What anti‑fibrotic medications are recommended for treating lung fibrosis?

Anti-Fibrotic Medications for Lung Fibrosis

The two FDA-approved anti-fibrotic medications for treating lung fibrosis are nintedanib and pirfenidone, with nintedanib having stronger evidence and a conditional recommendation for progressive pulmonary fibrosis (PPF), while pirfenidone has more limited evidence outside of idiopathic pulmonary fibrosis (IPF).

Primary Treatment Options

Nintedanib (Preferred Agent)

Nintedanib is conditionally recommended for treating PPF in patients who have failed standard management for fibrotic interstitial lung disease (ILD), other than IPF 1. This recommendation is based on the INBUILD trial, which enrolled 663 patients and demonstrated that nintedanib:

• Reduces the annual FVC decline by 107 ml compared to placebo
• Decreases the risk of ILD progression by 2.4-fold
• Shows consistent benefit regardless of radiological UIP pattern or underlying ILD type 1

Mechanism: Nintedanib is an oral intracellular tyrosine kinase inhibitor that blocks pathways involved in fibrogenesis 1.

Pirfenidone (Limited Evidence)

The evidence for pirfenidone in non-IPF progressive fibrotic lung disease is substantially weaker. The guideline committee could not make a firm recommendation for pirfenidone, with 62% voting for a conditional recommendation but 38% abstaining due to insufficient evidence 1. The trials were limited by:

• Only 380 patients with PPF enrolled across studies
• Early termination of one trial due to futility
• Small sample sizes leading to very low-quality evidence 1

For RA-ILD specifically: Pirfenidone may be conditionally added as second-line therapy, particularly in patients with a UIP pattern 2.

Disease-Specific Considerations

For Systemic Autoimmune Rheumatic Disease-Associated ILD (SARD-ILD)

First-line therapy should be immunosuppression (mycophenolate, rituximab, or cyclophosphamide), NOT antifibrotics 2. Antifibrotics are reserved for:

1. Progressive disease despite immunosuppression: Add nintedanib, particularly if progressive fibrosing disease is evident on HRCT 2
2. RA-ILD with progression: Consider adding pirfenidone 2
3. SSc-ILD, MCTD-ILD, RA-ILD with progression: Tocilizumab is an additional option 2

For IPF

Both nintedanib and pirfenidone are established therapies that slow FVC decline and reduce acute respiratory deteriorations 3, 4, 5. Treatment should be initiated early, as FVC decline is linear regardless of baseline lung function 5.

Critical Adverse Effects to Monitor

Nintedanib

The side effect profile is predominantly gastrointestinal 1:

• Diarrhea (2.8× increase)
• Nausea (3.1× increase)
• Vomiting (3.6× increase)
• Weight loss (3.7× increase)
• Elevated liver enzymes (AST 3.2×, ALT 3.6×)
• Dose reduction required in 7.9× more patients
• Treatment discontinuation in 1.9× more patients

Management strategy: Dose adjustment is effective at reducing side effects without compromising efficacy 5. Most patients can tolerate therapy with appropriate management.

Pirfenidone

Common side effects include photosensitivity, gastrointestinal symptoms, and elevated liver enzymes (specific rates not provided in the evidence for PPF populations).

Clinical Algorithm for Treatment Selection

1. Determine if IPF or non-IPF ILD

   • IPF: Either nintedanib or pirfenidone as first-line 3, 4
   • Non-IPF ILD: Proceed to step 2

2. For non-IPF ILD, assess for autoimmune features

   • SARD-ILD present: Start immunosuppression (mycophenolate, rituximab, or cyclophosphamide) 2
   • No autoimmune features: Consider nintedanib if progressive fibrosing phenotype 1

3. Define progression (must have occurred within past year with no alternative explanation):

   • Worsening respiratory symptoms
   • Radiological progression
   • Physiological decline (FVC or DLCO) 1

4. If progression on first-line therapy:

   • Add nintedanib for progressive fibrosing disease 2
   • For RA-ILD: Consider adding pirfenidone 2
   • For SSc-ILD/MCTD-ILD/RA-ILD: Consider tocilizumab 2

Important Caveats

Standard management must be attempted first for non-IPF ILD before initiating antifibrotics 1. Standard management varies by disease but typically includes immunosuppression, antigen remediation, or observation. The exception is IPF, where antifibrotics are first-line.

The evidence base is limited: The INBUILD trial is the primary high-quality evidence for nintedanib in PPF, and no comparable trial exists for pirfenidone in this population 1. The 2022 ATS/ERS/JRS/ALAT guidelines explicitly call for additional research.

Combination therapy is emerging: Recent data suggest upfront combination of nintedanib with anti-inflammatory agents (tacrolimus and prednisolone) may improve outcomes in previously untreated PPF patients, though this requires validation in larger trials 6.