IPF Treatment Landscape 2025: Approved Therapies, Next-Gen Disease-Modifying Drugs & Preclinical Evidence

1. Introduction: A Paradigm Shift in IPF Drug Development

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive fibrotic interstitial lung disease with an extremely poor prognosis following diagnosis. Historically, the therapeutic strategy for IPF has been focused on slowing the rate of lung function decline — termed "progression suppression." Since the establishment of pirfenidone and nintedanib as Standard of Care (SoC), there had been an "innovation gap" of approximately 10 years with no new drug approvals.

However, from 2024 to 2025, this stagnation is being dramatically disrupted. This report comprehensively surveys and analyzes the clinical trial results and mechanisms of action (including preclinical data) of the latest developments — from nerandomilast, the first new drug approved by the US FDA in over a decade (October 2025), to inhaled treprostinil (which met its primary endpoint in Phase 3), and next-generation compounds showing groundbreaking Phase 2 data suggesting lung function "improvement" and fibrosis "regression."

This article examines the current standard of care, analyzes Phase 3 successes and failures, and discusses promising Phase 2 candidates with disease-modifying potential. We emphasize a translational perspective — connecting each drug's pathophysiological target with its clinical outcomes.

2. Current Approved Therapies and Standard of Care

Two drugs are currently approved and recommended in international guidelines for IPF treatment: pirfenidone and nintedanib. While proven to slow disease progression, neither halts it, and tolerability concerns remain.

2.1 Pirfenidone

Brand Name: Pirespa (Japan), Esbriet (US/EU)
Developer: Shionogi (Japan), Roche/Genentech (Global)

Pirfenidone is the world's first approved antifibrotic agent for IPF, possessing a pleiotropic mechanism of action.

2.1.1 Clinical Efficacy and Safety

Pirfenidone's approval was primarily based on the multinational Phase 3 ASCEND and CAPACITY trials. In ASCEND, the pirfenidone group demonstrated significant suppression of FVC decline at 52 weeks compared to placebo, reducing the risk of disease progression by approximately 48%. Pooled analyses also suggested reductions in all-cause and IPF-related mortality, and respiratory-related hospitalization risk.

Japan-Specific Dosing Notably, the approved dose in Japan (1,200–1,800 mg/day) differs from the Western standard (2,403 mg/day). Japanese Phase 3 trials showed significant FVC preservation at both dose levels, and Korean real-world data confirmed efficacy and tolerability at ≤1,800 mg/day, suggesting that Asian patients may achieve therapeutic effects at lower doses.

2.1.2 Mechanism of Action (Preclinical Evidence)

TGF-β Pathway Suppression: Inhibits TGF-β production and activation, blocking fibroblast-to-myofibroblast differentiation and collagen synthesis.
Anti-inflammatory Cytokine Modulation: Reduces IL-1β, IL-6, TNF-α, IFN-γ, and MCP-1 in bleomycin-induced lung fibrosis models.
Direct Collagen Fibril Inhibition: Recent research reveals pirfenidone directly inhibits collagen type I fibril formation, with electron microscopy showing shortened and thinned collagen fiber bundles.

2.1.3 Safety Considerations

Key adverse effects include photosensitivity, rash, nausea, and GI symptoms. Approximately 15% of patients in ASCEND/CAPACITY discontinued treatment due to side effects.

2.2 Nintedanib

Brand Name: Ofev
Developer: Boehringer Ingelheim

Nintedanib is a tyrosine kinase inhibitor (TKI) targeting multiple growth factor receptors involved in fibrosis.

2.2.1 Clinical Efficacy and Indication Expansion

In the Phase 3 INPULSIS trials, nintedanib (150 mg BID) significantly reduced the annual rate of FVC decline in IPF patients. Pooled analysis showed FVC decline of -113.6 mL/year vs -223.5 mL/year for placebo — approximately 50% suppression.

