Pharmacological data of a successful 4-days-a-week regimen in HIV antiretroviral therapy (ANRS 162-4D trial)

Introduction: Few data are available on plasma concentrations of antiretroviral therapy (ARV) during intermittent treatment.

Objective: To compare plasma concentrations in OFF vs ON treatment periods at several time points during treatment.

Methods: During a successful 48-week multicenter study (ANRS 162-4D trial) of 4 days with treatment (ON) followed by 3 days without treatment (OFF) in adults treated by two nucleoside analogues and a third agent belonging to a boosted protease-inhibitor (PI, darunavir [DRV], atazanavir [ATV], lopinavir [LPV]) or a non-nucleoside-reverse-transcriptase inhibitor (NNRTI, efavirenz [EFV], etravirine [ETR], rilpivirine [RPV]) conducted in 100 patients (96% success), we determined the plasma concentrations of ARV. Blood samples were collected for analysis at inclusion (W0, 7/7 strategy for all patients), W16 and W40 (ON) and at W4, W8, W12, W24, W32 and W48 (OFF).

Results: A total of 866 samples was analysed. Plasma concentrations were not statistically lower after 4 days (ON) vs 7/7 days of treatment except for RPV (-30 ng/mL at 4/7, P = 0.003). Significant lower plasma concentrations were observed for OFF vs ON except for ETR (n = 5, P = 0.062). Overall, 87.1% of ON concentrations (ATV 92.1%, DRV 51.1%, LPV 62.5%, EFV 94.4%, ETR 100% and RPV 94.9%) and 21.8% of OFF concentrations (ATV 1.4%, DRV 0.0%, LPV 0.0%, EFV 16.0%, ETR 92.6% and RPV 39.0%) were above the theoretical limit of efficacy of the molecule. In the OFF period, 85.8% of PI concentrations were under the limit of quantification, while 98.0% of NNRTI concentrations were quantifiable.

Conclusion: Despite low/undetectable PI/NNRTI plasma concentrations in the OFF period, patients maintained an undetectable viral load. The mechanistic explanation should be investigated.