Pirfenidone

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Cat Number

API53179138

CAS Number

53179-13-8

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CAS Number

53179-13-8

EINECS

621-260-7

Storage

Store at room temperature

Synonyms

Esbriet; Pirespa; AMR-69; Pirfenidona; Pirfenidonum; 2(1H)-Pyridinone, 5-methyl-1-phenyl-; 5-Methyl-1-phenyl-2(1H)-pyridone

Molecular Formula

C12H11NO

Molecular Weight

185.22

Smiles

CC1=CN(C(=O)C=C1)C2=CC=CC=C2

Appearance

Off-white solid

Melting Point

96-97°C

Boiling Point

329.1±15.0°C (Predicted)

Relative Density

1.137±0.06 (Predicted)

General Description

Pirfenidone is a small‑molecule anti‑fibrotic agent with a pyridone structure, chemically related to pyridine‑2‑one. Its structure is 5‑methyl‑1‑phenyl‑2‑(1H)‑pyridone, with a molecular weight of 185.2 Da. The molecule is a white to off‑white powder, slightly soluble in water but soluble in alcohol and other organic solvents.

Mechanism of Action

Pirfenidone reduces fibrosis by downregulating the production of transforming growth factor‑β (TGF‑β), a key cytokine in the fibrotic cascade, and by inhibiting fibroblast proliferation and collagen synthesis. It also has antioxidant activity, scavenging reactive oxygen species (ROS) and reducing the release of pro‑inflammatory cytokines. The drug modulates multiple pathways involved in the pathogenesis of fibrosis.

Application

Pirfenidone is indicated for the treatment of idiopathic pulmonary fibrosis (IPF), slowing the decline in lung function and reducing the risk of mortality. It is also used for the treatment of pulmonary fibrosis associated with other conditions, and it is being investigated for the management of renal fibrosis, systemic sclerosis, and other fibrotic disorders.

In a phase 1 trial, 30 patients with bronchiolitis obliterans syndrome (BOS) after HCT received pirfenidone for 56 weeks (with extension). It was well tolerated in 63% at the recommended dose. Significant improvements were seen in percent predicted FEV₁ (P=0.00267), liver function tests, physical functioning, shortness of breath, and cGVHD skin scores. qCT showed healthier upper lobe lungs in responders.

Fig. 1 Responders to pirfenidone have qCT metrics in the upper lobes that are consistent with healthier lungs. (Sharifi H, et al., 2025)

References

Sharifi H, et al. Pirfenidone for the treatment of bronchiolitis obliterans syndrome related to chronic graft-versus-host disease. Blood Adv. 2025;9(19):5024-5037.

This theoretical perspective proposes pirfenidone as a potential treatment for COVID‑19. Pirfenidone blocks TGF‑β maturation, enhances PPAR activity, and has antioxidant effects. It could suppress the inflammatory response and prevent lung injury by counteracting TGF‑β‑induced ENaC internalization, CFTR downregulation, PAI‑1 activation, and NF‑κB activation. The authors suggest combining pirfenidone with N‑acetylcysteine for maximum benefit.

Fig. 2 Pirfenidone activates peroxisome proliferator-activated receptors (alpha and gamma) (PPAR). (Hamidi SH, et al., 2021)

References

Hamidi SH, et al. Role of pirfenidone in TGF-β pathways and other inflammatory pathways in acute respiratory syndrome coronavirus 2 (SARS-Cov-2) infection: a theoretical perspective. Pharmacol Rep. 2021;73(3):712-727.

Does Pirfenidone require protection from light during long-term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation and discoloration. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Pirfenidone?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can soften the powder and accelerate degradation.

Is Pirfenidone hygroscopic, and how is this managed?

It is slightly hygroscopic. Under high humidity (>70% RH), it may absorb moisture and clump. Storage in tightly sealed containers with desiccant is recommended.

How is the impurity pirfenidone N-oxide (an oxidative degradation product) monitored?

This degradation product is quantified using a stability-indicating HPLC method, ensuring it remains within ICH qualification thresholds.