Drugmakers race to find weapons against rare Ebola strain as Congo toll mounts
Global health authorities and a clutch of drugmakers are racing to assemble medical defences against an Ebola outbreak in eastern Democratic Republic of Congo, where a rarer strain of the virus has left the world without a single approved vaccine or therapy to deploy.
The outbreak, traced to the Bundibugyo strain, is suspected to have caused about 906 cases including 223 deaths, with the World Health Organization warning the toll is likely to climb. The strain, known as BDBV, carries a fatality rate of up to 40 per cent. Unlike the more common Zaire strain, against which licensed shots and drugs already exist, Bundibugyo has no approved countermeasures — a gap that has forced regulators toward emergency and compassionate-use pathways for untested products.
Most of the experimental treatments now under review have never been tested in humans, and the evidence for their use rests largely on animal data. The WHO last week recommended prioritising a slate of antibodies, antivirals and vaccines for both prevention and treatment.
On vaccines, the agency identified a single-dose candidate from the International AIDS Vaccine Initiative as the most promising, though development would likely take seven to nine months before clinical assessment. A rival shot, ChAdOx1 Bundibugyo — built on the platform behind the Oxford/AstraZeneca Covid-19 vaccine and manufactured by the Serum Institute of India — could yield doses for trials within two to three months, the WHO said, with production already under way through a partnership including CEPI and the University of Oxford. A third candidate, developed at the University of Texas Medical Branch using the same technology as Merck's approved Ervebo, has shown a survival benefit in primates.
The antibody field is led by privately held Mapp Biopharmaceutical, whose pan-ebolavirus drug MBP134 has been prioritised for trials in confirmed cases and backed by the US Biomedical Advanced Research and Development Authority. Regeneron's maftivimab, a component of its approved Zaire treatment Inmazeb, is also being explored; the company said it had donated 500 doses of Inmazeb to the WHO and that supply was already on the ground in Congo.
In antivirals, Gilead Sciences has put forward its oral drug obeldesivir as a possible post-exposure prophylaxis. The company said preclinical data pointed to activity against Bundibugyo, though the drug is not approved for the purpose. Gilead's older intravenous antiviral remdesivir has also shown laboratory activity against the strain, and the WHO has flagged a combination of an antibody and remdesivir for evaluation.
A further obstacle is diagnosis. The WHO has said limited testing capacity is slowing the response, with the most widely deployed frontline tool unable to distinguish the Bundibugyo strain. Tests from bioMérieux affiliate BioFire Defense and Germany's Altona Diagnostics can detect it, and both firms said they were ramping up production.
The episode underscores a familiar problem in outbreak economics: commercial incentives to develop products against rare viral strains are thin until an emergency arrives, at which point the scientific groundwork is rarely far enough along to deploy at speed.