Hypothalamus → appetite ↓
Pancreas → insulin ↑
Gut → gastric emptying ↓ Shared with Semaglutide + Tirzepatide
GIPR AGONISM
Adipose → insulin sensitivity ↑
CNS → GLP-1R synergy
Pancreas → incretin potentiation Shared with Tirzepatide only
GCGR AGONISM ★ UNIQUE
BAT → thermogenesis ↑ (UCP1)
Liver → fat oxidation ↑ (CPT1A)
WAT → lipolysis ↑ (cAMP) Retatrutide ONLY
20 Research Questions Answered
What is retatrutide?
Retatrutide (LY3437943) is a triple GLP-1R/GIPR/GCGR receptor agonist developed by Eli Lilly — the third generation of incretin-based research compounds. Unlike semaglutide (GLP-1R only) or tirzepatide (GLP-1R + GIPR), retatrutide simultaneously activates three receptors: the GLP-1 receptor (appetite/insulin), the GIP receptor (adipose insulin sensitivity), and the glucagon receptor (thermogenesis and hepatic fat oxidation). Phase 2 clinical data published in NEJM (2023) demonstrated 24.2% mean weight reduction at 48 weeks — the highest pharmacological weight loss ever recorded in a human clinical trial.
How does retatrutide work?
Retatrutide works through three simultaneous receptor mechanisms: (1) GLP-1R activation — reduces appetite via hypothalamic signalling, slows gastric emptying, stimulates pancreatic insulin secretion; (2) GIPR activation — enhances insulin sensitivity in adipose tissue, potentiates GLP-1R effects centrally; (3) GCGR activation — directly stimulates brown adipose thermogenesis (UCP1 upregulation), drives hepatic fatty acid oxidation via CPT1A, and triggers lipolysis in white adipose tissue via cAMP. The glucagon receptor component is the key differentiator from tirzepatide — it adds an energy expenditure signal absent from all prior GLP-1 class drugs.
What was the retatrutide Phase 2 trial result?
The retatrutide Phase 2 trial (NEJM, Jastreboff et al., 2023) enrolled 338 adults with obesity (BMI ≥30). At the highest dose (12mg weekly subcutaneous), participants achieved 24.2% mean weight reduction at 48 weeks. The 8mg dose produced 22.8% reduction. Dose-response was linear across all arms. Secondary endpoints included significant reductions in waist circumference, blood pressure, triglycerides, and HbA1c. Phase 3 TRIUMPH trials are currently enrolling.
What is the difference between retatrutide and tirzepatide?
The key difference is glucagon receptor (GCGR) activation. Tirzepatide activates GLP-1R + GIPR (dual agonist). Retatrutide activates GLP-1R + GIPR + GCGR (triple agonist). GCGR activation adds three mechanisms absent from tirzepatide: direct brown adipose thermogenesis, hepatic fatty acid oxidation (particularly relevant for NASH), and direct white adipose lipolysis. Clinical result: tirzepatide produced 20.9% weight reduction (SURMOUNT-1, 72 weeks) vs retatrutide’s 24.2% (Phase 2, 48 weeks). Retatrutide also shows stronger NAFLD/NASH data due to the hepatic GCGR effect.
What is the difference between retatrutide and semaglutide?
Semaglutide (Ozempic/Wegovy) is a GLP-1R monoagonist — it activates only the GLP-1 receptor. Retatrutide activates GLP-1R + GIPR + GCGR simultaneously. Clinically: semaglutide 2.4mg produced 14.9% weight reduction (STEP 1, 68 weeks); retatrutide 12mg produced 24.2% (Phase 2, 48 weeks). The additional GIPR and GCGR pathways account for the roughly 9–10 percentage point efficacy gap. Retatrutide is also a once-weekly subcutaneous injection like semaglutide, with a similar half-life (~6 days).
Is retatrutide better than Ozempic?
