Intervention: Azathioprine
Trial phase: Phase 2
ATC code: L04AX01
SMILES: Cn1cnc([N+](=O)[O-])c1Sc1ncnc2nc[nH]c12
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 6
Group description: Azathioprine tablets(50mg)+ prednisone tablets(5mg)

Azathioprine: Azathioprine tablets 50 - 100 mg (approximately 1 mg/kg) once daily, plus prednisone 30 mg/day for one week, then 20 mg/day for one week, then 15 mg/day for two weeks, then 10 mg/day through Month 6.
Eligibility criteria:
Inclusion Criteria:

Men and women at least 18 years of age with a diagnosis of definite or probable AIH defined by the revised International Autoimmune Hepatitis Group (IAIHG) criteria
Elevation of serum ALT ≥ 1.5 times the upper limit of normal
Liver biopsy showing chronic hepatitis consistent with AIH
Patients able to swallow the study medication
Patients capable of understanding the purposes and risks of the study, who can give written informed consent and who are willing to participate in and comply with the study
Women of childbearing potential must have a negative serum pregnancy test within seven days prior to receiving study medication and agree to use contraceptive measures to avoid pregnancy during participation in the trial.

Exclusion Criteria:

Patients with other concurrent liver disease
Patients with cirrhosis on liver biopsy with a MELD score > 15
Patients with a history or presence of decompensated liver disease
Patients with serum creatinine ≥ 1.5 mg/dL prior to enrollment
Patients positive for HCV RNA or Hepatitis B surface antigen (HBsAg)
Patients with a history of alcohol intake > 25 g/day within the past six months
Patients with TSH outside normal range accompanied by an abnormal T4
Patients with alpha-fetoprotein ≥ 20 ng/mL
Patients with severe anemia (hemoglobin < 8 g/dL), leukopenia (WBC < 4000/mm3), or thrombocytopenia (platelet count < 100,000/mm3)
Patients with a history of recent exposure to hepatotoxic drugs
Patients who require therapy with any immunosuppressive agent other than those prescribed in the study
Patients unable or unwilling to provide informed consent
Pregnant or nursing women
Patients with reproductive potential who are unwilling/unable to use a double barrier method of contraception
Patients who have been treated with another investigational agent in the three months prior to enrollment
Patients receiving any drug interfering with tacrolimus metabolism
Patients with current malignancy or a history of malignancy (within the past 5 years), except basal or non-metastatic squamous cell carcinoma of the skin that has been treated successfully
Patients with uncontrolled concomitant infection, a systemic infection requiring treatment, or any other unstable medical condition that could interfere with the study objectives
Patients with severe diarrhea, vomiting, active peptic ulcer or gastrointestinal disorder that may affect the absorption of tacrolimus
Patients with a known hypersensitivity to azathioprine, corticosteroids or tacrolimus
Patients with any form of current substance abuse, psychiatric disorder or a condition that, in the opinion of the Investigator, may invalidate communication with the Investigator
Patients who are recipients of an organ transplant or who require treatment with immunosuppressives or corticosteroids for any disease other than AIH.