History of GLP-1 Drugs: Full Timeline 2005 to 2026

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The history of GLP-1 drugs is longer and stranger than most patients realize. The first GLP-1 receptor agonist, exenatide (Byetta), was FDA-approved on April 28, 2005 — built from a peptide isolated in the venom of a Gila monster. Liraglutide (Victoza) followed in 2010, semaglutide (Ozempic) in 2017, oral semaglutide (Rybelsus) in 2019, semaglutide for weight loss (Wegovy) in 2021, and the first GIP/GLP-1 dual agonist tirzepatide (Mounjaro) in 2022 with its weight-loss sibling Zepbound in 2023. Two decades of clinical use, multiple cardiovascular outcome trials, and a growing list of approved indications now sit behind these molecules. This article walks the timeline date by date, explains how the molecules evolved, and shows where the PlexusDx Semaglutide Injection, Tirzepatide Injection, and Microdose GLP-1 Protocol fit relative to that history — because the choice you make in 2026 is shaped by science that started in 1902.

The pre-history: incretins, proglucagon, and the missing hormone (1902–1987)

The story does not start with Ozempic. In 1902, Bayliss and Starling identified secretin, the first gut hormone — proof that the intestine sends chemical signals to other organs. By 1906, Liverpool researchers had shown that intestinal extract lowers blood glucose, and in 1932 La Barre coined the term “incretine” for a gut factor that stimulates insulin independently of direct nerve signaling. The 1960s and 1970s brought radioimmunoassay technology and the identification of GIP (glucose-dependent insulinotropic polypeptide) as the first incretin hormone. In 1983, Bell and colleagues cloned the human proglucagon gene, revealing the sequences of GLP-1 and GLP-2. Between 1985 and 1987, Svetlana Mojsov identified the biologically active fragment of GLP-1, and Mojsov, Joel Habener, Daniel Drucker, and Jens Juul Holst proved it stimulates insulin secretion. The molecule was real and powerful — but native GLP-1 had a half-life of roughly two minutes in human plasma, which made it useless as a daily drug. Solving the half-life problem is what produced the medicines on pharmacy shelves today.

The Gila monster connection: how lizard venom unlocked the first GLP-1 drug (1992–2005)

In 1992, Dr. John Eng at the VA Medical Center in the Bronx discovered exendin-4, a peptide in Gila monster venom that mimicked GLP-1 but lasted hours instead of minutes. Exendin-4 became the chemical scaffold for exenatide, and on April 28, 2005, the FDA approved exenatide (Byetta) for type 2 diabetes — the first GLP-1 receptor agonist ever marketed. To be clear about what came from the lizard: native human GLP-1 is produced by L-cells in the human intestine; the first GLP-1 drug used a peptide from Gila monster saliva as a long-acting analog. Subsequent drugs like liraglutide and semaglutide are engineered modifications of the human GLP-1 sequence, not lizard-derived. Byetta was twice-daily injection, the dosing was inconvenient, and the weight loss was real but modest — but the proof of concept was in. A drug class had been born.

The FDA approval era: every major GLP-1 milestone (2005–2019)

The decade and a half after Byetta produced the medications most patients now recognize. 2010: the FDA approved liraglutide (Victoza), the first once-daily GLP-1, engineered at Novo Nordisk by Lotte Knudsen using a fatty-acid side chain to extend half-life. 2012: exenatide extended-release (Bydureon) brought weekly dosing. 2014: the FDA approved liraglutide 3.0 mg (Saxenda) for chronic weight management — the first GLP-1 drug with an obesity indication. 2014: dulaglutide (Trulicity) launched as a weekly diabetes GLP-1. 2017: the FDA approved semaglutide (Ozempic) for type 2 diabetes — the once-weekly molecule that would change everything, with greater A1c reduction and weight loss than its predecessors in the SUSTAIN trial program. 2019: oral semaglutide (Rybelsus) became the first GLP-1 you could swallow, using SNAC absorption-enhancer technology to push a peptide across the gut wall. By the end of the decade the class had expanded from one twice-daily injectable to a portfolio of once-daily and once-weekly options — and the weight-loss signal everyone had noticed in the diabetes trials was about to become its own indication.

