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: BACKGROUND : Several studies have demonstrated liposomal doxorubicin ( Doxil ) to be an active antineoplastic agent in platinum - resistant ovarian cancer , with dose limiting toxicity of the standard dosing regimen ( 50 mg / m ( 2 ) q 4 weeks ) being severe erythrodysesthesia ( " hand - foot syndrome " ) and stomatitis .
### Output Text:
BACKGROUND : Several studies have demonstrated liposomal <span class="chemical">doxorubicin</span> ( <span class="chemical">Doxil</span> ) to be an active antineoplastic agent in <span class="chemical">platinum</span> - resistant ovarian cancer , with dose limiting toxicity of the standard dosing regimen ( 50 mg / m ( 2 ) q 4 weeks ) being severe erythrodysesthesia ( " hand - foot syndrome " ) and stomatitis . 