Research-grade retatrutide 10mg is available to South African laboratories in 2026 at roughly R2,000–R4,000 per vial, sold strictly for in vitro and preclinical use and not registered by SAHPRA for human application. Retatrutide (LY3437943) is a fatty-acylated 39-amino-acid peptide that acts as a full triple agonist at the human GLP-1 receptor (GLP-1R), GIP receptor (GIPR), and glucagon receptor (GcgR), first characterised by Coskun et al. (2022) and advanced through the Jastreboff et al. NEJM 2023 Phase 2 obesity trial.
Key Takeaways
- Retatrutide is the only clinically advanced triple GLP-1R/GIPR/GcgR agonist peptide; the glucagon component drives hepatic and adipose energy expenditure absent in tirzepatide and semaglutide
- Phase 2 data (Jastreboff et al., NEJM 5 July 2023) showed ~24% mean body-weight reduction at 12 mg weekly; no Phase 3 results have been published as of May 2026
- South African sourcing ranges R2,000–R4,000 per 10mg vial; verify Certificate of Analysis (CoA), HPLC purity ≥98%, and cold-chain documentation before procurement
- Retatrutide is not SAHPRA-registered and must be labelled and used exclusively for research; human use is prohibited under South African law
- For receptor-level benchmarking, run retatrutide against a tirzepatide dual-agonist control and a semaglutide GLP-1R-selective control to isolate the GcgR contribution
What Is Retatrutide? The Triple-Agonist Mechanism Explained
Retatrutide (INN: retatrutide; development code LY3437943) is a long-acting, fatty-acylated 39-amino-acid peptide developed by Eli Lilly. It is a full agonist at three class B G protein-coupled receptors simultaneously: GLP-1R, GIPR, and GcgR. The C20 fatty diacid moiety drives albumin binding, extending the peptide's circulating half-life and supporting once-weekly dosing in human trials.
Each receptor contributes a distinct metabolic signal in research models:
- GLP-1R activation reduces food intake and enhances β-cell insulin secretion
- GIPR agonism contributes to insulin sensitisation in adipose tissue and amplifies GLP-1R-driven appetite suppression in the hindbrain, though the precise interaction remains an active research question
- GcgR activation stimulates hepatic glucose output and increases resting energy expenditure and lipolysis via hepatic and brown adipose pathways
Why the glucagon arm matters for receptor-level comparison
The glucagon component distinguishes retatrutide from tirzepatide at the receptor level. Tirzepatide is a GLP-1R/GIPR dual agonist with no meaningful GcgR activity, registered by SAHPRA under the brand Mounjaro for type 2 diabetes. Researchers comparing the two molecules in vitro should source a tirzepatide research peptide reference standard alongside retatrutide to isolate the GcgR contribution in functional assays.
Semaglutide is a GLP-1R-selective agonist, making a semaglutide peptide the cleanest monoreceptor comparator in a three-arm experimental design.
Coskun et al. (2022) characterised retatrutide as a balanced triple agonist with sub-nanomolar potency at all three human receptors. The exact EC50 (half-maximal effective concentration) values sit in the supplementary tables of the original JCI publication.
Retatrutide vs Tirzepatide vs Semaglutide: Receptor Comparison
Retatrutide is the only molecule of the three with meaningful glucagon receptor (GcgR) activity, the pharmacological feature South African researchers need to isolate when designing energy-expenditure assays.
| Parameter | Retatrutide (LY3437943) | Tirzepatide | Semaglutide |
|---|---|---|---|
| GLP-1R agonism | Full agonist, sub-nanomolar potency | Full agonist | Full agonist, selective |
| GIPR agonism | Full agonist, sub-nanomolar potency | Full agonist | None |
| GcgR agonism | Full agonist, sub-nanomolar potency | None | None |
| Molecular weight | ~4.8 kDa (C20-acylated 39-mer) | ~4.8 kDa | ~4.1 kDa |
| Half-life (human) | Multi-day, supports weekly dosing | ~5 days | ~7 days |
| Highest clinical dose studied | 12 mg weekly, Phase 2 obesity | 15 mg weekly | 2.4 mg weekly (obesity) |
Source note: Receptor pharmacology from Coskun et al., JCI 2022; clinical pharmacokinetics and dose data from Jastreboff et al., NEJM 2023. A tirzepatide research peptide and semaglutide peptide reference sample alongside retatrutide allow the GcgR contribution to be subtracted analytically.
