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Retinal toxicity of chloroquine has been known for several years , but the mechanism ( s ) of toxicity remain controversial ; some author support the idea that the binding of chloroquine to melanin pigments in the retinal pigmented epithelium ( RPE ) play a major toxic role by concentrating the drug in the eye .
 Chemical: chloroquine; Chemical: chloroquine
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: chloroquine; Chemical: chloroquine