2144
Further studies are needed to determine the most appropriate nucleoside or nucleotide analogue for antiviral prophylaxis during CT and the optimal duration of administration after completion of CT .
 nucleoside, nucleotide
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 nucleoside, nucleotide