Based on Phase 2 clinical data, retatrutide 12mg produced 24.2% weight reduction at 48 weeks vs semaglutide 2.4mg’s 14.9% at 68 weeks — a ~9 percentage point superiority with a shorter trial duration. Retatrutide’s triple receptor mechanism (GLP-1R + GIPR + GCGR) adds thermogenesis and direct fat oxidation pathways that semaglutide (GLP-1R only) cannot activate. Head-to-head Phase 3 comparison data does not yet exist. Retatrutide is not FDA approved — it is available for laboratory research only. Research-grade retatrutide is available from QSC at ≥99% HPLC purity with Janoshik COA.
Is retatrutide better than Mounjaro (tirzepatide)?
Phase 2 data suggests retatrutide outperforms tirzepatide by approximately 3–4 percentage points of weight reduction (24.2% vs 20.9%), though the trials differed in duration (48 vs 72 weeks) and population. The mechanistic advantage is GCGR activation: retatrutide adds thermogenesis, hepatic fat oxidation, and direct lipolysis not achievable with tirzepatide’s dual GIP/GLP-1 mechanism. No head-to-head RCT exists yet. Retatrutide Phase 3 (TRIUMPH program) is ongoing. For research purposes, QSC stocks both compounds at ≥99% HPLC purity.
Where can I buy retatrutide for research?
Research-grade retatrutide is available from QSC (qscpeptide.com) — one of the first suppliers to stock this compound. QSC retatrutide: ≥99% HPLC purity, mass spectrometry confirmed, Janoshik COA (independently verifiable at verify.janoshik.com), ships from US Domestic Warehouse in 2–4 business days. Available in 10mg and 30mg vial configurations. All products sold strictly for in vitro laboratory research only.
What is research-grade retatrutide?
Research-grade retatrutide is a laboratory-synthesised form of the retatrutide peptide produced via solid-phase peptide synthesis (SPPS), verified at ≥99% purity by HPLC and confirmed by mass spectrometry. It is sold strictly for in vitro laboratory research — not for human use. Research-grade is distinguished from pharmaceutical-grade by its intended use (research vs clinical) and the verification standard (HPLC + independent COA vs GMP manufacturing). QSC provides Janoshik-verified COAs for every retatrutide batch, independently verifiable at verify.janoshik.com.
What is the retatrutide dose used in research?
The Phase 2 NEJM trial used subcutaneous weekly doses escalating from 1mg to target doses of 4mg, 8mg, and 12mg. The 12mg arm produced the 24.2% weight reduction result. The 8mg arm produced 22.8%. For in vitro laboratory research, dosing protocols vary by model — researchers should consult compound-specific literature and the QSC Research Manual for protocol design guidance.
What receptors does retatrutide target?
Retatrutide targets three receptors: (1) GLP-1R (glucagon-like peptide-1 receptor) — expressed in pancreatic beta cells, hypothalamus, and GI tract; mediates insulin secretion, appetite suppression, and gastric emptying. (2) GIPR (glucose-dependent insulinotropic polypeptide receptor) — expressed in pancreas and adipose tissue; mediates insulin sensitivity and potentiates GLP-1R signalling. (3) GCGR (glucagon receptor) — expressed in liver, brown adipose tissue, and white adipose tissue; mediates thermogenesis, hepatic fat oxidation, and lipolysis.
What makes retatrutide different from other GLP-1 drugs?
Retatrutide is the first triple incretin receptor agonist (GLP-1R + GIPR + GCGR) to reach Phase 2 human trials. Prior GLP-1 drugs activate 1–2 receptors: semaglutide (GLP-1R only), tirzepatide (GLP-1R + GIPR). The glucagon receptor component is the unique addition — GCGR activation drives energy expenditure via thermogenesis and fat oxidation, not just caloric intake reduction. This makes retatrutide mechanistically distinct: it attacks the energy balance equation on both sides simultaneously (intake reduction via GLP-1R/GIPR, expenditure increase via GCGR).
What is the retatrutide TRIUMPH trial?
