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Vildagliptin , in addition to metformin , proved to be effective in improving beta - cell function and in reducing insulin resistance measurements .
 Vildagliptin, metformin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 Vildagliptin, metformin