Impact of drug resistance mutations on virologic response to salvage therapy. Swiss HIV Cohort Study

Effect of polymorphisms on the replicative capacity of protease inhibitor-resistant HIV-1 variants under drug pressure

The role of drug pressure on the replicative capacity of protease inhibitor-resistant HIV-1 variants and the contribution of a common amino-acid polymorphism in the protease gene (L63P) to this process were investigated. Using HIV-1 variants resistant to the protease inhibitors saquinavir (G48V/L90M) or indinavir (A71V/V82T/I84V), viral replication was studied in the presence or absence of inhibitor and a mutation at position 63. The initial changes diminished enzyme function of the protease and reduced replicative capacity for both virus mutants. Addition of the respective inhibitor blocked the wild-type, but was also able to delay the replication kinetics of either mutant, revealing the limits of resistance. Importantly, the polymorphic change L63P, although not conferring inhibitor resistance by itself, provided a significant replication benefit to both mutant viruses, particularly under drug pressure, and may reveal a far-reaching compensating power of polymorphic changes. This may drive evolution and the directed selection of protease inhibitor-resistant HIV-1 variants, a finding with significant clinical and diagnostic implications.

Antiretroviral therapy in Africa

We should stop and think about the risks of resistance, and ways of minimising them, before increasing access to antiretroviral therapy in Africa

Emergence of protease inhibitor resistance-associated mutations in plasma HIV-1 precedes that in proviruses of peripheral blood mononuclear cells by more than a year

HIV-1 genotype assay using plasma viruses has been widely applied for detection of resistant viruses in infected individuals, whereas there are only a few reports about proviral genotype in peripheral blood mononuclear cells (PBMCs). To determine which sample, plasma or PBMC, should be used for early detection of drug-resistant viruses during antiretroviral treatment, we analyzed 275 plasma-derived and 211 PBMC-derived HIV-1 protease sequences obtained from HIV-1-infected patients during protease inhibitor (PI) therapy. In 70 of 107 pairs (65.4%) of plasma and PBMC samples taken from the same blood draws, the numbers of PI resistance-associated mutations in the plasma-derived genotype were different from those in the PBMC-derived genotype. Plasma viruses had more PI resistance-associated mutations than PBMC proviruses (P = 0.0004). Analysis of serial samples showed that plasma-derived genotype assay could detect primary mutations about 425 days earlier than PBMC-derived genotype when the plasma viral load was less than 10(4 )copies/mL. Our data suggest that genetic turnover of PBMC proviruses is slower than that of plasma viruses and that time lag between emergence of mutations in plasma-derived and PBMC-derived genotypes correlates inversely with viral load. Plasma viruses should be the material of choice for early detection of drug resistance during antiretroviral treatment.

Predictors of the virological response to a change in the antiretroviral treatment regimen in HIV-1-infected patients enrolled in a randomized trial comparing genotyping, phenotyping and standard of care (Narval trial, ANRS 088)

OBJECTIVE

To identify predictors of the virological response to antiretroviral therapy in patients in whom initial therapy has failed.

METHODS

The Narval trial was designed to compare phenotyping, genotyping and standard of care for the choice of antiretroviral therapy in patients in whom a protease inhibitor (PI)-containing regimen had failed. Virological success was defined as viral load below 200 copies/ml at week 12. Baseline variables including demographic, clinical and biological characteristics, HIV reverse transcriptase and protease mutations, the randomization arm, the drugs prescribed, as well as adherence to treatment and plasma concentrations of PIs and non-nucleoside reverse transcriptase inhibitors (NNRTIs) at week 12 were tested in the model. Variables that were significantly associated with virological success in univariate analysis were included in a logistic regression model.

RESULTS

Five-hundred-and-forty-one patients were randomized. Virological success at week 12 was obtained in 200 patients. In multivariate analysis, the following factors were significantly associated with virological success: prescription of efavirenz to NNRTI-naive patients (OR=4.37; 95% CI: 2.76-6.90), randomization to the genotyping arm (OR=2.13, 1.20-3.79), prescription of lamivudine (OR=1.69, 1.01-2.83) and prescription of abacavir to abacavir-naive patients (OR=1.66, 1.02-2.72). Factors significantly associated with virological failure were prescription of nelfinavir (OR=0.30, 0.13-0.68), a high baseline viral load (OR=0.37, 0.28-0.50), the presence of at least five PI mutations (OR=0.42, 0.26-0.66), the presence of at least three thymidine analogue mutations (OR=0.61, 0.39-0.97) and at least 30 months of prior PI exposure (OR=0.64, 0.41-0.99).

CONCLUSIONS

These results confirm that among heavily pretreated patients, prescription of efavirenz to NNRTI-naive patients is associated with a good virological response, while a high baseline viral load, a large number of PI mutations and nelfinavir prescription at baseline are associated with a poor virological response. Genotyping was found to be beneficial, while this was not the case for phenotyping. This work was presented at the XI International HIV Drug Resistance Workshop, Sevilla, Spain, July 3-6 2002 (Abstract N(o)133); and at the XIV International Conference on AIDS, Barcelona, Spain, July 7-11 2002 (Abstract N(o)ThOrB138).

How does expert advice impact genotypic resistance testing in clinical practice?

The Havana trial, a randomized, prospective study, demonstrated that expert interpretation of genotypic resistance test (GRT) results improved virological outcomes in human immunodeficiency virus type 1 (HIV-1)-infected patients for whom highly active antiretroviral therapy (HAART) was failing. The impact of expert advice in routine clinical practice is unknown. We retrospectively evaluated the virological outcomes of 74 patients for whom HAART was failing and whose clinical providers accepted or rejected HAART regimens recommended by an expert panel who routinely reviewed GRT results. Fifty (68%) of 74 patients received regimens recommended by the expert panel ("advice accepted" [AA]), and 24 patients (32%) received regimens per the clinician's preference ("advice rejected" [AR]). After 24 weeks, AA and AR groups had median decreases in the plasma HIV-1 RNA viral load of 2.6 and 1.3 log(10) copies/mL, respectively (P=.0001). Twenty-six (52%) of 50 patients in the AA group and 5 (21%) of 24 patients in the AR group had a plasma HIV-1 RNA viral load of <50 copies/mL (P=.01). Consideration should be given to enlisting expert assistance in the interpretation of GRT results in routine clinical practice.

Antiretroviral drug resistance testing in adults infected with human immunodeficiency virus type 1: 2003 recommendations of an International AIDS Society-USA Panel

New information about the benefits and limitations of testing for resistance to human immunodeficiency virus (HIV) type 1 (HIV-1) drugs has emerged. The International AIDS Society-USA convened a panel of physicians and scientists with expertise in antiretroviral drug management, HIV-1 drug resistance, and patient care to provide updated recommendations for HIV-1 resistance testing. Published data and presentations at scientific conferences, as well as strength of the evidence, were considered. Properly used resistance testing can improve virological outcome among HIV-infected individuals. Resistance testing is recommended in cases of acute or recent HIV infection, for certain patients who have been infected as long as 2 years or more prior to initiating therapy, in cases of antiretroviral failure, and during pregnancy. Limitations of resistance testing remain, and more study is needed to refine optimal use and interpretation.

