Luisa Valer

Predictors of Virological Response to Atazanavir in Protease Inhibitor-Experienced Patients

Abstract Background: Atazanavir (ATV) is the latest approved HIV protease inhibitor (PI). Even though it is very convenient (only two capsules once a day), concerns have risen about its potency. Method: The clinical performance of ATV 400 mg once a day was examined in all PI-experienced patients who were included in the ATV expanded access program conducted in a single institution. The predictive value of baseline drug resistance HIV genotypes, ATV plasma trough levels, and the genotypic inhibitory quotient (GIQ) on the virological response at week 24 was assessed. Results: Data from 92 patients were analyzed. ATV was prescribed as part of a rescue intervention (45%), a simplification strategy (11%), or an attempt to ameliorate hyperlipidemias (23%) or other toxicities (16%). Tenofovir (TDF) was concomitantly used with ATV in 78% of patients. None received ritonavir boosting. In patients with detectable viremia at baseline (65%), the median HIV RNA drop was 0.7 logs. The median ATV Cmin was 0.12 μg/mL (IQR, 0.05-0.22 μg/mL), which is clearly above the IC90 (90% inhibitory concentration) for ATV in wild-type viruses. The virological response did not correlate significantly with ATV Cmin. The median number of protease resistance mutations was lower in patients showing virological response than in nonresponders (1 vs. 5; p = .07). A higher HIV RNA drop was associated with a higher GIQ (p = .02; β = –5.4; 95% CI, –10 to –1). Only 4 patients (4%) discontinued treatment due to ATV-related toxicities (hyperbilirubinemia in 1). Bilirubin levels were associated with ATV plasma concentrations (p = .05; β = 3.2; 95% CI, –0.1 to 6.5). The rate of hypertriglyceridemia and hypercholesterolemia declined significantly with respect to baseline. Conclusion: ATV is relatively safe and provides significant virological response in PI-experienced patients, mainly among those with a low number of protease resistance mutations. The GIQ predicts accurately the virological response in patients receiving ATV. Hyperbilirubinemia is associated with higher ATV plasma levels.

Prediction of virological response to lopinavir/ritonavir using the genotypic inhibitory quotient.

The predictive value of virological response to lopinavir (LPV)/ritonavir (r) was assessed in 126 HIV-infected patients who failed antiretroviral therapy and had begun a rescue intervention based on LPV/r. At 3 months, subjects with < or =6 protease (PRO) resistance mutations showed a higher rate of virological response (HIV-RNA drop > 1 log or to <50 copies/ml) than patients with >6 PRO resistance mutations (77% versus 48%; p = 0.01). On the other hand, virological responders had greater mean LPV plasma trough levels than nonresponders (6.4 versus 3.9 microg/ml; p = 0.02). A positive correlation was found between LPV trough concentration and viral load reductions at 3 months under LPV/r (r = 0.23; p = 0.017). Overall, virological response was seen in 80.8% of patients with LPV trough levels >4.8 microg/ml while in only 52.5% of patients with lower LPV trough concentrations (p = 0.002). In the multivariate analysis, both < or =6 PRO resistance mutations and LPV trough levels >4.8 microg/ml were independent predictors of virological response to salvage therapy with LPV/r. A genotypic inhibitory quotient (GIQ) was estimated for each patient based on the ratio between LPV trough levels and the number of PRO resistance mutations. A positive strong correlation was found between GIQ and viral load reductions (r = 0.42; p = 0.002). Virological response was seen in 78% of patients with a GIQ >0.7 but only in 41.6% of those with lower GIQ (p = 0.004). When LPV trough levels >4.8 microg/ml, PRO resistance mutations < or =6, and GIQ >0.7 were all included in a stepwise multivariate analysis, GIQ remained as the main independent predictor of response to LPV/r.

Predictors of selection of K65R: tenofovir use and lack of thymidine analogue mutations

Over the past 5 years, 1846 HIV-infected patients underwent drug resistance testing at our institution. None out of 216 drug-naive subjects showed K65R. However, it was recognized in 53 out of 1630 antiretroviral-experienced patients (3.3%), of whom 10 had never been exposed to tenofovir. The rate of K65R increased from 0.6% in 1999 to 11.5% in 2004. The recognition of K65R correlated negatively with the presence of thymidine analogue mutations but positively with Q151M.

Impact of HIV genotyping and drug levels on the response to salvage therapy with saquinavir/ritonavir.

