Factors associated with the successful modification of antiretroviral therapy. HIV Outpatient Study Investigators

Virological response to Salvage Therapy in HIV-Infected Persons Carrying the Reverse Transcriptase K65R Mutation

Background

The effect of the HIV reverse transcriptase K65R mutation on virological response to salvage therapy has not been clearly defined.

Methods

From six Italian clinical centres, all consecutive patients starting salvage antiretroviral therapy after virological failure in the presence of the K65R mutation identified by a genotypic resistance test were selected.

Results

Among 145 subjects included over a 197 person-year follow-up, the estimated probability of virological response (VR, defined as reaching HIV RNA <50 copies/ml after salvage therapy) at 24 and 48 weeks was 36% and 60%, respectively. The strongest independent predictor of VR was the inclusion of a thymidine analogue (TA) in the salvage regimen. The presence of M184V and the introduction of lopinavir/ritonavir as new drug were both marginally associated with better outcome. After 24 weeks of salvage therapy, the median reduction in HIV-1 RNA was -1.36 log10 copies/ml (interquartile range [IQR] 0.10–2.46): at multivariable regression analysis, salvage regimens containing a TA (β=+0.80; P=0.02) and lamivudine (β=+1.21; P=0.02) as new drug had a positive effect on the reduction of HIV-1 RNA.

Conclusions

Development of the K65R mutation does not preclude a high rate of virological response to rescue therapy. Inclusion of a TA in the salvage regimen and the presence of a M184V mutation could have a favourable effect on virological outcome.

Crystal structures of clinically relevant Lys103Asn/Tyr181Cys double mutant HIV-1 reverse transcriptase in complexes with ATP and non-nucleoside inhibitor HBY 097

Lys103Asn and Tyr181Cys are the two mutations frequently observed in patients exposed to various non-nucleoside reverse transcriptase inhibitor drugs (NNRTIs). Human immunodeficiency virus (HIV) strains containing both reverse transcriptase (RT) mutations are resistant to all of the approved NNRTI drugs. We have determined crystal structures of Lys103Asn/Tyr181Cys mutant HIV-1 RT with and without a bound non-nucleoside inhibitor (HBY 097, (S)-4-isopropoxycarbonyl-6-methoxy-3-(methylthio-methyl)-3,4-dihydroquinoxalin-2(1H)-thione) at 3.0 A and 2.5 A resolution, respectively. The structure of the double mutant RT/HBY 097 complex shows a rearrangement of the isopropoxycarbonyl group of HBY 097 compared to its binding with wild-type RT. HBY 097 makes a hydrogen bond with the thiol group of Cys181 that helps the drug retain potency against the Tyr181Cys mutation. The structure of the unliganded double mutant HIV-1 RT showed that Lys103Asn mutation facilitates coordination of a sodium ion with Lys101 O, Asn103 N and O(delta1), Tyr188 O(eta), and two water molecules. The formation of the binding pocket requires the removal of the sodium ion. Although the RT alone and the RT/HBY 097 complex were crystallized in the presence of ATP, only the RT has an ATP coordinated with two Mn(2+) at the polymerase active site. The metal coordination mimics a reaction intermediate state in which complete octahedral coordination was observed for both metal ions. Asp186 coordinates at an axial position whereas the carboxylates of Asp110 and Asp185 are in the planes of coordination of both metal ions. The structures provide evidence that NNRTIs restrict the flexibility of the YMDD loop and prevent the catalytic aspartate residues from adopting their metal-binding conformations.

Trends in Antiretroviral Therapy Use and Survival Rates for a Large Cohort of HIV-Infected Children and Adolescents in the United States, 1989-2001

BACKGROUND

In the United States, HIV-infected children and adolescents are aging and using antiretroviral (ARV) therapy for extended periods of time.

OBJECTIVE

To assess trends in ARV use and long-term survival in an observational cohort of HIV-infected children and adolescents in the United States.

METHODS

The Pediatric Spectrum of HIV Disease Study (PSD) is a prospective chart review of more than 2000 HIV-infected children and adolescents. Patients were included in the analysis from enrollment until last follow-up.

