Tirzepatide

Key benefits

What to expect

Based on community reports and published research. Individual results vary significantly.

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Dosing protocols

Dosing information is sourced from published research and community protocols. This is not a recommendation. Consult a healthcare professional.

Overview

Tirzepatide (brand names Mounjaro for diabetes, Zepbound for weight management) is a first-in-class dual GIP/GLP-1 receptor agonist developed by Eli Lilly. Unlike semaglutide which only targets GLP-1 receptors, tirzepatide also activates GIP (glucose-dependent insulinotropic polypeptide) receptors, creating a synergistic effect on appetite, insulin sensitivity, and fat metabolism. The SURMOUNT-1 trial demonstrated average weight loss of 20.9% at the highest dose - the most ever achieved by a pharmaceutical agent in a clinical trial. It received FDA approval for type 2 diabetes in 2022 and for weight management in 2023.

How it works

Tirzepatide simultaneously activates both GIP and GLP-1 receptors. GLP-1 receptor activation reduces appetite, slows gastric emptying, and stimulates insulin secretion. GIP receptor activation enhances fat metabolism, improves insulin sensitivity, and may protect against the muscle wasting seen with GLP-1-only agonists. The dual mechanism produces greater weight loss than GLP-1 alone. The molecule is engineered with a C20 fatty acid moiety that binds to albumin, providing a half-life of approximately 5 days for once-weekly dosing.

Side effects

Research history

Tirzepatide vs semaglutide

In the SURMOUNT trials, tirzepatide at its highest dose (15 mg) produced average weight loss of 20.9% compared to semaglutide's 16.9% in the STEP trials. A head-to-head trial (SURMOUNT-5) is expected to provide direct comparison data. Beyond weight, tirzepatide appears to produce greater improvements in insulin sensitivity and may better preserve lean mass due to the GIP receptor component. The GI side effect profile is similar between the two, though some data suggests tirzepatide may cause slightly less nausea at equivalent efficacy levels.

Retatrutide: the triple agonist

Retatrutide is the next evolution - a triple GIP/GLP-1/glucagon receptor agonist in Phase 3 trials. Early data showed up to 24.2% weight loss at 48 weeks. The glucagon receptor component may further enhance fat metabolism and energy expenditure. If approved, it would represent the most potent pharmaceutical weight loss agent ever developed. Eli Lilly is running the Phase 3 program with results expected in 2025–2026.

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References

1. [1]Jastreboff AM, et al. "Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)." New England Journal of Medicine, 2022.
2. [2]Frias JP, et al. "Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes." New England Journal of Medicine, 2021.
3. [3]Rosenstock J, et al. "Retatrutide, a GIP, GLP-1, and glucagon receptor agonist." New England Journal of Medicine, 2023.

Frequently asked questions

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