(Bloomberg) -- Positive results from an experimental Covid-19 therapy are rekindling questions about why it hasn’t gained authorization from US regulators, even as the availability of other treatments drops. 

Adults at high risk of severe Covid who were treated with Eiger BioPharmaceutical Inc.’s therapeutic, called peginterferon lambda, had a 51% lower risk of hospitalization than those who received a placebo, according to the study published Wednesday in the New England Journal of Medicine.  Most of the patients in the study, about 83% were vaccinated. 

The report builds on data from the same study that were released last year without peer review by experts. Those findings have failed to gain emergency authorization for the drug, even while Covid antibodies have lost effectiveness due to new mutations. Palo Alto, California-based Eiger said it has no plans to pursue emergency use authorization from the US Food and Drug Administration, based on feedback from the agency. 

A spokesperson for the FDA declined to comment for the story, citing federal disclosure laws and regulations.

Signaling Protein

Interferon is a signaling protein naturally produced by the body that orchestrates defenses against viruses, such as those that cause hepatitis, and also plays a role in battling diseases like cancer. In the early days of the pandemic, researchers found that people with an impaired interferon response were more vulnerable to worse Covid outcomes, leading to hopes that using it in therapy might be beneficial. 

Early enthusiasm was dimmed by research showing that another form of interferon didn’t benefit patients hospitalized with Covid when administered alongside Gilead Sciences Inc.’s antiviral, remdesivir. Later, the FDA declined to meet with Eiger to discuss authorization of interferon, according to a company statement, because of concerns regarding how the NEJM study was conducted.

Eiger has been developing interferon lambda to treat viral hepatitis and gave the drug to researchers who wanted to study its use against Covid. Interferon was among treatments included in a large international trial that has been used to assess several Covid therapies. 

The company sees wider applications for interferon, such as treating other lung pathogens like respiratory syncytial virus, Eiger interim Chief Executive Officer David Apelian said. The company is looking at potential partnerships and reviewing its entire portfolio, including interferon lambda for Covid, and sees having a more comprehensive plan for future investments in the second quarter, he said. 

Darkest Chapters

The NEJM findings support interferon’s US clearance, said Jeffrey Glenn, a Stanford University microbiologist who was senior author on the interferon study, and the drug should be made available to people who would most benefit. Those include immune-compromised patients or people who can’t take Pfizer Inc.’s Paxlovid because of potential adverse drug interactions. 

“This is one of the darkest chapters of the whole pandemic,” Glenn said. Interferon could have saved millions of lives if it had been available earlier, and still could if regulators cleared its use, he said. 

Read more: Merck Covid Drug Linked to New Virus Mutations, Study Says

Others aren’t convinced. Key differences between the US population and those in the study, who came from Brazil and Canada, make the findings difficult to interpret, said Roy M. Gulick, an infectious diseases expert at Weill Medical College of Cornell University who leads a National Institutes of Health panel on Covid treatment guidelines. For example, the need for hospitalization, a key outcome in the study, can be assessed in different ways around the world. The study also collected data on patients whose emergency room visits were longer than six hours, another outcome that could vary by country, Gulick said. 

The availability of existing antivirals like Paxlovid and remdesivir has raised the bar for new emergency authorizations, Gulick said. Alternatives like an oral version of remdesivir or Shionogi & Co.’s Xocova may hold more promise than interferon, he said. 

New drugs could become critical as options for treatments start running dry. The virus has evolved to thwart most approved monoclonal antibodies made by Regeneron Pharmaceuticals Inc., Eli Lilly & Co. and AstraZeneca Plc. Unfettered use of Pfizer’s antiviral could fuel the emergence of drug-resistant mutations, scientists have said, and at least one preprint study suggests that Merck & Co.’s Lagevrio gives rise to new forms of the virus that are capable of spreading. 


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