Efavirenz, nelfinavir, and stavudine rescue combination therapy in HIV-1-positive patients heavily pretreated with nucleoside analogues and protease inhibitors

Nelfinavir and non-nucleoside reverse transcriptase inhibitor-based salvage regimens in heavily HIV pretreated patients

OBJECTIVE

To assess the efficacy of nelfinavir mesylate (NFV) in combination with delavirdine mesylate (DLV) or efavirenz (EFV) and other antiretroviral agents following virological failure on other protease inhibitor (PI)-based regimens.

DESIGN

Multicentre, retrospective chart review.

METHODS

One hundred-one patients who were naive to both NFV and non-nucleoside reverse transcriptase inhibitors (NNRTIs) and who initiated NFV plus DLV or EFV-based salvage regimens were reviewed. Response to treatment was defined as a reduction in HIV ribonucleic acid (RNA) levels to unquantifiable levels (less than 50 copies/mL, less than 400 copies/mL, less than 500 copies/mL) on at least one occasion after the initiation of salvage therapy. Baseline correlates of response, including prior duration of HIV infection, prior number of regimens, viral load and CD4 cell counts were also evaluated.

RESULTS

Patients had a mean duration of HIV infection of 10 years, a mean duration of prior therapy of four years, a median of four prior nucleoside reverse transcriptase inhibitors and a median of two prior PIs. At the time of review the mean duration of salvage therapy was 63.4 weeks. Virological suppression was achieved in 59 (58.4%) patients within a mean of eight weeks and maintained for a mean of 44.9 weeks (the mean follow-up was 78 weeks). Of the non-responders, 16 (38%) achieved a less than 1 log(10) decrease in HIV RNA levels. Although there was no association between baseline correlates, response rate (75.7%) was significantly higher in patients with HIV RNA levels of 50,000 copies/mL or lower and CD4 counts greater than 200 cells/mm(3).

CONCLUSION

NFV/NNRTI-based highly active antiretroviral therapy regimens are an effective therapy in many patients who have experienced virological breakthroughs on at least one prior PI-based regimen.

Novel tight binding PETT, HEPT and DABO-based non-nucleoside inhibitors of HIV-1 reverse transcriptase

Non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs) are a key component of effective combination antiretroviral therapies for HIV/AIDS. NNRTIs despite their chemical diversity, bind to a common allosteric site of HIV-1 RT, the primary target for anti-AIDS chemotherapy, and noncompetitively inhibit DNA polymerization. NNRTIs currently in clinical use have a low genetic barrier to resistance and therefore, the need for novel NNRTIs active against drug-resistant mutants selected by current therapies is of paramount importance. We describe the chemistry and biological evaluation of highly potent novel phenethylthiazolylthiourea (PETT), 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT) and dihydroalkoxybenzyloxopyrimidine (DABO) derivatives targeting the hydrophobic binding pocket of HIV-1 RT. These NNRTIs were rationally designed by molecular modeling and docking studies using a novel composite binding pocket that predicted how drug-resistant mutations would change the RT binding pocket shape, volume, and chemical make-up and how these changes could affect NNRTI binding. Several ligand derivatization sites were identified for docked NNRTIs that fit the composite binding pocket. The best fit was determined by calculating an inhibition constant (Ludi Ki) of the docked compound for the composite binding pocket. Compounds with a Ludi Ki of <1 microM were identified as the most promising tight binding NNRTIs. These NNRTIs displayed high selective indices with robust anti-HIV-1 activity against the wild-type and drug-resistant isolates carrying multiple RT gene mutations. The high rate of treatment failure due to the emergence of drug resistance mutations makes the discovery of broad-spectrum PETT, HEPT and DABO-based NNRTIs useful as a component of effective combination regimens.

