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: Because sirolimus does not share the vasomotor renal adverse effects exhibited by calcineurin inhibitors , it has been designated a ' non - nephrotoxic drug ' .
### Output Text:
Because <span class="chemical">sirolimus</span> does not share the vasomotor renal adverse effects exhibited by calcineurin inhibitors , it has been designated a ' non - nephrotoxic drug ' . 