Smart drug zeroes in on sleeping sickness


Antwerp and Ghent universities find new way to treat fatal tropical disease

Deadly parasite

A new drug for the treatment of African sleeping sickness has been discovered by researchers at the universities of Antwerp and Ghent. Effective in animal tests, the drug promises to have significant advantages over existing treatments once developed for use in humans.

Sleeping sickness occurs across much of sub-Saharan Africa, caused by a parasite transmitted by the tsetse fly. Once bitten, someone unlucky enough to catch the bug starts feeling generally unwell and feverish as the parasites multiply in their blood stream.

Then the parasites get into the central nervous system. This causes severe neurological complications, including changes to the sleep cycle that give the disease its name.

"A number of therapies do exist", says Guy Caljon from the Department of Biomedical Sciences at Antwerp University. "However, the drugs currently in use often cause serious side effects and cannot be administered orally, which is a major hurdle for patients in remote areas. They often live far away from a health centre, so they can’t just go and get treated."

With the number of cases falling, the pharmaceutical industry does not see a profit in developing new or improved treatments. "However, it is still important to have an effective drug in reserve, as the disease could always reappear or develop resistance to current treatments."

Designer drug

The treatment he and his colleagues in Antwerp and Ghent have come up with exploits a weakness in the parasite's biology. In order to grow and multiply, the parasite needs a class of chemicals called purine nucleosides. It cannot make these itself, so it scavenges them from the body in which it is living.

So the researchers designed a molecule that looks like the kind of purine nucleoside the parasite needs, but once absorbed has the effect of fouling up its internal chemistry.

This molecule also has the advantage of easily entering the patient's blood stream, so it does not need to be injected, and circulating to the areas of the body where the parasites do the most damage.

"We set out to find substances that could take out the parasite in a specific way," concludes Louis Maes, another Antwerp researcher involved in the project. "It was essential to find an affordable, orally administered drug that could reach the brain."

Photo: Trypanosoma, the parasite that causes sleeping sickness, in human blood
Credit: CDC/Myron G Schultz