Bronchiolitis Obliterans Syndrome Market

• DelveInsight estimates that in 2024, there were more than 34 thousand total diagnosed prevalent cases of BOS across the 7MM, which are expected to increase by 2034.
• In the US, total diagnosed prevalent cases of BOS exceeded 18 thousand in 2024 and are anticipated to grow by 2034.
• Despite improvements in transplant protocols and immunosuppressive regimens, BO0053 continues to lack disease-modifying therapies that can effectively prevent, halt, or reverse the fibrotic airway obstruction. This persistent gap underscores the urgent need for innovative, targeted interventions that go beyond symptom management to preserve graft function and extend long-term survival for transplant recipients.
• Currently, there are no approved drugs specifically for BOS, but several promising therapies are in development, including Alvelestat (MPH966) by Mereo BioPharma, ARINA-1 by Renovion, and LAM-001 by OrphAI Therapeutics, among others. These emerging treatments aim to offer more targeted and effective options for managing BOS and slowing disease progression.
• BOS treatment lacks truly curative or disease-reversing options, with current approaches mainly focused on broad immunosuppression and symptom management. Available therapies often fail to fully halt progression or restore lost lung function. Diagnostic challenges persist due to non-specific symptoms and limited early detection tools. There is a critical need for earlier diagnosis, targeted lung-specific therapies, and innovative strategies to slow or stop airway damage to improve outcomes for patients with BOS.
• Mereo BioPharma, Renovion, and OrphAI Therapeutics, among others, are advancing their assets through various clinical trial phases, driving innovation in the BOS market and creating significant opportunities to address unmet needs and improve patient outcomes.

DelveInsight’s “Bronchiolitis Obliterans Syndrome (BOS) – Market Insights, Epidemiology, and Market Forecast – 2034” report delivers an in-depth understanding of BOS, historical and forecasted epidemiology, as well as the BOS market trends in the United States, EU4 (Germany, France, Italy, and Spain), the United Kingdom, and Japan.

The BOS market report provides current treatment practices, emerging drugs, market share of individual therapies, and current and forecasted 7MM BOS market size from 2020 to 2034. The report also covers BOS treatment practices/algorithms and unmet medical needs to curate the best opportunities and assess the market’s potential.

Bronchiolitis Obliterans Syndrome (BOS) Understanding and Treatment Algorithm

Bronchiolitis Obliterans Syndrome (BOS) Overview

BOS is a chronic, progressive lung disease that affects people differently but almost always leads to irreversible airway damage if not managed early. Most commonly seen in lung or stem cell transplant recipients, BOS gradually scars and blocks the small airways, causing symptoms like persistent dry cough, worsening shortness of breath, wheezing, and frequent respiratory infections that can severely limit daily activities. While some may experience a slow decline, many face a steady loss of lung function that can lead to respiratory failure if untreated. Unlike infections, BOS is not contagious, but its impact on quality of life and survival is significant, as it remains a leading cause of late transplant failure. Current therapies aim to slow progression with intensified immunosuppression or anti-inflammatory treatments like azithromycin, but there is no cure, and lung retransplantation is often the last resort for severe cases. Early detection through regular lung function monitoring, timely diagnosis, and personalized care are essential to help patients preserve their lung health and quality of life for as long as possible.

Further details related to country-based variations are provided in the report…

Bronchiolitis Obliterans Syndrome (BOS) Diagnosis 

Pulmonary function testing is crucial for diagnosing bronchiolitis obliterans syndrome (BOS), typically showing irreversible airflow obstruction with reduced FEV1 and FEV1/FVC ratio, possible hyperinflation, and decreased DLCO. Imaging may reveal hyperinflation or a mosaic attenuation pattern due to air trapping. While bronchoscopy can help rule out other causes, lung biopsy is rarely needed if classic clinical and spirometric findings are present, especially post-transplant. When biopsy is required, surgical biopsy is preferred due to low sensitivity of transbronchial sampling. Ultimately, BOS diagnosis hinges on spirometry evidence of fixed obstructive lung disease in the appropriate clinical context.

