A randomized study of antiretroviral management based on plasma genotypic antiretroviral resistance testing in patients failing therapy. CPCRA 046 Study Team for the Terry Beirn Community Programs for Clinical Research on AIDS

Managing failure to antiretroviral drugs in HIV-1-infected patients

Managing failure to antiretroviral therapies implies the addressing of several issues: the clinical stage, the virological and the immunological response to the failing regimen, together with drug history, resistance and exposure. Each of these issues will be discussed with the aim of providing useful data to design an optimal rescue antiretroviral therapy.

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

PURPOSE

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

METHOD

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

RESULTS

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

CONCLUSION

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

Limited evolution of HIV antiretroviral drug resistance-associated mutations during the performance of drug resistance testing

We investigated the evolution of HIV reverse transcriptase (RT)- and protease-associated antiretroviral (ARV) drug resistance mutations during the time taken to perform genotypic drug resistance testing. Thirty treatment-experienced patients who were adherent to therapy and who underwent genotypic drug resistance testing provided blood samples at randomization and when reviewing the test results (baseline). Patients remained on their existing therapy between randomization and baseline. The predominant HIV strains in 10 patients (33%) either lost and/or gained primary RT inhibitor (RTI)- or protease inhibitor (PI)-associated resistance mutations during the testing period. Of the 9 patients with RT mutations, 2 lost, 5 gained, and 2 both lost and gained RTI resistance mutations. One patient gained a significant PI-associated resistance mutation on an existing PI-resistant background. The evolution that occurred in the RT may have altered the effectiveness of subsequent ARV therapy in some patients. Neither viral load at randomization, ARV drug class used at randomization, time between collection of blood samples, duration of current therapy, nor number of ARV drugs used influenced gain or loss of resistance mutations. There was a significant association between duration of previous ARV therapy and gain of RTI-associated resistance mutations ( p =.02), however. In general, our results suggest that patients should continue current therapy until test results are available. A few patients would be expected to gain ARV drug-associated resistance mutations during this time, however.

Evaluation of the LiPA HIV-1 RT assay version 1: comparison of sequence and hybridization based genotyping systems

BACKGROUND

Specific mutations in the reverse transcriptase (RT) gene of HIV-1 are associated with reduced activity of nucleoside inhibitors used in the antiretroviral treatment of infected patients. The appearance of these mutations may result in therapy failure. Therefore, HIV-1 genotyping is an important tool for monitoring antiretroviral therapy. At present different assay systems are used to obtain information about the changes in the viral genome.

OBJECTIVE

The aim of this study was to evaluate the LiPA HIV-1 RT assay version 1 for monitoring drug resistance mutations in comparison to full-length sequencing.

STUDY DESIGN

Two hundred and forty-four samples were analyzed using the LiPA HIV-1 RT assay version 1 and were compared with full RT gene sequences obtained by in-house sequencing.

RESULTS

In 129/244 (52.9%) samples full concordance between both systems was found, in 86/244 (35.2%) samples at least one position was not detected by the LiPA assay, in 19/244 (7.8%) samples the results were contradictory, and in 10/244 (4.1%) contradictory as well as absent signals from the LiPA assay were found. Analyzing total codons, missing signals were observed at 137 codons, mainly found at positions 41 (40/137) and 215 (41/137). The 32 contradictions between LiPA and sequencing were equally distributed across all codons except for position 184 with only one case. The main reason for missing signals is the heterogeneity of the HIV genome, which could not be fully covered by the LiPA probes, e.g. unusual mutations or polymorphisms in the vicinity of the relevant positions. The same is the case for some contradictions, although most of them are not evident (19/32 positions).

CONCLUSIONS

We analyzed a patient population with partly multiple therapy failures. The LiPA HIV-1 RT assay version 1 gives a high degree of samples with at least one missing signal (39.4%) in our cohort and this is not acceptable for a diagnostic tool. However, the LiPA assay might work better in untreated patients and could, therefore, still be used for screening.

Phenotypic and genotypic HIV-1 drug resistance assays provide complementary information

To determine the extent to which genotype (GT) or phenotype (PT) methods provide HIV-1 drug resistance information that is overlapping or complementary, both tests were performed on 1378 patient plasma samples. Discordance, defined as determination of reduced susceptibility measured by PT but sensitivity by GT (PT-R/GT-S), or vice versa (PT-S/GT-R), was common: 83, 62, 43, and 28% of samples with evidence of drug resistance had at least 1, 2, 3, or 4 drugs discordant, respectively. Three types of discordance were observed: PT-R/GT-S, and PT-S/GT-R with or without the presence of mixtures at resistance-associated positions (25%, 34%, and 41% of all discordance, respectively). After accounting for mixtures, results for didanosine (30%), zalcitabine (18%), tenofovir (17%), abacavir (14%), lamivudine (12%), and amprenavir (11%) were discordant in >or= 10% of samples. PT-S/GT-R results were most common for didanosine and zalcitabine, whereas PT-R/GT-S results were most common for lamivudine and amprenavir. PT provided quantitative assessment of the degree of reduced susceptibility and identified reduced susceptibility (PT-R/GT-S) or normal susceptibility (PT-S/GT-R) that was not recognized by the GT interpretation algorithm. GT provided valuable information when mixtures were present and minor populations of drug resistant virus were not detected by phenotyping (PT-S/GT-R results). This demonstrates the complementary nature of information provided by PT and GT tests and suggests that their combined use can provide additional clinically-relevant information.

