Transforming Primary Sclerosing Cholangitis: From Treatment to Transplantation

Transforming Primary Sclerosing Cholangitis: From Treatment to Transplantation

Summary of CME Lecture by Kris Kowdley, MD, FAASLD

1. Main Clinical Topics Discussed

• Natural history, classification, and pathophysiology of Primary Sclerosing Cholangitis (PSC)
• Prognostic biomarkers and risk stratification models in PSC
• Challenges in clinical trial endpoint development for PSC
• Role of histology, serum fibrosis markers, and advanced imaging in disease monitoring

2. Key Learning Points, Guidelines, and Recommendations

Disease Classification & Pathophysiology

• PSC is divided into small duct and large duct variants; whether small duct PSC is an earlier stage of large duct PSC remains unclear
• No approved medical therapies currently exist for PSC; a major barrier is identifying regulatory-acceptable surrogate endpoints
• Median transplant-free survival is approximately 15–20 years
• PSC-associated IBD is increasingly considered a distinct third IBD subtype — characterized by right-sided predominance, mild endoscopic findings, and frequent backwash ileitis — rather than classic ulcerative colitis or Crohn's disease
• Elevated IgG4 levels in PSC (distinct from IgG4-related cholangiopathy) are associated with poor prognosis

Prognostic Models

• Established models include: Mayo Clinic Model, King's College Model, Amsterdam Oxford Model, and the Presto Model
• The Amsterdam Oxford and Presto models both incorporate: alkaline phosphatase (ALP), platelets, albumin, and bilirubin
• AST:ALT ratio >1 may suggest fibrosis in PSC
• None of these models have been validated with long-term survival data comparable to the Globe PBC or UK PBC scores

Histological Scoring

• Biopsy has significant limitations: 20% of PSC biopsies may be completely normal; substantial sampling and biological variability exists
• Nakanuma scoring system (incorporating fibrosis, inflammation, ductal injury, and ductopenia) may be the preferred histological scoring system for predicting clinical outcomes and potential use as a clinical trial endpoint
• Ishak stages 3–6 vs. 0–2 both independently predicted PSC event-free survival

3. Specific Clinical Data, Statistics, and Study Results Cited

Alkaline Phosphatase as a Biomarker

• Patients with ALP <1.5× ULN had significantly superior long-term transplant-free survival vs. those with ALP >5× ULN
• Optimal prognostic cut-off identified: ALP <1.3× ULN
• In a retrospective study of 366 patients followed for a median of 100 months, 18% reached a PSC-related death or liver transplant endpoint; hazard ratio increased with ALP ranging from 0.5–2.5× ULN
• UDCA vs. placebo (~200 patients, 5-year Scandinavian trial): No survival difference over 14 years regardless of treatment; however, biochemical responders (ALP normalization or >40% reduction at 1 year) had significantly better outcomes irrespective of UDCA use, suggesting ALP response — not UDCA itself — drives prognosis

ELF (Enhanced Liver Fibrosis) Score

• ELF <9.8 vs. ≥9.8 correlated with event-free survival
• ELF delta of 0.19 predicted differences in clinical events
• ELF achieved a negative predictive value of 96% for excluding PSC-related cirrhosis
• FibroTest achieved NPV of 95%; FIB-4 performed least well but remains accessible as a non-proprietary test
• APRI score showed good NPV but poor sensitivity

Histology & Clinical Events (Simusu/Simtuzumab Trials)

• Ishak stage 3–6: Hazard ratio 1.98 for PSC-related clinical events
• ELF score: Hazard ratio 1.3
• Baseline ALP