Stop the virus before it establishes an infection
Each winter, respiratory viruses test the limits of healthcare systems and the resilience of the most vulnerable among us. In Newcastle, Australia, virologist Professor Nathan Bartlett has spent five years asking a deceptively simple question: what if the body's own defences could be awakened at the very threshold of infection? The answer — a nasal spray called INNA-051 that primes the innate immune system before a virus can take hold — is now advancing through US clinical trials, backed by over $64 million in funding, carrying with it the quiet hope that prevention might one day arrive before the emergency room does.
- Every winter, more than 1,000 people per week flood New South Wales emergency departments with influenza-like illness — the human cost that drives this research forward.
- Rather than chasing individual viruses, INNA-051 targets the body's universal front door — the nose — activating broad innate immunity that could defend against influenza, RSV, COVID-19, and beyond.
- Over $64 million in funding from the Gates Foundation, Minderoo Foundation, and the US Department of Defence signals that the world's most powerful health investors are betting on this approach.
- A Phase 2 trial enrolling 900 high-risk participants — university residents, households with young children, childcare workers — is planned for later this year, the largest test yet of the compound's real-world promise.
- Professor Bartlett urges measured optimism: vaccination, hand hygiene, and staying home when sick remain the bedrock of respiratory protection, with INNA-051 as a potential addition, not a replacement.
Every winter, respiratory viruses arrive with predictable force. During the 2025 flu season in New South Wales, more than 1,000 people walked into emergency departments each week with influenza-like illness. That pressure sits at the heart of Professor Nathan Bartlett's work — a five-year effort to build a tool that might prevent those visits from happening.
Bartlett, a virologist at the University of Newcastle and leader of the Infection Research Program at HMRI, has long focused on those most at risk: older adults, young children, people with chronic conditions. His driving question has been both simple and difficult — how do you stop an infection before it takes hold?
His answer is INNA-051, a nasal spray that activates the innate immune system at the nose, the primary entry point for most respiratory viruses. Rather than targeting a single pathogen, the spray enhances the body's broader antiviral response, offering potential protection against influenza, RSV, COVID-19, and other infections. The compound originated at Melbourne's Doherty Institute, where researchers developing vaccine adjuvants noticed it seemed to protect against influenza even without a vaccine. They asked Bartlett to find out whether the effect was real — and five years of testing against rhinoviruses, coronaviruses, influenza, and SARS-CoV-2 followed.
That evidence proved compelling. Melbourne-based ENA Respiratory has secured more than $46 million from the Gates and Minderoo Foundations and an $18 million US Department of Defence contract. A Phase 2 trial is now underway in the United States — following a 200-person safety study, a larger trial of 900 participants is planned for later this year, focused on high-exposure settings like university accommodation and childcare.
For Bartlett, the progress carries meaning beyond the laboratory. He hopes the years of work will eventually reach doctors and patients — particularly those most vulnerable to serious outcomes. But he is careful to keep expectations grounded: vaccination remains the most effective protection, and the everyday measures of hand hygiene, staying home when sick, and avoiding contact with vulnerable people still matter enormously. As another winter approaches, that reminder is as important as any breakthrough.
Every winter, respiratory viruses arrive like clockwork, and the pressure on hospitals is immediate and measurable. During the peak of the 2025 flu season in New South Wales, more than 1,000 people walked into emergency departments each week with influenza-like illness. That number sits behind Professor Nathan Bartlett's work—a five-year effort to develop a tool that might prevent those visits from happening in the first place.
Bartlett is a virologist at the University of Newcastle and leads the Infection Research Program at HMRI. His focus has always been on the vulnerable: older adults, young children, people with chronic conditions. Respiratory viruses like influenza, RSV, and COVID-19 can turn serious quickly for these groups. The question that has driven his research is straightforward but difficult: how do you stop an infection before it takes hold?
The answer he's been working toward is a nasal spray called INNA-051. Rather than designing a drug to fight a single virus, Bartlett and his team took a different approach. The spray activates the innate immune system—the body's first line of defence—at the exact point where most respiratory viruses enter: the nose. The logic is elegant. If you can wake up the immune system at the gate, before the virus establishes itself, you've won half the battle. And because the spray works by enhancing the body's broader antiviral response rather than targeting one specific pathogen, it has the potential to protect against a range of respiratory infections, not just one.
The compound's journey began elsewhere. Researchers at Melbourne's Doherty Institute had developed it to improve vaccine effectiveness, but they noticed something unexpected: it seemed to offer protection against influenza even without a vaccine. They asked Bartlett to design a research program to test whether the effect was real. That question launched five years of work. Bartlett and his colleagues at Newcastle and HMRI, working with collaborators in Australia and the United Kingdom, tested the compound against rhinoviruses, coronaviruses, influenza, and SARS-CoV-2. His role was to validate the drug and measure its effect on viruses—to gather the evidence that would eventually justify the money needed for larger trials.
That evidence worked. Melbourne-based biotechnology company ENA Respiratory has now secured more than $46 million in funding from the Gates Foundation and Minderoo Foundation, plus an $18 million contract with the United States Department of Defence. A Phase 2 clinical trial is underway in the United States. After a safety study involving 200 participants, a larger trial with 900 people is planned for later this year. The focus will be on people at high risk of exposure: those in university accommodation, households with young children, childcare settings—the places where respiratory viruses spread fastest.
For Bartlett, the progress carries weight beyond the science. "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." But he is careful not to oversell what a new drug can do. Vaccination remains the most effective protection. Staying home when sick, hand hygiene, avoiding close contact with vulnerable people—these simple measures still matter enormously. Respiratory viruses spread easily, but small actions can slow them down. As winter approaches and respiratory illness activity begins to rise again, that reminder is worth repeating.
Citas Notables
If we can activate the immune system at that point of entry, we can help stop the virus before it establishes an infection.— Professor Nathan Bartlett
You hope all that work you did makes it through clinical development and eventually ends up in doctors' hands treating patients.— Professor Nathan Bartlett
La Conversación del Hearth Otra perspectiva de la historia
Why does a nasal spray work better than a pill or injection for this?
The virus enters through the nose. If you can activate the immune system right there at the point of entry, you're meeting it before it spreads deeper into the lungs or bloodstream. It's about geography—being in the right place first.
But the spray activates the innate immune system, not the adaptive one. Isn't that the weaker response?
The innate system is your first responder. It's fast and broad. The adaptive system is more precise but takes time to build. If you can stop the virus in the first hours, before it establishes itself, you don't need precision—you need speed and coverage.
So this could work against viruses that don't exist yet?
In theory, yes. That's the whole point. We're not designing a drug for influenza or COVID-19 specifically. We're enhancing the body's general antiviral defences. A new respiratory virus emerges, and the innate system should still recognize it as a threat.
Why did it take five years of preclinical work before human trials?
You have to prove it's safe and that it actually does what you claim. You test it in cells, in animal models, measure how it affects different viruses. You need that evidence before you can ask 200 people to breathe it in.
What happens if the Phase 2 trial succeeds?
Then you move to Phase 3—larger, longer trials to confirm the effect holds up in real-world conditions. If that works, you submit to regulators. If they approve it, it becomes another tool in the toolkit alongside vaccines and public health measures.
Is there a risk that boosting the innate immune system could cause problems?
That's exactly what the safety studies are for. You're looking for inflammation, allergic reactions, any sign that activating the immune system causes harm. The first 200 participants in the US trial already went through that. So far, no red flags.