The main objective of this study is to determine whether day and night closed-loop insulin delivery for 12 weeks under free living conditions is superior to addition of real-time continuous glucose monitoring in adults with type 1 diabetes and sub-optimal glucose control on insulin pump therapy.

This is an open-label, multi centre, randomised, crossover design study, involving a 6 to 8 week run-in period, during which glucose control will be optimised by a professional pump educator, followed by two 3 months study periods during which glucose levels will be controlled either by an automated closed-loop system or by subjects usual insulin pump therapy augmented with real-time continuous glucose monitoring in random order. A total of up to 42 adults (aiming for 30 completed subjects) aged 18 years and older with T1D on insulin pump therapy will be recruited through diabetes clinics and other established methods in participating centres. Subjects who drop out of the study within the first 6 weeks of the first intervention arm will be replaced.

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. Subjects will be discouraged from international travel during the first two weeks of closed-loop use.

The primary outcome is time spent in target range between 3.9 and 10.0 mmol/L as recorded by CGM (adjusted for potential over-estimation) during home stay. Secondary outcomes are the HbA1c, time spent with glucose levels above and below target, as recorded by CGM, and other CGM-based metrics.

Inclusion Criteria:

1. The subject has type 1 diabetes as defined by WHO
2. The subject is 18 years of age or older
3. The subject will have been on an insulin pump for at least 6 months with good knowledge of insulin self-adjustment including carbohydrate counting
4. The subject is treated with one of the rapid acting insulin analogues (Insulin Aspart, Insulin Lispro or Insulin Glulisine)
5. HbA1c ≥7.5% (58mmol/mmol) and ≤ 10% (86 mmol/mmol) based on analysis from central laboratory or equivalent
6. The subject is willing to perform regular finger-prick blood glucose monitoring, with at least 6 measurements per day
7. The subject is willing to wear closed-loop system at home and at work place
8. The subject is willing to follow study specific instructions
9. The subject is willing to upload pump and CGM data at regular intervals
10. Female subjects of child bearing age should be on effective contraception and must have a negative urine-HCG pregnancy test at screening. In addition in Germany, women of childbearing potential must use a highly effective method of birth control, which is defined as those which result in a low failure rate (i.e. less than 1% per year) and must use two independent methods of contraception, e.g. diaphragm and spermicide-coated condom.

Exclusion Criteria:

1. Non-type 1 diabetes mellitus
2. Any other physical or psychological disease or condition likely to interfere with the normal conduct of the study and interpretation of the study results
3. Current treatment with drugs known to have significant interference with glucose metabolism, such as systemic corticosteroids, as judged by the investigator
4. Known or suspected allergy against insulin
5. Subjects with clinically significant nephropathy, neuropathy or proliferative retinopathy as judged by the investigator
6. Significantly reduced hypoglycaemia awareness as judged by the investigator
7. More than one episode of severe hypoglycaemia as defined by American Diabetes Association (31) 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).
8. Random C-peptide > 100pmol/l with concomitant plasma glucose >4 mM(72 mg/dl)
9. Total daily insulin dose > 2 IU/kg/day
10. Subject is pregnant or breast feeding or planning pregnancy in near future (within next 3 months)
11. Severe visual impairment
12. Severe hearing impairment
13. Subjects using implanted internal pacemaker
14. Lack of reliable telephone facility for contact
15. Subject not proficient in English (UK) or German (Germany and Austria)
16. Subjects who are living alone

Additional exclusion criteria specific for Austria and Germany

1. Positive results on urine drug screen (amphetamines/metamphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, opiates).
2. Positive alcohol breath test.

Additional exclusion criteria specific for Germany only

1. Positive reaction to any of the following tests: hepatitis B surface (HBs) antigen, anti-hepatitis C virus (anti-HCV) antibodies, anti-human immunodeficiency virus (HIV) 1 antibodies, anti-HIV2 antibodies.

2. Significantly reduced hypoglycaemia awareness withGold score ≥ 4 according to Geddes J et al, Diabetes Care 2007

3. Serious macro- and microangiopathy

4. Serious anomalies of the skin

5. Serious skin diseases (e.g. psoriasis vulgaris, bacterial skin diseases) located at places of the body, which potentially are possible to be used for localisation of the glucose sensor)

6. Renal insufficiency

7. Epilepsy

8. Eating disorders (like bulimia or anorexia nervosa)

9. Disorders of the lipid metabolism

10. Blood transfusion requiring patients

11. Psychiatric diseases and related conditions

12. Patients with frequent catheter abscesses having occurred in connection with the pump therapy

13. Patients with medically documented allergy towards the adhesive (glue) of plasters

14. Abnormal blood values for:

    • the creatinine clearance,
    • erythropoietin,
    • TSH.

15. Patients with the following concomitant medications or misuse of substances:

    • steroids,
    • anticoagulant therapies.

16. Patients with a planned intervention under general anaesthesia.

17. Patients who do shift work