Insmed Provides Clinical and Business Update

Rhea-AI Summary

Insmed (Nasdaq: INSM) announced 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, and Insmed has discontinued the CRSsNP program effective immediately.

Topline placebo-adjusted least-squares means for 28-day average sTSS at Week 24 were placebo -2.44, brensocatib 10 mg -2.21, and brensocatib 40 mg -2.33. Safety was consistent with prior studies with no new signals. The company also acquired INS1148, a Phase 2–ready monoclonal antibody targeting SCF248, and plans initial development in interstitial lung disease and moderate-to-severe asthma.

Positive

• Acquired INS1148, a Phase 2–ready monoclonal antibody
• Plans to advance INS1148 in interstitial lung disease and moderate-to-severe asthma
• Safety profile: no new safety signals observed at up to 40 mg

Negative

• BiRCh failed primary and secondary efficacy endpoints in CRSsNP (Dec 17, 2025)
• Program discontinued for brensocatib in CRSsNP, ending development in this indication
• Placebo vs 40 mg sTSS LS mean: placebo -2.44 vs brensocatib 40 mg -2.33 (no improvement)

Key Figures

Sample size 10 mg arm 99 patients Brensocatib 10 mg once daily CRSsNP Phase 2b BiRCh study arm

Sample size 40 mg arm 93 patients Brensocatib 40 mg once daily CRSsNP Phase 2b BiRCh study arm

Sample size placebo arm 95 patients Placebo arm in CRSsNP Phase 2b BiRCh study

Primary endpoint LS mean -2.44 Placebo LS mean change in sTSS at Week 24

Primary endpoint LS mean -2.21 Brensocatib 10 mg LS mean change in sTSS at Week 24

Primary endpoint LS mean -2.33 Brensocatib 40 mg LS mean change in sTSS at Week 24

Any TEAE 10 mg 63.6% Treatment-emergent adverse events in brensocatib 10 mg arm

Any TEAE 40 mg 69.9% Treatment-emergent adverse events in brensocatib 40 mg arm

Market Reality Check

$174.09 Last Close

Volume Volume 3,628,122 is 21% above the 20-day average of 3,003,450. normal

Technical Price 200.67 is trading above the 200-day MA at 120.12.

Peers on Argus

INSM is up 1.9% while key biotech peers show mixed, mostly negative moves (e.g., BNTX -1.37%, REGN -0.83%, GMAB -1.09%, ONC +1.07%), indicating a company-specific reaction.

Historical Context

Date	Event	Sentiment	Move	Catalyst
Dec 09	Scientific conference data	Positive	-1.2%	Multiple ERS 2025 presentations, including Phase 2b and Phase 3 brensocatib data.
Dec 04	Equity inducement grants	Neutral	-0.8%	Inducement RSUs and options granted to 92 new employees.
Nov 18	EU drug approval	Positive	+2.1%	European Commission approval of BRINSUPRI for NCFB patients in the EU.
Nov 13	CSR initiative	Neutral	-1.8%	Global Day of Good with 1,200 employees in volunteer activities worldwide.
Nov 05	Investor conferences	Neutral	+2.3%	Management presentations at Jefferies and Evercore healthcare investor conferences.

Pattern Detected

Recent news reactions mostly aligned with event tone, with one notable divergence on a positive scientific/medical data presentation.

Recent Company History

This announcement follows a series of scientific, regulatory, and corporate updates. In mid‑November, the European Commission approved BRINSUPRI for NCFB, which saw a 2.14% price rise. Earlier, Q3 2025 results detailed growing product revenues and higher operating losses. Recent items also included conference presentations, inducement equity grants, volunteer initiatives, and investor conference appearances, with generally modest single‑day price moves. Against that backdrop, today’s failed CRSsNP study and new INS1148 acquisition mark a pipeline rebalancing rather than a first entry into respiratory indications.

Market Pulse Summary

This announcement combines a clinical setback with a pipeline expansion. The Phase 2b BiRCh study in CRSsNP did not meet primary or secondary endpoints, leading to discontinuation of that program, though safety remained consistent. At the same time, Insmed acquired INS1148, a Phase 2‑ready monoclonal antibody targeting SCF248 for respiratory and immunological diseases. Investors may watch upcoming Phase 2 designs, additional brensocatib data readouts, and evolving revenue trends from existing products as key markers of execution.

