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: Notwithstanding these facts our findings suggest that these patients might benefit from relatively mild initial treatment , especially true for patients not previously exposed to this drug .
### Output Text:
Notwithstanding these facts our findings suggest that these patients might benefit from relatively mild initial treatment , especially true for patients not previously exposed to this drug . 