Scientists in the UK and Australia hope a new nasal spray that stops a COVID-19 infection in ferrets works in humans too.
The spray - developed by Australian biotech company Ena Respiratory - reduced the viral load in infected ferrets by 96 percent, compared to those who didn't get treated, according to a study published this week.
"It kicks in like a defence shield, which is broad-spectrum and non-specific," Ena adviser Roberto Solari, infectious disease expert at Imperial College London, told the Guardian.
As anyone who's had a test for the virus knows, it usually enters via the nose. SARS-CoV-2 - the virus' formal name - infects people by attaching itself to an enzyme called ACE2. A study in August found ACE2 is in abundant supply in the olfactory epithelium - the part of the nose responsible for detecting smell, which also could explain why loss of smell is often one of the first symptoms people experience.
Ena says INNA-051, the name of the compound used in the spray, "works by stimulating the innate immune system, the first line of defence against the invasion of pathogens into the body".
"By boosting the immune response in this way with INNA-051 prior to infection, the ability of the COVID-19 virus to infect the animals and replicate was dramatically reduced."
"We've been amazed with just how effective our treatment has been," said Ena managing director Christophe Demaison. "By boosting the natural immune response of the ferrets with our treatment, we've seen a rapid eradication of the virus."
The research is yet to undergo peer review, and it's not clear if the human immune system will react in the same way.
In fact, the immune system could be to blame for some of the more extreme cases, according to two new studies. While some people have no symptoms at all from a COVID-19 infection, or just a mild illness, some survive only after spending weeks in hospital - and others die.
A new study published in journal Science this week found around 10 percent of patients with severe illness have a mutation which causes some of the body's antibodies to turn on the immune system, rather than the invader. No one in their study - involving more than 3000 people - who had a mild illness had this mutation.
Almost all of the people with the mutation were men - 94 percent - which could explain why men are more likely to die from the disease than women.
Ena hopes to have its nasal spray in human trials early next year. INNA-051 was in development before the pandemic began early this year, its backers hoping for a spray that could work on all types of respiratory infections - then COVID-19 came along.
"While a vaccine is ultimately the key solution to combating COVID-19, governments need to be developing different treatment approaches to ensure they have a range of options, in the event that a vaccine proves elusive or takes longer to develop," said Chris Nave, chief executive of the Australian Medical Research Commercialisation Fund.
Several dozen vaccines are currently in development in a global effort the likes of which have never been seen before. Most estimates put the rollout date of a successful candidate sometime in 2021, but there's no guarantee.