Key Terms

phase 2b medical

"the Phase 2b BiRCh study of brensocatib in patients with chronic"

Phase 2b is a stage in the development of a new medicine or treatment where researchers test its effectiveness and safety in a larger group of people. This step helps determine whether the treatment works well enough to move forward and if it has manageable side effects, which is important for investors because successful results can lead to potential approval and market opportunity.

chronic rhinosinusitis without nasal polyps medical

"brensocatib in patients with chronic rhinosinusitis without nasal polyps (CRSsNP)"

Chronic rhinosinusitis without nasal polyps is a long-lasting inflammation of the nose and sinus linings that causes congestion, facial pressure, reduced smell and recurrent infections but does not involve growths called nasal polyps. For investors, it matters because its persistent symptoms drive ongoing demand for medications, procedures and medical devices, influence healthcare spending and clinical trial activity, and affect regulatory approvals and market size much like a chronic maintenance problem keeps repair and service businesses in steady demand.

monoclonal antibody medical

"the acquisition of INS1148, an investigational monoclonal antibody with the potential"

A monoclonal antibody is a laboratory-made protein designed to recognize and attach to a specific target in the body, such as a disease-causing substance or cell. It functions like a highly precise lock-and-key tool, helping to treat or detect illnesses. For investors, companies developing monoclonal antibodies can represent promising opportunities in the healthcare sector, especially as these treatments often address unmet medical needs.

treatment-emergent adverse event medical

"Treatment-emergent adverse event (TEAE) percentages were:"

An event is called a treatment-emergent adverse event when a new or worsening unwanted health effect appears after a person starts a drug or medical treatment, typically measured from the first dose onward in clinical studies. Investors watch these events because they can stop or slow product approval, raise development costs, or undermine market confidence—like a widely reported defect in a new gadget that triggers recalls and damages sales.

least squares (ls) mean technical

"Topline results from each treatment arm were as follows: placebo least squares (LS) mean"

Least squares (LS) mean is an adjusted average calculated from a statistical model that removes the influence of other factors so groups can be compared on a level playing field. Think of it as the average outcome you would expect if everyone being compared had the same mix of background characteristics, like age or starting size. For investors, LS means matter because they give a fairer view of performance or effect sizes in studies and reports, helping avoid misleading conclusions driven by imbalances in the data.

interstitial lung disease medical

"advance Phase 2 development programs for INS1148 initially in interstitial lung disease"

A group of lung conditions that cause inflammation and scarring of the thin tissue between the air sacs, which makes it harder for oxygen to pass into the blood; imagine the lungs’ fine filters becoming stiff and less effective. Investors care because reports of interstitial lung disease can affect a drug’s safety profile, trigger regulatory warnings or label changes, and shift demand for treatments or create liability risks that influence a company’s valuation.

stem cell factor medical

"target a specific isoform of Stem Cell Factor SCF248, which prevents"

A naturally occurring protein that acts like a fertilizer for stem cells, helping them survive, divide and turn into blood or other tissue cells by binding to a receptor on their surface. Investors care because this protein is a key ingredient or drug target in therapies and lab-grown cell products; its biology affects clinical success, safety, manufacturing complexity and commercial potential of regenerative medicines and certain cancer treatments.

c-kit signaling medical

"prevents only the inflammatory cascade downstream of c-Kit signaling, while leaving"

c-kit signaling is a cell communication system centered on the c-kit protein, a receptor on the surface of certain cells that receives a chemical “call” telling the cell to grow, survive, move, or become a specific cell type; think of it as a light switch or phone line that turns on programs inside a cell. It matters to investors because drugs that block or enhance this pathway can treat cancers, blood disorders, or regenerative conditions, so progress in related trials, approvals, or safety findings can strongly affect the value of biotech companies working on those therapies.

AI-generated analysis. Not financial advice.

—Phase 2b BiRCh Study of Brensocatib in CRSsNP Did Not Meet Primary or Secondary Efficacy Endpoints; Safety Consistent with Previous Studies; Insmed Discontinues CRSsNP Program—

—Company Acquires Phase 2 Ready Monoclonal Antibody for Potential Respiratory and Immunological & Inflammatory Indications—

BRIDGEWATER, N.J., Dec. 17, 2025 /PRNewswire/ -- Insmed Incorporated (Nasdaq:INSM), a people-first global biopharmaceutical company striving to deliver first- and best-in-class therapies to transform the lives of patients facing serious diseases, announced today that the Phase 2b BiRCh study of brensocatib in patients with chronic rhinosinusitis without nasal polyps (CRSsNP) did not meet its primary or secondary efficacy endpoints in either the 10 mg or 40 mg treatment arms. Brensocatib was well tolerated, with no new safety signals identified, including in the 40 mg arm, which is the highest dose Insmed has studied to date. Insmed has discontinued its development program of brensocatib in CRSsNP effective immediately and intends to present these data at a future congress.

