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 review considers anemia associated with sirolimus , including its presentation , mechanisms , and management .
### Output Text:
This review considers anemia associated with <span class="chemical">sirolimus</span> , including its presentation , mechanisms , and management . 