Although preexposure prophylaxis (PrEP) has achieved significant results in reducing the incidence of HIV in regions where it has been made available and implemented, it is not infallible. As a case report published February 2nd in The New England Journal of Medicine (NEJM) notes, “incident HIV is possible despite adherence to preexposure prophylaxis when persons are exposed to [regimen]-resistant virus.”
Because of their findings in a 43-year-old male treated with PrEP, the authors of the report-a team of physicians, pharmacists, and basic researchers from Maple Leaf Medical Clinic and St. Michael’s Hospital in Toronto; the University of Colorado Anschutz Medical Campus in Aurora, Colo.; and the British Columbia Centre for Excellence in HIV/AIDS in Vancouver-recommended that clinicians prescribing the regimen, which consists of emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF), urge enhanced surveillance for mutant HIV strains that may compromise PrEP’s effectiveness. They also call for increased patient education with regard to the importance of regimen adherence in efficacy.
PrEP, otherwise known as FTC/TDF (Truvada, Gilead), was approved by the US Food and Drug Administration in 2012 for HIV preexposure prophylaxis. Notably, the iPrEx study, published in December 2010, found that the regimen, when administered to HIV-negative men who have sex with men, reduced the incidence of infection by 44%. A follow-up study, published in July 2014, demonstrated that adherence to the prescribed regimen was vital to its efficacy, as is the case with most antiviral therapies.
Now the NEJM case report calls this into question.
Indeed, the 43-year-old male in the case, from Toronto, who indicated to his physicians that he had sex with men, thus making him at high-risk for HIV and a prime candidate for PrEP, was started on oral daily FTC/TDF in April 2013, 9 weeks after a negative HIV test and following a period of 3 months during which he abstained from sex. He underwent 7 HIV screening tests over the ensuing 21 months and, based on pharmacy dispensation records, he adhered “perfect[ly]” to the regimen for a period of 24 months.