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: These insights might have useful implications for future studies utilizing B1R antagonists for treatment of human DOX cardiomyopathy .
### Output Text:
These insights might have useful implications for future studies utilizing B1R antagonists for treatment of human <span class="chemical">DOX</span> cardiomyopathy . 