Prevalence and virologic consequences of HIV-1 genotype mutations detected in a cohort of 161 Italian patients receiving a nelfinavir-based highly active antiretroviral therapy

A cross-sectional study was carried out in our tertiary care hospital between January 1998 and December 2001. All 161 consecutive patients naive to nelfinavir and who had received a nelfinavir-based highly active antiretroviral therapy (HAART) of at least 24-week duration were extrapolated from the 802 adult HIV-infected subjects treated with antiretroviral therapy. All cases of virologic failure were considered and viral genotyped. Virologic failure occurred in 80 out of 161 nelfinavir-treated patients, all belonging to the experienced group. On the whole, only 11 patients (7%) developed the D30N substitution, whose 6 was in association with the N88D mutation. Among the 80 failed patients, the M184V mutation was detected in 52 (65%), while only 7 patients showed simultaneously the M184V, T215Y and K103N substitutions. In our HIV-infected population receiving a nelfinavir-based HAART, the D30N mutation has shown a low absolute frequency, while the detection of M184V substitution and the simultaneous occurrence of M184V, T215Y and K103N mutations were related to a more favorable virological response.

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.

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.

No increase in protease resistance and a decrease in reverse transcriptase resistance mutations in primary HIV-1 infection: 1992-2001

Rates of antiretroviral resistance in recently transmitted virus in Sydney, Australia fluctuated over the past decade, influenced by treatment trends. Current rates of drug resistance are not high in historical terms or compared with those reported. Rates of resistance to reverse transcriptase inhibitors peaked in the mid-1990s, fell dramatically with the introduction of combination therapy and appear to have plateaued at 10-15% over the past 3 years. Primary resistance mutations in the protease gene are still rare.

Drug resistance mutations and outcome of second-line treatment in patients with first-line protease inhibitor failure on nelfinavir-containing HAART

OBJECTIVES

To determine resistance mutations emerging in HIV-1-infected patients experiencing their first protease inhibitor (PI)-failure on nelfinavir-containing highly active antiretroviral therapy (HAART), and to assess virological response to rescue regimens.

METHODS

Plasma HIV-1 RNA from 24 patients failing nelfinavir-containing HAART was sequenced. Failure was defined as two consecutive measurements of viral load > 400 HIV-1 RNA copies/mL. Patients with previous failure on other PIs were excluded. Data on response to second-line treatment was extracted from patient files.

RESULTS

At failure primary protease mutations were found in 14 patients (58%). Ten patients had D30N (38%), five patients had L90M (19%), two patients had V82A/F (8%) and two patients had M46I/L (8%). Two patients had both D30N and L90M. Pronounced increases of secondary protease mutations were seen at codon 88 (Delta: 33%), codon 36 (Delta: 30%) and codon 71 (Delta: 17%). Of eight patients with N88D, seven also harboured D30N (P < 0.01). Polymorphisms at codon 63 were detected at baseline in all patients who developed primary resistance mutations at failure (P < 0.01). On rescue regimens, 78% achieved viral loads below limit of detection (BLD). The presence of primary protease mutations was not associated with a higher risk of failure on second-line treatment.

CONCLUSION

In patients failing nelfinavir-containing HAART, D30N was detected frequently and L90M occasionally. A pronounced accumulation of the secondary protease mutations N88D, M36I, and A71V/T was found, and D30N was strongly associated with N88D. A high proportion of patients became undetectable on second-line treatment and the presence of primary resistance mutations did not negatively affect the outcome of rescue regimens.

HIV-1 drug resistance: can we overcome?

Highly active antiretroviral therapy (HAART) targeting the viral reverse transcriptase and protease enzymes has advanced the treatment of HIV/AIDS. Nucleoside and non-nucleoside reverse transcriptase inhibitors and protease inhibitors used in combination can suppress viral replication thereby delaying disease progression. Emergence of HIV-1 mutated strains, resistant to one or more antiretroviral inhibitors or drug classes, remains one of the leading causes of treatment failure among patients living with HIV/AIDS. While advances in genotypic and phenotypic testing allow for drug resistance guided therapeutic management, the increasing prevalence of multi-drug resistance and an absence of new drug classes forewarn new problems in sustaining the effectiveness of HAART. One promising hope for continued benefit of antiretroviral therapy despite emergent resistance is the observed reduction in replicative ability or 'fitness' of multimutated viruses. This review discusses the development and influence of known drug mutations on drug susceptibility versus viral fitness.

Antiretroviral-drug resistance among patients recently infected with HIV

BACKGROUND

Among persons in North America who are newly infected with the human immunodeficiency virus (HIV), the prevalence of transmitted resistance to antiretroviral drugs has been estimated at 1 to 11 percent.

METHODS

We performed a retrospective analysis of susceptibility to antiretroviral drugs before treatment and drug-resistance mutations in HIV in plasma samples from 377 subjects with primary HIV infection who had not yet received treatment and who were identified between May 1995 and June 2000 in 10 North American cities. Responses to treatment could be evaluated in 202 subjects.

RESULTS

Over the five-year period, the frequency of transmitted drug resistance increased significantly. The frequency of high-level resistance to one or more drugs (indicated by a value of more than 10 for the ratio of the 50 percent inhibitory concentration [IC50] for the subject's virus to the IC50 for a drug-sensitive reference virus) increased from 3.4 percent during the period from 1995 to 1998 to 12.4 percent during the period from 1999 to 2000 (P=0.002), and the frequency of multidrug resistance increased from 1.1 percent to 6.2 percent (P=0.01). The frequency of resistance mutations detected by sequence analysis increased from 8.0 percent to 22.7 percent (P<0.001), and the frequency of multidrug resistance detected by sequence analysis increased from 3.8 percent to 10.2 percent (P=0.05). Among subjects infected with drug-resistant virus, the time to viral suppression after the initiation of antiretroviral therapy was longer (P=0.05), and the time to virologic failure was shorter (P=0.05).

CONCLUSIONS

The proportion of new HIV infections that involve drug-resistant virus is increasing in North America. Initial antiretroviral therapy is more likely to fail in patients who are infected with drug-resistant virus. Testing for resistance to drugs before therapy begins is now indicated even for recently infected patients.

The Effect of Number of Mutations and of Drug-Class Sparing on Virological Response to Salvage Genotype-Guided Antiretroviral Therapy

Objective

To assess on longitudinal data the impact of number of drug-associated mutations at genotype resistance testing (GRT) and history of previous exposure to antiretrovirals on the virological response to genotype-guided antiretroviral therapy.

Methods

Subjects that failed HAART who underwent GRT between June 1999 and March 2002 were enrolled. GRT was performed by Viroseq-2 with expert advice offered to physicians. Main outcome was reaching undetectable (<80 copies/ml) HIV-1 RNA level after GRT and maintaining undetectable viraemia for at least 6 months. The number of mutations conferring resistance to each class of antiretrovirals was categorized and their effect on virological outcome investigated. Mutations considered in the analysis were those reported by the IAS-USA in 2002. Multivariate analysis was performed by Cox proportional hazard model.

