This is a single-centre, randomised, double-blind, 4-way crossover, 4-treatment, euglycaemic clamp study in subjects with Type 1 Diabetes Mellitus (T1DM). Each subject will be randomly allocated to one of four treatment sequences. Each sequence comprises one single dose of each of four IMPs. IMP1 and IMP2 are BioChaperone lispro formulations. They have the same composition and correspond to different development stages of a unique product which is BioChaperone insulin lispro; between them, improvements were made to prepare industrial production. Comparators (IMP3 and IMP4) are US-approved Humalog® and EU-approved Humalog®. All IMPs will be dosed at 0.2 U/Kg of insulin lispro on 4 dosing visits separated by a washout period of 5 to 15 days.

The trial will compare the characteristics of BioChaperone insulin lispro fully liquid (IMP2) formulation to US-approved Humalog and EU-approved Humalog.

Inclusion Criteria:

• Subjects with type 1 Diabetes Mellitus
• Body Mass Index (BMI) between 18.5 and 28.5 kg/m^2, both inclusive
• HbA1c <= 75 mmol/mol (<=9.0%).
• Fasting negative C-peptide (<= 0.30 nmol/L).
• Total insulin dose of < 1.2 (I)U/kg/day.
• Stable insulin regimen (with respect to safety of the subject and scientific integrity of the study) using continuous subcutaneous insulin infusion (CSII) or multiple daily insulin injections (MDI) for at least 2 months.

Exclusion Criteria:

• Known or suspected hypersensitivity to IMP(s) or related products.
• Receipt of any medicinal product in clinical development within 30 days or at least 5 half-lives of the related substances and their metabolites (whichever is longer) before randomisation in this trial.
• History of multiple and/or severe allergies to drugs or foods or a history of severe anaphylactic reaction.
• Any history or presence of cancer except basal cell skin cancer or squamous cell skin cancer as judged by the Investigator.
• Any history or presence of clinically relevant comorbidity capable of constituting a risk for the subject when participating in the trial or of interfering with the interpretation of data.
• Signs of acute illness as judged by the Investigator.
• Any serious systemic infectious disease during four weeks prior to first dosing of the trial drug, as judged by the Investigator.
• Clinically significant abnormal screening laboratory tests, as judged by the Investigator.
• Proliferative retinopathy or maculopathy as judged by the Investigator based on a recent (<1.5 years) ophthalmologic examination.
• Use of oral antidiabetic drugs (OADs) and/or GLP-1 receptor agonists within 3 months prior to screening.