Nelfinavir: a review of its use in the management of HIV infection

Nelfinavir (Viracept) is an orally administered protease inhibitor. In combination with other antiretroviral drugs (usually nucleoside reverse transcriptase inhibitors [NRTIs]), nelfinavir produces substantial and sustained reductions in viral load in patients with HIV infection. Nelfinavir may be used in the treatment of adults, adolescents and children aged >or=2 years with HIV infection. It can also be used in pregnancy. Resistance to nelfinavir may develop, but the most common mutation (D30N, appearing mainly in HIV-1 subtype B) does not confer resistance to other protease inhibitors, thereby conserving these agents for later use. Although less effective than lopinavir/ritonavir, the preferred first-line treatment in US guidelines, nelfinavir is positioned as an alternative agent for the treatment of adults and adolescents with HIV infection and is an option for those unable to tolerate other protease inhibitors. Nelfinavir also has a role in the management of pregnant patients as well as paediatric patients with HIV infection.

A randomized controlled trial to evaluate antiretroviral salvage therapy guided by rules-based or phenotype-driven HIV-1 genotypic drug-resistance interpretation with or without concentration-controlled intervention: the Resistance and Dosage Adapted Regimens (RADAR) study

BACKGROUND

It is not well defined whether concentration-controlled intervention (CCI) and rules-based human immunodeficiency virus (HIV) type 1 genotype drug-resistance interpretation (GI) or virtual phenotype drug-resistance interpretation (VPI) may improve the outcome of HIV salvage therapy.

METHODS

In a prospective, randomized, controlled trial, patients were randomized (on a factorial basis) to change treatment after either GI or VPI, and they then were further randomized to the control arm (no CCI) or the CCI arm. Protease inhibitor (PI) and nonnucleoside reverse-transcriptase inhibitor (NNRTI) trough concentration (Ctrough) values were determined at weeks 1, 4, 12, and 24 of the study.

RESULTS

Among 230 patients, virological benefit (defined by an HIV RNA load of <400 copies/mL at week 24) was not statistically different, either between patients in the GI and VPI arms or between patients in the CCI and control arms. A virological benefit was found for patients in the CCI arm, compared with patients in the control arm, but this benefit was not statistically significant (56.8% vs. 64.3% at week 4 and 63.6% vs. 74% at week 12). Dosage adaptation was possible for only a fraction of patients, because of low rates of treatment adherence or patient refusal to increase dosages. In the logistic regression analysis, independent predictors of virological response at week 24 were a PI Ctrough value and/or an NNRTI Ctrough value in the higher quartiles (or above cutoff levels) and a low number of PIs previously received. Moreover, receipt of a regimen that contained PIs boosted with ritonavir was an independent predictor of virological response.

CONCLUSIONS

The present study did not support the routine use of CCI for patients undergoing salvage treatment, probably as a result of existing difficulties associated with its clinical application. However, a higher Ctrough value appeared to be correlated with treatment response. No major differences were found between VPI or GI when they are used together with expert advice for the selection of salvage treatment combinations.

Effectiveness of Antiretroviral Therapy after Protease Inhibitor Failure: An Analytic Overview

To examine effectiveness of subsequent antiretroviral therapy (ART), studies published during the period of 1 January 1997 through 31 May 2003 involving patients who had failed a protease inhibitor (PI)-containing regimen and were switched to another regimen were reviewed. Twelve studies describing 1197 patients were analyzed. A total of 38% of patients had human immunodeficiency virus (HIV) RNA levels of <500 copies/mL at 24 weeks. After adjustment for baseline HIV RNA level, the rate of virologic suppression ranged from 16% for patients switching drugs within previously failed classes to 54% for nonnucleoside reverse-transcriptase inhibitor (NNRTI)-naive patients switched to boosted PI- and NNRTI-containing regimens. ART regimens in patients who failed a PI-containing regimen provided virologic suppression only in a few patients. The best response was seen in NNRTI-naive patients receiving NNRTI- and boosted PI-containing regimens. New approaches are needed to achieve better suppression in pretreated HIV-infected patients.

