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: The mechanisms of sirolimus - associated proteinuria are multifactorial and may be due to an increase in glomerular capillary pressure following calcineurin inhibitor withdrawal .
### Output Text:
The mechanisms of <span class="chemical">sirolimus</span> - associated proteinuria are multifactorial and may be due to an increase in glomerular capillary pressure following calcineurin inhibitor withdrawal . 