Effectiveness of half-a-tablet efavirenz plus 2 nucleos(t)ide reverse-transcriptase inhibitors as maintenance therapy with the guidance of therapeutic drug monitoring among virologically suppressed HIV-positive patients: A prospective study

Abstract

Background: Optimal efavirenz (EFV) dose that minimizes adverse effects while maintaining efficacy has yet to be elucidated. With a therapeutic drug monitoring (TDM)-guided strategy, we assessed the effectiveness of half-a-tablet EFV plus 2 nucleos(t)ide reverse-transcriptase inhibitors (NRTIs) in HIV-infected Taiwanese who had achieved viral suppression with full-dose (600 mg) EFV.

Methods: HIV-infected adults receiving EFV-containing regimens who had plasma mid-dose EFV concentration (C12) ≥2.0 mg/L and had plasma HIV RNA load (PVL) <200 copies/mL were enrolled in this single-arm, open-label study by reducing EFV to half-a-tablet daily. The primary endpoint was PVL <50 copies/ml in an intention-to-treat (ITT) population at week 48. The secondary endpoints were the plasma EFV C12, the proportion of patients with plasma EFV C12 <1.0 mg/L, PVL <50 copies/ml at week 96 and week 144.

Results: Between April 2013 and September 2016, 203 patients (93.6% male; median age, 39.0 years) were enrolled. The median EFV C12 before switch was 2.80 mg/L (interquartile range (IQR), 2.41-3.73), which decreased to 1.59 mg/L (IQR, 1.23-2.03) after switch with a reduction of 47.4% (IQR, 38.3-55.5%). In ITT analysis, 93.6%, 92.3% and 87.3% of the patients achieved PVL <50 copies/ml at weeks 48, 96 and 144, respectively. More than 70% of the patients reported alleviation of EFV-associated adverse effects following the switch.

Conclusion: Under the guidance of TDM, switch to half-a-tablet EFV plus 2 NRTIs is effective in maintaining viral suppression in HIV-infected Taiwanese with EFV C12 ≥ 2.0 mg/L.

Keywords: Combination antiretroviral therapy; Dose optimization; Non-nucleoside reverse-transcriptase inhibitor; Pharmacogenetics; Switch therapy.