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: A Phase II trial of cisplatin plus WR - 2721 ( amifostine ) for metastatic breast carcinoma : an Eastern Cooperative Oncology Group Study ( E8188 ) .
### Output Text:
A Phase II trial of <span class="chemical">cisplatin</span> plus <span class="chemical">WR - 2721</span> ( <span class="chemical">amifostine</span> ) for metastatic breast carcinoma : an Eastern Cooperative Oncology Group Study ( E8188 ) . 