A total of 139 HIV-infected adults failing a protease inhibitor (PI) regimen were recruited in a multicentre, prospective, open trial. All began saquinavir soft gel 1000 mg and ritonavir 100 mg twice a day plus two nucleoside analogues. Ten discontinued treatment because of adverse events. Plasma HIV-RNA levels fell > 1 log at 24 weeks in 44.5% of patients in an intent-to-treat analysis. The number of PI resistance mutations and saquinavir plasma levels independently predicted the virological response.

Prevalence of the HIV-1 protease mutation I47A in clinical practice and association with lopinavir resistance.

Mutation proI47A has recently been associated with lopinavir/ritonavir (LPV/r) resistance. Only four out of 1859 specimens (0.2%) sent for drug resistance testing (219 drug-naive and 1650 antiretroviral-experienced) showed I47A. All belonged to patients failing LPV/r. The prevalence among protease inhibitor-experienced patients was 0.6%. Phenotypic testing showed that proI47A caused high-level lopinavir resistance (> 100-fold) and cross-resistance to amprenavir, whereas it caused hypersusceptibility to saquinavir. ProI47A should thus be considered the primary lopinavir resistance mutation.

Comparison of the efficacy, safety and predictive value of HIV genotyping using distinct ritonavir-boosted protease inhibitors

The pharmacokinetic profile of protease inhibitors (PI) is improved significantly by adding low doses of ritonavir (rit). The use of rit-boosted PI allows the reduction of pill burden, improves dosing schedules and enhances drug exposure, all factors that have been associated with a greater benefit of antiretroviral therapy. All patients receiving rit 100 mg bid together with saquinavir (SQV) soft gel 1000 mg bid, indinavir (IDV) 800 mg bid or lopinavir (LPV) 400 mg bid, as part of a salvage regimen, were retrospectively analyzed in a reference institution. Only subjects who had failed all three antiretroviral drug families in the past were included. A total of 299 patients were included in the study (121 on SQV, 62 on IDV and 116 on LPV). Mean plasma HIV-RNA and CD4 lymphocyte counts at baseline were less favourable in the LPV group (4.4 logs, 275 cells/microl) with respect to SQV (4.3 logs, 355 cells/microl) and IDV (3.7 logs, 409 cells/microl) groups (P < 0.05). The proportion of subjects experiencing virological success (attainment of either < 500 HIV-RNA copies/ml or > 1 log reduction) in an intent-to-treat analysis at 24 weeks was 61% with LPV, 49% with SQV and 48% with IDV. The CD4 count increased 48% with SQV, 45% with IDV and 37% with LPV. The proportion of subjects discontinuing therapy due to adverse events was higher using IDV (27%) than using either SQV (11%) or LPV (6%) (P < 0.05). The presence of < 5 or > 5 PI resistance mutations at baseline discriminated significantly better who would respond to therapy in all instances: 90 vs. 48% with LPV, 95 vs. 21% with SQV and 90 vs. 23% with IDV. The efficacy of rit-boosted PI combinations is greatly influenced by the extent of baseline PI resistance. Differences, not only in potency, but mainly in tolerance may favour the selection of one dual PI combination over others.

Performance of Six Different Ritonavir-Boosted Protease Inhibitor–Based Regimens in Heavily Antiretroviral-Experienced HIV-Infected Patients

Abstract Background: Regimens based on ritonavir-boosted protease inhibitors (PI/r) are often used as rescue interventions. It is unclear whether significant differences exist between distinct PI/r. Method: All HIV+ patients who had experienced PI failure at two HIV clinics and were rescued with a regimen based on saquinavir (SQV)/r 1000/100 mg bid, indinavir (IDV)/r 800/100 mg bid, lopinavir (LPV)/r 400/100 mg bid, amprenavir (APV)/r 600/100 mg bid, atazanavir (ATV)/r 300/100 mg qd, or tipranavir (TPV)/r 500/200 mg bid were retrospectively examined. A significant virological response (VR) was defined as >1 log reduction in plasma HIV-RNA or to <50 copies/mL at week 24. Results: A total of 389 patients were included in the analysis: 139 on SQV/r, 35 on IDV/r, 129 on LPV/r, 35 on APV/r, 29 on ATV/r, and 22 on TPV/r. No significant differences in HIV-RNA and CD4 counts at baseline were recognized between groups. In a multivariate analysis, only the total number of protease resistance mutations was associated with a lower VR (odds ratio [OR] = 0.77, 95% CI 0.68–0.87, p .001). The presence of <5 or ⩾5 protease resistance mutations at baseline was the best threshold to discriminate the achievement of VR in any treatment group. In an intent-to-treat analysis, for individuals with ⩾5 protease resistance mutations, the rates of VR were 64% with TPV/r, 47% with LPV/r, 46% with SQV/r, 33% with ATV/r, 25% with IDV/r, and 16% with APV/r. Adverse events leading to treatment withdrawal occurred more frequently using IDV/r (22.8%) than others (p = .03). Conclusion: The rate of VR in salvage therapy using PI/r-based regimens is relatively high in PI-experienced patients. The efficacy is greatly influenced by the number of baseline protease resistance mutations; 5 mutations is the best threshold to predict the chances of VR to any PI/r-based regimen.

