Abstract
OBJECTIVE: Although postmenopausal (post-M) women have behavioral and biological risk factors for HIV infection, the activity of preexposure prophylaxis (PrEP) agents in older adults has not been well studied. DESIGN: We used an ex-vivo approach to compare the tissue concentrations of tenofovir (TFV) diphosphate (TFVdp) and emtricitabine (FTC) triphosphate (FTCtp) in cervical tissues from premenopausal (pre-M) and post-M women. METHOD: Cervical explants from 16 pre-M and 11 post-M women were incubated in 10-300 μg/ml TFV or FTC for 24 h. Explants were then snap frozen in liquid nitrogen and stored until analysis. TFVdp and FTCtp were quantified using tandem liquid chromatography-mass spectrometry. RESULTS: Active metabolite concentrations of TFVdp were more than nine-fold lower in post-M explants (P < 0.05). The percentage of TFV converted to TFVdp in pre-M explants was 0.0038 [below the limit of quantification (BLQ)-0.5886] compared with 0.0004 (BLQ-0.0706) in post-M explants. The majority of FTCtp concentrations were BLQ. For both TFVdp and FTCtp, there was a trend for more unquantifiable concentrations in post-M vs. pre-M (TFV: 38 vs. 21%, P = 0.2; FTC: 71 vs. 52%, P = 0.2). CONCLUSION: These findings could have implications in the use of nucleotide-based PrEP strategies targeted to older women. If validated in vivo, lower exposures of active nucleoside/tide metabolites could mean post-M women need higher doses of TFV-based PrEP to achieve protective efficacy.