Tirzepatide, Semaglutide and Retatrutide Compared: Single, Dual and Triple Incretin Agonism in Laboratory Research

Incretin receptor pharmacology is one of the most frequently requested research areas in UK laboratories, and it is also one of the easiest to describe imprecisely. Semaglutide, tirzepatide and retatrutide are often grouped together as “GLP-1 compounds”, yet they act on different numbers of receptor targets. That difference shapes assay design, reporting language and what a procurement team should expect to see in a material’s documentation.

This article compares the three in research terms only. It describes receptor targets and agonism class, and it separates what published research reports about a compound from the status of any actual ADINA material. Nothing here is a human-use claim, a dosing guide or a therapeutic recommendation.

What “incretin agonism” means in research terms

Incretin research centres on three Class B G-protein-coupled receptors: the GLP-1 receptor, the glucose-dependent insulinotropic polypeptide (GIP) receptor, and the glucagon receptor. A compound is described by how many of these receptors it engages and with what balance of activity.

Single-pathway agonism engages one receptor. Dual agonism engages two. Triple agonism engages three. In the literature these are usually reported alongside potency ratios, which describe relative activity across the targets rather than a simple on/off switch. Two compounds can both be labelled “dual agonists” and still behave differently in a specific assay depending on receptor affinity and signalling bias.

Semaglutide: the single-pathway comparator

Semaglutide is a GLP-1 receptor agonist. It is built around a GLP-1 backbone with modifications that extend its circulating stability, and in the literature it is characterised as engaging the GLP-1 receptor rather than the GIP or glucagon receptors. That single-target profile makes it a common reference point: when a study needs a selective GLP-1 comparator, semaglutide is the material the wider field usually reaches for.

Because it isolates one pathway, it is often used as the baseline against which dual and triple agonists are contrasted. That does not make it a lesser material; it makes it a defined one, and defined behaviour is what a comparative assay needs. The ADINA catalogue entry for semaglutide sets out the specification and documentation available for the material we hold.

Tirzepatide: dual GIP and GLP-1 agonism

Tirzepatide is a dual agonist, engaging both the GIP receptor and the GLP-1 receptor. It is not a GLP-1-only compound and it is not a triple agonist, and conflating it with either is one of the most common errors in informal descriptions of the field. Its published clinical research programme explored the combination of the two incretin pathways rather than a single one.

For laboratory work, the practical point is that a dual agonist engages two receptor systems. An assay intended to isolate GLP-1 signalling will not capture the GIP component, so method design has to account for both targets explicitly. Researchers comparing tirzepatide with semaglutide are, in effect, comparing two-pathway engagement against one-pathway engagement.

ADINA’s tirzepatide entry documents the material as a dual incretin agonist, distinct from its single-target and triple-target comparators.

Retatrutide: triple GIP, GLP-1 and glucagon agonism

Retatrutide is described in the literature as a triple agonist, engaging the GIP, GLP-1 and glucagon receptors. Its published phase 2 programme is the clearest source setting out the three-target design, and it is frequently cited when researchers want to compare triple agonism against dual and single agonism.

The addition of the glucagon receptor is what separates it from tirzepatide, and the addition of both GIP and glucagon is what separates it from semaglutide. Retatrutide is not part of the ADINA catalogue at the time of writing, so it appears here as a research comparator rather than as a stocked material. Where a study requires it, we would rather say clearly that we do not hold it than imply otherwise.

Side-by-side comparison

The table is deliberately narrow. It states receptor targets and class only, because those are the facts a method design or a procurement specification can be built on. Potency figures, half-lives and comparative effect sizes belong in the specific published studies that report them, and should be read there rather than summarised second-hand.

What the distinction means for method design

Receptor count changes what an assay can detect.

A cAMP reporter assay targeted at the GLP-1 receptor will report on one pathway. If the material in the well also engages the GIP or glucagon receptor, that activity is invisible to the reporter but still present in the system. Studies comparing across the three compounds therefore usually need either a panel of receptor-specific assays or a binding study that establishes affinity per target.

Reporting language matters too. Describing tirzepatide as a “GLP-1 agonist” understates its targets, and describing semaglutide as a “dual agonist” overstates them. Precise class language is not pedantry; it is what allows two laboratories to compare results without hidden differences in what each assay was measuring.

Documentation and traceability for UK procurement

For UK research and procurement teams, the compound’s pharmacology is only half the decision. The other half is the material in front of you: its identity, its specification, and the documentation that travels with the batch.

At ADINA we distinguish three things clearly. First, what published research reports about a compound. Second, the specification of the material we hold. Third, the status of supporting documents such as certificates of analysis and batch records. Where a document is not yet available, we describe it as pending rather than implying it exists. We do not publish purity percentages, testing results or delivery promises we cannot substantiate, and any figure quoted on this site will be traceable to a document we can supply.

This matters for comparison work specifically. When a study contrasts three materials, the result is only as sound as the identity and consistency of each batch. Batch traceability and documentation status should be confirmed before a comparison begins, not after.

Sources and evidence boundaries

The receptor-target and agonism-class descriptions above reflect the established pharmacology literature and the published clinical research programmes for each compound, including the phase 2 programme for retatrutide. We have deliberately not reproduced specific potency values, trial effect sizes or half-life figures, because those are best read in the primary publications that report them with their own methods and limitations.

A general caution applies across this field. A receptor target is a mechanism, not an outcome. Research on a compound tells you what the literature has examined; it does not tell you what a given batch of material will do in your system, and it says nothing about the status of the ADINA material beyond the specification and documentation we publish.

Choosing between the three

If your work needs a selective single-pathway comparator, semaglutide is the natural starting point. If it examines two-pathway incretin engagement, tirzepatide fits the design. If it requires full three-pathway agonism, retatrutide is the research comparator, and we would point you to the primary literature rather than to a catalogue entry we do not hold.

Whichever you choose, the questions to settle first are the same: which receptors your assay actually measures, what class language your report will use, and whether the batch documentation you need is available or pending.

Materials described here are supplied for laboratory research use only, and are not for human or veterinary use. Researchers should confirm that any use complies with their institution’s requirements and applicable UK regulations.