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: Moreover , the inhibitory effect of NIK - 247 on AChE was reversible .
### Output Text:
Moreover , the inhibitory effect of <span class="chemical">NIK - 247</span> on AChE was reversible . 