What are the essential design elements—including inclusion criteria (biopsy‑confirmed IgA nephropathy, exclusion of secondary causes, proteinuria ≥0.5 g/day after ≥90 days of optimized ACE inhibitor or ARB therapy, eGFR ≥30 mL/min/1.73 m²), stratification factors, primary renal endpoints, follow‑up duration, safety monitoring, and population diversity—when planning a clinical trial for IgA nephropathy?

Research Considerations in IgA Nephropathy Clinical Trials

When designing a clinical trial for IgA nephropathy, enrollment should target high-risk patients with biopsy-confirmed disease, proteinuria ≥1 g/day (ideally ≥0.75 g/day) despite ≥90 days of optimized RAS blockade, and eGFR ≥30 mL/min/1.73 m², while the primary endpoint should focus on proteinuria reduction as a validated surrogate marker for kidney outcomes. 1, 2

Essential Inclusion Criteria

Diagnostic Requirements

• Biopsy-confirmed IgA-dominant glomerulonephritis with MEST-C scoring to characterize disease severity and exclude variant forms 1
• Exclusion of secondary causes is mandatory, including IgA vasculitis, infection-related IgA-dominant glomerulonephritis, liver cirrhosis, inflammatory bowel disease, autoimmune diseases, and viral infections (HIV, hepatitis) 1

Risk Stratification Entry Criteria

• Proteinuria threshold: ≥1 g/day (or ≥0.75 g/day for higher-risk populations) after at least 90 days of maximally tolerated ACE inhibitor or ARB therapy 1
• eGFR requirement: ≥30 mL/min/1.73 m² to balance inclusion of at-risk patients while avoiding those with advanced CKD where treatment effects may be limited 1, 3
• Optimized supportive care run-in period: Minimum 90 days (3 months) of stable, maximally tolerated RAS blockade with blood pressure control before randomization 1

Exclusion of Variant Forms

Trials should exclude patients with IgA deposition with minimal change disease, IgAN with acute kidney injury, and IgAN with rapidly progressive glomerulonephritis, as these require distinct management approaches 1

Stratification Factors

Randomization should be stratified by baseline proteinuria level (e.g., 1-2 g/day vs. >2 g/day), eGFR category (e.g., ≥50 vs. 30-49 mL/min/1.73 m²), and geographic region to account for ethnic differences in disease behavior and treatment response. 3, 2

• Geographic/ethnic stratification is critical given documented differences between Chinese, Japanese, and non-Asian populations in response to therapies like mycophenolate mofetil and tonsillectomy 1
• Baseline kidney function (eGFR categories) affects both treatment efficacy and safety, particularly for immunosuppressive agents 1
• Concomitant SGLT2 inhibitor use should be considered as a stratification factor or separate exploratory stratum given emerging evidence of benefit 3, 2

Primary and Secondary Endpoints

Primary Renal Endpoints

• Proteinuria reduction (change in 24-hour urine protein-to-creatinine ratio from baseline to week 36) is the most validated surrogate endpoint, with a treatment target of <1 g/day, ideally <0.5 g/day or <0.3 g/day 1, 3, 2
• eGFR slope (change from baseline to week 132-136) provides complementary information on kidney function preservation 3, 2

Secondary Endpoints

• Composite kidney outcome: Time to ≥30% sustained eGFR decline, kidney failure (dialysis, transplantation), or kidney disease-related death 4, 3
• Complete or partial remission rates: Proteinuria <0.3 g/day (complete) or <0.5 g/day (partial) maintained for ≥6 months 4
• Histologic endpoints in select trials with repeat biopsies to assess MEST-C score changes 1, 2

Follow-Up Duration

A minimum follow-up of 132-136 weeks (approximately 2.5-3 years) is necessary to adequately assess both proteinuria response and eGFR trajectory, with a 4-week washout period to evaluate durability of effect. 3, 2

• Shorter-term proteinuria endpoints (36 weeks) can serve as primary outcomes with longer-term kidney function outcomes as key secondary endpoints 3
• The slow progression of IgAN necessitates extended follow-up to capture meaningful differences in hard kidney outcomes 5, 6

Safety Monitoring

Immunosuppression-Related Toxicity

Trials involving immunosuppressive agents must implement rigorous safety monitoring, particularly for patients with eGFR <50 mL/min/1.73 m², diabetes, obesity (BMI >30 kg/m²), latent infections, or advanced age. 1

• Infection screening: Mandatory baseline testing for tuberculosis, HIV, hepatitis B and C before enrollment 1
• Metabolic monitoring: Regular assessment for hyperglycemia, weight gain, bone density changes, and psychiatric symptoms with glucocorticoid-based regimens 1
• Cardiovascular safety: Blood pressure monitoring and assessment for fluid retention, particularly with endothelin receptor antagonists 3

Kidney-Specific Safety

• Acute eGFR decline: Monitor for initial hemodynamic changes with RAS inhibitors, SGLT2 inhibitors, or endothelin antagonists 3, 2
• Hyperkalemia surveillance: Regular serum potassium monitoring, especially with combination RAS blockade 7

Population Diversity Considerations

Enrollment should reflect global disease distribution with adequate representation from East Asian populations (where incidence is highest), while ensuring sufficient diversity to assess treatment effects across ethnic groups. 6, 3

• Geographic distribution: The ALIGN trial enrolled across 20 countries to ensure generalizability 3
• Age range: Mean age at diagnosis is 34-45 years; trials should include young adults through middle age 6
• Sex representation: Approximately 40-60% female enrollment reflects disease demographics 3

Contemporary Trial Design Elements

Emerging Combination Therapy Paradigm

Modern IgAN trials should consider dual-mechanism approaches: (1) therapies targeting pathogenic IgA production (targeted-release budesonide, systemic corticosteroids) combined with (2) therapies managing nephron loss consequences (RAS inhibitors, SGLT2 inhibitors, dual endothelin-angiotensin receptor blockers). 2, 5

• Exploratory strata for SGLT2 inhibitor combinations are increasingly important given their integration into standard care 3, 2
• Novel mechanism evaluation: Trials of complement inhibitors, anti-B-cell strategies, and APRIL/BAFF antagonists represent the evolving therapeutic landscape 5, 8, 2

Risk Prediction Tools

• International IgAN Prediction Tool should be used for baseline risk stratification, though it cannot predict treatment-specific effects 1
• Clinical and histologic data at biopsy provide complementary prognostic information 1

Critical Pitfalls to Avoid

• Insufficient run-in period: Enrolling patients before 90 days of optimized supportive care may dilute treatment effects by including responders to RAS blockade alone 1
• Overly restrictive eGFR cutoffs: Excluding patients with eGFR 30-50 mL/min/1.73 m² eliminates a high-risk population that may benefit most 3, 2
• Ignoring ethnic differences: Failing to stratify by ethnicity may obscure population-specific treatment responses 1
• Inadequate safety monitoring: Underestimating immunosuppression risks, particularly in patients with eGFR <50 mL/min/1.73 m², can lead to preventable serious adverse events 1