"Given that there are no animal models in this disease, the purpose of this proof-of-concept study was to determine if brensocatib could provide treatment benefit to patients with CRSsNP," said Martina Flammer, M.D., MBA, Chief Medical Officer of Insmed. "While we are disappointed in the results, they provided us with a clear answer. We extend our sincerest gratitude to the patients and investigators who made the BiRCh study possible."

In the study, a negative score in the primary endpoint of change from baseline to the 28-day average of daily Sinus Total Symptom Score (sTSS) at Week 24 indicated an improvement. Topline results from each treatment arm were as follows: placebo least squares (LS) mean was -2.44; brensocatib 10 mg LS mean was -2.21; and brensocatib 40 mg LS mean was -2.33. Treatment-emergent adverse event (TEAE) percentages were:

	Brensocatib 10 mg Once Daily (N=99)	Brensocatib 40 mg Once Daily (N=93)	Placebo (N=95)
Any TEAE, n(%)	63 (63.6)	65 (69.9)	62 (65.3)
Serious TEAE, n(%)	2 (2.0)	3 (3.2)	2 (2.1)
Severe TEAE, n(%)	0	0	3 (3.2)

Acquisition of Phase 2 Ready Asset: INS1148
Insmed also announced today the acquisition of INS1148, an investigational monoclonal antibody with the potential to be a first-in-class therapy to address respiratory and immunological and inflammatory diseases with high unmet need. Through its novel mechanism of action, INS1148 has the potential to preferentially target a specific isoform of Stem Cell Factor SCF248, which prevents only the inflammatory cascade downstream of c-Kit signaling, while leaving its critical homeostatic and tissue healing pathways intact. Insmed plans to advance Phase 2 development programs for INS1148 initially in interstitial lung disease and moderate-to-severe asthma. INS1148 (formerly known as OpSCF) was developed by Opsidio, a private, clinical-stage company.

Dr. Flammer added, "The acquisition of INS1148 adds a clinical-stage monoclonal antibody with a novel mechanism of action to our growing pipeline. We look forward to advancing this potentially first-in-class therapy in multiple serious diseases."

About the Phase 2b BiRCh Study

The Phase 2b trial of brensocatib in patients with CRSsNP was a randomized, double-blind, parallel-group, placebo-controlled, multicenter study to evaluate the efficacy and safety of brensocatib compared to placebo. The study was conducted at 104 sites globally, and a total of 288 patients were randomized 1:1:1 to receive either brensocatib 10 mg (n=99), brensocatib 40 mg (n=94), or placebo (n=95) daily for 24 weeks in addition to daily treatment with mometasone furoate nasal spray background therapy. The primary endpoint was change from baseline in the 28-day average of daily sTSS at Week 24. Secondary endpoints included changes in percentage of sinus opacification, Sino-Nasal Outcome Test 22 score, modified Lund-MacKay CT score, 28-day average of daily Nasal Congestion score, 28-day average of daily Peak Nasal Inspiratory Flow, as well as proportion of participants requiring rescue therapy and mean brensocatib plasma concentration.

About Insmed

Insmed Incorporated is a people-first global biopharmaceutical company striving to deliver first- and best-in-class therapies to transform the lives of patients facing serious diseases. The Company is advancing a diverse portfolio of approved and mid- to late-stage investigational medicines as well as cutting-edge drug discovery focused on serving patient communities where the need is greatest. Insmed's most advanced programs are in pulmonary and inflammatory conditions, including two approved therapies to treat chronic, debilitating lung diseases. The Company's early-stage programs encompass a wide range of technologies and modalities, including gene therapy, AI-driven protein engineering, protein manufacturing, RNA end-joining, and synthetic rescue.

Headquartered in Bridgewater, New Jersey, Insmed has offices and research locations throughout the United States, Europe, and Japan. Insmed is proud to be recognized as one of the best employers in the biopharmaceutical industry, including spending five consecutive years as the No. 1 Science Top Employer. Visit www.insmed.com to learn more or follow us on LinkedIn, Instagram, YouTube, and X.

