All peptides discussed on this page are sold by Webber Science for in vitro research purposes only. They are not intended for human or veterinary use. This content is provided for informational purposes and does not constitute medical advice.
Introduction
The global research interest in metabolic peptides has accelerated dramatically since the clinical success of GLP-1 receptor agonists. But the field extends well beyond a single drug class. Researchers investigating energy homeostasis, adipose tissue biology, and metabolic dysfunction now have access to a diverse toolkit of peptides targeting distinct signalling pathways — from dual and triple incretin receptor agonists to growth hormone fragments and novel mitochondrial uncouplers.
This guide provides Canadian researchers with a science-first overview of six key weight loss and metabolic peptides available for laboratory investigation: Tirzepatide, Retatrutide, AOD9604, Tesamorelin, SLU-PP-332, and HGH Fragment 176-191. For each compound, we review the mechanism of action, preclinical and clinical evidence, and relevance to specific research applications.
Tirzepatide
Mechanism of Action
Tirzepatide is a synthetic peptide that acts as a dual agonist of the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor. This dual-incretin mechanism differentiates it from earlier GLP-1-only agonists:
- GIP receptor activation — Stimulates insulin secretion, promotes adipose tissue lipid buffering, and may improve brown adipose tissue thermogenesis.
- GLP-1 receptor activation — Delays gastric emptying, suppresses glucagon secretion, and signals satiety via hypothalamic pathways.
- Combined effect — Dual activation produces synergistic reductions in food intake and body weight compared to GLP-1 mono-agonism in preclinical models.
Research Evidence
Tirzepatide has the most extensive clinical dataset of any peptide on this list. The SURPASS and SURMOUNT trial programmes demonstrated:
- SURMOUNT-1 (2022): In adults with obesity (without diabetes), tirzepatide produced up to 22.5% body weight reduction over 72 weeks.
- SURPASS-2: Superior HbA1c and weight reduction compared to semaglutide in type 2 diabetes.
- Ongoing trials are investigating cardiovascular outcomes (SURPASS-CVOT) and heart failure with preserved ejection fraction.
For researchers, tirzepatide serves as a critical benchmark compound in metabolic studies, providing a reference point for evaluating next-generation peptides.
🛒 Note: Tirzepatide product listings vary; check the Webber Science catalogue for current availability.
Retatrutide (LY3437943)
Mechanism of Action
Retatrutide is a triple agonist targeting three incretin-related receptors — earning it the designation “triple-G” peptide:
- GIP receptor — Enhances insulin secretion and lipid metabolism.
- GLP-1 receptor — Suppresses appetite and delays gastric emptying.
- Glucagon receptor — Increases energy expenditure via hepatic gluconeogenesis and lipolysis.
The addition of glucagon receptor agonism is the key differentiator from tirzepatide. Glucagon promotes thermogenesis and fatty acid oxidation, which may produce greater fat mass reduction than dual GIP/GLP-1 agonism alone.
Research Evidence
- Phase 2 trial (2023): In adults with obesity, retatrutide produced up to 24.2% body weight reduction at 48 weeks — the highest reported in any clinical trial of a metabolic peptide at that time.
- Metabolic endpoints: Significant improvements in HbA1c, blood pressure, and lipid profiles.
- Preclinical studies in diet-induced obese mice showed superior reductions in body fat compared to dual GIP/GLP-1 agonists.
Retatrutide represents the current leading edge of incretin-based metabolic research and is expected to enter Phase III trials.
📘 Deep dive: Retatrutide: The Triple-G Peptide | Retatrutide vs. Semaglutide vs. Tirzepatide: 2026 Buyer’s Guide
🛒 Source for your lab: Retatrutide (GLP-3 RET 5 mg) — Webber Science
AOD9604
Mechanism of Action
AOD9604 is a modified fragment of the C-terminus of human growth hormone (hGH), specifically amino acids 177–191, with a tyrosine addition at the N-terminus for stability. Its mechanism centres on lipolysis without the mitogenic effects of full-length hGH:
- Lipolytic activity — AOD9604 stimulates the release of free fatty acids from adipose tissue via β3-adrenergic pathway activation.
- Anti-lipogenic effect — Inhibits de novo lipogenesis in adipocytes.
- No IGF-1 upregulation — Unlike full-length hGH, AOD9604 does not significantly increase IGF-1 levels, reducing concerns about cell proliferation.
Research Evidence
- Phase IIb trial (2006): A randomized, double-blind study in obese humans found a statistically significant dose-dependent reduction in body weight over 12 weeks at the 1 mg dose. However, the effect size was modest (~1.5 kg greater than placebo), and development was discontinued for commercial reasons.
