Written By: Pharmacally Medical News Desk
Insmed Incorporated has announced that its Phase 2b BiRCh study evaluating brensocatib in patients with chronic rhinosinusitis without nasal polyps (CRSsNP) did not meet its primary or secondary efficacy endpoints. The study evaluated two dose levels, 10 mg and 40 mg, and neither demonstrated a statistically significant benefit compared with placebo across the predefined outcome measures.
The BiRCh trial was designed to assess whether brensocatib could reduce symptoms and disease burden in adults living with CRSsNP, a chronic inflammatory condition of the sinuses characterized by nasal congestion, facial pain or pressure, and impaired quality of life. Unlike chronic rhinosinusitis with nasal polyps, CRSsNP has fewer targeted treatment options and remains a challenging condition to manage with current therapies.
Brensocatib is an oral, reversible inhibitor of dipeptidyl peptidase 1 (DPP1). By inhibiting DPP1, the drug aims to reduce the activation of neutrophil serine proteases, enzymes believed to drive inflammation and tissue damage in several neutrophil-mediated diseases. This mechanism has generated interest across multiple inflammatory conditions, including respiratory diseases, where neutrophilic inflammation plays a role.
Key outcome of the trial
The primary endpoint of the Phase 2b BiRCh study was the change from baseline in a validated CRSsNP symptom score over the treatment period. In the study, a negative change in the Sinus Total Symptom Score (sTSS) indicated symptom improvement; however, according to Insmed Incorporated, neither the 10 mg nor the 40 mg dose of brensocatib achieved a statistically significant improvement compared with placebo on this primary endpoint. Key secondary endpoints included additional patient-reported measures of sinus symptoms, assessments of disease severity and quality-of-life impact, and other supportive clinical or inflammatory markers relevant to CRSsNP. Across these secondary endpoints, both dose groups again failed to show meaningful separation from placebo, with symptom improvements that were modest, inconsistent, and not statistically significant.
Regarding safety, brensocatib was generally well tolerated, with no new or unexpected safety signals, and adverse events were mostly mild to moderate and comparable to placebo across both dose groups, consistent with its previously established safety profile.
Martina Flammer, M.D., MBA, Chief Medical Officer of Insmed Incorporated, said the BiRCh study was conducted as a proof-of-concept trial due to the lack of animal models for CRSsNP, and although the results were disappointing, they provided a clear outcome, while thanking the patients and investigators for their contribution to the study.
Insmed also stated that it has discontinued the development program for brensocatib in CRSsNP, effective immediately, and plans to present the full BiRCh study data at a future scientific congress.
References
Insmed Provides Clinical and Business Update, 17 Dec 2025, https://investor.insmed.com/2025-12-17-Insmed-Provides-Clinical-and-Business-Update