Antivirals against HIV-1

Morbidity and mortality associated with HIV infection increased rapidly following the recognition of this syndrome in 1981, and by 1994, AIDS was the leading cause of death in the United States among men and women ages 15-45. The antiretroviral therapy era began in 1987 following the Food and Drug Administration approval of zidovudine, a nucleoside analog reverse transcriptase inhibitor; however, it was not until 1996, when HIV viral load assays were developed that could quantify the copy number of HIV RNA present in plasma, that investigators and clinicians could appropriately evaluate the antiviral efficacy of therapy. This important technical breakthrough and the availability of HIV protease inhibitors led to a dramatic decline in the morbidity and mortality associated with the disease.

Pediatric HIV infection and treatment

Knowledge regarding the basic mechanisms of pediatric HIV infection and its prevention and treatment has expanded greatly in the last decade. Significant questions remain and have been largely refocused to the complexities of a chronic disease process. Management invariably requires specialists who must keep abreast of a rapidly evolving information base.

HIV-1 genotypic and phenotypic resistance

Antiretroviral failure caused by the development of drug resistance in HIV-1 is an increasingly common clinical problem. Two types of resistance assays are available to clinicians. Genotypic assays determine the presence of mutations associated with drug resistance. The interpretation of mutations is often complicated, however, and may require expert opinion. Phenotypic assays provide a direct measure of the drug susceptibility of the virus. The magnitude of increase, however, in viral drug inhibitory concentration that is predictive of clinical drug failure remains unknown for several antiretroviral drugs. The mutational patterns underlying resistance to each antiretroviral drug are often diverse, and cross-resistance patterns within each of the currently available classes are complex. Currently, resistance testing is recommended for patients who have virologic failure on an antiretroviral regimen. Furthermore, testing should also be considered in treatment-native patients when the prevalence of transmitted drug-resistant virus is expected to be high.

Treatment for primary HIV infection: projecting outcomes of immediate, interrupted, or delayed therapy

With limited data available on the optimal treatment of primary HIV infection, disease modeling can be used to project clinical outcomes and inform decision makers. The authors developed a simulation model to evaluate the clinical outcomes and life expectancy projections for three primary HIV infection treatment strategies: 1) continuous antiretroviral therapy (ART) initiated at CD4 count <350 cells/mm(3); 2) continuous ART initiated immediately on diagnosis of primary HIV infection; and 3) ART initiated on diagnosis followed by structured treatment interruption. Projected life expectancies for the three strategies were 23.92, 24.46, and 26.07 years, respectively. The impact of key variables was assessed in sensitivity analysis, with the structured treatment interruption strategy remaining the most effective over a broad range of inputs. The immunologic benefit associated with immediate therapy and the potential for antiretroviral resistance due to structured treatment interruption have the most important impact on the optimal strategy. Based on current data, immediate treatment on diagnosis of primary HIV infection followed by structured treatment interruption will likely yield the best outcome. These results can assist decision makers and those planning clinical trials in defining evidence-based performance measures for primary HIV infection treatment and future trials.

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.

Early adoption of HIV-1 resistance testing in the San Diego County Ryan White CARE Act Program: predictors and outcome

This research identifies predictors and outcomes of early use of human immunodeficiency virus type 1 (HIV-1) resistance testing in the San Diego County Ryan White CARE Act program. Between January and November 2000, 98 patients receiving care in 7 clinics participated in the resistance testing program. Provider characteristics predictive of participation included number of patients and percent of practice devoted to HIV care and number of HIV-related continuing medical education hours over the preceding 12 months. Providers rarely requested expert panel review of test results, and expert review was not predictive of better viral load responses. Regimens specified before knowledge of resistance results had more active drugs than those prescribed after knowledge of test results. Phenotypic susceptibility was predictive of virologic response, as was degree of prior nucleoside analogue exposure. There was little relationship between phenotypic susceptibility and a clinician's decision to prescribe a drug. Early adopters of this technology were more experienced HIV providers than their colleagues and utilized susceptibility information using reasoning processes in which resistance was a contributory but not necessarily dominating factor.

Longitudinal use of phenotypic resistance testing to HIV-1 protease inhibitors in patients developing HAART failure

An "in-house" recombinant virus protease inhibitor susceptibility assay was carried out (median of 3 per patient) retrospectively in 26 patients failing HIV protease inhibitor based therapy at regular intervals to the initiation of the first protease inhibitor. Patients were treated with either indinavir (N = 6), ritonavir (N = 10), or saquinavir (N = 10) and two nucleoside analogues. Second line therapy was based on single or dual protease inhibitor regimens occasionally containing nelfinavir. Clinically relevant resistance cut-offs associated with a poorer virological outcome from 6 months on and the clinical outcome from 3 months on were determined tentatively as 4- to 8-fold resistance for indinavir and ritonavir and 2.5- to 8-fold to saquinavir. In addition, the degree of cross-resistance at the time of the change of protease inhibitor was associated with the response in viral load at 6 months to the second line therapy (P = 0.018). Cross-resistance (> or = 8-fold) between ritonavir and indinavir was common (78 and 100%). Cross-resistance between indinavir or ritonavir and saquinavir was less frequent (75 and 60% respectively) than the opposite (100%, P = 0.004). Cross-resistance to nelfinavir was encountered more frequently (> 70%) than to amprenavir (9%). The magnitudes of resistance were correlated between each other. In summary, the protease inhibitor susceptibility carried out longitudinally appears to be an earlier prognostic marker than viral load in a context of cross-resistance. The magnitude of resistance, as a marker of cross-resistance, should be useful to guide second line therapy.

