The main purpose of this study is to measure how much of Imlunestrant (LY3484356) gets into the bloodstream and how long it takes the body to eliminate it in female participants with impaired liver function compared to female participants with normal liver function. The side effects and tolerability of Imlunestrant will also be evaluated. The study may last up to 46 days for each participant.

Inclusion Criteria:

All Participants:

• Women not of childbearing potential may participate and include those who are infertile due to surgical sterilization (hysterectomy, bilateral oophorectomy, bilateral salpingectomy or tubal ligation), congenital anomaly such as mullerian agenesis; or postmenopausal
• Are between the body mass index (BMI) of 18.0 and 42.0 kilograms per meter squared (kg/m²), inclusive, at screening

Healthy Participants:

- Healthy females as determined by medical history, physical examination, and other screening procedures, with normal liver function

Participants with Impaired Liver Function:

• Females with chronic mild, moderate and severe liver impairment, assessed by Child-Pugh scoring
• Have diagnosis of chronic hepatic impairment (>6 months), with no clinically significant changes within 90 days prior to study drug administration.

Exclusion Criteria:

• Women of childbearing potential are excluded from the study.
• Have known allergies to imlunestrant or related compounds
• Have a history of alcoholism or drug/chemical abuse within 2 years prior to check-in
• Have received blood products within 2 months prior to check-in
• Have evidence of HIV infection and/or positive human HIV antibodies
• Have used or intend to use medications that are strong inhibiters or inducers of cytochrome P450 (CYP)3A4
• Who smoke more than 10 cigarettes or use the equivalent tobacco, smoking-cessation products, nicotine-containing products, or e-cigarettes (nicotine and non-nicotine) per day.
• Have a history or presence of cardiovascular (eg, symptomatic bradycardia with resting heart rate of <60 beats per minute), respiratory, renal, gastrointestinal, endocrine, hematological, or neurological disorders capable of significantly altering the absorption, metabolism, or elimination of drugs

All enrolled participants.

Baseline up to 18 days

All participants who received at least one dose of study drug.