What are the dosing and treatment guidelines for atrasentan in adult patients with primary IgA nephropathy at high risk of progression (proteinuria ≥1 g/24 h, eGFR ≥ 30 mL/min/1.73 m²) who are on a stable ACE inhibitor or ARB regimen?

Atrasentan Treatment Guidelines and Dosing for IgA Nephropathy

Atrasentan 0.75 mg orally once daily is the recommended dose for adults with primary IgA nephropathy who have proteinuria ≥1 g/24h, eGFR ≥30 mL/min/1.73 m², and are on maximally tolerated stable ACE inhibitor or ARB therapy for at least 90 days.

Patient Selection Criteria

Before initiating atrasentan, ensure patients meet these specific requirements 1, 2, 3:

• Biopsy-proven primary IgA nephropathy
• Proteinuria ≥1 g/24 hours (or UPCR ≥1 g/g)
• eGFR ≥30 mL/min/1.73 m²
• Stable, maximally tolerated RAS inhibitor (ACEi or ARB) for ≥90 days
• Blood pressure optimized to target <120/70 mmHg 1

The 2025 KDIGO guideline suggests atrasentan for patients at risk of progressive kidney function loss (Grade 2B recommendation) 1. This represents a significant evolution from the 2021 guideline, which only mentioned atrasentan as an investigational agent 4.

Dosing Regimen

Standard dose: 0.75 mg orally once daily 2, 3

• Continue treatment for 132 weeks (approximately 2.5 years) based on the ALIGN trial protocol 2, 3
• No dose adjustments are specified in current evidence for renal impairment down to eGFR 30 mL/min/1.73 m²
• Atrasentan replaces the RAS inhibitor when using sparsentan, but is added to RAS inhibitor therapy when using atrasentan alone 1

Clinical Efficacy

The ALIGN trial demonstrated robust proteinuria reduction 2:

• 38.1% reduction in proteinuria at 36 weeks with atrasentan versus 3.1% with placebo
• Between-group difference of 36.1 percentage points (95% CI: 26.4-44.6%; P<0.001)
• 75.7% of patients achieved ≥30% proteinuria reduction at 6 months

This magnitude of proteinuria reduction is clinically meaningful, as proteinuria <1 g/day is associated with improved kidney outcomes in IgA nephropathy 4, 5.

Monitoring Requirements

Baseline Assessment

• 24-hour urine protein or UPCR
• Serum creatinine and eGFR
• Blood pressure
• Hemoglobin/hematocrit
• Serum potassium
• Volume status assessment

Follow-up Monitoring 2, 3

Week 2-4 after initiation:

• Blood pressure (watch for fluid retention)
• Serum creatinine and potassium
• Volume status (weight, edema assessment)

Week 12:

• Repeat proteinuria measurement (24-hour urine or UPCR)
• Blood pressure
• Hemoglobin (monitor for anemia) 6

Week 36 and ongoing:

• Proteinuria assessment every 3-6 months
• eGFR monitoring per standard CKD guidelines 7
• Hemoglobin monitoring (endothelin receptor antagonists can cause anemia) 6

Safety Considerations and Management

Fluid Retention (Most Important Adverse Effect)

Fluid retention occurred in 11.2% of atrasentan patients versus 8.2% with placebo in ALIGN 2. Critically, no cases of cardiac failure or severe edema were reported, and fluid retention did not lead to treatment discontinuation.

Management approach:

• Increase diuretic dose if mild edema develops
• Consider loop diuretics if not already prescribed
• Do NOT discontinue atrasentan for mild fluid retention
• Only discontinue if severe, refractory fluid overload develops

Anemia

Hemoglobin decline has been observed with endothelin receptor antagonists 6:

• Monitor hemoglobin at baseline and every 3 months
• Consider iron supplementation or erythropoiesis-stimulating agents if clinically significant anemia develops
• Evaluate for other causes of anemia in CKD

Contraindications and Precautions

Avoid atrasentan in:

• Decompensated heart failure
• Severe volume overload states
• Pregnancy (teratogenic potential with endothelin receptor antagonists)
• Bilateral renal artery stenosis

Integration with Other IgA Nephropathy Therapies

Combination with SGLT2 Inhibitors

The ALIGN trial included an exploratory stratum of 64 patients receiving SGLT2 inhibitors 3. While specific results are pending, the 2025 KDIGO guideline suggests SGLT2 inhibitors for high-risk IgA nephropathy patients (Grade 2B) 1.

Practical approach:

1. Optimize RAS inhibitor first (≥90 days)
2. Add SGLT2 inhibitor if eGFR ≥20 mL/min/1.73 m² 7, 1
3. Consider adding atrasentan if proteinuria remains ≥1 g/day
4. Monitor carefully for volume status with this triple combination

Comparison with Sparsentan

Key distinction: Sparsentan (dual endothelin A/angiotensin II receptor antagonist) replaces the RAS inhibitor, while atrasentan is added to RAS inhibitor therapy 1.

Choose sparsentan when:

• Patient cannot tolerate maximum RAS inhibitor doses
• Desire for single-agent simplification

Choose atrasentan when:

• Patient well-controlled on current RAS inhibitor
• Concurrent SGLT2 inhibitor use planned
• Patient enrolled in ALIGN trial or similar protocol

Glucocorticoid Therapy

The 2025 KDIGO guideline maintains the 2021 recommendation for 6-9 months of systemic glucocorticoids (0.5-0.8 mg/kg/day, maximum 32 mg/day) for patients with proteinuria >0.75-1 g/day despite optimized supportive care 1.

Sequencing approach:

1. Optimize RAS inhibitor for 90 days minimum
2. Add SGLT2 inhibitor if indicated
3. Consider atrasentan if proteinuria persists ≥1 g/day
4. Reserve glucocorticoids for persistent high-risk disease, recognizing significant toxicity risks 1

Atrasentan may reduce or eliminate the need for glucocorticoids in many patients, given its substantial proteinuria-lowering effect without immunosuppressive toxicity.

Mechanism of Action Context

Atrasentan is a highly selective endothelin A receptor antagonist 8. Endothelin-1 activation drives:

• Mesangial cell proliferation and matrix expansion
• Glomerular inflammation
• Podocyte injury and proteinuria
• Tubulointerstitial fibrosis

Preclinical studies demonstrate that atrasentan reverses gene expression changes related to cell proliferation, proinflammatory signatures, and profibrotic pathways in IgA nephropathy models 8. This mechanistic rationale supports its disease-modifying potential beyond simple hemodynamic effects.

Common Pitfalls to Avoid

1. Starting atrasentan before optimizing RAS inhibition: Patients must be on maximally tolerated RAS inhibitor doses for ≥90 days 1, 3

2. Discontinuing for mild fluid retention: The ALIGN trial showed fluid retention was manageable and did not require treatment discontinuation 2

3. Inadequate blood pressure control: Target <120/70 mmHg must be achieved before adding atrasentan 1

4. Ignoring anemia: Monitor hemoglobin regularly as endothelin receptor antagonists can cause anemia 6

5. Using with sparsentan: These should not be combined; sparsentan already provides endothelin A receptor blockade 1

Duration of Therapy

The ALIGN trial protocol specifies 132 weeks of treatment 2, 3. Long-term continuation beyond this timeframe should be guided by:

• Sustained proteinuria reduction
• Stable or improved eGFR trajectory
• Absence of significant adverse effects
• Individual patient risk-benefit assessment

Given the chronic progressive nature of IgA nephropathy and the favorable safety profile observed in ALIGN, indefinite continuation may be appropriate for responders, though long-term data beyond 132 weeks are not yet available.