Hybrid Closed-Loop Control With Smart Prandial Insulin Dosing in Type 1 Diabetes

This is a single center, double-blind, randomized, crossover trial. The study team will target enrollment of 30 adolescents (age 12 - <18 years) with T1D who currently manage their diabetes with an insulin pump and a continuous glucose monitoring (CGM) system. Participants will be randomized 1:1 to the use of the standard HCL system (USS Virginia) vs. the HCL system with the smart bolus calculator first. The trial will be held at a local camp facility and will consist of EITHER a weeklong (6 day/5 night) camp OR two long weekends (4 day/3 night) separated by a washout period of about one week.

Inclusion criteria

• Age ≥12 and <18 years old at time of consent
• Clinical diagnosis, based on investigator assessment, of T1D for at least one year
• Currently using insulin for at least six months
• Currently using an insulin pump for at least three months
• Currently using a CGM system for at least three months
• Having at least 75% of CGM data over the previous four weeks
• Using insulin parameters such as carbohydrate ratio and correction factors consistently on their pump in order to dose insulin for meals or corrections
• Access to internet and willingness to upload data during the study as needed
• For females, not currently known to be pregnant or breastfeeding
• A negative urine pregnancy test will be required for all females of childbearing potential
• Willingness to suspend use of any personal CGM for the duration of the clinical trial once the study CGM is in use
• Willingness to switch to lispro (Humalog) or aspart (Novolog) if not using already, and to use no other insulin besides lispro (Humalog) or aspart (Novolog) during the study
• Total daily insulin dose (TDD) of at least 10 U/day
• Willingness not to start any non-insulin glucose-lowering agent during the course of the trial (including metformin, GLP-1 agonists, pramlintide, DPP-4 inhibitors, biguanides, sulfonylureas and naturaceuticals)
• Willingness to eat at least 40 grams of carbohydrates per meal
• An understanding and willingness to follow the protocol and signed informed consent
• Participants and parent/legal guardians will be proficient in reading and writing in English
• Willingness to comply with COVID-19 precautions as defined by the study team
• Having completed a COVID-19 vaccination with an FDA-approved COVID-19 vaccine at least two weeks before the first study admission, and willing to provide a copy of the COVID-19 vaccination card

Exclusion criteria

• Hemoglobin A1c <5% or >10% if measured at screening or available from historical medical report performed within the last 6 months; in absence of a valid HbA1c measurement, average blood glucose estimated from CGM data to be approximately between 100 and 240 mg/dL
• History of diabetic ketoacidosis (DKA) in the 6 months prior to enrollment
• Severe hypoglycemia resulting in seizure or loss of consciousness in the 6 months prior to enrollment
• Pregnancy or intent to become pregnant during the trial
• Currently breastfeeding or planning to breastfeed
• Currently being treated for a seizure disorder
• Planned surgery during study duration
• History of cardiac arrhythmia (except for benign premature atrial contractions and benign premature ventricular contractions which are permitted)
• Treatment with any non-insulin glucose-lowering agent (metformin, GLP-1 agonists, pramlintide, DPP-4 inhibitors, SGLT-2 inhibitors, biguanides, sulfonylureas and naturaceuticals)
• A known medical condition that in the judgment of the investigator might interfere with the completion of the protocol.
• Use of an insulin delivery mechanism that is not downloadable by the participant or study team
• Known contact with COVID-positive individual within 14 days of any study admission without negative follow-up COVID-19 Polymerase Chain Reaction (PCR) test performed 3-5 days after the date of exposure
• Symptoms of COVID-19 (e.g., fever, shortness of breath, unexpected loss of taste or smell) developed within 14 days of any study admission
• A positive COVID-19 test within 14 days of any study admission or during study admission participation
• Not being fully vaccinated at the time of the first camp admission (according to Center for Disease Control (CDC) guidelines a person is intended to be fully vaccinated after two weeks from either the second dose of the Pfizer or Moderna vaccine, or the single dose of the Johnson & Johnson vaccine)