ cells was detected in 9 of 16 study subjects at frequencies ranging from 30 to 1,400 proviral copies/10(6) cells, more frequently than CD3+ CD8+ lymphocytes expressing the RO isoform of CD45 (n = 2, 70 and 260 copies /10(6) cells). In agreement with previous studies, there was no evidence for a similar preferential infection of CD4+ naive lymphocytes. Proviral sequences in both CD4+ and CD8+ lymphocyte subsets were complete, as assessed by quantitation using primers from the long terminal repeat region spanning the tRNA primer binding site. In six of the seven study subjects investigated, variants infecting CD8+ lymphocytes were partially or completely genetically distinct in the V3 region from those recovered from CD4+ lymphocytes and showed a greater degree of compartmentalization than observed between naive and memory subsets of CD4+ lymphocytes. In two study subjects, arginine substitutions at position 306, associated with use of the chemokine coreceptor CXCR4, were preferentially found in CD4 lymphocytes. These population differences may have originated through different times of infection rather than necessarily indicating a difference in their biological properties. The preferential distribution of HIV-1 in naive CD8+ lymphocytes indeed suggests that infection occurred early in T-lymphocyte ontogeny, such as during maturation in the thymus. Destruction of cells destined to become CD8+ lymphocytes may be a major factor in the decline in CD8+ lymphocyte frequencies and function on disease progression and may contribute directly to the observed immunodeficiency in AIDS.

Impact of HIV type 1 protease, reverse transcriptase, cleavage site, and p6 mutations on the virological response to quadruple therapy with saquinavir, ritonavir, and two nucleoside analogs

Genotype alterations of HIV-1 protease, reverse transcriptase, cleavage sites p7/p1 and p1/p6, as well as p6(gag) and transframe protein p6* were studied in an observational cohort of 42 individuals who received antiretroviral therapy consisting of saquinavir, ritonavir, and two nucleoside analogs. In a multivariate logistic regression analysis, the prior protease inhibitor experience (odds ratio, 6.20; 95% CI, 1.22-31.38) and the presence of primary protease mutations (odds ratio, 9.99; 95% CI, 1.05-94.72) were independently associated with virological failure. Moreover, a trend was observed in that individuals with N-terminal amino acid insertions in the proline-rich motif of the p6(gag) protein were less likely to experience virological failure (OR, 0.17; 95% CI, 0.02-1.35; p = 0.09). In contrast, the presence of secondary protease, reverse transcriptase, or cleavage site mutations was not independently associated with treatment failure. However, mutations at cleavage site p7/p1 (p = 0.01) and C-terminal p6* mutations (p = 0.02) were both associated with primary protease mutations. In conclusion, the presence of primary protease mutations was the most important predictor of the subsequent virological response. Moreover, there is some evidence that insertions in the proline-rich area of the p6(gag) protein may affect the virological response. The relationship between mutations of cleavage sites or C-terminal p6* residues and protease mutations suggests that these alterations may serve a compensatory role, increasing viral fitness.

P-glycoprotein limits oral availability, brain, and fetal penetration of saquinavir even with high doses of ritonavir

The low oral bioavailability of the HIV protease inhibitor (HPI) saquinavir is dramatically increased by coadministration of the HPI ritonavir. Because saquinavir and ritonavir are substrates and inhibitors of both the drug transporter P-glycoprotein (P-gp) and of the metabolizing enzyme CYP3A4, we wanted to sort out whether the ritonavir effect is primarily mediated by inhibition of CYP3A4 or P-gp or both. P-gp is known to limit the bioavailability, brain, testis, and fetal penetration of its substrates, so effective inhibition of P-gp by ritonavir in vivo might open up pharmacological sanctuary sites for saquinavir, with the potential of beneficial effects on therapy, but also of increased toxicity. In vitro, P-gp-mediated transport of saquinavir and ritonavir was only moderately inhibited by both HPIs compared with the potent P-gp inhibitor PSC833. When [(14)C]saquinavir was orally coadministered with a maximum tolerated dose of ritonavir to wild-type and P-gp-deficient mice, saquinavir bioavailability was dramatically increased in both strains, but P-gp still limited the oral bioavailability of saquinavir, and its penetration into brain and fetus. These data indicate that in vivo, ritonavir is a relatively poor P-gp inhibitor. The highly increased bioavailability of saquinavir because of ritonavir coadministration most likely results from reduced saquinavir metabolism. Importantly, our data indicate that it is unlikely that ritonavir coadministration will substantially affect the contribution of P-gp to pharmacological sanctuary sites such as brain, testis, and fetus. Thus, if one wanted to effectively open these sites for therapeutic purposes, more efficient P-gp inhibitors should be applied.