The GLP-1 explosion: Wegovy, tirzepatide, and the public awareness shift (2021–2023)

In June 2021, the FDA approved semaglutide 2.4 mg (Wegovy) for chronic weight management based on the STEP trial program, which reported mean weight loss of roughly 15% over 68 weeks. Public awareness moved from clinical journals to celebrity feeds within months. Then in May 2022, the FDA approved tirzepatide (Mounjaro) for type 2 diabetes — the first GIP/GLP-1 dual agonist, hitting two incretin receptors at once and producing larger A1c and weight effects in the SURPASS program than any prior single-mechanism GLP-1. In November 2023, tirzepatide for chronic weight management was approved as Zepbound, with SURMOUNT trial data showing mean weight loss of roughly 21% at the 15 mg dose over 72 weeks. According to FAIR Health, GLP-1 prescribing among adults with an overweight or obesity diagnosis increased 586.7% between 2019 and 2024. Shortages, compounding controversies, and a 2024 Lasker Award honoring Habener, Mojsov, and Knudsen all followed in close succession.

How GLP-1 drugs actually work — mechanism in one paragraph

GLP-1 receptor agonists bind the GLP-1 receptor in the pancreas, brain, gut, and other tissues. In the pancreas they stimulate glucose-dependent insulin secretion and suppress glucagon — lowering blood sugar without driving hypoglycemia in the way older diabetes drugs do. In the gut they slow gastric emptying, which extends satiety after meals. In the brain they act on appetite-regulating centers in the hypothalamus and brainstem, reducing hunger and food preoccupation. Tirzepatide adds a second mechanism: it also activates the GIP (glucose-dependent insulinotropic polypeptide) receptor, the original incretin identified in the 1970s. Hitting both incretin pathways at once is the structural reason tirzepatide produces larger weight effects than semaglutide in head-to-head trial comparisons. The PlexusDx GLP-Squared dual-compound protocol stacks compounded semaglutide and tirzepatide for clinically appropriate patients who want both mechanisms in one regimen.

The pipeline: what's coming after tirzepatide

The pipeline is dense and fast-moving. Retatrutide (Eli Lilly) is a triple agonist hitting GLP-1, GIP, and glucagon receptors; phase 2 weight-loss data published in 2023 reported mean reductions of roughly 24% at the highest dose over 48 weeks, and phase 3 trials are underway. Orforglipron (Eli Lilly) is the first non-peptide oral GLP-1 receptor agonist — a small molecule rather than an injected peptide, with no SNAC absorption-enhancer required — and an FDA decision is anticipated in 2026. Cagrilintide (an amylin analog) combined with semaglutide as “CagriSema” is in late-stage trials for obesity. Oral semaglutide formulations for weight loss are launching alongside the injectables. The class that started with a twice-daily Gila monster peptide is now expanding into oral small molecules and triple agonists — and the dosing decision for any individual patient is going to depend more, not less, on how their biology responds.

Where PlexusDx fits relative to the timeline

PlexusDx Weight Management Protocols use compounded semaglutide and tirzepatide — the same active ingredients in Wegovy, Ozempic, Zepbound, and Mounjaro — prepared by licensed U.S. compounding pharmacies. Compounded semaglutide and tirzepatide are not FDA-approved finished drug products; they are pharmacy-prepared versions of those active ingredients, dispensed under U.S. compounding regulations. Six protocols cover the four main mechanism classes that 20 years of GLP-1 history produced: Microdose GLP-1 Protocol at $129/mo flat across four delivery formats (capsule, troche, lozenge, sublingual); Semaglutide Oral at $209/mo across six dose levels; Semaglutide Injection at $179–$229/mo across five dose levels; Tirzepatide Injection at $229–$309/mo across six dose levels; Tirzepatide Oral at $229–$509/mo across seven dose levels; and GLP-Squared dual-compound at $179–$325/mo. All protocols are all-inclusive cash-pay (clinician consult, prescription, compounded medication, and shipping), no membership fee, available in all 50 states with five states requiring a live consult instead of async intake.

