4022
The inhibitory activities of compound 1 and its N - methyl derivative ( 1a ) against porcine respiratory and reproductive syndrome virus ( PRRSV ) , human leukemic K562 cells , and human breast cancer MCF - 7 cells were evaluated .
 N - methyl
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 N - methyl