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: Individuals with HIV can now live long lives with drug therapy that often includes protease inhibitors such as ritonavir .
### Output Text:
Individuals with HIV can now live long lives with drug therapy that often includes protease inhibitors such as <span class="chemical">ritonavir</span> . 