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: One of the patients developed cardiac failure after 30 mg m - 2 MMC and only 150 mg m - 2 doxorubicin .
### Output Text:
One of the patients developed cardiac failure after 30 mg m - 2 <span class="chemical">MMC</span> and only 150 mg m - 2 <span class="chemical">doxorubicin</span> . 