Retatrutide for Type 2 Diabetes
Retatrutide (LY3437943) is a triple hormone receptor agonist that activates GLP-1, GIP, and glucagon receptors. While most attention has focused on retatrutide's weight loss potential, its Phase 2 data in type 2 diabetes (T2D) is equally noteworthy — showing HbA1c reductions of up to -2.02 percentage points and weight loss of up to -16.94% in patients with T2D.
All three of retatrutide's receptor targets are directly relevant to glucose metabolism, making it a mechanistically comprehensive approach to diabetes management. Eli Lilly is running a dedicated Phase 3 program (TRANSCEND) specifically for the type 2 diabetes indication.
Retatrutide has not been approved by the FDA for type 2 diabetes or any other indication. All data on this page comes from clinical trials.
Phase 2 Trial in Type 2 Diabetes
Published in The Lancet in 2023 (Rosenstock et al., NCT04867785), this was a 36-week, randomized, double-blind, placebo-controlled and active-comparator-controlled trial.
Study design
- 281 participants with type 2 diabetes
- 36 weeks of treatment
- Doses tested: 0.5mg, 4mg (two titration schedules), 8mg (two titration schedules), 12mg
- Comparators: Placebo and dulaglutide 1.5mg (an existing GLP-1 drug, marketed as Trulicity)
- Conducted in the United States
HbA1c results at 36 weeks
| Group | HbA1c Change | Achieving HbA1c <5.7% |
|---|---|---|
| Placebo | -0.01% | — |
| Dulaglutide 1.5mg | -1.41% | — |
| Retatrutide 0.5mg | -0.43% | — |
| Retatrutide 4mg | -1.39% to -1.40% | — |
| Retatrutide 8mg | -1.88% to -1.99% | — |
| Retatrutide 12mg | -2.02% | 67% |
The -2.02% HbA1c reduction at the 12mg dose is substantial. For context, an HbA1c of 6.5% or higher is the diagnostic threshold for type 2 diabetes, and an HbA1c below 5.7% is considered normoglycemia (non-diabetic blood sugar levels). Two-thirds of participants on the highest dose achieved normoglycemia.
Weight loss results at 36 weeks
| Group | Weight Change |
|---|---|
| Placebo | -3.00% |
| Dulaglutide 1.5mg | -2.02% |
| Retatrutide 4mg | -7.92% to -10.37% |
| Retatrutide 8mg | -12.90% to -14.82% |
| Retatrutide 12mg | -16.94% |
The -16.94% weight loss in a T2D population over 36 weeks is particularly notable. Patients with type 2 diabetes typically achieve less weight loss on GLP-1 drugs than patients without diabetes. The fact that retatrutide produced this level of weight loss in a T2D population — and in only 36 weeks — suggests the triple mechanism may be particularly effective at overcoming the metabolic resistance to weight loss that characterizes T2D.
How the Three Receptors Address Diabetes
Each of retatrutide's three receptor targets plays a distinct role in glucose metabolism:
GLP-1 (Glucagon-Like Peptide-1)
- Stimulates glucose-dependent insulin secretion — the pancreas releases more insulin in response to meals, but not during fasting (reducing hypoglycemia risk)
- Suppresses glucagon secretion (from alpha cells) when blood sugar is high
- Slows gastric emptying, reducing post-meal blood sugar spikes
- Reduces appetite, contributing to weight loss
This is the mechanism behind semaglutide (Ozempic) and liraglutide (Victoza/Saxenda).
GIP (Glucose-Dependent Insulinotropic Polypeptide)
- Enhances insulin secretion in a glucose-dependent manner, complementing GLP-1
- May improve beta-cell function — the cells in the pancreas that produce insulin
- Contributes to weight loss through additional appetite and metabolic effects
GIP is the second target in tirzepatide (Mounjaro), which achieved HbA1c reductions of up to -2.07% in the SURPASS-1 trial.
Glucagon Receptor
This is the most conceptually complex target for diabetes. Glucagon raises blood sugar — the opposite of what you want in a diabetes drug. However:
- Glucagon promotes hepatic fatty acid oxidation and reduces liver fat, which improves hepatic insulin sensitivity — a core defect in T2D
- Glucagon increases energy expenditure, contributing to weight loss, which in turn improves insulin sensitivity
- The blood-sugar-raising effect of glucagon is counterbalanced by the strong insulin-stimulating effects of GLP-1 and GIP activation
The net result, as shown in the Phase 2 data, is that retatrutide's glucagon component does not cause hyperglycemia — the glucose-lowering effects of GLP-1 and GIP dominate, while glucagon contributes metabolic benefits that go beyond what GLP-1 alone can achieve.
How Retatrutide Compares to Existing Diabetes Drugs
| Drug | Mechanism | Max HbA1c Reduction | Max Weight Loss (T2D) | Trial |
|---|---|---|---|---|
| Retatrutide 12mg | GLP-1 + GIP + Glucagon | -2.02% | -16.94% (36 wks) | Phase 2 (Lancet) |
| Tirzepatide 15mg | GLP-1 + GIP | -2.07% | -12.9% (40 wks) | SURPASS-1 |
| Semaglutide 1mg | GLP-1 | -1.5% to -1.8% | -4.4% to -6.5% | SUSTAIN series |
| Dulaglutide 1.5mg | GLP-1 | -1.41% | -2.02% (36 wks) | Retatrutide Phase 2 comparator |
Cross-trial comparisons have significant limitations. Different trials enrolled different patient populations, had different baseline HbA1c levels, and ran for different durations. Only head-to-head trials can provide definitive comparisons.