Response to changes in antiretroviral therapy after genotyping in human immunodeficiency virus-infected children

BACKGROUND

HIV genotyping has been beneficial when choosing salvage regimens in adults failing highly active antiretroviral therapy (HAART). Our objectives were to evaluate the usefulness of genotyping in HIVinfected children failing HAART and to determine whether the presence of resistance mutations was associated with previous antiretroviral therapy.

METHODS

We followed the progress of pediatric patients who had HIV genotyping performed after HAART failure. Charts were reviewed at 3-month intervals for 1 year after genotyping for changes in viral load and CD4+ cell percentage. Patients whose antiretroviral therapy was changed after genotyping were compared with those whose medications were not changed. We also compared the proportion of patients with genotypic mutations according to antiretroviral exposure at time of genotyping.

RESULTS

Eighteen pediatric patients were eligible for inclusion. None of 10 patients who had antiretroviral therapy changed after genotyping had a decrease in viral load atmonths after genotyping. One of 8 patients who had no changes in antiretroviral therapy had a sustained decrease in viral load at 12 months. Two-thirds of patients had resistance mutations to antiretrovirals without prior exposure to that drug.

CONCLUSIONS

This study did not demonstrate substantial clinical benefit to HIV genotyping in antiretroviral agent-experienced pediatric patients with high viral loads. These results contrast with favorable short term clinical and virologic responses to therapeutic changes after genotyping in HIV-infected adults. However, medication history alone does not appear to be an adequate alternative to genotyping in choosing salvage regimens in antiretroviral agent-experienced children.

Longitudinal use of a line probe assay for human immunodeficiency virus type 1 protease predicts phenotypic resistance and clinical progression in patients failing highly active antiretroviral therapy

An observational study assessed the longitudinal use of a new line probe assay for the detection of protease mutations. Probe assays for detection of reverse transcriptase (Inno-LiPA HIV-1 RT; Innogenetics) and protease (prototype kit Inno-LiPA HIV Protease; Innogenetics) mutations gave results for 177 of 199 sequential samples collected over 2 years from 26 patients failing two nucleoside reverse transcriptase inhibitors and one protease inhibitor (first line: indinavir, n = 6; ritonavir, n = 10; and saquinavir, n = 10). Results were compared to recombinant virus protease inhibitor susceptibility data (n = 87) and to clinical and virological data. Combinations of protease mutations (M46I, G48V, I54V, V82A or -F, I84V, and L90M) predicted phenotypic resistance to the protease inhibitor and to nelfinavir. The sum of protease mutations was associated with virological and clinical outcomes from 6 and 3 months on, respectively. Moreover, a poorer clinical outcome was linked to the sum of reverse transcriptase mutations. In conclusion, despite the limited number of patients studied and the restricted number of codons investigated, probe assay-based genotyping correlates with phenotypic drug resistance and predicts new Centers for Disease Control and Prevention stage B and C clinical events and virological outcome. Line probe assays provide additional prognostic information and should be prospectively investigated for their potential for treatment monitoring.

Management of HIV-infected Patients with Multidrug-resistant Virus

Heavily pretreated HIV-infected patients with multidrug-resistant virus remain a clinical challenge to the treating physician. While the goal of therapy in such patients is still controversial, sustained immunologic and clinical benefit have only been demonstrated with complete suppression of plasma viral load below detectable levels. Expert use of resistance testing may help in the selection of the salvage regimen, and monitoring of plasma drug levels may help optimize the potency and tolerability, especially of complex, multiple drug regimens where adherence remains a critical determinant of treatment outcome. The potential roles of newer agents, adjuvants, treatment interruptions, and immune-based therapies remain under investigation.

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

OBJECTIVE

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

RESULTS

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

CONCLUSIONS

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

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.

Both baseline HIV-1 drug resistance and antiretroviral drug levels are associated with short-term virologic responses to salvage therapy

BACKGROUND

To determine the impact of HIV-1 drug resistance at baseline and antiretroviral drug levels (DL) during follow-up on virologic response to the next antiretroviral regimen.

METHODS

Baseline genotypic and phenotypic susceptibility was obtained for plasma virus from patients failing a protease inhibitor-containing regimen. Untimed plasma antiretroviral DL were performed and the distribution of DL after 12 weeks of follow-up was classified as above (DLHigh) or below (DLLow) the median. Inhibitory quotients [IQ = (DL at week 12)/(fold change in IC50 to wild-type)] were determined for each drug in the regimen. Primary outcome was change in log10 plasma HIV-1 RNA viral load (DeltaVL) from baseline to 12 weeks.

RESULTS

There were 137 patients who had baseline resistance data available for the antiretroviral drugs used in the salvage regimen, and DL at week 12. Each drug with DLHigh was associated with DeltaVL = -0.40 (P = 0.0002) while each drug with DLLow had DeltaVL = -0.16 (P = 0.11). In multivariate models DeltaVL associated with each active drug (defined by genotype) with DLHigh was -0.48 log10 (P < 0.0001), and with each active drug with DLLow was -0.22 (P = 0.03). The DeltaVL was -0.18 if no drugs in the regimen had an IQ > median, compared to -0.58 for one drug, -1.06 for two drugs, -0.86 for three drugs, and -1.44 for four or five drugs with IQ > median (P < 0.0001 for trend).

