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: Histopathological examination of kidney , heart and lung sections revealed moderate to massive tissue damage with a variety of morphological aberrations by all the three drugs in the absence of GSPE preexposure than in its presence .
### Output Text:
Histopathological examination of kidney , heart and lung sections revealed moderate to massive tissue damage with a variety of morphological aberrations by all the three drugs in the absence of <span class="chemical">GSPE</span> preexposure than in its presence . 