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Griffith University researchers to trial naltrexone on long COVID patients
By Janelle Miles and Emma Pollard
7th May 2024
https://www.abc.net.au/news/2024-05-07/qld-griffith-university-trial-naltrexone-long-covid/103800050
Jayden Donald went from a fit and healthy teenager who rode his horses almost every day, to being so sick he could hardly sit up after his second bout of COVID-19.
A year later, the 19-year-old talented equestrian has only recently returned to university and to the competitive dressage arena after being diagnosed with long COVID.
"I was flat out walking," the University of Southern Queensland engineering student says at his family's picturesque property at Haigslea, about 50 kilometres west of Brisbane.
"You go from going to uni every day, seeing your mates, having a bit of fun, and saying, 'oh I want to go for dinner at the pub one night' to 'oh, I can't, I'm stuck at home'.'"
His symptoms included exhaustion so severe he was barely able to trudge from one end of his house to the other, brain fog, headaches, abnormally low blood pressure and a high heart rate.
A drug used for substance dependence
Long COVID is described by the World Health Organization as the continuation or development of new symptoms three months after an initial infection with SARS-CoV-2, the virus that causes COVID-19.
Some patients say the medical profession does not always take them seriously.
Jayden, on the other hand, sees a general practitioner and specialists with experience in treating long COVID.
He was prescribed low-dose naltrexone early in the course of his illness and 12 months on, is back to about 70 per cent of what life used to be like.
Naltrexone is administered in much higher doses to treat opioid and alcohol dependence.
But it's also been identified by researchers at Griffith University's National Centre for Neuroimmunology and Emerging Diseases (NCNED) on the Gold Coast as a potential treatment for long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
The team's latest research is published this month in the journal Frontiers in Immunology, building on its earlier findings that long COVID patients share the same impairment in cells as patients with ME/CFS.
Led by NCNED director Professor Sonya Marshall-Gradisnik, the researchers have previously identified a defect in a type of immune cell, known as natural killer cells, in both sets of patients.
Researchers take next step
The immunologist says the Griffith scientists were the first to identify a common trigger or cell mechanism behind both long COVID and ME/CFS.
Her PhD student Etianne Martini Sasso describes the patients as having faulty ion channels — or doors on their natural killer cell membranes — which prevent calcium from getting in and out of the cells.
It's the cellular equivalent of a door having a broken lock and key mechanism.
As part of her doctoral research, Ms Martini Sasso found she could restore the function of cells taken from long COVID and ME/CFS patients by treating them in a test tube with naltrexone.
The team's next step is to trial low-dose naltrexone in 100 long COVID patients — half will receive the drug and the remainder will be given a placebo. Researchers will be blinded to which patients receive the active medication.
Results will be compared with 50 healthy participants.
Blood samples will then be taken from all the volunteers and their natural killer cells will be tested before the trial, during the study and after its completion at three months.
The trial is expected to begin later this month with patients to be recruited across Australia, predominantly in Queensland, New South Wales, Victoria, and Western Australia.
A clinical trial of low-dose naltrexone is also planned for patients with ME/CFS.
Real spread of long COVID cases unclear
The researchers hope to identify more drugs that target and fix the broken door on patients' natural killer cells to improve treatment options, being mindful that patients can experience different symptoms despite having a similar diagnosis.
Symptoms can include gastrointestinal problems, muscle fatigue, shortness of breath, insomnia and changes in taste and smell.
Queensland Brain Institute scientist Fred Meunier, who was not involved in the Griffith University research, says the results are interesting but clinical trials are crucial to prove whether low-dose naltrexone can alleviate symptoms in long COVID patients.
"Hopefully, this is a good potential drug and a clinical trial would tell us whether it's working or not," says Professor Meunier, who is studying the long-term effects of COVID-19 on the brain.
The Australian Institute of Health and Welfare estimates the prevalence of long COVID-19 in Australia is between 5 and 10 per cent of those infected with the virus, based on the "limited data" available.
The state's chief health officer says the description wrongly implied long-term post-COVID viral symptoms were "somehow unique and exceptional" to other viral infections.
"Wide variation in estimates has been reported from international data, ranging from 9 per cent to 81 per cent in a global systematic review," the AIHW noted in a December 2022 analysis of the scientific literature.
"Many studies lack non-COVID-19 comparison groups that are needed to establish whether the prevalence can be attributed to COVID-19, which is particularly important for studies that rely on self-report of a diverse range of signs and symptoms that are not unique to long COVID."
Queensland Health does not routinely record information about long COVID numbers.
Slowly getting back on the horse
While Jayden Donald is doing well on low-dose naltrexone and other long COVID patients have anecdotally reported benefits from using the drug, the Griffith University scientists are working hard to verify their lived experiences.
After spending his first year out of high school largely confined indoors, the teenager recently returned to university and to horse riding.
"He started with riding 10 minutes … then 20 minutes, and then 30 minutes," Ms Donald says, adding he returned to the competitive dressage arena last month.
"He's much better."
Although he's not yet fully recovered, Ms Donald is hopeful Jayden is back on track to one day be able to achieve his dream of competing in an international junior dressage competition for equestrians aged under 25, on his horse Fred.
"We're lucky," she says. "There are some people in a lot worse situation than Jayden. We are very, very lucky."
To take part in the low-dose naltrexone trial, long COVID patients must be aged between 18 and 65 with a body mass index between 18.5 and 29.9.
Pregnant women and breastfeeding mothers are ineligible.