CONCLUSIONS

In salvage therapy, both the number of active drugs and the DL for each drug in the new regimen determine the antiviral response.

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.

Reverse transcriptase mutations in HIV-1 infected patients treated with two nucleoside analogues: the SMART study

Resistance to nucleoside reverse transcriptase inhibitors (NRTIs) was studied in 527 HIV-1-infected patients, 342 responder and 185 non-responder to two NRTIs. Responders were followed for one year to assess the incidence of clinical failure. The prevalence of the 215Y/F substitution was higher among non-responder, compared to responder patients (33.7&amp;#x0025 vs. 17&amp;#x0025, P = 0.0005), whereas the prevalence of the 184V and of the 70R mutations was comparable between these two groups. The 74V substitution was never observed and the 75T mutation was detected in only two subjects non-responder to a stavudine including regimen. Reduced susceptibility to didanosine or stavudine was infrequent. Reduced susceptibility to zidovudine was observed in 25&amp;#x0025 of individuals failing a zidovudine including regimen, whereas reduced susceptibility to lamivudine was detected in all subjects failing a lamivudine including regimen. In the prospective analysis, patients with undetectable viral load at enrollment had a lower incidence of failure rate over one year compared to those with detectable HIV-RNA at entry (P &amp;#x003C 0.0001). A detectable viral load at enrollment was the only independent variable that predicted clinical failure over one year (P &amp;#x003C 0.0001).

State AIDS Drug Assistance Programs: equity and efficiency in an era of rapidly changing treatment standards

BACKGROUND

The 54 state AIDS Drug Assistance Programs (ADAP) provide medications to HIV-infected persons with limited resources. Eligibility and coverage vary, raising concerns about health inequities.

OBJECTIVE

To compare the relative clinical and economic performance of ADAP programs.

RESEARCH DESIGN

A state-transition simulation model of HIV disease was used to explore the clinical consequences and lifetime costs associated with selected state policies. Clinical data came from the Multicenter AIDS Cohort Study, AIDS Clinical Trials Group Protocol 320, and other published randomized trials. Cost data came from the national AIDS Cost and Services Utilization Survey, and the 1999 Red Book. ADAP data came from National Association of State and Territorial AIDS Directors reports and interviews.

MEASURES

Projected life expectancy, quality-adjusted life expectancy, total lifetime direct medical costs, cost-effectiveness in dollars per quality-adjusted life year (QALY) gained.

RESULTS

ADAPs vary considerably in terms of formulary policies, health outcomes, expected costs, and cost-efficiency. Conservative projections, based on a cohort with starting mean CD4 count of 250 cells/microL, yield life expectancies ranging from 5.36 to 6.81 life years (4.69-6.01 quality-adjusted life years [QALYs]). Total per person lifetime direct medical costs range from $81,200 to $112,700; higher costs reflect increased spending on medications. Expected costs per QALY gained range from $7000 to $28,000. Under pessimistic assumptions regarding initial CD4 counts, drug efficacy, and discounting, the most comprehensive policy remains below $33,000/QALY.

CONCLUSIONS

Even the most comprehensive ADAPs constitute a cost-effective use of HIV care resources. A uniform, national ADAP formulary warrants consideration.

Comparison of Nine Resistance Interpretation Systems for HIV-1 Genotyping

HIV-1 genotyping has become a widely accepted tool for monitoring antiretroviral therapy. However, the benefit of genotyping is limited by the need to interpret the mutation pattern in order to obtain a prediction regarding susceptibility to each antiretroviral drug. Several different interpretation systems are currently available, commercially or free of charge; some are in combination with the genotyping test system used. In this study, we compared the results obtained on patient samples, using nine different resistance interpretation systems for HIV-1 genotype, and identified mutation patterns responsible for discordances between these systems. HIV-1 genotypes from 26 patients were obtained using the ViroSeq™ HIV-1 Genotyping System (Applied Biosystems). Nine resistance interpretation systems were used: the ‘virtual phenotype’ systems VirtualPhenotype™ (Virco) and Geno2Pheno ( http://cartan.gmd.de/geno2pheno.html ), the rule-based resistance algorithms Antiretroviral Drug Resistance Report (Applied Biosystems), Stanford HIV-SEQ program ( http://hivdb.stanford.edu/ ) and the ViroScorer™ system (ABL; including ANRS AC11, Detroit Medical Center, Grupo de Aconselhamento Virológico, CHL, and Rega). Discordance was defined as the same sequence being interpreted as resistant and sensitive to a substance by different systems, with intermediate scores being regarded as neutral. Results for lopinavir were not available from some interpretation systems. None of the 26 patient samples had concordant results for all drugs. The highest degree of concordance was found for the resistance scoring of lamivudine (25/26), followed by nelfinavir (23/26), indinavir, ritonavir, saquinavir (all 22/26), zidovudine, nevirapine (all 21/26), lopinavir, efavirenz (all 18/26), amprenavir, delavirdine (all 17/26), stavudine, abacavir (all 13/26), zalcitabine (7/26) and didanosine (5/26). In most cases, it was only one interpretation system that gave an interpretation different from the others. If this interpretation system was omitted, the overall discordance rate decreased by a statistically significant degree. There exists, therefore, an urgent need for standardization of interpretation algorithms for HIV-1 genotyping.

