Researchers in the Democratic Republic of Congo have launched a major clinical trial to evaluate whether Gilead Sciences’ experimental antiviral obeldesivir can prevent Ebola infection after exposure. The study, announced on Tuesday, comes as the Bundibugyo Ebola outbreak continues to affect eastern DR Congo and neighboring Uganda.
Health researchers in the Democratic Republic of Congo have begun enrolling participants in a landmark clinical trial testing the experimental antiviral drug obeldesivir as a post-exposure treatment for Ebola. The initiative aims to determine whether administering the antiviral shortly after exposure can stop the virus from causing disease, offering a potentially valuable new tool in outbreak control.
The trial is being led by the Democratic Republic of Congo’s National Institute for Biomedical Research (INRB) and France’s ANRS Emerging Infectious Diseases, with operational support from humanitarian organizations Alliance for International Medical Action (ALIMA) and Médecins Sans Frontières (MSF). It is taking place in Ituri province, the epicenter of the ongoing Bundibugyo Ebola outbreak.
Targeting those at highest risk
The study is designed to evaluate whether people who have recently been exposed to the Ebola virus are less likely to develop the disease if they receive obeldesivir soon after contact. Researchers plan to enroll around 1,000 participants aged 12 years and older who had high-risk exposure to a laboratory-confirmed Ebola case within the previous five days but who have not yet developed symptoms.
Participants will undergo close medical monitoring every day for 21 days, corresponding to the virus’s incubation period, before a final follow-up visit on day 42. The intensive monitoring will allow scientists to determine both the effectiveness and safety of the treatment while ensuring rapid medical care should symptoms develop.
Obeldesivir, developed by Gilead Sciences, has demonstrated activity against filoviruses, including the Bundibugyo strain of the Ebola virus, during pre-clinical studies. Researchers hope these encouraging laboratory findings will translate into protection for people exposed during real-world outbreaks.
Strengthening the outbreak response
The clinical trial forms part of a broader effort to improve the response to one of the region’s deadliest infectious disease emergencies. In addition to evaluating obeldesivir, the project includes a compassionate-use protocol under which Gilead’s injectable antiviral remdesivir will be offered to children under 12 years of age as well as pregnant and breastfeeding women who have been exposed to the virus, groups that are not included in the main study.
The research has secured significant international financial support. Initial funding includes €3.4 million from the Global Health EDCTP3 partnership, backed by the European Commission, alongside $1 million from the Africa Centers for Disease Control and Prevention. Africa CDC has also helped mobilize an additional $5 million in funding commitments from South Africa and the Democratic Republic of Congo.
The launch of the trial comes as the Bundibugyo Ebola outbreak continues to exact a heavy toll. According to Congolese government data, the epidemic has resulted in 1,963 confirmed cases, including 719 deaths. Researchers hope the findings will not only benefit the current response but also provide new evidence to guide future Ebola outbreak management across Africa, where rapid post-exposure treatment could become an important complement to existing surveillance, isolation and vaccination strategies.