Expansion to PF-ILD Nintedanib is uniquely approved for progressive fibrosing interstitial lung diseases (PF-ILD) and systemic sclerosis-associated ILD (SSc-ILD), clinically proving that antifibrotic therapy can be effective across different etiologies sharing the common pathology of progressive fibrosis.

2.2.2 Mechanism of Action (Preclinical Evidence)

Nintedanib potently inhibits three receptor tyrosine kinases:

PDGFR-α/β
FGFR-1/2/3
VEGFR-1/2/3

In vitro: Suppresses TGF-β-stimulated collagen I/III/V expression, fibronectin secretion, and collagen chaperone (FKBP10, HSP47) expression in IPF patient-derived fibroblasts.
In vivo: Significantly reduces α-SMA expression and tissue fibrosis in bleomycin-induced and joint contracture models.

2.2.3 Safety and Drug Interactions

Diarrhea occurs in >60% of patients. Hepatic function monitoring is required. Pharmacokinetic studies confirm that co-administration with pirfenidone does not significantly alter either drug's plasma levels — an important foundation for future combination therapy.

3. Phase 3 Breakthroughs: The First New Approvals in a Decade

3.1 Nerandomilast (Jascayd): Selective PDE4B Inhibition

Developer: Boehringer Ingelheim
Approval: US FDA approved (October 2025); Japan/EU under review

Nerandomilast (BI 1015550) is an oral, selective phosphodiesterase 4B (PDE4B) inhibitor. By selectively targeting the PDE4B subtype (which is highly expressed in inflammatory cells and fibroblasts), it avoids the severe GI side effects associated with non-selective PDE4 inhibitors.

3.1.1 Phase 3 FIBRONEER-IPF Results

The pivotal trial (NCT05321069) enrolled 1,177 IPF patients, including those on background antifibrotic therapy.

Primary Endpoint (FVC Change): Both dose groups showed significant FVC preservation at 52 weeks:
- 18 mg BID: -106 mL (vs placebo -170 mL; difference ~+64 mL)
- 9 mg BID: -122 mL (difference ~+48 mL)
US Subgroup: In US patients (n=196), the treatment effect was even more pronounced (~100–130 mL difference).
Secondary Endpoints: Trends toward reduced risk of acute exacerbation, respiratory hospitalization, and death (HR 0.74–0.86).

3.1.2 Expansion to PPF

In the parallel FIBRONEER-ILD trial (NCT05321082), nerandomilast also significantly reduced FVC decline in PPF patients (18 mg: -86 mL; 9 mg: -69 mL vs placebo: -152 mL).

3.1.3 Preclinical Mechanism

PDE4B selectivity: Elevates intracellular cAMP, suppressing pro-inflammatory cytokines (TNF-α, IL-6) and inhibiting fibroblast proliferation and myofibroblast differentiation.
Bleomycin/silica models: Suppresses macrophage and neutrophil infiltration, dramatically reduces TGF-β1 and IL-6 expression, and inhibits NLRP3 inflammasome activation.
Human cells: Induces myofibroblast dedifferentiation and enhances endothelial barrier function in IPF patient-derived fibroblasts.

3.2 Inhaled Treprostinil (Tyvaso): Dual Targeting of Vasculature and Fibrosis

Developer: United Therapeutics
Status: TETON-2 Phase 3 success; US approval filing in preparation

3.2.1 Phase 3 TETON-2 Results

In 597 IPF patients (NCT05255991), inhaled treprostinil (QID) demonstrated a +95.6 mL treatment difference versus placebo in absolute FVC change at 52 weeks (p<0.0001). The benefit was more pronounced in patients on background antifibrotic therapy, suggesting additive/synergistic effects.

3.2.2 Preclinical Mechanism

Direct antifibrotic action: Elevates cAMP via IP, EP2, DP1 receptors and PPARs, potently suppressing TGF-β and PDGF-induced fibroblast proliferation and collagen synthesis.
Mitochondrial function restoration: Normalizes fusion/fission abnormalities in IPF-derived fibroblasts.

