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: Bortezomib and high - dose dexamethasone - containing regimens are considered to be generally tolerable with few severe bacterial infections in patients with B - cell malignancies .
### Output Text:
<span class="chemical">Bortezomib</span> and high - dose <span class="chemical">dexamethasone</span> - containing regimens are considered to be generally tolerable with few severe bacterial infections in patients with B - cell malignancies . 