01—Abstract
Summary
Summary of the 8-K filed December 17, 2025. Cited figures are marked; the original filing is the authoritative source.
Insmed Incorporated (Nasdaq: INSM) reported on December 17, 2025 that the Phase 2b BiRCh study of brensocatib in chronic rhinosinusitis without nasal polyps (CRSsNP) did not meet its primary or secondary efficacy endpoints in either the 10 mg or 40 mg arms.
The primary endpoint was change from baseline in the 28-day average of daily Sinus Total Symptom Score at Week 24. Placebo's least squares mean was -2.44, versus -2.21 for the 10 mg arm and -2.33 for the 40 mg arm, where a negative score indicates improvement. The company said brensocatib was well tolerated with no new safety signals, including at 40 mg, the highest dose studied to date.
Insmed has discontinued the brensocatib CRSsNP development program effective immediately and intends to present the data at a future congress. In the same announcement, Insmed disclosed its acquisition of INS1148, an investigational monoclonal antibody that it describes as potentially first-in-class and as preferentially targeting a specific isoform of Stem Cell Factor. The company plans to advance INS1148 into Phase 2 development, initially in interstitial lung disease and moderate-to-severe asthma.
The filing states that INS1148 was developed by Opsidio, a private, clinical-stage company, and was formerly known as OpSCF. The filing does not disclose the acquisition consideration.
For investors, the key takeaways are the failed CRSsNP readout, which removes that indication from the pipeline, and the pivot toward a new clinical-stage asset in respiratory and immunological and inflammatory diseases. The filing's forward-looking statements flag the risk that full BiRCh data may differ from topline results and the risk that the company may be unable to integrate and develop INS1148.
02—Key points
Key Highlights
- Phase 2b BiRCh study of brensocatib in CRSsNP did not meet its primary or secondary efficacy endpoints in either the 10 mg or 40 mg arm.
- Primary endpoint LS mean change in 28-day average daily sTSS at Week 24: placebo -2.44, brensocatib 10 mg -2.21, brensocatib 40 mg -2.33.
- Brensocatib was well tolerated with no new safety signals, including at 40 mg, the highest dose studied to date.
- Insmed discontinued the brensocatib CRSsNP development program effective immediately; full data to be presented at a future congress.
- Insmed acquired INS1148, a clinical-stage monoclonal antibody developed by private company Opsidio, described as potentially first-in-class.
- Planned Phase 2 development of INS1148 initially in interstitial lung disease and moderate-to-severe asthma.
- The filing does not disclose the acquisition consideration for INS1148.
03—Questions
Frequently Asked Questions
Why did Insmed discontinue brensocatib in CRSsNP?
The Phase 2b BiRCh study did not meet its primary or secondary efficacy endpoints in either the 10 mg or 40 mg arm, so Insmed discontinued the CRSsNP development program effective immediately.
Did brensocatib show a safety problem in the BiRCh study?
The company stated that brensocatib was well tolerated with no new safety signals. Serious TEAEs were 2 (2.0%) at 10 mg, 3 (3.2%) at 40 mg and 2 (2.1%) on placebo, and no severe TEAEs occurred in either brensocatib arm, compared with 3 (3.2%) on placebo.
What is INS1148 and what is Insmed's plan for it?
INS1148 is an investigational monoclonal antibody that Insmed describes as having the potential to be first-in-class, with a mechanism that preferentially targets a specific isoform of Stem Cell Factor. Insmed plans to advance Phase 2 development initially in interstitial lung disease and moderate-to-severe asthma.
When will the full BiRCh data be presented?
Insmed stated it intends to present the data at a future congress. The filing does not specify which congress or when.
What risks does the filing highlight?
The forward-looking statements flag that the full BiRCh data set may not be consistent with the topline results, and that Insmed may be unable to successfully integrate and develop INS1148, among other risks such as clinical trial delays, safety findings and intellectual property challenges.
04—Continue