Retatrutide for Type 2 Diabetes: TRANSCEND Trial Data

Overview

Type 2 diabetes is a central target in retatrutide’s clinical development. As a triple agonist of GIP, GLP-1 and glucagon receptors, retatrutide works on several pathways that matter for blood sugar control. GLP-1 and GIP receptor activation trigger insulin release when glucose is high and suppress glucagon after meals. Its wider metabolic effects, including large weight loss and better insulin sensitivity, act on the root causes of type 2 diabetes.

Eli Lilly first reported topline results from TRANSCEND-T2D-1, the first Phase 3 trial of retatrutide specifically in adults with type 2 diabetes, in March 2026. The full peer-reviewed results were published in The Lancet on June 6, 2026, and presented the same day at the American Diabetes Association (ADA) 2026 Scientific Sessions in New Orleans. These data confirm and extend the blood sugar results from the Phase 2 trial published by Rosenstock et al. in The Lancet (2023). The figures below are the final published data, which differ slightly from the earlier press-release estimates.

TRANSCEND-T2D-1: Phase 3 Results

Trial Design

TRANSCEND-T2D-1 was a randomized, double-blind, placebo-controlled Phase 3 trial of retatrutide in adults with type 2 diabetes. Key details:

• Participants: 537, across 48 sites in the United States, Mexico, and India
• Baseline HbA1c: 7.9% (mean)
• Duration: 40 weeks
• Doses: 4 mg, 9 mg, and 12 mg (with dose escalation) vs. placebo
• Primary endpoint: Change in HbA1c from baseline
• Source: Bajaj et al., published in The Lancet, June 6, 2026 (“Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise”); presented at ADA 2026.

A1C Reduction

Every active dose lowered HbA1c significantly more than placebo, and the effect grew with dose: 12 mg gave the largest drop (-1.94 points). Between 82% and 89% of participants across the retatrutide doses reached an HbA1c below 7.0% (the standard treatment target), and 75-83% reached the tighter ≤6.5% threshold. (Earlier press-release estimates had suggested a plateau at 9 mg; the peer-reviewed Lancet data instead show a clean dose-response.)

Weight Loss

Weight loss in people with type 2 diabetes was large but smaller than in the obesity population without diabetes (TRIUMPH-4 reported -28.7% at 12 mg over 68 weeks). This matches a well-known pattern across incretin-based drugs: people with type 2 diabetes usually lose less weight than people without diabetes on the same dose. Reasons include differences in baseline metabolism, other diabetes medications, and the shorter trial (40 weeks vs. 68 weeks).

Weight loss had not leveled off at 40 weeks, which suggests longer treatment would bring more weight loss.

Safety and Tolerability

Gastrointestinal side effects were the most common, as with other GLP-1 drugs:

Dysesthesia was reported in 2.3-4.5% of participants on retatrutide in TRANSCEND-T2D-1. That is well below the 8.8-20.9% seen in TRIUMPH-4’s obesity population. It is not yet clear whether the gap reflects the shorter trial, the diabetes population or chance.

Discontinuation due to adverse events was 2.2-5.1% across retatrutide doses, much lower than the 12.2-18.2% in TRIUMPH-4. Better tolerability in people with type 2 diabetes is an important finding that may shape prescribing decisions and label language.

Key Takeaways from TRANSCEND-T2D-1

1. Retatrutide gave clinically meaningful A1C reductions at every dose, with a clean dose-response. 12 mg gave the largest drop (-1.94 points from a 7.9% baseline).
2. Between 82% and 89% of participants reached HbA1c below 7.0%, and 75-83% reached the tighter ≤6.5% target.
3. Weight loss was large (-15.3% at 12 mg) and had not leveled off at 40 weeks.
4. No severe hypoglycemia occurred in any arm, which is reassuring given retatrutide’s glucagon-receptor activity.
5. The safety profile was better than in the obesity population, with less dysesthesia and fewer people stopping treatment.
6. These are peer-reviewed data, published in The Lancet (June 6, 2026) and presented at ADA 2026, not preliminary press-release figures.

