Orphan Drugs in Development for Primary Biliary Cirrhosis: Challenges and Progress

Primary biliary cirrhosis (PBC) is a chronic progressive liver disease that often leads to fibrosis, cirrhosis, and end-stage liver disease. The diagnosis is made when there is evidence of cholestasis and reactivity to the antimitochondrial antibody. The etiology of PBC is poorly understood; however, several lines of evidence suggest an environmental factor that triggers a series of immune-mediated inflammatory reactions in the bile ducts in a genetically susceptible individual. Fatigue and pruritus are the most common symptoms of PBC; however, many patients are diagnosed with PBC only based on laboratory abnormalities. The only pharmacological treatment approved for PBC is ursodeoxycholic acid (UDCA). Several controlled studies have shown that UDCA improves liver biochemistries and prolongs transplant-free survival in PBC patients. Nearly 40% of PBC patients do not respond to UDCA, and those patients are at high risk of serious adverse events, such as the development of liver failure. Therefore, newer alternative therapeutic options for PBC are needed. Obeticholic acid is a first-in-class farnesoid X receptor agonist that has been recently evaluated in PBC patients with inadequate response to UDCA, and demonstrated beneficial results in improving liver biochemistries. Several other agents (fibrates and glucocorticoids) have been previously examined in PBC patients with inadequate response to UDCA, and preliminary results showed biochemical improvement. However, large-scale controlled clinical trials are needed to determine the long-term effects of fibrates and glucocorticoids on the clinical outcomes of PBC. Clinical trials of NGM282 (a fibroblast growth factor-19 analog) and Abatacept (a fusion protein composed of the Fc portion of immunoglobulin G1 fused to CTLA4) are currently underway.