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: A group of doctors in Boston warn that the protease inhibitor Viracept may cause an irregular heart beat , known as bradycardia , in people with HIV .
### Output Text:
A group of doctors in Boston warn that the protease inhibitor <span class="chemical">Viracept</span> may cause an irregular heart beat , known as bradycardia , in people with HIV . 