RESULTS

Triple-ARV therapy use (for 6 months or more) increased from 27% to 66% during 1997 to 2001 (P < 0.0001, chi for trend). The proportion of patients receiving 3 or more sequential triple-therapy regimens also increased from 4% to 17% during 1997 to 2001 (P < 0.0001, chi for trend), however, and the durability of triple-therapy regimens decreased from 13 to 7 months from the first to third regimen. Survival rates for the 1997 to 2001 birth cohorts were significantly better than for the 1989 to 1993 and 1994 to 1996 cohorts (P < 0.0001).

CONCLUSIONS

Survival rates in the PSD cohort have increased in association with triple-ARV therapy use. With continued changes in ARV regimens, effective modifications in ARV therapy and the sustainability of gains in survival need to be determined.

Durability and predictors of success of highly active antiretroviral therapy for ambulatory HIV-infected patients

OBJECTIVE

To evaluate the durability and correlates of the effectiveness of highly active antiretroviral therapy (HAART) in terms of AIDS-related mortality and morbidity, HIV viremia, and CD4 cell count.

DESIGN AND SETTING

The HIV Outpatient Study (HOPS), a prospective observational cohort from eight clinics in the USA that has been running since 1994.

PARTICIPANTS

Mortality and opportunistic infection (OI) rates were calculated for 1769 HOPS patients with CD4 cell count ever < 100 x 106/l. Data from 1022 HAART recipients with CD4 cell count ever < 500 x 106/l were analyzed.

MAIN OUTCOME MEASURES

Mortality and AIDS-related OI rates. Treatment success was defined as a reduction in plasma HIV RNA copies/ml of 1.0 log10 or more, or to an undetectable level, with a stable or rising CD4 cell count. Durable success was a successful response lasting at least 12 consecutive months.

RESULTS

HAART use remained high; mortality and OIs low. Patients received a mean of 1.8 HAART regimens. Median time on first HAART (n = 1022) was 11.8 months; second HAART (n = 424) 7.4 months; and third HAART (n = 213) 7.2 months. Treatment success was most likely for pre-HAART treatment naive patients; durably successful first HAART most often contained one protease inhibitor, particularly indinavir or nelfinavir (P = 0.006, adjusted for prior antiretroviral therapy). Durable success was most likely with first (49.0%) than with second (29.6%, P = 0.013) or third or more HAART regimens (14.9%, P < 0.0001). Time to success with first HAART was shorter for durable than non-durable responders (3.6 versus 5.3 months, respectively; unadjusted P = 0.002).

CONCLUSIONS

Durable response to HAART was associated with being pre-HAART therapy naive, prompt response to HAART, and single protease inhibitor-based initial HAART (indinavir or nelfinavir). Sequential HAART regimens were of progressively shorter duration, demonstrated less viral suppression and CD4 cell count benefit, yet low morbidity and mortality rates were sustained.

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.

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.

"Discordant" increases in CD4 cell count relative to plasma viral load in a closely followed cohort of patients initiating antiretroviral therapy

BACKGROUND

In HIV-positive persons receiving antiretroviral therapy, CD4 cell responses are associated with optimal suppression of viral replication. However, increases in CD4 cell counts in the absence of viral suppression have been reported. We characterized plasma viral load (pVL) and CD4 cell count increases in closely followed patients to evaluate determinants and the prevalence of CD4 cell responses at a populational level.

METHODS

All HIV-positive patients in the province of British Columbia, Canada, who were antiretroviral naive and initiated therapy between August 1996 and May 1998 were eligible for the study. The selection criteria were that patients had to have CD4 cell counts and pVLs measured at baseline and at least once during eight 16-week periods after the initiation of therapy. We characterized CD4 cell responses and sought patients who had a "discordant" increase at 1 year, which was defined as an increase in CD4 cell count of >or=50/mm3 with a <1 log10 decrease in pVL. We also evaluated adherence and antiretroviral use.

RESULTS

Overall, when baseline and 1-year pVLs and CD4 cell counts were compared, 6.2% of patients had CD4 cell count increases without pVL decreases of >or=1 log10. However, when all pVLs before 1 year were considered, 92% of the discordant increases could be attributed to prior transient or partial viral suppression. Furthermore, although substantial increases in CD4 cell counts were observed in transient virologic responders, the cumulative number of antiretroviral agents used by this group was significantly higher than that used by full virologic responders (p <.001).

