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: Prolonged treatment with losartan showed further reduction of glomerulosclerosis associated with reduced progression of tubular atrophy and interstitial fibrosis , thus preventing heavy proteinuria and chronic renal failure .
### Output Text:
Prolonged treatment with <span class="chemical">losartan</span> showed further reduction of glomerulosclerosis associated with reduced progression of tubular atrophy and interstitial fibrosis , thus preventing heavy proteinuria and chronic renal failure . 