Results

Four-hundred-and-seventy consecutive subjects were enrolled and followed-up for a median of 14 (IQR 9–19) months after GRT. Sustained undetectable viraemia was reached by 80 of 449 subjects (18%). Using as end-point reaching and maintaining for at least 6 months <400 copies/ml after GRT, 103 out of 447 subjects (23%) reached the outcome. For each single protease inhibitor (PI)-, nucleoside reverse transcriptase inhibitor (NRTI)-and non-nucleoside reverse transcriptase inhibitor (NNRTI)-associated mutation, there was a reduction of, respectively, 11% ( P=0.008), 12% ( P=0.001) and 39% ( P=0.005) in the likelihood of reaching virological outcome. Subjects carrying ≥6 mutations to NRTIs, ≥7 mutations to PIs and ≥2 mutations to NNRTIs were less likely to reach the virological success compared with those carrying 0–1 (NRTI and PI) or 0 (NNRTI) mutations [HR=0.25 (95% CI: 0.10–0.65); HR=0.33 (95% CI: 0.16–0.67); HR=0.33 (95% CI: 0.14–0.77)], respectively. However, at multivariate analysis the probability of reaching a favourable virological outcome in patients with ≥7 mutations to PIs, if naive for NNRTIs [HR=1.74 (0.69–4.36)], and in subjects with ≥2 mutations for NNRTIs if naive for PIs [HR=1.23 (0.22–6.80)], was comparable to those observed in patients with none or one mutation.

Conclusions

Our data showed a non-linear association between resistance-conferring mutations and virological outcome. GRT-guided therapy still provided remarkable chances of durable virological success even in subjects with ≥7 mutations to PIs and in subjects with ≥2 mutations to NNRTIs, when the subjects did not have a three-class exposure or if GRT showed no evidence of mutations for a drug class. GRT and as-long-as-possible sparing of a drug class could be a convenient strategy for long-term management of drug-failing patients.

Phenotype or Virtual Phenotype for Choosing Antiretroviral Therapy after Failure: A Prospective, Randomized Study

Background

Resistance testing is useful in the management of virological failure patients, although the best method to be used in clinical practice has not been determined.

Methods

A prospective, randomized, double-blind, multicentre, controlled clinical trial was performed to compare the usefulness of drug resistance testing with a recombinant viral phenotype method or with a virtual phenotype, a genotyping interpretation system. Planned 300 HIV-infected adults failing their current antiretroviral therapy (HIV RNA >1000 copies/ml) were centrally randomized 1:1 to resistance testing with a recombinant viral phenotype method or with a virtual phenotype, after stratifying according to previous drug exposure (one or two versus three drug classes). Percent of patients with HIV RNA suppression (% <400 copies/ml) after 24 weeks was the primary outcome variable. Median HIV RNA concentration and change from baseline in HIV RNA concentration were also used to compare effectiveness. An extended analysis was performed at week 48.

Results

Of the 300 patients enrolled, a total of 276 patients could be analysed; 139 patients were randomized to the phenotype group and 137 patients were randomized to the virtual phenotype group. After 24 weeks of follow-up, 46.8 and 56.2% of patients had HIV RNA <400 copies/ml ( P=0.1) in the phenotype and virtual phenotype, respectively. Mean decrease from baseline in viral load was 1.0 and 1.3 log copies/ml in the phenotype and virtual phenotype groups, respectively ( P=0.017). In a multivariate linear regression analysis, after adjusting for baseline HIV RNA and adherence to treatment, the virtual phenotype was associated with a greater mean decrease in plasma HIV RNA ( P=0.0063). The results observed at week 48 were similar.

Conclusions

Virtual phenotype is at least as effective as phenotype when used to select an optimized treatment for patients who have failed one or more antiretroviral regimens.

Antiretroviral prophylaxis of perinatal HIV-1 transmission and the potential impact of antiretroviral resistance

Since 1994, trials of zidovudine, zidovudine and lamivudine, and nevirapine have demonstrated that these antiretroviral drugs can substantially reduce the risk of perinatal HIV-1 transmission. With reductions in drug price, identification of simple, effective antiretroviral regimens to prevent perinatal HIV-1 transmission, and an increasing international commitment to support health care infrastructure, antiretrovirals for both perinatal HIV-1 prevention and HIV-1 treatment will likely become more widely available to HIV-1-infected persons in resource-limited countries. In the United States, widespread antiretroviral usage has been associated with increased antiretroviral drug resistance. This raises concern that drug resistance may reduce the effectiveness of perinatal antiretroviral prophylaxis as well as therapeutic intervention strategies. The purpose of this article is to review what is known about resistance and risk of perinatal HIV transmission, assess the interaction between antiretroviral resistance and the prevention of perinatal HIV-1 transmission, and discuss implications for current global prevention and treatment strategies.

[Factors associated with resistance to human immunodeficiency virus protease inhibitors]

BACKGROUND

To assess the risk factors associated with genotypic resistance to protease inhibitors (PI) in HIV-infected subjects with virologic failure despite highly active antiretroviral treatment (HAART).

PATIENTS AND METHOD

Retrospective chart review including 47 consecutive patients with virologic failure despite PI-based HAART who had undergone a genotypic HIV-1 testing. The prevalence of genotypic resistance to PI was determined and several demographic, clinical and laboratory variables were compared between patients with and without genotypic resistance to those drugs.

RESULTS

The entire nucleotide sequence of the protease gene was obtained in 43 of the 47 patients; 18 of them had genotypic resistance to PI. Genotypic resistance to PI was associated with a previous therapy with suboptimal antiretroviral regimens (OR = 10.2; 95% CI, 1.05-245.1; P = 0.02), duration of antiretroviral therapy longer than 18 months (OR = 13.3; 95% CI, 1.23-340.85; P = 0.01), greater number of antiretroviral regimens and drugs before the virologic failure (p < 0.01) and presence of the 184V mutation in the reverse transcriptase gene (OR = 5.6; 95% CI, 1.2-29.2; P = 0.02). There was no relationship between PI resistance and the risk group, viral load or CD4 cell count. In the multivariate analysis, previous therapy with suboptimal antiretroviral regimens was the better predictor of PI resistance (OR = 11.1; 95% CI, 1.04-117.47; P = 0.046).

CONCLUSIONS

Patients treated with suboptimal antiretroviral activity regimens before starting HAART can be at greater risk of developing genotypic resistance to protease inhibitors.

High prevalence of HIV-1 subtype G and natural polymorphisms at the protease gene among HIV-infected immigrants in Madrid

OBJECTIVES

Genetic characterization of HIV-1 subtypes among immigrants and natives infected overseas.

METHODS

Phylogenetic analysis of HIV-1 protease sequences obtained from 109 foreigners (mainly Africans) and 32 native individuals infected overseas attending a reference HIV/AIDS centre located in Madrid, Spain.

