The purpose of this investigator-initiated trial is to compare the effect of a daily injection of insulin degludec vs. basal insulin delivery via Continuous Subcutaneous Insulin Infusion (CSII), both in combination with bolus insulin delivery via the patient's usual insulin pump with insulin aspart, on glycemic variability, overall blood glucose control and incidence of hypoglycemia, all assessed by continuous glucose monitor (CGM), as well as patient satisfaction, in patients with type 1 diabetes currently using CSII.

The primary objective of this trial is to determine whether insulin degludec will provide an equally stable and consistent basal glycemic profile with lower glycemic variability as determined by Continuous Glucose Monitoring compared to insulin aspart delivered by Continuous Subcutaneous Insulin Infusion in patients with type 1 diabetes experienced in use of insulin pump therapy. Specifically, this study will determine if the percent time in the target glycemic range (70 to 180 mg/dl) by Continuous Glucose Monitoring is superior using insulin degludec than continuously infused insulin aspart, and if degludec is associated with lower glucose variability as assessed by the standard deviation (SD) of the mean daily glucose by Continuous Glucose Monitoring. Particular attention will be given to the nocturnal glucose profile (from midnight to 6 am) which most closely reflects basal insulin action as it is typically the time of day least affected by bolus insulin, food intake or exercise. Quality of life questionnaires regarding treatment preference will be used to capture patient preference for method of basal insulin delivery.

RESEARCH DESIGN AND METHODS

Study hypothesis:

It is anticipated, based on the low glycemic variability of insulin degludec shown in glucose clamp studies and seen in clinical practice, that insulin degludec will provide more stable 24 hour basal insulin action than insulin aspart by Continuous Subcutaneous Insulin Infusion (CSII) in patients with type 1 diabetes.

Primary endpoint:

Percent time in euglycemia (BG 70 to 180 mg/dl) by Continuous Glucose Monitoring (CGM) during the final 14 days of each treatment period during steady state (with basal insulin delivery as either one daily injection of insulin degludec or as insulin aspart via CSII).

Study type:

This will be a randomized, cross-over, open label, single-center study consisting of a 20 week period on each of two basal insulin delivery methods, both in combination with insulin aspart with boluses taken by insulin pump. Each 20 week period will consist of a 4 week insulin optimization period for titration of basal and bolus insulin doses, followed by a 16 week maintenance period. The final 2 weeks of the maintenance period during each treatment arm will be used for endpoint data collection. The treatment sequence will occur in random order. The study population will include patients with type 1 diabetes with good baseline glycemic control who are experienced in the use of both CSII and CGM; the cross-over design allows each subject to serve as his or her own control.

Inclusion Criteria:

1. Male and female patients > 18 years of age with type 1 diabetes using CSII with any pump for > 12 months.

2. Females must be using adequate contraception, defined as oral contraceptive pill, barrier method of contraception, or surgical method (tubal ligation or hysterectomy).

3. Good glycemic control (HbA1c < 8.0%).

4. Patients are experienced in carbohydrate counting, evidenced by pump downloads showing frequent meal boluses with realistic carbohydrate entries, few over-rides of the pump bolus calculator, few to no omitted boluses (at least 3 boluses per day), and post-meal glucose levels generally below 200 mg/dl indicating accurate carbohydrate assessment.

5. Patients are regular (>85% of time) users of the Dexcom G5 or G6 CGM.

6. Pump download confirms correct use of insulin pump features, including appropriate use of bolus calculator with minimal overrides, entering carbohydrate content of meals, at least 3 boluses taken per day, appropriate use of correction boluses, and infusion set changes every 2 to 3 days.

7. No serious comorbidities including: retinopathy requiring active intervention, eGFR < 30, CV event within the previous 6 months, active malignancy with ongoing treatment, any condition requiring chronic use of systemic glucocorticoids, or any other condition which in the opinion of the investigator would interfere with the subject's ability to comply with the study protocol or acutely affect insulin requirements.

8. Able to comply with study protocol.

9. Ability to provide written informed consent prior to any study-related procedures.

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Exclusion Criteria:

1. Subjects with type 2 diabetes.

2. Subjects with HbA1c > 8.0%

3. Subjects not using CSII and CGM (ie, on MDI)

4. Subjects inexperienced in the use of CSII, or whose pump download shows poor utilization of bolus calculator features, ie fewer than 2 boluses per day, lack of correction boluses, frequent overrides of the recommended boluses, unrealistic carbohydrate entries (suggestive of under-bolusing), not changing infusion set at least every 3 days, or other evidence of poor insulin pump usage.

5. Subjects inexperienced in or not regular users (>85% of time) of Dexcom G5 or G6 CGM

6. Subjects who are using a Medtronic pump with low blood glucose suspend who are unwilling to use the Dexcom CGM or to disengage the low blood glucose suspend feature of the pump.

7. Use of any other CGM than Dexcom G5 or G6.

8. Serious concomitant illness.

9. Females unwilling to use adequate contraception, intending to become pregnant, or breastfeeding.

10. Known or suspected allergy to study products, their excipients or related products.

11. Previous participation in this trial. Note: subjects who screen fail because of A1c may rescreen once if, in the opinion of the investigator, the HbA1c was explainable (ie, recent steroid injection or illness, etc) and atypical for the subject.

12. Hypoglycemic unawareness.

13. Episode of severe hypoglycemia (requiring assistance for treatment) within the previous 90 days.

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Data and statistical analysis will be available to any researcher with appropriate request

post study, up to 5 years

email principal investigator

This is an unblinded study as the two basal insulin delivery methods (degludec via injection vs. aspart via CSII) cannot be blinded. One group of patients will first use degludec for 20 weeks then switch to CSII for 20 weeks. As all eligible patients who sign the IRB consent form are identified, a random number will be generated to determine the treatment with which they begin first. The other group of patients will start with CSII and after 20 weeks switch to Tresiba for 20 weeks. Randomization sequence will be determined by computerized randomization program. All patients will receive both treatments unless they drop out. Dropouts are unlikely since the participants are all regular continuing patients of the site's clinical practice.