A drug derived from lizard saliva has been approved by U.S. regulators to treat Diabetes in patients who have not responded to other treatments, the drug’s developers, Eli Lilly and Co. and Amylin Pharmaceuticals Inc., said on Friday.

The drug, exenatide, to be sold under the brand name Byetta, was approved by the U.S. Food and Drug Administration as an add-on therapy for patients with type 2 diabetes - the most common form - whose blood sugar is not sufficiently controlled by two other treatments. The FDA did not approve the drug as a stand-alone treatment.

The drug is made from the saliva of the Gila monster lizard, which lives in the Arizona desert and eats just four times a year. It is the first of a new class of drugs known as incretin mimetics. It mimics hormones released in the human gut in response to food that help regulate glucose levels.

About 18 million people in the United States have diabetes, or 6.2 percent of the population. Diabetics are unable to produce enough insulin or cannot process their insulin properly, resulting in dangerously high blood-sugar levels, which can lead to Heart disease, Blindness and amputations if not treated.