GLP-1-Based Peptides Compared: Retatrutide, Cagrilintide, and AOD9604

GLP-1 receptor agonists have become central to metabolic research. What began with mono-agonists such as semaglutide later expanded to dual agonists such as tirzepatide and, more recently, to triple agonists such as Retatrutide.

This comparison groups the key peptides in the PeptidesDirect portfolio by receptor profile, research status, and typical use case. It also includes adjacent compounds such as cagrilintide and AOD9604, even though they are not GLP-1 agonists themselves.

How the Generations Differ

One practical way to group these agents is by the number and type of receptors they target.

First generation (mono-agonists) such as semaglutide (Ozempic/Wegovy) act through the GLP-1 receptor alone. GLP-1 is an incretin hormone released after meals. It supports glucose-dependent insulin secretion, slows gastric emptying, and reduces appetite through central signaling pathways.

Second generation (dual agonists) such as tirzepatide (Mounjaro/Zepbound) activate two receptors at once. Tirzepatide combines GLP-1 and GIP signaling.

Third generation (triple agonists) is currently represented in late-stage development by Retatrutide. It activates GLP-1, GIP, and glucagon receptors within one molecule.

Cagrilintide (an amylin analogue) and AOD9604 (a GH fragment) sit outside that incretin sequence, but they are relevant comparators because they address weight and metabolic research through different pathways.

Approved GLP-1 Medications for Reference

Before turning to investigational peptides, it helps to look at the approved agents that serve as clinical reference points.

Semaglutide (Ozempic/Wegovy)

Semaglutide is the active ingredient behind Ozempic and Wegovy (Novo Nordisk). Structurally, it has 94% homology to native GLP-1 but includes a C18 fatty acid side chain that promotes albumin binding and extends the half-life to about one week. Additional modifications improve resistance to DPP-4 degradation.

Semaglutide remains a useful benchmark for later incretin-based agents because it isolates GLP-1 receptor signaling and already has cardiovascular outcomes data from a dedicated event-driven trial.

Tirzepatide (Mounjaro/Zepbound)

Tirzepatide (Eli Lilly) was the first approved dual incretin agonist. It activates both the GLP-1 and GIP receptors. Like semaglutide, it uses a fatty-acid modification to extend half-life for once-weekly dosing.

The role of GIP is still discussed with some nuance. Beyond insulin secretion, GIP appears to influence adipose tissue biology and other metabolic pathways that differ from GLP-1 alone.

Compared with semaglutide, tirzepatide showed that adding a second receptor can improve weight-loss outcomes in separate trial programs, although the studies were not identical.

Retatrutide - Three Receptors, One Peptide

Retatrutide (LY-3437943, Eli Lilly) is a triple agonist that activates GLP-1, GIP, and glucagon receptors. The GLP-1 component contributes appetite reduction, insulin secretion, and delayed gastric emptying. GIP adds a second incretin pathway. The glucagon component is the main difference versus semaglutide and tirzepatide.

Why Glucagon Agonism Matters

Glucagon was long viewed mainly as a counter-regulatory hormone that raises blood glucose. In combination approaches, however, glucagon receptor agonism may also contribute distinct metabolic effects:

• Higher energy expenditure: glucagon signaling can increase thermogenesis and basal energy use.
• Liver fat effects: glucagon is linked to hepatic fat oxidation, which matters in MASLD-related research.
• Additional fat-metabolism signaling: glucagon targets a pathway that is different from GLP-1 or GIP alone.
• Balanced glycemic effects require context: GLP-1 and GIP may offset some glucose-raising effects of glucagon, but glycemic outcomes still depend on dose, population, and study design.

In that 48-week Phase 2 trial, retatrutide produced a larger mean weight reduction than the figures reported in STEP 1, SURMOUNT-1, or REDEFINE-1, but cross-trial comparisons still need caution because semaglutide, tirzepatide, CagriSema, and retatrutide were studied over different durations and with different estimands.

For research, retatrutide is particularly relevant when the question involves triple agonism, glucagon receptor biology, liver fat reduction, or combined effects on appetite and energy expenditure.

Retatrutidemetabolic

First-ever triple-action weight management peptide targeting three receptors at once: GIP, GLP-1, and glucagon. Shown exceptional results in Phase 2 trials - up to 24% weight reduction. The most advanced metabolic peptide available.

More details: Retatrutide Guide

Cagrilintide - The Amylin Pathway

Cagrilintide (Novo Nordisk) does not belong to the GLP-1 agonist sequence. It is a long-acting amylin analogue. Amylin is co-secreted with insulin from pancreatic beta cells and acts as a separate satiety signal. It can reduce food intake, slow gastric emptying, and suppress postprandial glucagon release.

Cagrilintide is relevant for research on amylin signaling, satiety pathways, and combination strategies that extend beyond GLP-1 receptor agonism alone.

AOD9604 - The GH Fragment

AOD9604 is the outlier in this group. It is not a GLP-1 agonist but a modified fragment of human growth hormone (amino acids 176-191). In the mouse work often cited for AOD9604, the fragment was associated with lipolytic effects and changes in beta-3 adrenergic receptor expression, but the authors concluded those effects were not mediated directly through beta-3-AR.

Historically, AOD9604 was developed as an obesity candidate in the early 2000s but did not progress beyond Phase 2. For research, it remains relevant as a GH-fragment comparator with older weight-loss and fat-metabolism data, while its mechanism is less defined than that of incretin-based peptides.

AOD-9604metabolic

Modified hGH fragment (176-191) studied for fat metabolism and lipolysis research. Interacts with beta-3 adrenergic receptors without growth-promoting effects.

How the Peptides Differ in Efficacy

Weight-loss data are often presented side by side, but these results come from separate studies with different durations, populations, dose strategies, and estimands. That limits any direct ranking.

The broad pattern is that multi-receptor approaches have produced larger weight-loss signals than semaglutide alone. Still, the figures above should be read as separate trial outcomes rather than as a strict head-to-head hierarchy.

Which Peptide for Which Research?

Quality and Ordering

For product-specific information such as certificate of analysis availability, shipping options, payment methods, or reconstitution accessories, refer to the relevant product page because these operational details can change over time and are not part of the clinical evidence discussed in this article.

Further Reading

• Retatrutide Guide
• Retatrutide vs Tirzepatide vs Semaglutide
• Peptide Storage Guide
• What Are Research Peptides?