Why the GcgR column matters for energy-expenditure research
GcgR agonism drives the hepatic and brown-adipose thermogenic signal absent in tirzepatide and semaglutide. In a three-arm in vitro design, retatrutide-treated hepatocytes or adipocytes show elevated cyclic adenosine monophosphate (cAMP) and lipolytic flux relative to the dual- and mono-agonist controls because the glucagon receptor is the only pathway retatrutide engages that the other two molecules cannot.
Key Clinical Trial Data: Phase 2 Results (2023) and Phase 3 Status (2026)
The Phase 2 obesity trial published by Jastreboff et al. in NEJM on 5 July 2023 reported a mean body-weight reduction of approximately 24% at 48 weeks on the 12 mg weekly retatrutide dose, the largest placebo-adjusted weight loss recorded for any incretin-class molecule at that point. The trial enrolled 338 adults with obesity (body mass index (BMI) ≥30, or ≥27 with a weight-related comorbidity) in a randomised, double-blind, dose-ranging design across 1, 4, 8 and 12 mg weekly arms versus placebo, with percentage change in body weight as the primary endpoint.
Secondary endpoints relevant to in vitro and preclinical workstreams included waist circumference, fasting insulin, HbA1c (glycated haemoglobin), and a full lipid panel (LDL-C, HDL-C, triglycerides). All moved in directions consistent with the combined GLP-1R, GIPR and GcgR pharmacology described in the Coskun 2022 receptor characterisation.
For a research group benchmarking retatrutide against a tirzepatide research peptide or a semaglutide peptide, the Phase 2 lipid and fasting-insulin deltas provide the most useful published reference for expected directionality in downstream metabolic assays.
Phase 3 TRIUMPH programme status as of May 2026
As of May 2026, no Phase 3 TRIUMPH trial for retatrutide has reported primary outcome results in a peer-reviewed journal. Eli Lilly pipeline disclosures through early 2026 continue to list LY3437943 as in active Phase 2/3 development for obesity and related cardiometabolic indications, with Phase 3 initiation dated to 2024 and projected primary completions in the 2026–2027 window.
Any quantitative claim circulating about Phase 3 weight-loss magnitudes, cardiovascular outcomes, or MASH endpoints should be treated as speculative until top-line readouts appear on ClinicalTrials.gov or in a peer-reviewed publication. Unpublished data cannot be independently verified.
Researchers procuring retatrutide 10mg in South Africa in 2026 should anchor study design to the NEJM 2023 Phase 2 dataset and the Coskun 2022 preclinical package, not to unpublished Phase 3 figures.
Retatrutide 10mg: Specification and Research Applications
Retatrutide 10mg is supplied as a lyophilised white powder in a sealed glass vial, manufactured to a research-grade purity specification of ≥98% by high-performance liquid chromatography (HPLC) and intended exclusively for in vitro and preclinical use. The 10mg fill size suits multi-experiment protocols, allowing a single vial to be aliquoted across dose-response curves, receptor binding assays, and replicate cell-culture runs without exhausting stock mid-study.
For reconstitution, our standard bench protocol uses sterile water for injection or bacteriostatic water (0.9% benzyl alcohol) at a working concentration calculated against the ~4.8 kDa molecular weight of LY3437943. Add the diluent down the vial wall and swirl rather than shake to limit shear and foaming. pH adjustment to ~7.0–7.4 and 0.22 μm filtration are advisable where the reconstituted peptide enters cell-culture media, as these steps remove particulates and stabilise the peptide under physiological conditions.
Polaris Peptides' 2024 product documentation for retatrutide 10mg recommends storing the lyophilised vial at −20 °C in a desiccated, light-protected environment, with reconstituted solution held at 2–8 °C and work completed within 28 days. Repeated freeze-thaw cycles should be avoided. Single-use aliquots stored at −20 °C or below are preferable for assays running beyond a month.
