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Zivich PN, Cole SR, Edwards JK, Glidden DV, Das M, Shook-Sa BE, Shao Y, Mehrotra ML, Adimora AA, Eron JJ. HIV Prevention Among Men Who Have Sex With Men: Tenofovir Alafenamide Combination Preexposure Prophylaxis Versus Placebo. J Infect Dis 2024; 229:1123-1130. [PMID: 37969014 PMCID: PMC11011171 DOI: 10.1093/infdis/jiad507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 11/06/2023] [Accepted: 11/13/2023] [Indexed: 11/17/2023] Open
Abstract
BACKGROUND While noninferiority of tenofovir alafenamide and emtricitabine (TAF/FTC) as preexposure prophylaxis (PrEP) for the prevention of human immunodeficiency virus (HIV) has been shown, interest remains in its efficacy relative to placebo. We estimate the efficacy of TAF/FTC PrEP versus placebo for the prevention of HIV infection. METHODS We used data from the DISCOVER and iPrEx trials to compare TAF/FTC to placebo. DISCOVER was a noninferiority trial conducted from 2016 to 2017. iPrEx was a placebo-controlled trial conducted from 2007 to 2009. Inverse probability weights were used to standardize the iPrEx participants to the distribution of demographics and risk factors in the DISCOVER trial. To check the comparison, we evaluated whether risk of HIV infection in the shared tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) arms was similar. RESULTS Notable differences in demographics and risk factors occurred between trials. After standardization, the difference in risk of HIV infection between the TDF/FTC arms was near zero. The risk of HIV with TAF/FTC was 5.8 percentage points lower (95% confidence interval [CI], -2.0% to -9.6%) or 12.5-fold lower (95% CI, .02 to .31) than placebo standardized to the DISCOVER population. CONCLUSIONS There was a reduction in HIV infection with TAF/FTC versus placebo across 96 weeks of follow-up. CLINICAL TRIALS REGISTRATION NCT02842086 and NCT00458393.
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Affiliation(s)
- Paul N Zivich
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Institute of Global Health and Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Stephen R Cole
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jessie K Edwards
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - David V Glidden
- Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA
| | - Moupali Das
- Gilead Sciences, Foster City, California, USA
| | - Bonnie E Shook-Sa
- Department of Biostatistics, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Yongwu Shao
- Gilead Sciences, Foster City, California, USA
| | - Megha L Mehrotra
- Department of Epidemiology and Biostatistics, University of California, San Francisco, California, USA
- Gilead Sciences, Foster City, California, USA
| | - Adaora A Adimora
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Division of Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Joseph J Eron
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Division of Infectious Diseases, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
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Zhu Y, Gao F, Glidden DV, Donnell D, Janes H. Estimating counterfactual placebo HIV incidence in HIV prevention trials without placebo arms based on markers of HIV exposure. Clin Trials 2024; 21:114-123. [PMID: 37877356 PMCID: PMC11361381 DOI: 10.1177/17407745231203327] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
INTRODUCTION Developing alternative approaches to evaluating absolute efficacy of new HIV prevention interventions is a priority, as active-controlled designs, whereby individuals without HIV are randomized to the experimental intervention or an active control known to be effective, are increasing. With this design, however, the efficacy of the experimental intervention to prevent HIV acquisition relative to placebo cannot be evaluated directly. METHODS One proposed approach to estimate absolute prevention efficacy is to use an HIV exposure marker, such as incident rectal gonorrhea, to infer counterfactual placebo HIV incidence. We formalize a statistical framework for this approach, specify working regression and likelihood-based estimation approaches, lay out three assumptions under which valid inference can be achieved, evaluate finite-sample performance, and illustrate the approach using a recent active-controlled HIV prevention trial. RESULTS We find that in finite samples and under correctly specified assumptions accurate and precise estimates of counterfactual placebo incidence and prevention efficacy are produced. Based on data from the DISCOVER trial in men and transgender women who have sex with men, and assuming correctly specified assumptions, the estimated prevention efficacy for tenofovir alafenamide plus emtricitabine is 98.1% (95% confidence interval: 96.4%-99.4%) using the working model approach and 98.1% (95% confidence interval: 96.4%-99.7%) using the likelihood-based approach. CONCLUSION Careful assessment of the underlying assumptions, study of their violation, evaluation of the approach in trials with placebo arms, and advancement of improved exposure markers are needed before the HIV exposure marker approach can be relied upon in practice.
