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: Although 25 mg of lamivudine was slightly less effective than 100 mg ( P = . 011 ) and 300 mg ( P = . 005 ) , it still induced 94 % suppression of HBV DNA after the fourth week of therapy .
### Output Text:
Although 25 mg of <span class="chemical">lamivudine</span> was slightly less effective than 100 mg ( P = . 011 ) and 300 mg ( P = . 005 ) , it still induced 94 % suppression of HBV DNA after the fourth week of therapy . 