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We identified a series of 4 - hydroxypyridazin - 3 ( 2H ) - one derivatives as novel DAAO inhibitors with high potency and substantial cell permeability using fragment - based drug design .
 4 - hydroxypyridazin - 3 ( 2H ) - one
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 4 - hydroxypyridazin - 3 ( 2H ) - one