Add-on semaglutide improves glycaemic control, weight loss in adults with T1D, obesity

The addition of once-weekly semaglutide to an automated insulin delivery (AID) system leads to significantly improved time in range (TIR) and reduced body weight in adults with type 1 diabetes (T1D) and obesity compared with AID alone, according to the ADJUST-T1D* trial presented at ADA 2025.

“AID therapy has become the standard of care in T1D; however, only 30 percent of adults with T1D can achieve HbA_1c <7 percent in the US,” said Dr Halis Kaan Akturk from the Barbara Davis Center for Diabetes at the University of Colorado, Colorado, US, one of the authors of the study.

“Glucagon-like peptide-1 receptor agonists, [particularly semaglutide], may have the potential to be used as an adjunctive therapy in T1D to improve glycaemic control and decrease weight, insulin dose, and cardiorenal risk,” he added.

This investigator-initiated, multicentre, double-blind, placebo-controlled study evaluated 72 adults (aged 18–65 years) with T1D and obesity (BMI 30–34.9 kg/m²). Participants were randomized in a 1:1 ratio to receive either once-weekly semaglutide 1 mg, the available dose at the time of the study, or a placebo in addition to their AID system.

By week 26, significantly more semaglutide-treated patients achieved the primary composite outcome of TIR (70–80 mg/dL) of >70 percent, time below range (<70 mg/dL) of <4 percent, and weight reduction of ≥5 percent than the placebo-treated patients (36 percent vs 0 percent; p<0.001). [ADA 2025, abstract CT-SY29-1]

Mean HbA_1c level decreased from 7.8 percent at baseline to 7.1 percent at week 26 in the semaglutide group and from 7.7 percent to 7.4 percent in the placebo group, resulting in an adjusted group difference of -0.3 percentage points.

Based on the CGM metrics, the percentage of time in tight range and TIR improved by 6.9 percent and 8.8 percent, respectively, with semaglutide compared with placebo.

Treatment with semaglutide vs placebo was also associated with a reduction in body weight (adjusted group difference of -8.8 kg) and BMI (adjusted group difference of -3.1 kg/m²) from baseline to week 26.

The insulin dose was reduced by 30 percent between the semaglutide and placebo groups.

In terms of safety, gastrointestinal-related adverse events occurred more frequently in the semaglutide arm than the placebo arm (52.8 percent vs 25 percent). Although this finding was similar to that of the semaglutide trials in individuals with type 2 diabetes and obesity, according to Dr Viral Shah from Indiana University School of Medicine in Indianapolis, Indiana, US, who presented the study results.

“Overall, in people with T1D and obesity, semaglutide treatment significantly improved achievement of the primary composite outcome compared with AID use alone,” Shah concluded. “Regulatory trials for its use in T1D are highly encouraged.”

He added treatment with semaglutide 1 mg/week was safe and well tolerated.