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: Although a dose - response effect has been observed with cisplatin , the dose - limiting toxicities associated with cisplatin ( e . g . , nephrotoxicity , ototoxicity , and neurotoxicity ) have limited its use as a treatment for breast carcinoma .
### Output Text:
Although a dose - response effect has been observed with <span class="chemical">cisplatin</span> , the dose - limiting toxicities associated with <span class="chemical">cisplatin</span> ( e . g . , nephrotoxicity , ototoxicity , and neurotoxicity ) have limited its use as a treatment for breast carcinoma . 