Bronchiolitis Obliterans Syndrome (BOS) Treatment

Treatment of BOS after lung transplant focuses on intensifying immunosuppression, using agents like tacrolimus, cyclosporine, mycophenolate mofetil, and prednisone, as BOS reflects chronic rejection. Azithromycin and triple therapy with inhaled fluticasone, montelukast, and azithromycin can help slow lung function decline. Managing gastroesophageal reflux is also important. For severe, progressive BOS, lung retransplantation or extracorporeal photopheresis may be considered. In non-transplant BOS, removing the offending agent is key. Immunosuppression may help if BOS is linked to rheumatoid arthritis but is ineffective for toxic or post-infectious cases, where symptomatic care with bronchodilators, cough suppressants, and oxygen is the mainstay.

Bronchiolitis Obliterans Syndrome (BOS) Epidemiology

As the market is derived using a patient-based model, the BOS epidemiology chapter in the report provides historical as well as forecasted epidemiology segmented by total diagnosed prevalent cases of BOS, grade -specific diagnosed prevalent cases of BOS, total treated cases of BOS in the 7MM covering the United States, EU4 countries (Germany, France, Italy, and Spain), the United Kingdom, and Japan from 2020 to 2034. 

• In 2024, EU4 and the UK together accounted for more than 14 thousand diagnosed prevalent cases of BOS, a number expected to increase by 2034. Among these countries, Germany reported the highest number of diagnosed prevalent BOS cases in 2024.
• According to DelveInsight’s analysts, there were more than 1,000 Grade 0 or 0p, over 400 Grade 1 (mild), more than 500 Grade 2 (moderate), and over 400 Grade 3 (severe) BOS cases in Japan in 2024, and these numbers are expected to increase during the forecast period (2025–2034).
• According to the World Health Organization’s Global Observatory on Donation and Transplantation (GODT), nearly 3,000 lung transplants were performed in the US in 2024, all from deceased donors, underscoring the continued high demand for donor lungs and the vital importance of transplantation in treating advanced lung diseases. 

Bronchiolitis Obliterans Syndrome (BOS) Drug Chapters

Emerging Drugs

ARINA-1: Renovion

ARINA-1 is an innovative, at-home nebulized therapy in Phase III development, designed to support overall lung health by effectively clearing excess mucus, reducing airway inflammation, and limiting bacterial growth. By combining these actions, ARINA-1 aims to improve breathing, protect lung function, and offer patients a convenient and proactive way to manage chronic lung conditions.

• In March 2023, Renovion reported that the FDA granted Fast Track designation (FTD) to ARINA-1 for preventing BOS progression in adults with bilateral lung transplants. This designation streamlines development and allows rolling submissions for faster review, aiming to speed up access to promising treatments for serious unmet medical needs.
• In January 2017, Renovion, reported that the FDA Office of Orphan Products granted Orphan Drug Designation (ODD) in the US to its nebulized therapy ARINA-1 for the treatment of lung dysfunction following lung transplant.

Alvelestat (MPH966): Mereo Biopharma

Alvelestat developed by Mereo BioPharma, is an oral neutrophil elastase inhibitor currently being evaluated in Phase I/II clinical trials for patients with BOS following stem-cell transplantation. This investigational therapy represents a novel approach aimed at managing inflammation and slowing disease progression in individuals affected by BOS, where effective treatment options remain limited.

• In December 2021, Mereo BioPharma shared encouraging results from the first seven patients enrolled in its investigator-sponsored study. Interim Phase Ib data showed that six out of seven patients experienced a steady decline in plasma desmosine levels over eight weeks, while all patients demonstrated improved or stable lung function (FEV1) and reduced stimulated neutrophil elastase activity. These findings suggest that Alvelestat may meaningfully slow disease progression and preserve lung function in BOS patients, addressing a key gap in current treatment options. 

