Forty years of GLP-1, condensed.
From a hormone first characterized in a Boston lab to a class projected to exceed $150B in annual revenue by the end of the decade. Every approval, key trial, and structural milestone — in chronological order, with the why, not just the when.
~$1B→ ~$50B+ class revenue, 2017 vs 2025
The GLP-1 class crossed from a niche diabetes category into one of the largest pharmaceutical categories in history within eight years of Ozempic’s launch — driven first by off-label weight management, then by the SELECT cardiovascular outcomes trial that reshaped how payers think about the entire class.
Discovery
- 19861986Discovery
GLP-1 hormone characterized
Researchers Habener, Mojsov, and colleagues at Massachusetts General Hospital identify glucagon-like peptide-1 as a product of the proglucagon gene. The active fragment GLP-1 (7-37) is shown to stimulate insulin release in a glucose-dependent manner — the foundation that everything else is built on.
- 19921992Discovery
Exendin-4 isolated from Gila monster saliva
John Eng at the Bronx VA discovers exendin-4 — a 39-amino-acid peptide in Heloderma suspectum venom that activates the human GLP-1 receptor and resists rapid breakdown. This becomes the molecular template for the first GLP-1 drug.
First-generation
- 2005April 2005First-generation
Byetta (exenatide) — first GLP-1 approved
FDA approves Byetta (exenatide), a synthetic version of exendin-4, for type 2 diabetes. Twice-daily injection. Modest weight loss (~2 kg) was a notable side effect, hinting at the obesity opportunity that would take another 16 years to fully unlock.
- 2010January 2010First-generation
Victoza (liraglutide) — first long-acting GLP-1
Novo Nordisk's Victoza launches in the US as a once-daily injection for type 2 diabetes. The lipid side chain that allows once-daily dosing becomes the design template later refined into semaglutide.
- 2012January 2012First-generation
Bydureon — first once-weekly GLP-1
Once-weekly extended-release exenatide reaches the market. The microsphere formulation is novel but injection-site nodules become a known side effect.
- 2014September 2014First-generation
Trulicity (dulaglutide) — gentle autoinjector
Eli Lilly launches dulaglutide as a once-weekly injection with a hidden-needle autoinjector design that becomes the gold standard for needle-averse patients.
- 2014December 2014First-generation
Saxenda — first GLP-1 approved for obesity
FDA approves liraglutide 3.0 mg (Saxenda) for chronic weight management. Daily injection, ~5–8% mean weight loss in SCALE trials. The category proves obesity is a payer-acceptable indication.
Semaglutide era
- 2017December 2017Semaglutide era
Ozempic (semaglutide) approved for T2D
Once-weekly semaglutide launches for type 2 diabetes. Phase 3 SUSTAIN trials demonstrate superior A1c reduction vs. existing GLP-1s. Off-label weight loss reports begin proliferating immediately.
- 2019September 2019Semaglutide era
Rybelsus — first oral GLP-1
Oral semaglutide launches with the absorption enhancer SNAC. Empty-stomach dosing ritual is required. Provides a needle-free option but bioavailability remains low (~1%).
- 2021June 2021Semaglutide era
Wegovy approved for chronic weight management
FDA approves semaglutide 2.4 mg (Wegovy) for obesity. STEP-1 trial: 14.9% mean body weight loss at 68 weeks. Demand outstrips supply within months — the modern GLP-1 cultural moment begins.
Tirzepatide era
- 2022May 2022Tirzepatide era
Mounjaro (tirzepatide) approved for T2D
First-in-class dual GIP/GLP-1 agonist launches for diabetes. SURPASS-2 head-to-head against semaglutide shows superior A1c and weight outcomes. The dual-agonist hypothesis pays off.
- 2022Late 2022Tirzepatide era
Compounded GLP-1 boom begins
FDA places semaglutide on the official drug shortage list. Under section 503A and 503B of the FDCA, compounding pharmacies and 503B outsourcing facilities can legally compound copies during a documented shortage. A new telehealth ecosystem builds around compounded semaglutide and tirzepatide.
- 2023November 2023Tirzepatide era
Zepbound approved for obesity
FDA approves tirzepatide 15 mg (Zepbound) for chronic weight management. SURMOUNT-1: 20.9% mean body weight loss at 72 weeks at the 15 mg dose. The first single-digit drug to cross the 20% weight-loss threshold.
- 2023August 2023Tirzepatide era
SELECT trial readout — semaglutide reduces cardiovascular events
The SELECT cardiovascular outcomes trial (~17,600 adults with established CV disease and BMI ≥27, no diabetes) shows semaglutide 2.4 mg cuts the rate of major adverse cardiovascular events by 20% vs. placebo. The first time a chronic weight loss drug shows cardiovascular benefit independent of glycemic effect.
Expansion era
- 2024March 2024Expansion era
Wegovy approved for cardiovascular risk reduction
Following SELECT, FDA expands Wegovy's label to include reduction of cardiovascular events in adults with CV disease and overweight/obesity. Medicare announces it will cover Wegovy under this indication — partial reversal of the historical bar on Medicare paying for obesity drugs.
- 2024June 2024Expansion era
First generic liraglutide (Teva)
FDA approves Teva's generic liraglutide. The first generic GLP-1 in the US opens the door to lower-cost daily-injection therapy as the older first-generation molecules go off-patent.
- 2024August 2024Expansion era
FDA removes tirzepatide from shortage list
FDA declares the tirzepatide shortage resolved. Compounding pharmacies are notified that they can no longer compound copies. Litigation from compounders follows; the legal landscape for compounded tirzepatide tightens through late 2024.
- 2024August 2024Expansion era
LillyDirect launches Zepbound vials
Eli Lilly opens self-pay vials of Zepbound at $399/month for 2.5 mg and $549/month for 5 mg through LillyDirect. The first major branded direct-to-consumer cash-pay GLP-1 program — designed in part to compete with the compounded market.
- 2024December 2024Expansion era
Zepbound approved for obstructive sleep apnea
Zepbound becomes the first drug ever approved for obstructive sleep apnea in adults with obesity. The SURMOUNT-OSA trials show ~50% reduction in apnea-hypopnea index. Medicare expands coverage under the OSA indication.
- 2025February 2025Expansion era
FDA removes semaglutide from shortage list
Supply of branded semaglutide stabilizes; the FDA declares the shortage resolved. The compounded semaglutide market constricts, with most compounders winding down by mid-2025.
Next-generation
- 2025June 2025Next-generation
Mazdutide approved in China
Innovent's GLP-1/glucagon dual agonist mazdutide receives Chinese NMPA approval — the first dual agonist developed in China to reach market.
- 2026Early 2026Next-generation
Retatrutide TRIUMPH Phase 3 readouts begin
First topline data from the TRIUMPH-1 obesity Phase 3 trial expected. Phase 2 data showed ~24% body weight loss at 48 weeks — if Phase 3 confirms, retatrutide would set a new ceiling on incretin-class efficacy.
- 2026April 2026Next-generation
Foundayo (orforglipron) — first small-molecule oral GLP-1 approved
FDA approves Eli Lilly's Foundayo (orforglipron) for chronic weight management. The first non-peptide oral GLP-1 receptor agonist — taken once daily, any time, with or without food. ATTAIN-1 showed ~12.4% body weight loss at 72 weeks. Approved 50 days after filing under the FDA's Commissioner's National Priority Voucher pilot — the fastest new molecular entity approval since 2002. Self-pay launch via LillyDirect from $149/month.