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GIP/GLP-1 Dual Receptor Agonist

Tirzepatide

Also known as: GLP-2 TZ, Mounjaro, Zepbound

An FDA-approved dual GIP/GLP-1 receptor agonist with a larger reported weight-loss effect than semaglutide in head-to-head-adjacent trials. Sold by research-chemical vendors under coded names like 'GLP-2 TZ' — this profile is about the actual approved drug, tirzepatide.

Educational content, not advice. Compiled from information publicly available on the internet; it may contain inaccuracies and was not written or reviewed by medical professionals. Use it as a starting point for your own research, verify against primary sources, and see our full disclaimer.

A note on naming

Like semaglutide, tirzepatide is sold under coded vendor names ("GLP-2 TZ" despite having no relationship to GLP-2 biology — this appears to be a naming choice to obscure the actual drug identity rather than a meaningful classification). Tirzepatide is the active ingredient in two FDA-approved prescription drugs: Mounjaro (type 2 diabetes) and Zepbound (chronic weight management), each with a substantial Phase 3 clinical trial program behind them.

Overview

Tirzepatide is a dual agonist of both the GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 receptors — the first approved drug to combine both mechanisms in one molecule. It was approved for type 2 diabetes (Mounjaro, 2022) and later for chronic weight management (Zepbound, 2023).

Proposed Mechanism of Action

By agonizing both the GIP and GLP-1 receptors, tirzepatide combines GLP-1's appetite-suppressing and glycemic effects with GIP's additional role in insulin sensitivity and lipid metabolism — the dual mechanism is the proposed explanation for its larger effect size relative to GLP-1-only agonists like semaglutide in cross-trial comparisons (formal head-to-head trials also exist; see the SURMOUNT-5 literature referenced in our source search if you want that specific comparison).

Research Context

The cited SURMOUNT-1 trial randomized 2,539 adults with obesity to 5 mg, 10 mg, or 15 mg once-weekly tirzepatide or placebo for 72 weeks (following a 20-week dose-escalation phase). The 15 mg group averaged approximately 20.9% weight reduction, with roughly nine in ten participants on tirzepatide losing weight, versus 3.1% average change in the placebo group.

Regulatory Status

As with semaglutide, tirzepatide is FDA-approved only in its branded, prescription form (Mounjaro/Zepbound), dispensed through licensed pharmacies at controlled doses. Compounded and "research use only" versions carry the same purity/dosing-accuracy caveats the FDA has raised for the broader GLP-1/GIP compounding category.

Limitations of the Current Evidence

  • The cited trial is specific to the obesity indication; the diabetes indication rests on a separate trial program (SURPASS).
  • Cross-drug efficacy comparisons (tirzepatide vs. semaglutide) are best drawn from trials designed for direct comparison, not by informally comparing percentage changes across separately conducted trials with different populations.

Research-Setting Dosing (as reported in literature)

RouteRange (as reported)FrequencyNotes
Subcutaneous injection5–15 mgOnce weekly, following a 20-week dose-escalation phaseSURMOUNT-1 trial (Jastreboff et al., 2022), 72 weeks total. The 15 mg dose group averaged roughly 20.9% body weight reduction versus 3.1% for placebo at week 72.

Figures above are extracted directly from the cited preclinical/research literature. They describe what researchers administered to study subjects (frequently animal models) — they are not human dosing recommendations and are not medical advice.

Cited Studies

  • Tirzepatide Once Weekly for the Treatment of Obesity

    Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, Kiyosue A, Zhang S, Liu B, Bunck MC, Stefanski A (SURMOUNT-1 Investigators) · New England Journal of Medicine · 2022

    Human clinical trial (Phase 3, randomized, double-blind, placebo-controlled, 2,539 subjects)View source →

Last updated August 1, 2026