Idiopathic Pulmonary Fibrosis: An Overview of Current Clinical Trials

Background

According to the Pulmonary Fibrosis Foundation, over 200 types of Interstitial Lung Diseases (ILDs) have been identified. ILDs are characterized by scarring or inflammation, or both, which damages the lungs’ ability to absorb oxygen. PF, or scarring of the lung, is often seen in ILDs. When the cause of the fibrosis is unknown it is termed “idiopathic.” IPF is the most frequently seen type of idiopathic ILD.¹

The ATS/ERS/JRS/ALAT Clinical Practice Guideline for IPF defines the disease as “a chronic, fibrosing interstitial pneumonia of unknown cause that is associated with radiological and histologic features of usual interstitial pneumonia (UIP). It occurs primarily in older adults, is characterized by progressive worsening of dyspnea and lung function and has a poor prognosis.”² Causes of IPF include smoking, genetics, and environmental or occupational exposures.

The Pulmonary Fibrosis Foundation further states that over 250,000 Americans are living with PF and ILD and IPF is one of the most common forms of PF. The prevalence of PF and ILD is rising with the number of new cases diagnosed annually exceeding 50,000.³ It was reported in 2023 that adjusted prevalence estimates around the world for IPF range from 0.33 to 2.51 per 10,000 persons in Europe and 2.40–2.98 per 10,000 persons in North America. The highest prevalence globally was in South Korea with 4.51 per 10,000 persons.⁴ The authors even suggested that although IPF is still considered a rare disorder, it may lose this distinction soon.⁵

There is currently no cure for IPF. The antifibrotic drugs pirfenidone and nintedanib gained FDA approval over 10 years ago as treatments for IPF. However, while they have been proven to lower the rate of progression and improve patient survival, there is still an urgent unmet need to find treatments that can stop disease progression.⁶

Current Clinical Trials of New Treatments

The Pulmonary Fibrosis Foundation’s PF Drug Development Pipeline shows three drugs that are currently available to patients with IPF: pirfenidone, nintedanib, and prednisone. While no additional treatments for IPF have yet reached patients, there are many clinical trials currently underway in Phases 1-3.⁷ A search of ClinicalTrials.gov using the search term Idiopathic Pulmonary Fibrosis and filtering for study start date (March 2023 to March 2024) and “recruiting and not yet recruiting status” returned over 35 studies. The following sections provide an overview of a selection of these clinical trials focusing on Phase 2 and 3 trials that have reported some results.

Phase II Trials

TTI-101 (NCT05671835)

Tvardi Therapeutics is sponsoring a Phase 2, multicenter, randomized, double-blind, placebo-controlled study to evaluate TTI-101, a novel STAT3 inhibitor, in participants with IPF. In 2022, Tvardi announced that the FDA had granted Orphan Drug Designation for TTI-101 for the treatment of IPF. At that time, pre-clinical studies had demonstrated STAT3 inhibition with TTI-101 reversed fibrosis and restored lung function in models of IPF.⁸ In May of 2023 the company launched the Phase II study, REVERTIPF and in August they announced the first patients were dosed.⁹

BBT-877 (NCT05483907)

In April 2023, Bridge Biotherapeutics announced the first IPF patient was dosed in a Phase 2 study of BBT-877 and in October 2023 they announced a positive recommendation from an Independent Data Monitoring Committee to continue the study.¹⁰ BBT-887 is an experimental Autotaxin inhibitor that limited lysophosphatidic acid (LPA) by up to 90% in a first-in-human study. LPA induces physiological activities that lead to the development of various fibrotic diseases including IPF.¹¹

Oral Ifetroban (NCT05571059)

Cumberland Pharmaceuticals announced the launch of a Phase 2 clinical trial of oral ifetroban in patients with IPF in May 2024.¹² Ifetroban is a thromboxane-prostanoid receptor (TBXA2R) antagonist. TBXA2R signaling has been studied in preclinical lung fibrosis models and was found to link oxidative stress to fibroblast activation during lung fibrosis. In one study, in vivo administration of ifetroban protected mice from lung fibrosis, reduced profibrotic signaling in the lungs in three preclinical models, and increased fibrotic resolution after bleomycin treatment.¹³

Axatilimab (NCT06132256)

Axatilimab, a novel monoclonal antibody that targets Colony Stimulating Factor-1 Receptor (CSF-1R), is being developed by Syndax and Incyte as a potential treatment for Graft-Versus-Host-Disease (GVHD) and IPF. A Phase 2 clinical trial in IPF patients is listed on ClinicalTrials.gov with a start date of December 12, 2023. CSF-1R is believed to lower the number of disease-mediating macrophages which can play a key role in fibrotic disease processes. Incyte and Syndax reported positive results in a Phase 2 trial in GVHD in an abstract at the American Society of Hematology Annual Meeting 2023.¹⁴ The FDA granted Orphan Drug Status for Axatilimab in both GVHD and IPF. In February 2024, Syndax reported that enrollment was ongoing in the Phase 2 trial for IPF.¹⁵

Phase 2b/3 Trials

Bexotegrast (NCT06097260)

Bexotegrast, under development by Pliant Therapeutics, is an αvβ6 and αvβ1 integrin inhibitor. While expressed at low levels in normal tissue, αvβ6 and αvβ1 are upregulated in the pulmonary tissues of IPF patients. It is believed the integrins activate TGF-ß, which leads to increased collagen production and thus to fibrosis. Pliant has launched BEACON-IPF, a Phase 2b clinical trial to evaluate Bexotegrast in participants with IPF.¹⁶ Data from INTEGRIS-IPF, a global Phase 2a study of Bexotegrast, was reported as a late-breaking abstract at the 2023 ERS International Congress. Bexotegrast-treated participants demonstrated reduced FVC decline at Week 12, with 50% of Bexotegrast participants still showing improvement at Week 24. 89% of Bexotegrast participants with improvement in FVC at Week 12 sustained this at Week 24. A favorable safety and tolerability profile was also found.¹⁷ In March 2024, Pliant announced an accelerated development plan for Bexotegrast whereby BEACON-IPF will be implemented as a Phase 2b/3 adaptive design with the hope of shortening the timeline to Phase 3 data.¹⁸ Bexotegrast has been granted Fast Track and Orphan Drug designations by the FDA.

BMS-986278 (NCT06003426)

Bristol Myers Squib (BMS) is currently enrolling participants in ALOFT, a global Phase 3 clinical trial of BMS-986278, a lysophosphatidic acid receptor 1 (LPA1) antagonist for treatment of patients with IPF and PFF. Higher LPA levels and activation of LPA1 are involved in pulmonary fibrosis pathogenesis, and preclinical studies demonstrated that antagonizing LPA1 may be helpful in treating lung injury and fibrosis. BMS presented positive Phase 2 data of a 69% relative reduction in the rate of decline in percent-predicted forced vital capacity for BMS-986278 at the September 2023 European Respiratory Society International Congress. BMS-986278 has been granted Breakthrough Therapy, Fast Track, and Orphan Drug designations by the FDA.¹⁹

Summary

The prevalence of PF and ILD are increasing globally and IPF is the most common form of PF. While two FDA-approved treatments for IPF do demonstrate modest slowing of disease progression, there is still an unmet medical need for additional treatments that could stop progression entirely or even provide a cure. The continued development of new treatments offers hope to IPF patients worldwide.