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: In early clinical studies with CB 3717 , activity has been seen in breast cancer , ovarian cancer , hepatoma , and mesothelioma .
### Output Text:
In early clinical studies with <span class="chemical">CB 3717</span> , activity has been seen in breast cancer , ovarian cancer , hepatoma , and mesothelioma . 