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Research on vaccines and treatments for the Bundibugyo strain of the Ebola virus has taken on a new urgency. According to the Ministry of Health of the Democratic Republic of Congo (DRC), as of May 23, there were 101 confirmed cases and 10 deaths, along with 904 suspected cases and 119 suspected deaths. The outbreak remained active across three provinces and 11 affected health zones. In Uganda, two confirmed cases and one death have been reported.

“At present, there are no licensed vaccines or approved therapeutics specifically targeting Bundibugyo virus disease. The WHO [World Health Organization] and its partners are supporting accelerated research and development efforts to evaluate candidate vaccines and investigational therapeutics. Authorities in affected and at-risk countries are encouraged to establish regulatory approvals and operational readiness for clinical trials and emergency use of investigational countermeasures should they become available,” the WHO reiterated in a situation update issued on May 17.

Vaccine and Research Coordination

On May 19, WHO’s representative in the DRC, Anne Ancia, updated vaccine development efforts.

“Vaccines are only available for the Zaire strain, which was identified in 1976,” she said.

WHO and local health authorities are rushing more testing kits to the eastern DRC to identify cases of infection with Bundibugyo virus, a species of Ebola virus for which there are no vaccines or therapeutics.

A WHO technical advisory group was scheduled to meet on Tuesday afternoon “to provide further recommendation to the WHO and its Member States on which potential vaccine should be prioritized,” Ancia said.

The French National Agency for Research on HIV/AIDS and Emerging Infectious Diseases (ANRS MIE) has been designated by the WHO to coordinate the Collaborative Open Research Consortium focused on filoviruses to anticipate and respond to emerging health threats such as Ebola and Marburg.

According to a press release by the French National Institute of Health & Medical Research (Inserm), “as soon as the first cases were reported, the ANRS MIE, the WHO, and the Africa Centres for Disease Control and Prevention (Africa CDC) brought together experts to prepare for the rapid launch of clinical trials — particularly those focused on treatments and vaccines — and to define the scientific and operational priorities of the response.”

An international protocol called Partner has been activated to enable the rapid evaluation of treatments during an epidemic. At the same time, “studies are planned to monitor people exposed to the virus and test post-exposure prophylaxis strategies, including the EBO-PEP study sponsored by ANRS MIE. Work is also underway to enable the rapid deployment of vaccine trials, if necessary.”

ERVEBO Vaccine

The ERVEBO vaccine, used against another form of Ebola, the Zaire strain, is currently the only one approved and in stock. Animal data suggest that it may offer partial protection against Bundibugyo in the range of 70%-80%, but this has not been confirmed in humans.

Several vaccine candidates specifically targeting Bundibugyo are currently under development, such as rVSV-BDBV GP, which has demonstrated protection in animal studies, including after exposure. Other approaches aim to provide broader protection against multiple Ebola viruses; however, they are still in the early stages of research and are not yet available.

“In response to the current Bundibugyo Ebola virus outbreak in the Democratic Republic of Congo, the Oxford Vaccine Group (OVG) is working urgently with Oxford’s own Clinical BioManufacturing Facility and the Serum Institute of India Pvt. Ltd. (SIIPL) to rapidly produce and scale doses of our ChAdOx-based monovalent Bundibugyo Ebola virus candidate vaccine, ChAdOx1 BDBV. The ChAdOx platform, a type of viral vector vaccine, has previously demonstrated a vital role in the development of vaccines for emerging infectious diseases and in responding to outbreak scenarios. This platform underpinned the Oxford/AstraZeneca COVID-19 vaccine […]” OVG stated in a press release.

Treatment Candidates

Inserm also reported that several treatment candidates are under investigation, although clinical evidence remains limited.

“The most advanced candidate is a treatment based on two antibodies capable of neutralizing the virus, called MBP134, which has been tested in nonhuman primates with encouraging results. An optimized version, known as MBP431, has also been developed to remain active in the body for a longer period and be easier to administer, particularly via intramuscular injection. Tested in animals, this formulation could facilitate its use in the field, particularly among individuals who have recently been exposed to the virus, to prevent the development of the disease.”

Remdesivir, a drug already used to treat COVID, has shown antiviral activity against the Bundibugyo variant in laboratory studies.

Another candidate, an antiviral drug called obeldesivir, is also being studied. Administered orally, it could be particularly useful during an outbreak as it would be easier to distribute it quickly to exposed individuals. But here again, the available data remain limited for the time being.”

This story was translated from Univadis France, part of the Medscape Professional Network.