Visceral leishmaniasis is transmitted by sand flies

Flickr/Armed Forces Pest Management Board

The second biggest parasitic killer in developing countries, visceral leishmaniasis, could be treated effectively and safely with an existing drug candidate for another neglected disease, sleeping sickness, say scientists.

Visceral leishmaniasis kills up to 60,000 people a year in parts of Africa, Asia and Latin America. It is caused by the parasite Leishmania donovani, which is transmitted by sandflies. The parasite lives in the host's white blood cells where it multiplies before infecting the spleen, liver and bone marrow.

Ninety per cent of all visceral leishmaniasis cases occur in Bangladesh, Brazil, India, Nepal and Sudan, according to the WHO, which aims to eliminate the disease from the Indian subcontinent as part of its new drive to control ten neglected tropical diseases by 2020.

Current treatments include miltefosine, Pentostam and amphotericin B, which are variously costly, toxic, need to be given intravenously, or are losing potency as the parasite gains resistance.

Now researchers at the University of Dundee, United Kingdom, think that fexinidazole, a treatment undergoing phase I trials for African sleeping sickness, might also be a candidate for treating leishmaniasis.

They found that five days of oral treatment with fexinidazole almost completely suppressed the infection in mice. Crucially, the two active agents that fexinidazole is converted into once in the body remain at therapeutic levels for more than a day, meaning a potential treatment may only require a single daily oral dose.

The results were published in Science Translational Medicine last week (1 February).

Alan Fairlamb, lead author of the research, told SciDev.Net that because fexinidazole is already in trials for another disease, this could speed up development of the drug and make it cheaper.

"If you know, through previous clinical trials for other indications, that a drug is well tolerated and has no major safety concerns you can move quickly," he said. "Lessons learned in one trial will inform another. The development [time] has been shortened by several years."

He added that having a once-daily pill of fexinidazole would make treatment in, and delivery to, rural areas easier.

David Horn, a researcher from the UK-based London School of Hygiene & Tropical Medicine, said: "Any multi-purpose, once daily, oral drug that could safely treat both sleeping sickness and leishmaniasis would be very good news."  

However, Michael Chew, science portfolio adviser at the Wellcome Trust, which funded the research, cautioned that the results were only in mice. "Not many drugs get to commercial production and even if they do this often takes a long time," he said.  

Link to full paper in Science Translational Medicine [425kB]