Full Breakdown
Insmed Discontinues Brensocatib Development Following Phase 2b Study Results
12/18/2025, 10:57:35 AM
Study Findings and Discontinuation of Brensocatib Program
Insmed Incorporated announced on December 17, 2025, that its Phase 2b BiRCh study of brensocatib, aimed at treating chronic rhinosinusitis without nasal polyps (CRSsNP), did not achieve its primary or secondary efficacy endpoints. The study, which involved 288 patients across 104 global sites, compared brensocatib at doses of 10 mg and 40 mg against a placebo over a 24-week period. The primary endpoint assessed the change from baseline in the 28-day average of daily Sinus Total Symptom Score (sTSS) at Week 24. Results indicated a placebo least squares (LS) mean score of -2.44, while the brensocatib groups recorded LS means of -2.21 and -2.33, respectively, demonstrating no significant improvement.
Despite the lack of efficacy, brensocatib was reported to be well tolerated, with no new safety signals identified. In light of these findings, Insmed has decided to discontinue the development program for brensocatib in CRSsNP. Chief Medical Officer Dr. Martina Flammer expressed disappointment in the results but acknowledged the study's clarity in determining the drug's effectiveness.
Acquisition of INS1148: A New Direction
In conjunction with the discontinuation of brensocatib, Insmed announced the acquisition of INS1148, an investigational monoclonal antibody that targets respiratory and immunological diseases. INS1148, previously known as OpSCF, is designed to preferentially inhibit the inflammatory cascade associated with c-Kit signaling while preserving essential tissue healing pathways. Insmed plans to initiate Phase 2 development programs for INS1148 in interstitial lung disease and moderate-to-severe asthma, marking a strategic shift in its therapeutic focus.
Dr. Flammer highlighted the potential of INS1148 as a first-in-class therapy, stating, "The acquisition of INS1148 adds a clinical-stage monoclonal antibody with a novel mechanism of action to our growing pipeline."
Official Statements & Responses
Insmed's announcement reflects a commitment to advancing innovative therapies despite setbacks. Dr. Flammer noted the importance of the BiRCh study in providing definitive answers regarding brensocatib's efficacy, thanking the patients and investigators involved for their contributions.
Criticism & Opposition
While the results of the BiRCh study were disappointing for Insmed, there has been no public dissent regarding the decision to discontinue the brensocatib program. However, the broader implications of such failures in clinical trials often raise concerns about the viability of drug development in complex disease areas like CRSsNP.
Conflicting Reports & Gaps
There are no conflicting reports regarding the efficacy of brensocatib in the BiRCh study; however, the absence of detailed data on the specific safety profile and adverse events associated with the treatment could be seen as a gap in the reporting.
Verbatim Quotes
“While we are disappointed in the results, they provided us with a clear answer.” — Dr. Martina Flammer, Chief Medical Officer of Insmed
“Flammer added, "The acquisition of INS1148 adds a clinical-stage monoclonal antibody with a novel mechanism of action to our growing pipeline.” — Dr. Martina Flammer, Chief Medical Officer of Insmed
