22732
Subsequent hit to lead follow - up confirmed the activity of the chemotype , and a structure - based design approach using protein - ligand crystal structures of the beta 1AR resulted in the identification of several fragments that bound with higher affinity , including indole 19 and quinoline 20 .
 indole, quinoline
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 indole, quinoline