A new system for screening chemicals in bulk to see if they work against neglected diseases has had its first victory – a possible new drug for .
However, the drug will never get to the millions who need it unless someone donates millions of dollars to develop it.
“Schisto” is caused by snail-borne trematode flatworms that penetrate the skin and eventually lay eggs in the liver, gut or bladder. It infects 200 million people worldwide, mostly in Africa, and kills 280,000 a year.
Despite this toll, only one drug is widely used against the disease – praziquantel, which was introduced in the 1980s.
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When an infection is treated with only one drug, resistance can easily evolve. Though, this has so far been rare for schisto, says of Illinois State University in Normal.
Growing resistance
Because of its complicated life cycle in people and snails, and because many human cases are not treated, relatively few worms have been exposed to the drug.
However, with recently by the World Health Organisation and charities such as the , use of the drug is becoming more widespread.
“More resistant cases are likely,” says Williams, “unless we can head them off by combining praziquantel with another drug that works differently.”
To find such a drug, Williams’s team turned to the at the Chemical Genomics Center of the US National Institutes of Health.
Funding vital
Here they screened large numbers of chemicals for any that could block a vital enzyme unique to schistosomes, which protects the worms from damage by oxygen free radicals.
They found several possibilities – the best of which seems safe for mammals, and low doses killed schistosomes in test-tubes and in mice.
Better, it works by a different mechanism to praziquantel, so it should be difficult for worms to evolve resistance to both. And it works best on adult worms, the stage in the organism’s lifecycle when most people are treated.
Williams now wants to test different versions of the chemical to find the one that is the safest for humans, yet the deadliest for the worms.
He hopes trials in humans can start in 5 years. But the team will need a partner with deep pockets to get a drug through clinical trials. As ever with schisto, says Williams, “funding is now the key”.
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