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Three ( 4 . 1 % ) of the 73 patients were positive for MPO - ANCA at 13 , 16 and 17 months , respectively , after the start of PTU therapy .
 Chemical: PTU
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: PTU