19928
Compounds 21 , 25 , and 39 proved to be active DHFR inhibitors with IC50 range of 0 . 3 - 0 . 8 mu M .
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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:
 None