Respiratory viruses continue to place significant pressure on communities and healthcare services each winter. During the peak of the 2025 flu season, more than 1,000 people were presenting to NSW emergency departments each week with influenza-like illness.

For Professor Nathan Bartlett, a virologist at the University of Newcastle and leader of HMRI’s Infection Research Program, those numbers highlight the need for better ways to stop infections before they take hold.

Respiratory viruses such as influenza, RSV and COVID-19 can have serious consequences for older adults, young children and people living with chronic health conditions. Finding new ways to prevent these infections before they cause harm has been a major focus of Professor Bartlett’s research career.

Now a promising nasal spray he helped develop is advancing through clinical trials in the United States, bringing that goal one step closer to reality.

A new way to fight respiratory viruses

Professor Bartlett spent five years leading preclinical research on INNA-051, an investigational nasal spray designed to boost the body’s natural immune defences against respiratory viruses.

Rather than targeting a single virus, INNA-051 works by activating the innate immune system, the body’s first line of defence against infection.

“The idea is to boost the body’s natural ability to protect itself from respiratory viruses,” Professor Bartlett said.

“Most viruses, including influenza, RSV and COVID-19, enter through the nose. If we can activate the immune system at that point of entry, we can help stop the virus before it establishes an infection.

“Instead of targeting one specific virus, we’re enhancing the body’s broader antiviral response, which means it has the potential to protect against a range of respiratory infections.”

From an unexpected discovery to a global research program

Professor Bartlett’s involvement began after researchers at Melbourne’s Doherty Institute made an intriguing observation.

The compound behind INNA-051 had originally been developed to improve vaccine effectiveness, but researchers noticed it appeared to provide protection against influenza even without a vaccine.

“They asked me to design a program to prove it works, or doesn’t work,” Professor Bartlett said. “That’s how my involvement started.”

Over the following five years, University of Newcastle and HMRI researchers worked alongside collaborators in Australia and the United Kingdom to test the compound against a range of respiratory viruses, including rhinoviruses, coronaviruses, influenza and SARS-CoV-2.

“My role in Newcastle was one of the preclinical leads working on initial validation of the drug and its effect on viruses,” Professor Bartlett said.

“We were there at the start, getting the evidence needed to raise the money so they could go with a big clinical trial.”

Moving closer to patients

The early research helped pave the way for clinical development.

Melbourne-based biotechnology company ENA Respiratory has since secured more than $46 million in funding from organisations including the Gates Foundation and Minderoo Foundation, as well as an $18 million contract with the United States Department of Defence.

A Phase 2 clinical trial is now underway in the United States. Following a successful safety study involving 200 participants, a larger trial involving 900 people is planned later this year.

The study will focus on people at increased risk of exposure to respiratory viruses, including those living in university accommodation, households with young children and childcare settings.

For Professor Bartlett, the progress represents much more than a scientific milestone.

“You hope all that work you did makes it through clinical development and eventually ends up in doctors’ hands treating patients,” he said.

“It would protect those at high risk of nasty outcomes.”

A timely reminder as winter approaches

Recent FluTracking data showed respiratory illness activity rising as winter approached, highlighting the continued impact respiratory viruses have on communities across Australia.

The rise serves as a timely reminder that communities can’t afford to be complacent when it comes to respiratory illness and should take steps to reduce their risk of infection this winter.

For Professor Bartlett, while new treatments and preventions are important, simple public health measures remain one of the most effective ways to protect yourself and others.

“Vaccination remains one of the most effective ways to protect yourself and those around you from serious illness,” Professor Bartlett said.

“If you’re unwell, stay home where possible, practise good hand hygiene and try to avoid close contact with people who may be vulnerable.

“Respiratory viruses spread very easily, but small actions can make a big difference in protecting our families, workplaces and communities.”