4. Promising Phase 2 Candidates: Toward Disease "Reversal"

Phase 2 data now suggest not just FVC stabilization, but actual improvement — raising the prospect of true disease modification.

4.1 BMS-986278 (Admilparant): LPA1 Antagonist

Developer: Bristol Myers Squibb
Phase 2 Data: 60 mg BID reduced FVC decline by 62% vs placebo (IPF cohort: -1.2% vs -2.7% at 26 weeks).
Phase 3: ALOFT-IPF and ALOFT-PPF trials ongoing (completion ~2026–2027).

4.2 ENV-101 (Taladegib): Fibrosis Regression and Lung Volume Recovery

Developer: Endeavor BioMedicines
Target: Hedgehog (Hh) pathway
Phase 2a Data: ENV-101 achieved FVC improvement of +1.9% at 12 weeks (vs -1.3% for placebo). AI-analyzed HRCT showed significant increases in total lung capacity (+200 mL vs -56 mL) and reduced pulmonary vascular volume — suggesting structural reversal of fibrosis.
Phase 2b: WHISTLE-PF trial ongoing.

4.3 Buloxibutid (C21): AT2 Receptor-Mediated Tissue Repair

Developer: Vicore Pharma
Phase 2a (AIR Trial): FVC increased by +216 mL from baseline over 36 weeks — extraordinary given the expected ~180 mL decline in untreated patients.
Mechanism: Promotes AEC2 protection and regeneration. Biomarker analysis showed elevated MMP-13 (collagen-degrading enzyme), indicating active fibrosis resolution.

4.4 ISM001-055 (Rentosertib): AI-Discovered Target

Developer: Insilico Medicine
Target: TNIK (Traf2- and NCK-Interacting Kinase)
Phase 2a Data: 60 mg QD achieved FVC improvement of +98.4 mL at 12 weeks (vs -62.3 mL for placebo).
Significance: One of the world's first cases where an AI-discovered target and AI-designed molecule achieved proof-of-concept in human clinical trials.

4.5 Other Notable Candidates

Axatilimab (Syndax/Incyte): Anti-CSF-1R antibody targeting pro-fibrotic macrophages. MAXPIRe Phase 2 trial ongoing for IPF.
HZN-825 (Amgen/Horizon): Another LPA1 antagonist in Phase 2b.

5. Lessons from Failures: Late-Stage Discontinuations

5.1 Pamrevlumab (ZEPHYRUS-1)

Target: CTGF
Failed to show significance at 48 weeks (p=0.29). Likely underpowered Phase 2 and inability to detect add-on effects over SoC.

5.2 Bexotegrast (BEACON-IPF)

Target: αvβ6/αvβ1 integrin
Interim analysis showed increased risk of respiratory hospitalization/death vs placebo despite initial FVC trends. Trial terminated early — highlighting that integrins also play critical roles in immune defense and homeostasis.

5.3 TTI-101 (REVERT)

Target: STAT3
Failed to demonstrate efficacy with high dropout rates (56–62%) due to GI side effects.

6. Conclusion and Future Outlook

2025 is a landmark year for IPF drug development:

New Standard of Care: Nerandomilast and inhaled treprostinil enable combination therapy beyond existing antifibrotics, expected to further reduce FVC decline rates.
Disease Reversal on the Horizon: Phase 2 data from ENV-101, buloxibutid, and ISM001-055 suggest that IPF could transition from "a disease we can only slow" to "a disease we can halt or even reverse." FVC increases and lung volume recovery indicate that remodeling of fibrotic tissue may be achievable.
Remaining Challenges: Long-term safety, survival benefits, and the lessons from bexotegrast's failure regarding unexpected consequences of potent pathway inhibition.

The future of IPF treatment will likely evolve into precision medicine — selecting optimal molecular-targeted drug combinations based on individual patient profiles (inflammatory vs fibrotic dominance, genetic backgrounds).

