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: Systemic toxicity following administration of sirolimus ( formerly rapamycin ) for psoriasis : association of capillary leak syndrome with apoptosis of lesional lymphocytes .
### Output Text:
Systemic toxicity following administration of <span class="chemical">sirolimus</span> ( formerly <span class="chemical">rapamycin</span> ) for psoriasis : association of capillary leak syndrome with apoptosis of lesional lymphocytes . 