LAM-001: OrphAI Therapeutics

LAM-001 is OrphAI Therapeutics’ proprietary dry powder inhaled formulation of sirolimus. It is designed to deliver therapeutic doses directly to the lungs, minimizing systemic exposure and toxicity for a safer, more targeted treatment. Early animal and human data support this improved safety profile. LAM-001 is currently in Phase II clinical trials for rare lung diseases, including PH and BOS.

• In September 2023, AI Therapeutics reported its rebranding to OrphAI Therapeutics.
• On August, 2023, OrphAI Therapeutics, reported the initiation of a Phase II study of its novel inhaled sirolimus, LAM-001, for the treatment of BOS, marking an important step toward addressing this challenging rare lung disease. 

Drug Class Insights

The treatment landscape for BOS has progressed to focus on slowing progression, preserving lung function, and managing symptoms. Care centers on optimizing immunosuppression and supportive measures to control inflammation and complications. For advanced cases, retransplantation may be an option, highlighting the critical need for more effective therapies to improve long-term outcomes.

The BOS treatment market is gradually expanding with a pipeline of promising therapies aiming to address the unmet need for targeted, lung-specific treatments that go beyond traditional immunosuppression. Emerging therapies include ARINA-1, an innovative nebulized therapy designed to restore lung health by clearing mucus and reducing airway inflammation; Alvelestat (MPH966), an oral neutrophil elastase inhibitor targeting neutrophil-driven damage; and LAM-001, an inhaled formulation of sirolimus engineered to deliver anti-inflammatory effects directly to the lungs while minimizing systemic toxicity. Several of these candidates have secured Fast Track or Orphan Drug Designations from the US FDA, reflecting their potential to transform BOS care by tackling the underlying mechanisms of chronic rejection and airway injury, and offering new hope for patients facing this progressive condition.

Continued in report…

Market Outlook

BOS is the most common form of chronic lung allograft dysfunction, characterized by progressive and irreversible airflow obstruction due to fibrotic narrowing of the small airways. While its exact mechanism is not fully understood, BOS is believed to result from an alloimmune response in which the recipient’s immune system attacks the transplanted lung, causing inflammation and scarring of the bronchioles. This immune-mediated injury is driven by persistent rejection processes and other factors like infections or gastroesophageal reflux, which further damage the airway epithelium. Over time, this leads to obliteration of the bronchiolar lumen, resulting in declining lung function and respiratory failure if untreated. Although there is no cure for BOS, management focuses on slowing disease progression by optimizing immunosuppression, using anti-inflammatory agents like azithromycin, and treating contributing factors, but these measures do not reverse established fibrosis. In advanced cases, lung retransplantation may be the only option to restore lung function and prolong survival.

The BOS therapeutics market is further expected to grow, driven by factors such as the rising number of transplant procedures, improved diagnostic monitoring, and the development of novel targeted therapies during the forecast period (2025–2034).

When standard therapies prove insufficient, especially in progressive or treatment-resistant BOS, carefully selected off-label and adjunctive options may offer additional benefit. In BOS, macrolide antibiotics like azithromycin are often used off-label for their anti-inflammatory effects to help slow the decline in lung function. Other approaches, such as extracorporeal photopheresis or leukotriene inhibitors, have shown potential in certain patients but remain outside formal treatment guidelines. In severe, unresponsive cases, lung retransplantation becomes the last resort to restore lung function and improve survival. These strategies highlight the critical need for individualized, specialist-guided management and the development of novel, more effective therapies to address the limitations of current treatment approaches.

Bronchiolitis Obliterans Syndrome (BOS) Drugs Uptake

This section focuses on the uptake rate of potential drugs expected to be launched in the market during study period 2020–2034. 

Bronchiolitis Obliterans Syndrome (BOS) Pipeline Development Activities

The report provides insights into different therapeutic candidates in Phase III, Phase II, and Phase I. It also analyzes key players involved in developing targeted therapeutics. 

Pipeline development activities

The report covers information on collaborations, acquisitions and mergers, licensing, and patent details for emerging therapies for BOS. 

