What is the recommended weight‑based dosing and monitoring plan for Odevixibat in children ≥3 months with progressive familial intrahepatic cholestasis or Alagille syndrome?

Odevixibat Dosing and Monitoring in Pediatric Cholestatic Disease

Recommended Dosing

For Progressive Familial Intrahepatic Cholestasis (PFIC): Start odevixibat at 40 mcg/kg once daily in children ≥3 months of age, with option to escalate to 120 mcg/kg once daily if inadequate response after 3 months 1.

For Alagille Syndrome (ALGS): Use odevixibat 120 mcg/kg once daily in children ≥12 months of age 1, 2.

Dosing Algorithm by Indication

PFIC (≥3 months old):

• Initial dose: 40 mcg/kg once daily orally
• Assess response at 3 months based on pruritus reduction and serum bile acid levels
• If inadequate response: Escalate to 120 mcg/kg once daily
• Maximum dose: 120 mcg/kg/day 1, 3

ALGS (≥12 months old):

• Start directly at 120 mcg/kg once daily
• No dose titration required based on current evidence 1, 2

The evidence supporting these dosing recommendations comes from the pivotal FDA approval trial in PFIC, which demonstrated that both 40 mcg/kg and 120 mcg/kg doses reduced scratching scores compared to placebo (35.4% and 30.1% of assessments showing no/minimal scratching versus 13.2% for placebo) 3. For ALGS, the ASSERT trial specifically evaluated 120 mcg/kg dosing and demonstrated significant reduction in scratching scores (LS mean change -1.7 vs -0.8 for placebo, p=0.0024) and serum bile acids (LS mean change -90 μmol/L vs +22 μmol/L for placebo, p=0.0012) 2.

Monitoring Plan

Baseline Assessment

• Pruritus severity: Use caregiver-reported scratching scores (PRUCISION or similar validated instrument)
• Serum bile acids: Fasting levels
• Liver function tests: ALT, AST, bilirubin, alkaline phosphatase
• Fat-soluble vitamins: Vitamins A, D, E, K levels and INR
• Hepatotoxicity markers: Baseline transaminases 1

Ongoing Monitoring Schedule

Weeks 1-4:

• Monitor for diarrhea (most common adverse effect, occurring in 29% of ALGS patients) 2
• Assess tolerability and adherence

Months 1-3:

• Pruritus assessment: Monthly caregiver-reported scratching scores
• Serum bile acids: At 6-8 weeks and 12 weeks
• Liver function tests: Monthly
• For PFIC patients on 40 mcg/kg: Assess response at 3 months to determine if dose escalation needed

Months 3-6:

• Pruritus assessment: Every 4-6 weeks
• Serum bile acids: At weeks 20 and 24 (average these values for response assessment) 2
• Liver function tests: Every 4-6 weeks
• Fat-soluble vitamins: At 6 months

Beyond 6 months:

• Pruritus assessment: Every 2-3 months
• Serum bile acids: Every 3 months
• Liver function tests: Every 3 months
• Fat-soluble vitamins: Every 6 months
• Monitor for signs of hepatotoxicity throughout treatment 1

Response Criteria

Adequate response defined as:

• Reduction in scratching scores by ≥1 point on 0-4 scale
• Reduction in serum bile acids by ≥50% from baseline or to <70 μmol/L
• Improvement in sleep quality and quality of life measures

Inadequate response in PFIC:

• If on 40 mcg/kg with <50% reduction in bile acids or minimal pruritus improvement at 3 months, escalate to 120 mcg/kg 3

Dose Modifications for Adverse Reactions

For diarrhea (most common adverse effect):

• Mild: Continue treatment, provide supportive care
• Moderate-severe or persistent: Consider temporary dose reduction or interruption
• Resume at lower dose once resolved 1

For hepatotoxicity:

• Monitor ALT/AST elevations closely
• If transaminases >5x upper limit of normal: Interrupt treatment
• May resume at lower dose once normalized 1

For fat-soluble vitamin deficiency:

• Supplement appropriately with vitamins A, D, E, K
• Monitor levels every 3-6 months
• Adjust supplementation as needed 1

Administration Instructions

• Administer once daily in the morning
• Give with food to improve tolerability
• Capsules can be opened and contents mixed with soft food or liquid for patients unable to swallow capsules
• Critical: Separate from bile acid binding resins (cholestyramine, colesevelam) by at least 4 hours before or 4 hours after odevixibat, as these can reduce odevixibat absorption 1

Important Clinical Considerations

Genotype matters in PFIC: The 2024 EASL guidelines note that patients with biallelic protein-truncating mutations (PPTMs) in BSEP deficiency were excluded from odevixibat trials due to theoretical concerns and lack of response to surgical bile acid interruption 4. Odevixibat is most effective in PFIC patients with missense mutations 4.

Liver transplantation remains definitive: While odevixibat improves pruritus and reduces serum bile acids, the guidelines emphasize that liver transplantation remains the standard of care for progressive cholestasis in both ALGS and PFIC 4. Odevixibat should be viewed as a bridge therapy or quality-of-life intervention, not a cure.

Real-world effectiveness: A systematic review found no consistent dose-response relationship across all IBATi trials, suggesting significant inter-patient variability in response 5. This underscores the importance of individualized monitoring and dose adjustment based on clinical response rather than rigid adherence to maximum dosing.

Duration of benefit: The ASSERT trial in ALGS demonstrated sustained efficacy through 24 weeks 2, and the ICONIC trial with maralixibat (another IBAT inhibitor) showed durable effects at 204 weeks 4, suggesting long-term benefit is achievable.