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: Four patients had five infusion - related reactions during the infusion of liposomal doxorubicin , leading to treatment discontinuation in three patients .
### Output Text:
Four patients had five infusion - related reactions during the infusion of liposomal <span class="chemical">doxorubicin</span> , leading to treatment discontinuation in three patients . 