Scientists have developed a nasal spray that is safe and effective in protecting against various strains of the flu, an advance that could lead to new strategies to counter seasonal influenza outbreaks.
Despite the development of vaccines, seasonal influenza still accounts for as many as 646,000 deaths every year.
New strains of the virus are also constantly emerging, making previous generations of vaccines less effective, with newer variants posing potential pandemic threats.
Researchers have sought different prophylactic strategies to protect people against influenza, including antibody therapies.
But most such therapies in the form of injections don’t elicit large amounts of antibodies in mucosal areas such as the nose.
Now, scientists from the Harvard TH Chan School of Public Health have developed CR9114, an anti-influenza antibody that can be delivered via the nose.
An early phase clinical trial has found that these antibodies, sprayed into the nose of healthy volunteers, bind and neutralise the virus.
Researchers also found that the antibody nasal spray is safe and well-tolerated in humans in two trials involving 143 participants.
“Intranasal CR9114 was safe and well-tolerated across all doses and schedules,” scientists wrote in the study published in the journal Science Translational Medicine.
“These data establish the basis for efficacy studies in humans and suggest that intranasal CR9114 may represent an effective immunoprophylactic for influenza virus,” the study noted.
The experimental nasal spray was also tested in macaques at various doses and dosing schedules.
While the nasal spray led to antibody accumulation in the nose, where the virus first invades, the antibodies degraded in about three hours.
Researchers found that the spray provided the best protection against both influenza A and B when given twice a day.
“Twice-daily administration of CR9114 protected nonhuman primates against influenza virus challenge with the same intranasal formulation and device as used in humans,” scientists wrote.
Antibodies isolated from the noses of treated volunteers were also found to bind to influenza A and B in lab culture, proving they have neutralising potential.
These antibodies can be self-administered via nasal sprays, offering a means to quicker roll out during the early stages of flu outbreaks, scientists say.
Experts say intranasal delivery of antibodies could compliment vaccines during flu outbreaks.
“A major advantage of nasal delivery is that it produces high antibody levels right where the virus enters, using much smaller doses than intravenous antibody treatments. However, the antibody cleared quickly from the nasal surface,” said immunologist Isabelle Montgomerie from New Zealand’s Malaghan Institute of Medical Research.
“This means it would not replace vaccination, but it could provide short-term protection during a pandemic, especially for high-risk groups like healthcare workers,” said Dr Montgomerie, who was not involved in the study.