Limited Impact of First-Line Drug Resistance Mutations on Virologic Response Among Patients Receiving Second-Line Antiretroviral Therapy in Rural Uganda.

Background: Delayed detection of ART failure in settings without access to viral load (VL) monitoring has been hypothesized to lead to suboptimal response to second-line therapy due to accumulated drug resistance mutations (DRMs). We tested this hypothesis in a program setting in rural Uganda.

Methods: From June 2012 to January 2014, we enrolled participants receiving nonnucleoside reverse transcriptase inhibitor-based first-line ART for ≥4 years, without access to VL monitoring. Participants who had a measured VL ≥ 1000 copies/mL on two occasions were switched to protease inhibitor-based regimens and followed every 6 months until September 2016. We measured VL at study exit. We conducted DRM testing at enrollment and study exit and examined factors associated with virologic failure.

Results: We enrolled 137 participants (64.3% female) with a median age of 44 years and a median duration on ART of 6.0 years. In a median of 2.8 years of follow-up, 7 (5%) died, 5 (3.6%) voluntarily withdrew, and 9 (6.6%) became lost to follow-up. Of 116 participants with a VL result at study exit, 20 (17%) had VL > 1000 copies/mL. Virologic failure was associated with reporting suboptimal adherence ( P = 0.028). Of patients with DRM data at enrollment, 103 of 105 (98%) had at least 1 DRM. Participants with thymidine analog mutations at enrollment were less likely to have virologic failure at study exit (11% vs. 36%; P = 0.007). No other DRMs were associated with failure.

Conclusion: Even in the presence of multiple DRMs on first-line therapy, virologic failure after 3 years of protease inhibitor-based ART was infrequent. Suboptimal adherence to ART was associated with virologic failure.