For millions of people suffering from Alzheimer's disease, an experimental drug from Eli Lilly & Co. may now be their last hope for treatment.

Pharmaceutical giants Pfizer and Johnson & Johnson pulled the plug on their joint development of a similar Alzheimer's therapy, after that drug failed to show any benefit in two late-stage studies. Lilly has said it will release its findings by the end of September.

The stakes are high, for the 5.4 million people in the United States who have been diagnosed with Alzheimer's and for Lilly. No medicines on the market slow the progression of the disease, the most common form of dementia. If Lilly's drug proves a success, treatments could begin as early as next year and the Indianapolis-based company could realize billions in revenue. Still, company executives have warned that a successful outcome for the drug, called solanezumab, is a longshot.

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