Despite recent pharmacological and technological advantages, hypoglycemia remains to be the key limiting factor in achieving optimal glycemic control in people with type 1 diabetes. State-of-the-art treatment for type 1 diabetes is insulin in pens or pumps that focus on reducing hyperglycemia after relative insulin deficiency e.g. after food intake. In recent years, we focused on adding low-dose glucagon to insulin therapies for the treatment and prevention of hypoglycemia - referred to as "dual-hormone treatment". We have shown that low-dose glucagon is efficient in treating mild hypoglycemia and that several factors may affect its glucose response. Our next step is to test whether the combined delivery of insulin and glucagon can improve glucose control in individuals with type 1 diabetes. In this proposal, we want to test the efficacy, safety and feasibility of a dual-hormone closed-loop system, also known as an artificial pancreas. The closed-loop system involves automatic infusion of glucagon and insulin based on continuous glucose measurements. The system will be tested in a 33-hour in-clinic study comparing the glucose control by the combined automatic delivery of insulin and glucagon with the automatic delivery of insulin-only. The study is performed at Steno Diabetes Center Copenhagen (SDCC) in collaboration with the Technical University of Denmark (DTU). We expect that the study will clarify whether low-dose glucagon added to insulin therapy can improve the glucose control in adults with type 1 diabetes. We believe that the utilization of glucagon will allow for a weight neutral optimization of glucose control, reduce risk of hypoglycemia and reduce disease burden that will reduce diabetes complications and cardiovascular diseases.

Rationale: We hypothesize that our newly developed dual-hormone insulin-glucagon closed-loop system (DCL) is safe, efficient and superior to our single-hormone insulin-only closed-loop system (SCL). The study aims to compare the glucose control achieved by DCL with our SCL.

Design: A randomized single-blinded placebo-controlled cross-over 33-hour in-clinic study of glucose control achieved with DCL versus SCL in adults and adolescents with type 1 diabetes.

Participants: 13 insulin-pump treated T1D participants will be included, if they are 15-80 years old, have T1D for ≥ 3 years, use insulin pumps with FiAsp®, and have an HbA1c≤ 8.5% (69 mmol/mol).

Procedures: In this two-phase study 1) we test the operability of our closed-loop systems and 2) compare glucose control by DCL with SCL. The two studies are identical except for the blinding procedures. In the first phase (pilot study), four participants are included, and the glucagon/saline pump is not masked. In the second phase (main study), 13 participants are included, and are as well as the investigators blinded for the content in the glucagon/saline pump.

Two days prior to study visit, a CGM (Dexcom® G6) is place on the participant's abdomen. At study visits, participants arrive in the evening at our research unit and get their insulin pump disconnected. Two study pumps (Dana Diabecare RS®, SOOIL) are attached: one pump infuses insulin (FiAsp®, Novo Nordisk) and the other infuses either glucagon (GlucaGen®, Novo Nordisk) or saline. Once a sampling cannula is placed in an antecubital vein, the study is initiated and the closed-loop system (DCL vs SCL) takes over the glucose control for the next 33 hours. Except from the control algorithm (SCL vs DCL), the study days are identical. Participants can move around freely in the clinic for 33 hours but will perform a 45-min moderate (50% VO2max) exercise session, consume three meals with variant carbohydrate content, and sleep during two overnight periods. Participants will be monitored frequently with blood samples (drawn from the antecubital vein), blood pressure, pulse, and VAS scale for nausea.

Inclusion criteria

• Age ≥ 18 years
• T1D ≥ 2 years
• Insulin pump therapy ≥ 1
• Currently treated with FiAsp® - insulin
• HbA1c ≤ 8.5% (69 mmol/mol) Exclusion criteria
• Pregnancy or nursing
• Inability and willingness to comply with all protocol procedures, e.g. exercise, sleeping, blood sampling, and meal consumption
• Plan to become pregnant or sexually active and not using adequate contraceptive methods (sterilization, intrauterine device, contraceptive pill, patch or injection)
• Hypoglycemia unawareness (self-reported lack of hypoglycemia symptoms when blood glucose is < 3.0 mmol/l)
• Use of anti-diabetic medicine (other than insulin), corticosteroids or other drugs affecting glucose metabolism during or within 30 days prior to study participation
• History of coronary artery disease or congestive heart failure
• Abnormal ECG suggestive of coronary artery disease and increased risk of malignant arrhythmia
• Allergy to glucagon or lactose
• Pheochromocytoma
• Other concomitant medical or psychological condition that according to the investigator's assessment makes the patient unsuitable for study participation

Withdrawal criteria

• In case of pregnancy (or desire for pregnancy), female subjects are withdrawn
• Lack of compliance to any of the important study procedures in the discretion of the investigator
• Unacceptable adverse effects in the discretion of the investigator
• Withdrawal on participants request will be accepted at any time without further justification

Patients who complete or withdraw from the study continue their usual quarterly follow-up visits at the diabetes clinic. Withdrawal does not affect their statutory patient rights.