CONCLUSIONS

Our results demonstrate that virtually all CD4 cell count increases can be attributed to transient or partial pVL suppression. Unmeasured pVL suppression likely explains discordant responses that have been previously reported. Similarities between transient and full virologic responders also appear to be time limited and are often associated with greater cumulative use of antiretroviral therapy by transient virologic responders.

Salvage therapy with amprenavir and ritonavir: prospective study in 17 heavily pretreated patients

OBJECTIVE

To evaluate the safety profile and efficacy of salvage regimens containing amprenavir (APV) 600 mg twice daily and ritonavir (RTV) 200 mg twice daily.

DESIGN

Prospective, single-center study.

METHOD

The patient database of the department of infectious diseases was screened for patients who had failed at least two successive three-drug combinations. These patients were proposed to take APV and RTV in association with two to four other drugs. They were followed monthly for 6 months.

RESULTS

Seventeen patients were included. They had been previously treated for 70 +/- 23 months. At baseline, viral load (VL) was 4.86 +/- 0.98 log10 copies/mL and CD4 187 +/- 145 10(6)/L. On week 24, using intent-to-treat analysis, VL decreased to 2.95 +/- 1.59 log10 copies/mL and CD4 increased to 365 +/- 210 10(6)/L. Nine patients (53%) had a VL < 2.3 log10 copies/mL. The most common adverse events were grade 1 or 2 diarrhea and an increase of cholesterol and triglyceride levels. Mean APV trough concentration was 1727 +/- 1749 ng/mL on week 24.

CONCLUSION

These data show that the combination of low-dose RTV and reduced doses of APV is safe. This combination can be added to nonnucleoside analogs.

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.

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.

Comparison of different treatment regimens for the emergence of new resistance under therapy

OBJECTIVE

To compare the effects of different therapy regimens on the probability of emergence of new resistant mutants during therapy.

METHODS

We developed a stochastic model of infection and treatment to calculate the probability of de novo resistance during therapy. We simulated diverse treatment regimens, with different efficacy in controlling HIV replication. We studied the use of genotypic testing to choose treatment protocols specifically tailored against the wild type.

RESULTS

The probability of emergence of a previously nonexisting drug-resistant mutant during therapy depends crucially on the drug regimen used. In particular, therapy protocols targeting the wild-type strain may lead to a higher probability of treatment failure due to resistance. Conversely, targeting the minority strains in the population, which readily mutate into the resistant variety, significantly lowers the probability of a new resistant emerging under therapy.

CONCLUSIONS

Use of genotypic testing may lead to wrong decisions in the choice of therapy if the population dynamics of production of new resistant mutants is not taken into account.

Multiple drug rescue therapy for HIV-infected individuals with prior virologic failure to multiple regimens

OBJECTIVES

To characterize the antiviral response and tolerability of a multi-drug rescue therapy (MDRT) among heavily pretreated patients.

METHODS

Observational study conducted in a single, university-based tertiary referral clinic. Patients (n = 106) who failed several prior regimens started MDRT including at least five antiretroviral (ARV) drugs between August 1997 and June 1998. The most common starting regimen included three nucleoside reverse transcriptase inhibitors and two protease inhibitors, which was prescribed to 45 (42.5%) patients. Virologic response was defined as plasma viral load < 400 copies/ml on at least two consecutive visits.

RESULTS

Median prior ARV exposure was seven drugs over a median time of 43 months. Fifty-nine percent of the patients were phenotypically (VIRCO Antivirogram) resistant at baseline to seven or more ARV. Median plasma viral load change following initiation of MDRT was -1.04 log10 copies/ml over a median of 15 months. Using intention-to-treat analysis 40% of patients had plasma viral load values < 400 copies/ml between weeks 47 and 57 of follow-up. Twenty-six patients (25%) experienced severe laboratory abnormalities or subjective adverse drug effects and six of these participants discontinued therapy.

CONCLUSION

MDRT induced a substantial antiviral response in this heavily pretreated group of patients despite extensive phenotypic resistance at baseline. Adverse effects were frequent but generally manageable. Our data suggest that relying exclusively on historical, clinical and laboratory evidence may not be sufficient to rule out a possible antiviral response when multiple drug regimens are used in this heavily pretreated patient population.