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: Results thus far suggest no dose - response effect for paclitaxel doses above 200 mg / m2 .
### Output Text:
Results thus far suggest no dose - response effect for <span class="chemical">paclitaxel</span> doses above 200 mg / m2 . 