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In this work we describe the optimization of a lead compound based on the quinazoline template to give a new series of potent pyrido [ 3 , 2 - d ] pyrimidines as histamine H4 receptor antagonists .
 Chemical: quinazoline; Chemical: pyrido [ 3 , 2 - d ] pyrimidines; Chemical: histamine
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: quinazoline; Chemical: pyrido [ 3 , 2 - d ] pyrimidines; Chemical: histamine