The purpose of this study is to evaluate how well LY4005130 is tolerated and what side effects may occur in healthy participants. The study drug will be administered either subcutaneously (SC) (under the skin) or intravenously (IV) (into a vein in the arm). Blood tests will be performed to check how much LY4005130 gets into the bloodstream and how long it takes the body to eliminate it.

Part A for the single-ascending doses (SAD) of the study will last about 12 weeks with 9 visits. Part B for the multiple-ascending doses (MAD) of the study will either last about 16 weeks with 13 visits or 26 weeks with 14 visits not including screening.

Inclusion Criteria:

• Are overtly healthy as determined by medical evaluation including medical history, physical examination, laboratory tests, vital signs, and 12-lead (electrocardiogram) ECG. If any values are outside the normal range and considered to be significant, for example, elevated white blood cell count, the respective test may be repeated once at the discretion of the investigator without consultation with the sponsor

• If enrolled as Japanese or Chinese, the entry requirements are as follows:

  • To qualify as a participant of first-generation Japanese origin, the participant, the participant's biological parents, and all of the participant's biological grandparents must be of exclusive Japanese descent and born in Japan
  • To qualify as Chinese for the purpose of this study, all 4 of the participant's biological grandparents must be of exclusive Chinese descent and born in China

• Have a body weight 45 kilogram (kg) or greater and body mass index greater than 18 and less than 32 kilogram per square meter (kg/m²)

Exclusion Criteria:

• Are an individual of childbearing potential (IOCBP)

• Have known allergies to LY4005130, related compounds, or any components of the formulation

• Have received a live vaccine within 28 days of screening or intend to do so during the study or within 28 days after the study

  • Non-live or inactivated vaccinations are allowed
  • Bacillus Calmette Guerin vaccine must not have been administered within 12 months before screening

• Had a surgical procedure within 12 weeks before screening;

  • during the study, or
  • within 28 days after the study

• Have a history of allergy to medications that could be used to treat infusion reactions, or to the drug excipients

• Have a history or presence of multiple or severe allergies, anaphylactic reaction to prescription or nonprescription drugs, significant history of atopy, or a history of severe posttreatment hypersensitivity reactions. These reactions include, but are not limited to, erythema multiforme major, linear immunoglobulin A dermatosis, toxic epidermal necrolysis, and exfoliative dermatitis

• Have a diagnosis or history of malignant disease within 5 years prior to screening, with the following exceptions

  • Basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years, or
  • Cervical carcinoma in situ, with no evidence of recurrence within the 5 years prior to screening

• Have had breast cancer within the past 10 years

• Have a history of a primary immunodeficiency, splenectomy, or any underlying condition that predisposes the participant to infection that, in the opinion of the sponsor or investigator, poses an unacceptable risk to the participant

• Have a current or recent acute, active infection