Phase 1 randomized, double-blind, three period, crossover study comparing the pharmacodynamic, pharmacokinetic, safety and tolerability profiles for Arecor ultra-rapid insulin aspart (AT247), NovoLog® and Fiasp® in participants with type 1 diabetes mellitus (T1DM) during continuous subcutaneous infusion (CSII)

Inclusion Criteria:

1. Subjects diagnosed with T1DM for at least 12 months.
2. Subjects who have been using an approved insulin pump or use multiple daily injections with basal and bolus insulin, with a stable total insulin dose <1.2 U/kg/day and bolus insulin dose <0.7 U/kg/day for at least 3 months.
3. Fasting C-peptide concentration of ≤0.3 nmol/l (0.9061 ng/ml), assessed at a plasma glucose concentration >90 mg/dL.
4. HbA1c concentration of ≤8.5% (≤69 mmol/mol).
5. BMI within the range ≥18.5 - ≤28.0 kg/m2.

Exclusion Criteria:

1. Known or suspected hypersensitivity to IMP or related products.
2. History or presence of malignant neoplasms within the past 5 years prior to the day of screening. Basal and squamous cell skin cancer and any in-situ carcinomas are allowed.
3. Clinically significant concomitant disease including cardiovascular, renal, hepatic, respiratory, gastrointestinal, hematological, dermatological, neurological, psychiatric, systemic or infections disease as judged by the investigator.
4. Supine blood pressure at screening (after resting for at least 5 min in supine position) outside the ranges for systolic 95-140 mmHg blood pressure and/or for diastolic blood pressure greater than 90 mmHg.
5. Smoking more than 5 cigarettes per day or equivalent use of any tobacco containing product, and unable to refrain from smoking during the in-house periods of the study. A positive urine cotinine test at screening and check-in.