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: CI - 921 ( NSC 343499 ; 9 - [ [ 2 - methoxy - 4 - [ ( methylsulphonyl ) amino ] phenyl ] amino ] - N , 5 - dimethyl - 4 - acridinecarboxamide ) is a topoisomerase II poison with high experimental antitumour activity .
### Output Text:
<span class="chemical">CI - 921</span> ( <span class="chemical">NSC 343499</span> ; <span class="chemical">9 - [ [ 2 - methoxy - 4 - [ ( methylsulphonyl ) amino ] phenyl ] amino ] - N , 5 - dimethyl - 4 - acridinecarboxamide</span> ) is a topoisomerase II poison with high experimental antitumour activity . 