Brensocatib is making waves in respiratory medicine. Following the full publication of its Phase 3 ASPEN trial in The New England Journal of Medicine in May 2025 and FDA approval in April 2025, this new oral treatment is being hailed as a breakthrough for people living with non-cystic fibrosis bronchiectasis (NCFBE).
In the UK, healthcare professionals and patients now wait with growing anticipation as the drug moves through the regulatory process. In this article, we explore what brensocatib is, how it works, what the clinical trials show, and when it might become available in the UK.
What Is Brensocatib?
Brensocatib is a first-in-class oral medicine developed by Insmed Incorporated. It is designed to treat adults with non-cystic fibrosis bronchiectasis, a chronic lung disease characterised by permanent airway damage, mucus build-up, and frequent chest infections.
Brensocatib targets one of the causes of inflammation in bronchiectasis, rather than just treating the symptoms. It works by inhibiting dipeptidyl peptidase I (DPP1), an enzyme responsible for activating neutrophil serine proteases, which are powerful proteins released by white blood cells (neutrophils) that can damage lung tissue when overactive.
By blocking DPP1, brensocatib reduces harmful inflammation and slows the destructive cycle of infection and lung damage that defines bronchiectasis.
Understanding Bronchiectasis
Bronchiectasis affects over 300,000 people in the UK, particularly older adults and women. It leads to symptoms such as:
- Persistent cough
- Daily sputum (phlegm) production
- Frequent chest infections
- Fatigue and breathlessness
Treatment has traditionally focused on antibiotics, chest physiotherapy, and inhaled medications. However, these manage symptoms and kill bacteria without addressing the underlying inflammatory disease process. Brensocatib offers a new approach by directly targeting inflammation.
Clinical Trials of Brensocatib
Brensocatib has been evaluated in two major clinical trials: WILLOW (Phase 2) and ASPEN (Phase 3). Both trials tested its ability to reduce pulmonary exacerbations, which are flare-ups of bronchiectasis that often require hospital care or antibiotics.
Phase 2: The WILLOW Trial
- Participants: 256 adults with NCFBE and ≥2 exacerbations in the past year.
- Design: Randomised, double-blind, placebo-controlled.
- Treatment: Brensocatib 10 mg or 25 mg once daily vs placebo.
- Duration: 24 weeks.
Key findings (published in The Lancet Respiratory Medicine, 2021):
- Both doses of brensocatib significantly reduced the frequency of exacerbations.
- Patients had longer time to their first exacerbation.
- Marked reductions in neutrophil protease activity confirmed the drug’s biological effect.
Adverse events included tooth discolouration, rash, and mild gastrointestinal issues, but the treatment was generally well tolerated.
Phase 3: The ASPEN Trial
In May 2025, the full results of the pivotal ASPEN trial were published in The New England Journal of Medicine. This was a larger, longer study that confirmed the benefits of brensocatib.
- Participants: 1,682 adults with NCFBE and ≥2 exacerbations in the previous year.
- Design: International, randomised, double-blind, placebo-controlled.
- Treatment: Brensocatib 10 mg once daily vs placebo.
- Duration: 52 weeks.
Results:
- Annualised rate of exacerbations:
- Brensocatib: 0.78 exacerbations/year
- Placebo: 1.03 exacerbations/year
- Rate ratio: 0.75 (P < 0.001)
- Time to first exacerbation: Significantly longer in the brensocatib group.
- Neutrophil enzyme activity: Substantially reduced, confirming the drug’s mechanism of action.
- Quality of life (St. George’s Respiratory Questionnaire):
- Improvements observed, but did not reach statistical significance.
Adverse Effects:
- Common side effects:
- Tooth and gum discolouration
- Periodontal disease
- Skin rash
- Nausea and diarrhoea
- Serious adverse events: Occurred at similar rates in both groups.
The trial confirmed that brensocatib reduces exacerbations, delays their onset, and is generally well tolerated.
Reference:
Chalmers JD, et al. Brensocatib in Non–Cystic Fibrosis Bronchiectasis. N Engl J Med. 2025
FDA Approval: A Landmark Moment
On 18 April 2025, the U.S. Food and Drug Administration (FDA) approved brensocatib for adults with NCFBE who have had two or more exacerbations in the past 12 months.
This approval is historic and it marks the first licensed therapy to directly address the inflammatory mechanisms in bronchiectasis, rather than just controlling infections.
When Will Brensocatib Be Available in the UK?
Brensocatib is not yet available on the NHS, but regulatory steps are in motion:
- Insmed has submitted a marketing authorisation application to the MHRA.
- NICE will assess whether the treatment is cost-effective for NHS use.
If approved, brensocatib could be made available in the UK by early 2026. Experts are hopeful, given the high unmet need.
Why Brensocatib Is a Breakthrough for Patients
For the first time, bronchiectasis patients have a treatment that:
- Reduces the number of exacerbations
- Delays disease progression
- Targets the underlying inflammation
- Offers once-daily oral dosing
This is a shift from reactive care (treating infections) to proactive, hopefully, disease-modifying therapy.
Conclusion
With FDA approval now secured and robust clinical evidence published in The New England Journal of Medicine, brensocatib represents a major milestone in bronchiectasis care. Its expected UK launch is highly anticipated by both patients and clinicians.
As we await MHRA and NICE decisions, brensocatib stands out as the first drug to address the root cause of this under-recognised respiratory condition, offering hope to thousands of people living with bronchiectasis. Once available, and people living with bronchiectasis are using it, we will be able to see what the effect is outside of the clinic trials.