The best treatment for COVID-19 could be the one you can’t get

None of the other treatments for COVID can boast comparable data. Not Paxlovid, not remdesivir, not molnupiravir. All these treatments gained their emergency use authorization status from the Food and Drug Administration by showing benefits in studies of only unvaccinated people.

Interferon lambda treatment is an important therapeutic advance. Unlike the monoclonal antibodies, which have consistently lost activity as variants emerged, interferon lambda is “agnostic” to these mutations and was effective in this study regardless of the type of variant, including Omicron. Interferon works by augmenting the body’s own immune response to the virus, so interferon is highly unlikely to select for resistance.

The good results from the trial go beyond the primary outcome of reducing hospitalization or death. The treatment had minimal side effects, similar to those of the placebo. Plus, those receiving active treatment experienced a faster decline in viral load by day seven than those in the placebo group, an effect that may decrease the risk of ongoing transmission.

Further benefits of the interferon strategy are its simplicity. One injection under the skin is comparable to an insulin shot, guarantees adherence to the treatment as a “one-and-done” therapy, and is much more simple than taking the 30 pills of Paxlovid, the 40 pills of molnupiravir, or the three days of intravenous infusions of remdesivir. Interferon is also unlikely to have significant interaction with prescribed medications, a big advantage when targeting COVID-19 therapy to the highest-risk people, many of whom are on complex medical regimens for other diseases.

With all these benefits, one might wonder why interferon lambda remains unavailable, while the three other treatments for outpatients with COVID-19 are heavily marketed and distributed — especially as about 460 Americans are dying each day from COVID. It’s particularly surprising since the results of the study were made public a year ago by Eiger BioPharmaceuticals, the company providing the drug for the trial.

The FDA turned down a request from Eiger for emergency use authorization for a variety of reasons shared by the company, including that the trial was not conducted in the United States. The FDA suggested that despite this high participant trial — one of the largest done to date on COVID-19 — the results served only as a proof of concept and required another definitive study.

In an effort to make interferon lambda available to patients before the anticipated winter surge, we wrote to the FDA in the fall to ask it to reconsider its decision. We cited the size and quality of the randomized clinical trial, asking that the FDA review the data based on their merits, independent from the company’s actions. We also emphasized the importance of increasing treatment options in the face of immune-evasive mutations and the known limitations of currently available therapies.

We received a polite response that said they would take our input into account. Let’s hope publication of this important study induces more concrete action soon by the FDA to represent the interests of American citizens. After all, COVID-19 may be less severe than it was in 2020, but it still kills hundreds of Americans daily. More important, for future outbreaks of viral infections, interferon lambda could be a key tool.

Dr. Paul Sax is clinical director of the Division of Infectious Diseases at Brigham and Women’s Hospital and a professor of medicine at Harvard Medical School. Dr. David Boulware is a professor of medicine at the University of Minnesota Medical School.