Milestones
- FDA approves Mounjaro for type 2 diabetes13 May 2022Complete.
- Key obesity trial in NEJM (20.9% weight loss)Jul 2022Complete.
- FDA approves Zepbound for weight loss8 Nov 2023Complete.
- FDA approves Zepbound for sleep apnea20 Dec 2024Complete.
- Beats Wegovy head-to-headMay 2025Complete.
- Heart-outcome results and new usesNowCurrent milestone.
Most important updates
- 28 Aug 2026
- 20 Aug 2024
- 8 Nov 2023
- 13 May 2022
- 17 Feb 2021
Current obstacles
- Supply and price pressureDemand outran supply for years, and governments and insurers are pushing prices down.
- Stomach side effectsNausea, vomiting and diarrhea are common as the dose goes up, and make people quit.
Physics limits
- The body defends its weightAs weight falls, hunger hormones rise and energy use drops, so loss plateaus after about a year. When treatment stops, most people regain much of it: in one trial, about two-thirds within a year.
- Part of the weight lost is muscleRoughly a quarter to a third of the weight lost on these drugs is lean mass, not fat. In older people that loss of muscle and bone can matter more than the weight itself.
- Stomach side effects cap the doseThe same gut and brain signals that curb appetite cause nausea and vomiting. Doses must be raised slowly over months, and some people can't tolerate the highest, most effective ones.
How it works
Molecule
A long-lasting hormone copy
A small protein based on a gut hormone, with a fatty tail that sticks to blood proteins so it lasts about five days.
Receptors
Two hormone signals
It triggers GLP-1 signals (fullness, slower stomach, insulin) and GIP signals (insulin, fat tissue).
Effect
Eating less
Most weight loss comes from feeling less hungry and eating less, plus better blood sugar.
Spec sheet
| Spec | Tirzepatide (Mounjaro / Zepbound) |
|---|---|
| Mechanism | GIP + GLP-1 receptor agonistR (reported) |
| Dosing | Once weekly, 2.5-15 mg SCR (reported) |
| Half-life | ~5 daysR (reported) |
| Weight loss, SURMOUNT-1 (15 mg) | 20.9% at 72 weeksR (reported) |
| SURMOUNT-5 vs semaglutide | 20.2% vs 13.7%R (reported) |
R reported by the company
Papers & demos
- May 2025paperTirzepatide as compared with semaglutide for the treatment of obesity, SURMOUNT-5 (NEJM) (opens doi.org)Head-to-head: 20.2% vs 13.7% weight loss at 72 weeks.
- Jul 2022paperTirzepatide once weekly for the treatment of obesity, SURMOUNT-1 (NEJM) (opens doi.org)Showed 20.9% average weight loss at 72 weeks, changing what people thought drugs could do.
Update log
Fri 28 Aug
- Major: PressRegulatory
Tue 20 Aug 2024
- Minor: PressResearch
Thu 1 Aug 2024
- Minor: PressTest
Wed 8 Nov 2023
- Major: RegulatorRegulatory
Fri 13 May 2022
- Major: PressRegulatory
Wed 17 Feb 2021
- Major: PressTest
About Eli Lilly
Eli Lilly
Zepbound, obesity pill, retatrutide
US drugmaker that leads in obesity and diabetes drugs. Tirzepatide (Mounjaro, Zepbound) is among the world's best-selling drugs, its GLP-1 pill was approved in 2026, and retatrutide gave about 28% weight loss in Phase 3. It bought Verve (gene editing) in 2025.
- Became the first drugmaker worth about $1 trillion (Nov 2025), thanks to tirzepatide.
- Foundayo (orforglipron), a daily GLP-1 pill with no food or water rules, was FDA-approved for obesity on 1 Apr 2026.
- Retatrutide gave 28.3% average weight loss at 80 weeks on the top dose in Phase 3 (May 2026).
- Founded
- 1876150 yrs
- Headquarters
- United States
- Status
- Public
- Listed
- LLY (opens google.com)NYSE
- Valuation
- $1.1Tmarket capSep 2026
- Works in
- BiotechObesity & metabolism
- Coverage
- 4 programs · 18 updateslatest 25d agochecked 25 Sep
- People
- David A. Ricks (opens en.wikipedia.org)Chair and CEODaniel SkovronskyChief Scientific Officer