What is Tirz?

Tirz (developmental code LY3298176) is a long-acting synthetic peptide developed as a research tool for probing simultaneous signalling through two incretin receptors — the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. It is described in the academic literature as the first characterised dual GIP/GLP-1 receptor agonist to reach large-scale clinical evaluation, and has become a reference compound for laboratory groups studying combined incretin biology, insulin secretion and body-weight regulation.

BuyRetaUK supplies Tirz as a sterile lyophilised powder at ≥99% HPLC purity, with a batch-specific Certificate of Analysis, packed for research handling in temperature-controlled UK storage. It is strictly for in-vitro laboratory use and is not approved by BuyRetaUK for human or veterinary administration.

Tirz was disclosed by Eli Lilly and Company as LY3298176 and characterised across a body of peer-reviewed pharmacology work from 2018 onward. The peptide was engineered by grafting GIP receptor activity onto a GLP-1 backbone, producing a single molecule with balanced dual agonism and a half-life suited to weekly dosing regimens in the studies that reference it.

The compound is now supported by the Eli Lilly SURPASS clinical trial programme (type-2 diabetes research) and the SURMOUNT programme (body-weight research). For laboratory buyers, Tirz's status as the archetypal dual incretin agonist makes it the standard comparator when characterising newer molecules such as the triple agonist RT3.

LY3298176 is the Eli Lilly internal development code for Tirz. The two names refer to the same 39-amino-acid synthetic peptide bearing a C20 fatty diacid moiety, which extends plasma half-life via albumin binding in the studies that report its pharmacokinetics. Laboratory suppliers frequently list the compound under both names, and analytical certificates typically reference LY3298176 in the identity block alongside the Tirz INN.

When cross-referencing publications, LY3298176 is the term most likely to appear in preclinical and mechanism-of-action papers, while Tirz is more common in clinical and metabolic literature.

A dual agonist is a single peptide that simultaneously activates two receptors. For Tirz, those receptors are the GIP receptor and the GLP-1 receptor — the two incretin axes responsible for the majority of nutrient-driven insulin secretion. This contrasts with single agonists (such as Sema, GLP-1 only) and triple agonists (such as RT3, which adds the glucagon receptor).

In receptor pharmacology assays Tirz is characterised as a balanced dual agonist with a bias toward the GIP receptor relative to native GIP, and full efficacy at the GLP-1 receptor. This receptor profile is the primary mechanistic feature that distinguishes Tirz from every single or triple agonist currently in wide research use.

GLP-1 (glucagon-like peptide-1) is an incretin hormone released from intestinal L-cells in response to nutrient intake. Its receptor, the GLP-1R, is expressed on pancreatic beta cells, alpha cells, cardiac tissue and central nervous system nuclei relevant to appetite. Tirz's GLP-1 activity mirrors the mechanism of established single-agonist compounds such as Sema, and provides the well-characterised incretin arm of its action.

GIP (glucose-dependent insulinotropic polypeptide) is the second incretin, released from duodenal K-cells. The GIP receptor is expressed on beta cells, adipocytes and central nuclei. Adding GIP receptor activity to a GLP-1 backbone is the defining innovation of Tirz — it is this dual engagement that laboratory groups reference when comparing Tirz against single GLP-1 agonists in metabolic models.

Both peptides are long-acting incretin-class research compounds, but their receptor profiles differ. Tirz is a dual agonist (GIP + GLP-1). RT3 is a triple agonist that adds glucagon receptor activity to the same two incretin arms. For laboratories building comparative datasets, Tirz typically appears as the dual-agonist reference alongside RT3 (triple) and Sema (single GLP-1).

Our dedicated comparison guide at /rt3-vs-tirz covers the full side-by-side receptor and class analysis.

Published research references Tirz across metabolic, glycaemic and body-composition models — investigating the joint effect of GIP and GLP-1 receptor activity on insulin secretion, food intake, adipose remodelling and energy balance. Because it acts as a balanced dual agonist, Tirz is a natural benchmark in studies that partition the receptor-level contribution of the GIP axis to overall incretin response.

A full research-workflow summary lives at /rt3-research and applies equally to tirz-based experimental designs.

Every BuyRetaUK batch is produced to research-grade specifications, quarantined until analytical release, then dispatched from temperature-controlled UK storage with a batch-specific Certificate of Analysis. Full batch traceability — sequence identity, purity, appearance and cold-chain history — is maintained for every lot.

For a full account of our quality workflow see the Laboratory Quality Standards guide at /laboratory-quality.

BuyRetaUK Tirz is released at ≥99% HPLC purity with mass spectrometry identity confirmation. Vials are lyophilised under sterile conditions, sealed under inert gas and quarantined at 2–8°C pending analytical sign-off. Shipping is temperature-controlled and every order arrives with the batch-specific COA that matches the lot printed on the vial.

Each Tirz lot ships with a batch-specific Certificate of Analysis covering identity (mass spectrometry), purity (reverse-phase HPLC with UV detection at ≥99%), appearance and endotoxin (LAL assay). The lot number on the COA matches the lot printed on the vial, so any batch can be independently cross-referenced.

For the full anatomy of a peptide COA — how the HPLC, mass spectrometry and endotoxin sections are structured — see /knowledge-hub/certificate-of-analysis-guide.

Lyophilised Tirz vials are stored at 2–8°C protected from light. For long-term storage below -20°C is acceptable; repeated freeze-thaw of the lyophilised powder is not recommended. Once reconstituted with bacteriostatic water the peptide is stored refrigerated (2–8°C) and used within approximately 30 days.

Volume-per-dose calculations for laboratory dilution are handled by our /reconstitution-calculator.