3683
The role of two ATP binding cassette transporters , P - glycoprotein ( P - gp ) and breast cancer resistance protein ( BCRP ) , in transdermal absorption of a typical common substrate was examined in vivo .
 ATP
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 ATP