10793
Thus , PDE5 inhibitors ( PDE5Is ) are thought to be promising new therapeutic agents for the treatment of Alzheimer ' s disease ( AD ) , a neurodegenerative disorder characterized by memory loss .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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