Phase 2 Type 2 Diabetes Data

The Phase 2 trial in type 2 diabetes, published by Rosenstock et al. in The Lancet (2023), gave the first evidence of how well retatrutide controls blood sugar.

Study Design

• Participants: 281 adults with type 2 diabetes
• Duration: 36 weeks (with a 4-week follow-up)
• Doses: 0.5 mg, 4 mg (two regimens), 8 mg (two regimens), 12 mg vs. dulaglutide 1.5 mg and placebo
• Population: Inadequately controlled type 2 diabetes (HbA1c 7.0-10.5%)

A1C Results at 24 Weeks (Primary Endpoint)

At 12 mg, A1C fell by 2.02 points at 24 weeks, and the results held at 36 weeks. The 8 mg (2 mg start) and 12 mg groups lowered A1C significantly more than dulaglutide. The Phase 3 TRANSCEND-T2D-1 results (-1.94% at 12 mg, 40 weeks) fit with this, though they are slightly lower, as you would expect in a larger, more diverse Phase 3 population.

Cross-Trial Comparison with Other Therapies

The first head-to-head trial, TRANSCEND-T2D-2 against semaglutide 2 mg (Ozempic), reported topline results on October 28, 2026: in 1,298 adults with type 2 diabetes, retatrutide 12 mg lowered A1C by 2.2 points versus 1.8 with semaglutide at 80 weeks, and body weight by 20.9% versus 9.4% (efficacy estimand; Lilly’s announcement, not yet peer reviewed). See TRANSCEND-T2D-2. For other medicines, only cross-trial comparisons are possible, with all the limits that brings:

Read these comparisons with caution. Trial populations, baseline characteristics, other medications and endpoint definitions differ across programs. TRANSCEND-T2D-2 is the only direct comparison so far, and only against semaglutide.

Retatrutide’s blood sugar effect looks broadly similar to tirzepatide’s, with numerically more weight loss. Only a direct comparison can show whether triple agonism beats dual agonism in a clinically meaningful way for blood sugar control.

The TRANSCEND Clinical Program

The TRANSCEND program includes several Phase 3 trials of retatrutide in type 2 diabetes and related conditions:

TRANSCEND-T2D-2 is especially interesting as the first head-to-head comparison of retatrutide against an established GLP-1 receptor agonist in people with diabetes. Its topline results, reported October 28, 2026, showed that at 80 weeks retatrutide 12 mg lowered A1C by 2.2 points vs 1.8 with semaglutide 2 mg (Ozempic), and body weight by 20.9% vs 9.4%. TRANSCEND-T2D-3 targets a group with high unmet need: kidney impairment limits treatment options and is a common complication of type 2 diabetes.

Mechanism of Action in Diabetes

Retatrutide’s triple receptor profile improves blood sugar control through several pathways that work together:

• GLP-1 receptor agonism: Triggers insulin release when glucose is high, suppresses unneeded glucagon release after meals, slows stomach emptying and reduces appetite. This is the familiar mechanism shared with semaglutide, liraglutide and other GLP-1 receptor agonists.
• GIP receptor agonism: Strengthens the incretin effect and may improve beta-cell function and insulin sensitivity. Tirzepatide shares this mechanism.
• Glucagon receptor agonism: Raises liver glucose output in the short term, but with ongoing treatment alongside GLP-1/GIP agonism the net effect is better overall blood sugar control. The glucagon component also raises energy expenditure, adding to the large weight loss that in turn improves insulin sensitivity and blood sugar.

Direct incretin-driven insulin release, eating less because of reduced appetite, and better insulin sensitivity from weight loss together likely explain the large A1C reductions seen across the program.

Frequently Asked Questions

How does retatrutide compare to Mounjaro (tirzepatide) for diabetes?

