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: The objective of this review is to summarize practical considerations of argatroban therapy in HIT .
### Output Text:
The objective of this review is to summarize practical considerations of <span class="chemical">argatroban</span> therapy in HIT . 