21593
Further pharmacokinetic optimization for sufficient oral absorption and liver triphosphate loading led to identification of a clinical development candidate GS - 6620 .
 Chemical: triphosphate; Chemical: GS - 6620
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: triphosphate; Chemical: GS - 6620