Appendix: IPF Drug Comparison Tables

Table 1: Currently Approved IPF Therapies (as of December 2025)

Drug (Generic)	Brand	Mechanism	Approval (JP/US/EU)	Key Clinical Reference
Pirfenidone	Pirespa / Esbriet	Pleiotropic antifibrotic (TGF-β, collagen)	✓/✓/✓	ASCEND (NEJM 2014; PMID: 24836312)
Nintedanib	Ofev	TKI (PDGFR/FGFR/VEGFR)	✓/✓/✓	INPULSIS (NEJM 2014; PMID: 24836313)
Nerandomilast	Jascayd	Selective PDE4B inhibitor	Under review/✓ (Oct 2025)/Under review	FIBRONEER-IPF (NCT05321069)

Table 2: Promising Phase 3/2 Clinical Candidates

Stage	Drug (Code)	Target/Mechanism	Key Result
Approved (US)	Nerandomilast (BI 1015550)	PDE4B inhibitor	FVC: -106 mL vs -170 mL (placebo)
Ph3	Treprostinil (inhaled)	Prostacyclin/cAMP	FVC: +95.6 mL vs placebo (p<0.0001)
Ph3	BMS-986278 (Admilparant)	LPA1 antagonist	Ph2: 62% reduction in FVC decline
Ph2b	ENV-101 (Taladegib)	Hedgehog inhibitor	FVC: +1.9% improvement; TLC +200 mL
Ph2b	Buloxibutid (C21)	AT2R agonist	FVC: +216 mL in 36 weeks
Ph2a	ISM001-055 (Rentosertib)	TNIK inhibitor (AI-designed)	FVC: +98.4 mL in 12 weeks

Table 3: Key Preclinical References

Drug	Preclinical Model	Key Findings	PMID
Pirfenidone	Bleomycin mouse	TGF-β suppression, cytokine reduction	Multiple
Nintedanib	Bleomycin mouse/rat	PDGFR/FGFR/VEGFR inhibition, α-SMA reduction	Multiple
Nerandomilast	Bleomycin mouse (SSc-ILD)	TGF-β1/Smad pathway suppression	39438343
Treprostinil	Bleomycin mouse	Lung injury, vascular remodeling attenuation	31819797
BMS-986278	Bleomycin mouse	Fibrosis suppression, LPA signal blockade	34726410
ENV-101	Phase 2a clinical	Hedgehog inhibition, FVC improvement, TLC increase	41043447

References

Clinical Trial Registrations (ClinicalTrials.gov)

FIBRONEER-IPF: NCT05321069
FIBRONEER-ILD (PPF): NCT05321082
TETON-2 (Treprostinil): NCT05255991
TETON-1 (Treprostinil, US/Canada): NCT04708782
ALOFT-IPF (BMS-986278): NCT06003426
ENV-101 Phase 2a: NCT04968574
WHISTLE-PF (ENV-101 Phase 2b): NCT06422884
ASPIRE (Buloxibutid): NCT06588686
Rentosertib Phase 2a (China): NCT05938920

Key Publications (PubMed)

King TE Jr, et al. A Phase 3 Trial of Pirfenidone in Patients with Idiopathic Pulmonary Fibrosis. N Engl J Med. 2014;370(22):2083-92. PMID: 24836312
Richeldi L, et al. Efficacy and Safety of Nintedanib in Idiopathic Pulmonary Fibrosis. N Engl J Med. 2014;370(22):2071-82. PMID: 24836313
Nerandomilast SSc-ILD preclinical study. Clin Rheumatol. 2024. PMID: 39438343
Nerandomilast fibrotic rats study. Br J Pharmacol. 2024. PMID: 39183442
Treprostinil bleomycin mouse study. Pulm Circ. 2019;9(4). PMID: 31819797
BMS-986278 discovery and preclinical study. J Med Chem. 2021;64(21):15883-15911. PMID: 34726410
Taladegib Phase 2a for IPF. Lancet Respir Med. 2025;13(11):1001-1010. PMID: 41043447