Analysis of the Virological Response with Respect to Baseline Viral Phenotype and Genotype in Protease Inhibitor-Experienced HIV-1-Infected Patients Receiving Lopinavir/Ritonavir Therapy

The virological response of multiple protease inhibitor-experienced, non-nucleoside reverse transcriptase inhibitor-naive, HIV-1-infected subjects was examined with respect to baseline viral phenotype and genotype through 72 weeks of therapy with lopinavir/ritonavir plus efavirenz and nucleoside reverse transcriptase inhibitors (Study M98-957). Using a ‘dropouts as censored’ analysis, plasma HIV RNA ≤400 copies/ml was observed in 93% (25/27), 73% (11/15) and 25% (2/8) of subjects with <10-fold, 10- to 40-fold, and >40-fold reduced susceptibility to lopinavir at baseline, respectively. In addition, virological response was observed in 91% (21/23), 71% (15/21) and 33% (2/6) of subjects with baseline lopinavir mutation score of 0–5, 6–7 and ≥8, respectively. Through 72 weeks, all subjects experiencing virological failure whose baseline isolates contained six or more protease inhibitor mutations had a common genotypic pattern, with mutations at positions 82, 54 and 10, along with a median of four additional mutations in protease. However, an equal number of subjects with a similar genotypic pattern experienced virological response. Further analysis revealed the baseline phenotypic susceptibility to lopinavir to be an additional covariate predicting response in this subset of subjects. In multivariate analyses, baseline susceptibility to lopinavir was associated with response at each time point examined (weeks 24, 48 and 72). These results provide guidance for clinically relevant interpretation of phenotypic and genotypic resistance tests when applied to lopinavir/ritonavir.

Rapid and sensitive oligonucleotide ligation assay for detection of mutations in human immunodeficiency virus type 1 associated with high-level resistance to protease inhibitors

A sensitive, specific, and high-throughput oligonucleotide ligation assay (OLA) for the detection of genotypic human immunodeficiency virus type 1 (HIV-1) resistance to Food and Drug Administration-approved protease inhibitors was developed and evaluated. This ligation-based assay uses differentially modified oligonucleotides specific for wild-type or mutant sequences, allowing sensitive and simple detection of both genotypes in a single well of a microtiter plate. Oligonucleotides were designed to detect primary mutations associated with high-level resistance to amprenavir, nelfinavir, indinavir, ritonavir, saquinavir, and lopinavir, including amino acid substitutions D30N, I50V, V82A/S/T, I84V, N88D, and L90M. Plasma HIV-1 RNA from 54 infected patients was amplified by reverse transcription-PCR and sequenced by using dideoxynucleotide chain terminators for evaluation of mutations associated with drug resistance. These same amplicons were genotyped by the OLA at positions 30, 50, 82, 88, 84, and 90 for a total of 312 codons. The sensitivity of detection of drug-resistant genotypes was 96.7% (87 of 90 mutant codons) in the OLA compared to 92.2% (83 of 90) in consensus sequencing, presumably due to the increased sensitivity of the OLA. The OLA detected genetic subpopulations more often than sequencing, detecting 30 mixtures of mutant and wild-type sequences and two mixtures of drug-resistant sequences compared to 15 detected by DNA sequencing. Reproducible and semiquantitative detection of the mutant and the wild-type genomes by the OLA was observed by analysis of wild-type and mutant plasmid mixtures containing as little as 5% of either genotype in a background of the opposite genome. This rapid, simple, economical, and highly sensitive assay provides a practical alternative to dideoxy sequencing for genotypic evaluation of HIV-1 resistance to antiretrovirals.

Genotypic testing for human immunodeficiency virus type 1 drug resistance

There are 16 approved human immunodeficiency virus type 1 (HIV-1) drugs belonging to three mechanistic classes: protease inhibitors, nucleoside and nucleotide reverse transcriptase (RT) inhibitors, and nonnucleoside RT inhibitors. HIV-1 resistance to these drugs is caused by mutations in the protease and RT enzymes, the molecular targets of these drugs. Drug resistance mutations arise most often in treated individuals, resulting from selective drug pressure in the presence of incompletely suppressed virus replication. HIV-1 isolates with drug resistance mutations, however, may also be transmitted to newly infected individuals. Three expert panels have recommended that HIV-1 protease and RT susceptibility testing should be used to help select HIV drug therapy. Although genotypic testing is more complex than typical antimicrobial susceptibility tests, there is a rich literature supporting the prognostic value of HIV-1 protease and RT mutations. This review describes the genetic mechanisms of HIV-1 drug resistance and summarizes published data linking individual RT and protease mutations to in vitro and in vivo resistance to the currently available HIV drugs.

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.

Final analysis of the Trilège induction-maintenance trial: results at 18 months

BACKGROUND

First results of Trilège demonstrated that the strategy of less intensive antiviral therapy is less effective than continuation of triple-drug therapy.

OBJECTIVE

To compare the final number of failures at month 18 and to study viral dynamics in patients experiencing a virological failure.

DESIGN

Longitudinal follow-up from a randomized controlled trial.

SETTING

Forty-three AIDS clinical-trial units.

PATIENTS

A total of 279 HIV-1 infected adults randomized in Trilège.

MEASUREMENTS

Analysis of recurrent values of HIV RNA > 500 copies/ml beyond time to virologic failure.

