IAS 2019 — DISCOVER trial update suggests potential for HIV prophylaxis


  • Laura Vargas-Parada, Ph.D.
  • Conference Reports
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Takeaway 

  • The DISCOVER trial assessed if F/TAF, approved as HIV treatment, can also reduce risk of acquiring HIV. 
  • Update: researchers say F/TAF has faster onset and longer sustained duration of HIV protection vs F/TDF. 

Why this matters 

  • The only drug approved for HIV preexposure prophylaxis (PrEP) is F/TDF.
  • F/TAF is reported to be noninferior to F/TDF as PrEP among 5387 participants.

Study design 

  • Randomized, double blind, safety and efficacy noninferiority trial, 92 study sites, United States, Canada, Western Europe.
  • Compared HIV risk, sexually transmitted infection incidence, adherence, pharmacokinetics. 
  • Relationship between adherence and efficacy assessed in nested case-control study.

Key results  

  • Noninferiority confirmed with sensitivity analysis; incident rate ratio: 0.55 (95% CI, 0.20-1.48). 
  • Bayesian analysis showed a 96% (95% credible interval) probability that F/TAF is more effective than F/TDF.
  • Tenofovir diphosphate levels in peripheral blood mononuclear cells were 6.3-fold higher with F/TAF vs F/TDF and achieved 90% effective concentration faster.
  • 98% receiving F/TAF had intracellular drug concentrations above the threshold considered protective from HIV vs 65% receiving F/TDF. 
  • Estimating duration of protection with a range of trial and historic data, F/TAF provided a 60% longer duration.

Limitations

  • Preliminary data, no cost analysis, conference presentation without peer review.