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For the second time, an experimental drug has been shown to reduce the cognitive decline associated with Alzheimer’s disease. On 3 May, pharmaceutical company Eli Lilly announced in a press release that its monoclonal antibody donanemab slowed mental decline by 35% for some participants in a 1,736-person trial — a rate comparable to that for competitor drug lecanemab. But researchers warn that until the full results are published, questions remain as to the drug’s clinical usefulness, as well as whether the modest benefit outweighs the risk of harmful side effects.