Immunological and Virological Outcomes of Patients Switched from LPV/r to ATV/r-Containing Second- Line Regimens

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.