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: We conducted a 12 - month controlled trial of mazindol , a putative growth hormone secretion inhibitor , in 83 boys with Duchenne dystrophy .
### Output Text:
We conducted a 12 - month controlled trial of <span class="chemical">mazindol</span> , a putative growth hormone secretion inhibitor , in 83 boys with Duchenne dystrophy . 