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: VTD consisted of bortezomib at a dose of 1 . 3 mg / m ( 2 ) and dexamethasone at a dose of 40 mg / day on days 1 , 8 , 15 , and 22 of a 35 - day cycle , with daily oral thalidomide at a dose of 100 mg / day .
### Output Text:
VTD consisted of <span class="chemical">bortezomib</span> at a dose of 1 . 3 mg / m ( 2 ) and <span class="chemical">dexamethasone</span> at a dose of 40 mg / day on days 1 , 8 , 15 , and 22 of a 35 - day cycle , with daily oral <span class="chemical">thalidomide</span> at a dose of 100 mg / day . 