Phase II AutoImmune Hepatitis

Written informed consent must be obtained before any assessment is performed. Patients with a confirmed diagnosis of AIH either Type II or Type II, based on the International Criteria for the Diagnosis of AIH, will be enrolled at screening. * Males and females aged from 18 to 75 years old, of non-child bearing potential * Females must be either: Postmenopausal for greater than two years Postmenopausal for less than two years with an FSH level greater \> 40mIU/mL Documented as surgically sterile (bilateral tubal ligation, bilateral oophorectomy or post-hysterectomy) at least three months prior to the screening evaluation Or be greater than age 40, does not want more children, is currently using at least one effective method of birth control at the time of screening and agrees to using two effective methods of birth control starting with Study day 0 and through the 42 days duration of the study • Must have in the judgment of the Investigator, the diagnosis of AIH, or have a score on the International Criteria for the Diagnosis of AIH (Appendix 2) of: Pretreatment score ≥15 Post-treatment score of ≥17 * Treatment with prednisone and/or other oral, immunosuppressive drug(s) must be stabilized for 6 weeks prior to screening for this study. * All patients with an abnormal ALT confirmed by two measurements 2 weeks apart at screening, with the present dose(s) of their immunosuppressant medication(s) * Patients do not have to have a documented relapse after completion of an initial course of therapy * Permitted concomitant immunosuppressant medications will include: Azathioprine dose equal to/or less 100 mg per day Budesonide dose equal to/or less 9 mg per day Mycophenolate metil equal to/or less 3000 mg per day Prednisone equal to/or less than 30 mg per day Ursodeoxycholic acid equal to/or less than 1500 mg er day Prograf equal to/or less than 6 mg per day * Patients must agree to abstain from alcohol and illicit drugs use during their participation in the study protocol * ALT and AST levels greater than 2 times less than five times the upper limit of the normal (reference) range (ULN) and have no clinical or laboratory evidence of hepatic decompensation (i.e., platelets ≥ 100,000/mm, total bilirubin ≤ 1.5 × ULN, prothrombin time ≤ 1.2 × ULN and albumin ≥ 3.0 g/dL) for inclusion. * Normal renal function as determined by a serum creatinine Exclusion criteria Patients fulfilling any of the following criteria are not eligible for inclusion in this study. No additional exclusions may be applied by the Investigator, to ensure that the study population will be representative of all eligible patients. * Any other forms of chronic liver disease that is not under treatment * Decompensated liver disease defined on the basis of any one of the following laboratory parameters at the screening evaluation: total bilirubin \> 1.5 × ULN, prothrombin time \> 1.2 × ULN, platelets ≤ 100,000/mm3, or albumin \< 3 g/dL OR current or prior history of clinical hepatic decompensation (e.g., ascites, jaundice, encephalopathy or variceal hemorrhage) * Hemoglobin \< 11 g/dL at the screening evaluation * Serological evidence of infection with HIV upon review of the medical record * Evidence of hepatocellular carcinoma (i.e., screening α-fetoprotein \> 50 ng/mL or other standard of care measure and ultrasound) * Patients with, or a history of clinically significant oncologic, pulmonary, hepatic, gastrointestinal, renal, other cardiovascular, hematologic, metabolic, endocrine, neurologic, immunologic or hematologic illness or any other major medical disorder that, in the judgment of the Investigator, would interfere with patient treatment, assessment or compliance with the protocol or should otherwise preclude their participation in this trial * Have received therapy with potentially hepatotoxic drugs within 3 months (90 days) prior to day 1 or are expected to receive such therapy during the study * Patients who are expected to receive a change in their immunosuppressant therapies during the protocol * Patients who may receive chemotherapeutic agents (e.g. immunoglobulins and other immune- or cytokine-based therapies) during the study for any other medical condition * Use of other investigational drugs within 5 half-lives of enrollment, or within 30 days until the expected pharmacodynamic effect has returned to baseline, whichever is longer * History of hypersensitivity to study drug or its excipients * Hepatitis B and C, infectious hepatitis (documented in medical record may need to repeat prior to enrollment) * Tuberculosis (documented in medical record) * Primary sclerosing cholangitis, primary biliary cholangitis (documented in medical record and may need to repeat prior to enrollment) * Alpha-1 antitrypsin deficiency, hemochromatosis, or Wilson's disease (documented in the medical record)