A Research Study of How Different Doses of a New Medicine NNC0148-0287 C (Insulin 287) Work on the Blood Sugar in People With Type 1 Diabetes When it is Taken Once a Week

A Trial Investigating the Pharmacokinetics and Pharmacodynamics of NNC0148-0287 C (Insulin 287) at Steady State Conditions in Subjects With Type 1 Diabetes

This study compares the new long-acting insulin 287 with the marketed insulin glargine for use in type 1 diabetes. The study will test how insulin is taken up in your blood, how long it stays there and how the blood sugar is lowered. The participant will get both of the insulins in a random order. Insulin 287 is a new medicine while insulin glargine is already approved for the treatment of diabetes and can be prescribed by a doctor. The participant will get 8 weekly doses of insulin 287 and 14 daily doses of insulin glargine. There will also be a run-in period of 2 days to 4 weeks with daily doses of insulin glargine before you start the insulin 287 period. All doses will be injected under the skin. The study will last for about 16 to 24 weeks. The participant will have 27 visits with the study doctor.

Inclusion Criteria:

• Male or female, aged 18-64 years (both inclusive) at the time of signing informed consent
• Diagnosed with type 1 diabetes mellitus greater than or equal to 1 year prior to the day of screening
• Current daily basal insulin treatment greater than or equal to 0.2 U/kg/day
• Body mass index between 18.5 and 29.0 kg/m^2 (both inclusive)
• HbA1c less than or equal to 9.0%

Exclusion Criteria:

• History or presence of any clinically relevant respiratory, metabolic, renal, hepatic, gastrointestinal or endocrinological conditions. Subjects with complications associated to diabetes can be included only if they are judged to be mild by the investigator. Subjects with other comorbidities (e.g. dyslipidaemia, hypertension and hypothyroidism) can be included if they have a stable treatment and are in adequate control according to the judgement of the investigator- Female who is pregnant, breast-feeding or intends to become pregnant or is of child-bearing potential and not using adequate contraceptive methods (adequate contraceptive measures as required by local regulation or practice)
• Known or suspected hypersensitivity to trial products or related products