Forward-looking Statements

This press release contains forward-looking statements that involve substantial risks and uncertainties. "Forward-looking statements," as that term is defined in the Private Securities Litigation Reform Act of 1995, are statements that are not historical facts and involve a number of risks and uncertainties. Words herein such as "may," "will," "should," "could," "would," "expects," "plans," "anticipates," "believes," "estimates," "projects," "predicts," "intends," "potential," "continues," and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) may identify forward-looking statements.

The forward-looking statements in this presentation are based upon the Company's current expectations and beliefs, and involve known and unknown risks, uncertainties and other factors, which may cause the Company's actual results, performance and achievements and the timing of certain events to differ materially from the results, performance, achievements or timing discussed, projected, anticipated or indicated in any forward-looking statements. Such risks, uncertainties and other factors include, among others, the following: the risk that the full data set from the BiRCh study will not be consistent with the topline results of the BiRCh study; failure to successfully conduct future clinical trials, such as the Company's planned Phase 2 studies of INS1148 in interstitial lung disease and moderate-to-severe asthma, including due to the Company's potential inability to enroll or retain sufficient patients to conduct and complete the trials or generate data necessary for regulatory approval, among other things; development of unexpected safety or efficacy concerns related to its product candidates; failure of third parties on which the Company is dependent to manufacture sufficient quantities of drug product for clinical needs, to conduct the Company's clinical trials, or to comply with the Company's agreements or laws and regulations that impact the Company's business or agreements with the Company; failure to obtain regulatory approval for the Company's product candidates; inaccuracies in the Company's estimates of the size of the potential markets for its product candidates or in data the Company has used to identify physicians; expected rates of patient uptake, duration of expected treatment, or expected patient adherence or discontinuation rates, if the Company's product candidates are approved; inability of the Company or the Company's third-party manufacturers to comply with regulatory requirements related to the Company's product candidates; the Company's inability to obtain adequate reimbursement from government or third-party payors and acceptance prices for its product candidates, if approved; restrictions or other obligations imposed on the Company by agreements related to its product candidates and failure to comply with our obligations under such agreements; risks that the Company's clinical studies will be delayed or that serious side effects will be identified during drug development; the strength and enforceability of the Company's intellectual property rights or the rights of third parties; risks that the Company is unable to successfully integrate and develop products obtained through acquisition from third parties, such as INS1148; and the cost and potential reputational damage resulting from litigation to which the Company may become a party, including product liability claims.

The Company may not actually achieve the results, plans, intentions or expectations indicated by the Company's forward-looking statements because, by their nature, forward-looking statements involve risks and uncertainties because they relate to events and depend on circumstances that may or may not occur in the future. For additional information about the risks and uncertainties that may affect the Company's business, please see the factors discussed in Item 1A, "Risk Factors," in the Company's Annual Report on Form 10-K for the year ended December 31, 2024 and any subsequent Company filings with the Securities and Exchange Commission (SEC).

The Company cautions readers not to place undue reliance on any such forward-looking statements, which speak only as of the date of this press release. The Company disclaims any obligation, except as specifically required by law and the rules of the SEC, to publicly update or revise any such statements to reflect any change in expectations or in events, conditions or circumstances on which any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in the forward-looking statements.

Contact:

Investors

Bryan Dunn
Vice President, Investor Relations
(646) 812-4030
investor.relations@insmed.com

Media

Claire Mulhearn
Vice President, Corporate Communications
(862) 842-6819
media@insmed.com

 

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SOURCE Insmed Incorporated

FAQ

What did Insmed (INSM) announce on December 17, 2025 about brensocatib in CRSsNP?

Insmed said the Phase 2b BiRCh study did not meet primary or secondary endpoints and the CRSsNP program is discontinued.

What were the topline sTSS results for brensocatib 10 mg and 40 mg in the BiRCh study?

Topline least-squares means at Week 24 were: placebo -2.44, brensocatib 10 mg -2.21, and brensocatib 40 mg -2.33.

Did brensocatib show any new safety concerns in the Phase 2b BiRCh study?

No new safety signals were identified; safety was reported as consistent with prior studies, including at 40 mg.

What asset did Insmed acquire and what indications will it pursue for INSM1148?

Insmed acquired INS1148, a Phase 2–ready monoclonal antibody, and plans to advance it in interstitial lung disease and moderate-to-severe asthma.

How does the brensocatib discontinuation affect Insmed’s pipeline (INSM)?

The company discontinued the CRSsNP program but added INS1148 to its pipeline to pursue respiratory and inflammatory indications.

When will Insmed present the BiRCh study data for INSM’s brensocatib trial?

Insmed intends to present the BiRCh data at a future scientific congress (date not specified).