Switch to Unboosted Atazanavir With Tenofovir Study
Status:
Completed
Trial end date:
2015-12-01
Target enrollment:
Participant gender:
Summary
A drug-drug interaction between the anti-HIV drugs tenofovir DF (TDF) and atazanavir (ATZ)
results in lower ATZ plasma levels when the drugs are given together, particularly in
patients not taking ritonavir to boost ATZ levels. Lower plasma drug levels may make the
anti-HIV regimen less effective in controlling the HIV virus levels in the blood. For this
reason, current treatment guidelines recommend that ATZ always be boosted with ritonavir in
regimens also containing TDF. However, withdrawal of ritonavir is often desirable given the
tolerability and toxicity issues with this agent, even at the low dose (100 mg daily) used to
boost ATZ. For example, ritonavir can cause stomach upset, nausea, diarrhea, high cholesterol
levels, and liver enzyme abnormalities.
However, there is evidence that plasma ATZ levels may not predict treatment success on
unboosted ATZ regimens, particularly among people whose plasma HIV virus is already under
control and unboosted ATZ is being used as a maintenance strategy. In the BC Centre for
Excellence in HIV/AIDS Drug Treatment Program (DTP), nearly 100 patients originally treated
with ritonavir-boosted ATZ + TDF (+ FTC or 3TC) are receiving successful maintenance therapy
with unboosted ATZ and the same TDF-based backbone.
The study will examine the hypothesis that switching to maintenance therapy with unboosted
ATZ 400mg daily will have similar 48-week virologic efficacy to continuing ATZ/ritonavir
300/100mg daily among HIV-infected adults with stable viral load suppression on regimens
comprising ATZ/ritonavir 300/100mg daily with TDF plus either FTC or 3TC, despite potentially
lower ATZ trough levels with the unboosted regimen. In other words, patients whose HIV viral
load is undetectable while receiving TDF (+FTC or 3TC) and ATZ/ritonavir will continue to
maintain an undetectable viral load after switching to unboosted ATZ without ritonavir, in
the same proportions as those continuing on their boosted ATZ/ritonavir regimen.