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: Performance status ( PS ) and initial lenalidomide dose predicted for treatment discontinuation .
### Output Text:
Performance status ( PS ) and initial <span class="chemical">lenalidomide</span> dose predicted for treatment discontinuation . 