There are no head-to-head data against tirzepatide. In cross-trial comparisons, tirzepatide has given slightly larger A1C reductions (up to -2.4% in the SURPASS program), while retatrutide gives more weight loss (-15.3% vs. ~12.9% at comparable doses and durations). Eli Lilly develops both. The only direct comparison so far is TRANSCEND-T2D-2, against semaglutide, not tirzepatide; no tirzepatide head-to-head in type 2 diabetes is currently planned.

Can retatrutide achieve diabetes remission?

The TRANSCEND-T2D-1 press release did not report diabetes remission rates (usually defined as A1C < 6.5% without medication). In the Phase 2 trial, 53-86% of participants on retatrutide 4 mg or higher reached an A1C of 7.0% or less at 24 weeks, against 22% on placebo. Given how far A1C and weight fell, some participants likely reached remission-range A1C levels, but remission was not reported as such. In the published Lancet data, 75-83% of participants reached HbA1c ≤6.5% at 40 weeks while still taking the study drug, which is not the same as remission.

Why is the A1C reduction similar at 9 mg and 12 mg?

The March 2026 topline release put the two doses at about -2.0 points (9 mg) and -1.9 points (12 mg), which suggested a plateau. The published Lancet data show -1.86 points at 9 mg and -1.94 at 12 mg: the doses fall in the expected order but differ only a little, so most of the blood sugar effect is already there at 9 mg. Weight loss rose more clearly with dose (-13.9% at 9 mg vs. -15.3% at 12 mg). In TRIUMPH-2 (obesity with type 2 diabetes) the A1C effect also plateaued at 9 mg (-1.6 vs -1.5 points at 12 mg).

When will retatrutide be approved for type 2 diabetes?

Retatrutide is not approved for any use. Lilly says it plans to file for approval no later than the first quarter of 2027. When it announced the TRIUMPH-2 and TRIUMPH-3 results in July 2026, it named obesity, knee osteoarthritis pain and obstructive sleep apnea as the uses its data package supports; it did not mention type 2 diabetes. The FDA ruled on October 2, 2026 that retatrutide is a drug, so the application must be a New Drug Application (NDA); Lilly is challenging the FDA ruling in court and has not said which pathway it will use. Lilly has not said when it will seek approval for type 2 diabetes.

Why was weight loss lower in the diabetes population?

The -15.3% weight loss at 12 mg in TRANSCEND-T2D-1 (40 weeks) is lower than the -28.7% in TRIUMPH-4 (68 weeks). Two things explain the gap: shorter treatment (40 vs. 68 weeks, with weight loss still going) and the well-documented smaller weight loss in people with type 2 diabetes. Diabetes medicines such as insulin and sulfonylureas can cause weight gain, insulin resistance changes energy metabolism, and the metabolic state in type 2 diabetes seems to resist weight loss compared with people without diabetes. The same pattern holds across the GLP-1 agonist class.

What side effects were most common in the diabetes trial?

Gut side effects led the list: nausea (16.4-26.5%), diarrhea (18.7-26.3%) and vomiting (15.0-17.6%). Dysesthesia occurred in 2.3-4.5% of participants, lower than the 8.8-20.9% in the obesity population (TRIUMPH-4). Discontinuation due to adverse events was 2.2-5.1%, similar to other injectable incretins and much lower than TRIUMPH-4’s 12.2-18.2%. These data suggest the drug may be better tolerated in people with type 2 diabetes, though the shorter trial may also play a part.

Summary

The TRANSCEND-T2D-1 Phase 3 trial confirms that retatrutide works in type 2 diabetes, with A1C reductions of up to -1.94 points and weight loss of -15.3% at 40 weeks. The safety profile was better than in the obesity population, with less dysesthesia and far fewer people stopping treatment. These data suggest retatrutide could become a significant new option for type 2 diabetes. The first direct comparison, TRANSCEND-T2D-2 against semaglutide 2 mg, reported topline results on October 28, 2026 (A1C -2.2 points on both retatrutide doses vs -1.8; not yet peer reviewed). The full TRANSCEND-T2D-1 data were presented at ADA 2026 and published in The Lancet on June 6, 2026.