Exenatide (Byetta)

• a synthetic version of a peptide (small protein) found in the saliva of the Gila monster (which is for some reason pronounced HEE-la), an intricately-patterned North American lizard capable of storing food in its tail
• is structurally similar to and so mimics the action of glucagon-like peptide 1 (GLP-1), an endogenous (made by the body) incretin (hormone made by the intestine that enhances the secretion of insulin after meals) that is important for regulation of glucose levels in the body and is deficient in diabetics
• enhances glucose-induced insulin release from beta cells in the pancreas
  
• used to treat type II diabetes (doesn't work on type I since people with this form generally have no beta cells, which is why they are diabetic in the first place)
• administered in combination with other anti-diabetic drugs (i.e. as an add-on or adjunctive therapy) to permit better control of glucose levels
• main side effects are nausea and vomiting
  

Mikhail N. Exenatide: a novel approach for treatment of type 2 diabetes. South Med J. 2006 Nov;99(11):1271-9.