Background: Atazanavir/ritonavir (ATV/r) recently became the preferred protease inhibitor
(PI) for use in Nigeria since it is dosed once daily, which may improve treatment adherence and has
fewer side effects than lopinavir/ritonavir (LPV/r) - the most widely available PI in resource-limited
settings. We, therefore, aimed to evaluate the immunologic and virologic effects of switching patients
to an ATV/r-containing regimen.
Methods: In a large antiretroviral treatment programme at the Lagos University Teaching Hospital in Nigeria, 400 patients
were switched to ATV/r-based second-line ART. We conducted a retrospective evaluation of immunologic and virologic
outcomes following 24 months on the ATV/r regimens.
Results: Of the 400 patients switched to an ATV/r containing regimen, 255 were virologically suppressed on LPV/r prior
to switch, 107 were switched due to failure on a first-line regimen, 28 were on saquinavir/ritonavir (SQV/r)-based
regimen, while 10 were unintentionally switched while non-suppressed on a LPV/r-based regimen. Demonstrable and
sustained immunological responses were documented as the median (IQR) CD4+ cell count increased steadily from 466
(323) cells/mm3 at the time of switch to 490 (346) cells/mm3 at 6 months, and 504 (360) cells/mm3 at 24 months. Of 99
patients evaluated 12 months after ATV/r switch, 2 (2%) had detectable viral load (VL). None of the 26 (0%) in this group
evaluated at 24 months had detectable viral load.
In a comparison group of 576 patients who were maintained on LPV/r-based second line regimens, 359 (62.3%) had
undetectable viral loads. Of 318 patients with VL data 24 months later, 25 (7.9%) had detectable VL. There was no
significant difference between the proportion of patients maintained on LPV/r (7.9%) and those switched to ATV/r (0%)
in the development of virologic failure after 24 months of follow-up.
Conclusion: Among patients that were switched to ATV/r-containing regimens, we found improvements in
immunological responses and no increase in risk of virologic failure.