What is the current evidence for using B‑cell‑depleting therapy (rituximab) in adults with biopsy‑proven IgA nephropathy who have persistent proteinuria ≥1 g/day despite maximally tolerated angiotensin‑converting enzyme inhibitor or angiotensin receptor blocker therapy?

B-Cell Directed Therapy (Rituximab) is NOT Currently Recommended for IgA Nephropathy

Based on current guideline evidence and the highest quality randomized controlled trial, rituximab should not be used as standard therapy for IgA nephropathy with persistent proteinuria ≥1 g/day despite maximally tolerated ACE-I/ARB therapy. The 2012 KDIGO guidelines do not recommend rituximab for IgAN, and the most rigorous RCT demonstrated no benefit 1.

Current Guideline-Based Treatment Algorithm

First-Line Therapy (Strongly Recommended)

• ACE-I or ARB therapy is the cornerstone treatment when proteinuria is ≥1 g/day, with uptitration as tolerated based on blood pressure (Grade 1B recommendation) 2, 3
• Target blood pressure: <130/80 mmHg if proteinuria <1 g/day; <125/75 mmHg if proteinuria ≥1 g/day 2
• Continue optimized supportive care for 3-6 months before considering immunosuppression 2

Second-Line Therapy (If Persistent Proteinuria ≥1 g/day)

• Corticosteroids are suggested for patients with persistent proteinuria ≥1 g/day despite 3-6 months of optimized supportive care AND eGFR ≥50 mL/min/1.73 m² (Grade 2C recommendation) 2
• Recommended regimen: 6-month course of alternating IV methylprednisolone (1g for 3 days) followed by oral prednisone 0.8-1 mg/kg/day for 2 months, then tapered by 0.2 mg/kg/day monthly for 4 months 2

What NOT to Use

• Rituximab is NOT recommended - no guideline recommendation exists 2, 3
• MMF is NOT recommended (Grade 2C against) 2
• Cyclophosphamide or azathioprine combined with corticosteroids is NOT recommended unless crescentic IgAN with rapidly deteriorating function (Grade 2D against) 2

Evidence Against Rituximab in IgAN

The Definitive Negative Trial

The 2017 randomized controlled trial by Lafayette et al. 1 provides the highest quality evidence:

• 34 patients with biopsy-proven IgAN, proteinuria >1 g/day, eGFR <90 mL/min/1.73 m², on stable ACE-I/ARB therapy
• Primary outcomes: Change in proteinuria and eGFR over 1 year
• Results:
  • Rituximab effectively depleted B cells but did NOT reduce proteinuria compared to baseline or control group
  • No change in eGFR in either group
  • Only 3 patients in each group achieved ≥50% reduction in proteinuria
  • Failed to reduce galactose-deficient IgA1 or anti-galactose-deficient IgA1 antibodies - the key pathogenic molecules in IgAN

This trial demonstrates that despite effective B-cell depletion, rituximab does not address the fundamental pathogenic mechanisms of IgAN at this stage and severity of disease.

Why Rituximab Doesn't Work in IgAN

The pathophysiology explains the failure: IgAN is driven by galactose-deficient IgA1 and immune complex formation. Rituximab depletes B cells but fails to reduce these pathogenic antibodies that are already circulating and being produced by long-lived plasma cells (which lack CD20 and are not targeted by rituximab) 1.

Limited Exceptions Where Rituximab Has Been Reported

Rituximab may have a role only in highly specific IgAN subtypes that are NOT the typical presentation:

1. IgAN with Minimal Change Disease (MCD-IgAN)

• Small case series suggest benefit in steroid-dependent or frequently relapsing MCD-IgAN 4, 5, 6
• This represents a distinct pathophysiologic entity where the MCD component (podocyte dysfunction) may be B-cell mediated
• This is NOT standard IgAN - it's a rare overlap syndrome

2. IgA Vasculitis with Severe Nephritic-Nephrotic Syndrome

• Very limited case reports in patients with crescentic features and nephritic-nephrotic syndrome 7
• Used as salvage therapy when conventional immunosuppression fails
• Not evidence-based; purely anecdotal

3. Post-Transplant IgAN

• Emerging data suggest possible benefit, but evidence remains heterogeneous and limited to small retrospective studies 8
• Not standard of care

Updated 2025 KDIGO Guideline Context

The 2025 KDIGO guideline update 9 introduces newly approved therapies that target different pathogenic mechanisms:

• Nefecon (targeted-release budesonide) - targets gut-associated lymphoid tissue where galactose-deficient IgA1 is produced
• Sparsentan (dual endothelin A/angiotensin II receptor antagonist)
• Iptacopan (complement factor B inhibitor)
• Atrasentan (endothelin A receptor antagonist)
• Sibeprenlimab (APRIL inhibitor)

Notably, rituximab is NOT mentioned among recommended or emerging therapies in the 2025 guideline 9, 10.

Clinical Pitfalls to Avoid

1. Do not use rituximab based on its success in other glomerular diseases (membranous nephropathy, minimal change disease) - IgAN has different pathophysiology
2. Do not assume B-cell depletion equals therapeutic benefit - the Lafayette trial proved this assumption wrong 1
3. Do not delay corticosteroid therapy in appropriate candidates (proteinuria ≥1 g/day, eGFR ≥50 mL/min/1.73 m²) by trying rituximab first
4. Do not confuse IgAN with MCD-IgAN - they require different approaches

Safety Considerations from FDA Label

If rituximab were to be considered off-label (which is not recommended), be aware of significant risks 11:

• Infusion-related reactions (77% with first infusion)
• Serious infections (bacterial, viral, fungal)
• Progressive multifocal leukoencephalopathy
• Hepatitis B reactivation
• Severe mucocutaneous reactions
• Prolonged B-cell depletion and hypogammaglobulinemia

These risks are not justified given the lack of efficacy in standard IgAN.