Phenotypic hypersusceptibility to non-nucleoside reverse transcriptase inhibitors in treatment-experienced HIV-infected patients: impact on virological response to efavirenz-based therapy

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.

The role of nevirapine in the treatment of HIV-1 disease

Nevirapine (Viramune, Boehringer Ingelheim) is a non-nucleoside reverse transcriptase (RT) inhibitor (NNRTI) effective in the treatment of HIV-1 infected antiretroviral-naive and -experienced patients. Some recent studies have suggested that nevirapine-based regimens may have an efficacy similar to protease inhibitor (PI)-based regimens, at least in naive patients with CD4+ > 200 microl, while it lacks the drawbacks inherent in PI-containing regimens, such as lipodystrophy and metabolic alterations. Switching from a PI-containing regimen to a nevirapine-containing regimen seems to retain the virological response to therapy and it may also limit or reverse the development of some metabolic disorders induced by PIs. Nevirapine is also effective in preventing mother-to-child transmission of HIV-1 disease and in the treatment of HIV-1 infected children. Nevirapine is well-tolerated, rash being the most common severe adverse effect observed. Hepatotoxicity may also appear with nevirapine, mainly in patients with chronic hepatitis C and/or altered liver function tests. This side effect may occasionally be life-threatening but it can be safely managed in most patients.