Ebola vaccine candidates are currently being evaluated in phase I–III clinical trials conducted in Africa, the EU and the US. Although preclinical development of candidate vaccines utilise different platforms, including inactivated viral particles, DNA vaccines, recombinant viral vectors, recombinant proteins, subunit proteins and virus-like particles, the most advanced vaccine candidates are based on viral vectors engineered to serve as antigen delivery platforms that encode the full length of the surface glycoprotein of the Ebola virus. Examples of viral vectors expressing ebolavirus glycoproteins include recombinant human adenovirus (Ad26), recombinant simian adenovirus (chimpanzee Ad3), recombinant vaccinia virus (MVA) and a live vesicular stomatitis virus (rVSV) used alone or in prime-booster regimens. The genus Ebolavirus, a member of the family of Filoviridae, is comprised of five distinct species: Bundibugyo (BDBV), Ebola virus (EBOV) (formerly designated as Zaire ebolavirus, ZEBOV), Reston (RESTV), Sudan (SUDV) and Taï Forest (TAFV). The EBOV and SUDV species are the predominant causes of most EVD outbreaks. Glycoproteins from the different filoviruses show a high degree of diversity at the nucleotide and amino acid levels (60-65% conservation), implying that vaccines for protection against different filovirus infections would have to express and induce an immune response to several glycoproteins and would optimally be multivalent encoding glycoproteins from different viral species into one vaccine regimen. Single dose or prime-boost regimens are being explored in ongoing clinical trials. To date, at least 15 EVD vaccines are being developed (in North America, Europe, Russia and China), with four main candidates in varying advanced stages of human testing. These include the two most advanced – rVSV-ZEBOV (Merck) and ChAd3-EBO Z (GSK) – as well as a prime-boost regimen of Ad26.ZEBOV and MVA-BN-Filo developed by J&J/Bavarian Nordic, and a recombinant particle made of EBOV glycoprotein produced in an insect cell line, developed by the biotech company Novavax. The two lead vaccine candidates started human clinical trials in September 2014 and data on their safety and immunogenicity profiles were ready by December-January, breaking all records in terms of vaccine trial Phase I timelines. WHO played a key role in this endeavor, by identifying and coordinating numerous trial sponsors to test the vaccines contemporaneously in the US, Canada, and several countries in Europe and Africa. These two vaccines are now in Phase II/III trials in the three affected countries. The trial collaborations underway are: a ring vaccination trial of VSV-EBOV in Guinea, organized through a large international consortium including WHO, MSF, Canada, Norway and universities in the UK, Switzerland and the US; and a cluster based, non-blinded, individually randomized trial of rVSV-ZEBOV in Sierra Leone under a Sierra Leonean-US-CDC collaboration. A Phase II trial of both vaccines was carried out in Liberia under a Liberian government – US-NIH collaboration. This trial was completed at the end of April, and it is not known if trials in Liberia will continue. In the meantime, phase II trials of the GSK vaccine are slated to start in Cameroon, Ghana, Mali, Nigeria and Senegal in the second half of 2015. Pharmaceutical companies developing the vaccines have committed to ramp up production capacity in case of proven vaccine efficacy and the need for deployment. This could be the fastest vaccine roll-out in history. A comprehensive list of the EVD clinical trials can be found on the WHO International Clinical Trials Registry.
Ebola outbreak in Republic Democratic of the Congo: switching from MEURI (Monitored Emergency Use of Unregistered and Investigational Interventions) to a RCT (Randomized Clinical Trial) for 4 experimental medications in the treatment of Ebola Virus Disease
An international research team has begun patient enrollment in a clinical trial testing multiple investigational Ebola therapies in the Democratic Republic of the Congo (DRC). The randomized, controlled trial is enrolling patients of any age with confirmed Ebola virus disease (EVD). The trial is conducted at a treatment unit in the city of Beni operated by ALIMA (The Alliance for International Medical Action), a medical humanitarian organization, that is making the difference in a very difficoult scenario: “the situation is worrying, as we are hospitalizing a higher number of cases and the majority of these new cases are patients who were not previously registered as known contacts,” said Dr. Rouafi Oummani, ALIMA’s medical coordinator in Beni.
The trial, which will expand to additional DRC districts, is organized through an international research consortium coordinated by the World Health Organization (WHO). It is led and funded by the National Institute for Biomedical Research (INRB), part of the DRC Ministry of Health, and the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health, and also involves several additional international partners.
