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: Peripheral neuropathy has been noted as a complication of therapy with perhexiline maleate , a drug widely used in France ( and in clinical trials in the United States ) for the prophylactic treatment of angina pectoris .
### Output Text:
Peripheral neuropathy has been noted as a complication of therapy with <span class="chemical">perhexiline maleate</span> , a drug widely used in France ( and in clinical trials in the United States ) for the prophylactic treatment of angina pectoris . 