Mechanism

How Retatrutide Works

Retatrutide is an investigational once-weekly injectable peptide studied by Eli Lilly and Company as an agonist at three receptors. This page describes the receptor targets as they are stated in registry and literature records. Informational only; not medical advice.

Receptor targets

Three receptor pathways

GLP-1 receptor

Associated with appetite regulation, delayed gastric emptying and glucose-dependent insulin secretion.

GIP receptor

Implicated in insulin response and adipose tissue metabolism; the basis of dual-agonist approaches.

Glucagon receptor

Studied for its contribution to energy expenditure and hepatic lipid handling alongside incretin effects.

Reference

What the records show

Receptor Mechanism and Agonism

Retatrutide (development code LY3437943) is characterized pharmacologically as a triple receptor agonist. It targets three distinct metabolic hormone receptors:

Glucagon-Like Peptide-1 (GLP-1) Receptor
Glucose-Dependent Insulinotropic Polypeptide (GIP) Receptor
Glucagon Receptor

According to published pharmacological reviews, GLP-1 and GIP are incretin hormones recognized for their ability to stimulate insulin secretion. While single-incretin and dual-incretin therapies engage GLP-1 or both GLP-1 and GIP receptors, retatrutide integrates activity at a third receptor pathway by also engaging the glucagon receptor.

Retatrutide is being developed by Eli Lilly and Company and remains an investigational drug. It has not been approved by regulatory agencies, and its safety and clinical efficacy are currently undergoing formal assessment in human clinical trials.

Preclinical Research Directions

Preclinical research has evaluated the multi-receptor action of retatrutide across experimental animal and cellular models:

Renal Fibrosis and Inflammation: Preclinical research evaluated the comparative effects of semaglutide, tirzepatide, and retatrutide on non-diabetic renal fibrosis. The study assessed anti-fibrotic and anti-inflammatory markers using human HK-2 cells as well as unilateral ureteral obstruction (UUO) and aging murine models.
Cognitive and Neurodegenerative Models: Preclinical work has examined retatrutide in streptozotocin-induced diabetic rat models to assess potential effects on learning, memory, and neuroinflammatory pathways associated with diabetes mellitus.

Additional details on these basic research models can be explored via [retatrutide renal fibrosis research](/research/comparative-effects-of-semaglutide-tirzepatide-and-retatrutide-on-renal-fibrosis-42630988) and [retatrutide cognitive research in diabetic models](/research/effects-of-retatrutide-on-learning-and-memory-in-streptozotocin-induced-male-dia-42385950).

Phase 3 Clinical Trial Program

The clinical evaluation of retatrutide spans multiple large-scale Phase 3 trials designed to measure primary endpoints across glycemic control, weight change, and organ-specific outcomes.

Trial Identifier	Trial Name	Indication / Population	Enrolment	Comparators / Interventions	Primary Endpoints
[NCT05929066](/trials/triumph-1)	TRIUMPH-1	Obesity, Overweight, Knee Osteoarthritis, Obstructive Sleep Apnea	2,335	Retatrutide vs. Placebo	Percent Change in Body Weight; AHI Events Per Hour; WOMAC Pain Subscale Score
NCT05931367	TRIUMPH-4	Obesity, Overweight, Knee Osteoarthritis	445	Retatrutide vs. Placebo	WOMAC Pain Subscale Score; Percent Change in Body Weight
NCT06662383	TRIUMPH-5	Obesity	800	Retatrutide vs. Tirzepatide	Percent Change in Body Weight
[NCT07357415](/trials/triumph-9-nct07357415)	TRIUMPH-9	Obesity, Overweight	600	Retatrutide	Percent Change from Baseline in Body Weight
[NCT06383390](/trials/triumph-outcomes)	TRIUMPH-Outcomes	Atherosclerotic Cardiovascular Disease (ASCVD), Chronic Kidney Disease (CKD)	10,000	Retatrutide vs. Placebo	Composite Endpoints; Composite of ESKD, ≥40% Sustained eGFR Decline, CV Death, or Renal Death
NCT06354660	TRANSCEND-T2D-1	Type 2 Diabetes (Inadequate glycemic control with diet and exercise)	537	Retatrutide vs. Placebo	Change from Baseline in Hemoglobin A1c (HbA1c) (%)
NCT06260722	TRANSCEND-T2D-2	Type 2 Diabetes (Inadequate control with metformin ± SGLT2i)	1,250	Retatrutide vs. Semaglutide	Change from Baseline in Hemoglobin A1c (HbA1c) (%)

Endpoints Under Investigation

Across these trials, primary endpoints measure specific physiological and clinical markers:

Glycemic Control: Measured via percent change from baseline in Hemoglobin A1c (HbA1c) in the TRANSCEND-T2D-1 and TRANSCEND-T2D-2 studies.
Weight Regulation: Assessed via percent change from baseline in body weight in TRIUMPH-1, TRIUMPH-4, TRIUMPH-5, and TRIUMPH-9.
Joint Pain and Function: Measured through the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Subscale in participants with knee osteoarthritis in TRIUMPH-1 and TRIUMPH-4.
Respiratory Outcomes: Measured by changes in the Apnea-Hypopnea Index (AHI) events per hour in participants with obstructive sleep apnea in TRIUMPH-1.
Cardio-Kidney Outcomes: Assessed in TRIUMPH-Outcomes (NCT06383390) via time to first occurrence of composite cardiovascular events and kidney composite endpoints, including end-stage kidney disease (ESKD), sustained ≥40% decline in estimated glomerular filtration rate (eGFR), cardiovascular death, or renal death.

