The decision was taken on Tuesday (3 February) by the Trial Steering Committee, which includes the lead scientists from Liberia, the University of Oxford and Médecins Sans Frontières (MSF), to stop enrolling patients onto the clinical trial of brincidofovir with immediate effect.
Over the past few weeks the number of new cases of confirmed Ebola virus has been falling across West Africa. Last week (ending 25 January) the World Health Organization (WHO) confirmed that there were four new Ebola cases in Liberia out of a total 99 cases in the three worst-affected regions, the lowest tally since June 2014.
On Friday (30 January), following discussions with the US Food and Drug Administration (FDA), the pharmaceutical company Chimerix, which manufactures brincidofovir, unexpectedly announced that it would cease to participate in any current or future trials of brincidofovir for Ebola virus disease.
The current position is that there is no realistic prospect of the trial enrolling sufficient patients to be able to reach a conclusion about the efficacy of the drug. Therefore the trial has been terminated.
Professor Peter Horby from the University of Oxford, who was leading the brincidofovir trial, said: "The past weeks have brought the extremely positive news that Ebola infections are falling across West Africa, including in Liberia where our trial of brincidofovir was based. We’re delighted that infections are falling, but fewer patients makes it more difficult to carry out the robust scientific studies needed to ensure a new treatment will be safe and effective.
"On Friday Chimerix took the decision to withdraw from the trial, following discussions with the US FDA. It is now clear that we will not be able to complete our study of brincidofovir, leaving us no option but to stop enrolling to the study with immediate effect."
Dr Jeremy Farrar, Director of the Wellcome Trust, which is funding a multimillion-pound therapeutics platform for experimental Ebola treatments, including the brincidofovir study, said: "The WHO recently confirmed that new cases of Ebola had fallen below 100 in a week for the first time since the crisis reached its peak. This is testament to the extraordinary efforts of organisations like MSF and the doctors, nurses and volunteers who have worked in West Africa from the outset to bring this dreadful epidemic under control.
"We’re now at the stage when new interventions that could help to finally end the current outbreak, and prevent future ones, are ready to be tested in Africa. It’s therefore disappointing that the trial of this therapy cannot continue, but it is essential that other studies of potential treatments and vaccines continue and hopefully will still be able to deliver meaningful results for this and the inevitable future epidemics of Ebola. We must never be in a position again when we do not have diagnostics, treatments and vaccines for this terrible infection."
Dr Stephen Kennedy, a study investigator from the Pacific Institute for Research and Evaluation, Monrovia, Liberia, said: "With the current stride towards zero case in Liberia, there are now fewer cases to test therapeutic agents. There are now efforts in place to decommission many of the existing Ebola treatment units. Therefore, the ability to assess the potential of a therapeutic agent among positive cases remains a significant challenge. Accordingly, the scientific community will move on without any clear evidence regarding the role of brincidofovir in the management of Ebola."
The study was part of a £3.2m platform funded by the Wellcome Trust, which is coordinated by Professor Peter Horby of the University of Oxford. The aim of the platform is to enable multiple partners around the world to quickly establish clinical trials at existing Ebola treatment centres. The platform will continue to support the evaluation of other investigational products for the treatment of Ebola virus disease.