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Extensive structure activity relationship studies ultimately led to identification of pyrazolodiazepinone , 22 , which was > 1000 - fold selective for PDE2 over recombinant , full length PDEs 1B , 3A , 3B , 4A , 4B , 4C , 7A , 7B , 8A , 8B , 9 , 10 and 11 .
 Chemical: pyrazolodiazepinone
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: pyrazolodiazepinone