KOL Views

To keep up with current market trends, we take KOLs and SMEs’ opinions working in the domain through primary research to fill the data gaps and validate our secondary research. Industry Experts contacted for insights on BOS evolving treatment landscape, patient reliance on conventional therapies, patient therapy switching acceptability, and drug uptake, along with challenges related to accessibility, including Medical/scientific writers, Medical Professionals, Professors, Directors, and others.

DelveInsight’s analysts connected with 50+ KOLs to gather insights; however, interviews were conducted with 15+ KOLs in the 7MM. Centers like the Baylor College of Medicine and Methodist Hospital, US; University of Minnesota, US; University of Freiburg, Germany; Hôpital St Louis, France; University of Siena, Italy; University of Valencia, Spain; University Forvie Site, UK; Jichi Medical University, Japan; and Chiba University, Japan; among others, were contacted. Their opinion helps understand and validate current and emerging therapy treatment patterns or BOS market trends. This will support the clients in potential upcoming novel treatments by identifying the overall scenario of the market and the unmet needs.

Physician’s View

As per KOLs from the US, the development of Alvelestat (MPH966) marks a significant step forward in BOS management. By precisely targeting neutrophil-driven airway damage, Alvelestat offers a more focused approach than standard immunosuppression, with the potential to better preserve lung function and slow disease progression. This advancement reflects growing momentum toward more effective, patient-centered BOS therapies.

As per KOLs in Spain, BOS is an increasing public health challenge, with cases on the rise, especially among lung transplant recipients and other high-risk groups. Its progressive loss of lung function, significant impact on quality of life, and lack of curative treatments highlight the urgent need for earlier diagnosis and more effective therapeutic options.

As per KOLs from Japan, BOS poses a rising clinical and economic burden. As cases increase, so do the costs associated with intensive management, long-term immunosuppression, and potential retransplantation. Given its significant impact on lung function and quality of life, there is an urgent need for more effective and economically sustainable approaches to diagnose, treat, and manage BOS within the healthcare system.

Qualitative Analysis

We perform Qualitative and market Intelligence analysis using various approaches, such as SWOT and Attribute Analysis. In the SWOT analysis, strengths, weaknesses, opportunities, and threats in terms of disease diagnosis, patient awareness, patient burden, competitive landscape, cost-effectiveness, and geographical accessibility of therapies are provided. These pointers are based on the Analyst’s discretion and assessment of the patient burden, cost analysis, and existing and evolving treatment landscape.

Attribute Analysis analyzes multiple emerging therapies based on relevant attributes such as safety, efficacy, frequency of administration, route of administration, and order of entry. Scoring is given based on these parameters to analyze the effectiveness of therapy.

Further, the therapies’ safety is evaluated wherein the adverse events are majorly observed, and it sets a clear understanding of the side effects posed by the drug in the trials, which directly affects the safety of the molecule in the upcoming trials. It sets a clear understanding of the side effects posed by the drug in the trials. In addition, the scoring is also based on the route of administration, order of entry and designation, probability of success, and the addressable patient pool for each therapy. According to these parameters, the final weightage score and the ranking of the emerging therapies are decided. 

Market Access and Reimbursement

US

Centre for Medicare and Medicaid Services (CMS)

The United States drug pricing regime is complex given its multi-payer model. It is currently undergoing significant changes, with recent federal legislation, such as the Prescription Drug Pricing Reform provisions of the Inflation Reduction Act, significantly altering the pricing regime under certain federal programs.

The US health care system includes both private and public health insurance coverage.  Whether a drug product is covered, and at what price, is determined by each payer’s coverage, coding, and payment criteria for health insurance plans. The largest government-funded programs are Medicare and Medicaid. Private plans, which cover far more Americans than public plans, have more flexibility to make coverage and reimbursement determinations. 

Further details will be provided in the report.

The report provides detailed insights on the country-wise accessibility and reimbursement scenarios, cost-effectiveness scenarios, programs making accessibility easier and out-of-pocket costs more affordable, insights on patients insured under federal or state government prescription drug programs, etc.

