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.

Drug-Class-Wide Resistance to Antiretrovirals in HIV-Infected Patients Failing Therapy: Prevalence, Risk Factors and Virological Outcome

Background

Drug-class-wide resistance (DCWR) to anti-retrovirals substantially reduces treatment options.

Methods

A database of 602 patients failing highly active antiretroviral therapy (HAART) undergoing genotypic resistance test (GRT) was analysed. DCWR was defined according to the International AIDS Society consensus. A multiple logistic regression model was built to define factors significantly associated with DCWR and to assess virological response to salvage regimens.

Results

NRTI DCWR was observed in 28.5% of 592 NRTI-exposed patients, NNRTI DCWR in 57.7% of 284 NNRTI exposed patients, PI DCWR in 19.9% of 412 PI exposed patients, and three-class resistance in 21.4% of 112 three-class-exposed patients. The prevalence of NRTI and PI DCWR increased significantly by year of exposure to the same class from 8.9% (<1 year) to 35.3% (>4 years) and from 1.2% (<1 year) to 34.8% (>4 years), respectively ( P<0.001, for trend). The risk of developing NRTI and PI DCWR increased by 25% (95% confidence interval [CI]: 1.6%–51.3%) and by 53% (20.5%–94.3%) for each year of treatment, and by 17% (95% CI: 5.6%–29.3%) and by 32% (17.7%–50.3%) for each previous failing NRTI- and PI-containing regimen, respectively. NRTI DCWR due to at least four nucleoside analogues mutations (NAMs) increased by year of NRTI exposure from 8.9% (<1 year) to 32.6% (>4 years; P<0.001, for trend). After adjustment for confounding factors, the probability of achieving plasma viral load <500 copies/ml was significantly reduced in patients with NRTI (OR: 0.750; 95% CI: 0.574–0.979), NNRTI (OR: 0.746; 95% CI: 0.572–0.975), PI (OR: 0.655; 95% CI: 0.456–0.941), three-class (OR: 0.220; 95% CI: 0.082–0.593) resistance.

Conclusions

The probability of developing NRTI and PI DCWR increased with length of class exposure and with the number of previously failing regimens. By contrast, high levels of NNRTI DCWR were observed within 1 year in NNRTI-failing patients, with a steady prevalence over time. The increase in prevalence with time of NRTI DCWR was due to the accumulation of NAMs. DCWR to NRTIs, NNRTIs, PIs or all the three together was associated with an increased probability of virological failure to subsequent HAART regimens.