Long-term follow-up of patients taking tenofovir DF with low-level HIV-1 viremia and the K65R substitution in HIV-1 RT.

Patients with on-going HIV-1 replication and a K65R mutation in HIV-1 RT were assessed for further development of RT mutations while taking tenofovir disoproxil fumarate and other antiretroviral drugs. K65R was observed in 10 out of 536 treatment-experienced patients entering the study. K65R became undetectable in two patients, and the development of additional resistance mutations was minimal. Over 18 months, no patient developed multinucleoside resistance (Q151M or T69 insertions) and plasma viral loads were stable (median +0.04 log10 copies/ml).