Economic analysis of initial HIV treatment. Efavirenz- versus indinavir-containing triple therapy

OBJECTIVE

To compare the clinical and economic outcomes associated with triple therapy containing efavirenz or indinavir and 2 nucleoside reverse transcriptase inhibitors (NRTIs; zidovudine and lamivudine) in HIV-positive patients.

DESIGN AND SETTING

An economic model based on viral load and CD4+ cell counts to predict long term outcomes such as progression to AIDS and AIDS-related death was developed and then analysed using data from a randomised clinical trial. Cost estimates from the healthcare system perspective were based on data from 6 state, all-payor databases, the AIDS Cost and Services Utilisation Study, and other literature. Analyses were carried out for time horizons between 5 and 15 years.

PATIENTS AND INTERVENTIONS

HIV-positive patients with limited exposure to NRTIs. Initial regimens consisted of efavirenz or indinavir, each combined with 2 NRTIs. A maximum of 2 switches to other regimens was permitted.

MAIN OUTCOME MEASURES AND RESULTS

The efavirenz-containing triple therapy regimen was predicted to prolong survival at a savings of up to 10,923 US dollars (1998 values) relative to initial therapy with the indinavir-containing regimen. Patients who receive efavirenz are expected to have 11% greater survival at 5 years and fewer treatment failures (28 vs 52%, at 2 years). Overall, the economic and health benefits predicted for the efavirenz-containing regimen were robust to reasonable variation in key parameters.

CONCLUSIONS

The superior clinical trial outcomes for efavirenz-containing regimens should translate into substantial economic and health benefits.

Immunological and virological responses in HIV-1-infected adults at early stage of established infection treated with highly active antiretroviral therapy

OBJECTIVE

To evaluate the immunological and virological responses to highly active antiretroviral therapy (HAART) in blood and lymphoid compartments of HIV-1-infected patients at an early stage of infection.

DESIGN

An open-label, observational, non-randomized, prospective trial of outpatients attending the Centre of Clinical Investigation in Infectious Diseases, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Switzerland.

SUBJECTS

Forty-one antiretroviral-naive HIV-1-infected adults with 400 CD4 T cells/microl or greater and 5000 plasma HIV-1-RNA copies/ml or greater were enrolled, and 32 finished the study. Forty-nine HIV-negative individuals were included as controls. All subjects gave written informed consent.

INTERVENTIONS

All patients received abacavir 300 mg by mouth every 12 h and amprenavir 1200 mg by mouth every 12 h for 72 weeks.

MAIN OUTCOME MEASURES

The extent of immune reconstitution in blood and lymph nodes after 72 weeks of HAART was evaluated, and compared with immunological measures of 49 HIV-negative subjects.

RESULTS

Virus replication was effectively suppressed (-3.5 log10 at week 72). Substantial increments of CD4 T cell count in blood and percentage in lymph nodes were observed over time, and these measures were comparable to HIV-negative subjects by week 24 in blood and by week 48 in lymph nodes. The increase was equally distributed between naive and memory CD4 T cells. Recovery of HIV-specific CD4 responses occurred in 40% of patients.

CONCLUSION

The initiation of HAART at an early stage of established HIV infection induces systemic quantitative normalization of CD4 T cells, a partial recovery of HIV-specific CD4 cell responses, and effective and durable suppression of virus replication.

