In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: For compounds that have shown TDP in the clinic ( terfenadine , terodiline , cisapride ) there is little differentiation between the dog ED50 and the efficacious free plasma concentrations in man ( < 10 - fold ) reflecting their limited safety margins .
### Output Text:
For compounds that have shown TDP in the clinic ( <span class="chemical">terfenadine</span> , <span class="chemical">terodiline</span> , <span class="chemical">cisapride</span> ) there is little differentiation between the dog ED50 and the efficacious free plasma concentrations in man ( < 10 - fold ) reflecting their limited safety margins . 