By Mariam Sunny and Jennifer Rigby
May 21 (Reuters) – Global health authorities are racing to identify medical options to help contain an Ebola outbreak in eastern Democratic Republic of Congo linked to the Bundibugyo strain of the virus.
Unlike the more common Zaire strain, there are no approved vaccines or treatments for Bundibugyo.
About 600 suspected cases and 139 suspected deaths have been reported in the outbreak, and the World Health Organization has warned the numbers are likely to rise. Bundibugyo ebolavirus (BDBV) has a fatality rate of up to 40%.
A small number of experimental vaccines and therapies are being assessed, and global health authorities are examining whether any existing Ebola medical options might offer protection – so far supported only by limited animal data.
Most candidates have not yet been tested in humans and would require emergency or compassionate-use authorization for deployment in DRC.
Here is what we know so far:
VACCINES
1. A Bundibugyo-specific vaccine, rVSVΔG/BDBV-GP, which uses the same technology as Merck’s approved vaccine Ervebo for the Ebola Zaire strain, has shown survival benefit in non-human primates in a 2023 proof-of-concept study.
A spokesperson for the University of Texas Medical Branch, whose researchers were involved in the study, said discussions are ongoing to advance the vaccine, but nothing has been finalized. The WHO has indicated a potential six-to-nine-month timeline to manufacture an rVSV Bundibugyo vaccine.
2. Another potential vaccine candidate based on ChAdOx1 technology, which was used in the Oxford/AstraZeneca COVID-19 vaccine, is being manufactured by the Serum Institute of India.
The company started production under its “emergency response framework”, alongside partners Coalition for Epidemic Preparedness Innovations and the University of Oxford, as soon as it got word of the outbreak this month, a spokesperson said.
Doses could be ready within two to three months, the WHO said, though animal studies have yet to be conducted, so more testing is needed.
CEPI, which funded some of the early COVID-19 vaccines and aims to have shots available within 100 days of an outbreak, said it is in talks with both candidates about how to speed up development, which would likely focus on conducting pre-clinical studies at the same time as manufacturing more doses.
ANTIBODY-BASED THERAPIES
1. Privately held Mapp Biopharmaceutical is developing a pan-ebolavirus antibody drug involving a combination of two human monoclonal antibodies, MBP134.
Initially studied for Sudan ebolavirus, the drug was found to be safe and well-tolerated in early-stage trials. Development has been backed by the U.S. Biomedical Advanced Research and Development Authority, known as BARDA.
The agency said it is coordinating shipments of the investigational treatment for potential use in high-risk Americans exposed to the virus.
Mapp said MBP134 has shown similar activity against all known ebolaviruses and that it is working with the World Health Organization and other authorities as part of the response to the Congo outbreak.
2. Human monoclonal antibodies isolated from Bundibugyo survivors have also been explored as potential treatments.
One candidate, BDBV289-N, demonstrated efficacy in a 2018 animal study. The study, conducted by a group of researchers with support from the U.S. National Institutes of Health, showed the antibody gave up to 100% protection in infected monkeys, even when treatment started up to eight days after infection.
ANTIVIRAL DRUGS
Gilead Sciences’ antiviral drug, remdesivir, has shown activity against the Bundibugyo virus in laboratory studies conducted by researchers at the University of Texas Medical Branch. Some data suggest it may have stronger activity against BDBV than against the Zaire Ebola strain.
Gilead did not respond to a request for comment.
DIAGNOSTIC TESTS
The WHO had indicated that limited testing capacity for the Bundibugyo strain was slowing the response to the outbreak. Here are tests that can detect the infection.
1. BioFire Defense, an affiliate of French diagnostic firm bioMérieux, makes an FDA-cleared test – BioFire Global Fever Special Pathogens Panel – that can detect multiple Ebola species, including Bundibugyo.
A company spokesperson said it is increasing production capacity and engaging with public health stakeholders and international contacts to assess potential needs.
2. Germany-based firm Altona Diagnostics’ test called RealStar Filovirus Screen RT-PCR Kit 1.0 is being used to detect the Bundibugyo outbreak in Congo. It has ramped up production to support local testing facilities in Congo.
(Reporting by Mariam Sunny in Bengaluru and Jennifer Rigby in Geneva;Editing by Josephine Mason and Rod Nickel)
