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 used an in vitro model of chemotherapy induced peripheral neuropathy that closely mimic the in vivo condition by exposing primary cultures of dorsal root ganglion ( DRG ) sensory neurons to paclitaxel and cisplatin , two widely used and highly effective chemotherapeutic drugs .
### Output Text:
We used an in vitro model of chemotherapy induced peripheral neuropathy that closely mimic the in vivo condition by exposing primary cultures of dorsal root ganglion ( DRG ) sensory neurons to <span class="chemical">paclitaxel</span> and <span class="chemical">cisplatin</span> , two widely used and highly effective chemotherapeutic drugs . 