A Study of LY3981314 in Participants With Autoimmune Hepatitis

Inclusion Criteria:

• Have a confirmed diagnosis of autoimmune hepatitis (AIH) for greater than or equal to (≥) 6 months according to American Association for the Study of Liver Diseases diagnostic criteria (Appendix 8, Section 10.8)

• Have alanine aminotransferase (ALT) greater than (>) 1.5x upper limit of normal (ULN) to less than (<) 5x ULN

• Have elevated soluble FAS (sFAS) based on Sponsor predetermined threshold

• Be on a stable immunosuppressive medication regimen for AIH with no dose changes or weaning of treatment for ≥8 weeks prior to screening, and no anticipated medication adjustments until after the post-treatment liver biopsy at Day 29. The following medications are permitted for the management of AIH:

  • Azathioprine
  • 6-Mercaptopurine
  • Inhibitors of inosine monophosphate dehydrogenase (mycophenolate mofetil, mycophenolate sodium, mycophenolic acid)
  • Tacrolimus
  • Cyclosporine
  • Corticosteroids at a dose equivalent to less than or equal to (≤) 10 mg of prednisone per day

Exclusion Criteria:

• Have clinical, laboratory, histological, or imaging evidence of cirrhosis

• Have a controlled attenuation parameter (CAP) score >300 decibel-milliwatt (dB/m) as measured by transient elastography

• Have clinical evidence of hepatic decompensation as defined by the presence of any of the following abnormalities

  • international normalized ratio >1.3
  • history of esophageal varices, ascites or hepatic encephalopathy

• Have or had other forms of chronic liver disease per Medical History:

  • alcoholic liver disease
  • hepatitis B
  • hepatitis C
  • history of primary biliary cholangitis or primary sclerosing cholangitis
  • history of celiac disease, or other autoimmune disorders including immune-checkpoint related hepatitis associated with elevated aminotransferases
  • uncontrolled thyroid disease
  • current drug-induced liver disease based on typical exposure and history
  • metabolic dysfunction associated steatohepatitis, Wilson's disease, hemochromatosis, alpha-1-antitrypsin deficiency, or cystic fibrosis-related liver disease
  • suspected or proven liver cancer
  • any other physician confirmed liver disease other than AIH

• Have any medical condition that, in the opinion of the investigator, may increase the risk of complications related to liver biopsy (for example, a known coagulopathy, inherited disorders of hemostasis, sickle cell disease, amyloidosis)

• Have any of the following laboratory abnormalities at screening:

  • Platelet count <150,000/cubic millimeter (mm³)

  • Hemoglobin

    • <10 grams per deciliter (g/dL) for individuals assigned female at birth (AFAB)
    • <11 g/dL for individuals assigned male at birth (AMAB)

  • Absolute neutrophil count <1000/mm³

  • Transferrin saturation >50 percentage (%) (except when it has been demonstrated that a diagnosis of hemochromatosis has been excluded by genetic testing or when a previous liver biopsy has demonstrated no evidence of iron overload.)

  • Total bilirubin > ULN unless known Gilbert's syndrome per Medical History.

    • Gilbert's syndrome participant must have normal direct bilirubin; if diagnosis of Gilbert's cannot be confirmed by medical records, participant may not participate in the study

  • Have renal impairment measured as estimated glomerular filtration rate<60 milliliters per minute (mL/min)/1.73 square meter (m²), calculated using the Chronic Kidney Disease Epidemiology Collaboration Creatinine Equation (2021 version), as determined by the local laboratory during screening