Efficacy of Darunavir/ritonavir Maintenance Monotherapy in Patients with HIV-1 Viral Suppression: a Randomized Open-label, Noninferiority Trial, MONOI-ANRS 136

Background: Darunavir/ritonavir (darunavir/r) maintenance strategy, in patients with suppressed HIV RNA viremia, is a potential long-term strategy to avoid nucleoside analogue toxicities and to reduce costs.

Methods: MONOtherapy Inhibitor protease is a prospective, open-label, noninferiority, 96-week safety and efficacy trial in virologically suppressed patients on triple therapy who were randomized to a darunavir/r triple drug regimen or darunavir/r monotherapy. The primary endpoint was the proportion of patients with HIV RNA less than 400 copies/ml at week 48; treatment failure was defined as two consecutive HIV RNA more than 400 copies/ml (time to loss of virologic response) or any change in treatment. The trial had 80% power to show noninferiority for the monotherapy arm (delta =-10%, 90% confidence interval).

Results: A total of 242 patients were screened, 225 of whom were randomized. In the per protocol efficacy analysis, treatment success was 99% on darunavir/r triple drug versus 94% on darunavir/r monotherapy (delta = -4.9%, 90% confidence interval, from -9.1 to -0.8). Similar results were found in intent-to-treat population (92 versus 87.5%, delta = -4.5%, 90% confidence interval from -11.2 to 2.1). Three patients experienced virologic failure on darunavir/monotherapy and none on darunavir/r triple drug. No resistance to protease inhibitor emerged in patients with plasma viral load above 50 copies/ml. The two groups did not differ in the number of serious adverse events.

Conclusion: Darunavir/r monotherapy exhibited efficacy rate over 85% with concordant results in the magnitude of difference with darunavir/r triple drug regimen in both intent-to-treat and per protocol analyses, but discordant conclusions with respect to the noninferiority margin. Patients failing on darunavir/r monotherapy had no emergence of new darunavir resistance mutations preserving future treatment options.