The main study objective is to compare real-time continuous subcutaneous glucose monitoring (CGM) combined with overnight automated closed-loop glucose control, and real-time CGM alone in the home setting.

Achievement of tight glycaemic control in type 1 diabetes mellitus (T1D) using intensive insulin regimens, which has been shown to be important for the prevention of long term diabetes-related complications, is limited by a significantly increased risk of hypoglycaemia. The average patient with T1D suffers two symptomatic episodes of hypoglycaemia per week, and one episode of severe hypoglycaemia, defined as an event requiring assistance of another person to administer rescue treatment in the form of carbohydrate and/or glucagon, per year.Despite the rapid advancements in insulin pump technology and the ongoing development of more physiological insulin preparations, the currently available therapeutic regimens are still unable to achieve optimal glycaemic control.The emergence of continuous glucose monitoring (CGM) over the last decade, which enables users to view in real-time estimates of plasma glucose and receive alarms for impending hypo- or hyperglycaemia, thus facilitating appropriate changes in insulin therapy, is a major step towards improved diabetes monitoring.

The desirable goal is the development of an insulin delivery that is glucose responsive and the development of effective real time glucose monitoring should allow this. Glucose responsive insulin delivery should allow achievement of ideal glucose targets with less risk of hypoglycaemia. Closed-loop systems may provide a realistic treatment option for people with T1D. The research we are conducting at the University of Cambridge has been focused on developing a closed-loop system for overnight glucose control in patients with T1D. The studies that have been performed so far employ model predictive control (MPC) - this algorithm estimates patient-specific parameters from CGM measurements taken every 1 to 15 minutes and makes predictions of glucose excursions, which are then used to calculate basal insulin infusion rates. We hypothesize that overnight automated closed-loop glucose control in the home setting will be efficacious and safe compared to CGM alone, in T1D subjects on insulin pump treatment.

Inclusion Criteria:

• Type 1 diabetes, as defined by WHO for at least 6 months or confirmed C-peptide negative.
• On insulin pump therapy for at least 3 months

Exclusion Criteria:

• Non-type 1 diabetes mellitus
• Any physical/psychological disease likely to interfere with the study
• Taking medication likely to interfere with interpretation of the results
• Known/suspected allergy against insulin
• Patients with clinically significant nephropathy, neuropathy or retinopathy as judged by the investigator
• Ongoing severe recurrent hypoglycaemia as judged by the investigator.