“Combatting Ebola requires a comprehensive response that draws on the strengths of all areas of public health. Biomedical research can lead to critical new tools, such as potentially life-saving therapies,” said NIAID Director Anthony S. Fauci., M.D. “Through scientifically and ethically sound clinical trials, we hope to efficiently and definitively establish the safety and efficacy of these investigational Ebola treatments, offering new ways to save lives.”
After the end of the 9th EVD outbreak in RDC, on Aug. 1, 2018, the DRC Ministry of Health declared the country’s 10th outbreak of EVD. As of Nov. 25, 2018, 240 deaths out of 419 confirmed and probable cases of EVD have been reported in the northeastern provinces of North Kivu and Ituri. Under the leadership of the DRC Ministry of Health, the WHO has coordinated the outbreak response with several international partners. NIAID, along with the U.S. Centers for Disease Control and Prevention, the U.S. Agency for International Development (USAID), and other U.S. government partners, have provided guidance and support to the multi-sectoral outbreak response.
“We urgently need a safe and effective treatment for this deadly disease,” said DRC Minister of Health Oly Ilunga Kalenga, M.D., Ph.D. “As we face a 10th outbreak of Ebola, we hope this clinical trial will give us more information about how best to treat patients.”
The trial aims to compare mortality among patients who receive one of three investigational Ebola drugs with a control group of patients who receive the investigational monoclonal antibody cocktail treatment ZMapp, developed by Mapp Biopharmaceutical, Inc. The therapies being tested include: mAb114, a single monoclonal antibody developed by NIAID, with early support from the INRB; and remdesivir (also known as GS-5734), an antiviral drug developed by Gilead Sciences, Inc. The trial has been approved to begin enrolling patients in these three groups, and plans are underway to amend the trial to include REGN-EB3 (also known as REGN3470-3471-3479), a monoclonal antibody cocktail developed by Regeneron Pharmaceuticals, Inc.
The participating Ebola treatment units will continue to provide all participants with supportive care for EVD. Ebola care includes supportive oral and/or intravenous fluids, electrolyte replacement, maintaining oxygen status and blood pressure, and pain management.
The investigational treatments have varying levels of data to support their use from testing in the laboratory, animals, and humans. However, none has been approved for treating EVD. ZMapp is the only investigational treatment previously tested in a randomized, controlled efficacy trial. Results from that study, conducted in the U.S. and West Africa during the 2014 to 2016 outbreak, suggested that ZMapp appeared to be beneficial, but as the outbreak waned, the trial ultimately could not enroll enough participants to definitively establish the drug’s efficacy.
The investigational treatments also have been administered to most of the Ebola patients in the current outbreak in the DRC under an ethical framework developed by the WHO called Monitored Emergency Use of Unregistered and Investigational Interventions (MEURI). However, this emergency-use mechanism cannot yield generalizable evidence on how well the treatments work.
“A randomized, controlled clinical trial is necessary to obtain reliable data about the safety and efficacy of investigational Ebola treatments,” said H. Clifford Lane, M.D., director of NIAID’s Division of Clinical Research. “It is possible to conduct rigorous clinical research in an outbreak setting, and we anticipate this trial will provide useful data.”
Professor Jean-Jacques Muyembe-Tamfum, M.D., Ph.D. (which was part of the research team that investigated the first know outbreak of Ebola disease in 1976), director-general of the INRB, and Richard T. Davey, Jr., M.D., deputy director of NIAID’s Division of Clinical Research, are co-principal investigators for the study.
Trial participants will be randomly assigned to receive one of the investigational treatments by intravenous infusion. Site clinicians will monitor patients’ symptoms and take blood samples for laboratory tests. Patients will remain in the Ebola treatment unit until they fully recover from the disease. They will be asked to return to the clinic approximately two months after receiving treatment for a check-up and to provide additional blood samples for laboratory tests.
Plans are underway to expand the trial beyond the ALIMA site in Beni to additional Ebola treatment units operated by medical humanitarian organizations, including International Medical Corps. The trial also may be adapted to continue across more than one outbreak and in several countries. The number of participants enrolled in the trial ultimately will depend on the evolution of Ebola outbreaks. The study is designed to enroll 112 patients per arm, potentially over multiple outbreaks.
“This clinical trial marks a significant and important step forward for the DRC and our international partners,” said Dr. Muyembe. “We are eager to learn more about each of these investigational treatments as we continue to work tirelessly to identify new cases, trace contacts and control the spread of disease.”
An independent data and safety monitoring board will regularly review the study data. For more information, visit ClinicalTrials.gov and search identifier NCT03719586.