A Phase I, randomised, single-centre, double-blind, single-dose, three period, balanced cross over study in a glucose clamp setting. The study compares the pharmacodynamic, pharmacokinetic and safety characteristics of AT247, NovoRapid® and Fiasp® in male participants with type I diabetes mellitus.

Inclusion Criteria include:

1. Diagnosis type I Diabetes Mellitus for at least 12 months
2. Receiving treatment with multiple daily insulin injections or insulin pump therapy for at least 12 months
3. Fasting C-peptide concentration ≤8.5% (≤69 mmol/mol) at screening
4. BMI 18.5-35.0 kg/m2

Exclusion Criteria include:

1. known or suspected hypersensitivity to Investigational Medicinal Products
2. clinically significant concomitant disease or abnormal lab values
3. supine systolic BP outside range 95-140 mmHg and/or diastolic BP greater than 90 mmHg