This study will test a drug called A3907 to see how safe and tolerated it is for treating people with Primary Sclerosing Cholangitis (PSC). Detailed Description: The primary goal of this study in participants with PSC with and without a Clinically Relevant Stricture (CRS) who are treated with A3907 is to assess the safety and tolerability of A3907 following repeat doses. Secondary goals include evaluation of the pharmacokinetic properties of A3907 (the study of how the body interacts with A3907 for the entire duration of exposure) and changes in safety parameters via laboratory testing such as liver enzymes, bile acid levels and markers of bile acid synthesis.