1. Using the adherence‐efficacy relationship of emtricitabine and tenofovir disoproxil fumarate to calculate background HIV incidence: a secondary analysis of a randomized, controlled trial
- Author
-
Glidden, David V, Das, Moupali, Dunn, David T, Ebrahimi, Ramin, Zhao, Yongwu, Stirrup, Oliver T, Baeten, Jared M, and Anderson, Peter L
- Subjects
HIV/AIDS ,Sexual and Gender Minorities (SGM/LGBT*) ,Prevention ,Clinical Trials and Supportive Activities ,Infectious Diseases ,Clinical Research ,6.1 Pharmaceuticals ,Evaluation of treatments and therapeutic interventions ,Infection ,Good Health and Well Being ,Anti-HIV Agents ,Bayes Theorem ,Emtricitabine ,Female ,HIV Infections ,Homosexuality ,Male ,Humans ,Male ,Pre-Exposure Prophylaxis ,Sexual and Gender Minorities ,Tenofovir ,counterfactual ,PrEP ,clinical trial design ,tenofovir alafenamide ,tenofovir disoproxil fumarate ,Bayesian inference ,Clinical Sciences ,Public Health and Health Services ,Other Medical and Health Sciences - Abstract
IntroductionRandomized trials of new agents for HIV pre-exposure prophylaxis (PrEP) compare against emtricitabine and tenofovir disoproxil fumarate (F/TDF), without a placebo group. We used the well-characterized adherence-efficacy relationship for F/TDF to back-calculate the (non-PrEP) counterfactual background HIV incidence (bHIV) in a randomized trial of a novel PrEP agent and estimate comparative efficacy (to counterfactual bHIV).MethodsThe DISCOVER trial (ClinicalTrials.gov: NCT02842086) randomized 5387 men who have sex with men (MSM) and transgender women who have sex with men and demonstrated non-inferiority of emtricitabine and tenofovir alafenamide (F/TAF) to F/TDF (HIV incidence rate ratio [IRR] 0·47, 95% CI: 0·19 to 1.15). Tenofovir diphosphate (TFV-DP) levels in dried blood spots (DBS) were assessed for all diagnosed with HIV and in a random 10% of the cohort. We used a Bayesian model with a diffuse prior distribution, derived from established data relating tenofovir diphosphate levels to HIV prevention efficacy. This prior, combined with the F/TDF seroconversion rate and tenofovir diphosphate levels in DISCOVER, yielded Bayesian inferences on the counterfactual bHIV.ResultsThere were six versus 11 postbaseline HIV infections (0.14 vs. 0.25/100 person-years [PY]) on F/TAF and F/TDF respectively. Of the 11 on F/TDF, 10 had low, none had medium and one had high tenofovir diphosphate levels; among HIV-negative controls, 5% of the person-time years had low, 9% had medium and 86% had high TFV-DP levels. A non-informative prior distribution for counterfactual bHIV, combined with the prior for TFV-DP level-efficacy relationship, yielded a posterior counterfactual bHIV of 3·4 infections/100 PY (0.80 Bayesian credible interval [CrI] 1·9 to 5·9), which suggests a median HIV efficacy of 96% (0.95 CrI [88% to 99%]) for F/TAF and 93% (0.95 CrI [87% to 96%]) for F/TDF compared to bHIV.ConclusionsBased on the established connection of drug concentrations to PrEP prevention efficacy, a Bayesian framework can be used to estimate a synthetic non-PrEP control group in randomized, active-controlled PrEP trials that include a F/TDF-comparator group.
- Published
- 2021