Tirzepatide: Product Overview
Tirzepatide (LY3298176) is a once-weekly injectable peptide from Eli Lilly that activates both the GIP and GLP-1 receptors. It was the first dual incretin agonist approved for clinical use. It’s sold as Mounjaro for type 2 diabetes and as Zepbound for weight management and obstructive sleep apnea.
Product profile
| Attribute | Detail |
|---|---|
| Generic name | Tirzepatide |
| Development code | LY3298176 |
| Brand names | Mounjaro (type 2 diabetes), Zepbound (weight management and obstructive sleep apnea) |
| Manufacturer | Eli Lilly and Company |
| Drug class | Dual GIP and GLP-1 receptor agonist (“twincretin”) |
| Molecule | 39-amino-acid synthetic peptide built on the GIP sequence, with a C20 fatty diacid chain that binds albumin |
| Half-life | About 5 days, which supports once-weekly dosing |
| Route | Subcutaneous injection |
| Dosing frequency | Once weekly |
| Strengths | 2.5, 5, 7.5, 10, 12.5 and 15 mg |
| First approval | 2022 (Mounjaro, type 2 diabetes) |
Mechanism of action
Tirzepatide is one molecule that activates two incretin receptors, GIP and GLP-1. Both hormones are released by the gut after a meal, and both receptors are found in brain areas that regulate appetite.
GLP-1 receptor. Reduces appetite, slows gastric emptying and supports glucose-dependent insulin release.
GIP receptor. Supports glucose-dependent insulin release and influences how fat tissue stores and handles energy.
An imbalanced agonist. Tirzepatide was engineered by adding GLP-1 activity to the GIP sequence, and it doesn’t hit both receptors equally. Lilly’s pharmacology research found it binds the GIP receptor with the same affinity as native GIP, but binds the GLP-1 receptor with about 5-fold weaker affinity and shows about 20-fold lower potency there. At clinical doses it engages the GIP receptor more than the GLP-1 receptor. Researchers think this balance helps, because GLP-1 doses are often limited by nausea and vomiting while GIP engagement isn’t.
Biased signaling at GLP-1. At the GLP-1 receptor, tirzepatide favors the cAMP signaling pathway over beta-arrestin recruitment. That means less receptor internalization than native GLP-1 causes. In islet cell studies this was linked to a stronger insulin response.
Long action. The C20 fatty diacid chain binds albumin in the blood, which slows clearance and gives a half-life of about 5 days.
Approved uses and dosing
| Brand | Approved use (US) |
|---|---|
| Mounjaro | Blood sugar control in type 2 diabetes, alongside diet and exercise |
| Mounjaro | Lowering the risk of major cardiovascular events in adults with type 2 diabetes at high risk, added August 2026 |
| Zepbound | Weight reduction and long-term maintenance in adults with obesity, or overweight with at least one weight-related condition |
| Zepbound | Moderate to severe obstructive sleep apnea in adults with obesity, added December 2024 |
The Zepbound prescribing information sets out the dose schedule:
- Start at 2.5 mg once weekly for 4 weeks. This dose is for starting treatment only, not for maintenance.
- Increase in 2.5 mg steps, waiting at least 4 weeks at each dose.
- Maintenance for weight management is 5, 10 or 15 mg once weekly. For obstructive sleep apnea it’s 10 or 15 mg.
- The maximum dose is 15 mg once weekly.
The slow step-up is there to reduce gastrointestinal side effects. A missed dose can be taken within 4 days. After that, it’s skipped and the regular day resumes. Tirzepatide shouldn’t be combined with other tirzepatide products or with GLP-1 receptor agonists.
Type 2 diabetes evidence: the SURPASS program
The SURPASS program enrolled more than 13,000 people with type 2 diabetes across 10 trials. Tirzepatide lowered A1C and body weight in a dose-dependent way, both alone and on top of other diabetes medicines.
| Trial | Comparator | Duration | A1C change, tirzepatide 5 / 10 / 15 mg | A1C change, comparator | Reached A1C below 5.7% at 15 mg |
|---|---|---|---|---|---|
| SURPASS-2 | Semaglutide 1 mg | 40 weeks | -2.01 / -2.24 / -2.30 points | -1.86 points | 46% (semaglutide 19%) |
| SURPASS-3 | Insulin degludec | 52 weeks | -1.90 / -2.20 / -2.37 points | -1.34 points | 48% |
In SURPASS-1, where tirzepatide was the only diabetes medicine, 52% of people on 15 mg reached an A1C below 5.7%, compared with 1% on placebo.
In SURPASS-2, all three tirzepatide doses beat semaglutide 1 mg on both A1C and weight. Weight change was -7.6, -9.3 and -11.2 kg on tirzepatide against -5.7 kg on semaglutide. An A1C below 5.7% is the range seen in people without diabetes. SURPASS-4 compared tirzepatide with insulin glargine in people at high cardiovascular risk.