RESULTS

The overall rate of infection with HIV-1 non-B subtypes was 50.3% (71/141). Whereas 94.3% (67/71) belonged to immigrants (mostly Africans, 60/67), only 5.6% (4/71) were from native individuals (P < 0.05). The distribution of non-B subtypes was: 49 G, eight C, six A, four D, two F and two H. The high prevalence of subtype G was mainly related to individuals from west-central Africa. Interestingly, substitutions at three or more positions associated with protease inhibitor (PI) resistance were recognized in 52.6% of naive subjects carrying non-B subtypes, but only in 8% of those infected with B viruses (P < 0.05). The genotypes most frequently recognized among non-B and B subtypes occurred, respectively, at positions 36 (100 versus 12%), 20 (77.2 versus 0%), 63 (40.3 versus 64%), 82 (17.5 versus 0%), 10 (14 versus 12%), 77 (3.5 versus 34%), and 71 (0 versus 2%). Accordingly, changes I-36 and I-20 may be considered specific genetic markers for non-B, group M variants and subtype G infections, respectively.

CONCLUSION

Nearly two-thirds of foreigners with HIV-1 infection in Madrid carry non-B subtypes, subtype G (protease) being the most common among west-central African immigrants. The high rate of natural polymorphisms at the protease gene in non-B viruses may compromise the response to PI. Therefore, HIV subtyping should be considered in treatment guidelines.

Genotypic Correlates of Resistance to HIV-1 Protease Inhibitors on Longitudinal Data: The Role of Secondary Mutations

Direct sequencing of the pol gene was assessed retrospectively with protease inhibitor susceptibility in a longitudinal study. A total of 134 samples from 26 patients were analysed at regular intervals up to 2 years. Patients were included in virological failure despite indinavir, ritonavir or saquinavir based triple-drug therapy. Both the type and number of certain secondary protease mutations modulated the effect of primary mutations on phenotypic resistance. This was notably applicable to L10I/V, and to lesser extents to A71V/T. However, combinations of primary mutations, including I54V could predict resistance to the drug used and nelfinavir in more than 80%. In contrast, in vitro cross-resistance to amprenavir was rarely encountered. In addition, there was a relationship between a higher number of key mutations and poorer virological and clinical outcomes, respectively, from 6 and 3 months on. The key mutations were the protease mutations independently conferring phenotypic resistance and/or the reverse transcriptase mutations predicting treatment outcome. This relationship was independent from drug history, viral load and CD4 cell count measurements. In summary, even on a small sample size, sequence-based genotyping seems to be a good prognostic marker when performed longitudinally. In the context of primary resistance mutations, including additional secondary mutations, it may be useful in the prediction of phenotypic and clinical resistance. This should be assessed to optimize treatment monitoring before emergence of broadly cross-resistant virus.

Association of Antiretroviral Resistance Genotypes with Response to Therapy – Comparison of Three Models

Genotype-based resistance assays are commonly used to aid treatment in HIV-infected individuals failing anti-retroviral therapy. The relationship between genotype and antiretroviral therapy comes mostly from in vitro assays of the response to a single drugs although there is a need for a prediction of clinical response to combination therapy. We have compared three different methods of analysing genotype data as a predictor of clinical response in a small clinical cohort of highly antiretro-viral-experienced individuals failing therapy. No method performed well beyond 8 weeks into a new therapeutic regimen. A model based on the number of ‘primary’ mutations was statistically significant, but a multiple regression model, which identified specific mutations explained threefold more variation in response. Optimal prediction in this dataset was given by a model obtained from a classification tree analysis, in which genotype at amino acid sites 135 and 202 were combined with amino acid site 184, which explained over 50% of the deviance in the data and had a classification success of 86%.

Virological Success of Lopinavir/Ritonavir Salvage Regimen is Affected by an Increasing Number of Lopinavir/Ritonavir-Related Mutations

We evaluated the virological outcome of lopinavir/ritonavir (LPV/RTV) in 224 HIV-1-infected and protease inhibitor (PI)-experienced patients showing virological failure to a highly active antiretroviral therapy (HAART) regimen and followed up for at least 3 months. At baseline, the median level of plasma viraemia was 4.61 log10 copies/ml (range 3–6.48) and the median CD4 cell count was 219 cells/mm3 (range 1–836). During a median follow-up of 272 days (range 92–635), we observed an increase in the number of CD4 cells (P=0.02) and a dramatic decrease in plasma viraemia levels (P=0.0001), which became undetectable in 122 patients (54.5%). The closely related predictive factors were baseline plasma viraemia levels and the number of mutations known to reduce susceptibility to LPV/RTV. Thirty-one patients (13.8%) discontinued LPV/RTV during the follow-up, and one AIDS event and three deaths were recorded. Of the 134 patients (59.8%) who underwent a baseline genotype resistance test, 22 (16.4%) had ≥6 mutations known to reduce LPV/RTV susceptibility; plasma viraemia became undetectable in 76 patients (56.7%), only five of whom harboured ≥6 mutations at baseline (P=0.0001). The independent predictive factors related to virological success were plasma viraemia levels and the number of mutations reducing susceptibility to LPV/RTV at baseline; each additional log10 copies/ml of HIV RNA reduced the probability of virological success by 34.0% and each extra mutation by 14.5%.

Phenotypic or genotypic resistance testing for choosing antiretroviral therapy after treatment failure: a randomized trial

OBJECTIVE

To assess the respective value of phenotype versus genotype versus standard of care for choosing antiretroviral therapy in patients failing protease inhibitor-containing regimens.

METHODS

Patients with plasma HIV-1 RNA exceeding 1000 copies/ml were randomly allocated to phenotyping, genotyping, or standard of care.

RESULTS

Five-hundred and forty-one patients were randomized, 190 to phenotyping, 192 to genotyping and 159 to standard of care. The baseline median CD4 cell count (280 x 106 cells/l), the plasma HIV-1 RNA level (4.3 log10 copies/ml), and the number of drugs previously received (n = 6) were similar in the three arms. More patients in the standard-of-care arm received at least three new drugs (55% versus 20% in the other arms; P < 0.001) and a regimen containing drugs from the three different classes. Plasma HIV-1 RNA was < 200 copies/ml at week 12 in 35% of patients in the phenotyping arm, 44% in the genotyping arm and 36% in the standard-of-care arm (phenotyping versus standard of care, P = 0.918; genotyping versus standard of care, P = 0.120). In a secondary analysis of 179 patients experiencing a first protease inhibitor failure, the percentage of patients achieving HIV-1 RNA < 200 copies/ml was significantly higher in the genotyping arm (65%) than in the phenotyping (45%) and the standard-of-care arms (45%) (genotyping versus standard of care, P = 0.022).

CONCLUSIONS

Overall, resistance assays did not demonstrate benefit over standard of care. In patients with the most limited protease inhibitor experience, a significant benefit was observed in the genotyping arm.

HIV-1 genotype and phenotype correlate with virological response to abacavir, amprenavir and efavirenz in treatment-experienced patients

OBJECTIVE

To assess the safety and efficacy of three new drugs in patients with antiretroviral failure and to correlate retrospectively baseline factors with virological response.

DESIGN AND SETTING

Open-label, 48-week, single-arm, multi-center phase II trial conducted at nine US university or government clinics and private practices.