Primary nelfinavir (NFV)-associated resistance mutations during a follow-up period of 108 weeks in protease inhibitor naïve patients treated with NFV-containing regimens in an HIV clinic cohort

BACKGROUND

Nelfinavir (NFV) is a widely prescribed HIV-1 specific protease inhibitor (PI). However, there are only a few reports that have described the long-term effects of NFV-containing regimens, especially with regard to the emergence of drug resistance in inner-city clinics.

OBJECTIVES

The aim of this study was to investigate the clinical and virologic responses to treatment with NFV-containing regimens for up to 108 weeks and determine the timing and rate of emergence of primary NFV-resistance associated mutations in daily clinical practice.

STUDY DESIGN

A cohort study in an inner-city clinic. Our study included 51 consecutive patients who were PI-nai;ve and commenced therapy in February 1997 through April 1999.

RESULTS AND CONCLUSIONS

The proportions of patients who continued the same therapeutic regimen and showed virologic success (viral load <400 copies/ml) up to 108 weeks were 78 and 63%, respectively, based on intent-to-treat analysis. Among patients with a viral load persistently >400 copies/ml at week 12 (n=30), 11 developed primary NFV-resistance associated mutations by 108 weeks (stratified log-rank test; P<0.05). The Cox proportional hazard model showed that prior use of reverse transcriptase inhibitors (n=22) (relative hazard (RH); 2.10, 95% CI; 0.67-6.62), prior AIDS diagnosis (n=6) (RH; 1.70, 95% CI; 0.37-7.77), CD4 < 200/microl at baseline (n=19) (RH; 2.48, 95% CI; 0.78-7.81) and viral load >30,000 copies/ml at baseline (n=21) (RH; 2.10, 95% CI; 0.67-6.62) were not independent predictors of the NFV-resistance, although some tendency was noted. In total, 77% of the patients continued NFV-containing treatment without the NFV-resistance for 108 weeks. The viral load at week 12 could be used as a predictor of treatment success in our cohort study.

Prospective comparison of first-line nelfinavir therapy versus nelfinavir introduction in rescue antiretroviral regimens

In order to establish the role of the protease inhibitor nelfinavir in current clinical practice, a prospective 18-month open-label comparison of efficacy and tolerability of nelfinavir was performed among HIV-infected patients who either incorporated nelfinavir in their first-line highly active antiretroviral therapy (HAART) regimen (group A, 57 patients), or who added nelfinavir to a rescue antiretroviral regimen (following at least two attempts with protease inhibitor-based HAART) (group B, 67 patients). All evaluable data were analyzed according to the prior and concurrent antiretroviral therapy, including genotypic resistance assays for patients undergoing salvage therapy. A significantly better virologic outcome (as expressed by a > 2 log(10) drop of plasma viremia versus baseline or attainment of undetectable levels), was shown among patients belonging to group A versus group B, where a number of genotypic mutations possibly elicited by previous anti-HIV treatment strongly impaired a potent and sustained nelfinavir activity. On the whole, the immunologic response (as expressed by the mean CD4(+) lymphocyte count versus baseline), substantially paralleled the virologic one in all analyzed subgroups, but a tendency toward a maintained immunologic competence was also observed in the majority of patients experiencing virologic failure. Nelfinavir introduction was sufficiently safe, because a limited percentage of patients suffered from mild-to-moderate, novel, or continuing adverse events, which proved significantly more frequent in the salvage group but did not affect adherence to HAART.

Modulation of human immunodeficiency virus (HIV)-specific immune response by using efavirenz, nelfinavir, and stavudine in a rescue therapy regimen for HIV-infected, drug-experienced patients

