Retatrutide Clinical Trial Outcomes

Retatrutide has been studied in people with type 2 diabetes.

In the published phase 2 type 2 diabetes trial, adults aged 18 to 75 years with type 2 diabetes, HbA1c of 7.0% to 10.5%, and BMI of 25 to 50 kg/m² were included. The study reported improvements in glycaemic control and reductions in body weight compared with placebo.

In the phase 3 TRANSCEND-T2D-1 trial, retatrutide was studied in people with type 2 diabetes inadequately controlled with diet and exercise alone. The primary endpoint was change in HbA1c at week 40. Lilly’s ADA 2026 summary reported HbA1c improvement of up to -1.9%, with up to 85% of participants reaching HbA1c of 6.5% or below.

Reuters separately reported that, across doses in the 40-week trial, HbA1c fell by 1.7% to 2.0%, compared with 0.8% in the placebo group.

However, retatrutide is not licensed in the UK for diabetes, obesity or any other condition.

Waist circumference was measured in retatrutide studies. In TRIUMPH-1, manufacturer-reported data showed the following changes at 80 weeks:

This means waist circumference changed in the trial population. It should not be described as proof that retatrutide specifically targets belly fat.

Cholesterol levels have been measured as cardiovascular risk markers in retatrutide clinical trials.

In the TRIUMPH-1 phase 3 trial, Lilly reported reductions in non-HDL cholesterol of up to 24.2% at 80 weeks in adults with obesity, or overweight with at least one weight-related comorbidity, without diabetes.

In the TRANSCEND-T2D-1 phase 3 trial, Lilly reported reductions in non-HDL cholesterol of up to 19.8% at 40 weeks in adults with type 2 diabetes inadequately controlled with diet and exercise alone.

Non-HDL cholesterol is a measure of all cholesterol carried by potentially harmful lipoproteins and is commonly used to assess cardiovascular risk.

These findings describe changes in cholesterol levels during clinical trials. They do not mean retatrutide is approved to treat high cholesterol, and they do not prove that retatrutide reduces the risk of heart attack, stroke or cardiovascular death. Retatrutide is not currently licensed in the UK.

Blood pressure has been measured as a cardiovascular risk marker in retatrutide clinical trials.

In the TRIUMPH-1 phase 3 trial, Lilly reported reductions in systolic blood pressure of up to 12.3 mmHg at 80 weeks. This trial studied adults with obesity, or overweight with at least one weight-related comorbidity, without diabetes.

In the TRANSCEND-T2D-1 phase 3 trial, Lilly reported reductions in systolic blood pressure of up to 6.4 mmHg at 40 weeks. This trial studied adults with type 2 diabetes inadequately controlled with diet and exercise alone.

These findings show changes in systolic blood pressure during clinical trials. They do not mean retatrutide is approved for high blood pressure, and they do not prove that retatrutide reduces the risk of heart attack, stroke or cardiovascular death. Retatrutide is not currently licensed in the UK.

Retatrutide has been studied in metabolic dysfunction-associated steatotic liver disease, also known as MASLD.

The MASLD substudy included 98 participants from the phase 2 obesity trial who had liver fat of at least 10%. Liver fat was measured using MRI-PDFF.

At 24 weeks, average relative liver fat change was:

At 24 weeks, normal liver fat, defined as less than 5%, was reached by:

At 48 weeks, relative liver fat reduction was 86.0% with retatrutide 12mg , compared with 4.6% with placebo.

These findings relate to liver fat measured in a clinical trial. Retatrutide is not approved in the UK as a treatment for MASLD, MASH or fatty liver disease.

Obstructive sleep apnoea is a condition where breathing repeatedly stops and starts during sleep. It is often measured using the apnoea-hypopnoea index, also called AHI. AHI measures the average number of breathing interruptions per hour of sleep.

In the TRIUMPH-1 phase 3 trial, a subgroup of 243 people with moderate-to-severe obstructive sleep apnoea was assessed.

At 80 weeks, Lilly reported that AHI reduced by up to 36.1 events per hour. This was equal to a 60.6% reduction from the average starting score of 58.6 events per hour.

These findings show changes in sleep apnoea severity scores during a clinical trial. Retatrutide is not licensed in the UK for obstructive sleep apnoea.

Knee osteoarthritis is a common cause of knee pain and stiffness, especially in people living with obesity or excess weight.

In the TRIUMPH-1 phase 3 trial, a subgroup of 574 people with knee osteoarthritis was assessed. Researchers measured knee pain using the WOMAC pain score, which is a standard questionnaire used in osteoarthritis studies.

At 80 weeks, Lilly reported that WOMAC pain scores reduced by up to 4.3 points, equal to a 73.1% reduction from the average starting score.

A separate phase 3 trial, TRIUMPH-4, looked more specifically at people with obesity or overweight and knee osteoarthritis. At 68 weeks, the reported WOMAC pain score changes were:

In the same trial, a reduction in knee pain score of at least 70% was reported in:

These results show changes in pain scores during clinical trials. They do not mean retatrutide is approved or recommended for knee osteoarthritis.

So far, the strongest published evidence comes from the phase 2 obesity trial and the MASLD liver fat substudy. Phase 3 results from TRIUMPH-1 and TRANSCEND-T2D-1 have also been reported, but some of these findings are currently manufacturer-reported. They should be interpreted with caution until full peer-reviewed publications are available.

Further clinical trials and regulatory review are needed before retatrutide can be submitted for approval and assessed for routine use. Retatrutide is not currently licensed in the UK. It should not be promoted, bought online or used outside an authorised clinical trial.