Category:GLP-1 receptor agonists: Difference between revisions

The glucagon-like peptide-1 receptor agonists, usually abbreviated GLP-1 receptor agonists, or GLP-1 RAs, are a class of medicines used to treat type 2 diabetes and obesity, and increasingly used to reduce cardiovascular and kidney risk. Within roughly two decades of the first approval they have become some of the most widely used and most discussed medicines in the world. Their history is unusual: it begins not with the modification of an older drug, but with a lizard.

By the 1980s researchers had identified glucagon-like peptide-1 (GLP-1), a hormone released by the gut after eating. It was an appealing target for a diabetes medicine because it prompts the pancreas to release insulin chiefly when blood sugar is high, rather than indiscriminately. But GLP-1 itself was useless as a drug: the body breaks it down within minutes, and the high doses needed to overcome that caused severe nausea.^[1]

The breakthrough came from an unexpected direction. In 1992 John Eng, a researcher at a Veterans Affairs medical center in the Bronx, was systematically screening animal venoms for bioactive peptides. In the venom of the Gila monster, a venomous lizard of the southwestern United States, he identified a peptide he named exendin-4. It closely resembled human GLP-1 and acted on the same receptor, but, crucially, it resisted the rapid breakdown that had defeated GLP-1 itself.^[2] The Gila monster eats only a few times a year, and exendin-4 is thought to have evolved to regulate its digestion after rare, large meals.^[3]

Eng's employer declined to patent the discovery, so he filed the patent himself in 1993, and then spent several years trying to interest a pharmaceutical company in developing it.^[1] A synthetic version of exendin-4, named exenatide, was eventually developed and, in 2005, approved as the first GLP-1 receptor agonist, sold as Byetta.^[3]

The medicines that followed traced a striking expansion of use. Exenatide and the early agents required injection once or twice daily; later molecules were engineered for far longer action. Liraglutide was approved for type 2 diabetes in 2010 and, at a higher dose, for obesity in 2014. Dulaglutide, a once-weekly agent, followed in 2014. Semaglutide was approved in 2017, later also in an oral form, and tirzepatide, which acts on a second gut-hormone receptor (GIP) as well as the GLP-1 receptor, was approved in 2022.^[3]

The expansion was driven by a long series of large clinical trials, and it ran in a consistent direction: from blood-sugar control, to weight loss, to the prevention of cardiovascular and kidney disease. Trials reported substantial weight reduction with the newer agents; cardiovascular outcome trials reported reductions in cardiovascular events, including, in the SELECT trial, a roughly twenty per cent reduction in major adverse cardiovascular events with semaglutide in people with obesity but without diabetes;^[4] and further trials examined kidney outcomes and other conditions. Head-to-head trials have compared agents directly, with tirzepatide generally producing greater average weight loss than semaglutide.^[5] This steady widening of approved uses, sometimes described as problem expansion, is the defining feature of the class's short history, and the reason these medicines moved within two decades from a niche diabetes treatment to a central place in medicine and in public attention.

GLP-1 receptor agonists are understood to act by stimulating the GLP-1 receptor, mimicking the natural hormone. Several effects are associated with this action: the glucose-dependent release of insulin from the pancreas and suppression of glucagon, which lowers blood sugar; slowed emptying of the stomach; and effects on appetite mediated by the brain, which reduce food intake.^[3] The weight loss produced by the class is generally attributed chiefly to reduced food intake. The cardiovascular and kidney benefits seen in trials are thought to arise partly through weight loss and improved blood sugar and partly through more direct effects, though the relative contribution of each is not fully established. As with medicines generally, that these agents bind and activate the GLP-1 receptor is well established; the fuller relationship between that action and the range of clinical effects continues to be investigated.

The GLP-1 receptor agonists include exenatide, liraglutide, dulaglutide, semaglutide, and lixisenatide. Tirzepatide is sometimes grouped with them but is more precisely a dual agonist, acting at both the GLP-1 and the GIP receptor. Several agents are widely known by brand name, semaglutide is sold as Ozempic and Rybelsus for diabetes and as Wegovy for obesity; tirzepatide as Mounjaro and Zepbound; liraglutide as Victoza and Saxenda, the same molecule often carrying different brand names, doses, and approved uses. The list is not exhaustive, and the class is expanding.

The most common adverse effects of GLP-1 receptor agonists are gastrointestinal, nausea, vomiting, diarrhoea, and constipation, which are frequent, especially as the dose is increased, and lead some people to stop treatment. Because the medicines slow gastric emptying, anesthesia guidance has been issued on managing them before surgery.

Several more serious concerns have been studied. The class carries a boxed warning in the United States regarding thyroid C-cell tumours, based on findings in rodents; human data have not established a corresponding increased risk of thyroid cancer, and the warning remains a precaution. Pancreatitis has long been discussed as a possible risk and continues to be examined. A more recent signal concerns the eye: some studies have reported an association between semaglutide and non-arteritic anterior ischemic optic neuropathy (NAION), a form of sudden vision loss; the relative risk reported is modest and the absolute risk low, and the association is still under investigation.^[6] Earlier concern about a possible risk of suicidal thoughts was examined in a large analysis covering 91 placebo-controlled trials and roughly 108,000 patients; in January 2026 the US Food and Drug Administration reported that it had not found an increased risk and requested removal of the related warning language from the labels of GLP-1 receptor agonist medicines.^[7] Figures for all of these risks are population estimates that vary between studies, and individual response varies considerably between people.