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Affiliation(s)
- Yifan Zhu
- Sanofi US, USA
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, USA
| | - Fei Gao
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, USA
| | - David V Glidden
- Department of Epidemiology and Biostatistics, University of California at San Francisco, USA
| | - Deborah Donnell
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, USA
| | - Holly Janes
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, USA
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Donnell D, Kansiime S, Glidden DV, Luedtke A, Gilbert PB, Gao F, Janes H. Study design approaches for future active-controlled HIV prevention trials. STATISTICAL COMMUNICATIONS IN INFECTIOUS DISEASES 2024; 15:20230002. [PMID: 38250627 PMCID: PMC10798828 DOI: 10.1515/scid-2023-0002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 12/30/2023] [Indexed: 01/23/2024]
Abstract
Objectives Vigorous discussions are ongoing about future efficacy trial designs of candidate human immunodeficiency virus (HIV) prevention interventions. The study design challenges of HIV prevention interventions are considerable given rapid evolution of the prevention landscape and evidence of multiple modalities of highly effective products; future trials will likely be 'active-controlled', i.e., not include a placebo arm. Thus, novel design approaches are needed to accurately assess new interventions against these highly effective active controls. Methods To discuss active control design challenges and identify solutions, an initial virtual workshop series was hosted and supported by the International AIDS Enterprise (October 2020-March 2021). Subsequent symposia discussions continue to advance these efforts. As the non-inferiority design is an important conceptual reference design for guiding active control trials, we adopt several of its principles in our proposed design approaches. Results We discuss six potential study design approaches for formally evaluating absolute prevention efficacy given data from an active-controlled HIV prevention trial including using data from: 1) a registrational cohort, 2) recency assays, 3) an external trial placebo arm, 4) a biomarker of HIV incidence/exposure, 5) an anti-retroviral drug concentration as a mediator of prevention efficacy, and 6) immune biomarkers as a mediator of prevention efficacy. Conclusions Our understanding of these proposed novel approaches to future trial designs remains incomplete and there are many future statistical research needs. Yet, each of these approaches, within the context of an active-controlled trial, have the potential to yield reliable evidence of efficacy for future biomedical interventions.
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Affiliation(s)
- Deborah Donnell
- Fred Hutchinson Cancer Center, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
| | - Sheila Kansiime
- Medical Research Council/Uganda Virus Research Council and London School of Hygiene and Tropical Medicine, Uganda Research Unit, Entebbe, Uganda
- Medical Research Council International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | | | | | - Peter B. Gilbert
- Fred Hutchinson Cancer Center, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
| | - Fei Gao
- Fred Hutchinson Cancer Center, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
| | - Holly Janes
- Fred Hutchinson Cancer Center, Seattle, WA, USA
- University of Washington, Seattle, WA, USA
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Abstract
PURPOSE OF REVIEW Ending the HIV epidemic will require the development of additional effective immune-mediated and nonimmune-mediated means of HIV prevention. Evaluating novel interventions requires large, controlled trials demonstrating efficacy. Recent advances in the field of HIV prevention necessitate new approaches to efficacy trial design. RECENT FINDINGS Three classes of efficacy trial designs are possible: standard of prevention-controlled trials, active-controlled trials, and active-controlled trials augmented with external control data. Recent experience with these approaches provides lessons on considerations around and success of the designs. Additional experience and development is needed for the augmented active-controlled trial design. SUMMARY Efficacy trials of new HIV prevention interventions are feasible but require careful consideration, given the complexity and dynamic state of the prevention field. While standard of prevention-controlled efficacy trials are reasonable approaches for HIV vaccine and monoclonal antibody efficacy trials, trials of new antiretroviral agents may require active-controlled designs.
