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: We postulate that the mechanism of the simvastatinezetimibe - induced hepatotoxicity is the increased simvastatin exposure by ezetimibe inhibition of UGT enzymes .
### Output Text:
We postulate that the mechanism of the <span class="chemical">simvastatinezetimibe</span> - induced hepatotoxicity is the increased <span class="chemical">simvastatin</span> exposure by <span class="chemical">ezetimibe</span> inhibition of UGT enzymes . 