PATIENTS AND INTERVENTIONS

Patients with HIV-1 RNA > or =500 copies/ml despite > or =20 weeks of treatment with at least one protease inhibitor received abacavir 300 mg twice a day, amprenavir 1200 mg twice a day and efavirenz 600 mg once a day. Other antiretrovirals were prohibited until week 16 except for substitutions for possible abacavir hypersensitivity.

MAIN OUTCOME MEASURES

HIV RNA at weeks 16 and 48.

RESULTS

A total of 101 highly treatment-experienced patients enrolled; 60 were naive to non-nucleoside analog reverse transcriptase inhibitors (NNRTI). HIV RNA < 400 copies/ml was attained in 25 out of 101 (25%) patients at 16 weeks (35% of NNRTI-naive and 10% of -experienced patients) and 23 (23%) patients at 48 weeks (33% of naive and 7% of experienced patients). CD4 cells increased by a median of 15 x 10(6) and 43 x 10(6) cells/l at weeks 16 and 48, respectively. Drug-related rash occurred in 50 out of 99 (51%) of patients, and 17 out of 99 (17%) permanently discontinued one or more drugs as a result. Lower baseline viral load, fewer NNRTI-related mutations, absence of decreased abacavir (> or =4-fold) and efavirenz (> or =10-fold) susceptibility, and greater number of drugs to which virus was susceptible were associated with virological response at week 16.

CONCLUSIONS

Abacavir, amprenavir and efavirenz durably reduced HIV RNA and increased CD4 cell counts in a subset of treatment-experienced adults. Baseline viral load and some genotypic and phenotypic markers of resistance correlated with HIV RNA response.

Usefulness of monitoring HIV drug resistance and adherence in individuals failing highly active antiretroviral therapy: a randomized study (ARGENTA)

OBJECTIVE

To establish the influence of genotypic resistance-guided treatment decisions and patient-reported adherence on the virological and immunological responses in patients failing a potent antiretroviral regimen in a randomized, controlled trial in a tertiary care infectious diseases department.

PATIENTS

A total of 174 patients with virological failure were randomly assigned to receive standard of care (SOC) or additional genotypic resistance information (G). Adherence was measured by a self-administered questionnaire.

MAIN OUTCOMES MEASURES

Primary endpoints were the proportion with HIV-RNA < 500 copies/ml at 3 and 6 months by intention-to-treat analysis. Secondary endpoints were changes from baseline HIV-RNA levels and CD4 cell counts.

RESULTS

At entry, 25% had failed three or more highly active antiretroviral therapy (HAART) regimens and 41% three drug classes; there were more resistance mutations in G. In 127 evaluable questionnaires, 43% reported last missed dose during the previous week. At 3 months, 11 of 89 patients (12%) in SOC and 23 of 85 (27%) in G had HIV-RNA < 500 copies/ml (OR 2.63, 95% CI 1.12-6.26); the relative proportions were 17 and 21% at 6 months. CD4 cell changes did not differ between arms. Six month CD4 cell changes were +62 in adherent and -13 cells/microl in non-adherent patients (P < 0.01). Being assigned to G, good adherence, previous history of virological success, fewer experienced HAART regimens and lower baseline viral load were independently predictive of 3 month virological success.

CONCLUSION

The virological benefit of genotype-guided treatment decisions in heavily pre-exposed patients was short term. Patients adherence and residual treatment options influenced outcomes.

Low prevalence of antiretroviral drug resistance among HIV-1 seroconverters in London, 1984-1991

OBJECTIVES

To examine the prevalence of resistance mutations and natural polymorphisms to reverse transcriptase (RT) and protease inhibitors in a cohort of patients with defined seroconversion dates.

METHODS

Eligible patients were those attending an HIV centre in North London who seroconverted from HIV negative to positive status between 01/01/85 and 31/12/91 (n=104). Genotypic resistance analysis was performed on the first positive serum sample after seroconversion and before use of antiretroviral therapy using population-based sequencing of RT-PCR fragments and rule-based sequence interpretation (Vircogen).

RESULTS

Protease and RT sequences were successfully amplified from only 37 (35.6%) of the 104 seroconverters. Only one patient who seroconverted in August 1991 showed any evidence of significant mutations in the RT region, and this was associated with resistance to zidovudine (ZDV) (215Y and 210W). An additional patient who seroconverted in July 1991 had a TOR mutation and was classified as having intermediate resistance to ZDV. No spontaneous mutations were detected in the protease region.

CONCLUSIONS

Overall only 2 (5%) of these treatment-naïve individuals were infected with HIV variants resistant to ZDV. Although the data at present do not support the need for pretreatment genotyping, there is a need for continued surveillance of the frequency of resistance mutations in antiretroviral naïve patients since the introduction of highly active antiretroviral therapy.

Clinical utility of HIV-1 genotyping and expert advice: the Havana trial

OBJECTIVE

To determine whether HIV-1 genotyping and expert advice add additional short-term virologic benefit in guiding antiretroviral changes in HIV+ drug-experienced patients.

DESIGN

A two factorial (genotyping and expert advice), randomized, open label, multi-center trial. The patients were stratified according to the number of treatment failures.

PATIENTS AND METHODS

HIV-1 infected patients on stable antiretroviral therapy who presented virological failure were included into the study. Genotypic testing was performed by using TrueGene HIV Genotyping kit and the results were interpreted by a software package (RetroGram, version 1.0). An expert advisory committee suggested the new therapeutic approach based on clinical information alone or on clinical information plus HIV-1 genotyping results. Plasma HIV-1 RNA load, CD4+ cell count and adverse events were recorded at baseline and every 12 weeks.

RESULTS

A total of 326 patients were included. The baseline CD4+ cell count and plasma HIV-1 RNA were 387 (+/- 224) x 10(6) cells/l and 4 (+/- 1) log(10) respectively. The proportion of patients with plasma HIV-1 RNA < 400 copies/ml at 24 weeks differed between genotyping and no genotyping arms (48.5 and 36.2%, P < 0.05). Factors associated with a higher probability of plasma HIV-1 RNA < 400 copies/ml were HIV-1 genotyping [odds ratio (OR), 1.7; 95% confidence interval (CI), 1.1-2.8; P = 0.016] and the expert advice in patients failing to a second-line antiretroviral therapy (OR, 3.2; 95% CI, 1.2-8.3; P = 0.016).

CONCLUSIONS

HIV-1 genotyping interpreted by a software package improves the virological outcome when it is added to the clinical information as a basis for decisions on changing antiretroviral therapy. The expert advice also showed virologic benefit in the second failure group.

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.

