Pre-exposure prophylaxis for HIV infection: what if it works?

Anecdotal reports are already circulating, of physicians prescribing tenofovir to patients at high risk of HIV infection, and of unregulated use of the drug at venues such as sex clubs and circuit parties.20 Even those who would provide pre-exposure prophylactic treatment, such as doctors and other healthcareproviders are unsure about appropriate indications.21 If present trials show efficacy of tenofovir (or tenofovir and emtricitabine) against HIV transmission, the pressure for immediate approval for prevention will be great. In studies of individuals with HIV taking combination antiretroviral therapy, this mutation was detected in 3-2% of people over 96 weeks of follow-up.22 Small phase I studies of tenofovir monotherapy in people with HIV did not show development of any drug resistance mutations with up to 28 days of treatment, but in macaques infected with simian immunodeficiency virus, ultrasensitive resistance tests showed rapid development of K65R in those with high viral loads given high doses of tenofovir.21 The K65R mutation also causes some resistance to other nucleoside reverse transcriptase inhibitors and increased susceptibility to zidovudine.