7226
Agonists to S1P ( 1 ) are currently in use clinically for the treatment of multiple sclerosis , and these drugs may act on both S1P ( 1 ) expressed on lymphocytes and S1P ( 1 ) expressed within the central nervous system .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 None