The cumulative occurrence of resistance mutations in the HIV-1 protease gene is associated with failure of salvage therapy with ritonavir and saquinavir in protease inhibitor-experienced patients

Salvage therapy with ritonavir (RTV) and saquinavir (SQV) failed to achieve virological and immunological improvement in 24 HIV-infected patients who discontinued triple therapy with RTV or indinavir (IDV) because of failure or intolerance to treatment. Changes in the HIV-1 protease gene sequence were analyzed prospectively in 14 patients. No primary protease mutation was found prior to the use of protease inhibitors. After 7 months of treatment with IDV or RTV, primary resistance mutations at codons pol 46 and/or pol 82 were observed in 11 of 13 patients. After 16 weeks on RTV-SQV, novel primary mutations related to SQV emerged in 7 of 13 patients, together with an increase in the number of secondary resistance mutations. Our observations indicate that the cumulative occurrence of resistance mutations in the protease gene was associated with failure of antiretroviral therapy. The presence of mutations to a first protease inhibitor may represent a risk factor for the failure of a subsequent treatment with a second line protease inhibitor.

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.

Two decades of HIV infection in a cohort of haemophilic individuals: clinical outcomes and response to highly active antiretroviral therapy

OBJECTIVES

Many haemophilic individuals infected with HIV died before receiving antiretroviral therapy (ART). Most who remain alive are chronically infected with hepatitis C virus (HCV), which has implications for their prognosis and choice of ART. The clinical status of a cohort of HIV-positive haemophilic men is reported together with their response to highly active antiretroviral therapy (HAART).

DESIGN

Longitudinal cohort study.

SETTING

A comprehensive care haemophilia centre.

PATIENTS

A group of 111 haemophilic men who seroconverted to HIV in the period 1979 to 1985.

RESULTS

The cohort has been followed since 1979. By 30 April 1999, 57 of the 111 men had developed AIDS and 65 had died: Kaplan-Meier rates of 57.0% [95% confidence interval (CI) 46.9-67.0) and 65.1% (95% CI 52.7-77.4) by 19.5 years, respectively. AIDS rates have declined since 1997 but death rates have remained high, largely owing to deaths from non-HIV-related causes. Thirty-five patients remain alive and under follow-up at the clinic. The 28 men who had received ART had lower CD4 cell counts than the seven patients who had not received ART, but the two groups were otherwise similar. In total, 21 patients are known to have started HAART while under care at the centre. By 10-12 months after starting HAART, viral loads dropped by 2.06 log10 copies/ml and CD4 cell counts increased by 60 x 10(6) cells/l. In 10 out of 18 patients with viral loads initially > 400 copies/ml, a viral load below this level was attained; four had changed therapy at the time.

CONCLUSIONS

While the decision to initiate HAART in haemophilic men should be made carefully because of the possible adverse events, our results suggest that a good response rate was achieved in this group of men.

Experience with Nevirapine in Previously Treated HIV-1-Infected Individuals

Objective

To assess the tolerability, virological, immunological and clinical effects of nevirapine in the setting of a compassionate use programme in pretreated HIV-infected individuals.

Design

Retrospective observational cohort-study in 13 HIV-outpatient clinics in The Netherlands.

Methods

Main outcome measures: plasma HIV-1 RNA levels; CD4 cell counts; incidence of new AIDS-defining diseases; multivariate analysis of predictors for virological success; incidence of skin rashes.

Results

187 HIV-infected individuals treated with nevirapine in the Nevirapine Named Patient Programme in The Netherlands were included. After 48 weeks, 38% of patients had an HIV-1 RNA level below 1000 copies/ml. In multivariate regression analysis, prior treatment with three or less nucleoside analogue reverse transcriptase inhibitors, and a higher baseline CD4 cell count was predictive of virological success. The median CD4 cell count remained stable over the 48 weeks. Eleven patients experienced a new AIDS-defining event. The total incidence of rash (including rash not leading to discontinuation of nevirapine) was 13.9 and 6.4% of the patients discontinued nevirapine because of rash. None of the 28 patients with undetectable HIV-1 RNA levels at baseline developed a rash.

Conclusions

We conclude that nevirapine when used as part of salvage therapy, is safe and most likely to give sustained suppression of HIV-1 in patients that have been less extensively pretreated. CD4 cell counts remained stable despite the low rate of virological success, this also occurred in patients not concurrently using protease inhibitors (PIs). The incidence of nevirapine-related rash in PI-pretreated patients and especially in patients with undetectable HIV-1 RNA levels at the start of nevirapine treatment, is considerably lower than previously reported for antiretroviral-naive patients.