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Affiliation(s)
- Holly Janes
- Fred Hutchinson Cancer Center
- University of Washington
| | - Susan Buchbinder
- San Francisco Department of Public Health
- University of California, San Francisco
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Moore M, Stansfield S, Donnell DJ, Boily MC, Mitchell KM, Anderson PL, Delany-Moretlwe S, Bekker LG, Mgodi NM, Celum CL, Dimitrov D. Efficacy estimates of oral pre-exposure prophylaxis for HIV prevention in cisgender women with partial adherence. Nat Med 2023; 29:2748-2752. [PMID: 37798438 PMCID: PMC11386520 DOI: 10.1038/s41591-023-02564-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 08/23/2023] [Indexed: 10/07/2023]
Abstract
Pre-exposure prophylaxis (PrEP) with tenofovir (TFV) disoproxil fumarate and emtricitabine administered orally daily is effective in preventing human immunodeficiency virus (HIV) acquisition in both men and women with sufficient adherence; however, the adherence-efficacy relationship in cisgender women has not been well established. We calculated the adherence-efficacy curve for cisgender women by using HIV incidence and plasma TFV concentration data from three trials (FEM-PrEP, VOICE and Partners PrEP). We imputed TFV diphosphate (TFV-DP) concentrations, a measure of long-term adherence, from TFV quantification by using data from the HIV Prevention Trials Network 082 study, which measured both TFV-DP and TFV concentrations. Two, four and seven pills per week reduced HIV incidence by 59.3% (95% credible interval (CrI) 29.9-95.8%), 83.8% (95% CI 51.7-99.8%) and 95.9% (95% CI 72.6-100%), respectively. Our adherence-efficacy curve can be validated and updated by HIV prevention studies that directly measure TFV-DP concentrations. The curve suggests that high adherence confers high protection in cisgender women. However, the lower efficacy with partial adherence highlights the need for new PrEP products and interventions to increase adherence.
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Affiliation(s)
- Mia Moore
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, Seattle, WA, USA.
- HPTN Modelling Centre, Imperial College London, London, UK.
| | - Sarah Stansfield
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- HPTN Modelling Centre, Imperial College London, London, UK
| | - Deborah J Donnell
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Marie-Claude Boily
- HPTN Modelling Centre, Imperial College London, London, UK
- Medical Research Council Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Kate M Mitchell
- HPTN Modelling Centre, Imperial College London, London, UK
- Medical Research Council Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, London, UK
| | - Peter L Anderson
- Anschutz Medical Campus, University of Colorado, Aurora, CO, USA
| | | | - Linda-Gail Bekker
- Desmond Tutu HIV Centre, University of Cape Town, Cape Town, South Africa
| | - Nyaradzo M Mgodi
- College of Health Sciences Clinical Trials Research Centre, University of Zimbabwe, Harare, Zimbabwe
| | - Connie L Celum
- Departments of Global Health, Medicine and Epidemiology, University of Washington, Seattle, WA, USA
| | - Dobromir Dimitrov
- Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Center, Seattle, WA, USA
- HPTN Modelling Centre, Imperial College London, London, UK
- Department of Applied Mathematics, University of Washington, Seattle, WA, USA
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Dunn DT, Stirrup OT, McCormack S, Glidden DV. Interpretation of active-control randomised trials: the case for a new analytical perspective involving averted events. BMC Med Res Methodol 2023; 23:149. [PMID: 37365584 DOI: 10.1186/s12874-023-01970-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 06/09/2023] [Indexed: 06/28/2023] Open
Abstract
Active-control trials, where an experimental treatment is compared with an established treatment, are performed when the inclusion of a placebo control group is deemed to be unethical. For time-to-event outcomes, the primary estimand is usually the rate ratio, or the closely-related hazard ratio, comparing the experimental group with the control group. In this article we describe major problems in the interpretation of this estimand, using examples from COVID-19 vaccine and HIV pre-exposure prophylaxis trials. In particular, when the control treatment is highly effective, the rate ratio may indicate that the experimental treatment is clearly statistically inferior even when it is worthwhile from a public health perspective. We argue that it is crucially important to consider averted events as well as observed events in the interpretation of active-control trials. An alternative metric that incorporates this information, the averted events ratio, is proposed and exemplified. Its interpretation is simple and conceptually appealing, namely the proportion of events that would be averted by using the experimental treatment rather than the control treatment. The averted events ratio cannot be directly estimated from the active-control trial, and requires an additional assumption about either: (a) the incidence that would have been observed in a hypothetical placebo arm (the counterfactual incidence) or (b) the efficacy of the control treatment (relative to no treatment) that pertained in the active-control trial. Although estimation of these parameters is not straightforward, this must be attempted in order to draw rational inferences. To date, this method has been applied only within HIV prevention research, but has wider applicability to treatment trials and other disease areas.
