The main objective of this study is to determine whether day and night closed-loop insulin delivery for 4 weeks under free living conditions is superior to usual insulin pump therapy in adults with type 1 diabetes and HbA1C<7.5%.

This is an open-label, multi center, randomized, crossover design study, involving a 2-4 week run-in period, followed by two 4 weeks study periods during which glucose levels will be controlled either by an automated day- and night closed-loop system or by subjects usual insulin pump therapy in random order. A total of up to 34 adults (aiming for 24 completed subjects) aged 18 years and older with T1D on insulin pump therapy and HbA1C<7.5% will be recruited through diabetes clinics and other established methods in participating centers.

Subjects will receive appropriate training in the safe use of closed-loop insulin delivery system. Subjects will have regular contact with the study team during the home study phase including 24/7 telephone support.

The primary outcome is time spent in target range between 3.9 and 10.0 mmol/L as recorded by CGM during home stay. Secondary outcomes are time spent with glucose levels above and below target, as recorded by CGM, and other CGM-based metrics.

Inclusion Criteria:

• The subject has type 1 diabetes as defined by WHO
• The subject is 18 years of age or older
• The subject will have been on an insulin pump for at least 6 months with good knowledge of insulin self-adjustment including carbohydrate counting
• The subject is treated with one of the rapid acting insulin analogues (Insulin Aspart, Insulin Lispro or Insulin Glulisine)
• HbA1c <7.5% (58mmol/mmol) based on analysis from central laboratory or equivalent
• The subject is willing to perform regular finger-prick blood glucose monitoring, with at least 6 measurements per day
• The subject is willing to wear closed-loop system at home and at work place
• The subject is willing to follow study specific instructions
• The subject is willing to upload pump and CGM data at regular intervals
• Female subjects of child bearing age should be on effective contraception and must have a negative urine-HCG pregnancy test at screening.

Exclusion Criteria:

• Non-type 1 diabetes mellitus
• Any other physical or psychological disease or condition likely to interfere with the normal conduct of the study and interpretation of the study results
• Current treatment with drugs known to have significant interference with glucose metabolism, such as systemic corticosteroids, as judged by the investigator
• Known or suspected allergy against insulin
• Subjects with clinically significant nephropathy, neuropathy or proliferative retinopathy as judged by the investigator
• Significantly reduced hypoglycaemia awareness as judged by the investigator
• More than one episode of severe hypoglycaemia as defined by American Diabetes Association in preceding 6 months (Severe hypoglycaemia is defined as an event requiring assistance of another person to actively administer carbohydrates, glucagon, or take other corrective actions).
• Random C-peptide > 100pmol/l with concomitant plasma glucose >4 mM(72 mg/dl) Total daily insulin dose > 2 IU/kg/day
• Subject is pregnant or breast feeding or planning pregnancy in near future (within next 3 months)
• Severe visual impairment
• Severe hearing impairment
• Subjects using implanted internal pacemaker
• Lack of reliable telephone facility for contact
• Subject not proficient in English (UK) or German (Austria)
• Subjects who are living alone
• Additional exclusion criteria specific for Austria: Positive results on urine drug screen (amphetamines/metamphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, opiates).
• Additional exclusion criteria specific for Austria:Positive alcohol breath test.