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Old Drugs Show New Promise in Combating Prion Diseases

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Two drugs that doctors have long used to treat malaria and certain psychotic illnesses may one day find a new use. According to findings reported today in the Proceedings of the National Academy of Sciences, the drugs effectively combat infectious prion proteins¿which can cause Creutzfeldt-Jakob disease and other fatal, neurodegenerative orders¿in infected mouse cells.

A prion is a deformed, infectious version of the so-called cellular prion protein, which exists in healthy humans and many animals. The body is thought to regularly rid the brain's nerve cells of misfolded prion proteins. When that doesn't occur, however, the prion sets off a wave of destruction, converting normal proteins into the disease-causing form. In the new study, however, prion research pioneer Stanley B. Prusiner of the University of California at San Francisco and his colleagues found that the malaria drug quinacrine and chlorpromazine, which is approved to treat conditions like schizophrenia, actually inhibited the conversion of normal prion protein into the infectious kind. Indeed, more than three weeks after discontinuing treatment, the infected mouse cells remained free of prion infection.

Though quinacrine proved considerably more potent than chlorpromazine in the cell-based study, chlorpromazine's superior ability to cross the blood-brain barrier may ultimately make it more useful in treating people. Indications of that may come in an upcoming clinical trial, in which the researchers plan to test the two drugs separately and in combination. "It's a big leap from findings in cell culture to those in humans, and we do not know if we will see a favorable response in humans," team member Carsten Korth notes. "But the results we saw, in a cell model we consider valid, make this lead worth pursuing immediately."

Kate Wong is an award-winning science writer and was formerly senior editor for features at Scientific American, where she focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

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