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Affiliation(s)
- David T Dunn
- Institute for Global Health, University College London, London, UK.
- MRC Clinical Trials Unit, University College London, 90 High Holborn, London, WC1V 6LJ, UK.
| | - Oliver T Stirrup
- Institute for Global Health, University College London, London, UK
| | - Sheena McCormack
- MRC Clinical Trials Unit, University College London, 90 High Holborn, London, WC1V 6LJ, UK
| | - David V Glidden
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA
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Donnell D, Gao F, Hughes JP, Hanscom B, Corey L, Cohen MS, Edupuganti S, Mgodi N, Rees H, Baeten JM, Gray G, Bekker L, Hosseinipour M, Delany‐Moretlwe S. Counterfactual estimation of efficacy against placebo for novel PrEP agents using external trial data: example of injectable cabotegravir and oral PrEP in women. J Int AIDS Soc 2023; 26:e26118. [PMID: 37363917 PMCID: PMC10292682 DOI: 10.1002/jia2.26118] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 05/12/2023] [Indexed: 06/28/2023] Open
Abstract
INTRODUCTION Multiple antiretroviral agents have demonstrated efficacy for human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP). As a result, clinical trials of novel agents have transitioned from placebo- to active-controlled designs; however, active-controlled trials do not provide an estimate of efficacy versus no use of PrEP. Counterfactual placebo comparisons using other data sources could be employed to provide this information. METHODS We compared the active-controlled study (HPTN 084) of injectable cabotegravir (CAB-LA) versus daily oral emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) among women from seven countries in Africa to three external, contemporaneous randomized HIV prevention trials from which we constructed counterfactual placebo estimates. We used direct standardization via analysis weights to achieve the same distribution of person-years between the external study and HPTN 084, across strata predictive of HIV risk (country and selected risk covariates). We estimated prevention efficacy against a counterfactual placebo to provide information on the use of CAB-LA and FTC/TDF compared to no intervention. We compared the counterfactual placebo findings for FTC/TDF to previous placebo-controlled trials, adjusted for observed adherence to daily pills. RESULTS Distribution of age and baseline prevalence of gonorrhoea and chlamydia were similar among matched counterfactual placebo and observed HPTN 084 arms after standardization. Counterfactual estimates of CAB-LA versus placebo in all three settings showed a consistent risk reduction of 93%-94%, with lower bounds of the confidence intervals above 72%. Observed adherence (quantifiable tenofovir in plasma) in HPTN 084 was 54%-56%, and estimated efficacy of daily oral FTC/TDF against a counterfactual placebo was consistent with a predicted risk reduction of 39%-40% for this level of daily pill use. CONCLUSIONS Counterfactual placebo rates of HIV acquisition derived from external trial data in similar locations and time can be used to support estimates of placebo-based efficacy of a novel HIV prevention agent. External trial data must be standardized to be representative of the clinical trial cohort testing the novel HIV prevention agent, accounting for confounders.
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Affiliation(s)
| | - Fei Gao
- Fred Hutchinson Cancer CenterSeattleWashingtonUSA
| | | | | | | | - Myron S. Cohen
- University of North CarolinaChapel HillNorth CarolinaUSA
| | | | - Nyaradzo Mgodi
- University of Zimbabwe Clinical Trials Research CentreHarareZimbabwe
| | | | | | - Glenda Gray
- South Africa Medical Research CouncilTygerbergSouth Africa
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Sullivan PS, Hall E, Bradley H, Sanchez T, Woodyatt CR, Russell ES. Estimating HIV Incident Diagnoses Among Men Who Have Sex With Men Eligible for Pre-exposure Prophylaxis but Not Taking It: Protocol and Feasibility Assessment of Data Sources and Methods. JMIR Res Protoc 2023; 12:e42267. [PMID: 36881450 PMCID: PMC10031441 DOI: 10.2196/42267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 12/27/2022] [Accepted: 01/20/2023] [Indexed: 03/08/2023] Open
Abstract
