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 preliminary results suggest that BNP may be useful as an early and sensitive indicator of anthracycline - induced cardiotoxicity .
### Output Text:
These preliminary results suggest that BNP may be useful as an early and sensitive indicator of <span class="chemical">anthracycline</span> - induced cardiotoxicity . 