RESULTS

A total of 83 patients experienced virological failure by month 18; 10 in the zidovudine (ZDV) + lamivudine (3TC) + indinavir (IDV) arm, 46 in the ZDV + 3TC arm, and 27 in the ZDV + IDV arm, confirming previous results. Whatever the treatment ultimately received, 87% of patients had an HIV RNA < 500 copies/ml at month 18 with no statistical difference between randomized arms. Patients experiencing a failure in the triple-drug regimen had a greater tendency to maintain HIV RNA > 500 copies/ml beyond the time of virological failure than patients in both less intensive treatment groups who experienced failure. Lower levels of HIV RNA at failure and reinitiating of either the original triple-drug regimen or a new combination of nucleoside analogue reverse transcriptase inhibitors and protease inhibitors were associated with lower hazard ratios for developing recurrent HIV RNA > 500 copies/ml.

CONCLUSION

Results confirmed the failure of a less intensive regimen to maintain patients with a viral suppression (HIV RNA < 500 copies/ml). Although there is a lower incidence of failure in the triple-drug regimen, randomization to a less intensive regimen of ZDV + 3TC or ZDV + IDV was not detrimental, as treatment modification, either to the original triple regimen, or a different regimen was successful.

A randomized trial assessing the impact of phenotypic resistance testing on antiretroviral therapy

OBJECTIVE

To compare the effect of treatment decisions guided by phenotypic resistance testing (PRT) or standard of care (SOC) on short-term virological response.

DESIGN

A prospective, randomized, controlled clinical trial conducted in 25 university and private practice centers in the United States.

PARTICIPANTS

A total of 272 subjects who failed to achieve or maintain virological suppression (HIV-1-RNA plasma level > 2000 copies/ml) with previous exposure to two or more nucleoside reverse transcriptase inhibitors and one protease inhibitor.

INTERVENTIONS

Randomization was to antiretroviral therapy guided by PRT or SOC.

MAIN OUTCOME MEASURES

The percentage of subjects with HIV-1-RNA plasma levels less than 400 copies/ml at week 16 (primary); change from baseline in HIV-1-RNA plasma levels and number of "active" (less than fourfold resistance) antiretroviral agents used (secondary).

RESULTS

At week 16, using intent-to-treat (ITT) analysis, a greater proportion of subjects had HIV-1-RNA levels less than 400 copies/ml in the PRT than in the SOC arm (P = 0.036, ITT observed; P = 0.079, ITT missing equals failure). An ITT observed analysis showed that subjects in the PRT arm had a significantly greater median reduction in HIV-1-RNA levels from baseline than the SOC arm (P = 0.005 for 400 copies/ml; P = 0.049 for 50 copies/ml assay detection limit). Significantly more subjects in the PRT arm were treated with two or more "active" antiretroviral agents than in the SOC arm (P = 0.003).

CONCLUSION

Antiretroviral treatment guided prospectively by PRT led to the increased use of "active" antiretroviral agents and was associated with a significantly better virological response.

Underestimation of HIV type 1 drug resistance mutations: results from the ENVA-2 genotyping proficiency program

Current recommendations indicate the use of HIV-1 drug resistance genotyping in the treatment of HIV-1 infection, primarily on treatment failure, and in specific instances also before the initiation of therapy. As such, HIV-1 genotyping is becoming a standard of care parameter in HIV-1 treatment monitoring and a rapidly increasing number of laboratories now use this technology routinely. A study of proficiency, using the ENVA-2 panel, was performed to evaluate the current HIV-1 resistance genotyping quality in 34 laboratories from different parts of the world. The results demonstrated extensive interlaboratory variation in the quality of genotyping and a significant underestimation of resistance mutations, even in samples expressing pure mutant genotype. The level of variation could not be attributed to the sequencing technology used and was therefore considered to be laboratory associated. The direct clinical consequences of this may be inadequate treatment of HIV-1-infected individuals and a more rapid exhaustion of therapeutic options for the patients. Drug resistance mutations are frequently missed. Therefore, quality control programs are urgently needed. Until these are widely implemented, clinicians must consider this issue and interpret the reported genotyping results with caution.

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.

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.

Persistence and fitness of multidrug-resistant human immunodeficiency virus type 1 acquired in primary infection

This study examines the persistence and fitness of multidrug-resistant (MDR) viruses acquired during primary human immunodeficiency virus infection (PHI). In four individuals, MDR infections persisted over the entire study period, ranging from 36 weeks to 5 years, in the absence of antiretroviral therapy. In stark contrast, identified source partners in two cases showed expected outgrowth of wild-type (WT) virus within 12 weeks of treatment interruption. In the first PHI case, triple-class MDR resulted in low plasma viremia (1.6 to 3 log copies/ml) over time compared with mean values obtained for an untreated PHI group harboring WT infections (4.1 to 4.3 log copies/ml). Increasing viremia in PHI patient 1 at week 52 was associated with the de novo emergence of a protease inhibitor-resistant variant through a recombination event involving the original MDR virus. MDR infections in two other untreated PHI patients yielded viremia levels typical of the untreated WT group. A fourth patient's MDR infection yielded low viremia (<50 to 500 copies/ml) for 5 years despite his having phenotypic resistance to all antiretroviral drugs in his treatment regimen. In two of these PHI cases, a rebound to higher levels of plasma viremia only occurred when the M184V mutation in reverse transcriptase could no longer be detected and, in a third case, nondetection of M184V was associated with an inability to isolate virus. To further evaluate the fitness of MDR variants acquired in PHI, MDR and corresponding WT viruses were isolated from index and source partners, respectively. Although MDR viral infectivity (50% tissue culture infective dose) was comparable to that observed for WT viruses, MDR infections in each case demonstrated 2-fold and 13- to 23-fold reductions in p24 antigen and reverse transcriptase enzymatic activity, respectively. In dual-infection competition assays, MDR viruses consistently demonstrated a marked replicative disadvantage compared with WT virus. These results indicate that MDR viruses that are generated following PHI can establish persistent infections as dominant quasispecies despite their impaired replicative competence.

