Sleeping sickness, Chagas disease and Leishmaniasis kill thousands each year but little funding has been put into their study so far.
Scientists are putting their hope on a drug that could cure three tropical diseases caused by similar parasites affecting millions, mostly in Africa, Asia and Latin America.
In the three million compounds tested, Chagas disease caused by the Trypansosoma cruzi parasite, leishmaniasis caused by infection with Leishmania parasites and sleeping sickness caused by Trypanosoma brucei parasite, were treated in mice. Scientists are running safe tests before conducting human trials.
A study published in the journal Nature shows the compound causes no harm to human cells.
Scientists at the Genomics Institute of the Novartis Research Foundation found that all three diseases are caused by similar parasites called kinteoplastids that share the same biology. Genetics led them to believe that a common cure could be possible.
Existing treatments are expensive, not effective and sometimes toxic.
All three diseases kill more than 50,000 people per year but are neglected in terms of funding, the research team said.
The scientists involved in the research identified a compound called GNF6702 that could treat Trypanosoma brucei, Trypansosoma cruzi and Leishmania parasites.
"We found that these parasites harbour a common weakness. We hope to exploit this weakness to discover and develop a single class of drugs for all three diseases," said Frantisek Supek, who led the study.
"What makes it special is the fact it is targeting all three parasites. That's the first time it has been done, so it is quite special," Dr Elmarie Myburgh, one of the researchers, told BBC News.
"To me this is obviously a big deal, I'm in this field to try and make a difference, to get to a cure, and we're working hard in the hope that it gets to patients."
"There's been very little incentive to spend a lot of money on these diseases as they affect a very poor, and yet large, population."