Comparison of human immunodeficiency virus type 1 Pr55(Gag) and Pr160(Gag-pol) processing intermediates that accumulate in primary and transformed cells treated with peptidic and nonpeptidic protease inhibitors

Human immunodeficiency virus type 1 (HIV-1) produces two polyproteins, Pr55(Gag) and Pr160(Gag-Pol), that are cleaved into mature functional subunits by the virally encoded protease. Drugs that inhibit this protease are an important part of anti-HIV therapy. We studied the ordered accumulation of Gag and Gag-Pol processing intermediates by variably blocking the protease with HIV-1 protease inhibitors (PIs). Variable protease inhibition caused accumulation of a complex pattern of processing intermediates, which was the same after incubating HIV-1-infected cells with increasing concentrations of either one of the peptidomimetic inhibitors indinavir, saquinavir (SQV), ritonavir (RTV), nelfinavir, and SC-52151 or one of the nonpeptidomimetic inhibitors DMP450, DMP323, PNU-140135, and PNU-109112 for 3 days. The patterns of Gag and Gag-Pol processing intermediate accumulation were nearly identical when the following were compared: cell- versus virion-associated proteins, HIV-1-infected transformed cell lines versus primary human peripheral blood mononuclear cells (PBMCs) and HIV-1(MN) versus HIV-1(IIIB) virus strains. RTV was a more potent inhibitor of p24 production in PBMCs than SQV by approximately 7-fold, whereas SQV was a more potent inhibitor in transformed cells than RTV by approximately 30-fold. Although the antiretroviral potency of HIV-1 PIs may change as a function of cell type, the polyprotein intermediates that accumulate with increasing drug concentrations are the same. These results support sequential processing of Gag and Gag-Pol polyproteins by the HIV-1 protease and may have important implications for understanding common cross-resistance pathways.

Phase III study of granulocyte-macrophage colony-stimulating factor in advanced HIV disease: effect on infections, CD4 cell counts and HIV suppression. Leukine/HIV Study Group

OBJECTIVE

To evaluate the effect of adjuvant granulocyte-macrophage colony-stimulating factor (GM-CSF) (sargramostim, yeast-derived recombinant human GM-CSF) on incidence and time to opportunistic infection or death, plasma HIV-RNA, and CD4 cell count in patients with advanced HIV disease.

METHODS

This Phase III randomized, double-blind, placebo-controlled trial enrolled subjects with CD4 cell counts < or = 50 x 10(6)/l or < or = 100 x 10(6)/l with a prior AIDS-defining illness on stable antiretroviral therapy. Subjects were stratified by baseline HIV-RNA level (> or = or < 30,000 copies/ml) and randomized to receive subcutaneous injections of GM-CSF 250 microg or placebo three times per week for 24 weeks. Subjects were permitted to continue on blinded drug for up to 20 months. Subjects were evaluated for infections, plasma HIV-RNA, lymphocyte counts, changes in antiretroviral therapy, toxicity, and survival.

RESULTS

Three-hundred and nine subjects received at least one dose of study drug, 70% completed 24 weeks of therapy. Groups were well matched at baseline. Significant increases in CD4 cell and neutrophil counts were observed at 1, 3, and 6 months in the GM-CSF group. GM-CSF significantly reduced the incidence of overall infections (78% placebo versus 67% GM-CSF; P = 0.03) and delayed time to first infection (56 days placebo versus 97 days GM-CSF; P = 0.04). No statistical difference in cumulative opportunistic infections was observed between groups; however, among subjects without an opportunistic infection prior to study, the GM-CSF group demonstrated a trend towards fewer subjects with an opportunistic infection on study (26% placebo versus 8% GM-CSF; P = 0.08). Change in HIV-RNA was not significantly different between groups, but significantly fewer GM-CSF subjects with baseline viral load < 30,000 copies/ml had changes in antiretroviral therapy for increased viral load (42% placebo versus 21% GM-CSF; P = 0.01). In patients with HIV-RNA levels below the limit of detection at baseline, more GM-CSF patients maintained an undetectable viral load at 24 weeks (54% placebo versus 83% GM-CSF; P = 0.02). GM-CSF was well tolerated.

CONCLUSIONS

GM-CSF significantly increased CD4 cell count and decreased virological breakthrough and overall infection rate in subjects with advanced HIV disease.

Toxicity and drug exposure in a quadruple drug regimen in HIV-1 infected patients participating in the ADAM study

OBJECTIVE

To study the relationship between toxicity and the exposure to nelfinavir and saquinavir as part of a quadruple drug regimen.

