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The new drug works by blocking an enzyme that helps the flu virus to replicate. Getty Images
  • A new drug has shown promise in fighting the flu virus in early clinical trials involving mice and ferrets.
  • Researchers say the medication also hasn’t shown any signs of allowing the flu virus to become drug resistant.
  • The next step is to test the drug for safety and efficacy in humans.

As the next generation of influenza (flu) drugs is being developed, another entrant is in the works that may one day be able to take on both the common flu as well as pandemic infections.

The new drug works by causing changes in the genetics of the flu virus that eventually stop it from being able to reproduce itself.

However, the drug has only been tested on animals so far, so it’s a long way from being available at your local pharmacy.

What’s exciting for the researchers involved, though, is that in testing so far the new drug has not opened the door to the flu virus becoming drug resistant.

“We have seen good consistency (on resistance) and that creates confidence of what to expect in humans,” said Richard Plemper, PhD, a professor at Georgia State University’s Institute for Biomedical Sciences and one of the authors of a new paper on the new drug’s latest steps.

That paper, published today, states that existing flu treatments such as Tamiflu are “increasingly compromised by pre-existing resistance of circulating viruses.”

Another new drug, baloxavir marboxil (Xofluza), which came on the market last year, has had a worse track record in avoiding inducing resistance, the paper notes. It points to a study that found the medication led to resistant virus in nearly 10 percent of participants within 5 days.

“We currently have just two classes (of flu drugs) approved,” Dr. Plemper told Healthline. “They are effective, but the problem is resistance. Viruses can escape these drugs.”

“We consider it imperative that the next generation of influenza inhibitors have high barriers against (resistance),” he added. “The next generation has to make it very difficult or, ideally, impossible for the virus to escape.”

Plemper and his colleagues state in their paper that the new drug has demonstrated “a prohibitive genetic barrier against the emergence of resistant influenza viruses” and that it has been shown “therapeutic efficacy far superior to that of” current flu drugs.

At least in trials on mice and ferrets.

Plemper said the next steps would be clinical trials to test the safety and efficacy of the new drug. He hopes to start those early next year.

If or when the drug could be on pharmacy shelves is “very difficult to predict,” Plemper noted.

He said it depends on the outcome of the trials and any unforeseen developments that crop up during them.

One big thing they’ll look at will be making sure there is no “escape route” through which the virus can achieve resistance.

“That’s one of the most important questions we have,” he said.

If everything does goes well, “any new drug we could get to treat influenza would be very, very welcome,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Tennessee.

He noted that because Xofluza — the most recent new flu drug and the first in 20 years — has shown that it can induce resistance, it’s “made a lot of people really cautious.”

The new drug works by blocking an enzyme called the RNA polymerase, which helps to copy DNA.

It’s central to the flu virus being able to replicate itself.

Blocking the enzyme causes genetic mutations that can eventually prevent the virus from replicating.

Dr. Schaffner called this mechanism unique. “If it does that effectively, it obviously will stop the multiplication of the virus in its tracks.”

“It’s the most provocative new drug that I’ve heard about in the pipeline” for influenza, he told Healthline.