Treating HIV: Pre-exposure Prophylaxis

Ellie Kamarjian, PharmD Candidate 2015 Mercer University College of Pharmacy

Pre-exposure prophylaxis is a prevention option for people who are at high risk of getting human immunodeficiency virus (HIV). The Centers for Disease Control and Prevention (CDC) recommends taking Truvada® (tenofovir and emtricitabine) daily as a pre-exposure prophylaxis. Truvada® reduced the risk of getting HIV infection by up to 92% for those who took the medicines consistently than for those who didn’t.1

Table 12

Title: Tenofovir-Based Pre-exposure Prophylaxis for HIV Infection among African Women
Design Randomized, placebo-controlled trial
Objective To assess daily treatment with tenofovir-based pre-exposure prophylaxis against HIV type 1 (HIV-1) infection in women in South Africa, Uganda, and Zimbabwe
Study Groups Five study groups: Oral tenofovir disoproxil fumarate (TDF) 300 mg with a TDF-FTC placebo, oral tenofovir-emtricitabine (TDF-FTC) 300 mg of TDF and 200 mg of FTC) with TDF placebo, both TDF-FTC placebo and TDF placebo, one percent tenofovir (TFV) vaginal gel, or vaginal placebo gel
Methods Participants (N = 5029) were randomly assigned in a 1:1:1:1:1 to one of the five regimens. Patients were counseled to use products daily. HIV-1 testing was performed monthly, and plasma TFV levels were assessed quarterly. Patients were followed for eight weeks after the last visit.
Duration September 2009 through August 2012
Primary Outcome Measure HIV-1 Infection identified by seroconversion
Baseline Characteristics Mean age was 25.3 years, 21% of women were married, and 71% were using injectable hormonal contraception with a reported mean of 2.5 episodes of vaginal intercourse during the seven days before enrollment
Results A total of 312 HIV-1 infections occurred; the incidence of HIV-1 infection was 5.7 per 100 person-years. The incidence was highest among participants who were younger than 25 years of age and among those who were unmarried.   Fifty-two occurred in the TDF group, 61 in the oral placebo group, and 70 in the placebo gel group. In the modified intention-to-treat analysis, the effectiveness was -49.0% with TDF (hazard ratio for infection, 1.49; 95% confidence interval [CI], 0.97 to 2.29), -4.4% with TDF-FTC (hazard ratio, 1.04; 95% CI, 0.73 to 1.49), and 14.5% with TFV gel (hazard ratio, 0.85; 95%CI, 0.61 to 1.21). In a random sample, TFV was detected in 30%, 29%, and 25% of available plasma samples from participants randomly assigned to receive TDF, TDF-FTC, and TFV gel, respectively.
Adverse Events Common Adverse Events: Elevated serum creatinine levels were seen more frequently among participants randomly assigned to the oral TDF-FTC group than among those in the oral placebo group (1.3% vs. 0.2%, p = 0.004); all but one of these elevations were mild
Serious Adverse Events: None reported
Percentage that Discontinued due to Adverse Events: None reported
Study Author Conclusions None of the drug regimens evaluated reduced the rates of HIV-1 acquisition in an intention-to-treat analysis. The adherence to study drugs was low.

Despite having adequate access to therapy, counseling, and treatments, adherence was very low for patients in this trial. Since the use of medication therapy for the pre-exposure prophylaxis of HIV infection relies heavily on patient compliance, this study was unable to show that therapy with tenofovir was beneficial. Ultimately, until adherence can be improved, pre-exposure benefits are improbable.

References:

  1. HIV Basics. Centers for Disease Control and Prevention website. Available at: http://www.cdc.gov/hiv/basics/prep.html. Accessed February 10, 2015.
  2. Marrazzo JM, Ramjee G, Richardson BA, et al. Tenofovir-based preexposure prophylaxis for HIV infection among African women. N Engl J Med. 2015; 372(6)509-518.
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