About PBC

What is Primary Biliary Cholangitis (PBC)?

PBC is a rare, chronic, autoimmune liver disease that progressively destroys the liver’s bile ducts. It mostly affects middle-aged women (10 women for every one man impacted), but it can be faster progressing and less responsive to therapy in men and younger women.1 Estimates indicate that PBC affects nearly 1 in 1,000 women over the age of 40.2

Bile ducts are tiny tubes that form the biliary tree, a network that collects and drains bile from the liver. Bile is a detergent-like substance composed of bile acid salts, cholesterol, and phospholipids. Bile collected from the liver is stored in the gall bladder and released into the small intestine in response to eating. In the intestine, its detergent-like properties combined with pancreatic juices help dissolve and digest food. In PBC, immune and inflammatory degeneration of bile ducts impairs the formation and flow of bile leading to the buildup of toxic bile acids.

PBC is progressive, with reinforcing cycles of cell death and regeneration, inflammation, and fibrosis (scarring). Complications include cirrhosis (excessive scarring), bleeding, accumulation of fluid in the abdomen, nervous system disorders, and sometimes liver failure. PBC has no cure, but medication can improve elevated liver enzymes and biomarkers that are associated with liver-related complications, liver transplantation, and death.

People living with PBC may experience symptoms like fatigue and severe itching (pruritus). As the disease progresses and damages the liver, patients may experience yellowing of the skin, dry eyes and mouth, and pain in the upper right abdomen. The goal of treatment is to improve patient quality of life and overall liver health. Treatments are often judged by their ability to improve results on laboratory tests that reflect impaired bile flow or cholestasis, including:

  • Alkaline phosphatase (ALP)
  • Bilirubin
  • Markers of liver injury, like alanine aminotransferase (ALT) and aspartate aminotransferase (AST)

Normalizing these markers has been shown to help significantly reduce the risk for PBC disease progression, liver cirrhosis, liver transplantation, and mortality.3

Unfortunately, up to 40% of patients do not have an adequate response to current first-line treatment and up to 50% of patients have an inadequate response to current approved second-line treatment, or they struggle with medication side effects such as increased itching.2 That is why CymaBay is dedicated to delivering alternative treatment options.

PBC Facts

About three-quarters of women impacted are over age 50.2

Fibrosis (scarring) of the liver and decreased blood flow may occur.

When affected, men and younger women are less responsive to therapy and at higher risk for progression.

May progress to cirrhosis (late-stage scarring) and, in some cases, liver failure.

Causes bile duct degeneration and destruction, leading to impaired bile flow and buildup of toxic bile acids.

Symptoms include fatigue and itchy skin (pruritis), dry eyes and mouth, yellowing of the skin and pain in the upper right abdomen.

1. Carbone M, Mells GF, Pells G, Dawwas MF, Newton JL, Heneghan MA, et al. Sex and age are determinants of the clinical phenotype of primary biliary cirrhosis and response to ursodeoxycholic acid. Gastroenterology. 2013;144(3):560-9 e7; quiz e13-4.

2. Trivedi PJ, Hirschfield GM. Recent advances in clinical practice: epidemiology of autoimmune liver diseases Gut 2021;70:1989-2003.

3. Mei Lu 1, Yueren Zhou et al. Clin Gastroenterol Hepatol. 2018 Aug;16(8):1342-1350.e1. doi: 10.1016/j.cgh.2017.12.033. Epub 2017 Dec 23

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