Impact of drug levels and baseline genotype and phenotype on the virologic response to amprenavir/ritonavir-based salvage regimens.

Coadministration of amprenavir (APV) with small doses of ritonavir (RTV) results in a significant increase in APV plasma concentrations. Viruses showing resistance to other protease inhibitors (PI) may remain susceptible to APV, supporting a role for this drug in salvage therapy. We enrolled 35 patients who began a rescue intervention based on APV/RTV 600/100 mg twice daily. Their median viral load before beginning APV/RTV was 4.15 logs and their median CD4 count was 247 cells per microliter. The median prior PI exposure was of 43 months. At baseline, the median number of PI resistance mutations was 7. A significant virologic response (VR) (>1 log drop in plasma HIV-RNA and/or to <50 copies per milliliter) was recorded in 21.7% (5/23) of treated patients at week 48 (14.3% in the intent-to-treat analysis). The VR was significantly more frequent among subjects with less than 5 PI resistance mutations (66.6% vs. 5.8%; p = 0.008). Patients with prior exposure to lopinavir showed VR significantly less frequently than those not exposed to that drug (11% versus 60%; p < 0.05). The mean APV plasma trough concentration at week 12 was 1.3 microg/mL, and did not differ significantly comparing subjects having or not having VR. A trend toward a higher VR rate at week 48 was noticed among subjects with high genotypic inhibitory quotients (GIQ). In summary, HIV genotyping but not drug levels might be helpful to predict which patients would benefit from a rescue intervention based on APV/RTV 600/100 twice daily.

Long-Term Outcome of HIV-Infected Patients with Multinucleoside-Resistant Genotypes

Abstract Background: Multiple resistance to nucleoside analogs mediated by the Q151M complex and/or codon 67-69 inserts/deletions represents a growing problem among HIV-infected persons, most of whom have been exposed to sequential therapies for long periods of time. Patients and Method: All plasma samples collected from HIV-infected patients failing antiretroviral therapy and referred for HIV genotyping to our institution during the last 3 years were examined. Genetic analysis of the reverse transcriptase (RT) and protease (PR) genes was performed using an automatic sequencer. Results: Multinucleoside-resistance (MNR) genotypes were recognized in 22 (2.9%) of 761 participants. Twelve of them carried the Q151M complex and 9 harbored different codon 67-69 inserts. One participant carried a deletion at codon 67 of the RT gene. All patients with MNR viruses had been exposed to nucleoside analogs for a median of 54 months (range, 19-96). The mean plasma HIV RNA at the time MNR was first identified was 4.62 log and the mean CD4 count was 227 cells/μL. All patients with MNR viruses except two began salvage therapies based on protease inhibitors (PIs). Overall, 54.5% (12/22) of participants showed a significant virologic response (defined as >1 log reduction in plasma HIV RNA). Seven of them reached <50 copies/mL and remained with undetectable viremia for a median of 17 months (range, 8-50). No differences were found when patients with Q151M and codon 67-69 rearrangements were compared. The only predictor of response was the inclusion of ritonavir-boosted PI in the salvage regimen. In all patients with virologic failure, MNR genotypes have persisted over time. Conclusion: The prevalence of viruses with MNR genotypes is currently low (~3%) among HIV-infected patients failing antiretroviral therapy. The expected poor prognosis of patients harboring MNR viruses may often be overcome using rescue interventions based on potent ritonavir-boosted PI combinations.

Superinfección por el virus de la inmunodeficiencia humana: implicaciones clínicas y biológicas

La demostracion de particulas virales del VIH-1 con secuencias geneticas recombinantes, esto es, que corresponden a mas de una variante viral, sugiere que un individuo ha sido infectado por distintos subtipos del VIH-1. Esto puede ocurrir como resultado de una superinfeccion o de una coinfeccion. En el primer caso, la nueva infeccion ocurre en un sujeto ya infectado previamente, mientras que en la coinfeccion la exposicion a la diversas variantes del VIH-1 ocurre a la vez. La demostracion de la superinfeccion representa una evidencia indirecta en contra de una inmunidad protectora frente al VIH-1 y, por tanto, en contra de la utilidad de una vacuna.