Drug Resistance Among PrEP Recipients — How Big a Concern?

Charles B. Hicks, MD

Data from the iPrEx trial showed infrequent low-level resistance in those who became HIV-infected while taking pre-exposure prophylaxis.

Uptake of pre-exposure prophylaxis (PrEP) among individuals at risk for acquiring HIV infection has been slow despite clinical trial data showing efficacy in different populations. Reasons for this are multiple and complex, but one issue of concern is selection for antiretroviral-resistant virus in PrEP users who become HIV-infected. The Chemoprophylaxis for HIV Prevention in Men (iPrEx) study is a phase III clinical trial designed to determine whether daily tenofovir/ emtricitabine (FTC) can safely and effectively prevent HIV infection among men (and transgendered women) who have sex with men.

In this trial, 48 of the 1226 persons randomized to receive tenofovir/FTC acquired an incident HIV infection. Based on clinical drug-resistance assays, none of these infections were caused by a virus with tenofovir or FTC resistance mutations. However, ultrasensitive assays revealed low levels (frequencies <1%) of the M184I mutation in virus from two patients. Two additional patients who started PrEP with unrecognized acute HIV infection were infected with virus containing the M184V or I mutation.

Citation(s):

Liegler T et al. HIV-1 Drug resistance in the iPrEx preexposure prophylaxis trial. J Infect Dis 2014 Oct 15; 210:1217.