DESIGN

The ADAM study is a randomized study to investigate the feasibility of induction-maintenance therapy in HIV-1 infection.

METHODS

HIV-1-infected patients with no prior use of antiretroviral treatment started induction therapy consisting of stavudine + lamivudine + nelfinavir + saquinavir for a period of 26 weeks. Data regarding toxicity of the quadruple regimen and exposure to the protease inhibitors were collected.

RESULTS

Seven of the 65 patients enrolled had to switch therapy for reasons of toxicity within the first 26 weeks. Diarrhoea was frequently reported (49 of 65, one discontinuation), but could be relieved by using antidiarrhoeal agents. Laboratory monitoring revealed elevated liver enzymes (leading to four discontinuations) and mild to moderate elevations of triglycerides and cholesterol (nine and 23 of 65, respectively). The exposure to saquinavir and nelfinavir was lower than expected. Abdominal pain was associated with a higher exposure to nelfinavir or saquinavir. The association of nausea and abdominal distension with drug exposure appeared to vary over time.

CONCLUSIONS

The quadruple drug regimen was quite well tolerated. Diarrhoea was frequently reported but could be relieved by the use of antidiarrhoeal agents. In comparison with other protease inhibitor combinations, lipid abnormalities in plasma were infrequent and mild. With the exception of diarrhoea, all gastrointestinal complaints observed were found to be associated with the level of exposure to nelfinavir or saquinavir. The exposure to the protease inhibitors was relatively low, although the virologic efficacy of the regimen used was satisfactory.

Comparison of ritonavir plus saquinavir- and nelfinavir plus saquinavir-containing regimens as salvage therapy in children with human immunodeficiency type 1 infection

BACKGROUND

In this retrospective study we compared the antiretroviral effect of regimens consisting of simultaneous administration of two protease inhibitors (PI) with at least one nucleoside reverse transcriptase inhibitor on plasma viral load (VL) and CD4 cell count in HIV-infected children intensively pretreated with nucleoside reverse transcriptase inhibitors and PIs.

METHODS

Eleven HIV-infected children were changed to antiretroviral combination regimens including two PIs and followed for a median time of 24 weeks. Group A comprised six patients who were given ritonavir + saquinavir (SQV) and Group B consists of five patients who were changed to nelfinavir + SQV. Patients were treated with these combinations with 2 PIs because of treatment failure (increasing viral load) of prior PI therapy or clinical signs of disease progression.

OUTCOME MEASURES

Serial determinations of plasma viral load (Amplicor, Roche) and CD4 cells were performed every 4 to 8 weeks. The detection limit of the Amplicor-reverse transcriptase-PCR assay was 50 copies/ml (1.7 log10).

RESULTS

In Group A the median VL reduction was 1.1 log10 after 3 months and 1.4 log10 after 6 months. In Group B median VL decreased 0.1 and 0.2 log10 after 3 and 6 months. In both groups during the study period none of the patients reached undetectable VL. The relative changes of CD4 cells above baseline in Group A showed a median increase of 7% after 3 months and 23% after 6 months. In Group B after 3 months CD4 cells did not increase, and after 6 months the median relative increase was only 7%. Both combination therapies were well tolerated, not necessitating any drug interruption during study period.

CONCLUSIONS

In children with intensive prior antiretroviral treatment, a salvage therapy including two PIs demonstrated antiretroviral efficacy in some patients. In this study the reduction of the VL as well as the increase of CD4 cells was more pronounced with ritonavir + SQV than with nelfinavir + SQV. With both combinations complete suppression of HIV replication was not achieved. Therefore the long term effect of these combinations may be limited by the emergence of resistant HIV strains.