Why genetics belong in the next chapter of GLP-1 history

Twenty years of GLP-1 trials have made one thing clear: response varies meaningfully across patients. Variants in GLP1R (the GLP-1 receptor itself), GIPR (the GIP receptor that tirzepatide also activates), FTO (appetite regulation), MC4R (satiety signaling), and TCF7L2 (insulin response) are associated with measurably different response patterns to semaglutide and tirzepatide. The Precision Peptide Genetic Test maps 48 genes and 57 variants across 14 health pathways — including 34 weight-management insights and the GIPR rs1800437 variant linked to differential GLP-1 response — so the prescribing clinician can anchor titration to the patient's biology rather than the population mean. The test is $298 standalone or $99 as an add-on after the first month of any PlexusDx protocol. Neither the 2005 Byetta launch nor the 2017 Ozempic launch had this option; the next chapter does.

Frequently asked questions

What was the first GLP-1 drug?

Exenatide (Byetta), approved by the FDA on April 28, 2005, for type 2 diabetes. It was derived from exendin-4, a peptide discovered in Gila monster venom by Dr. John Eng at the VA Medical Center in the Bronx. Native human GLP-1 has a roughly two-minute half-life, so an exendin-4-based long-acting analog was the practical entry point for the drug class.

When were GLP-1 drugs first approved for weight loss?

Liraglutide 3.0 mg (Saxenda) was approved for chronic weight management in December 2014 — the first GLP-1 drug with an obesity indication. Semaglutide 2.4 mg (Wegovy) followed in June 2021 and became the more widely used option due to greater efficacy and once-weekly dosing.

Where does GLP-1 come from — is it really from a lizard?

GLP-1 itself is a hormone produced by L-cells in the human intestine. The first GLP-1 drug (exenatide) was based on a peptide from Gila monster saliva, but later drugs like semaglutide and liraglutide are engineered from modified versions of the human GLP-1 molecule, not from lizards.

Who discovered GLP-1?

Identifying GLP-1 as a biologically active hormone involved multiple scientists in the 1980s: Joel Habener, Svetlana Mojsov, Daniel Drucker, and Jens Juul Holst, working across U.S. and Danish institutions. The 2024 Lasker Award recognized Habener, Mojsov, and Lotte Knudsen, who engineered the first long-acting GLP-1 drugs at Novo Nordisk.

When did GLP-1 drugs become popular?

Public awareness surged after the FDA approved Wegovy (semaglutide) for weight loss in June 2021. Celebrity and social media usage amplified interest dramatically. Among adults with an overweight or obesity diagnosis, GLP-1 prescribing increased 586.7% between 2019 and 2024 according to FAIR Health data.

What is the newest GLP-1 drug or pipeline candidate to know?

Tirzepatide (Mounjaro 2022, Zepbound 2023) is the most recent FDA-approved molecule in widespread use. The closest pipeline candidates are orforglipron, the first non-peptide oral GLP-1 from Eli Lilly, with an FDA decision anticipated in 2026, and retatrutide, a triple GLP-1/GIP/glucagon agonist in phase 3.

Are compounded GLP-1 drugs FDA-approved?

No. Compounded semaglutide and compounded tirzepatide are not FDA-approved finished drug products. They are pharmacy-prepared versions of those active ingredients dispensed under U.S. compounding regulations. PlexusDx Weight Management Protocols use compounded semaglutide and tirzepatide from licensed U.S. compounding pharmacies; only branded products like Wegovy, Ozempic, Zepbound, Mounjaro, Saxenda, Rybelsus, Trulicity, and Victoza are FDA-approved finished drugs.

History of GLP-1 Drugs: Complete Timeline From Exenatide (2005) to Tirzepatide and Beyond | PlexusDx