The main purpose of this study is to compare the amount of LY3871801 that gets into the blood stream and how long it takes the body to get rid of it, when given as crystalline freebase tablet (test) and as a solid dispersion oral suspension (reference) in healthy participants. The information about any adverse effects experienced will be collected and the tolerability of LY3871801 will also be evaluated. The study may last up to approximately 15 days excluding the 28 days of screening period.

Inclusion Criteria:

• Participants who are overtly healthy as determined by medical evaluation including medical history and physical examination.
• Have body weight ≥ 45 kilograms (kg) and body mass index (BMI) within the range 18.5 to 40.0 kilograms per meter squared (kg/m²)
• Participants not of childbearing potential

Exclusion Criteria:

• Have known allergies to LY3871801, related compounds or any components of the formulation, or history of significant atopy.
• Have an abnormal blood pressure and/or pulse rate, deemed to be clinically significant by the investigator
• Have used or intend to use prescription or nonprescription medication (including dietary supplements, vitamins, herbal supplements, and/or alternative medicines) within 7 days prior to dosing
• History of drug or alcohol abuse in the past 2 years and/or regularly use known drugs of abuse
• Are unwilling to stop alcohol consumption 24 hours prior to admission and while resident at the clinical research unit (CRU).
• Smoke more than 10 cigarettes per day (or the equivalent, including electronic cigarettes) or are unable to abide by the CRU smoking restrictions.