Recognizing Inadequate Response to First-Line Therapy in PBC

Key Takeaways:

• Roughly 40 percent of patients with primary biliary cholangitis (PBC) have an inadequate biochemical response to first-line ursodeoxycholic acid (UDCA) and remain at elevated risk of progression to cirrhosis and liver failure.
• Response is assessed about 12 months after starting UDCA using alkaline phosphatase (ALP) and total bilirubin; validated criteria and continuous risk scores translate those values into an individualized prognosis.
• An inadequate response is a decision point, not an endpoint – it should prompt risk re-estimation and consideration of guideline-recognized second-line therapy.

UDCA at 13 to 15 mg/kg/day is the established first-line therapy for PBC, and patients who achieve a good biochemical response on it have a transplant-free survival that approaches an age- and sex-matched population.^1,2

A substantial minority, however, do not respond adequately, and these patients carry a materially higher risk of progression. Recognizing them early – rather than continuing first-line therapy indefinitely on the assumption that it is working – is the pivot point of modern PBC management.

The biochemistry that predicts outcome

Two routine values carry most of the prognostic weight in PBC. Total bilirubin is the single strongest predictor of survival and anchors every validated prognostic model, while ALP reflects the activity of cholestatic injury. An on-treatment ALP below twice the upper limit of normal is a marker of treatment response.²

Because the magnitude of ALP and bilirubin elevation tracks with the risk of progression, the two together form the backbone of response assessment once UDCA is underway.^1,2

Defining inadequate response at 12 months

Guidelines recommend assessing biochemical response approximately 12 months after UDCA initiation. Several validated binary criteria define an adequate response; among the most widely used are the Paris II definition – ALP and aspartate aminotransferase each below 1.5 times the upper limit of normal with a normal bilirubin – and the Toronto definition, ALP at or below 1.67 times the upper limit of normal, though more recent data suggest that more stringent targets, including ALP normalization and bilirubin below 0.6 times the upper limit of normal, are associated with better outcomes.^1-3

Applying these definitions, up to 40 percent of patients are classified as inadequate responders, a group with a higher long-term risk of liver transplantation or liver-related death.^1,2

Quantifying risk beyond binary criteria

Continuous risk scores refine the binary picture. The GLOBE score combines age at the start of therapy with bilirubin, albumin, ALP, and platelet count after 1 year of UDCA and predicts transplant-free survival with good discrimination. A score above 0.30 identifies patients whose survival falls below that of a matched healthy population.⁴

The UK-PBC risk score uses baseline albumin and platelets together with ALP, transaminases, and bilirubin at 12 months to estimate the risk of end-stage liver disease at 5, 10, and 15 years, with areas under the curve above 0.90 in validation. Both tools convert routine laboratory values into an individualized prognosis that frames the second-line conversation.^4,5

Acting on an inadequate response

An inadequate response should trigger reassessment rather than reassurance. After confirming adherence and excluding contributing factors, an inadequate responder warrants the addition of second-line therapy to UDCA.^1,2

In the United States, the available second-line agents are the peroxisome proliferator-activated receptor (PPAR) agonists – elafibranor, a dual PPAR-alpha/delta agonist, and seladelpar, a selective PPAR-delta agonist, both granted accelerated approval in 2024 – with off-label fibrates as an additional PPAR-targeted option.^6-8

The farnesoid X receptor (FXR) agonist obeticholic acid was the first approved second-line agent, but it was withdrawn from the US market in late 2025 after its confirmatory trial failed to verify clinical benefit and showed serious liver injury, including in patients with early-stage disease.⁹

Identifying the inadequate responder at 12 months – and re-estimating risk at each subsequent visit – keeps patients moving toward the therapy most likely to protect long-term liver function.^1,2