Bronchiolitis Obliterans Syndrome

Zambon is continually searching for solutions with the potential to make lives better for people affected by severe respiratory diseases such as BOS

Bronchiole with open airway and with obstructed airway


Bronchiolitis obliterans syndrome (BOS) is the most common form of chronic lung allograft dysfunction (CLAD) after lung transplantation (also referred to as chronic rejection). Chronic rejection can occur as the result of an immune reaction to the transplanted lung or lungs. In BOS, an uncontrolled immune reaction leads to chronic inflammation of the small airways (the bronchioles) of the lungs. This causes scarring and narrowing of the airways that continues to worsen over time, limiting an individual’s ability to breathe.

Understanding BOS

Historically known as “popcorn lung”, BOS commonly affects people following lung or stem cell transplantation, although it is also associated with autoimmune diseases and exposure to environmental contaminants.

BOS is a rapidly progressive inflammatory rare disease that irreversibly destroys the airways of the lungs and usually leads to respiratory failure and death within 2 to 4 years after diagnosis.1 Currently, there is no approved treatment indicated for BOS.2

An estimated 50% of lung transplant patients develop BOS within five years post-transplant.3 The average incidence of BOS in alloHSCT patients is 8.3%.4 There are an estimated 30,000 lung transplant and alloHSCT recipients worldwide with BOS. 5

1. Chambers DC, et al. J Heart Lung Transplant. 2018;37(10):1169–1183.
2. Verleden GM, et al. J Heart Lung Transplant. 2019; 38(5):493-503.
3. Weigt, et al. Semin Respir Crit Care Med. 2013;34(3):336–351.
4. Soubani, AO. Eur Respir J.  2007; 29: 1007-1019.
5. Data on File. Zambon. 2019.

Discover more about BOS

Rare Disease Week 2021

BOS - The Achilles Heel of Lung Transplantation

Zambon Team

During Rare Disease Week 2021, Zambon shared the findings of a comprehensive research project involving interviews with almost 40 BOS patients, caregivers and healthcare professionals. The findings provide a unique insight into the emotional impact of a BOS diagnosis, and the reality of living with BOS and the challenges and opportunities of BOS detection, diagnosis, and care.

BOSTON Program

The BOSTON clinical development program is evaluating investigational Liposomal Cyclosporine A for Inhalation (L-CsA-i) for the treatment of BOS. The formulation of L-CsA-i is administered via the optimized investigational eFlow® Technology nebulizer system (PARI Pharma GmbH). The rationale of inhaled therapy is to deliver sufficient concentrations of drug directly to the site of disease while minimizing systemic exposure.

We are currently conducting two global pivotal phase 3 studies to evaluate the safety and efficacy of L-CsA-i for the treatment of BOS in adults following single lung (BOSTON-1) or double lung (BOSTON-2) transplantation. The studies are enrolling patients in eight countries, including more than 20 US clinical sites.

BOSTON-3 is an open-label extension study for eligible patients who complete participation in either the BOSTON-1 or BOSTON-2 studies.

BOSTON-4 is currently underway at European clinical sites and will assess the safety and exploratory efficacy in adults with BOS following allogeneic hematopoietic stem cell transplant (alloHSCT).

BOSTON-5 is a planned safety study in pediatric patients with BOS.

L-CsA-i has received FDA Fast Track and Orphan Drug Designations for the treatment of BOS from US Food and Drug Administration and European Medicines Agency, reflecting the high unmet need of the disease. If approved, L-CsA-i would be the first treatment indicated for BOS. Conditioned upon receiving necessary regulatory approvals, we are preparing market access and product launch plans in the U.S., EU and other global markets.

Conditioned upon receiving necessary regulatory approvals, we are preparing market access and product launch plans in the U.S., EU and other global markets.

*For US Healthcare Professionals