GLP-1 Research Timeline: From Discovery to Modern Medicine

It is easy to assume that drugs like Ozempic and Wegovy appeared suddenly, conjured by marketing and a fortunate clinical accident. The truth is slower and more interesting. The molecule these medicines imitate — glucagon-like peptide-1, or GLP-1 — was teased out of the body over the course of the 1980s, and the path from that discovery to a once-weekly injection that reliably produces double-digit weight loss took the better part of forty years. Along the way it passed through an Arizona lizard, a string of cautious diabetes approvals, and a set of trials large enough to change how the medical profession thinks about obesity itself.

This page sets out that history in order. It is meant as a reference — a single place to check who established what, and in which year — rather than a polemic. If you want the underlying biology first, our explainer on what GLP-1 is covers the hormone itself, and how GLP-1 influences satiety describes what it does once it reaches the brain. What follows is the chronology.

The discovery timeline

The dates below condense the long arc from a metabolic curiosity in the 1960s to the obesity medicines of the 2020s. Each milestone is anchored to the peer-reviewed literature or to the relevant regulatory decision; the eras that group them are explained in the sections that follow.

The incretin puzzle and the characterisation of GLP-1

The story begins not with weight but with sugar. By the mid-1960s, researchers had noticed something that did not quite add up: a dose of glucose swallowed by mouth provoked a far larger release of insulin than the identical dose delivered straight into a vein. The gut, it seemed, was telling the pancreas to prepare for food before the bloodstream had registered any of it. The hormones responsible for this anticipatory signal were named incretins, and the hunt for them defined a generation of endocrinology.

The first incretin to be pinned down was GIP, characterised in the early 1970s after John Brown and colleagues in British Columbia purified it from gut extracts. GLP-1 took longer, because it was hiding in plain sight. In the early 1980s, Joel Habener's laboratory and Graeme Bell's group, working separately, sequenced the gene for proglucagon — the large precursor protein that the body snips into smaller active fragments. Tucked inside that precursor, alongside glucagon itself, were peptides nobody had yet assigned a job. Two of them were glucagon-like, and were duly named GLP-1 and GLP-2; the first of those would prove to be the prize.

What was not obvious at first was which fragment mattered. The full-length peptide predicted by the gene sequence turned out to be largely inert. The active hormone was a shorter, processed form, and identifying it correctly was the difference between a curiosity and a drug target. That distinction is why the mid-1980s work on the truncated peptide was so consequential.

The crucial work came between 1986 and 1987. Svetlana Mojsov, working with Habener at Massachusetts General Hospital, established the precise form of the active peptide — a truncated version, GLP-1(7-36) amide — and showed that it was a remarkably potent stimulus to insulin release. Crucially, it acted only when blood glucose was high, which is what makes the hormone, and the drugs that mimic it, comparatively safe from the standpoint of hypoglycaemia. In parallel, Jens Juul Holst in Copenhagen developed the assays that proved GLP-1 was secreted from the gut in response to a meal. The recognition of this trio's contribution came much later, with a 2024 Lasker Award shared by Mojsov, Habener and Novo Nordisk's Lotte Bjerre Knudsen.

By the close of the 1980s, then, the basic biology was in hand. GLP-1 was a gut hormone that prompted glucose-dependent insulin secretion, suppressed glucagon, slowed the emptying of the stomach and, as later work would confirm, acted on the brain to curb appetite. It looked like an ideal diabetes drug. There was only one problem, and it was a serious one: the natural hormone is destroyed within about two minutes of entering the bloodstream. A molecule that vanishes that quickly cannot be turned into a practical medicine. Solving that durability problem is the thread that runs through everything that follows.

The Gila monster and the exenatide breakthrough

The solution arrived from an unlikely direction. In 1992, John Eng, an endocrinologist at a Veterans Affairs hospital in the Bronx, was investigating the venom of the Gila monster, Heloderma suspectum, a slow and venomous lizard native to the American south-west. Eng isolated a 39-amino-acid peptide he named exendin-4. It shared roughly half its sequence with human GLP-1 and switched on the same receptor — but, vitally, it resisted the enzyme that destroys the human hormone so quickly. Here was a naturally occurring, long-acting GLP-1 analogue. The lizard, which eats only a handful of times a year, appeared to have evolved the very molecule diabetes researchers had been trying to engineer.

Turning that finding into a drug took more than a decade of synthesis, animal work and clinical trials. The decisive human evidence arrived in 2004, when John Buse and colleagues reported in Diabetes Care that exenatide meaningfully improved glycaemic control in people with type 2 diabetes already taking a sulfonylurea — a trial from the programme that supported approval. The synthetic version of exendin-4, exenatide, was duly cleared by the United States Food and Drug Administration in 2005 under the brand name Byetta. It was the first GLP-1 receptor agonist to reach patients. Twice-daily injection was a meaningful burden, and the weight loss it produced was modest by today's standards, but the principle was now proven in humans: stimulate the GLP-1 receptor with something the body cannot immediately dismantle, and blood sugar improves. The class had been born, and the race to make it more convenient and more powerful was on. Our overview of FDA-approved GLP-1 medications traces how that class has since expanded.

The first approvals: building a class

The next advance was a more human molecule. Novo Nordisk's liraglutide was engineered from the human GLP-1 sequence with modifications — including a fatty-acid chain that binds to albumin in the blood — that stretched its action out to roughly a full day. Liraglutide was approved for type 2 diabetes in 2010 as Victoza, replacing twice-daily dosing with a single daily injection. It was a clear improvement, and it hinted at something the diabetes trials kept showing as a side note: patients were losing weight.

