Primary biliary cholangitis (PBC) is an immune-mediated liver disease characterized by chronic inflammation of the intrahepatic bile ducts, causing progressive ductopenia, cholestasis, and if not effectively treated, leading to fibrosis, cirrhosis and liver failure. Nowadays almost all patients with PBC are diagnosed at an early disease stage and receive treatment with ursodeoxycholic acid (UDCA) which is currently the only drug approved for the treatment of patients with PBC. However, approximately 20% to 30% (up to \>50% in patients presenting under the age of 40 years) still does not have a benefit from UDCA and has a reduced prognosis as compared to healthy individuals. Major steps forwards in the field of PBC have been done in the last decade, however there are still significant areas of unmet clinical need in PBC: the lack of knowledge on etiopathogenesis; a poor understanding of disease sub-phenotypes; the lack of biomarkers of disease progression that allow risk stratification needed in clinical management and trials design, among the others. In the current evolving research landscape with the availability of the -omics technologies generating libraries of genome-wide data, metabolomics and proteomics data, among the others, the prospects of discovering the gene and molecular underpinnings of PBC are more promising than ever. Scientists envision an era of "personalized medicine" when more and more people will obtain their own genetic and metabolic maps, enabling them to identify their status as carriers of specific risk profiles.

Based on these premises, the current project aims to build up a research, nation-wide infrastructure (around 60 Italian participating centres will be involved) to study the biology of PBC and, in particular, to explore why a significant group of, typically young patients fail primary therapy with UDCA, placing them at risk of developing progressive disease and needing liver transplantation (LT). The investigators will recruit patients and organise the collection of important clinical information and laboratory investigation, together with biological samples. Data will be collected in the form of electronic Case Report Forms (REDCap cloud) that will be completed by clinicians at baseline and thereafter on an annual basis. The clinical information will allow us to identify patients' clinical profiles. The biological samples will allow to understand key aspects of people's make up, including patient genes and the way their immune system works, and the differences in make up between people with different clinical phenotypes.

This research infrastructure would represent an invaluable resource for successful translational research in this field. Specifically, it would serve investigators conducting research; clinicians treating patients; epidemiologists gathering demographic data; and the drug and device industry seeking new markets. It also can represent a necessary infrastructure for the implementation of the European Reference Networks (ERN) for rare diseases, main pillars of the current EU policy framework on National Plans for research and development. The Italian PBC database would also be crucial for drug development, specifically to assess the feasibility of clinical trials, to facilitate the planning of appropriate clinical trials, to support the enrolment of patients and to assess the impact of new interventions.