In a world first, scientists have repurposed an existing drug and shown it could help fix faulty proteins thought to be involved in long COVID. The drug, naltrexone, is typically used to treat substance use disorders, but the team believe their research shows its potential to help millions of people living with long COVID and ME/CFS.

As science has learned more about long COVID, many have drawn parallels between it and the chronic condition ME/CFS, which stands for myalgic encephalomyelitis/chronic fatigue syndrome. Sometimes referred to simply as chronic fatigue syndrome, this often misunderstood condition is associated with a catalog of symptoms beyond debilitating fatigue, with at least a quarter of patients becoming bed- or housebound for long periods of time, according to the Centers for Disease Control and Prevention.

When people in recovery from COVID-19 began to report a similar constellation of symptoms, including exhaustion, brain fog, heart palpitations, and gastrointestinal issues, ME/CFS patients, clinicians, and researchers spotted the similarities between the two syndromes.

A team at Griffith University’s National Center for Neuroimmunology and Emerging Diseases (NCNED) have now built on some of their previous findings in ME/CFS to show that an existing drug could have potential benefits for patients with long COVID too.

The study centers on a type of protein called an ion channel. “Ion channels are integral membrane proteins that facilitate the passage of ions (charged particles) across the cell membrane,” explained first author Etianne Sasso, a PhD candidate at Griffith University, in a statement.

Effectively, these are gateways by which ions that are essential for many bodily processes can enter and exit cells. The team had previously shown that in both ME/CFS and long COVID, some of the ion channels on immune cells don’t function effectively.

The team discovered that naltrexone – a drug that was first approved in the US in 1984 as a treatment for substance use disorders involving alcohol and opioids – can restore the function of these ion channels in cells from ME/CFS patients. Now, they’ve repeated that finding in long COVID, using a technique called electrophysiology.

“We found that by restoring the function of these ion channels, important ions such as calcium were again able to move in and out of immune cells, controlling many of the body’s biological processes,” Sasso explained.

Effective treatment strategies are lacking for both long COVID and ME/CFS, so these results could be great news for a large, but underserved patient community.

Following their discovery, the researchers are now planning two clinical trials to see how real patients respond to the drug.

“We will be undertaking two clinical trials testing the efficacy of low dose naltrexone where the first will be in long COVID patients while the second trial will, for the first time, be in ME/CFS patients,” said Professor Sonya Marshall-Gradisnik, the senior author and director of NCNED.

“Should these trials prove successful, it could mean a vastly improved quality of life for countless individuals struggling with long COVID and ME/CFS.”

The study is published in Frontiers in Immunology.