The purpose of this study is to determine the effectiveness and safety of an investigational drug called volixibat in treating pruritus (itching) in patients with primary biliary cholangitis (PBC). It is believed that the increased circulation of bile acids in patients with PBC leads to itching. Volixibat is a medicine that lowers circulating bile acid levels, and as a result, is also thought to reduce itching associated with PBC. Study procedures include clinic visits for safety evaluations, questionnaire completions, and blood draws. Researchers also want to measure the biomarkers of PBC disease progression. A biomarker is a biological molecule found in blood and other body fluids or tissues that may be a sign of a condition or disease and can be used to predict response to a specific treatment.