What is the role of Rituximab (rituximab) in treating autoimmune pancreatitis?

Rituximab for Autoimmune Pancreatitis

Rituximab is an effective treatment for relapsing type 1 autoimmune pancreatitis (AIP) that provides rapid clinical, biological, and morphological response with sustained remission after discontinuation. 1

Types of Autoimmune Pancreatitis

• Type 1 AIP: Pancreatic manifestation of IgG4-related disease with multi-organ involvement
• Type 2 AIP: Pancreas-specific disease not related to IgG4, often associated with inflammatory bowel disease

Standard Treatment Algorithm

1. First-line therapy: Oral corticosteroids (prednisone/prednisolone)

   • Initial dose: 40 mg daily or 0.6-0.8 mg/kg daily for 4 weeks 2
   • Lower doses (10-20 mg daily) may be effective in some patients, particularly elderly with comorbidities 2

2. For relapsing disease:

   • Rituximab is the preferred option for relapsing type 1 AIP 1, 3
   • Alternative options include azathioprine, 6-mercaptopurine, or mycophenolate mofetil 2, 4

Rituximab Protocol for AIP

Induction Therapy:

• 375 mg/m² intravenously weekly for 4 weeks 1 OR
• 1000 mg on days 0 and 14 5

Maintenance Therapy:

• 500 mg intravenously every 6 months for 2 years 1 OR
• Two doses of 1000 mg each (15 days apart) repeated after 6 months 5

Efficacy of Rituximab in AIP

• Response rate: 94% in relapsing AIP, significantly better than immunomodulator drugs (67%) 3
• Remission duration: No relapses during follow-up of approximately 63 months in one study 1
• Relapse pattern: No disease relapse observed in the first year after the last infusion, with 80% probability of relapse between 1-3 years 5

Monitoring During Treatment

• Clinical examinations
• Biological tests (including serum IgG4 levels)
• Imaging (PET scan) to assess pancreatic and extra-pancreatic involvement
• Immunomonitoring of lymphocyte CD19+ 1

Benefits of Rituximab

1. Deep and persistent reduction in serum IgG4 levels
2. Resolution of both pancreatic and extra-pancreatic hypermetabolic signals on PET scan
3. Effective depletion of B lymphocyte CD19+ cells 1
4. Better tolerance compared to immunomodulator drugs 3

Cautions and Adverse Effects

• Infusion reactions (can be managed with premedication)
• Risk of infections
• Potential for hypogammaglobulinemia
• Rare but serious adverse events: progressive multifocal leukoencephalopathy, hepatitis B reactivation 6

When to Consider Rituximab

1. Relapsing disease after corticosteroid therapy
2. Multiple organ involvement
3. Intolerance to other immunosuppressive agents
4. Need for steroid-sparing therapy, particularly in patients with diabetes or osteoporosis 2

Rituximab has emerged as a valuable treatment option for relapsing type 1 AIP, demonstrating superior efficacy compared to conventional immunomodulators. Its ability to provide sustained remission makes it an important therapeutic consideration, particularly for patients with multiple relapses or multi-organ involvement.