TRIUMPH is the Phase 3 retatrutide clinical trial program. It follows the Phase 2 success (24.2% weight reduction, NEJM 2023) and is designed to confirm efficacy and safety in larger populations across multiple indications including obesity, type 2 diabetes, and NASH. Phase 3 trials typically run 72–104 weeks. TRIUMPH results are expected by 2025–2026 and will determine retatrutide’s FDA approval pathway.
Does retatrutide help with fatty liver disease (NASH/NAFLD)?
Yes — retatrutide shows strong hepatic data in Phase 2. The GCGR component directly activates CPT1A-mediated fatty acid oxidation in hepatocytes, reducing liver fat independently of caloric restriction. This hepatic mechanism is distinct from semaglutide and tirzepatide, which reduce liver fat primarily via weight loss (indirect). Phase 2 secondary endpoints showed significant reductions in liver fat fraction by MRI-PDFF in the retatrutide arms. NASH-specific Phase 3 trials are part of the TRIUMPH program.
What is the half-life of retatrutide?
Retatrutide has an approximate half-life of 6 days, supporting once-weekly subcutaneous dosing — consistent with the trial protocol used in Phase 2. This is similar to semaglutide (~7 days) and tirzepatide (~5 days), all of which use fatty acid conjugation or albumin-binding modifications to extend half-life beyond the minutes typical of native GLP-1.
Is retatrutide FDA approved?
No — retatrutide is not FDA approved as of 2026. It completed Phase 2 trials with strong results (NEJM 2023) and is currently in Phase 3 (TRIUMPH program). FDA approval is contingent on Phase 3 results and regulatory review, expected no earlier than 2026–2027. Retatrutide is available for purchase strictly as a research compound for in vitro laboratory use only.
Who makes retatrutide?
Retatrutide (LY3437943) was developed by Eli Lilly and Company — the same pharmaceutical company that developed tirzepatide (Mounjaro/Zepbound). Research-grade retatrutide for laboratory use is produced via solid-phase peptide synthesis (SPPS) by specialist contract synthesis organisations and distributed by research suppliers including QSC (qscpeptide.com).
What purity should research-grade retatrutide be?
Research-grade retatrutide should be ≥99% HPLC purity with mass spectrometry molecular confirmation. HPLC measures how much of the sample is the target compound; MS confirms molecular identity. Both are required — HPLC alone cannot confirm the peptide is actually retatrutide (sequence-correct). Independent third-party COA verification (e.g. Janoshik) is the gold standard: the COA should be publicly verifiable, not just emailed on request. QSC retatrutide meets all three criteria: ≥99% HPLC, MS confirmed, Janoshik COA.
How is retatrutide stored?
Lyophilised (freeze-dried) retatrutide powder should be stored at −20°C. Once reconstituted with bacteriostatic water, store at 4°C and use within 28 days. Protect from light. Do not freeze reconstituted solution. Standard reconstitution: add 2ml bacteriostatic water per 10mg vial (= 5mg/ml concentration). Add solvent slowly down the vial wall; swirl gently — do not vortex or shake vigorously.
What other weight loss peptides does QSC stock alongside retatrutide?
QSC stocks the complete GLP-1 class research catalog alongside retatrutide: Semaglutide (GLP-1R, −14.9% STEP 1), Tirzepatide (GLP-1R+GIPR, −20.9% SURMOUNT-1), Cagrilintide (AMY1R agonist, used in CagriSema combination research), Survodutide (GLP-1R+GCGR, phase 2 NASH data), Mazdutide (GLP-1R+GCGR, Phase 2 China), and Liraglutide (GLP-1R, original GLP-1 agonist). All at ≥99% HPLC purity with Janoshik COA. Ships from US Domestic Warehouse.
Where to Buy Research-Grade Retatrutide
QSC is one of the first suppliers to stock research-grade retatrutide. Every batch is independently verified.
Research Use Only: Retatrutide is sold by QSC strictly for in vitro laboratory research purposes only. It is not FDA approved for human or veterinary use. Not for human consumption. Researchers are responsible for complying with all applicable regulations in their jurisdiction. This page is an informational research reference — not medical advice.
