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: She subsequently died some 5 weeks after the commencement of her drug therapy . Post - mortem examination showed evidence of massive hepatocellular necrosis , acute hypersensitivity myocarditis , focal acute tubulo - interstitial nephritis and extensive bone marrow necrosis , with no evidence of malignancy .
### Output Text:
She subsequently died some 5 weeks after the commencement of her drug therapy . Post - mortem examination showed evidence of massive hepatocellular necrosis , acute hypersensitivity myocarditis , focal acute tubulo - interstitial nephritis and extensive bone marrow necrosis , with no evidence of malignancy . 