26648
Altogether , these properties highly distinguish APR19 from RU486 and likely its derivatives , suggesting that it belongs to a new class of pure antiprogestins which inactivate PR by a passive mechanism .
 APR19, RU486
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 APR19, RU486