Etravirine: a review of its use in the management of treatment-experienced patients with HIV-1 infection.

Etravirine (Intelence®) is an orally administered next-generation non-nucleoside reverse transcriptase inhibitor (NNRTI). It is approved for the treatment of HIV-1 infection in treatment-experienced adult patients who have evidence of viral replication and are harbouring HIV-1 strains resistant to other antiretroviral (ARV) agents. In the US, etravirine must be used in combination with other ARV agents; in the EU, it must be used in combination with other ARV agents that include a boosted HIV-1 protease inhibitor. Etravirine shows good activity in vitro against most wild-type strains of HIV-1, as well as against several strains resistant to available NNRTIs. Furthermore, etravirine appears to present a higher barrier than first-generation NNRTIs against the development of drug resistance. Whereas the presence of a single mutation is sufficient to affect the virological response to efavirenz or nevirapine, the resistance profile of etravirine is more complex and a prediction of virological response may be calculated using a weighted genotypic score. Importantly, the most prevalent NNRTI-associated mutation, K103N, alone does not affect the etravirine response. In two identically designed randomized clinical trials, the addition of etravirine to an optimized background therapy (OBT) regimen improved virological responses to a greater extent than placebo plus OBT following 24 weeks' treatment in highly treatment-experienced adult patients with HIV-1 infection who had evidence of viral replication (HIV-1 RNA levels of >5000 copies/mL at baseline). Furthermore, pre-planned pooled analyses of the trials at 48 and 96 weeks showed that etravirine plus OBT provided durable virological suppression. Consistently higher virological response rates were observed for recipients of etravirine plus OBT than placebo plus OBT in a pre-specified subgroup analysis of baseline viral loads, CD4+ cell counts, HIV-1 subtype or the composition of background ARV therapy. Greater improvements from baseline in immunological outcomes were also observed for recipients of etravirine plus OBT compared with those receiving placebo plus OBT over the 96-week treatment period of the trials. When used as part of an OBT regimen in trials of up to 96 weeks duration, etravirine was well tolerated with an overall tolerabilty profile similar to that of placebo. The only treatment-emergent adverse event that occurred with a higher frequency for recipients of etravirine compared with placebo plus OBT was rash. In highly treatment-experienced patients with HIV-1 infection and evidence of viral replication, the addition of etravirine to an OBT regimen provides an effective and well tolerated treatment that leads to improvements in both virological and immunological outcomes.