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: Neither a tumor - protective effect nor reduced toxicity to normal tissues was observed with the addition of amifostine to cisplatin in this trial .
### Output Text:
Neither a tumor - protective effect nor reduced toxicity to normal tissues was observed with the addition of <span class="chemical">amifostine</span> to <span class="chemical">cisplatin</span> in this trial . 