Study to Evaluate the Safety and Efficacy of Oral CR845 (Difelikefalin) in Patients With Primary Biliary Cholangitis (PBC) and Moderate-to-Severe Pruritus

Key Inclusion Criteria: To be eligible for inclusion into the study, a patient must meet the following criteria: * Confirmed diagnosis of PBC; * If currently taking ursodeoxycholic acid (UDCA), should be on stable dose for \>12 weeks prior to screening and plan on continuing to take UDCA throughout the study; * If previously taking UDCA, should have discontinued its use \>12 weeks prior to screening; * Self-reports experiencing daily or near-daily pruritus during the month prior to screening; * Prior to randomization has a mean baseline WI-NRS score indicative of moderate to severe pruritus. Key Exclusion Criteria: A patient will be excluded from the study if any of the following criteria are met: * Presence of Child-Pugh Class C decompensated cirrhosis at screening; * Itching secondary to biliary obstruction; * History or presence of hepatocellular carcinoma, hepatic abscess, or acute portal vein thrombosis; * Current placement on liver transplantation list with anticipated liver transplant during the course of the study or current Model for End-stage Liver Disease (MELD) score ≥15; * Alanine aminotransferase or aspartate aminotransferase \>5 × upper limit of normal at screening, or within 2 months prior to screening; * Anticipates receiving an opioid antagonist (eg, naloxone, naltrexone) or opioid-mixed agonist-antagonist (eg, buprenorphine, nalbuphine) from the start of screening through the end of the Treatment Period; * New or change of treatment with antihistamines and corticosteroids (oral, intravenous, or topical), opioids, gabapentin, pregabalin, cholestyramine, rifampicin or fibrates within 14 days prior to screening.