When the Food and Drug Administration (FDA) approved Byetta (exenatide) in 2005, doctors thought it was just approving the first glucagon-like peptide-1 (GLP-1) agonist to treat Type 2 diabetes. But this new drug class had the potential to treat a host of other problems.
GLP-1 agonists mimic the body's intrinsic GLP-1, a hormone that stimulates insulin release, suppresses the hormone glucagon, slows the muscles that move food through the intestinal tract, and decreases appetite. GLP-1s indirectly cause weight loss by slowing the movement of food through the stomach and intestines, extending the feeling of fullness. Researchers soon discovered they also directly act on GLP-1 receptors in the brain to reduce appetite and cravings. During clinical trials and postapproval surveillance, clinicians noticed people on GLP-1s losing weight.
Clinicians began prescribing GLP-1s off-label—not for a purpose or in a dose the FDA specifically approved—soon after seeing the drug's weight loss effects. By 2014, the FDA approved the GLP-1 Type 2 diabetes drug Victoza (liraglutide) to treat obesity under a different brand name, Saxenda. Both brands contain the same drug but have different dosing instructions. Since then, other drug manufacturers have followed the same strategy.
