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: Here , the impact of p53 inhibition on acute vs . late - stage DOX cardiotoxicity was examined in a juvenile model .
### Output Text:
Here , the impact of p53 inhibition on acute vs . late - stage <span class="chemical">DOX</span> cardiotoxicity was examined in a juvenile model . 