Scope of the Report

• The report covers a segment of key events, an executive summary, and a descriptive overview of BOS, explaining its causes, signs and symptoms, pathogenesis, and currently available therapies.
• Comprehensive insight into the epidemiology segments and forecasts, the future growth potential of diagnosis rate, disease progression, and treatment guidelines have been provided.
• Additionally, an all-inclusive account of the current and emerging therapies and the elaborative profiles of late-stage and prominent therapies will affect the current treatment landscape.
• A detailed review of the BOS market, historical and forecasted market size, market share by therapies, detailed assumptions, and rationale behind our approach is included in the report, covering the 7MM drug outreach.
• The report provides an edge while developing business strategies by understanding trends through SWOT analysis and expert insights/KOL views, patient journey, and treatment preferences that help shape and drive the 7MM BOS market.

Bronchiolitis Obliterans Syndrome (BOS) Report Insights

• Patient Population
• Therapeutic Approaches
• BOS Pipeline Analysis
• BOS Market Size and Trends
• Existing and Future Market Opportunity 

Bronchiolitis Obliterans Syndrome (BOS) Report Key Strengths

• 10 years Forecast
• The 7MM Coverage 
• BOS Epidemiology Segmentation
• Key Cross Competition 
• Attribute analysis
• Drugs Uptake and Key Market Forecast Assumptions

Bronchiolitis Obliterans Syndrome (BOS) Report Assessment

• Current Treatment Practices
• Unmet Needs
• Pipeline Product Profiles
• Market Attractiveness
• Qualitative Analysis (SWOT and Attribute Analysis)

Key Questions

Market Insights

• What was the total market size of BOS, the market size of BOS by therapies, and market share (%) distribution in 2020, and what would it look like by 2034? What are the contributing factors for this growth?
• How will arina-1 affect the treatment paradigm of BOS?
• Which drug is going to be the largest contributor by 2034?
• What are the pricing variations among different geographies for approved and marketed therapies?
• How would future opportunities affect the market dynamics and subsequent analysis of the associated trends?

Epidemiology Insights

• What are the disease risks, burdens, and unmet needs of BOS? What will be the growth opportunities across the 7MM with respect to the patient population pertaining to BOS?
• What is the historical and forecasted BOS patient pool in the United States, EU4 (Germany, France, Italy, and Spain) and the United Kingdom, and Japan?
• Out of the countries mentioned above, which country would have the highest diagnosed prevalent BOS population during the forecast period (2025–2034)?
• What factors are contributing to the growth of BOS cases?

Current Treatment Scenario, Marketed Drugs, and Emerging Therapies

• What are the current options for the treatment of BOS? What are the current clinical and treatment guidelines for treating BOS?
• How many companies are developing therapies for the treatment of BOS?
• How many emerging therapies are in the mid-stage and late stage of development for treating BOS?
• What are the recent novel therapies, targets, mechanisms of action, and technologies developed to overcome the limitations of existing therapies? 
• Patient acceptability in terms of preferred treatment options as per real-world scenarios?
• What is the 7MM historical and forecasted market of BOS?

Reasons to Buy

• The report will help develop business strategies by understanding the latest trends and changing treatment dynamics driving the BOS market.
• Insights on patient burden/disease prevalence, evolution in diagnosis, and factors contributing to the change in the epidemiology of the disease during the forecast years.
• Understand the existing market opportunities in varying geographies and the growth potential over the coming years.
• The distribution of historical and current patient share is based on real-world prescription data in the United States, EU4 (Germany, France, Italy, and Spain) and the United Kingdom, and Japan.
• Identifying upcoming solid players in the market will help devise strategies to help get ahead of competitors.
• Detailed analysis, ranking of class-wise potential current, and emerging therapies under the attribute analysis section to provide visibility around leading classes.
• Highlights of Access and Reimbursement policies for BOS, barriers to accessibility of approved therapy, and patient assistance programs.
• To understand Key Opinion Leaders’ perspectives around the accessibility, acceptability, and compliance-related challenges of existing treatment to overcome barriers in the future.
• Detailed insights on the unmet needs of the existing market so that the upcoming players can strengthen their development and launch strategy