BACKGROUND HIV incidence estimates are published each year for all Ending the HIV Epidemic (EHE) counties, but they are not stratified by the demographic variables highly associated with risk of infection. Regularly updated estimates of HIV incident diagnoses available at local levels are required to monitor the epidemic in the United States over time and could contribute to background incidence rate estimates for alternative clinical trial designs for new HIV prevention products. OBJECTIVE We describe methods using existing, robust data sources within areas in the United States to reliably estimate longitudinal HIV incident diagnoses stratified by race and age categories among men who have sex with other men (MSM) eligible for pre-exposure prophylaxis (PrEP) but not taking it. METHODS This is a secondary analysis of existing data sources to develop new estimates of incident HIV diagnoses in MSM. We reviewed past methods used to estimate incident diagnoses and explored opportunities to improve these estimates. We will use existing surveillance data sources and population sizes of HIV PrEP-eligible MSM estimated from population-based data sources (eg, US Census data and pharmaceutical prescription databases) to develop metropolitan statistical area-level estimates of new HIV diagnoses among PrEP-eligible MSM. Required parameters are number of new diagnoses among MSM, estimates of MSM with an indication for PrEP, and prevalent PrEP use including median duration of use; these parameters will be stratified by jurisdiction and age group or race or ethnicity. Preliminary outputs will be available in 2023, and updated estimates will be produced annually thereafter. RESULTS Data to parameterize new HIV diagnoses among PrEP-eligible MSM are available with varying levels of public availability and timeliness. In early 2023, the most recent available data on new HIV diagnoses were from the 2020 HIV surveillance report, which reports 30,689 new HIV infections in 2020, and 24,724 of them occurred in an MSA with a population of ≥500,000. Updated estimates for PrEP coverage based on commercial pharmacy claims data through February 2023 will be generated. The rate of new HIV diagnoses among MSM can be estimated from new diagnoses within each demographic group (numerator) and the total person-time at risk of diagnosis for each group (denominator) by metropolitan statistical area and year. To estimate time at risk, the person-time of individuals on PrEP or person-time after incident HIV infection but before diagnosis should be removed from stratified population size estimates of the total number of person-years with indications for PrEP. CONCLUSIONS Reliable, serial, cross-sectional estimates for rates of new HIV diagnoses for MSM with PrEP indications can serve as benchmark community estimates of failures of HIV prevention and opportunities to improve services and will support public health epidemic monitoring and alternative clinical trial designs. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID) DERR1-10.2196/42267.
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Affiliation(s)
- Patrick Sean Sullivan
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, United States
| | - Eric Hall
- Department of Epidemiology, School of Public Health, Oregon Health Sciences University, Portland, OR, United States
| | - Heather Bradley
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, United States
| | - Travis Sanchez
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, United States
| | - Cory R Woodyatt
- Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, United States
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Parkin N, Gao F, Grebe E, Cutrell A, Das M, Donnell D, Duerr A, Glidden DV, Hughes JP, Murray J, Robertson MN, Zinserling J, Lau J, Miller V. Facilitating Next-Generation Pre-Exposure Prophylaxis Clinical Trials Using HIV Recent Infection Assays: A Consensus Statement from the Forum HIV Prevention Trial Design Project. Clin Pharmacol Ther 2022. [PMID: 36550769 DOI: 10.1002/cpt.2830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 12/08/2022] [Indexed: 12/24/2022]
Abstract
Standard-of-care HIV pre-exposure prophylaxis (PrEP) is highly efficacious, but uptake of and persistence on a daily oral pill is low in many settings. Evaluation of alternate PrEP products will require innovation to avoid the unpractically large sample sizes in noninferiority trials. We propose estimating HIV incidence in people not on PrEP as an external counterfactual to which on-PrEP incidence in trial subjects can be compared. HIV recent infection testing algorithms (RITAs), such as the limiting antigen avidity assay plus viral load used on specimens from untreated HIV positive people identified during screening, is one possible approach. Its feasibility is partly dependent on the sample size needed to ensure adequate power, which is impacted by RITA performance, the number of recent infections identified, the expected efficacy of the intervention, and other factors. Screening sample sizes to support detection of an 80% reduction in incidence for 3 key populations are more modest, and comparable to the number of participants in recent phase III PrEP trials. Sample sizes would be significantly larger in populations with lower incidence, where the false recency rate is higher or if PrEP efficacy is expected to be lower. Our proposed counterfactual approach appears to be feasible, offers high statistical power, and is nearly contemporaneous with the on-PrEP population. It will be important to monitor the performance of this approach during new product development for HIV prevention. If successful, it could be a model for preventive HIV vaccines and prevention of other infectious diseases.