Discordance between genotypic and phenotypic drug resistance profiles in human immunodeficiency virus type 1 strains isolated from peripheral blood mononuclear cells

The aim of the study was to analyze the relationship between genotypic and phenotypic drug resistance profiles of human immunodeficiency virus type 1 (HIV-1) strains isolated from patients during double-analogue nucleoside therapy. A drug-resistant HIV strain was isolated from 20 out of 25 patients, with 16 (64%) subjects carrying a virus with multiple drug resistance mutations. The most frequent resistance mutations were M184V (18 isolates) and M41L (7 isolates). Discordance between the genotypic and phenotypic profile for at least one drug was detected in 16 out of 25 strains. Particularly, eight isolates had a discordant genotypic-phenotypic resistance pattern for two drugs and one isolate had such a pattern for three drugs. A genotypic resistance pattern with a phenotypic sensitivity profile was detected in six isolates (four resistant to zidovudine and two resistant to lamivudine). On the other hand for several strains a genotypic pattern of sensitivity pattern to abacavir (10 strains), didanosine (7 strains), stavudine (3 strains), zidovudine (2 strains), and lamivudine (1 strain) with a phenotypic resistance profile was detected. After a follow-up period of 8 months, an impairment of virological and immunological parameters was detected only in subjects with an HIV-1 isolate with a phenotypic resistance profile in despite of the genotypic results. Predicting resistance phenotype from genotypic data has important limitations. Despite the low number of patients and the short follow-up period, this study suggests that during failing therapy with analogue nucleosides, a phenotypic analysis could be performed in spite of an HIV genotypic sensitivity pattern.

Salvage antiretroviral therapy in HIV infection

Highly-active antiretroviral (ARV) therapy (HAART) has lead to a sharp decline in AIDS-related morbidity and mortality. Treatment failure is a common, significant problem and as many as 50% of patients have detectable plasma HIV RNA despite being on combination ARV therapy. Clinicians must be knowledgeable about the reasons for treatment failure and the best options available for management. Treatment failure can occur because of non-compliance, drug discontinuation, lack of drug potency, inadequate drug plasma concentration and drug resistance. Strategies used when selecting salvage therapy include the use of resistance testing to choose a regimen, the exploitation of pharmacokinetic interactions by boosting protease inhibitor (PI) trough levels and counselling the patient on compliance. When selecting the agents to use in salvage therapy, the new regimen should ideally include as many new agents to which no or minimal resistance is anticipated and at least one new class of drugs if possible. Data on salvage therapy mostly comes from anecdotal reports and retrospective cohort studies. With a paucity of clinical trial data, clinicians are often forced to prescribe unproven regimens based on what is anticipated about cross-resistance and drug interactions. It is important that new agents and new targets continue to be developed as an increasing number of patients in practice have exhausted all treatment options.

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.

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.

Prevalence of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance-associated mutations and polymorphisms in NNRTI-naïve HIV-infected patients

BACKGROUND

The efficacy of treatment containing nonnucleoside reverse transcriptase inhibitors (NNRTIs) could be compromised in NNRTI-naïve patients already harboring a virus resistant to NNRTIs. On the contrary, hypersusceptibility to NNRTIs in patients having failed nucleoside reverse transcriptase inhibitor (NRTI)-containing regimens has been described and has been associated with improved outcome.

METHOD

We assessed the prevalence of NNRTI resistance-associated mutations or polymorphisms in 146 antiretroviral-naïve patients and in 181 HIV-infected patients who were given an NNRTI-based regimen. We phenotypically evaluated the NNRTI susceptibility of 41 strains presenting with amino acid substitutions at positions involved in NNRTI resistance.

RESULTS

In the 268 genotypically analyzable samples, the overall prevalence of NNRTI resistance-associated mutations was 2% (6/268 patients). The prevalence of strains with amino acid substitutions at reverse transcriptase (RT) gene positions (A98, K101, K103, V106, V108, V179) involved in NNRTI resistance was 15%. Hypersusceptibility to NNRTI was rare (2%, 1/41) in those samples. RT substitutions at positions involved in NNRTI resistance were not associated with a significantly worse virologic outcome in NNRTI-treated patients. Our understanding of small shifts in IC50 values (higher or lower) toward NNRTI is very limited. The significance of many RT mutations on NNRTI susceptibility is not clear.

CONCLUSION

In contrast to resistance mutations, RT substitutions at positions involved in NNRTI resistance are frequent. They are not associated with a worse virologic outcome or with decreased phenotypic susceptibility to NNRTIs. It may be prudent not to rule out the use of NNRTIs in patients with small shifts in IC50 values or poorly understood mutations.

Comparison of health state utilities using community and patient preference weights derived from a survey of patients with HIV/AIDS

OBJECTIVES

The authors compare health state utilities derived from a national survey of patients with HIV/AIDS to represent community-based preferences with utilities derived from the same survey representing patient preferences; explore the relationships between these utilities and the dimensions of the SF-6D health state classification; and examine the implications of differences in the source of utilities for a cost-effectiveness analysis of early treatment of patients with HIV/AIDS.

