A Three-part Study to Evaluate the Safety, Pharmacokinetics and Pharmacodynamics of MK-2640 in Healthy Participants (Part I) and Participants With Type 1 Diabetes Mellitus (Parts II and III) (MK-2640-001)

Inclusion Criteria (Part I): * healthy male or healthy female of non-child bearing potential * in good health * is a non-smoker and/or has not used nicotine or nicotine-containing products (e.g., nicotine patch) for at least approximately 3 months Inclusion Criteria (Parts II and III): * male or female of non-child bearing potential * has T1DM for at least 12 months * on stable doses of insulin * in good health * is a nonsmoker and/or has not used nicotine or nicotine-containing products (e.g., nicotine patch) for at least approximately 3 months Exclusion Criteria: * is mentally or legally incapacitated, or has significant emotional problems at the time of screening visit or expected during the conduct of the trial or has a history of clinically significant psychiatric disorder of the last 5 years * has a history of clinically significant endocrine (except T1DM for Part II subjects), gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory, genitourinary or major neurological (including stroke and chronic seizures) abnormalities or diseases * is positive for hepatitis B surface antigen, hepatitis C antibodies or human immunodeficiency virus (HIV) * has a history of cancer (malignancy), except adequately treated non-melanomatous skin carcinoma or carcinoma in situ of the cervix * has a history of significant multiple and/or severe allergies, or has had an anaphylactic reaction or significant intolerability to prescription or non-prescription drugs or food, had major surgery, donated or lost 1 unit of blood within 4 weeks prior to the screening visit * has participated in another investigational trial within 4 weeks prior to the screening visit * is unable to refrain from or anticipates the use of any medication, including prescription and non-prescription drugs or herbal remedies beginning approximately 2 weeks prior to administration of the initial dose of trial drug, throughout the trial, until the posttrial visit * consumes greater than 3 glasses of alcoholic beverages daily * consumes greater than 6 servings of coffee, tea, cola, energy-drinks, or other caffeinated beverages per day. * is currently a regular or recreational user of cannabis, any illicit drugs or has a history of drug (including alcohol) abuse within approximately 3 months Exclusion Criteria (Parts II and III): * has a history of diabetic ketoacidosis in the last 6 months. * has had one or more severe hypoglycemic episodes associated with hypoglycemic seizures, comas or unconsciousness within 2 weeks prior to dosing * has used systemic (intravenous, oral, inhaled) glucocorticoids within 3 months of screening or is anticipated to require treatment with systemic glucocorticoids during study participation * has a history of hypersensitivity to pharmacologic insulins or to any of the inactive ingredients in regular human insulin, or to any E. coli-derived drug product