This research study is testing whether a weekly medication called tirzepatide can help adults with type 1 diabetes use their insulin pump more easily, specifically by reducing or eliminating the need to count carbohydrates at meals.
People with type 1 diabetes must take insulin for life, and even with advanced insulin pumps and continuous glucose monitors, many still struggle to keep blood sugar within the target range. One of the biggest challenges is carbohydrate counting, which requires estimating the amount of carbohydrates in every meal to give the correct insulin dose.
Tirzepatide is a medication currently approved for type 2 diabetes and weight management. Early research suggests it may also help people with type 1 diabetes by lowering appetite, slowing digestion, reducing insulin needs, and smoothing after-meal blood sugar rises.
This study will include 105 adults with type 1 diabetes at centers in Canada and Switzerland. Everyone will use the Tandem Control-IQ insulin pump with a Dexcom G7 continuous glucose monitor. Participants are randomly assigned to one of two groups:
Tirzepatide group:
Participants receive weekly tirzepatide injections. After the dose is gradually increased over 12 weeks, they will eventually try using their insulin pump without entering carbohydrate amounts at meals.
Control group:
Participants continue their usual therapy and keep counting carbohydrates for their mealtime insulin doses.
The main goal of the study is to learn whether people taking tirzepatide can safely maintain good blood sugar control without counting carbs, compared with standard care. All participants will attend several clinic visits and share their glucose, insulin, and health data throughout the 32-week trial. Some centers will also conduct heart/fitness, or body-composition tests.
As with any medication, tirzepatide may cause side effects such as nausea, vomiting, diarrhea, or decreased appetite. Rare but serious risks like gallbladder disease or pancreatitis are also monitored. Pregnancy must be avoided during the trial.
Overall, this study aims to understand whether adding tirzepatide to automated insulin delivery can simplify diabetes management, reduce burden, and maintain safe and effective glucose control for adults living with type 1 diabetes.
Age ≥ 18 years.
Clinical diagnosis of type 1 diabetes for ≥ 1 year, per investigator judgment (confirmatory C-peptide and autoantibodies not required).
A BMI ≥ 27 kg/m2.
HbA1c > 6.5%, and < 12%.
Use of GLP1-RAs within the last four weeks.
Use of antihyperglycemic agents other than insulin or metformin within the last 2 weeks.
Planned or ongoing pregnancy.
Breastfeeding.
Parallel
Tirzepatide
DrugTirzepatide, administered as a once-weekly subcutaneous injection, initiated at 2.5 mg and escalated in 2.5-mg increments every 4 weeks to a target of 10 mg or the maximally tolerated dose, used as an adjunct therapy in adults with type 1 diabetes using the Tandem Control-IQ automated insulin delivery system.
Tandem Control-IQ Automated Insulin Delivery System (with Dexcom G7 CGM)
DeviceThis intervention uses the Tandem t:slim X2 insulin pump with the Control-IQ automated insulin delivery algorithm, integrated with the Dexcom G7 continuous glucose monitor. The system adjusts basal insulin and delivers automated correction boluses based on real-time glucose values. All participants receive standardized training and use this system for the full 32-week study. Rapid-acting insulin compatible with Control-IQ is required. This intervention is distinguished by its use under two different operational strategies: standard carbohydrate counting in the control arm and complete omission of meal announcements during the final 6 weeks in the tirzepatide arm.
Carbohydrate Counting
BehavioralParticipants enter the estimated carbohydrate amount for every meal and snack into the Tandem Control-IQ insulin pump to calculate and deliver prandial insulin boluses. This reflects standard use of hybrid closed-loop systems. The procedure is maintained for the entire 32-week study in the control arm and during Weeks 1-26 in the tirzepatide arm.
No Meal Announcement
BehavioralParticipants do not enter carbohydrate amounts or announce meals to the Tandem Control-IQ system. The pump operates without user-initiated prandial boluses, relying solely on automated basal adjustments and automated correction boluses. This intervention is implemented only in the tirzepatide arm during Weeks 27-32.
Daytime Time-in-Range
The primary outcome is the percentage of daytime hours (06:00-24:00) during which participants' glucose levels, measured by the Dexcom G7 continuous glucose monitor, fall within the target range of 3.9-10.0 mmol/L.
Weight
Change in body weight to assess the effects of tirzepatide on body composition. Weight is measured in kilograms.
Height
Change in height to assess the effects of tirzepatide on body composition. Height is measured in meters.
Body Mass Index
Change in BMI to assess the effects of tirzepatide on body composition. BMI is measured in kilograms per square meter.
Waist circumference
Change in waist circumference to assess the effects of tirzepatide on body composition. Waist circumference is measured in centimetres.
Severe hypoglycemia
Episode requiring the assistance of another person, due to altered consciousness, to administer carbohydrates, glucagon, or other resuscitative actions.
Diabetic Ketoacidosis
Clinical episode characterized by hyperglycemia/euglycemia, ketonemia or ketonuria, metabolic acidosis, and associated symptoms such as nausea, vomiting, abdominal pain, rapid breathing, or altered consciousness. Events requiring emergency evaluation, intravenous fluids, or hospital treatment will be recorded as DKA. All episodes will be assessed for severity, timing, precipitating factors, and their relationship to study interventions, including tirzepatide use and automated insulin delivery performance.
Gastrointestinal and related side effects
Nausea Vomiting Abdominal pain Diarrhea Constipation Liver profile changes Gallbladder disease Acute pancreatitis Other related side effects
Click on the lead sponsor to view all of their trials.
McGill University Health Centre/Research Institute of the McGill University Health Centre
Lead sponsor
Breakthrough T1D
Collaborator
Institut de Recherches Cliniques de Montreal
Collaborator
Insel Gruppe AG, University Hospital Bern
Collaborator
