TTP399-206 is a Phase 2a multicenter double blind cross over randomized study of cadisegliatin in participants with T1D using hybrid closed loop systems to manager their diabetes. Patients using a hybrid closed loop insulin pump to manage their diabetes will be randomized to either receive blinded cadisegliatin 800 mg QD as an adjunctive therapy to their insulin treatment or placebo QD along with their insulin treatment. The trial begins with a screening period of up to 2 weeks, followed by a device training and insulin adjustment period of 1-2 weeks leading into the first double-blind treatment period of 6 weeks. There will then be a washout period of 1-2 weeks followed by the second double-blind treatment period of 6 weeks where the patient will cross-over to the treatment arm that they did not receive in the first treatment period.

TTP399-206 is a 20 week, Phase 2a trial designed to evaluate efficacy and safety of cadisegliatin in participants with T1D who are using hybrid closed loop (HCL) systems to manage their condition to gather preliminary data to understand how cadisegliatin performs in an HCL setting.

Key Inclusion Criteria:

• Participants >= 18 years of age
• Fasting plasma C-peptide levels <0.6 ng/ml
• Average TIR < 70% at the end of the screening period
• Currently on a hybrid closed loop device for at least 3 months and willing to stay on the same model of pump device for study duration
• Willing to wear a study provided CGM for study duration
• Capable of participating in a 30-minute lasting exercise test

Key Exclusion Criteria:

• Have Type 2 Diabetes Mellitus (DM), monogenic diabetes, maturity-onset diabetes, other unusual or rare forms of DM, or diabetes resulting from a secondary disease.
• Have been hospitalized for DKA within 3 months
• Have uncontrolled hypothyroidism or hyperthyroidism
• Have QTcF interval > 450 msec for males or > 470 msec for females
• Have a personal or family history of long QT syndrome, Torsades de pointes, or other complex ventricular arrhythmias
• Have persistent, uncontrolled hypertension
• Have clinically significant cardiovascular or cerebrovascular disease
• Have proliferative retinopathy or maculopathy requiring acute treatment
• Have a serious concomitant systemic disorder incliuding but not limited to HIV or active Hep B or Hep C
• Diagnosed and/or treated for malignancy within 3 years
• Have used any of the following medications within the specified time periods: any non-insulin anti-diabetic therapies (e.g.SGLT-2 inhibitors, GLP-1 receptor agonists, metformin, sulfonylureas, DPP-4 inhibitors, pramlintide, a-glucosidase inhibitors, or glucose dependent insulinotropic polypeptide agonists) within 30 days, antipsychotic medications (e.g. olanzapine, risperidone, clozapine, quetiapine, and haloperidol) within 30 days, systemic corticosteroids for ≥7 days for a temporary medical condition within 30 days,