Research applications supported by the 10mg format
A 10mg vial reliably covers the following workstreams:
- Receptor binding and cAMP accumulation assays at human GLP-1R, GIPR and GcgR, benchmarking retatrutide against a tirzepatide research peptide (dual GLP-1R/GIPR) and a GLP-1R-selective semaglutide peptide
- In vitro 3T3-L1 adipocyte and primary hepatocyte models probing lipolysis, lipogenesis and glucose uptake, an open niche given the absence of indexed 2024–2026 third-party in vitro retatrutide papers
- Rodent metabolic phenotyping (body composition, fasting insulin, hepatic triglyceride) anchored to the Coskun 2022 preclinical package
How Retatrutide's Glucagon Component Adds Research Value
The GcgR arm distinguishes retatrutide pharmacologically from tirzepatide and gives the molecule its distinct energy-expenditure signature in preclinical models. Hepatic GcgR activation drives glycogenolysis, gluconeogenesis and fatty-acid oxidation. Extrahepatic signalling has been linked to lipolysis in white adipose tissue and, in rodents, to uncoupling protein 1 (UCP1)-mediated thermogenesis in brown adipose tissue.
For in vitro work, GcgR engagement is the mechanistic lever you are probing whenever you measure hepatocyte glucose output, adipocyte cAMP responses or mitochondrial uncoupling readouts that a tirzepatide research peptide cannot activate.
The design rationale is a push-pull energy balance model: GLP-1R and GIPR agonism suppress food intake and improve insulin secretion and sensitivity, while GcgR agonism increases basal energy expenditure and hepatic lipid oxidation. Coskun et al. (2022) reported that in diet-induced obese mice, retatrutide produced greater fat-mass reduction than matched dual GLP-1R/GIPR agonism at comparable doses. The glucagon component drives additional hepatic and adipose lipolysis rather than further appetite suppression.
The 2023 NEJM Phase 2 readout (Jastreboff et al.) was consistent with this expenditure-weighted profile, with weight loss exceeding what GLP-1R-selective comparators such as a semaglutide peptide have produced in equivalent populations.
Isolated GcgR agonism risks hyperglycaemia through unopposed hepatic glucose output, which is why the GLP-1R component is structurally non-negotiable. Incretin-driven insulin secretion counterbalances glucagon-driven glucose production. For assay design, this means GcgR-only and GLP-1R-only controls (or selective antagonists such as des-His1-[Glu9]-glucagon amide) belong in any retatrutide receptor-deconvolution experiment, particularly in primary hepatocyte glucose-output assays where the net signal is the algebraic sum of opposing pathways.
Sourcing Retatrutide 10mg in South Africa: What Researchers Should Know
Retatrutide is not a SAHPRA-registered medicine in South Africa as of 2026 and is supplied locally only as a research chemical for in vitro and preclinical laboratory use. The South African Health Products Regulatory Authority (www.sahpra.org.za) governs medicines and scheduled substances under the Medicines and Related Substances Act 101 of 1965 (as amended). No triple GLP-1/GIP/glucagon agonist has been gazetted as a registered product under that framework.
South African online retailers listing "retatrutide" routinely flag the compound as a research peptide and explicitly not SAHPRA-approved for human use.
Price discovery in the local market is wide. A Shifa listing shows retatrutide 10mg at a promotional R3,900 (from R7,000). Higher-mass vials and pens from Noventra Pharma and DEX-branded stock sit in the R1,600–R2,800 band for 30–32mg formats. International research suppliers price 10mg lyophilised vials around US$120–170, which translates to roughly R2,000–R3,200 per 10mg before shipping, duties and VAT at 2025–2026 exchange rates.
A defensible procurement budget for South African labs is therefore approximately R2,000–R4,000 per 10mg landed.
Supplier due diligence checklist
Before placing an order, request and verify:
- Certificate of Analysis (CoA) with HPLC purity (≥98% is the working benchmark for incretin peptides)
- Mass spectrometry confirmation consistent with a C20-acylated 39-mer at ~4.8 kDa
- Lyophilised presentation with documented storage at −20 °C dry, 2–8 °C reconstituted, used within 28 days
- Cold-chain or insulated shipping with tracked, signed delivery to a registered laboratory address
- Written research-use-only disclaimer on the invoice and product page
JCSG.org supplies research-grade peptides with tracked, discreet shipping and CoA documentation on request. For receptor-level benchmarking against the dual-agonist tirzepatide research peptide or the GLP-1R-selective semaglutide peptide, order matched lots from the same supplier to minimise inter-vendor variance in your assay panel. All material is sold for laboratory use only and is not for human consumption.
Retatrutide vs Other Next-Generation Peptides in the Research Pipeline
Retatrutide is the most clinically advanced triple GLP-1R/GIPR/GcgR agonist peptide in development as of 2026, sitting one receptor ahead of tirzepatide's dual mechanism and structurally distinct from amylin-based and oral small-molecule candidates. For a South African lab building a comparator panel, four molecules define the current incretin and metabolic peptide pipeline.
