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: As this schedule exerted more toxicity than needed to investigate protective agents , the protection of ICRF - 187 was determined using a dose schedule with lower general toxicity ( 6 weekly doses of 4 mg / kg doxorubicin given i . v . plus 2 weeks of observation ) .
### Output Text:
As this schedule exerted more toxicity than needed to investigate protective agents , the protection of <span class="chemical">ICRF - 187</span> was determined using a dose schedule with lower general toxicity ( 6 weekly doses of 4 mg / kg <span class="chemical">doxorubicin</span> given i . v . plus 2 weeks of observation ) . 