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: The patient was treated with steroid pulse , plasmapheresis , cyclophosphamide and antiplatelet agents .
### Output Text:
The patient was treated with <span class="chemical">steroid</span> pulse , plasmapheresis , <span class="chemical">cyclophosphamide</span> and <span class="chemical">antiplatelet agents</span> . 