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Baltimore's Profectus marks key step in race for Ebola vaccine

An Ebola vaccine being developed by Baltimore company Profectus BioSciences is effective against the strain of the virus that has ravaged West Africa, research to be published Thursday suggests — a milestone the company says is a first in the race to prevent outbreaks of the deadly disease.

While other leading vaccine candidates have progressed to human trials in Africa, published data on the protection they provide is based on tests exposing animals to a relatively mild laboratory version of the Ebola virus, or strains from previous outbreaks.

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But Profectus' vaccine successfully shielded primates from a potent strain virtually identical to the one that has infected more than 25,000 people, researchers wrote in a study in the journal Nature.

That sort of evidence could be key in obtaining approval from the Food and Drug Administration. Dwindling counts of new Ebola cases in West Africa could make it difficult for other researchers to determine whether their vaccines prevented subjects from contracting the virus. They might have to rely on lab data, as Profectus has, to show that the treatments work.

"It will be necessary for others to now catch up with us," said John Eldridge, chief scientific officer at Profectus. "I think all these other vaccines will need to back up and essentially demonstrate what we have just demonstrated."

The company's advantage might be only temporary. It's possible that scientists working on other vaccines have gathered similar data but haven't published it yet, said Dr. Heinz Feldmann, chief of the laboratory of virology at the National Institute of Allergy and Infectious Diseases.

It can take time to complete such research. Just obtaining the permits and other approvals needed to handle a new strain of a pathogen such as Ebola may take as much as a year, Feldmann said.

Still, he said, Profectus' findings are a significant step in the fight against the strain of Ebola that has killed more than 10,000 people since late 2013.

"This is novel because they are the first," Feldmann said. "The big question which was out in the field is, are the current vaccine approaches, all based on previous strains, are they going to be efficacious against this new virus?"

In the Profectus study, two vaccines were administered to rhesus macaques. When researchers later exposed the animals to a virus 97 percent identical to Ebola Makona — the strain in West Africa — none became sick. Two unvaccinated macaques died.

Profectus has received $55 million in investment for the vaccine research, Eldridge said. Clinical trials on humans are set to begin in June.

The vaccine is based on an animal virus modified to include genes from a key protein in the Ebola virus that prompts the body to build immunity. It does not contain the Ebola virus itself, Eldridge said, and cannot cause Ebola infection.

It is considered a second-generation version of one of two leading Ebola vaccine candidates, developed by the Public Health Agency of Canada and NewLink Genetics and licensed by drugmaker Merck. Both vaccines contain live, weakened particles of the modified animal virus, but Profectus' version is designed to be less capable of replicating itself, which is supposed to reduce its side effects without limiting its effectiveness.

The Merck vaccine and another developed by GlaxoSmithKline and the National Institute of Allergy and Infectious Diseases are considered leading candidates against Ebola. Clinical trials of both are underway in West Africa.

But those efforts could be challenged as Ebola's spread winds down. Last week, the number of new cases reported fell to 30 — the lowest weekly total since May 2014, according to the World Health Organization.

Twenty-one of those cases were reported in Guinea; the rest were in Sierra Leone. Liberia has not reported a new case since February, and its last Ebola patient died March 27. If no new cases appear within 42 days, a country is declared Ebola-free.

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While the trend is positive, Thomas Geisbert said, it poses a challenge for vaccine researchers.

"The question everybody has right now is, are they going to have enough data because of the outbreak slowing down?" said Geisbert, a professor of microbiology and immunology at the University of Texas Medical Branch at Galveston. He helped Feldmann develop the science behind the Merck and Profectus vaccines in the early 2000s.

A lack of data from clinical trials in Africa would be a setback for research teams because it is the only way to test the vaccines' effectiveness in humans.

Because it is unethical to deliberately expose human test subjects to Ebola, researchers need either field data or data from animal experiments to prove their vaccines work. Without sufficient field data, Geisbert said, many teams will likely have to turn to studies like the one published Thursday.

If a vaccine candidate has protected animals from older strains of Ebola in past experiments, he said, it's likely it will also be effective against the current Ebola strain. But proof is still required.

"You can't prove it until you do it," Geisbert said.

Officials at Merck, GlaxoSmithKline and Johnson & Johnson, which is developing another Ebola vaccine candidate, did not respond to questions about their vaccine research efforts.

Eldridge said the research puts Profectus' vaccine a step ahead of the others. Though the company hasn't started trials to test its safety for humans — 39 people are set to receive injections in Gaithersburg in June — a similar vaccine it is developing for HIV has been well-tolerated in volunteer test subjects, company officials said.

The company is also planning trials in September of a single vaccine to protect against two other strains of Ebola plus Marburg virus, a similar pathogen.

But Feldmann said it's still too early to talk about which vaccines are superior to others.

"It's a process of selection based on data and based on experience," Feldmann said. "The most important thing at the end is that we're going to have at least one that is working."

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