Dr. Sandeep Patil, Dr. Darryle Schoepp tested the new drug, known by its experimental name LY2140023, in 196 patients. “All patients were hospitalized, gradually taken off any pretrial antipsychotic medications, and treated in a double-blind manner for 4 weeks,” the researchers wrote in their study, published in the journal Nature Medicine.

Double-blind means neither the doctors nor the patients knew if they were getting LY2140023, Zyprexa or a placebo. About 32 percent of the patients treated with LY2140023 had fewer hallucinations, delusions and instances of thought disorder, as well as less social withdrawal, apathy and emotional symptoms of schizophrenia, the researchers found. This compared to 41 percent of patients who got Zyprexa, known generically as olanzapine, and just 3 percent of the patients given placebos. But the LY2140023 patients had fewer side-effects. Most were mild, including insomnia or sleepiness, nausea and headache.

The findings suggest that the new class of drugs might offer a different approach for treating schizophrenia, a very serious mental illness that can cause hallucinations and delusions and which affects about 1 percent of the population globally, the researchers said. Current antipsychotic drugs act on a neurotransmitter — a message-carrying chemical in the brain — called dopamine. But blunting the effects of dopamine causes very unpleasant side-effects and schizophrenia patents often stop taking their drugs. The side-effects can also affect their health because weight gain and diabetes can both cause early death.

LY2140023 affects a different brain chemical called glutamate. It is the first of a new class of drugs called mGlu2/3 receptor agonists. “These data suggest that mGlu2/3 receptor agonists have antipsychotic properties and may provide a new alternative for the treatment of schizophrenia,” the researchers wrote. Lilly plans further trials of the drug.

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