A Study of LY3938577 in Healthy Participants and Participants With Type 1 Diabetes Mellitus (T1DM)
The main purpose of this study is to look at the amount of the study drug LY3938577 that gets into the blood stream and how long it takes the body to get rid of it. At a later stage of this study (part B and C) the blood sugar lowering effect and the duration of action of LY3938577 will be evaluated compared to Insulin Degludec.

The study will also evaluate the safety and tolerability of LY3938577 and information about any side effects experienced will be collected.

The study will be conducted in three parts (A, B, and C). Healthy participants in part A will receive one single dose of LY3938577 or a placebo, whereas participants in Parts B and C with T1DM will receive single doses of either LY3938577 or Insulin Deglude given via intravenous (IV) infusion.

The study will last up to approximately 5.5, 10 and 13 weeks for parts A, B, and C, respectively, including screening period.
- EligibilityCriteria: Inclusion Criteria:  Part A -  • Participants who are overtly healthy as determined by medical history and physical examination.  Parts B and C -  Have Type 1 Diabetes Mellitus (T1DM) for at least 2 years with a fasting C-peptide level of 0.20 Nanomoles Per Liter (nmol/L) or less, or nonfasting C-peptide level of 0.30 nmol/L or less at screening. Have well-controlled HbA1c between 6.0% to 8.5 percent (%). Insulin pump users with a total daily basal dose between 15 to 45 International Unit (IU).  All Parts -  Have normal blood pressure, pulse rate and safety laboratory test results that are acceptable for the study. Have body mass index (BMI) between 18.0 and 35.0 kilograms per meter squared (kg/m²), inclusive, at screening. Have venous access sufficient to allow for blood sampling. Male and/or female not of childbearing potential.  Exclusion Criteria:  Parts B and C -  Have had more than 1 emergency room visit or hospitalization due to poor glucose control (hyperglycemia or diabetic ketoacidosis) within the last 6 months prior to screening. Have had any episodes of severe hypoglycemia (defined as requiring assistance due to neurologically disabling hypoglycemia) , hypoglycemia unawareness, or both within the last 6 months prior to screening. Have been treated with Glucagon-like Peptide-1 Receptor Agonists (GLP1-RA), Dipeptidyl Peptidase 4 (DPP4) inhibitor, Glucose-dependent Insulinotropic Polypeptide (GIP) agonists, Metformin, or Sodium-Glucose Transport Protein 2 (SGLT2) inhibitors within the previous 3 months. Have received systemic or inhaled glucocorticoid therapy (excluding topical, intraarticular, and intraocular preparations) for more than 14 consecutive days within 4 weeks before screening.  All Parts -  Have had any of the following cardiovascular conditions: acute myocardial infarction, New York Heart Association Class III or IV heart failure, or cerebrovascular accident (stroke). Have gastroparesis or have undergone gastric bypass (bariatric) surgery or restrictive bariatric surgery (for example, Lap-Band®) prior to screening. Have history of renal transplantation, currently receiving renal dialysis, have serum creatinine level of more than 2.00 milligrams per decilitre (mg/dL) or have an estimated glomerular filtration rate of less than 60.0 milliliters (mL) / minute) / 1.73 square meters.  Have acute or chronic hepatitis, or obvious clinical signs or symptoms of any other liver disease except non-alcoholic fatty liver disease (that is, participants with non-alcoholic fatty liver disease are eligible for participation), and/or have elevated liver enzyme measurements, as determined by the local laboratory at screening and as indicated:  TBL >2 × the Upper Limit of Normal (ULN) in the absence of Gilbert's syndrome, or ALT/serum glutamic pyruvic transaminase (SGPT) >2.5 × ULN, or AST/serum glutamic oxaloacetic transaminase (SGOT) >2.5 × ULN. - HealthyVolunteers: Accepts Healthy Volunteers - Gender: All - MinimumAge: 18 Years - MaximumAge: 64 Years - StdAgeList: Adult