METHODS

The authors derived community-based standard gamble (SG) utilities using an algorithm developed for the SF-6D health state classification system. The authors derived patient SG utilities from HIV/AIDS patient rating scale self-assessments using a power transformation. Data were from the HIV Cost and Services Utilization Study, a probability sample of 2864 HIV-infected adults receiving care in the United States in 1996.

RESULTS

Patient SG utilities were higher than community SG utilities by 4% to 9% (0.979 vs. 0.937, 0.910 vs. 0.841, and 0.845 vs. 0.778; P < 0.001 for all comparisons). In regression analyses, patient SG utilities were less influenced by physical functioning, pain, and mental health dimensions of the SF-6D. The base case results of a cost-effectiveness analysis comparing early antiretroviral therapy to deferred therapy were unaffected by the choice between community ($20,100 per quality-adjusted life year) and patient ($18,400 per quality-adjusted life year) perspectives. The impact of the choice of utilities remained small in sensitivity analyses that varied the influence of treatment side effects on utilities and the initial symptom status of patients.

CONCLUSION

There are differences between community and patient utilities for HIV/AIDS health states, although even when treatment side effects are important, these differences may not affect cost-effectiveness ratios.

Viral load outcome of non-nucleoside reverse transcriptase inhibitor regimens for 2203 mainly antiretroviral-experienced patients

OBJECTIVE

To assess the factors associated with virologic response to non-nucleoside reverse transcriptase inhibitor (NNRTI)-containing regimens in a large clinic cohort.

DESIGN

Inception cohort.

SETTING

HIV clinics in Europe

PATIENTS

We identified all patients in EuroSIDA who began a regimen including either nevirapine or efavirenz (not both) after July 1997 and for whom pre-therapy viral load and CD4 cell count were known.

MAIN OUTCOME MEASURES

Virological failure.

RESULTS

A total of 1325 patients initiated nevirapine and 878 efavirenz. Respectively, median start dates were October 1998 and May 1999. Other factors at baseline, including CD4 cell count, viral load, previous AIDS, previous antiretroviral drug use and make-up of the NNRTI-containing regimen were all approximately similar between the nevirapine and efavirenz groups. A total of 669 patients experienced virological failure during follow-up. In a Cox model, less protease inhibitors and nucleoside reverse transcriptase inhibitors (NRTIs) previously used, higher CD4 nadir, lower viral load at baseline, a previous AIDS diagnosis and less NRTIs in the regimen were associated with lower risk of virological failure. The relative hazard of virological failure comparing those on efavirenz with those on nevirapine was 0.57 (95% confidence interval, 0.47-0.69; P < 0.0001).

CONCLUSIONS

The difference in virologic outcome between those using nevirapine and efavirenz in this almost entirely drug-experienced population could reflect differences in effectiveness of the drugs in this setting but, despite the similarity between groups at baseline, bias cannot be excluded as an explanation. Replication of these findings in randomized trials and other cohort studies is required.

A recombinant virus assay using full-length envelope sequences to detect changes in HIV-1 co-receptor usage

The clinical management of HIV-1 infection has benefited enormously from molecular characterization of drug resistance as well as determination of the viral phenotype in vitro. HIV-1 infected individuals on HAART are currently monitored for the development of drug resistance variants allowing clinicians to redesign drug regimens. An understanding of the molecular basis of the evolution of drug resistance in vivo allows the improvement of the drugs as well as in vitro evaluation of new antiviral compounds alone or in combination with those currently approved. New findings suggest that viral envelopes could be a target to inhibit infection and replication. Therefore the generation of a recombinant virus assay (RVA) to allow the phenotypic determination of drug resistance against entry inhibitors (EI) is anticipated. We constructed an env-deleted clone of HIV-1 using the molecular clone NL-4.3. PCR amplified complete envelope genes (NL-4.3, BaL, primary envelope-genes) were ligated in vitro with a deletion clone (pNL-deltaK) and PM1-cells, supporting the replication of R5- and X4-tropic viruses, were transfected. Determination of co-receptor usage of the harvested recombinant virus-swarm revealed no difference compared to the molecular clones derived individually from three different patients. These results clearly show that an envelope-based RVA is practicable to monitor HIV-co-receptor usage at a given time point. Furthermore, this assay will allow to monitor resistance development against existing and future entry inhibitors and will aid to improve the management of HIV-therapy.

Susceptibility testing. Viral pathogens

The control of the global expansion and proliferation of the AIDS pandemic has been complicated by the emergence of resistant strains of HIV-1 to the many new antiviral drugs directed to the genes coding for reverse transcriptase and protease enzymes of the virus. Similarly, new drug regimens for the management of chronic hepatitis B and C infections have been complicated by the lack of sustained clinical responses recently associated with either nucleotide mutation (HBV) or specific genotype of the virus (HCV). Commercial systems for performing and interpreting genotypic analysis will facilitate the recognition of informative mutations, standardize results between laboratories, and produce informative and interpretative result formats for optimal treatment of patients. Drug-resistant strains of herpesviruses (HSV, VZV, CMV) are generally associated with prolonged treatment of these infections in immunocompromised patients. Ultimate relevance of genotypic assays for routine clinical practice will require correlation with phenotypic results and the outcomes of long-term studies associating clinical improvement with antiviral drugs with specific mutation patterns of these viruses.