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: Three cases were related to cyclosporine , and 1 case was secondary to both cyclosporine and tacrolimus .
### Output Text:
Three cases were related to <span class="chemical">cyclosporine</span> , and 1 case was secondary to both <span class="chemical">cyclosporine</span> and <span class="chemical">tacrolimus</span> . 