Drug Resistance Among Adolescents and Young Adults with Virologic Failure of First-Line Antiretroviral Therapy and Response to Second-Line Treatment.

Barriers to sustainable virologic suppression (VS) of HIV-infected adolescents and young adults include drug resistance mutations (DRMs) and limited treatment options, which may impact the outcome of second-line antiretroviral therapy (ART). We sequenced plasma viral RNA from 74 adolescents and young adults (16-24 years) failing first-line ART at Newlands Clinic, Zimbabwe between October 2015 and December 2016. We evaluated first-line nucleoside reverse transcriptase inhibitor (NRTI) susceptibility scores to first- and second-line regimens. Boosted protease inhibitor (bPI)-based ART was provided and viral load (VL) monitored for ≥48 weeks. Fisher's exact test was used to evaluate factors associated with VS on second-line regimens, defined as VL <1,000 copies/mL (VS1,000) or <50 copies/mL (VS50). The 74 participants on first-line ART had a median [interquartile range (IQR)] age of 18 (16-21) years and 42 (57%) were female. The mean (±standard deviation) duration on ART was 5.5 (±3.06) years and the median (IQR) log10 VL was 4.26 (3.78-4.83) copies/mL. After switching to a second-line PI regimen, 88% suppressed to <1,000 copies/mL and 76% to <50 copies/mL at ≥48 weeks. A new NRTI was associated with increased VS50 (p = .031). These 74 adolescents and young adults failing first-line ART demonstrated high levels (97%) of DRMs, despite enhanced adherence counseling. Switching to new NRTIs in second-line improved VS. With the widespread adoption of generic dolutegravir, lamivudine and tenofovir combinations in Africa, genotyping to determine NRTI susceptibility, may be warranted.