Pipeline comparators worth stocking alongside retatrutide
Tirzepatide (LY3298176) remains the reference dual GLP-1R/GIPR acylated peptide and is the natural mechanistic predecessor to retatrutide. Labs benchmarking glucagon-receptor contribution typically run retatrutide against the tirzepatide research peptide at matched molar concentrations to isolate the GcgR signal, then against the GLP-1R-selective semaglutide peptide to anchor the GLP-1R-only baseline.
Cagrilintide, a long-acting amylin analogue, is studied in fixed-ratio combination with semaglutide (CagriSema) under Novo Nordisk's REDEFINE Phase 3 programme. It offers a non-incretin co-agonist axis useful for satiety-pathway dissection in adipocyte and hypothalamic models.
Orforglipron, Eli Lilly's oral non-peptide GLP-1R agonist, sits outside the peptide-handling workflow entirely (no lyophilisation, no cold chain) but appears increasingly in 2025–2026 comparative weight-loss literature. For peptide chemists it is a useful pharmacological control rather than a replacement reagent. Retatrutide retains the only triple-receptor profile in advanced clinical development through 2026.
Frequently Asked Questions: Retatrutide 10mg Research Use
What is the molecular weight of retatrutide?
Retatrutide (LY3437943) is a C20 fatty-acylated 39-amino-acid peptide with an approximate molecular weight of ~4.8 kDa. The exact monoisotopic mass sits in the 4,700–4,800 Da range across vendor specification sheets mirroring the Lilly-published sequence because the C20 acyl modification adds approximately 300 Da to the unmodified 39-mer backbone. For molar calculations in receptor assays, ~4,800 Da is a workable approximation.
How should retatrutide 10mg be reconstituted for in vitro assays?
In our lab we reconstitute lyophilised retatrutide 10 mg in sterile water or phosphate-buffered saline (PBS) to a 1 mg/mL working stock. We filter through 0.22 μm if destined for cell culture, then aliquot into low-protein-binding tubes for single-use freezing at −20 °C. Vendor guidance recommends 2–8 °C for in-solution work and completion within 28 days to limit deamidation and oxidation of the peptide backbone.
What is the difference between retatrutide and tirzepatide at the receptor level?
Retatrutide is a balanced full agonist at GLP-1R, GIPR, and the glucagon receptor (GcgR), whereas tirzepatide engages only GLP-1R and GIPR with no meaningful GcgR activity. The added glucagon arm is the mechanistic basis for retatrutide's hepatic lipid and energy-expenditure signal absent from tirzepatide and from the GLP-1R-selective semaglutide comparator.
Is retatrutide approved by SAHPRA?
No. As of 2026 SAHPRA has not registered any retatrutide-containing product for human use, and no scheduling notice names retatrutide or GLP-1/GIP/glucagon triple agonists specifically. South African suppliers consistently label vials and pens as "research peptide, not SAHPRA-approved" because the Medicines and Related Substances Act framework requires explicit registration before a compound can be marketed for human use.
What purity grade is required for receptor binding research?
Receptor binding and cAMP accumulation assays at GLP-1R, GIPR, and GcgR require ≥98% HPLC purity to keep truncated-sequence and oxidised by-products from skewing EC50 determinations. Even 2–5% impurity can shift potency estimates by 10–20% in sensitive functional assays. Vendor CoAs should include HPLC chromatograms and mass-spec confirmation of the ~4.8 kDa parent ion before material enters quantitative pharmacology workflows.
Next Steps for South African Researchers
Start by sourcing matched-lot retatrutide, tirzepatide and semaglutide research peptides from a single South African or regional supplier with documented CoA and cold-chain tracking. Request the vendor's HPLC and mass-spectrometry data before payment, and confirm that all material is labelled for research use only. Run your initial dose-response curves against the Phase 2 NEJM dataset (Jastreboff et al., 5 July 2023) and the Coskun 2022 preclinical receptor characterisation to validate assay performance. Document your reconstitution protocol, storage conditions, and lot numbers in your laboratory notebook to enable reproducibility across future experiments. If you encounter unexpected potency shifts or off-target signalling, contact your supplier's technical team and request a replacement CoA or fresh aliquot before troubleshooting your assay design.
