Viral efficacy maintained and safety parameters improved with a reduced dose of stavudine: a pilot study

OBJECTIVES

Stavudine (d4T) is a potent but potentially toxic nucleoside reverse transcriptase inhibitor that is still widely used in developing countries. This study's aim was to determine the efficacy and safety profile of lower-dose d4T.

METHODS

Multi-centre, open-label, single-arm, pilot, 48-week study in French patients weighing >60 kg with viral load <400 HIV-1 RNA copies/mL who were receiving d4T 40 mg twice daily and then switched to 30 mg twice daily. The primary endpoint was the proportion with plasma viral load <400 copies/mL at week 24. Secondary endpoints included the proportion with <50 copies/mL at weeks 24 and 48, changes in mitochondrial DNA, CD4 cell count and pharmacokinetics, and clinical and laboratory safety.

RESULTS

Fifty-seven patients enrolled. Baseline CD4 count was 584 cells/microL; viral loads were <400 copies/mL and <50 copies/mL in 100% and 89%, respectively. Prior antiretroviral drug exposure was 6.9 years, d4T exposure was 6.3 years. Fifty-six out of 57 (98%) patients had viral load <400 copies/mL and 51 (89%) had viral load <50 copies/mL at week 24. Median CD4 count increased by 63 cells/microL at week 48 (P=0.006). At 48 weeks, total cholesterol decreased by 0.24 mmol (P=0.02), high-density lipoprotein cholesterol by 0.15 mmol (P=0.0001) and alanine aminotransferase by 5.74 mg/dL (P=0.01). Paired baseline DNA and week 24 RNA mutations were unchanged. Mitochondrial DNA (copies/cell) content increased from 672+/-254 to 682+/-269. d4T area under the plasma concentration time curve (AUC) decreased by 31% (P=0.003) and C(max) by 44% (P=0.004). Clinical and laboratory parameters improved or were unchanged.

CONCLUSIONS

Reduced-dose d4T is effective with improved safety parameters.

GENOPHAR: a randomized study of plasma drug measurements in association with genotypic resistance testing and expert advice to optimize therapy in patients failing antiretroviral therapy

OBJECTIVES

To evaluate the benefits of therapeutic drug monitoring (TDM) in association with genotypic resistance testing and expert advice to optimize therapy in multiexperienced patients infected with HIV-1.

METHODS

Patients with a viral load>1000 HIV-1 RNA copies/mL and an unchanged antiretroviral therapy regimen over the last 3 months were randomized into two groups: a genotypic group (G) and a geno-pharmacological group (GP). Treatment was selected by an expert committee according to genotypic resistance testing (the G and GP groups) and TDM (the GP group) at week 4. Treatment could be modified at each visit according to toxicity, poor virological response and TDM. Results of TDM were withheld from the G group until week 12. The primary endpoint of the study was the percentage of patients with viral load<200 copies/mL at week 12.

RESULTS

A total of 134 patients were randomized in the study, with 67 in each group, and included in the intent-to-treat (ITT) analysis. At baseline, median values were as follows: viral load (log(10) copies/mL): G=4.1, GP=4.0; CD4 cell count (cells/microL): G=292, GP=294; and number of prior drugs: G=7, GP=8. The median number of resistance mutations was five in the G group [nucleoside reverse transcriptase inhibitors (NRTIs)=three; non-nucleoside reverse transcriptase inhibitors (NNRTIs)=one; protease inhibitors (PI)=one] and seven in the GP group (NRTI=four; NNRTI=two; PI=one). At week 8, treatment was adjusted according to the TDM in 13 of the 67 patients in the GP group (19%). By ITT missing equal failure analysis at week 12, and after only one intervention according to plasma concentration results, a viral load<200 copies/mL was achieved in 30 of the 67 patients (45%) in the G group and in 29 of the 67 patients (43%) in the GP group (not significant). In the multivariate analysis, only prior exposure to at least two PIs at baseline gave a poor response to subsequent antiretroviral therapy. At week 24, a viral load<200 copies/mL was achieved in 35 of the 67 patients (52%) in the G group and in 40 of the 67 patients (60%) in the GP group.

CONCLUSIONS

A statistically significant benefit of using TDM was not found in this short-term study where patients appeared to be adherent. However, combining genotypic resistance testing with the use of an expert committee to monitor subsequent therapy individually in patients with multiple resistance mutations was associated with high antiviral efficacy.

Impact of Insertions in the HIV-1 P6 Ptapp Region on the Virological Response to Amprenavir

We evaluated the impact of genetic changes within p6Gag gene on the virological response (VR, mean decrease in plasma viral load at week 12) to unboosted amprenavir (APV). Gag-protease fragments, including gag p2, p7, p1, p6 regions and whole protease (PR) were sequenced from baseline plasma specimens of 84 highly pre-treated but APV-naive patients included in the NARVAL (ANRS 088) trial. The correlation between baseline p6Gag polymorphism, PR mutations, baseline characteristics and VR to APV was analysed in univariate analysis. Insertions (P459Ins) within p6 protein, leading to partial or complete duplication of the PTAPP motif, were significantly associated with a decreased VR (P459Ins versus wild-type; –0.3 ±0.8 vs –1.1 ±1.2 log copies/ml, P=0.007) and were more frequent when the V82A/F/T/S PR mutation was present ( P=0.020). In multivariate analysis, after adjustment on the predictive factors of the VR in the NARVAL trial and on the PR mutations linked with response, there was a strong trend to an association ( P=0.058) between the presence of P459Ins and an altered VR. In conclusion, these results suggest that insertions in the p6 region of HIV-1 gag gene may affect the VR, in highly pre-treated patients receiving an unboosted APV-containing regimen.