New drug shows promise against Asian liver fluke

An experimental drug called tribendimidine could help cure millions of people infected with a parasitic worm known as the Southeast Asian liver fluke, which can cause cancer, Swiss scientists said on Thursday.

In a study in The Lancet medical journal, researchers found that tribendimidine, developed by the Chinese National Institute of Parasitic Diseases, is as safe and effective as the standard treatment for this fluke—a generic drug called praziquantel—and has a cure rate of 70 percent.

In contrast to the new drug, antimalarials such as artemether, artesunate, mefloquine “are ineffective and should not be recommended” for treating the fluke, also known as Opisthorchis viverrini or O viverrini, the researchers said.

“Our results were very encouraging for tribendimidine,” Jennifer Keiser of the Swiss Tropical and Public Health Institute, who led the study, said in a telephone interview.

“The cure rates were much better than praziquantel, but of course we would now need to confirm these results in larger clinical trials. To move forward, this drug would also need to be developed outside China.”

Parasitic worms come in various types and are a problem that Plagues more than a billion people around the world. Over time these parasites have become increasingly resistant to available drugs, raising an urgent need to find new drugs to fight them.

According to the World Health Organization, Opisthorchis caused by parasitic worms is endemic in southeast Asia, the Siberian lowlands and eastern Europe. An estimated 67 million people are at risk of the disease, and 9 million are infected in Cambodia, Laos, and northeastern parts of Thailand and Vietnam.

Infection with this fluke can cause a variety of conditions, including cancers of the bile duct.

The researchers said that since praziquantel is currently the only drug treatment available and concerns are growing about the emergence of resistance to it, they wanted to look at the efficacy of other potential treatments.

Besides tribendimidine, which is licensed in China for use in people but has not been registered outside China, the antimalarial drugs artemether, artesunate and mefloquine have shown potential against the infection in studies on animals.

Keiser’s team conducted a trial to assess the safety and efficacy of these drugs compared with praziquantel in school children in Laos, where prevalence of Opisthorchis viverrini infection is higher than 50 percent.

They treated 125 infected children with one of five options and measured the effects by cure rate and by each drug’s ability to clear eggs laid by the parasites in their human hosts.

The highest cure rate of 70 percent was seen in patients treated with tribendimidine, followed by 56 percent for those treated with praziquantel. Just four percent of children taking combined mefloquine and artesunate were cured, and four percent of those on artesunate only. No child was cured with mefloquine.

Praziquantel and tribendimidine were also found to be “significantly more effective” than the others at clearing eggs, Keiser’s team said.

By Kate Kelland

LONDON