A Clinical Trial Using Tirzepatide to Help Adults With Type 1 Diabetes Automatically Control Their Blood Sugar

Phase 3RecruitingNCT07284511

McGill University Health Centre/Research Institute of the McGill University Health Centre105 enrolled

Overview

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.

Current diabetes technology, including hybrid automated insulin delivery systems like the Tandem Control-IQ paired with the Dexcom G7 continuous glucose monitor, improves glucose control but still relies heavily on patients entering carbohydrate amounts before eating, a task that is difficult, error-prone, and often stressful. Tirzepatide, which is approved for type 2 diabetes and weight management, works by slowing digestion, lowering appetite, reducing insulin requirements, and improving after-meal glucose spikes, and early evidence suggests it may offer similar benefits in type 1 diabetes. This study is designed to determine whether adding once-weekly tirzepatide injections to a commercially available automated insulin delivery system can make diabetes management easier for adults with type 1, particularly by reducing or eliminating the need to count carbohydrates at meals. In this 32-week trial, 105 adults will be randomly assigned to receive tirzepatide or no tirzepatide while all participants use the Control-IQ system. Those receiving tirzepatide will gradually increase their dose over 12 weeks, continue counting carbohydrates until week 26, and then stop announcing meals entirely for the final 6 weeks, while the control group will count carbohydrates throughout. Across the study, participants will attend scheduled clinic visits, complete remote follow-ups, undergo laboratory tests, and, depending on the site, may complete heart function tests, body-composition scans, fitness testing, or gastric emptying assessments. Researchers will compare glucose control, insulin needs, weight, metabolic markers, meal patterns, and patient-reported outcomes between groups, with the primary goal of determining whether glucose management without carbohydrate counting is not worse than (non-inferior to) standard carbohydrate counting. The study also closely monitors safety, as tirzepatide can cause nausea, vomiting, diarrhea, decreased appetite, and rare complications such as gallbladder disease or pancreatitis. Overall, this research aims to learn whether combining tirzepatide with automated insulin delivery can safely simplify diabetes management, reduce treatment burden, and improve metabolic outcomes for adults living with type 1 diabetes.

Interventions

TirzepatideDRUG

Tirzepatide, 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)DEVICE

This 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 CountingBEHAVIORAL

Participants 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 AnnouncementBEHAVIORAL

Participants 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.

Eligibility

Sex: ALLMin age: 18 Years

Medical Language ↔ Plain English

Inclusion Criteria: * 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%. * Current therapy: multiple daily injections or insulin pump. * Willingness to use Tandem Control IQ insulin pump system with the use of rapid or ultra rapid-acting insulins compatible with Tandem Control-IQ pump (e.g. Fiasp is not compatible) * Active carbohydrate counting for prandial insulin dosing. * Individuals of childbearing potential must be using or agree to use an effective birth-control method. Childbearing potential refers to participants of the female sex post-menarche who have not reached menopause and who do not have a medical condition causing sterility (e.g., hysterectomy). Post-menopausal state refers to the absence of menses for 12 months without any alternative cause. Exclusion Criteria: * 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. * Severe hypoglycemia requiring hospitalization in the past 2 months. Severe hypoglycemia is defined as requiring the assistance of another person, due to altered consciousness, to administer carbohydrates, glucagon, or other resuscitative actions. * Diabetic ketoacidosis within the last 2 months. * History of acute or chronic pancreatitis. * Personal or family history of medullary thyroid cancer or multiple endocrine neoplasia type 2. * Severe renal impairment with eGFR \<30 mL/min/1.73 m2 (CKD-EPI), measured within the last four months. * Clinically significant proliferative diabetic retinopathy or gastroparesis, as per the judgment of the investigator. * Current or ≤ 1 month use of supraphysiological doses of oral or intravenous glucocorticoids. * History of bariatric surgery within the last 6 months. * Medical or psychiatric illness likely to interfere with participation (e.g. cirrhosis, active cancer, decompensated schizophrenia), per investigator judgment. * Inability or unwillingness to comply with safe diabetes management practices, in the view of the investigator. * Any safety concern that, in the investigator's judgment, precludes participation.

Outcomes

Primary Outcomes

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.

Time frame: During the final 6 weeks of the study

Secondary Outcomes

Weight

Change in body weight to assess the effects of tirzepatide on body composition. Weight is measured in kilograms.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study

Height

Change in height to assess the effects of tirzepatide on body composition. Height is measured in meters.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study.

Body Mass Index

Change in BMI to assess the effects of tirzepatide on body composition. BMI is measured in kilograms per square meter.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study

Waist circumference

Change in waist circumference to assess the effects of tirzepatide on body composition. Waist circumference is measured in centimetres.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study

Waist-to-Hip Ratio

Change in waist-to-hip ratio to assess the effects of tirzepatide on body composition. Waist-to-Hip Ratio is measured by dividing the waist circumference by the hip circumference. It is unitless.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study.

Systolic Blood Pressure

Change in systolic blood pressure to evaluate the cardiovascular effects of tirzepatide. Systolic blood pressure is measured in millimetres of mercury.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study.

Diastolic Blood Pressure

Change in diastolic blood pressure to evaluate the cardiovascular effects of tirzepatide. Diastolic blood pressure is measured in millimetres of mercury.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study.

Resting Heart Rate

Change in resting heart rate to assess the cardiovascular effects of tirzepatide. Resting heart rate is measured in beats per minute.

Time frame: At enrollment, Week 8, Week 16, Week 24, and Week 32, At Week 8 and Week 16 post-study.

Insulin-related measures

Daily insulin requirements, including basal insulin, bolus insulin, and total insulin units per day, recorded through the insulin pump. Total insulin use normalized to body weight (units/kg/day) to assess treatment-related changes in insulin sensitivity. Carbohydrate amounts entered for bolus dosing (control arm and Weeks 1-26 of tirzepatide arm).

Time frame: Continuously from randomization through Week 32, with primary analysis focused on Weeks 27-32, At Week 8 and Week 16 post-study.

Glucose outcomes

Percentage of CGM readings within 3.9-10.0 mmol/L, 3.9-7.8 mmol/L, \<3.9 mmol/L, \<3.0 mmol/L, \>10.0 mmol/L, and \>13.9 mmol/L, as well as mean glucose, glucose standard deviation, and glucose coefficient of variation.

Time frame: Continuously collected from randomization through Week 32, with key comparisons during Weeks 23-26 and Weeks 27-32, At Week 8 and Week 16 post-study.

Glycated Hemoglobin (HbA1c)

Change in glycated hemoglobin (HbA1c) to assess overall glycemic control over the study period.

Time frame: At enrollment, mid-study at Week 16, and at the end-of-study visit at Week 32, At Week 8 and Week 16 post-study.

Estimated Glomerular Filtration Rate

Changes in estimated glomerular filtration rate. eGFR is measured in millilitres/minute/body surface.