- Preclinical: Mouse models demonstrated enhanced lipolysis and reduced fat mass without affecting glucose metabolism.
- AOD9604 remains a useful research tool for studying hGH-independent lipolytic pathways.
Research Considerations
While the clinical programme was not commercially pursued, AOD9604’s mechanistic distinction from full-length hGH makes it valuable for researchers studying adipose tissue metabolism specifically, without confounding IGF-1-mediated effects.
🛒 Source for your lab: AOD9604 (5 mg) — Webber Science
Tesamorelin
Mechanism of Action
Tesamorelin is a synthetic analogue of growth hormone-releasing hormone (GHRH) with a trans-3-hexenoic acid group at the N-terminus that increases its stability against proteolytic degradation. It works by:
- Stimulating endogenous growth hormone secretion — Via GHRH receptor activation in the anterior pituitary.
- Increasing IGF-1 — The pulsatile GH release increases hepatic IGF-1 production, which mediates many of its metabolic effects.
- Reducing visceral adipose tissue — The primary therapeutic effect demonstrated in clinical studies.
Unlike exogenous hGH, tesamorelin preserves the physiological pulsatility of GH release, which may reduce side effects associated with continuous elevated GH exposure.
Research Evidence
- FDA-approved (as Egrifta) for HIV-associated lipodystrophy — one of the few peptides on this list with regulatory approval (in the United States, not Canada).
- Phase III trials: Demonstrated significant reductions in visceral adipose tissue (VAT) in HIV-positive patients with lipodystrophy, with maintained effects over 52 weeks.
- Metabolic parameters: Improved triglycerides, waist circumference, and patient-reported body image distress.
Tesamorelin is particularly relevant for researchers studying the differential regulation of visceral versus subcutaneous fat depots.
🛒 Source for your lab: Tesamorelin — Webber Science
SLU-PP-332
Mechanism of Action
SLU-PP-332 represents a novel class of metabolic peptide: an ERRα/ERRγ (estrogen-related receptor alpha/gamma) agonist. ERRs are orphan nuclear receptors that regulate mitochondrial biogenesis and oxidative metabolism:
- Mitochondrial uncoupling — SLU-PP-332 activates gene programmes that increase fatty acid oxidation and mitochondrial respiration.
- Muscle fibre type shifting — Preclinical data suggest ERR agonism promotes a shift toward type I (slow-twitch, oxidative) muscle fibres.
- Endurance phenotype mimicking — In mouse models, SLU-PP-332 produced metabolic and endurance adaptations similar to exercise training without actual physical activity.
Research Evidence
SLU-PP-332 is the most early-stage compound on this list. Evidence is primarily preclinical:
- Obese mouse models: Significant reductions in fat mass and improvements in exercise capacity.
- In vitro: ERR-dependent gene expression profiles consistent with enhanced oxidative metabolism.
SLU-PP-332 is a compelling compound for researchers investigating exercise mimetics, mitochondrial biology, and non-incretin metabolic pathways.
🛒 Source for your lab: SLU-PP-332 — Webber Science
HGH Fragment 176-191
Mechanism of Action
HGH Fragment 176-191 (commonly called “HGH Frag”) is the C-terminal fragment of human growth hormone comprising amino acids 176–191. This region was identified in the 1980s as the lipolytic domain of hGH:
- Lipolysis promotion — The fragment retains the fat-burning capacity of full-length hGH without stimulating IGF-1 production.
- Anti-lipogenesis — Inhibits acetyl-CoA carboxylase and fatty acid synthase activity in adipocytes.
- No diabetogenic effect — Unlike full-length hGH, the fragment does not impair glucose tolerance or increase insulin resistance.
Research Evidence
- Preclinical rodent studies: Demonstrated dose-dependent reductions in body fat with preserved lean mass.
- Differentiation from AOD9604: While structurally similar (AOD9604 is essentially a modified version of this fragment), HGH Fragment 176-191 lacks the N-terminal tyrosine modification, resulting in a shorter half-life.
- No clinical trials have been completed for this specific fragment; most clinical data come from the AOD9604 programme.
Research Considerations
The shorter half-life of HGH Fragment 176-191 compared to AOD9604 makes it more suitable for studies examining acute lipolytic responses rather than chronic administration models.