Weight management evidence: the SURMOUNT program
Across the SURMOUNT trials, tirzepatide produced dose-dependent weight loss in people with and without diabetes. Figures below use the treatment-regimen estimand, which counts everyone who started treatment, unless noted.
| Trial | Population | Participants | Duration | Tirzepatide | Comparator |
|---|---|---|---|---|---|
| SURMOUNT-1 | Obesity or overweight, no diabetes | 2,539 | 72 weeks | -15.0% / -19.5% / -20.9% at 5 / 10 / 15 mg | Placebo -3.1% |
| SURMOUNT-2 | Obesity or overweight with type 2 diabetes | 938 | 72 weeks | -12.8% / -14.7% at 10 / 15 mg | Placebo -3.2% |
| SURMOUNT-3 | After a 12-week intensive lifestyle program | 579 randomized | 72 weeks | A further -18.4% | Placebo +2.5% |
| SURMOUNT-4 | After 36 weeks on open-label tirzepatide | 670 randomized | 52 weeks | A further -5.5% | Switched to placebo +14.0% |
| SURMOUNT-5 | Obesity or overweight, no diabetes | 751 | 72 weeks | -20.2% | Semaglutide 2.4 mg -13.7% |
Lifestyle and continued treatment. SURMOUNT-3 participants lost 6.9% during the lifestyle phase, then 26.6% in total from study entry with tirzepatide (efficacy estimand). SURMOUNT-4 participants lost 21.1% in the open-label phase. Those who stayed on tirzepatide reached 26.0% total loss at 88 weeks, while those switched to placebo regained much of it. Those results support treating obesity as a long-term condition.
Head-to-head with semaglutide. SURMOUNT-5 is the first published head-to-head obesity trial against semaglutide. Each drug was taken at its maximum tolerated dose. Tirzepatide produced 47% greater relative weight loss, and 31.6% of tirzepatide participants lost at least 25% of their body weight against 16.1% on semaglutide.
Prediabetes. In the SURMOUNT-1 three-year study, 1,032 participants with prediabetes stayed on treatment for 176 weeks. Tirzepatide cut the risk of progressing to type 2 diabetes by 94% versus placebo (efficacy estimand), and the 15 mg group averaged 22.9% weight loss.
Heart, sleep apnea, liver and kidney outcomes
| Trial | Population | Participants | Primary result |
|---|---|---|---|
| SURPASS-CVOT | Type 2 diabetes with atherosclerotic cardiovascular disease, vs dulaglutide 1.5 mg | 13,299 | Major cardiovascular events 12.2% vs 13.1% (HR 0.92, 95.3% CI 0.83 to 1.01). Noninferior, superiority not shown. |
| SUMMIT | Heart failure with preserved ejection fraction and obesity, vs placebo | 731 | Cardiovascular death or worsening heart failure 9.9% vs 15.3% (HR 0.62, 95% CI 0.41 to 0.95) |
| SURMOUNT-OSA | Moderate to severe obstructive sleep apnea and obesity, vs placebo | 469 | Apnea-hypopnea index -25.3 vs -5.3 events per hour without PAP therapy, and -29.3 vs -5.5 with PAP |
| SYNERGY-NASH (Phase 2) | Biopsy-confirmed MASH with moderate or severe fibrosis, vs placebo | 190 | MASH resolution without worsening fibrosis in 44% / 56% / 62% at 5 / 10 / 15 mg vs 10% |
SURPASS-CVOT. This was the first cardiovascular outcomes trial in this class to use an active comparator, with a median follow-up of about 4 years. All-cause death was 16% lower with tirzepatide (HR 0.84), and in participants at high kidney risk, eGFR decline was slower by 3.54 mL/min/1.73 m² at 36 months. Those secondary results weren’t controlled for multiple testing. The trial supported the August 2026 cardiovascular indication for Mounjaro.
SUMMIT. The benefit came mainly from fewer worsening heart failure events. Cardiovascular death on its own didn’t differ significantly. Health status scores (KCCQ-CSS) rose 19.5 points with tirzepatide against 12.7 with placebo at 52 weeks.
SURMOUNT-OSA. The AHI fell by up to 58.7% from baseline. After one year, 42% of participants on tirzepatide alone and 50% on tirzepatide with PAP reached remission or mild, non-symptomatic sleep apnea, against 16% and 14% on placebo.
SYNERGY-NASH. Fibrosis improved by at least one stage without worsening MASH in 51% to 55% of tirzepatide participants against 30% on placebo. This was a 52-week Phase 2 trial, so longer trials are still needed.
Safety and tolerability
The most common side effects are gastrointestinal. They rise with dose, are mostly mild to moderate, and happen mainly while the dose is being increased.
Most common adverse events in SURMOUNT-1
| Adverse event | 5 mg | 10 mg | 15 mg | Placebo |
|---|---|---|---|---|
| Nausea | 24.6% | 33.3% | 31.0% | 9.5% |
| Diarrhea | 18.7% | 21.2% | 23.0% | 7.3% |
| Constipation | 16.8% | 17.1% | 11.7% | 5.8% |
| Vomiting | 8.3% | 10.7% | 12.2% | 1.7% |
| Stopped treatment due to adverse events | 4.3% | 7.1% | 6.2% | 2.6% |
These rates come from Lilly’s SURMOUNT-1 results. Serious adverse events were similar across groups, at 5.1% to 6.9% on tirzepatide and 6.8% on placebo.
Compared with semaglutide. In SURMOUNT-5, stopping treatment because of gastrointestinal side effects happened in 2.7% of tirzepatide participants against 5.6% on semaglutide. Injection site reactions were more common with tirzepatide.
Low blood sugar. On its own, tirzepatide carries a low risk of hypoglycemia. The risk rises when it’s used with insulin or sulfonylureas, and the prescribing information advises considering a lower dose of those medicines when tirzepatide is started.
Interactions with other medicines. Because tirzepatide slows gastric emptying, it can change how well oral medicines taken at the same time are absorbed.
Label warnings. The Zepbound label carries a boxed warning: tirzepatide caused thyroid C-cell tumors in rats, and it’s unknown whether it does so in humans. It isn’t used in people with a personal or family history of medullary thyroid carcinoma or with MEN 2. Other listed warnings include pancreatitis, gallbladder problems and pulmonary aspiration during anesthesia or deep sedation.
This article is for educational purposes only and does not replace medical advice. Speak with your licensed physician about diabetes and weight management options that are available to you in the Philippines and suited to your health history.
