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Differences in emergence of HIV resistance between subtypes B and C in vitro and potential implications on tenofovir alafenamide efficacy in vivo were evaluated. Dose escalation resistance selections showed K65R emerging earlier for subtype C viruses in vitro, as previously reported. Viral breakthrough experiments at therapeutic drug concentrations, however, showed no difference in time to breakthrough between these subtypes. Finally, clinical trial data found no evidence of greater K65R emergence in patients harboring subtype C HIV.

We previously demonstrated superior efficacy and safety advantages in HIV-infected, virologically suppressed adults switched to a regimen containing tenofovir alafenamide (TAF) as compared with those remaining on a tenofovir disoproxil fumarate (TDF) regimen through week 48. We now report long-term data through week 96. In this randomized, active-controlled, multicenter, open-label, noninferiority trial (ClinicalTrials.gov No. NCT01815736), we randomized virologically suppressed (HIV-1 RNA50 copies/ml) adults (2:1) to receive a once-daily, single-tablet regimen containing elvitegravir (EVG), cobicistat (COBI), emtricitabine (FTC), and TAF group or to continue one of four TDF-containing regimens (TDF group) for 96 weeks. We evaluated efficacy (HIV-1 RNA50 copies/ml using the FDA snapshot algorithm) and prespecified bone and renal endpoints at week 96. We randomized and treated 1,436 participants in this study (TAF n = 959, TDF n = 477). At week 96, TAF was superior to TDF in virologic efficacy, with 93% on TAF and 89% on TDF having HIV-1 RNA50 copies/ml (difference 3.7%, 95% confidence interval: 0.4%-7.0%). Improvements in hip and spine bone mineral density for those assigned to TAF versus TDF continued through week 96 (p .001). Significant improvements in urine protein or albumin to creatinine ratios were also seen among those in the TAF group versus TDF through week 96 (p .001). There were no cases of investigator-reported proximal renal tubulopathy in the TAF group as compared with one case in the TDF group. Switching to EVG/COBI/FTC/TAF (E/C/F/TAF) was associated with statistically significant efficacy and safety advantages over remaining on a standard-of-care TDF-based regimen.

New antiretroviral drugs with activity against strains of human immunodeficiency virus type 1 (HIV-1) with non-B subtypes and with resistance to current antiretroviral drugs are needed. The activity of two nucleotide analogs, tenofovir and adefovir (PMPA and PMEA, respectively), against non-B subtypes and nucleoside-resistant primary HIV-1 isolates was assessed. Tenofovir and adefovir were fully active against a panel of subtypes A, C, D, E, F, G, and group O primary HIV-1 isolates as compared with their respective activity against subtype B isolates. Moreover, the susceptibility of a panel of 10 primary HIV-1 isolates with >10-fold mean resistance to zidovudine, lamivudine, and abacavir was within 2.2-fold of wild-type tenofovir susceptibility for each isolate. An oral prodrug of tenofovir, tenofovir disoproxil fumarate (DF), is currently in phase III clinical trials for the treatment of HIV-1 infection. These in vitro susceptibility results suggest that tenofovir DF may be active in vivo against HIV-1 with nucleoside resistance as well as against HIV-1 with non-B subtypes.