Current laboratory assays and in vitro intracellular Th1 and Th2 cytokine synthesis in monitoring antiretroviral therapy of pediatric HIV infection

In 42 HIV-infected children, 8-10 years old, belonging to the category A state of infection, combined antiretroviral therapy (cART) was applied, consisting of AZT, ddC and Saquinavir. At 6 and 12 weeks following the start of cART, the efficacy of treatment was assessed, both by means of current parameters (blood CD4+ cell levels, virus load) and by measuring the intracellular synthesis of some Th1 (interleukin (IL)-2, interferon-gamma) and Th2 (IL-4, IL-10) cytokines, in CD4+ lymphocytes, respectively. Before cART, low values of blood CD4+ cell counts and a mean of about 8000 virus RNA copies ml(-1) of serum were detected, and in addition decreased levels of production of both intracellular Th1 cytokines, associated with increased levels of one of the Th2 cytokines (IL-10), but not of the other (IL-4), were noticed. After cART, earlier improvement of intracellular IL-2, interferon-gamma and IL-10 synthesis in CD4+ cells occurred compared to CD4+ counts and virus load. The usefulness of scoring the rates at which CD4+ lymphocytes are able to synthesize intracellular Th1 or Th2 cytokines, as an additional immune parameter during combined antiretroviral therapy monitoring in pediatric AIDS, is discussed.

Saquinavir hard gel suppresses viral load insufficiently in HIV-infected patients naive to anti-retroviral therapy: a retrospective cohort study

Protease inhibitors are important components in anti-retroviral regimens. In this retrospective study 29 HIV-infected patients treated with a regimen of zidovudine, lamivudine and saquinavir hard gel in 1 centre in Denmark were compared with 58 patients treated with zidovudine, lamivudine and ritonavir or indinavir followed at 5 other centres in Scandinavia. All patients were naive to anti-retroviral therapy prior to institution of the actual anti-retroviral regimen and were followed for a median of 1.3 and 1.4 y respectively. The 2 groups did not differ significantly with respect to age, gender, route of infection, ethnic background, viral load, CD4 count, AIDS at baseline or frequency of clinical controls. Six and 12 months after initiating anti-retroviral therapy, 31% and 34% of the patients on the saquinavir regimen obtained HIV-RNA < or = 500 compared with 76% and 73% in the control group (p < 0.001). In contrast to viral load, the increase in CD4 count did not differ significantly between the 2 groups. In conclusion, we found that with respect to suppression of viral load a regimen of saquinavir, zidovudine and lamivudine seemed to be inferior to a regimen of zidovudine, lamivudine and ritonavir or indinavir.

Baseline HIV drug resistance profile predicts response to ritonavir-saquinavir protease inhibitor therapy in a community setting

OBJECTIVE

To determine whether baseline drug resistance assays could help to predict treatment failure with the protease inhibitor combination ritonavir-saquinavir.

METHODS

Baseline HIV-1 drug resistance was determined for 76 consecutive patients who started treatment with the dual protease inhibitor combination ritonavir-saquinavir between September 1996 and June 1997 either alone or in combination with other antiviral agents. Resistance to 10 different antiviral agents was assessed by both phenotype (Virco Antivirogram) and genotype (Vircogen).

RESULTS

Resistance inferred from viral genotype was similar to measured phenotypic resistance for both ritonavir and saquinavir (P<0.01). Baseline drug resistance phenotype was predictive of poor virological response to this dual protease inhibitor combination, despite the confounding effects of other antivirals. Patients were at least four times less likely to achieve a 0.5 log10 decrease in plasma HIV RNA viral load if their viral isolates were resistant to ritonavir or saquinavir. Patients classified as resistant to either drug using either method had median decreases in plasma viral load of 0.05 log10 HIV RNA copies/ml or less, compared to >0.8 log10 for those with sensitive virus. Patients resistant to both drugs never achieved plasma viral loads <100000 copies/ml. As little as fourfold increases in baseline resistance appeared to be sufficient to compromise even dual protease inhibitor therapy.

CONCLUSION

Baseline resistance to ritonavir or saquinavir or both was associated with a poor antiviral response. Our data suggest that the measurement of drug resistance may assist in optimizing antiretroviral therapy in the clinic.

