Tirzepatide

First-in-class dual GIP/GLP-1 receptor agonist (Mounjaro®/Zepbound®) achieving up to 22.5% weight loss — the highest of any approved pharmacotherapy.

Overview

Also Known As

Mounjaro, Zepbound, LY3298176

Mechanism of Action

Dual GIP/GLP-1 receptor agonist (twincretin). Full agonist at GIP receptor, partial agonist at GLP-1 receptor. C-20 fatty diacid enables albumin binding. Synergistic effects on glucose control, appetite, energy expenditure, and adipose tissue.

Product

Dosing & Administration

Typical protocols and routes

Half-Life

Approximately 5 days (120 hours)

Administration Routes

subcutaneous

Dosing Protocols

Reconstitute vial with 3 mL bacteriostatic water. Start at 0.5 mg (a very small amount on insulin syringe marked 0-100) once per week. Titrate upward based on how you feel — appetite, energy, nausea. May increase to 1-2 mg weekly over time. Taken once per week only.

Research

Key findings and status

Key Research Findings

SURPASS-2: superior to semaglutide 1 mg for HbA1c and weight in T2D. SURMOUNT-1: 22.5% weight loss at 15 mg over 72 weeks (highest pharmacotherapy result to date). SURMOUNT-2: confirmed efficacy in obese T2D patients.

Detailed Information

Tirzepatide is the first dual GIP/GLP-1 receptor agonist, developed by Eli Lilly. It is FDA-approved as Mounjaro® for type 2 diabetes and as Zepbound® for chronic weight management. Tirzepatide represents a new class of “twincretin” peptides that simultaneously activate both incretin receptor pathways.

Mechanism of Action

Tirzepatide is a 39-amino acid synthetic peptide based on the GIP (glucose-dependent insulinotropic polypeptide) sequence, engineered with modifications to also activate the GLP-1 receptor. It acts as a full agonist at the GIP receptor and a partial agonist at the GLP-1 receptor. This dual mechanism produces additive or synergistic effects on glucose homeostasis, appetite suppression, and energy expenditure.

The GIP receptor activation adds unique benefits including direct effects on adipose tissue (promoting lipid storage efficiency and healthy fat distribution), potential enhancement of bone mineral density, and possibly improved tolerability compared to pure GLP-1 agonists. A C-20 fatty diacid moiety enables albumin binding for a once-weekly half-life.

Clinical Evidence

The SURPASS trial program established tirzepatide efficacy in type 2 diabetes. SURPASS-2 demonstrated superior HbA1c reduction (-2.5% vs -1.9%) and weight loss (-12.4 kg vs -6.2 kg) compared to semaglutide 1 mg at the highest dose (15 mg). The SURMOUNT program established weight management efficacy, with SURMOUNT-1 showing unprecedented mean weight loss of 22.5% over 72 weeks at the 15 mg dose.

These weight loss results are the highest achieved with any pharmacotherapy to date, approaching levels previously only achievable through bariatric surgery. SURMOUNT-2 confirmed efficacy specifically in overweight/obese patients with type 2 diabetes.

Safety & Legal

Side Effects & Warnings

Nausea, diarrhea, constipation, vomiting, decreased appetite, dyspepsia. Generally similar to GLP-1 agonists. Rare: pancreatitis, gallbladder events. Boxed warning: thyroid C-cell tumors in animal studies.

Legal Status

FDA-approved as Mounjaro/Zepbound. Also available as compounded research peptide.

Molecular Data

Chemical properties

Molecular Weight

4813.45 g/mol

Amino Acid Sequence

39-amino acid GIP-based sequence with GLP-1 receptor activity modifications and C-20 fatty diacid at Lys20