This is a single-centre, randomised, double-blind, three-period, complete cross-over trial comparing the pharmacokinetic and the pharmacodynamic properties of BioChaperone® insulin lispro and the two active comparators Fiasp® and Novorapid® when given as a bolus on top of basal delivery with an insulin pump in subjects with type 1 diabetes mellitus. Each subject will be randomly assigned to a treatment sequence consisting of 3 dosing visits during which the subject will receive the investigational products. In a euglycaemic clamp setting, subjects will be given a bolus dose of 0.15 U/kg body weight.

Throughout the glucose clamp procedure, blood glucose will be stabilised at a target level of 100 mg/dL by means of an intravenous infusion of glucose. Blood samples for pharmacokinetic assessment will be drawn at specified timepoints and glucose infusion rates and blood glucose concentrations will be recorded for pharmacodynamic assessment during the 10-hour clamp procedure after dosing.

Inclusion Criteria:

• Type 1 Diabetes Mellitus for more than 12 months.
• BMI between 18.5 and 28.5 kg/m².
• HbA1C level <=9.0%.
• Insulin treated for at least 12 months with total insulin dose <1.2U/kg/day.

Exclusion Criteria:

• Type 2 Diabetes Mellitus.
• History of multiple and/or severe allergies to drugs or foods.
• Any history or presence of clinically relevant cardiovascular, pulmonary, respiratory, gastrointestinal, hepatic, renal, metabolic, endocrinological (with the exception of conditions associated with diabetes mellitus), haematological, dermatological, neurological, osteomuscular, articular, psychiatric, systemic, ocular, gynaecologic (if female), or infectious disease, or signs of acute illness as judged by the Investigator.
• More than one episode of severe hypoglycaemia with seizure, coma or requiring assistance of another person during the past 6 months.
• Proliferative retinopathy or maculopathy and/or severe neuropathy, in particular autonomic neuropathy.
• Females of childbearing potential, who are pregnant, breast-feeding or intend to become pregnant or are not using highly effective contraceptive methods.