Regulatory and Expanded Access Status

Retatrutide remains an investigational product that has not been approved by any regulatory authority. Eli Lilly and Company sponsors an active expanded access program ([NCT07629401](/trials/pre-approval-expanded-access-of-retatrutide-ly3437943-nct07629401)), titled *Pre-approval Expanded Access of Retatrutide (LY3437943)*, listed for obesity and obesity-related complications.

Sources

ClinicalTrials.gov Record: NCT07629401
ClinicalTrials.gov Record: NCT06383390 (TRIUMPH-Outcomes)
ClinicalTrials.gov Record: NCT07357415 (TRIUMPH-9)
ClinicalTrials.gov Record: NCT05929066 (TRIUMPH-1)
ClinicalTrials.gov Record: NCT05931367 (TRIUMPH-4)
ClinicalTrials.gov Record: NCT06662383 (TRIUMPH-5)
ClinicalTrials.gov Record: NCT06260722 (TRANSCEND-T2D-2)
ClinicalTrials.gov Record: NCT06354660 (TRANSCEND-T2D-1)
Behavioural Brain Research, PMID 42385950 (2026-10-02)
iScience, PMID 42630988 (2026-09-18)
Pharmacological Research, PMID 42556625 (2026-09-01)
Annals of Internal Medicine, PMID 42673585 (2026-09-01)
Kidney Research and Clinical Practice, PMID 42682157 (2026-09-01)
Indian Journal of Pharmacology, PMID 42683980 (2026-09-01)
Cardiovascular Diabetology, PMID 42649514 (2026-08-26)

Key facts

Compound Name: Retatrutide
Development Code: LY3437943
Developer: Eli Lilly and Company
Mechanism: GLP-1 / GIP / Glucagon receptor agonist
Development Stage: Phase 3
Regulatory Status: Investigational

Page provenance

Last verified: 4 Sept 2026
Published: 4 Sept 2026
Editorial review: Reviewed

Source records

clinical trial
NCT07629401 — Pre-approval Expanded Access of Retatrutide (LY3437943)
Official source
clinical trial
NCT05931367 — TRIUMPH-4
Official source
clinical trial
NCT06260722 — Effect of Retatrutide Compared With Semaglutide in Adult Participants With Type 2 Diabetes and Inadequate Glycemic Control With Metformin With or Without SGLT2 Inhibitor (TRANSCEND-T2D-2)
Official source
clinical trial
NCT06383390 — The Effect of Retatrutide Once Weekly on Cardiovascular Outcomes and Kidney Outcomes in Adults Living With Obesity (TRIUMPH-Outcomes)
Official source
clinical trial
NCT06662383 — TRIUMPH-5
Official source
clinical trial
NCT07357415 — TRIUMPH-9
Official source
clinical trial
NCT06354660 — Effect of Retatrutide Compared With Placebo in Adult Participants With Type 2 Diabetes and Inadequate Glycemic Control With Diet and Exercise Alone (TRANSCEND-T2D-1)
Official source
clinical trial
NCT05929066 — TRIUMPH-1
Official source
drug
Retatrutide (LY3437943) — internal compound record
publication
PMID 42682157 — Incretin-based therapies in diabetic kidney disease: toward integrated cardio-kidney-metabolic disease modification.
Official source
publication
PMID 42630988 — Comparative effects of semaglutide tirzepatide and retatrutide on renal fibrosis in UUO and aged mice.
Official source
publication
PMID 42385950 — Effects of retatrutide on learning and memory in streptozotocin-induced male diabetic rats.
Official source
publication
PMID 42559975 — Composition and Labelling Accuracy of Products Sold as Retatrutide in Australia.
Official source
publication
PMID 42683980 — Pharmacological management of obesity: Current landscape and emerging therapies.
Official source
publication
PMID 42649514 — Disease-modifying anti-diabetic drugs (DMADDs): bridging the SIMPLE approach to disease interception.
Official source
publication
PMID 42556625 — The role of GLP-1 and GIP receptor agonists in the treatment of diabetes and obesity.
Official source
publication
PMID 42673585 — Efficacy and Safety of Glucagon-like Peptide-1 Receptor Agonists and Co-agonists for Weight Loss Among Adults Without Diabetes : An Updated Systematic Review.
Official source

Questions

What the sources answer

What receptors does retatrutide target?

Retatrutide is a triple receptor agonist targeting the GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and glucagon receptors.

Who is the developer of retatrutide?

Retatrutide (development code LY3437943) is developed by Eli Lilly and Company.

Is retatrutide an approved drug?

No. Retatrutide is an investigational drug currently undergoing Phase 3 clinical trials and has not received regulatory approval.

What primary endpoints are evaluated in retatrutide Phase 3 trials?

Phase 3 trials evaluate endpoints including percent change in body weight, change in HbA1c, WOMAC pain scores for knee osteoarthritis, Apnea-Hypopnea Index (AHI) in sleep apnea, and time to composite cardiovascular and kidney events such as end-stage kidney disease (ESKD) or sustained eGFR decline.

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