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: Cyclophosphamide ( CP ) , an antitumoral agent known to produce toxic effects on the bladder wall through its main toxic metabolite acrolein , was used to induce cystitis .
### Output Text:
<span class="chemical">Cyclophosphamide</span> ( <span class="chemical">CP</span> ) , an antitumoral agent known to produce toxic effects on the bladder wall through its main toxic metabolite <span class="chemical">acrolein</span> , was used to induce cystitis . 