Sleeping sickness: An experimental drug cleared the parasite from the body in a clinical trial

In a small trial, an experimental drug was 100 percent effective at clearing the parasite that causes sleeping sickness from the bodies of people with early to moderate infections.


29 November 2022

A Trypanosoma brucei parasite that can cause sleeping sickness in the blood

Kateryna Kon/Shutterstock

A single pill can be 100 percent effective in treating early to mid-stage sleeping sickness. In one small trial, people with this stage of sleeping sickness showed no signs of having the parasite 18 months after receiving the experimental treatment.

The drug was even 95 percent effective at clearing the parasite that may have already spread to the brain, a sign of an advanced infection.

Sleeping sickness, also known as African trypanosomiasis, is a parasitic infection native to West and Central Africa. Between 2016 and 2020, 55 million people were at risk, of whom 3 million were at intermediate or higher risk.

condition caused Trypanosoma bruceitsetse fly, which typically picks up the parasite when consuming the blood of an infected mammal such as dogs, livestock, or humans. Early symptoms include fever, malaise, and itching. Although usually mild at first, the infection can quickly become severe and even fatal.

The main way to treat the infection is with a medicine called fexinidazole. Although it is up to 91 percent effective in removing the parasite, fexinidazole should be taken orally once a day with food for 10 days. It also has many common side effects, including vomiting. According to the European Medicines Agency, fexinidazole should be taken under medical supervision.

To test the potential of a one-time drug called Acoziborole, Anthoine Tarral of the Center for Neglected Diseases in Switzerland and colleagues analyzed 208 people over the age of 15 in the Democratic Republic of the Congo and Guinea. Participants were diagnosed with sleeping sickness between October 2016 and March 2019.

More than three-quarters of the participants were given acoziborole at a late stage of infection, defined as the presence of the sleeping sickness parasite in the cerebrospinal fluid, suggesting that the infection may have reached their brains.

The remaining participants were treated in the early to mid-stage of the infection, defined as the presence of the parasite in other body fluids and not in the cerebrospinal fluid. All participants were followed for 18 months after treatment.

Tarral says acoziborole hasn’t been compared to fexinidazole because there were relatively few people diagnosed with sleeping sickness in the study areas. Therefore, the sample size in each treatment group would be too small to make a meaningful comparison, he says.

Among participants with late-stage sleeping sickness, acoziborole had a 95 percent success rate, defined as the absence of parasites in various bodily fluids 18 months after treatment. This rose to 100 percent in those with early to moderate infections. The researchers did not measure at what point the parasite was cleared from the participants’ bodies during the 18-month follow-up period.

If not treated properly, the parasite can remain and cross the blood-brain barrier and invade the central nervous system, causing severe symptoms.

According to Tarral, acoziborole could help meet the World Health Organization (WHO) goal of eliminating a widespread worldwide transmission of sleeping sickness by 2030.

“This drug can change the world of this disease,” he says. Tarral says Acoziborole could be on the market within two years.

Acoziborole caused only a few mild to moderate side effects. Thirteen of the participants reported vomiting. It is unclear whether this is due to medication, an infection, or an unrelated factor.

“The findings suggest that akoziborol is a safe, effective, oral therapy for the treatment of human African trypanosomiasis,” says David Horn of the University of Dundee, UK.

“The goal set by the WHO is to stop disease transmission by 2030 and the challenges here should not be underestimated, but the improvements acoziborol offers over existing alternative therapies could be crucial in achieving this goal.”

Journal reference: Lancet Infectious DiseasesDOI:

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