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Insmed (INSM) reports Phase 2b brensocatib CRSsNP data and acquires INS1148

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Form Type
8-K

Rhea-AI Filing Summary

Insmed Incorporated reported topline results from its Phase 2b BiRCh study of brensocatib in patients with chronic rhinosinusitis without nasal polyps (CRSsNP) and announced that it has discontinued development of brensocatib for this indication. The 24‑week, randomized, double‑blind, placebo‑controlled study enrolled 288 patients across 104 global sites, comparing once‑daily brensocatib 10 mg, brensocatib 40 mg, and placebo, all on top of mometasone furoate nasal spray.

The primary endpoint was change from baseline in the 28‑day average daily Sinus Total Symptom Score at Week 24. Least squares mean changes were -2.44 for placebo, -2.21 for brensocatib 10 mg, and -2.33 for brensocatib 40 mg. Brensocatib was observed to be well tolerated, with similar rates of treatment‑emergent and serious adverse events across arms. Insmed also disclosed it has acquired INS1148, an investigational monoclonal antibody it plans to develop for respiratory, immunological, and inflammatory diseases with high unmet need.

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Insights

Insmed is ending brensocatib development in CRSsNP after modest Phase 2b results while adding a new antibody asset, INS1148.

The BiRCh Phase 2b study tested brensocatib 10 mg and 40 mg once daily versus placebo in 288 CRSsNP patients over 24 weeks, all receiving mometasone furoate nasal spray. The primary endpoint was improvement in the 28‑day average daily Sinus Total Symptom Score at Week 24. Reported least squares mean changes were -2.44 for placebo, -2.21 for 10 mg brensocatib, and -2.33 for 40 mg brensocatib, indicating similar symptom score changes across arms based on these topline figures.

Safety was described as well tolerated, with comparable treatment‑emergent and serious adverse event rates and no new safety signals. Despite this tolerability profile, Insmed has discontinued the brensocatib program in CRSsNP, suggesting the efficacy data do not support further development in this indication based on the company’s assessment. In parallel, Insmed acquired INS1148, an investigational monoclonal antibody it plans to move into Phase 2 studies in interstitial lung disease and moderate‑to‑severe asthma, subject to successful trial conduct and regulatory interactions as described in its forward‑looking statements.

The shift away from brensocatib in CRSsNP toward INS1148 focuses the pipeline on other respiratory and immunological indications. Actual outcomes will depend on full BiRCh data, execution of planned Phase 2 trials for INS1148 in interstitial lung disease and asthma, manufacturing reliability, regulatory review, and the risk factors highlighted in Insmed’s prior annual and subsequent SEC reports.


UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of
The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 17, 2025

INSMED INCORPORATED
(Exact name of registrant as specified in its charter)

Virginia
 
000-30739
 
54-1972729
(State or other jurisdiction of incorporation)
 
(Commission File Number)
 
(IRS Employer Identification No.)

700 US Highway 202/206
Bridgewater, New Jersey
 
08807
(Zip Code)
(Address of principal executive offices)
   

Registrant’s telephone number, including area code: (908) 977-9900

Not Applicable
(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:
 
Title of each class
Trading Symbol(s)
Name of each exchange on which registered
Common Stock, par value $0.01 per share
INSM
Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR 230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR 240.12b-2).

Emerging growth company

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐



ITEM 7.01 — Regulation FD Disclosure.

On December 17, 2025, Insmed Incorporated (the “Company”) issued a press release announcing topline efficacy and safety results from the Phase 2b BiRCh study of brensocatib in patients with chronic rhinosinusitis without nasal polyps (“CRSsNP”) and the acquisition of INS1148, an investigational monoclonal antibody that the Company plans to develop for respiratory and immunological and inflammatory diseases with high unmet need. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference.

The information contained in this Item 7.01, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.

ITEM 8.01 — Other Events.

On December 17, 2025, the Company issued a press release announcing topline efficacy and safety results from the Phase 2b BiRCh study of brensocatib for patients with CRSsNP. The BiRCh study 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 Sinus Total Symptom Score (“sTSS”) at Week 24.

Results from each treatment arm for the primary endpoint of change from baseline to the 28-day average of daily sTSS at Week 24 were as follows: placebo least squares (“LS”) mean was -2.44; the 10 mg brensocatib treatment arm LS mean was -2.21; and the 40 mg brensocatib treatment arm LS mean was -2.33. Brensocatib was observed to be well tolerated, with no new safety signals identified. The percentage of treatment-emergent adverse events (“TEAEs”) 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)

The Company has discontinued its development program of brensocatib in CRSsNP and intends to present these data at a future congress.

Forward-Looking Statements

The forward-looking statements in this Current Report on Form 8-K 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 (the “SEC”).

The Company cautions readers not to place undue reliance on any such forward-looking statements, which speak only as of the date hereof. 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.

ITEM 9.01 – Financial Statements and Exhibits.

(d) Exhibits

Exhibit
No.
 
Description
99.1
 
Press release issued by Insmed Incorporated on December 17, 2025.
104
 
Cover Page Interactive Date File (embedded within the Inline XBRL document).


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: December 17, 2025
INSMED INCORPORATED
   
 
By:
/s/ Michael A. Smith
 
Name:
Michael A. Smith
 
Title:
Chief Legal Officer and Corporate Secretary



FAQ

What did Insmed (INSM) announce about the brensocatib BiRCh Phase 2b study?

Insmed announced topline efficacy and safety results from the Phase 2b BiRCh study of brensocatib in patients with chronic rhinosinusitis without nasal polyps (CRSsNP). The study compared 10 mg and 40 mg once‑daily brensocatib to placebo over 24 weeks with mometasone furoate nasal spray as background therapy.

How many patients were enrolled in Insmed's BiRCh Phase 2b CRSsNP trial?

The BiRCh Phase 2b study enrolled a total of 288 patients with CRSsNP at 104 sites globally. Patients were randomized 1:1:1 to brensocatib 10 mg (n=99), brensocatib 40 mg (n=94), or placebo (n=95) once daily for 24 weeks.

What were the primary endpoint results in Insmed's brensocatib BiRCh trial?

The primary endpoint was change from baseline in the 28‑day average daily Sinus Total Symptom Score at Week 24. Least squares mean changes were -2.44 for placebo, -2.21 for brensocatib 10 mg, and -2.33 for brensocatib 40 mg.

How did safety look in the brensocatib BiRCh Phase 2b study for Insmed?

Brensocatib was observed to be well tolerated with no new safety signals identified. Any treatment‑emergent adverse events occurred in 63.6% of patients on 10 mg, 69.9% on 40 mg, and 65.3% on placebo, with serious treatment‑emergent adverse events reported at low and similar rates across arms.

Is Insmed continuing to develop brensocatib for CRSsNP?

No. Insmed stated that it has discontinued its development program of brensocatib in CRSsNP following the Phase 2b BiRCh results. The company intends to present the data at a future medical congress.

What is INS1148 and how does it fit into Insmed's pipeline?

Insmed disclosed the acquisition of INS1148, an investigational monoclonal antibody. The company plans to develop INS1148 for respiratory, immunological, and inflammatory diseases with high unmet need, including planned Phase 2 studies in interstitial lung disease and moderate‑to‑severe asthma, subject to successful development.

Where can investors find more details on Insmed's risks and forward-looking statements?

Insmed referenced risk factors in Item 1A, "Risk Factors", in its Annual Report on Form 10‑K for the year ended December 31, 2024, and in subsequent SEC filings. The company emphasized that forward‑looking statements are subject to numerous risks and uncertainties.
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