Safety, Tolerability, and Efficacy of Etrasimod (APD334) in Participants With Primary Biliary Cholangitis

Key Inclusion Criteria: * Males or females aged 18 to 80 years (inclusive) at the time of screening, with confirmed Primary Biliary Cholangitis (PBC) diagnosis based upon at least 2 of 3 criteria: * Anti-mitochondrial antibodies (AMA) titer \>1:40 on immunofluorescence or M2 positive by enzyme-linked immunosorbent assay (ELISA) or positive PBC-specific antinuclear antibodies (anti-GP210 and/or anti-SP100) * Alkaline phosphatase (ALP) \>1.5 x upper limit of normal (ULN) for at least 6 months * Liver biopsy findings consistent with PBC * Use of ursodeoxycholic acid (UDCA) for at least 6 months prior to screening (stable dose for at least 3 months immediately prior to screening) * Participants must have ALP \>1.5 x ULN but \<10 x ULN, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \<5 x ULN, and total bilirubin \<ULN, at all screening visits * AST, ALT, ALP, and total bilirubin must have 2 values at least 4 weeks apart that are within 20% of each other Key Exclusion Criteria: * Chronic liver disease of a non-PBC etiology. However, PBC participants accompanied with primary Sjögren's syndrome (pSS) are eligible to be enrolled. * History or evidence of clinically significant hepatic decompensation * Medical conditions that may cause non-hepatic increases in ALP (e.g., Paget's disease) * Clinically significant infections within 6 weeks prior to treatment start, or infection with hepatitis C virus anytime in the past * Immunosuppressive, immunomodulating, or investigational agents within 30 days prior to treatment start * Treatment with obeticholic acid (OCA) within 30 days prior to Day 1 Note: Other protocol defined Inclusion/Exclusion criteria may apply