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: While lovastatin and simvastatin have been associated with toxic myopathy , pravastatin - associated myopathy could represent a distinct , inflammatory entity .
### Output Text:
While <span class="chemical">lovastatin</span> and <span class="chemical">simvastatin</span> have been associated with toxic myopathy , <span class="chemical">pravastatin</span> - associated myopathy could represent a distinct , inflammatory entity . 