Analysis of the virologic and immunomodulatory effects of an association of efavirenz (EFV), nelfinavir (NFV), and stavudine (d4T) was performed in 18 human immunodeficiency virus (HIV)-infected and highly active antiretroviral therapy (HAART)-experienced patients who failed multiple therapeutic protocols. Patients (<500 CD4(+) cells/ micro l; >10,000 HIV copies/ml) were nonnucleoside reverse transcriptase inhibitor (NNRTI)-naive and were treated for 10 months with EFV (600 mg/day) in association with NFV (750 mg three times daily) and d4T (30 or 40 mg twice daily). Measurement of HIV peptide- and mitogen-stimulated production of interleukin-2 (IL-2), gamma interferon (IFN-gamma), IL-4, and IL-10 as well as quantitation of mRNA for the same cytokines in unstimulated peripheral blood mononuclear cells were performed at baseline and 2 weeks (t1), 2 months (t2), and 10 months (t3) into therapy. The results showed that HIV-specific (but not mitogen-stimulated) IL-2 and IFN-gamma production was augmented and IL-10 production was reduced in patients who received EFV, NFV, and d4T. Therapy was also associated with a reduction in HIV RNA in plasma and an increase in CD4(+) cell count. These changes occurred in the first year of therapy (t2 and t3) and were confirmed by quantitation of cytokine-specific mRNA. Therapy with EFV, NFV, and d4T increases HIV-specific type 1 cytokine production as well as CD4 counts and reduces plasma viremia. This therapeutic regimen may be considered for use in cases of advanced HIV infection.

The use of efavirenz as a part of late rescue antiretroviral treatment

PURPOSE

Because rescue antiretroviral strategies are increasingly needed, patients' response to a late salvage treatment including efavirenz plus a novel protease inhibitor (PI), with or without at least one novel nucleoside analogue, was assessed.

METHOD

41 consecutive patients, who underwent four or more prior therapeutic failures and received nucleoside analogues alone for > or = 18 months and a PI-based HAART for > or = 15 months, had a 12- to 24-month prospective follow-up. 6 patients who interrupted treatment after 3-8 weeks because of side effects were excluded. In the remaining 35 evaluable participants, the efavirenz-containing rescue regimen included nelfinavir in 23 cases, indinavir in 7, ritonavir in 2, and ritonavir plus hard gel saquinavir in the remaining 3 cases. 17 of 35 patients concurrently introduced one or more novel nucleoside analogues. Initial mean viremia was 4.8 +/- 0.9 log(10) HIV RNA copies/mL, while mean baseline CD4+ lymphocyte count was around 100 cells/microL. Genotyping resistance testing was obtained at the time of treatment modification.

RESULTS

The virologic response was both limited and transient. A significant drop of mean viremia was reached at the third month (-0.7 log(10)), but it was not maintained beyond the sixth month; only 4 patients reached viral suppression during the first 6 months. A more evident and sustained benefit on CD4+ cell count was observed throughout the study (p <.007, compared with baseline). The 31 patients who remained evaluable beyond 12 months did not show relevant modifications of laboratory parameters. The patient subgroup that received > or = 1 novel nucleoside analogue at the time of efavirenz adjunct had a significantly more favorable virologic outcome until the ninth month of follow-up and included all cases who reached viral suppression. Antiviral resistance pattern showed frequent mutations of the protease gene, and a cross-resistance with nonnucleoside reverse transcriptase inhibitors (NNRTIs; found in 19 cases of 41), although our patients were not previously exposed to these compounds.

CONCLUSION

A late salvage therapy based on efavirenz plus a novel PI is not expected to achieve a complete and sustained virologic success in patients highly experienced with both nucleoside analogues and PIs and with a concurrent elevated viremia, probably due to extensive resistances acquired through time. Our rate of virologic failure proved even greater than that observed in previous studies of salvage therapy including NNRTIs. Prior long-term treatment with isolated nucleoside analogues and HAART, the use of highly sensitive techniques for monitoring of viremia, and a quite prolonged observation period may have played a role. However, the CD4+ response proved to be more evident and sustained than the virologic one, and the concurrent introduction of >/= 1 nucleoside analogue added significantly, especially during the first 9 months of salvage therapy.

A randomized trial of nelfinavir, ritonavir, or delavirdine in combination with saquinavir-SGC and stavudine in treatment-experienced HIV-1-infected patients

PURPOSE

To evaluate the 24-week impact of saquinavir-enhancing antiretroviral therapy on viral replication in patients previously treated with nucleoside analogues with or without prior saquinavir hard-gel capsules (HGC).

