New drug holds promise for parasitic worm disease
By Julie Steenhuysen
CHICAGO (Reuters) - U.S. researchers have discovered a promising new drug for schistosomiasis -- a parasitic worm disease that affects more than 200 million people in 70 countries.
The compound killed worms in the lab, and cured mice infected with the disease, said David Williams of Illinois State University, who reported his findings on Sunday in the journal Nature Medicine.
The only existing drug that works against schistosomiasis, praziquantel, is more than 20 years old.
"There is nothing else you could go to if the parasite evolves resistance," Williams said in a telephone interview. He said about 100 million people will take the drug this year.
"When you treat as many people as are being treated, it is likely drug resistance will evolve," he said.
Schistosomiasis is caused by flatworms that live in snail-invested fresh water. Water becomes contaminated by worm eggs when infected people urinate or defecate in it.
When people wade, swim or bathe in contaminated water, microscopic worms bore through the skin and travel in the blood, causing anemia, diarrhea, internal bleeding, organ damage and death.
Williams said his lab has been looking for unique characteristics of the parasite that would make it vulnerable, without harming the human host.
They found that the parasite has a unique way of disarming toxic oxygen radicals -- charged particles -- and they went to work finding compounds that would attack this weakness.
They teamed up with colleagues at the National Institutes of Health's Chemical Genomics Center, which screened 70,000 potential compounds. This turned up two classes of chemicals, or a total of 10 promising compounds.
DEADLY TO WORMS
"One of these compounds was very effective at killing the worms in very low concentrations," Williams said.
"When we took the same compound and used in experimental infections in mice, we could cure the mice of the disease," he added. Williams said none of the mice in the study had any ill effects from the treatment.
"Our current work is to take this lead compound and develop it into something we can use in humans," Williams said. "It's a pretty inexpensive molecule. It is pretty simple to synthesize in the lab."
The challenge will be able to develop a cheap drug that is as effective as the current drug, which is available generically. "We have a very, very high standard to reach to get something into market that will be competitive," he said.
Researchers at Brown University this month said the impact from schistosomiasis was even more widespread than previously thought. They estimated that 20 million people worldwide have severe and debilitating schistosomiasis, and nearly 800 million people are at risk.
"The search for new drugs for schistosomiasis is imperative if we are to control this devastating disease that exacts an enormous toll, both in terms of human suffering and slowed economic development," said Dr. Anthony Fauci, director of National Institute of Allergy and Infectious Diseases. (Editing by Maggie Fox and Doina Chiacu)