HIV disease and advanced age: an increasing therapeutic challenge

The mean age of patients at both first HIV detection and AIDS diagnosis is progressively rising over time. However, reliable epidemiological estimates, clinical data or controlled therapeutic and outcome figures are lacking for elderly patients, especially with regard to laboratory and clinical response to antiretroviral therapy, treatment tolerability, drug-drug interactions, short- and long-term toxicity, and interactions with underlying illnesses and concurrent pharmacological treatment. In fact, the large majority of randomised, controlled trials evaluating and comparing new antiretroviral drugs or anti-HIV therapeutic strategies, as well as antimicrobial treatment or chemoprophylaxis of HIV-related complications, either excluded patients with advanced age and/or concurrent disorders or did not offer substudies or detailed data analysis focusing on older patients compared with younger ones. The life expectancy of HIV-infected persons receiving highly active antiretroviral therapy (HAART) is now extended (approaching that of the general population), so that the definition of AIDS has lost its epidemiological and clinical significance thanks to the immune reconstitution resulting from potent antiretroviral therapy. However, an ever-increasing number of individuals aged > or =50 years with HIV infection is expected in the coming years, as a result of both increased survival of patients with treated disease and delayed recognition of individuals with occult HIV disease. The limited data available about combined antiretroviral therapy in the elderly seem to show an overlapping virological success rate but a slower and blunted immune recovery compared with younger patients. Thymic output, however, seems somewhat preserved even in adulthood and may contribute to the reconstitution of most of the quantitative and functional T cell abnormalities caused by HIV disease. More attention must be paid to underlying end-organ disorders, as well as expected pharmacological interactions and combined drug toxicity that may interfere with HAART efficacy and patients' compliance with recommended regimens and could lead to increased adverse effects. The available guidelines for antiretroviral treatment and therapy and prophylaxis of AIDS-related illnesses should be regularly updated and should include problems related to HIV disease in an aging population. Specific trials or substudies focusing on older people are warranted to obtain controlled data on all issues of antiretroviral therapy in the elderly, including time and mode of initiation, and modification and salvage HAART regimens. Antiretroviral drug dosage adjustment to take into account underlying pathological conditions or other pharmacological treatments is another emerging issue.

Response to Antiretroviral Therapy among Patients Exposed to Three Classes of Antiretrovirals: Results from the Eurosida Study

There is an increasing proportion of HIV-positive patients exposed to all licensed classes of antiretrovirals, and the response to salvage regimens may be poor. Among over 8500 patients in EuroSIDA, the proportion of treated patients exposed to nucleosides, protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitor (NNRTI) increased from 0% in 1996 to 47% in 2001. Four-hundred-and-thirteen patients, who had failed virologically two highly active antiretroviral therapy (HAART) regimens and experienced all three main drug classes, started a salvage regimen of at least three drugs, in which at least one new PI or NNRTI was included. Median viral load was 4.7 log copies/ml [Interquartile range (IQR) 4.2–5.2], CD4 lymphocyte count 150/mm3 (IQR 60–274/mm3) and follow-up 14 months. Of these patients, 283 (69%) subsequently experienced at least a 1 log decline in viral load and 202 (49%) achieved a viral load <500 copies/ml. Conversely, the CD4 count halved from the baseline value in 88 (21%), and 45 (11%) experienced a new AIDS-defining disease. In multivariable analyses, a 1 log viral load reduction was related to baseline viral load [relative hazard (RH) 1.27 per 1 log higher; P=0.008], a previous viral load of less than 500 copies/ml (RH 1.69; P=0.002), more recent initiation of the regimen (RH 1.36 per year more recent; P=0.02), number of new drugs in the regimen (RH 1.20 per drug; P=0.02), time since start of antiretroviral therapy (RH 0.94 per extra year; P=0.035) and time spent on HAART with viral load >1000 copies/ml (RH 0.96 per extra month; P=0.0001). Analysis of factors associated with CD4 count decline and new AIDS disease also indicated improved outcomes in more recent times and a tendency for a better response in those starting more new drugs, but no relationship with the total number of drugs. Outcomes in people starting salvage regimens appear to depend on the number of new drugs started but not on the total number of drugs being used.

Antiretroviral drug resistance testing in patients with HIV-1 infection: a meta-analysis study

BACKGROUND

HIV-1 resistance tests, both phenotype and genotype, have been entering clinical practice during the last years, but limited prospective studies have been reported in antiretroviral-treated patients with virological failure.

PURPOSE

A meta-analysis of randomized controlled trials (RCTs) published or presented at the most important international conferences until February 2001 was performed to estimate the impact of resistance-guided antiretroviral therapy on virological outcome.

METHOD

A search for RCTs was performed by using a MEDLINE database, Internet sources, and international conference presentations and was updated September 2001. All RCTs available, including four RCTs on genotype resistance testing, one RCT on phenotype resistance testing, and one RCT on genotypic and phenotypic testing, were analyzed. The rate of patients with undetectable viremia at 3 months was reported in all RCTs and the rate at 6 months was reported in 4 of 6 RCTs.

RESULTS

The rate of patients with undetectable viral load after 3 months was 42.6% in patients who were treated based on genotype results and was 33.2% in patients who were treated based on standard of care (SOC; odds ratio [OR] 1.7; 95% CI: 1.3-2.2). At 6 months, undetectable viremia was observed in 38.8% and 28.7% of the patients, respectively (OR: 1.6; 95% CI: 1.2-2.2). In 142 patients, expert advice was provided to optimize clinical use of genotypic data. The higher rate of viral suppression was achieved in this subgroup of patients (50.7% vs. SOC 35.8%; OR 2.4; 95% CI 1.5-3.7). In contrast, undetectable viremia was achieved in 37.5% patients who were treated based on phenotype results versus 33.8% patients who were treated based on SOC (OR 1.1; 95% CI 0.8-1.6).

CONCLUSION

These results support the use of a genotypic test in patients experiencing virological failure during antiretroviral treatment. Expert interpretation of the test may increase the probability of virological response.

HIV drug resistance and implications for the introduction of antiretroviral therapy in resource-poor countries

The development and transmission of HIV drug-resistant viruses is of serious concern and has been shown to significantly diminish the effectiveness of antiretroviral therapy. In addition, cross-resistance between drugs of the same class can seriously limit therapeutic options and may potentially be most problematic in resource-poor settings where new drugs are not widely available. Strategies based on avoidance of virological failure are therefore essential for the long-term success of therapy. In this regard, regionally adapted programs to facilitate proper adherence with therapy need to be urgently implemented, concomitant with expanded access to new antiretroviral drugs. The value of genotypic resistance testing as a prognostic tool to help guide therapeutic decisions has been established. However, the relatively high cost of this novel technology does not warrant its routine utilization at this time in resource-poor countries. Lastly, the genetic barrier of the antiretroviral agents that are prescribed is also an important consideration that needs to be integrated with knowledge of HIV-1 subtypes, drug pharmacology, and medical management of concurrent illnesses. The selection of appropriate first-line antiretroviral combination regimens may be an even more important consideration in developing than developed countries, given that options in the aftermath of treatment failure may be more limited in such settings.

