A coronavirus-fighting nasal spray protects ferrets from infection, early research shows. But it has a ways to go before reaching people.

• A coronavirus-fighting nasal spray protected ferrets from contracting the virus, according to a preliminary study.
• But we don't yet know how people would react to the spray's active ingredient.
• If the spray does work in people, it could be cheaper and easier to distribute than a vaccine.

A nasal spray that blocks the coronavirus from invading cells appears to protect ferrets from contracting the virus, according to a preliminary study.

The research, uploaded to the archive BioRxiv last week, was funded by the National Institutes of Health but has not yet been peer-reviewed.

Microbiology experts think it could be a promising first step toward a coronavirus-prevention treatment.

"I thought it was really compelling, what they did," Wes Van Voorhis, a researcher in infectious diseases at University of Washington School of Medicine, told Business Insider. "It looks like it was perfect protection."

Van Voorhis was not involved in the study, and he noted that no matter how promising, it's just a first step because the research involved only ferrets. And it was a small number of ferrets at that: just six got the spray. It's not yet known what the spray's effects will be on humans, especially because its active ingredient — lipopeptides — could trigger immune responses in people that make them feel sick.

"A lot of bacteria contain lipopeptides, and so our immune system is rigged up like crazy to recognize that," Van Voorhis said.

A spray that 'completely blocks' coronavirus particles

Whereas vaccines work by training the body to recognize and attack a pathogen, the nasal spray works similarly to the monoclonal antibodies President Trump received when he got the coronavirus in October. It's designed to stop the coronavirus from entering cells in the first place.

The coronavirus' spike protein enables it to fuse with a cell and insert its viral DNA. So the nasal spray contains a chain of protein and fat molecules — the lipopeptide — which binds to that spike protein, rendering it useless.

"They came with a strong premise, which was that they could block the fusion using a peptide," Van Voorhis said.

The team used ferrets as test subjects because like humans, they contract the coronavirus fairly easily.

Researchers infected three ferrets with the coronavirus, then gave the spray to six other ferrets. Another six got a placebo spray. They then divided the ferrets among three cages — each with three ferrets that had gotten the spray, three that had gotten the placebo, and one infected with the coronavirus.

After 24 hours, researchers separated the ferrets, then tested them for coronavirus every day for a week.

The results showed that no ferret given the spray got infected, whereas all of the ferrets given a placebo contracted the virus.

"In-host virus replication was completely blocked," the researchers wrote.

Anne Moscona, a study coauthor, told the New York Times that "if it works this well in humans, you could sleep in a bed with someone infected or be with your infected kids and still be safe."

However, the study's sample size was "tiny," Van Voorhis said, and the paper doesn't address the possible issues that lipopeptides could pose for human immune systems.

The researchers behind the study didn't observe any negative reaction to the spray among the ferrets, but the animals' immune systems might respond differently to lipopeptides than humans do. It's also possible the ferrets did have negative side effects but couldn't communicate that to researchers.

A human trial is the only way to figure out whether the spray could work without making people feel sick.

A cheaper, easier alternative to vaccines?

The research team needs to secure additional funding to launch human trials. If those trials happen and prove the spray to be safe and effective, the treatment could deliver benefits similar to a vaccine at a fraction of the cost and effort.

That's because the lipopeptide used as the active ingredient could be made cheaply, and it can be stored as a powder that a doctor could mix into sugar and water to make the nasal spray solution. The powder wouldn't need to be refrigerated. Some coronavirus vaccine candidates, by contrast, need to be kept at temperatures approaching minus 100 degrees Fahrenheit.

That makes a spray a promising alternative in communities that lack refrigeration.

Of course, a daily nasal spray would take more effort on a user's part than a one-time vaccine. But if it was effective enough, and a sufficient number of people used it for weeks or months, that could help communities control the pandemic.

However, Van Voorhis said, "whether everybody's going to get up every day and spray this stuff in their nose, it's another question."