Pulmatrix (NASDAQ: PULM) waives Section 5.4 in Cullgen merger pact

Rhea-AI Filing Summary

Pulmatrix, Inc. reported that on December 17, 2025 it entered into a mutual waiver agreement with Cullgen Inc. and PLC Merger Sub, Inc. related to their existing Merger Agreement. The waiver allows all parties to forego compliance with Section 5.4 of the Merger Agreement, which had imposed certain restrictions on each party during the pre-closing period. The company stated that, aside from this specific waiver, the Merger Agreement remains in full force and effect and no other terms have been amended, waived, or modified. Pulmatrix also issued a press release on December 18, 2025 describing the waiver, which is furnished as an exhibit.

Insights

M&A and corporate governance analyst

Pulmatrix and Cullgen waive one interim merger covenant; core deal stands.

Pulmatrix, Cullgen, and PLC Merger Sub, Inc. signed a mutual waiver agreement on December 17, 2025. This agreement waives compliance with Section 5.4 of their existing Merger Agreement, which had placed restrictions on each party’s actions during the pre-closing period. The filing emphasizes that this is a targeted waiver of a specific section.

The Merger Agreement otherwise remains in full force and effect, with no other provisions amended, waived, or modified according to the disclosure. This means the main economic and structural terms of the planned combination are stated to be unchanged in this excerpt. A press release dated December 18, 2025 was furnished to provide public communication around this change.

For investors following the Pulmatrix–Cullgen transaction, this update highlights an adjustment to pre-closing operating restrictions rather than to closing conditions or consideration. Subsequent company filings may provide more detail on how waiving Section 5.4 interacts with the ongoing pre-closing period and any remaining steps toward completion.

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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

PULMATRIX, INC.

(Exact name of registrant as specified in its charter)

Delaware		001-36199		46-1821392
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

945 Concord Street, Suite 1217

Framingham, MA 01701

(Address of principal executive offices) (Zip Code)

(888) 355-4440

(Registrant’s telephone number, including area code)

N/A

(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:

☐	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 exchange on which registered
Common Stock, par value $0.0001 per share		PULM		The NASDAQ Stock Market LLC

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

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 18, 2025, Pulmatrix, Inc. (the “Company” or “Pulmatrix”) issued a press release announcing the signing of the Waiver Agreement (as defined below) in connection with the Agreement and Plan of Merger and Reorganization, dated as of November 13, 2024, by and between the Company, Cullgen Inc. (“Cullgen”), PCL Merger Sub, Inc., a wholly owned subsidiary of the Company and PCL Merger Sub II, LLC, a wholly owned subsidiary of the Company, as subsequently amended by Amendment No. 1 on April 7, 2025 (the “Merger Agreement”). A copy of the press release is furnished as Exhibit 99.1 hereto and is incorporated herein by reference.

The information in this Current Report on Form 8-K (including Exhibit 99.1 attached hereto) is being furnished pursuant to Item 7.01 and shall not be deemed to be filed for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise be subject to the liabilities of that section, nor shall it be deemed to be incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, whether made before or after the date hereof and regardless of any general incorporation language in such filing.

Item 8.01. Other Events

On December 17, 2025, the Company, Cullgen and PLC Merger Sub, Inc. (collectively, the “Parties”) entered into that certain mutual waiver agreement (the “Waiver Agreement”), pursuant to which the Parties agreed to mutually waive compliance with Section 5.4 of the Merger Agreement, which such provision imposes restrictions on each party during the Pre-Closing Period (as defined in the Merger Agreement). Except as expressly waived pursuant to the Waiver Agreement, the Merger Agreement remains in full force and effect in all respects, and no other provision of the Merger Agreement has otherwise been amended, waived, or modified.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.		Description
99.1		Press Release dated December 18, 2025 (furnished pursuant to Item 7.01)
104		Cover Page Interactive Data File (formatted as Inline XBRL)

SIGNATURES

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

	PULMATRIX, INC.
Date: December 18, 2025	By:	/s/ Peter Ludlum
		Peter Ludlum
		Interim Chief Executive Officer and Interim Chief Financial Officer

FAQ

What did Pulmatrix (PULM) announce regarding its merger with Cullgen?

Pulmatrix announced that on December 17, 2025, it entered into a mutual waiver agreement with Cullgen Inc. and PLC Merger Sub, Inc. This agreement waives compliance with Section 5.4 of their existing Merger Agreement, which had imposed restrictions on the parties during the pre-closing period, while leaving the rest of the Merger Agreement in place.

Does the waiver change the overall Pulmatrix–Cullgen Merger Agreement?

According to the disclosure, the waiver only affects Section 5.4 of the Merger Agreement. The company states that, except as expressly waived, the Merger Agreement remains in full force and effect in all respects and that no other provision has been amended, waived, or modified.

What is Section 5.4 related to in the Pulmatrix Merger Agreement?

The filing describes Section 5.4 as a provision that imposes restrictions on each party during the Pre-Closing Period. While the text does not provide the full wording of Section 5.4, it makes clear that this section governs what the parties can do before the merger closes and that compliance with it has now been mutually waived.

When was the Pulmatrix–Cullgen waiver agreement signed and disclosed?

The mutual waiver agreement was signed on December 17, 2025. Pulmatrix then issued a press release on December 18, 2025 describing the waiver, and this press release was furnished as Exhibit 99.1 to the current report.

What exhibits did Pulmatrix include with this current report?

Pulmatrix included two exhibits: Exhibit 99.1, which is the press release dated December 18, 2025 furnished under Item 7.01, and Exhibit 104, which is the cover page interactive data file formatted as Inline XBRL.

Is the Pulmatrix press release about the waiver considered filed or furnished?

The company states that the information provided under Item 7.01, including Exhibit 99.1, is being furnished, not filed, for purposes of Section 18 of the Exchange Act. It also notes that this information is not automatically incorporated by reference into Securities Act or Exchange Act filings.