Retatrutide Cuts HbA1c, Promotes Weight Loss in Type 2 Diabetes Trial

A once-weekly injectable medication, retatrutide, is showing promising results for adults with type 2 diabetes, offering both significant reductions in HbA1c levels and substantial weight loss, according to topline data from the phase 3 TRANSCEND-T2D-1 trial. The findings, released March 19, 2026, suggest a potential new approach to managing the condition, often complicated by the challenges of achieving both glycemic control and weight management.

Retatrutide’s Triple Action

Retatrutide is a novel triple agonist, meaning it targets three key hormones involved in regulating blood sugar and appetite: GIP, GLP-1, and glucagon. Previous research has indicated its potential not only for diabetes and obesity but similarly for a range of other conditions. The TRANSCEND-T2D-1 trial involved 537 adults diagnosed with type 2 diabetes who weren’t adequately controlled with diet and exercise alone. Participants had an HbA1c between 7% and 9.5% at the study’s start, a body mass index (BMI) of 23 kg/m² or higher, and had not recently used diabetes medication or insulin (with exceptions for gestational diabetes).

Key Findings at 40 Weeks

The study assessed participants receiving either 4 mg, 9 mg, or 12 mg of retatrutide weekly, compared to a placebo group, over a 40-week period. The primary outcome measured was the change in HbA1c from baseline. Results showed that all three retatrutide dosages led to greater HbA1c reductions than placebo, with decreases of 1.7 percentage points (4 mg), and 1.9 percentage points (9 mg and 12 mg) compared to a 0.8 percentage point reduction in the placebo group.

Alongside improved glycemic control, retatrutide demonstrated significant weight loss. Participants receiving 4 mg, 9 mg, and 12 mg retatrutide lost 11.5%, 13.9%, and 15.3% of their body weight, respectively, compared to a 2.6% weight loss in the placebo group. These findings suggest a substantial impact on both metabolic health and body composition.

Cardiovascular Markers and Safety

Beyond HbA1c and weight, the study also indicated improvements in cardiovascular risk factors. Adults treated with retatrutide experienced clinically meaningful changes in non-HDL cholesterol, triglycerides, and systolic blood pressure, according to a press release from Eli Lilly.

The most commonly reported adverse events were nausea, diarrhea, and vomiting, occurring more frequently in the retatrutide groups than in the placebo group. These gastrointestinal side effects generally occurred during the initial dose escalation phase. A smaller percentage of participants reported dysesthesia (abnormal sensation) – 4.5% in the 4 mg group, 2.3% in the 9 mg group, and 4.4% in the 12 mg group, compared to none in the placebo group. Most dysesthesia events were mild and resolved during treatment. Discontinuation rates due to adverse events were relatively low, ranging from 2.2% to 5.1% across the retatrutide dosage groups.

Understanding HbA1c and Weight Loss in Type 2 Diabetes

HbA1c is a measure of average blood sugar levels over the past 2-3 months. A lower HbA1c indicates better blood sugar control, reducing the risk of long-term complications associated with diabetes, such as heart disease, kidney disease, and nerve damage. For context, the American Diabetes Association generally recommends an HbA1c target of below 7% for most adults with diabetes.

Obesity is a common comorbidity of type 2 diabetes, and often exacerbates insulin resistance, making blood sugar control more difficult. Weight loss can improve insulin sensitivity, leading to better glycemic control and reducing the require for medication. The simultaneous impact of retatrutide on both HbA1c and weight is particularly noteworthy, as achieving both goals can be challenging with existing therapies.

Study Design and Limitations

The TRANSCEND-T2D-1 trial was a randomized, placebo-controlled phase 3 study, considered the gold standard for evaluating the efficacy and safety of new medications. However, it’s important to note that the topline results released represent a summary of the findings. A full analysis of the data, including detailed information on secondary endpoints and subgroup analyses, will be presented at the American Diabetes Association Scientific Sessions in June and published in a peer-reviewed journal.

As with any clinical trial, there are potential limitations. The study population was specifically selected based on certain criteria (HbA1c range, BMI, medication history), which may limit the generalizability of the findings to all individuals with type 2 diabetes. The study duration of 40 weeks provides information on short-to-medium term effects, but longer-term studies are needed to assess the durability of the benefits and potential long-term safety concerns.

What’s Next for Retatrutide?

Eli Lilly plans to present the complete results from TRANSCEND-T2D-1 at the American Diabetes Association Scientific Sessions and publish them in a peer-reviewed journal. Additional topline results from other clinical trials evaluating retatrutide for obesity and other conditions are expected over the next year. These data will be crucial for informing regulatory submissions and potential market approval.

Regulatory Review and Potential Availability: Following the presentation of full trial data, Eli Lilly will likely submit a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) and similar applications to regulatory agencies in other countries. The review process typically takes several months to a year or more. If approved, retatrutide could become a new treatment option for adults with type 2 diabetes, potentially offering a more comprehensive approach to managing the condition.

Kenneth Custer, PhD, executive vice president and president of Lilly Cardiometabolic Health, emphasized the potential of retatrutide to address the challenges of achieving both HbA1c control and weight loss in individuals with type 2 diabetes. “For many people with type 2 diabetes, it is a struggle to achieve both HbA1c control and weight loss, since obesity has historically been harder to treat for those with type 2 diabetes,” Custer said in a press release. “With triple agonist retatrutide, we set out to create a molecule that could help patients achieve substantial HbA1c reduction and weight loss. These results support the remarkable potential of this novel molecule for people living with type 2 diabetes, with up to 2 [percentage point] HbA1c improvement and nearly 17% weight loss in 40 weeks of treatment.”

You can find more information about retatrutide and the TRANSCEND-T2D-1 trial on the Eli Lilly investor relations website. For general information about type 2 diabetes, visit the Centers for Disease Control and Prevention (CDC) or the American Diabetes Association.