What is the recommended dose of rituximab (Rituxan) for treating Neuromyelitis Optica (NMO) relapse?

Rituximab Dosing for Neuromyelitis Optica (NMO) Relapse

For treating NMO relapse, rituximab should be administered at a dose of 375 mg/m² weekly for 4 weeks, or alternatively as two 1000 mg doses given 2 weeks apart. 1, 2

Evidence-Based Dosing Regimens

Rituximab has emerged as an effective treatment for neuromyelitis optica spectrum disorders (NMOSD), with two primary dosing regimens showing clinical efficacy:

1. Standard Protocol (Most Evidence):

   • 375 mg/m² intravenously once weekly for 4 consecutive weeks 1, 3, 4
   • This regimen was used in the RIN-1 randomized controlled trial, which demonstrated complete prevention of relapses in AQP4 antibody-positive NMOSD patients 1

2. Alternative Protocol:

   • 1000 mg given on days 1 and 15 (two doses, two weeks apart) 5
   • This regimen showed a significant reduction in annual relapse rate from 0.7 to 0.4 in one study 5

Monitoring and Maintenance Considerations

CD19+ B-Cell Monitoring

• Monthly CD19+ B-cell counts are essential after initial treatment to identify early B-cell repopulation 2
• Retreatment should be considered when CD19+ B-cells reach ≥1-2% of lymphocytes 3, 2

Maintenance Therapy Options

• After initial induction therapy, maintenance regimens include:
  • 1000 mg every 6 months 5
  • 375 mg/m² every 6 months 3
  • Personalized retreatment based on CD19+ B-cell repopulation 2

Pre-Treatment Screening

Before initiating rituximab therapy, patients should undergo:

• Baseline immunoglobulin levels (IgG, IgM, IgA)
• Hepatitis B and C antibody testing
• Screening for latent tuberculosis 6

Clinical Efficacy

Rituximab has demonstrated significant efficacy in NMOSD:

• Complete prevention of relapses over 72 weeks in AQP4 antibody-positive patients in the RIN-1 randomized controlled trial 1
• Reduction in annual relapse rate from 1.15 to 0.46 across multiple dosing regimens 5
• Improvement in disability scores (EDSS) in most patients 3, 4

Safety Considerations

• Serious adverse events reported in clinical trials include infections, fractures, and rare cases of malignancy 1
• Progressive multifocal leukoencephalopathy has been reported in rheumatic patients treated with rituximab 6
• Regular monitoring for infections and periodic assessment of immunoglobulin levels is essential 6

Clinical Algorithm for NMO Relapse Treatment

1. Confirm diagnosis: Verify AQP4 antibody status and clinical/radiological evidence of NMO relapse
2. Select dosing regimen:
   • First choice: 375 mg/m² weekly for 4 weeks
   • Alternative: 1000 mg on days 1 and 15
3. Implement monitoring protocol:
   • Monthly CD19+ B-cell counts
   • Regular clinical assessment for relapse symptoms
4. Plan maintenance therapy based on B-cell repopulation or at fixed intervals (every 6 months)