19595
We previously reported the 6 - O - methyl entity as a prodrug moiety to increase liphophilicity of guanine nucleosides and the ProTide approach applied to 2 ' - C - methyl - 6 - O - methylguanosine has lead to potent HCV inhibitors now in clinical trials .
 6 - O - methyl, guanine nucleosides, 2 ' - C - methyl - 6 - O - methylguanosine
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 6 - O - methyl, guanine nucleosides, 2 ' - C - methyl - 6 - O - methylguanosine