Sleeping sickness is a notorious disease — immortalized in Joseph Conrad's Heart of Darkness. A single bite from a tsetse fly carrying the parasite is all it takes to infect someone. Without treatment one form of the illness can progress from mild symptoms to death in a matter of weeks.
Now, a new drug holds the promise of helping the World Health Organization meet its goal of eliminating the disease by 2030. A committee of the European Medicines Agency has given an important green light to the first single-dose treatment — a medication called acoziborole, which could be in use by early next year.
Acoziborole is especially notable because it is taken as three pills swallowed together in a single dose, replacing long-used earlier treatments that included intravenous drugs known to cause a "burning" sensation in the veins as well as being fatal for nearly one in 20 patients. Even the current first-line oral treatment, fexinidazole, must be taken for 10 days and comes with severe side effects such as nausea, vomiting and heart-rhythm disturbances. By contrast, clinical trials of acoziborole found just one significant side effect: mild to moderate headache.
"For decades, available treatments were difficult to use," says Dr. Gerardo Priotto, who leads the World Health Organization's efforts against sleeping sickness and was not part of the new drug's development team. Therapies required staff, equipment and reliable infrastructure, he says. "These challenges were especially severe in remote, rural areas, where most cases occur and health services are limited."
'A transformative tool'
The new drug, acoziborole, removes just about all of these barriers, representing a major breakthrough. "Its single‑dose, well‑tolerated regimen can dramatically simplify patient care, improve access to treatment and accelerate progress toward the elimination of sleeping sickness. It is a transformative tool for both patients and public health programs," Priotto says.
The harsh side effects of previous medications also discouraged people from seeking treatment, says Dr. Stéphane Hugonnet, who worked on the clinical trials and leads the response to sleeping sickness for the Drugs for Neglected Diseases Initiative (DNDi), a nonprofit that developed the drug with pharmaceutical firm Sanofi and funding from multiple partners, including the Gates Foundation, which provides financial support for NPR's global health coverage.
"Many patients remember what the treatment was like for themselves or family members and were afraid of care," Hugonnet says.
The tsetse fly picks up the parasite from an infected person and then can transmit it to someone else. The insect thrives in warm savanna woodlands and in vegetation along lakes or streams, so the disease tends to take hold in remote areas where people rely on fishing, hunting and agriculture for their livelihoods.
"Like many tropical diseases, sleeping sickness is a disease of the poor," says Dr. Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine in Houston.
Over the years, hundreds of thousands have died from sleeping sickness, but sustained efforts — tsetse fly control, diagnostic testing and medical treatment — have drastically reduced the incidence. The current annual case count is just about 1,000 in the world, with nearly two-thirds in the Democratic Republic of Congo. But "sleeping sickness has ebbed and returned at many points in history," says Hotez.
Sleeping sickness caused by the Trypanosoma brucei gambiense parasite accounts for more than 90% of cases, and that is the target of the new drug. The illness progresses in two phases: an early, less severe stage marked by fever and headaches, and then, once the parasite crosses the blood-brain barrier, a later phase with more serious neurologic effects, such as confusion and convulsions. At that point, the parasite disrupts brain regions that regulate circadian rhythm, causing patients to become sleepy during the day and awake at night. Without treatment, the disease can progress to coma and death.
Some previous treatments worked only for one stage of the disease, but acoziborole treats both.
"We can't dream to have better than this," says Dr. Wilfried Mutombo Kalonji, head of West and Central Africa Clinical Operations for DNDi, which began its work in 2003 after recognizing that many diseases in low-income countries were curable, but pharmaceutical companies had little financial incentive to develop treatments for people and countries unable to pay for them.
Trying to speed up treatment
Kalonji spoke with NPR from South Ubangi, a remote province in the Democratic Republic of Congo, where he helped lead the clinical trials submitted to the European Medicines Agency. He is now overseeing a new trial to determine whether blood (serologic) tests could allow treatment to begin immediately rather than waiting for confirmatory tests, which take more time, cost more money and generally can't be done in the field.
Monica Mungier, who studies sleeping sickness at the Johns Hopkins Bloomberg School of Public Health but was not involved with development of the new drug, says that the parasite can sometimes evade detection. So a negative test doesn't always mean a patient is not infected.
However, if it is determined that the blood tests are reliable enough to guide care, "then testing and treatment can begin on the same day," says Kalonji. Such a shift explains could increase the number of treated patients and potentially end transmission of the illness because human reservoirs would disappear, says Mungier.
The next step is a review of acoziborole by the Democratic Republic of Congo Ministry of Health and by WHO to see if the agency should update its treatment guidelines, which would help other countries authorize the drug's use. But global health experts worry that future U.S. and Western funding cuts could keep the drug from countries that need it.
Much of the progress toward eliminating sleeping sickness rests on the work of African researchers and patients who took part in the trials, despite difficult conditions. "The clinical trials are challenging," says Kalonji. "Patients are often in remote areas, with no electricity, no water. We had to set up all this, including training health workers, providing internet connections, electricity, and the safe way to get to testing sites, because they were remote. We overcame the challenges."
Fran Kritz is a health policy reporter based in Washington, D.C., and a regular contributor to NPR. She also reports for The Washington Post and Verywell Health.
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