That observation was pursued deliberately. In 2014 a higher dose of liraglutide was approved specifically for chronic weight management, under the name Saxenda — the first of the modern GLP-1 medicines licensed for obesity rather than diabetes. The weight loss it delivered, averaging in the region of 5 to 8 per cent of body weight, was respectable but not transformative. The transformation required a longer-acting molecule still.

That molecule was semaglutide, again from Novo Nordisk. Further modifications extended its half-life to about a week, allowing once-weekly injection. Semaglutide was approved for type 2 diabetes in 2017 as Ozempic, the brand name that would soon become shorthand for the entire category. Two years later, in 2019, an oral formulation reached the market as Rybelsus — the first GLP-1 receptor agonist available as a tablet, a genuine pharmaceutical feat given how readily peptides are digested. For a closer look at the molecule, see our piece on semaglutide explained and the mechanism behind how semaglutide works for weight loss.

The obesity era: semaglutide and tirzepatide

By 2017, doctors prescribing Ozempic for diabetes were seeing weight loss substantial enough that the obesity question could no longer be treated as incidental. Novo Nordisk ran the higher-dose semaglutide through a dedicated programme of obesity trials, the STEP studies. The headline result, published in The New England Journal of Medicine in 2021, was striking: in the STEP 1 trial led by John Wilding, adults with overweight or obesity but without diabetes lost an average of just under 15 per cent of their body weight over 68 weeks, against roughly 2.4 per cent on placebo. On the strength of those data, semaglutide was approved for chronic weight management in 2021 as Wegovy — the first genuinely powerful obesity medicine the field had produced.

The bar rose again almost immediately. Eli Lilly's tirzepatide took a different approach, activating not one receptor but two: the GLP-1 receptor and the GIP receptor, the other major incretin. This dual agonism appeared to amplify the effect. Tirzepatide was approved for type 2 diabetes in 2022 as Mounjaro. The obesity data, from the SURMOUNT-1 trial reported by Ania Jastreboff and colleagues, were the most dramatic yet: average weight loss of around 21 per cent at the highest dose over 72 weeks, a figure approaching the territory of bariatric surgery. Tirzepatide gained its obesity licence in 2023 as Zepbound. Our summaries of the Zepbound clinical-trial results and of how tirzepatide works go into the numbers, and a broader survey sits in our overview of the clinical studies behind GLP-1 drugs.

What changed in this era was not only the magnitude of the effect but the framing. Patients consistently described the quieting of an intrusive, constant preoccupation with food — what many now call food noise. That subjective shift, together with the trial data, helped recast obesity as a disorder of appetite regulation rather than a failure of resolve. Our pillar on appetite regulation sets out that argument at length.

Cardiovascular outcomes and expanding indications

A drug that produces weight loss is useful. A drug that demonstrably reduces heart attacks and strokes is something else entirely — it becomes a treatment a cardiologist will reach for regardless of the number on the scale. The pivotal evidence here came from the SELECT trial, reported in 2023. It enrolled more than 17,000 adults who had established cardiovascular disease and were overweight or obese, but who did not have diabetes — a population in whom GLP-1 drugs had not previously been tested for hard outcomes. Semaglutide reduced the risk of major adverse cardiovascular events by roughly 20 per cent compared with placebo.

That result mattered out of proportion to its size, because it severed the link between these medicines and diabetes in the regulatory imagination. It established that the benefit of treating obesity could be measured in cardiovascular events prevented, not merely in kilograms lost. The finding also reframed the cost-benefit conversation: a treatment that prevents heart attacks and strokes is judged by a different standard from one that simply reduces weight, and health systems weighing whether to fund these drugs at scale now had outcome data rather than surrogate measures to consider.

In the wake of SELECT, the indications have continued to widen — into heart failure with preserved ejection fraction, obstructive sleep apnoea, chronic kidney disease and beyond — as trials report across one organ system after another. Much of this breadth is thought to follow from GLP-1 receptors being distributed widely through the body, not only in the pancreas and gut but in the heart, kidney and brain, so that a single agonist can act in several places at once. The pattern suggests that what looked at first like a glucose-lowering drug, then a weight-loss drug, may be better understood as a treatment for the broad metabolic disease that obesity represents.

What the timeline reveals

Read end to end, the chronology carries a few lessons worth stating plainly. The first is patience: nearly forty years separated the characterisation of GLP-1 from the obesity medicines built on it, and most of that time was spent solving the dull but decisive problem of how to make the signal last. The second is the value of curiosity-driven and even accidental science — the incretin puzzle was pure physiology, and the breakthrough analogue came from lizard venom that no one was studying with diabetes in mind. The third is that effect sizes climbed steadily, from the modest weight loss of early exenatide to the surgery-adjacent figures of tirzepatide, as each generation of molecule was refined.

The history is not finished. Triple agonists, longer-acting formulations and oral versions of the most potent drugs are already in trials, and the list of conditions in which these medicines help continues to grow. For the wider scientific context, our GLP-1 science category collects the explainers, and the GLP-1 science hub gathers the deeper material in one place. What began as a question about why oral glucose releases more insulin has become one of the defining stories in modern medicine — and, on present evidence, it is still being written.