PREVAIL IV: Double-Blind, Randomized, Two-Phase, Placebo-Controlled, Phase II Trial of GS-5734 to Assess the Antiviral Activity, Longer-Term Clearance of Ebola Virus, and Safety in Male Ebola Survivors With Evidence of Ebola Virus Persistence in Semen

With the unprecedented size of the recent 2014-2016 West African Ebola outbreak, the scientific community is learning a great deal about the psychological and physical consequences of Ebola, Ebola viral persistence in survivors, risk of Ebola disease relapse in survivors, and the potential for survivors to transmit the virus to others. Data from PREVAIL III has demonstrated that persistence of Ebola virus in the semen of male survivors is common. In addition to Ebola virus persistence, Ebola relapse causing clinical disease has been well documented.

There are no licensed therapies for the treatment of Ebola virus disease nor for the clearance of persistent Ebola virus in survivors. A safe, effective therapy that can reduce and/or eliminate persistent Ebola virus from semen would reduce the risk of transmission and enable male survivors to resume normal sexual relations without fear of harming loved ones. The mechanism underlying Post-Ebola Syndrome is as yet unknown, but improvement in Post-Ebola signs and symptoms resulting from GS-5734 treatment would be an added benefit.

This study is a double-blind, randomized, two-phase (treatment and longer-term follow-up), two- arm trial of GS-5734 versus placebo among male Ebola survivors with persistent Ebola virus RNA in their semen. Participants are randomized 1:1 to receive either 100 mg of GS-5734 or placebo once daily by intravenous catheter for 5 days. Informed by transaminase elevations in prior Phase I studies in normal healthy subjects, a risk-mitigation strategy includes a built-in dose de-escalation. Participants will be stratified by country and on the basis of one versus two positive semen samples for Ebola virus RNA using the Cepheid GeneXpert platform assessed within 42 days prior to study enrollment. The early Data Safety and Monitoring Board (DSMB) review in August 2016 concluded there was no need for a cohort dose reduction. The protocol expanded to Guinea in October 2017, where the outbreak ended later. Currently there is an outbreak in the Democratic Republic of the Congo where the study team may evaluate conducting this study following the completion of the outbreak.

Antiviral activity, as well as safety and tolerability, will be assessed during the treatment phase. Longer-term clearance of Ebola virus will be assessed during the 5-month follow-up phase. Primary analyses for the assessment of antiviral activity in the treatment phase will focus on the assay negativity rate (ANR; percentage of genital samples that are negative for Ebola) over the first 28 days of the study, as well as clinical and laboratory adverse events. A sample is considered negative by PCR if the test result is undetectable. Primary analysis for the follow-up phase will focus on the ANR collected monthly from months 2 to 6.