Retatrutide's HbA1c reduction is comparable to tirzepatide's, while its weight loss in the T2D population substantially exceeds what tirzepatide achieved in SURPASS-1. The weight loss advantage may prove to be clinically meaningful, as greater weight loss in T2D patients is associated with higher rates of diabetes remission and reduced need for diabetes medications.
The TRANSCEND Phase 3 Program
Eli Lilly is running the TRANSCEND Phase 3 program to evaluate retatrutide specifically for type 2 diabetes. This is a separate program from TRIUMPH (which focuses on obesity).
What we know
- Multiple TRANSCEND trials are underway
- The program is expected to produce readouts in 2026
- Results will support a potential T2D-specific regulatory filing, likely separate from the obesity indication filing
Why a separate program matters
The FDA evaluates drugs by indication. A drug approved for obesity does not automatically have a diabetes indication — it requires separate clinical evidence. By running the TRANSCEND program in parallel with TRIUMPH, Lilly is positioning retatrutide for potential approval in both obesity and T2D, possibly with filings close in time.
What This Means for People with Type 2 Diabetes
Potential advantages of retatrutide over current options
- Greater weight loss in T2D patients — weight management is critical for diabetes control, and retatrutide produced more weight loss in a T2D population than any other incretin drug in published trials
- Comprehensive metabolic effects — the triple mechanism addresses insulin secretion (GLP-1, GIP), hepatic insulin resistance (glucagon), and energy expenditure (glucagon) simultaneously
- Potential liver benefits — many people with T2D also have MASLD, and retatrutide's glucagon component has shown strong liver fat reduction (see Retatrutide and Fatty Liver Disease)
Important caveats
- Phase 2 data only — the T2D trial enrolled 281 participants over 36 weeks, which is a relatively small study of moderate duration
- Phase 3 TRANSCEND results have not yet been reported
- Long-term safety in the T2D population is not yet characterized
- Retatrutide is not available by prescription — FDA approval is potentially in 2027
Frequently Asked Questions
Is retatrutide approved for type 2 diabetes?
No. Retatrutide is not approved for any indication. The Phase 3 TRANSCEND program is underway, with results expected in 2026. If the data supports it, a regulatory filing for T2D could follow, with potential approval in 2027 or later.
How does retatrutide compare to Ozempic for diabetes?
In the Phase 2 trial, retatrutide 12mg produced an HbA1c reduction of -2.02% (vs. -0.01% for placebo) over 36 weeks, and weight loss of -16.94%. Semaglutide (Ozempic) at 1mg typically produces HbA1c reductions of -1.5% to -1.8% and weight loss of -4.4% to -6.5% in T2D populations. Retatrutide appears to offer greater efficacy, but this comparison is indirect — no head-to-head trial has been conducted.
Would retatrutide replace insulin?
For some patients with type 2 diabetes, potentially. The Phase 2 trial showed that 67% of participants on the 12mg dose achieved HbA1c below 5.7% (normoglycemia). Patients achieving that level of glucose control may not need insulin or other diabetes medications. However, this depends on individual disease severity, beta-cell function, and other factors. Retatrutide would not replace insulin for people with type 1 diabetes, as it is a fundamentally different condition.
Can people with type 2 diabetes access retatrutide now?
Only through clinical trials. The TRANSCEND Phase 3 program is specifically enrolling T2D patients. Search for trials at ClinicalTrials.gov or LillyTrialGuide.com.
Sources
- Rosenstock, J., et al. (2023). Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-comparator-controlled, parallel-group, phase 2 trial conducted in the USA. The Lancet. DOI: 10.1016/S0140-6736(23)01053-X
- Jastreboff, A.M., et al. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. DOI: 10.1056/NEJMoa2301972
- ClinicalTrials.gov: NCT04867785
Medical Disclaimer
The content on glp3.wiki is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Retatrutide is an investigational drug that has not been approved by the U.S. Food and Drug Administration (FDA) or any other regulatory agency.
If you have type 2 diabetes, do not change, stop, or adjust your current medications based on information about an unapproved drug. Work with your endocrinologist or primary care physician to manage your diabetes using currently approved treatments.
This site is not affiliated with Eli Lilly and Company or any pharmaceutical manufacturer.
Sources
- Phase 2 T2D trial (Lancet)
The Lancet
- Phase 2 T2D trial
ClinicalTrials.gov
Related reading
What Is Retatrutide (GLP-3)?
The world's first triple agonist weight loss drug — how it works, what the trials show, and why people call it GLP-3.
Retatrutide Clinical Trials & Results
Living tracker of all retatrutide trials — Phase 1 through the TRIUMPH Phase 3 program.
Retatrutide and Fatty Liver Disease (MASLD/MASH)
Retatrutide produced up to 82.4% liver fat reduction in Phase 2 — among the strongest results for any drug in development for MASLD/MASH.