Impact of HIV type 1 drug resistance mutations and phenotypic resistance profile on virologic response to salvage therapy

This study examines the association between presence of drug resistance mutations and phenotypic resistance at baseline to virologic response to salvage therapy in a community setting. The study population consisted of 58 antiretroviral drug-experienced patients with HIV-1 infection who had recently switched therapy because of virologic failure. Drug resistance mutations in the reverse transcriptase- and protease-coding regions and phenotypic susceptibility to 13 antiretroviral drugs were assessed at baseline. Plasma HIV-1 RNA levels were assessed at baseline and at subsequent clinic visits. Results showed that three variables were significant in predicting virologic response: HIV-1 levels at baseline, number of protease mutations, and phenotypic sensitivity score for the regimen at baseline. For four drugs there was a significant association between the presence of specific drug resistance mutations and >10-fold phenotypic resistance to that drug. With phenotypic resistance defined as >4-fold resistance, the association between specific drug resistance mutations and phenotypic resistance was significant for seven drugs. Overall, these data show that phenotypic susceptibility and absence of drug resistance mutations, particularly protease mutations, are significant predictors of virologic response. For several drugs, specific combinations of drug resistance mutations are associated with decreased phenotypic susceptibility and might provide useful clinical guidelines in selecting therapeutic options.

Comparison of capillary electrophoresis sequencing with the new CEQ 2000 DNA Analysis System to conventional gel based systems for HIV drug resistance analysis

To date the majority of sequencing technologies have been based on use of gel plates. In this study sequencing by capillary electrophoresis for HIV-1 genotyping on the CEQ 2000 sequencer (Beckman Coulter Inc.) has been investigated and compared to an 'in house' protocol on the Prism-377 sequencer (Applied Biosystems) and to the HIV-1 TruGene kit (Visible Genetics Inc.), two gel plate-based systems. Plasma from 20 HAART-treated patients with virological failure were analyzed for protease (PR) and reverse transcriptase (RT) genes. A total of 520 RT codons (26/patient) and 360 PR codons (18/patient) related to antiretroviral drug resistance were evaluated. The overall agreement between CEQ 2000 and Prism-377 results was 100% for the RT and PR primary and secondary mutations. The overall agreement between CEQ 2000 and TruGene was 100% for primary and > or =97% for secondary mutations. Discrepant results would have never led to errors in genotype interpretation. Performances for a 24 patients/week/one technician genotyping throughput were analyzed. For Prism-377, TruGene and CEQ 2000, manual processing required 5, 4 and 2,5 days, sequence data analysis needed additional 3, 1 and 2 days and cost/patient was approximately 49, 214 and 39 $, respectively. The CEQ 2000 sequencer offers a reliable alternative for fast and cost effective HIV drug resistance analysis.

Extent of human immunodeficiency virus type 1 drug resistance as a predictor of virological failure after genotype-guided treatment switch

Little is known about factors involved in virological response to treatment changes guided by genotyping in patients whose highly active antiretroviral therapy (HAART) fails. A 12-month observational study was conducted of 45 patients infected with human immunodeficiency virus (HIV)-1, who underwent a new genotype-guided HAART regimen following virological treatment failure. Logistic regression models were used to define factors predictive of virological response to genotype-assisted treatment switches. Virological response was defined as achievement of a level of plasma HIV-1 RNA <1000 copies/mL at the end of the follow-up. Drug-resistance mutations were detected at baseline in 30 patients (66.7%). A sustained virological response to new treatment occurred in 13 (43.3%) of these, as opposed to 11 (73.3%) of the 15 patients harboring drug-susceptible virus at baseline (P=.07). In multivariate logistic regression analysis, the number of drug classes where there was resistance at baseline was the only independent predictor of virological failure (P=.0313). Lack of virological response to genotype-guided treatment changes is primarily due to complex baseline resistance patterns. Benefits of antiretroviral resistance testing may be seriously limited by the lack of subsequent treatment options for heavily pretreated patients.

Randomized salvage therapy with saquinavir-ritonavir versus saquinavir-nelfinavir for highly protease inhibitor-experienced HIV-infected patients

PURPOSE

To compare saquinavir + ritonavir and saquinavir + nelfinavir with nucleoside recycling in patients with multiple failures of highly active antiretroviral therapy (HAART).

METHOD

This was a prospective, multicenter, randomized open trial. Inclusion criteria were the following: consent, age > 18, previous protease inhibitor (PI) exposure > 6 months, unchanged HAART > 3 months, and viral load > 3 log. The treatments compared were ritonavir 200 mg bid + saquinavir 600 mg bid (Rito-Saq), and nelfinavir 1,000 mg bid + saquinavir 600 mg bid (Nelf-Saq). Nucleoside analogues were recycled, and nonnucleoside inhibitors were not permitted. Trough levels of the three drugs were measured by high-performance liquid chromatography at the month 3 visit. After the study had been completed, genotyping analysis was done on the first serum at entry.

RESULTS

The study was interrupted due to the availability of new anti-HIV drugs. A random sample of 31 (16 Rito-Saq and 15 Nelf-Saq) patients was divided into two groups, which were comparable in terms of demographic data and previous history of HIV infection. Mean CD4 cell count and plasma viral load (pVL) were 316 +/- 169 and 3.89 +/- 0.87 for Rito-Saq and 448 +/- 238 and 3.85 +/- 0.32 for Nelf-Saq. Previous duration of PI exposure was 31 months for both groups. The mean number of protease gene mutations was 3.8 (range, 2-7) and 4.4 (range, 2-9), respectively. On intention-to-treat (ITT) analysis at month 6, pVL stabilization or decrease >/= 0.5 log was observed in 18 patients (58%): 10 for Rito-Saq and 8 for Nelf-Saq. In a multivariate logistic regression analysis, virological success at month 3 was inversely correlated to baseline viral load (R = 0.14; 95% CI 0.03-2.9; p =.01); and at month 6, virological success was inversely associated to the number of mutations in the protease gene (R = 2.2; 95% CI 0.73-6.53; p =.06).

CONCLUSION

Nelf-Saq and Rito-Saq combinations can be proposed in case of multiple HAART failures. The fact that the virological response was inversely correlated to baseline viral load makes the case for an early switch after a HAART failure.

Human immunodeficiency virus type 1 drug resistance testing: a comparison of three sequence-based methods

The use of genotypic assays for determining drug resistance in human immunodeficiency virus (HIV) type 1 (HIV-1)-infected patients is increasing. These tests lack standardization and validation. The aim of this study was to evaluate several tests used for the determination of HIV-1 drug resistance. Two genotypic tests, the Visible Genetics TruGene HIV-1 Genotyping Kit and the Applied Biosystems HIV Genotyping System, were compared using 22 clinical samples. Genotyping results were also obtained from an independent reference laboratory. The Visible Genetics and Applied Biosystems genotyping tests identified similar mutations when differences in the drug databases and reference strains were taken into account, and 19 of 21 samples were equivalent. The concordance between the two assays was 99% (249 of 252 mutation sites). Mutations identified by the reference laboratory varied the most among those identified by the three genotypic tests, possibly because of differences in the databases. The concordance of the reference laboratory results with the results of the other two assays was 80% (201 of 252). Samples with 500 to 750 HIV RNA copies/ml could be sequenced by the Visible Genetics and Applied Biosystems assays using 1 ml of input. The Visible Genetics and Applied Biosystems assays both generated an accurate sequence. However, the throughput of the Visible Genetics assay is more limited and may require additional instruments. The two assays differ technically but are similar in overall complexity. Data analysis in the two assays is straightforward, but only the reports provided by Visible Genetics contain information relating mutations to drug resistance. HIV drug resistance genotyping by sequencing is a complex technology which presents a challenge for analysis, interpretation, and reporting.

