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: This treatment merits further comparison with other cisplatin - based regimens .
### Output Text:
This treatment merits further comparison with other <span class="chemical">cisplatin</span> - based regimens . 