🛒 Source for your lab: HGH Fragment 176-191 — Webber Science
Comparing Metabolic Peptides by Mechanism
Selecting the right peptide depends on the signalling pathway under investigation:
| Peptide | Primary mechanism | Clinical stage | Key research application |
|—|—|—|—|
| Tirzepatide | Dual GIP/GLP-1 agonist | Phase III/Approved | Benchmark dual-incretin compound |
| Retatrutide | Triple GIP/GLP-1/Glucagon agonist | Phase II/III | Next-gen incretin research |
| AOD9604 | hGH fragment (lipolytic) | Phase II (halted) | GH-independent lipolysis |
| Tesamorelin | GHRH analogue | FDA-approved (US) | Visceral adipose tissue |
| SLU-PP-332 | ERRα/γ agonist | Preclinical | Mitochondrial/exercise mimetics |
| HGH Fragment 176-191 | hGH C-terminal fragment | Preclinical | Acute lipolysis models |
Sourcing Weight Loss Peptides in Canada
Canadian researchers should consider the following when sourcing metabolic peptides:
1. Regulatory status — Tirzepatide (as Mounjaro/Zepbound) and tesamorelin (as Egrifta) have regulatory approvals in other jurisdictions but are sold by Webber Science for research purposes only.
2. Purity — Look for ≥98% purity with third-party certificates of analysis. Impurities in peptide preparations can produce confounding results, especially in cell-based metabolic assays.
3. Storage — GLP-1 and GIP receptor agonists are generally less stable than shorter peptides; follow COA storage recommendations carefully.
4. Domestic sourcing — Ordering from a Canadian supplier like Webber Science eliminates customs delays and reduces cold-chain risk.
FAQ
Are weight loss peptides approved for human use in Canada?
Tirzepatide is approved in Canada under the brand name Mounjaro for type 2 diabetes (with obesity indication under review). Tesamorelin is not approved in Canada. The other peptides discussed — Retatrutide, AOD9604, SLU-PP-332, and HGH Fragment 176-191 — have no Health Canada approval. All products sold by Webber Science are for in vitro research purposes only.
Is retatrutide more effective than tirzepatide?
Early Phase II data suggest retatrutide may produce greater weight loss than tirzepatide, likely due to its triple-incretin mechanism (adding glucagon receptor agonism). However, head-to-head Phase III trials have not yet been completed. Researchers should interpret cross-trial comparisons cautiously due to differences in study populations and protocols.
What is the difference between AOD9604 and HGH Fragment 176-191?
Both are derived from the C-terminal region of hGH (amino acids 176–191). AOD9604 includes an additional tyrosine residue at the N-terminus that increases metabolic stability and half-life. HGH Fragment 176-191 is the unmodified native sequence. Functionally, they target the same lipolytic mechanism, but pharmacokinetic profiles differ.
Can tirzepatide and retatrutide be compared in the same study?
Yes. Comparative studies of dual versus triple incretin agonists represent a growing area of metabolic research. Differences in receptor binding affinity, pharmacokinetics, and downstream signalling can be examined using both compounds in parallel experimental designs.
📘 Related: Retatrutide vs. Semaglutide vs. Tirzepatide: 2026 Buyer’s Guide
How does SLU-PP-332 differ from incretin-based peptides?
SLU-PP-332 acts on estrogen-related receptors (ERRα/γ) rather than incretin receptors (GIP, GLP-1, glucagon). It promotes mitochondrial biogenesis and oxidative metabolism — essentially mimicking exercise-induced metabolic adaptations. This makes it mechanistically distinct from all incretin-based weight-loss peptides.
What storage conditions are recommended for metabolic peptides?
Lyophilized peptides should be stored at −20°C. After reconstitution, most metabolic peptides should be kept at 2–8°C and used within the time frame specified on the COA. GLP-1 receptor agonists may be more sensitive to temperature fluctuations; follow product-specific guidelines.
Browse Weight Loss & Metabolic Peptides
Ready to source metabolic peptides for your research? Explore the full catalogue at Webber Science:
All products are for research purposes only. Not for human or veterinary use.
References
- Jastreboff, A.M. et al. (2022). “Tirzepatide Once Weekly for the Treatment of Obesity.” *NEJM*, 387(3), 205–216.
- Bray, G.A. et al. (2023). “Retatrutide — a triple hormone agonist for the treatment of obesity.” *NEJM*, 389(7), 614–626.
- Heffernan, M. et al. (2006). “AOD9604, a novel anti-obesity drug.” *International Journal of Obesity*, 30, S189.
- Stanley, T.L. et al. (2021). “Tesamorelin effects on visceral adipose tissue.” *Journal of Clinical Endocrinology & Metabolism*.
- Losby, W.D. et al. (2023). “Pharmacological activation of ERRα/γ mimics exercise training.” *Cell Metabolism*, 37(4), 1–15.
- Heffernan, M. et al. (2001). “The lipolytic domain of hGH: hGH 177-191.” *Growth Hormone & IGF Research*, 11, S155–S162.
- Tirzepatide Complete Guide for Canadian Researchers