Pharmacokinetics and resistance mutations affect virologic response to ritonavir/saquinavir-containing regimens

The authors assessed the impact of protease and reverse transcription (RT) mutations and individual pharmacokinetic parameters on virologic response to a four-drug regimen including ritonavir/saquinavir. Treatment was given at the start of the study (M0) to 22 HIV-1 protease inhibitor-naive or pretreated patients. Protease and RT genes were sequenced at M0, at the time of virologic failure, or at the end of the follow-up. Plasma ritonavir and saquinavir peak C(max), C(min), and area under the curve (AUC) were determined based on samples taken 0, 1, 2, 3, 4, 6, 8, and 12 hours after administration. HIV-1 RNA decreased to less than 50 copies/mL in 11 patients (group 1). At M0, five of them had no RT mutation and 10 had three or fewer secondary protease mutations with no new mutation during follow-up. Ritonavir and saquinavir pharmacokinetics showed wide interindividual variability. Treatment failed in 11 patients (group 2): 9 had three to eight protease mutations and a mean of 5.8 RT mutations at M0, with emergence of new mutations during follow-up. Pharmacokinetics was similar to those of group 1. The other two patients with virologic failure showed no baseline primary mutation but were the only patients with insufficient saquinavir and ritonavir AUC. The authors showed the complementarity between drug-resistance genotype and individual pharmacokinetics and the potential utility of AUC and Cmax to manage treatment.

Identification of key mutations in HIV reverse transcriptase gene can influence the clinical outcome of HAART

Therapeutic failures due to in vivo loss of drug sensitivity are still a major problem in AIDS care. Currently, the role of and methods for detecting resistant mutant strains in patients before therapeutic choices are still under debate. To investigate the relevance of screening for key mutations alone the commercial INNO-LiPA HIV-1 RT method was applied retrospectively to analyzing several HIV codons correlated with resistance to RTI (reverse-transcriptase inhibitors) in sera from 62 patients before starting HAART protocols, selected on the basis of clinical parameters. INNO-LiPA detected several resistant mutant strains, which were strictly consistent with previous selective pressure in the patients. A significant correlation between genotype pattern and response to HAART was found. The presence of key mutations associated with resistance to one or two RTI included in the protocol correlated with a decrease in treatment benefits, whereas patients with wild-type or non-resistant viral strains exhibited better response to HAART. Even if this information had been available when treatment was started, 45 of the patients would not have received different treatment. When compared with the total number of patients, the subgroup receiving a treatment that was considered retrospectively as consistent with the key mutation pattern exhibited a significantly better outcome. Although the interpretation of resistance-related key mutations needs improvement, this surrogate LiPA method seems to maintain a predictive role in the management of HIV infection, and is less expensive.

Prevalence of the T215Y mutation in human immunodeficiency virus type 1-infected pregnant women in a New York cohort, 1995--1999

From 1997 through 1999, the prevalence of the zidovudine resistance mutation T215Y was 9.7% among pregnant women, and the human immunodeficiency virus type 1 (HIV-1) load in those with resistant virus was higher than that measured in women with wild-type HIV-1. All mutations were noted in women with zidovudine experience, which suggests that monotherapy may not be adequate prophylaxis for vertical transmission of HIV-1 infection in the current era.

Limits of deep salvage antiretroviral therapy with nelfinavir plus either efavirenz or nevirapine, in highly pre-treated patients with HIV disease

The virological and immunological response to an efavirenz-containing rescue regimen was compared with that of a nevirapine-containing one in a prospective, open-label 12-month study performed in patients previously treated with > or = 12 months of nucleoside analogue monotherapy, and > or = 15 months of indinavir- or ritonavir-containing HAART. Pooled laboratory data were assessed according to change or continuation of nucleoside analogues, at the time of start of salvage treatment. An improvement of markers of HIV disease progression occurred in all 59 evaluable patients (with a higher viral load decrease in the efavirenz over the nevirapine group at the third month), but the virological response was neither complete nor sustained at the end of study, irrespective of efavirenz or nevirapine adjunct, and complete viral suppression was attained in only 16.9% of subjects. A progressively increasing mean CD4+ lymphocyte count characterized the immunological response of all patients. The 35 patients who changed at least one nucleoside analogue when introducing salvage therapy had a better outcome, irrespective of the non-nucleoside reverse transcriptase inhibitor chosen. Rescue strategies are increasingly needed in HIV-infected patients treated for a long time with HAART. The association of nelfinavir, a non-nucleoside reverse transcriptase inhibitor, and dual nucleoside analogues, is popular among patients who fail first-line HAART. When prolonged prior treatment with nucleoside analogue monotherapy and HAART are of concern, and a quite elevated viral load is present, this salvage regimen may not allow a complete and sustained virological response in a 1-year period, while a more favourable immunological recovery can be expected. However, the concurrent change of nucleoside analogues significantly improves treatment outcome.

Combination therapy with indinavir, ritonavir, and delavirdine and nucleoside reverse transcriptase inhibitors in patients with HIV/AIDS who have failed multiple antiretroviral combinations

PURPOSE

Ritonavir (RTV) and delavirdine (DLV) are inhibitors of cytochrome P450 (CYP) 3A4, the specific CYP that metabolizes indinavir (IDV). We hypothesized that patients who have failed multiple therapies containing protease inhibitors would still respond to IDV if high plasma concentrations were achieved. We retrospectively examined the antiviral efficacy of the combination of RTV, DLV, and IDV in heavily antiretroviral-experienced patients.

METHOD

A chart review of patients treated with IDV/RTV/DLV and two nucleoside reverse transcriptase inhibitor (NRTI) drugs was performed. Only patients who failed at least three highly active antiretroviral therapy (HAART) regimens and remained on IDV/RTV/DLV therapy for at least 2 months were included. Plasma concentrations for IDV and RTV were obtained if patients were still on therapy.

RESULTS

Ten participants were identified who qualified for this study. The median plasma HIV RNA prior to initiating IDV/RTV/DLV was 359,300 copies/mL. Nine of the 10 patients had failed nonnucleoside reverse transcriptase inhibitor (NNRTI)-containing regimens in the past. Eight out of 10 patients had at reduction in HIV RNA. Four of eight patients maintained the 1 log(10) reduction in HIV RNA past 6 months. Mean CD4 cell count increased from 142+/-99 to 273+/-126 cells/mm(3). Genotypic data available on six patients showed multiple protease gene mutations. Plasma concentration of IDV in three patients (two troughs and one 7 hours postdose) were >1,000 ng/mL.

CONCLUSION

Our data suggests that in heavily antiretroviral drug-treated patients, partial antiretroviral response to RTV/IDV/DLV can still be achieved. The use of IDV/RTV/DLV and two NRTIs as salvage therapy has merit in patients who have no viable treatment options. A prospective trial utilizing this drug combination is warranted.