An antibody spray that is sprayed into the nose was found to prevent flu not only in animals but also in humans. The influenza virus that causes flu keeps changing its appearance, so vaccines had to be made anew every year. The antibody tested this time binds to a part of the virus that rarely changes, raising expectations that it can respond to any type of variant.
Leyden Laboratories, a Dutch bio company, announced on the 5th in the international journal Science Translational Medicine that "a nasal spray made with the CR9114 antibody showed a preventive effect against flu in animal tests and early clinical trials." The researchers conducted animal experiments exposing subjects to actual flu viruses, and in human clinical trials checked whether the antibody was safe and maintained a certain level in the nose.
◇ Flu prevented in animals, safety also proven in humans
CR9114 is an antibody developed by Janssen, a subsidiary of Johnson & Johnson (J&J) in the United States. Antibodies bind to viruses and neutralize them so they cannot penetrate human cells. They then recruit other immune cells to eliminate the virus.
However, when injected into animals' blood vessels, the preventive effect against flu was not significant. That is because influenza viruses invade through the nose first, and the amount of antibody that entered the bloodstream and reached the nose was small.
Leyden Laboratories introduced CR9114 from Janssen in 2022 and developed it into a spray that can be administered into the nose instead of an intravenous injection. To make the injectable into a spray form, only part of the antibody was used. Antibodies have a Y-shaped structure. The branches on both sides, called Fab, bind to the virus, and the stem-like Fc binds to other immune cells.
The researchers proved that spraying only Fab into the nose can prevent flu. When CR9114 was sprayed into the noses of mice and monkeys, flu did not develop even when they were exposed to influenza A and B viruses. Influenza viruses come in three types—A, B, and C—but the ones that cause disease in humans are A and B.
Following the animal studies, the researchers also conducted an early clinical trial on 143 people between 18 and 55. When the spray was administered twice a day, antibody levels were stably maintained inside participants' noses, and no major side effects were observed.
After spraying the noses of people, the researchers collected biospecimens and tested them against various influenza viruses. The spray's antibodies bound to a variety of viruses. This confirmed the possibility of a universal flu preventive.
The most effective way to prevent flu is vaccination. It works by administering part of the virus into the body to produce antibodies in advance. The problem is that because influenza viruses constantly mutate, vaccines must be made anew every year.
Leyden Laboratories' antibody targets the stem region of hemagglutinin (HA), which changes very little in influenza viruses. Hemagglutinin acts as a key for the virus to attach to human respiratory cells. Blocking this part can stop various influenza viruses.
◇ Effective against variants, potential as a universal preventive
The next step is to directly expose people who use the spray to influenza viruses to confirm whether it prevents flu. This time, only safety in humans was confirmed; its preventive efficacy in real-world conditions was not proven.
Experts noted that even if the antibody spray passes all clinical trials, it has limitations in several respects. Because viruses can invade not only through the nose but also through the mouth, the spray cannot block flu 100%. Also, while vaccines are injected once during the flu season, the spray has the drawback of needing to be used twice a day.
Despite these limitations, if the antibody spray is commercialized, it could be a big help in preventing unforeseen pandemics, such as avian influenza. Since 2024, cases of dairy cows being infected with highly pathogenic avian influenza viruses have occurred one after another in 18 U.S. states, putting health authorities around the world on alert. Not only livestock but also wild mammals and people were infected, and there were deaths.
Leyden Laboratories tested the biospecimens collected from the noses of people who used the spray against an avian influenza A virus that was transmitted to humans in China in 2013 and confirmed the antibody's effect. Experts believe that if a pandemic occurs, the antibody spray could protect people with weakened immunity or medical workers until vaccines are rolled out.
In addition, an antibody spray can produce antibodies in many people in a short period of time, quickly achieving a herd immunity effect. While it takes time for antibodies to form after a vaccine injection, the spray can provide preventive effects immediately.
References
Science Translational Medicine (2026), DOI: https://doi.org/10.1126/scitranslmed.adz1580
Scientific Reports (2025), DOI: https://doi.org/10.1038/s41598-025-94314-5