METHOD

Patients were randomized in three groups to receive the following: Group 1-nelfinavir (750 mg tid), saquinavir soft-gel capsule (SGC) (800 mg tid), and stavudine (40 mg bid); Group II-ritonavir (400 mg bid), saquinavir-SGC (400 mg bid), and stavudine (40 mg bid); or Group III-delavirdine (400 mg tid), saquinavir-SGC (800 mg tid), and stavudine (40 mg bid). Viral loads, CD4 count, and safety were assessed over a 24-week period with an additional 6-month follow-up.

RESULTS

73 patients received randomized therapy; 14 of whom were SQV naïve, with a median baseline viral load of 3.6 log(10) and a CD4 count of 370 cells/mm(3). By 6 months, the median decreases in plasma viral loads were 0.26, 0.71, and 0.29 log(10) copies/mL for groups I, II, and III, respectively. The median increases in CD4 counts, for groups I, II, and III, were 52, 40, and 69 cells/mm(3) at 6 months, respectively. Changes in viral load and CD4 counts at 6 months and 1 year were not significantly different between the treatment groups. More patients discontinued therapy in the ritonavir arm (35%) for drug intolerance or toxicity compared to either the nelfinavir or delavirdine arms (15% and 5%, respectively). In a multivariate analysis, baseline viral load, younger age, and baseline saquinavir resistance were significantly associated with detectable viral load at 24 weeks.

CONCLUSION

The use of antiretroviral agents that pharmacokinetically boost saquinavir levels has a modest benefit in saquinavir-experienced patients.

Efavirenz: a pharmacoeconomic review of its use in HIV infection

Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in the treatment of patients with HIV infection. Both US and British treatment guidelines for HIV infection recommend NNRTI- or protease inhibitor-based combinations [i.e. with nucleoside reverse transcriptase inhibitors (NRTIs)] as first-line treatmentoptions in the management of HIV disease. Results of a pivotal randomised study (DMP 266-006) comparing efavirenz- versus indinavir-based triple combination therapy in patients with HIV infection (the majority of whom were antiretroviral therapy-naive) showed the efavirenz-based regimen was better tolerated and had greater success in achieving reductions in viral load below the limit of detection. These and other clinical data were incorporated into economic models in 2 analyses, one conducted in the US and the other in Canada. The US analysis examined long term clinical and economic outcomes predicted on the basis of response (viral load and CD4+ cell counts), tolerability and willingness to adhere to therapy. The efavirenz-based regimen was the dominant treatment strategy as it was predicted to improve survival and reduce direct medical costs in the US healthcare system. Compared with the indinavir-containing regimen, survival was increased by 11% (absolute difference) and cumulative costs were reduced by $US10,326 per patient (1998 discounted costs) at 5 years after starting treatment with efavirenz-based therapy. The Canadian analysis was conducted from the perspective of the Ontario healthcare system. This study did not consider differences in clinical efficacy between treatment groups, costs of study medication or outcomes beyond 1 year--all factors that would have favoured the efavirenz-based regimen. Of the 2 treatment options, the efavirenz-based regimen was associated with 7.4% lower average annual medical care costs, primarily because of greater costs associated with adverse clinical events with the indinavir-based regimen. In conclusion, current treatment guidelines for HIV infection recognise efavirenz-based combination regimens as a first-line treatment option. A pivotal comparative clinical trial (DMP 266-006) showed a significantly greater virological response to efavirenz- than indinavir-based triple combination therapy, and the efavirenz-based regimen was better tolerated. These clinical data are supported by pharmacoeconomic analyses conducted in the US and Canada, both of which showed lower medical care costs with the efavirenz-based regimen. The US analysis also predicted long term health benefits, such as improved survival, with efavirenz- versus indinavir-based triple combination therapy. These results must be weighed against the inherent difficulties of predicting long term treatment failure rates from short term data, and the limited number of pharmacoeconomic analyses conducted with efavirenz to date.