High-dose saquinavir plus ritonavir: long-term efficacy in HIV-positive protease inhibitor-experienced patients and predictors of virologic response

The year-long antiviral efficacy of a high-dose salvage regimen consisting of saquinavir (800 mg twice daily) plus ritonavir (400 mg twice daily) was evaluated in 58 HIV-positive patients who had seen no improvement under first-line protease inhibitor-containing regimens, nor in baseline predictors of virologic response. The efficacy of therapy was determined by CD4+/CD8+ and HIV-1 RNA values. The primary endpoint of our study was the percentage of patients with HIV-1 RNA levels <200 copies/ml (virologic success) at 6 and 12 months of of follow-up. Secondary endpoints were log10 reduction in HIV-1 RNA levels and CD4+ increases through follow-up. Surrogate markers related with a lower HIV-1 RNA area under the curve were identified at baseline. Kaplan-Meier analysis and Cox proportional hazards models were applied to identify baseline predictors of achieving viral suppression at <200 copies/ml. All analyses were intention to treat-last observation carried forward. Patients achieved a median HIV-1 RNA level reduction of >0.5 log through 1 year (-0.59 log10 at 12 months), as well as CD4+ counts increased significantly (89 cells/mm3 at 12 months). Overall, 53% of patients were likely to achieve HIV-1 RNA levels <200 copies/ml at 6 months. Seventy-six percent of patients who started therapy at HIV-1 RNA levels <5000 copies/ml but only 42% with baseline viral load of 5000 to 30,000 copies/ml and 18.7% with baseline viral load >30,000 copies/ml were likely to achieve viral suppression at 6 months (p < .001, log-rank test). Patients with baseline HIV-1 RNA levels between 5000 and 30,000 copies/ml (relative hazard [RH], 0.39; 95% confidence interval [CI], 0.01 to 0.98; p = .0396) and patients with baseline HIV-1 RNA levels >30,000 copies/ml (RH, 0.20; 95% CI, 0.07-0.61; p = .0040) were less likely to reach undetectable HIV-1 RNA levels than those with baseline HIV-1 RNA levels <5000 copies/ml. Salvage highly active antiretroviral therapy (HAART) strategies including saquinavir (SQV) at high doses plus ritonavir (RTV) exert a significant long-term efficacy in more than half of PI-experienced patients without significant additional toxicity. This therapeutic efficacy is strongly implemented by a switch at the lower HIV-1 RNA levels.

Salvage therapy with regimens containing ritonavir and saquinavir in extensively pretreated HIV-infected patients

OBJECTIVE

To evaluate the efficacy and toxicity of salvage regimens containing ritonavir and saquinavir in patients failing highly active antiretroviral therapy (HAART), and to correlate outcome with plasma concentrations of protease inhibitors.

DESIGN

Prospective, non-randomized interventional study.

SUBJECTS AND METHODS

Thirty extensively pretreated HIV-infected patients with virological failure under HAART were treated with ritonavir (400 mg twice daily) and saquinavir (600 mg twice daily) and at least one reverse transcriptase inhibitor. HIV-RNA, CD4 cell counts and plasma concentrations of protease inhibitors were determined, and patients were monitored for toxicity at monthly intervals.

RESULTS

Six patients showed complete virological success (HIV-RNA <200 copies/ml at week 12) which was sustained for a median follow-up of 6.3 months. Partial virological response (decrease of HIV-RNA of >1 log10 at week 12) was achieved by a further three patients. Patients with a virological response had significantly higher CD4 cell increases than patients without virological response (mean increase at week 12: 66x10(6) cells/l versus 6x10(6) cells/l; P = 0.01). No clinical events were observed during 6 months of follow-up. Neither the use of a non-nucleoside reverse transcriptase inhibitor (NNRTI) nor the number of newly introduced drugs influenced the virological response. Plasma concentrations of protease inhibitors did not statistically differ between patients with and without success. Toxicity included gastrointestinal disturbances, lipid abnormalities and liver dysfunction.

CONCLUSIONS

In extensively pretreated patients, salvage regimens containing ritonavir and saquinavir had only limited and short-term anti-HIV activity and were associated with substantial toxicity. Plasma concentrations of saquinavir were not predictive for virological response.

Efficacy of a five-drug combination including ritonavir, saquinavir and efavirenz in patients who failed on a conventional triple-drug regimen: phenotypic resistance to protease inhibitors predicts outcome of therapy

OBJECTIVE

to assess the safety and efficacy of a combination of ritonavir, efavirenz and two recycled nucleosides in patients who failed on a conventional triple-drug regimen including indinavir or ritonavir.

