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: One patient had complete response , seven had stable disease , none had partial response and five had progressive disease .
### Output Text:
One patient had complete response , seven had stable disease , none had partial response and five had progressive disease . 