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Affiliation(s)
- Neil Parkin
- Data First Consulting, Sebastopol, California, USA
| | - Fei Gao
- Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Eduard Grebe
- Vitalant Research Institute, San Francisco, California, USA.,Edward Grebe Consulting, Cape Town, South Africa
| | - Amy Cutrell
- ViiV Healthcare, Research Triangle Park, North Carolina, USA
| | - Moupali Das
- Gilead Sciences, Foster City, California, USA
| | - Deborah Donnell
- Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Ann Duerr
- Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | | | | | | | | | - Joerg Zinserling
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Joseph Lau
- Forum for Collaborative Research, Washington, DC, USA
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Clinical Considerations in the Selection of Preexposure Prophylaxis for HIV Prevention in Canada. CANADIAN JOURNAL OF INFECTIOUS DISEASES AND MEDICAL MICROBIOLOGY 2022; 2022:3913439. [PMID: 36081603 PMCID: PMC9448580 DOI: 10.1155/2022/3913439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 08/03/2022] [Indexed: 11/17/2022]
Abstract
According to the Public Health Agency of Canada, approximately 62,050 people were living with HIV in Canada in 2018, and of those, 13% were undiagnosed. Currently, no single strategy provides complete protection or is universally effective across all demographic groups at risk for HIV. However, HIV preexposure prophylaxis (PrEP) is the newest HIV prevention strategy that shows promise. To date, two products have received an indication for PrEP by Health Canada: emtricitabine/tenofovir disoproxil fumarate (Truvada®; FTC/TDF) and emtricitabine/tenofovir alafenamide (Descovy®; FTC/TAF). Despite the high efficacy of these PrEP intervention methods, access to PrEP in Canada remains low. Identifying and addressing barriers to PrEP access, especially in high-risk groups, are necessary to reduce HIV transmission in Canada. While guidelines published by the Center for Disease Control and Prevention (CDC) include FTC/TAF information, the efficacy of FTC/TAF for PrEP has not yet been considered in Canada's clinical practice guidelines. Thus, the current paper reviews data regarding the use of FTC/TDF and FTC/TAF for PrEP, which may be useful for Canadian healthcare providers when counseling and implementing HIV prevention methods. The authors highlight these data in relation to various at-risk populations and review ongoing clinical trials investigating novel PrEP agents. Overall, FTC/TDF PrEP is effective for many populations, including men who have sex with men, transgender women, heterosexuals with partners living with HIV, and people who use drugs. While there is fewer data reported on the efficacy of FTC/TAF to date, recent clinical trials have demonstrated noninferiority of FTC/TAF in comparison to FTC/TDF. Notably, as studies have shown that FTC/TAF maintains renal function and bone mineral density to a greater extent than FTC/TDF, FTC/TAF may be a safer option for patients experiencing renal and/or bone dysfunction, for those at risk of renal and bone complications, and for those who develop FTC/TDF-related adverse events.
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11
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Glidden DV, Das M, Dunn DT, Ebrahimi R, Zhao Y, Stirrup OT, Baeten JM, Anderson PL. Using the adherence-efficacy relationship of emtricitabine and tenofovir disoproxil fumarate to calculate background hiv incidence: a secondary analysis of a randomized, controlled trial. J Int AIDS Soc 2021; 24:e25744. [PMID: 34021709 PMCID: PMC8140182 DOI: 10.1002/jia2.25744] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 04/22/2021] [Accepted: 04/26/2021] [Indexed: 12/02/2022] Open
Abstract
INTRODUCTION Randomized 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). METHODS The 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. RESULTS There 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. CONCLUSIONS Based 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.
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Affiliation(s)
- David V Glidden
- School of MedicineUniversity of California San FranciscoSan FranciscoCAUSA
- Department of Epidemiology and BiostatisticsSan FranciscoCAUSA
| | | | - David T Dunn
- Centre for Clinical Research in Infection and Sexual HealthInstitute for Global HealthUniversity College LondonLondonUK
| | | | | | - Oliver T Stirrup
- Centre for Clinical Research in Infection and Sexual HealthInstitute for Global HealthUniversity College LondonLondonUK
| | | | - Peter L Anderson
- University of Colorado Denver ‐ Anschutz Medical CampusAuroraCOUSA
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