METHODS

An open label study of ritonavir (100 mg twice daily), saquinavir (1000 mg twice daily), efavirenz (600 mg per day) and nucleoside analogues in 32 saquinavir- and efavirenz-naive protease inhibitor-experienced patients. Patients were included on the basis of plasma levels of HIV RNA above 5000 copies/ml while on conventional antiretroviral therapy. Phenotypic resistance and genotypic resistance mutations to saquinavir were assessed at baseline. Peak and trough plasma levels of saquinavir were monitored throughout the study.

RESULTS

Median CD4 cell counts and median plasma HIV RNA at baseline were 258 x 10(6)/l and 4.31 log10 copies/ml, respectively. The plasma viral load decreased by a median of 1.20 log10 copies/ml and the CD4 cell count increased by a median 60 x 10(6) cells/l at week 24 of therapy. Seventy-one per cent of the patients achieved a plasma viral load < 500 copies/ml and 45% achieved a viral load < 50 copies/ml. Patients exhibiting phenotypic resistance to saquinavir at baseline experienced a median decrease in HIV RNA of 0.91 log10 copies/ml at week 24 of therapy, as compared with a decrease of 1.52 log10 copies/ml in those exhibiting sensitive viral strains (P = 0.03). Genotypic resistance to saquinavir was not predictive of virologic failure.

CONCLUSION

Our results indicate that the combination of ritonavir, saquinavir and efavirenz is safe and effective at 24 weeks in over two-thirds of patients who previously failed on highly active antiretroviral therapy, and that the determination of phenotypic resistance may be of greater value than the detection of resistance mutations to predict the outcome of salvage therapy in this setting.

Phenotypic analysis of CD8+ T lymphocytes in a cohort of HIV type 1-infected patients treated with saquinavir, ritonavir, and two nucleoside analogs for 1 year, and association with plasma HIV type 1 RNA

The phenotype of circulating CD8+ T lymphocytes and its association with plasma HIV-1 RNA were analyzed in 34 HIV-1-infected subjects, who were treated with saquinavir, ritonavir, and two nucleoside analogs (HAART) for 1 year. Four-color flow cytometry was applied to measure the expression of cell surface antigens CD38, HLA-DR, CD45RA, CD28, and CD62L on CD8+ T lymphocytes. The results were compared with data on 35 HIV-1-seronegative subjects, 18 untreated asymptomatic HIV-1-seropositive individuals, and 24 HIV-1-infected subjects receiving reverse transcriptase inhibitors (RTIs). Subjects receiving HAART showed a significantly elevated number and percentage of CD38- and HLA-DR-positive and CD28-negative CD8+ T lymphocytes as well as a lower percentage of naive (CD45RA+62L+) CD8+ T lymphocytes compared with HIV-1-uninfected controls. Even subjects with undetectable plasma HIV-1 RNA showed a persistent elevation of activated CD8+ T lymphocytes. However, fewer activated CD8+ T lymphocytes were observed in subjects receiving HAART than in untreated individuals and subjects administered RTIs. In individuals receiving RTIs, CD8+ cell activation was not significantly reduced compared with untreated subjects. Of all evaluated activation markers, the percentage of CD8+ T lymphocytes expressing CD38 and the combination of CD38 and HLA-DR showed the best correlation with plasma HIV-1 RNA. The persistence of CD8+ T lymphocyte activation in subjects receiving HAART strongly suggests ongoing viral activity, even in subjects with undetectable plasma HIV-1 RNA. A complete normalization of immunologic changes of CD8+ T lymphocytes would therefore require a more potent drug regimen or a longer duration of therapy.

Highly active antiretroviral therapy (HAART) for the treatment of infection with human immunodeficiency virus type 1

Highly active antiretroviral therapy (HAART) refers to a broad category of treatment regimens usually comprised of three or more antiretroviral drugs that, in previously untreated HIV-1-infected patients, are expected to reduce plasma virus levels below the limits of detection. Most HAART regimens include drugs from at least two of the three classes of antiretroviral therapy (nucleoside analog reverse transcriptase (RT) inhibitors, non-nucleoside analog RT inhibitors, and protease inhibitors). In deciding when to initiate antiretroviral therapy, physicians and their patients must balance the virological and immunological benefits of early treatment with the costs of drug therapy, the risk of drug side effects, and the risk of drug resistance if adherence is suboptimal. In previously untreated patients, HIV-1 replication can be suppressed indefinitely with certain HAART regimens. In previously treated patients, the benefits of HAART are often significantly diminished.