Inclusion Criteria:
* Age: 18 to 75 years
* A diagnosis of PSC based on cholangiographic evidence of PSC in accordance with American Association for the Study of Liver Diseases (AASLD) guidelines
* ALP \>1.5 times the ULN at screening
* PSC with or without IBD, such as ulcerative colitis or Crohn's disease
* If patients are being administered biologic or advanced therapeutic treatments, immunosuppressants, systemic corticosteroids, obeticholic acid, fibrates, or statins, they must be on a stable dose for ≥3 months prior to, and including, Day 0 and plan to remain on a stable dose throughout the study
* If patients are receiving ursodeoxycholic acid, they must be on a stable dose (not exceeding 23 mg/kg/day) for \>3 months prior to screening
* Patient agrees to stop all probiotics for at least 2weeks prior to treatment
* Patient is unable to conceive and/or patient who's partner is unable to become pregnant and/or agree to use effective methods of contraception when engaging in heterosexual intercourse
Exclusion Criteria:
* Treatment with any investigational agents within 3 months or 5 half-lives, whichever is longer prior to treatment or during the study. Gene therapy or other long-lasting investigational agents with unknown half-life is not allowed
* History of a liver transplant or anticipated need for a liver transplant within 1 year
* Patients who show evidence of significant worsening of hepatic function will be excluded.
* Evidence of compensated or decompensated cirrhosis based on histology, relevant medical complications, or laboratory parameters
* Model for end-stage liver disease (MELD) score as below, unless the MELD is driven by anticoagulant therapy, vitamin deficiency, or kidney disease:
* MELD Score of \>12 (decompensated cirrhosis) for Part 1 of the study
* MELD Score of \>12 for Part 2 of the study
* Small-duct PSC (in the absence of large duct PSC)
* Secondary causes of sclerosing cholangitis including IgG4 associated sclerosing cholangitis
* Any history of cholangiocarcinoma, gallbladder cancer, or hepatocellular carcinoma
* History of any malignancy with lymph node or regional metastases within 5 years or current malignancy undergoing active treatment
* Patients who require chronic use of antibiotics, received antibiotics in the last 1 month, or received Rebyota or Vowst (applicable for patients with Clostridioides difficile infection)
* In patients with ulcerative colitis, partial Mayo score of \>6 or, patients with Crohn's disease if CDAI of \>220
* Chronic kidney injury
* Recent acute cholangitis (within 90 days)
* Patients with indwelling biliary drain (or stent), total proctocolectomy with ileal anal pouch, partial large bowel resections or history of small bowel resection
* Other causes of liver disease, such as autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), AIH/PSC overlap syndrome, alpha-1-antitrypsin deficiency, viral hepatitis, iron overload syndrome, Wilson disease, nonalcoholic steatohepatitis, and/or alcohol related liver disease. Additionally, positive serology for hepatitis B surface antigen (HBsAg), hepatitis C virus antibody (anti HCV) (detectable HCV RNA in the serum), or human immunodeficiency virus antibodies (anti HIV)
* Active drug (known or suspected use of illicit drugs or drugs of abuse) or alcohol abuse disorder
* Female patients who are pregnant, nursing, or planning to become pregnant during the study
* Clinically significant and/or active infection
* Subjects with a greater degree of immunosuppression, as evidenced by Alsolute neutrophil count \<500 cells/mL or in the investigator's judgement immunosuppressed and at higher risk of infection
