Switching to bictegravir/emtricitabine/tenofovir alafenamide maintained HIV-1 RNA suppression in participants with archived antiretroviral resistance including M184V/I.

OBJECTIVES: Studies 1878 and 1844 demonstrated non-inferior efficacy of switching suppressed HIV-1-infected adults to bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) versus continuing boosted PI-based triple regimens or dolutegravir/abacavir/lamivudine (DTG/ABC/3TC). Here, detailed analyses of pre-existing resistance in the two BIC/FTC/TAF switch studies and efficacy at week 48 are described. METHODS: Pre-existing resistance was assessed from historical genotypes (documented resistance to study drugs was excluded) and by retrospective baseline proviral archive DNA genotyping from whole blood. Outcomes were based on HIV-1 RNA at week 48 with missing values imputed using the last on-treatment observation carried forward method. RESULTS: Cumulative pre-existing resistance data from historical and proviral genotypes were obtained for 95% (543/570) of participants who switched to BIC/FTC/TAF. Altogether, 40% (217/543) had one or more pre-existing primary resistance substitutions in protease, reverse transcriptase and/or integrase. Pre-switch NRTI resistance was detected in 16% (89/543) of BIC/FTC/TAF-treated participants, with M184V or M184I detected by proviral genotyping in 10% (54/543). At week 48, 98% (561/570) of all BIC/FTC/TAF-treated participants versus 98% (213/217) with pre-existing resistance and 96% (52/54) with archived M184V/I had HIV-1 RNA <50 copies/mL. No BIC/FTC/TAF-treated participants developed treatment-emergent resistance to study drugs. CONCLUSIONS: Pre-existing resistance substitutions, notably M184V/I, were unexpectedly common among suppressed participants who switched to BIC/FTC/TAF. High rates of virological suppression were maintained in the overall study population and in those with pre-existing resistance, including M184V/I, for up to 48 weeks of BIC/FTC/TAF treatment with no resistance development. These results indicate that BIC/FTC/TAF is an effective treatment option for suppressed patients, including those with evidence of archived NRTI resistance.

Repeat testing of low-level HIV-1 RNA: assay performance and implementation in clinical trials.

OBJECTIVE: Assess the performance of HIV-1 RNA repeat testing of stored samples in cases of low-level viremia during clinical trials. DESIGN: Prospective and retrospective analysis of randomized clinical trial samples and reference standards. METHODS: To evaluate assay variability of the Cobas AmpliPrep/Cobas TaqMan HIV-1 Test, v2.0, three separate sources of samples were utilized: the World Health Organization (WHO) HIV reference standard (assayed using 50 independent measurements at six viral loads <200 copies/ml), retrospective analysis of four to six aliquots of plasma samples from four clinical trial participants, and prospective repeat testing of 120 samples from participants in randomized trials with low-level viremia. RESULTS: The TaqMan assay on the WHO HIV-1 RNA standards at viral loads <200 copies/ml performed within the expected variability according to assay specifications. However, standards with low viral loads of 36 and 18 copies/ml reported values of ≥ 50 copies/ml in 66 and 18% of tests, respectively. In participants treated with antiretrovirals who had unexpected viremia of 50-200 copies/ml after achieving <50 copies/ml, retesting of multiple aliquots of stored plasma found <50 copies/ml in nearly all cases upon retesting (14/15; 93%). Repeat testing was prospectively implemented in four clinical trials for all samples with virologic rebound of 50-200 copies/ml (n = 120 samples from 92 participants) from which 42% (50/120) had a retest result of less than 50 copies/ml and 58% (70/120) retested ≥ 50 copies/ml. CONCLUSION: The TaqMan HIV-1 RNA assay shows variability around 50 copies/ml that affects clinical trial results and may impact clinical practice. In participants with a history of viral load suppression, unexpected low-level viremia may be because of assay variability rather than low drug adherence or true virologic failure. Retesting a stored aliquot of the same sample may differentiate between assay variability and virologic failure as the source of viremia. This retesting strategy could save time, money, and anxiety for patients and their providers, as well as decrease follow-up clinic visits without increasing the risk of virologic failure and resistance development.

The pharmacokinetic and pharmacodynamic interactions between buprenorphine/naloxone and elvitegravir/cobicistat in subjects receiving chronic buprenorphine/naloxone treatment.

BACKGROUND: Interactions between HIV and opioid-dependence therapies are known to occur. We sought to determine if such interactions occurred between buprenorphine/naloxone and elvitegravir boosted with cobicistat. METHODS: We performed a within-subject open-labeled pharmacokinetic and pharmacodynamic study in 17 HIV-seronegative subjects stabilized on at least 2 weeks of buprenorphine/naloxone therapy. Subjects underwent baseline and steady state evaluation of the effect of elvitegravir 150 mg once daily boosted with 150 mg once daily of cobicistat (EVG/COBI) on buprenorphine/naloxone parameters. Safety was monitored throughout the study. RESULTS: Compared with baseline values, buprenorphine mean AUCtau (69.0 versus 95.6 hr*ng/mL) and mean Cmax (8.4 versus 9.3 ng/mL) increased significantly in the presence of EVG/COBI. Compared with baseline values, norbuprenorphine mean AUCtau (103.4 versus 163.4 hr*ng/mL) and mean Cmax (6.9 versus 9 ng/mL) also increased significantly after achieving steady state EVG/COBI. Naloxone mean AUCtau (0.57 versus 0.45 hr*ng/mL) and mean Cmax (0.25 versus 0.16 ng/mL) decreased after the addition of EVG/COBI. The AUCtau, Cmax and Ctau of EVG and cobicistat did not significantly differ from historical controls. Opioid withdrawal or overdose was not observed among subjects in this study. CONCLUSION: The addition of EVG/COBI to stabilized patients receiving buprenorphine/naloxone modestly increased buprenorphine and norbuprenorphine levels without affecting the opioid pharmacodynamics.