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: Treatment of ifosfamide - induced urothelial toxicity by oral administration of sodium 2 - mercaptoethane sulphonate ( MESNA ) to patients with inoperable lung cancer .
### Output Text:
Treatment of <span class="chemical">ifosfamide</span> - induced urothelial toxicity by oral administration of <span class="chemical">sodium 2 - mercaptoethane sulphonate</span> ( <span class="chemical">MESNA</span> ) to patients with inoperable lung cancer . 