This study is a 12 month open-label, two-arm randomised parallel-group trial in adult type 1 diabetes patients executed in 14 centres in the Netherlands. The aim of this study is to determine the long-term clinical effectiveness of treatment with a dual-hormone (insulin and glucagon) fully closed loop system during 12 months compared to the current most used care and to the currently most advanced technological care. Secondary objectives include the assessment of cost-effectiveness, Patient Reported Outcome Measures (PROMs), other glycaemic outcomes and safety.

Rationale: Patients with type 1 diabetes mellitus (T1DM) require lifelong insulin therapy. Insulin therapy improves but does not fully normalise blood glucose levels with current therapies. Current therapies include subcutaneous insulin injection or subcutaneous insulin infusion, combined with a device to measure glucose levels (finger stick, intermittent sensor or continuous glucose monitoring). Although having provided a huge improvement in glycaemic control, patients have to work hard every day and still have to calculate mealtime boluses. An automated insulin delivery device covering both basal and prandial insulin requirement would mean another great leap forwards. The dual-hormone fully closed loop (DHFCL) provides such a new strategy of automated insulin delivery coupled with targeted glucagon infusion as insulin-antagonist to even more approximate normal physiology.

Objective: To determine the long-term clinical effectiveness of treatment with a dual-hormone (insulin and glucagon) fully closed loop system during 12 months compared to the current most used care and to the currently most advanced technological care. Secondary objectives include the assessment of cost-effectiveness, Patient Reported Outcome Measures (PROMs), other glycaemic outcomes and safety.

Study design: A 12 month open-label, two-arm randomised parallel-group trial. Study population: Adult (age ≥18 years) patients with T1DM for at least 1 year with an HbA1c at entry ≤ 91 mmol/mol.

Intervention: The study includes two separately randomised arms, defined by current diabetes treatment. In one arm, patients currently on Multiple Daily Injections (MDI; at least once daily long-acting insulin and thrice daily short-acting insulin) in combination with continuous or flash glucose monitoring (CGM or FGM; currently the most used strategy) are 1:1 randomised to either the intervention, i.e. the DHFCL, or continuation of their current treatment. In the other arm, patients currently on hybrid closed loop treatment (HCL; presently the most advanced diabetes control treatment) are 1:1 randomised to either the intervention or continuation of their current care.

Main study parameters/endpoints: The main study endpoint is the Time in Range (TIR; % of time spent in the 3.9-10 mmol/l target range) at 12 months, which will be compared between the intervention and the control treatment within each arm. Secondary endpoints include cost-effectiveness, PROMs, other glycaemic outcomes, safety measures and device-related outcomes.

Inclusion Criteria:

• Age between 18 and 75 years;

• Diagnosed with type 1 diabetes mellitus at least one year ago;

• HbA1c ≤ 91 mmol/mol;

• Treated with either MDI with FGM/CGM or treated with HCL:

  • MDI+FGM/CGM for ≥ 3 months with an adequate sensor use during at least 70% of the time in the month prior to screening (based on sensor usage from the download summary report of the FGM/CGM);
  • HCL for ≥ 3 months with a frequency of use ≥ 70% of the time in auto mode over the previous month prior to screening;

• Does not reach the treatment goals over the last 8 weeks:

  • for MDI+FGM/CGM: subject has a TIR <80% or Time Below Range (TBR) >4%;
  • for HCL: subject has a TIR <80% or TBR >4%;

• Willing to take or switch to insulin Humalog when randomized to the intervention DHFCL arm;

• Under treatment in one of the participating centres;

• Willing and able to sign informed consent;

• Access to internet at home (for DHFCL data upload).

Exclusion Criteria:

• Current use of non-approved HCL device;
• BMI >35 kg/m2;
• eGFR<30 mL/min/1.73m2;
• Plan to change usual diabetes regimen in the next 3 months;
• Current participation in another diabetes-related clinical trial;
• Actively participating in an investigational study (drug or device) wherein he/she has received treatment from an investigational study drug or device in the last 2 weeks before enrolment into this study, as per investigator judgment;
• Established history of allergy or severe reaction to adhesive or tape that must be used in the study;
• Use of oral glucose-lowering medication;
• Active retinopathy or painful neuropathy;
• Daily use of acetaminophen during the trial (all arms), as this may influence the sensor glucose measurements. Incidental use with a maximum of e.g. 3 daily doses of 1000mg paracetamol for a maximum of 3 consecutive days is allowed
• Limited ability to see, and to hear or feel alarm signals of the closed loop system;
• Current pregnancy, breast feeding or planning to become pregnant in the 12 months of the trial or using ineffective birth control methods;
• Presence of a medical or psychiatric condition, longstanding serious adherence problems, anticipated problems in handing over diabetes control to a device or use of a medication that, in the judgment of the investigator, clinical protocol chair, or medical monitor, could compromise the results of the study or the safety of the participant.