Study from the National Microbiology Laboratory shows promising results for mpox (monkeypox) treatment

Note: The World Health Organization has begun using “mpox” as the preferred term for the name of the disease. The virus that causes the mpox disease is still referred to as the monkeypox virus.

In the spring of 2022, cases of mpox (monkeypox) began appearing in Canada and other countries where the disease hadn’t been observed before. Prior to this, mpox was generally limited to infrequent cases in countries where it was endemic. Its last introduction to the western hemisphere was in 2003, with cases linked to the exotic pet trade in the U.S.

The NML plays a key role in Canada’s mpox response

The Public Health Agency of Canada’s National Microbiology Laboratory (NML) is the national reference laboratory for rare and emerging viral pathogens like the monkeypox virus, and at the beginning of the outbreak it was the only laboratory in Canada that had the ability to provide confirmatory diagnostic testing for the mpox disease. The NML did all of the national diagnostics early on in the outbreak and to this day continues to do testing for some provinces. Scientists at the NML worked with their counterparts in highly impacted provinces to help establish their own testing protocols, which made it possible for cases to be diagnosed quicker.

“This was essential because the faster you identify cases, the faster they can be isolated or managed in a clinical setting,” says Dr. David Safronetz, Chief of Special Pathogens at the NML.

When it started to become clear that there would be many cases of mpox in Canada, the question arose—what is the treatment strategy for those sick with the virus?

Scientists in the NML’s Special Pathogens group set about to test one of the more promising potential treatments, an antiviral medicine called tecovirimat (also known as TPOXX).

What is tecovirimat and why is it being studied?

Tecovirimat was developed specifically to treat orthopox viruses (the monkeypox virus is a member of the orthopox family of viruses), particularly smallpox. Early research studies suggested the treatment would be effective and it was recommended as the lead medicine to be administered in severe cases of mpox. However, since mpox cases were few and far between before the outbreak, data was limited to confirm that the treatment was effective. Tecovirimat is currently being used off-label to treat mpox and hasn’t been authorized yet by Health Canada, so gathering further evidence that it works against mpox is important.

The NML began testing tecovirimat through animal models (i.e., mice) to confirm its effectiveness. They were able to isolate the virus from one of the first mpox cases that they identified in Canada and use it for the study. The NML researchers found that the medication was able to significantly reduce the amount of virus within the animals to the point where they didn’t see any obvious clinical signs of disease.

“The study is significant because it shows this treatment has the potential to lessen the effects of disease on patients and limit outbreaks,” says Dr. Safronetz. “It helps justify the further use of tecovirimat in people and it adds to our knowledge about the effective treatment of mpox.”

The NML is involved in several other aspects of mpox research. The Special Pathogens group is currently evaluating other antiviral treatments and new vaccination strategies. The genomics group is doing whole genome sequencing, which includes monitoring the trends in the evolution of the virus and looking for genetic markers that could indicate antiviral resistance.

Dr. Safronetz says the Special Pathogens group felt a strong sense of responsibility that came along with taking a lead role in an outbreak so close to home. The group often deploys to other countries to assist in managing the response, such as with the 2014-2016 Ebola outbreak in West Africa. They have also played a supporting role in domestic outbreaks like COVID-19.

“In contrast to the group’s long history of supporting responses to outbreaks internationally, the mpox response demonstrated the value of global work in keeping all of us safer, both in Canada and the rest of the world and further motivated us in doing our work,” says Dr. Safronetz.