The Use of Efavirenz As a Part of Late Rescue Antiretroviral Treatment

Abstract

Purpose: Because rescue antiretroviral strategies are increasingly needed, patients’ response to a late salvage treatment including efavirenz plus a novel protease inhibitor (PI), with or without at least one novel nucleoside analogue, was assessed. Method: 41 consecutive patients, who underwent four or more prior therapeutic failures and received nucleoside analogues alone for ≥ 18 months and a PI-based HAART for ≥ 15 months, had a 12- to 24-month prospective follow-up. 6 patients who interrupted treatment after 3-8 weeks because of side effects were excluded. In the remaining 35 evaluable participants, the efavirenz-containing rescue regimen included nelfinavir in 23 cases, indinavir in 7, ritonavir in 2, and ritonavir plus hard gel saquinavir in the remaining 3 cases. 17 of 35 patients concurrently introduced one or more novel nucleoside analogues. Initial mean viremia was 4.8 ± 0.9 log₁₀ HIV RNA copies/mL, while mean baseline CD4+ lymphocyte count was around 100 cells/μL. Genotyping resistance testing was obtained at the time of treatment modification. Results: The virologic response was both limited and transient. A significant drop of mean viremia was reached at the third month (-0.7 log₁₀), but it was not maintained beyond the sixth month; only 4 patients reached viral suppression during the first 6 months. A more evident and sustained benefit on CD4+ cell count was observed throughout the study (p < .007, compared with baseline). The 31 patients who remained evaluable beyond 12 months did not show relevant modifications of laboratory parameters. The patient subgroup that received ≥ 1 novel nucleoside analogue at the time of efavirenz adjunct had a significantly more favorable virologic outcome until the ninth month of follow-up and included all cases who reached viral suppression. Antiviral resistance pattern showed frequent mutations of the protease gene, and a cross-resistance with nonnucleoside reverse transcriptase inhibitors (NNRTIs; found in 19 cases of 41), although our patients were not previously exposed to these compounds. Conclusion: A late salvage therapy based on efavirenz plus a novel PI is not expected to achieve a complete and sustained virologic success in patients highly experienced with both nucleoside analogues and PIs and with a concurrent elevated viremia, probably due to extensive resistances acquired through time. Our rate of virologic failure proved even greater than that observed in previous studies of salvage therapy including NNRTIs. Prior long-term treatment with isolated nucleoside analogues and HAART, the use of highly sensitive techniques for monitoring of viremia, and a quite prolonged observation period may have played a role. However, the CD4+ response proved to be more evident and sustained than the virologic one, and the concurrent introduction of ≥ 1 nucleoside analogue added significantly, especially during the first 9 months of salvage therapy.

Keywords:

• efavirenz
• HIV infection
• rescue treatment