Seminal Tenofovir Concentrations, Viral Suppression, and Semen Quality With Tenofovir Alafenamide, Compared With Tenofovir Disoproxil Fumarate (Spanish HIV/AIDS Research Network, PreEC/RIS 40)

Background. This study assessed the penetration and efficacy of tenofovir alafenamide (TAF) in the male genital tract (MGT) and the semen quality of individuals infected with human immunodeficiency virus (HIV)-1 who were treated with a TAF-containing regimen. Methods. This was a prospective, open-label, single-arm study of 14 virologically-suppressed, HIV-1-infected men on stable antiretroviral therapy with elvitegravir, cobicistat, emtricitabine (E/C/F) and tenofovir disoproxil fumarate (TDF) who switched to E/C/F and TAF. At baseline (pre-switch) and at 12 weeks post-switch, we measured HIV-1 RNA in seminal plasma (SP) and blood plasma (BP), tenofovir (TFV) in SP and BP, and TFV-diphosphate (dp) in peripheral blood mononuclear cells (PBMCs) and seminal mononuclear cells (SMCs) at the end of the dosing interval (C-24h). Semen quality was assessed before switching and after 12 weeks on TAF. Results. With TAF, TFV C-24 was 11.9-fold higher in SP than in BP. This concentration was significantly lower than TFV C-24 in SP with TDF, but 9.6-fold higher than the 50% inhibitory concentration (IC50) (11.5 ng/mL). By contrast, the median TFV-dp concentration achieved with TAF in SMCs was 6% that of TFV-dp in PBMCs. The TFV-dp SMC:PBMC ratio was also significantly lower with TAF. Nonetheless, TFV-dp C-24 in SMC was comparable with TAF and TDF. All the patients had HIV-1 RNA <40 copies/mL in BP and SP at baseline and at 12 weeks post-switch. No significant differences were observed in semen quality between TAF and TDF. Conclusions. Extracellular and intracellular seminal TFV distribution differs between TAF and TDF. Nevertheless, both formulations, combined with elvitegravir/cobicistat/emtricitabine, maintained HIV-1 RNA suppression in semen. Differences in MGT distribution were not associated with differences in semen quality.