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: Despite therapy with ursodeoxycholic acid , prednisone , and then tacrolimus , her cholestatic disease was unrelenting , with cirrhosis shown by biopsy 6 months after presentation .
### Output Text:
Despite therapy with <span class="chemical">ursodeoxycholic acid</span> , <span class="chemical">prednisone</span> , and then <span class="chemical">tacrolimus</span> , her cholestatic disease was unrelenting , with cirrhosis shown by biopsy 6 months after presentation . 