UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
FORM
CURRENT REPORT
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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 | ||
Exhibit 99.1

Pulmatrix and Cullgen Continue to Pursue Merger While Granting Each Other Waivers to Explore Alternatives
Pulmatrix continues to support Cullgen in seeking approval for their merger from the China Securities Regulatory Commission
Framingham, Mass., December 18, 2025 – Pulmatrix, Inc. (“Pulmatrix” or the “Company”) (Nasdaq: PULM), a biopharmaceutical company that has focused on the development of novel inhaled therapeutic products intended to prevent and treat migraine and respiratory diseases with important unmet medical needs using its patented iSPERSE™ technology, today announced that Pulmatrix and Cullgen Inc. (“Cullgen”) have mutually agreed to waive the “No Solicitation” clause in the Merger Agreement signed in November 2024 in order to permit each party to explore alternate transactions while continuing to work toward merger approval from the China Securities Regulatory Commission (the “CSRC”).
Peter Ludlum, Interim Chief Executive Officer of Pulmatrix, commented, “Regarding the Merger Agreement that we signed in November 2024, our Form S-4 filing was declared effective in May 2025, and our stockholders approved the Merger Agreement and related transactions in June 2025. However, we have not yet received approval from the CSRC. Therefore, we feel that it is appropriate to explore any opportunistic transactions that may benefit our respective companies while still seeking approval from the CSRC.”
Proposed Merger with Cullgen
As previously reported, on November 13, 2024, the Company entered into an agreement and plan of merger with Cullgen, as amended by Amendment No. 1 thereto on April 7, 2025 (the “Merger Agreement” and the transactions contemplated thereunder, collectively, the “Merger”).
Additional information about the Merger Agreement and the proposed Merger was previously disclosed in a registration statement on Form S-4 (File No. 333-284993) initially filed with the Securities and Exchange Commission (the “SEC”) on February 14, 2025, as amended on April 17, 2025, and May 7, 2025, and declared effective on May 9, 2025.
On June 16, 2025, the Company held a special meeting in lieu of the annual meeting of Pulmatrix stockholders, at which meeting the Company’s stockholders approved the Merger and related proposals. The closing of the Merger is subject to certain closing conditions, including Nasdaq’s approval of the listing of the shares of Pulmatrix common stock to be issued in connection with the Merger and approval from the China Security Regulatory Commission.
If the proposed Merger is completed, the business of Cullgen will continue as the business of the combined company.
The Company’s total cash and cash equivalents balance as of September 30, 2025, was $4.8 million. The Company anticipates that its cash position, based on current operational efficiencies and prioritization of spending, is sufficient to fund its operations into at least the fourth quarter of 2026.

Pulmatrix Clinical Assets and Proprietary iSPERSE™ Technology
iSPERSE™ Technology
| ● | iSPERSE™ particles are engineered with a small, dense and dispersible profile to exceed the performance of traditional dry powder particles as the iSPERSE™ particles have the dispersibility advantages of porous engineered particles. Pulmatrix believes this results in superior drug delivery compared to traditional oral and injectable forms of treatment for certain diseases. | |
| ● | As of September 30, 2025, Pulmatrix’s patent portfolio related to iSPERSE™ included approximately 146 granted patents, 18 of which are U.S.-granted patents, plus approximately 50 pending patent applications in the U.S. and other jurisdictions. |
PUR3100
| ● | PUR3100 is an orally inhaled dihydroergotamine (“DHE”) engineered with Pulmatrix’s iSPERSE™ dry powder inhalation technology for the treatment of acute migraine and is a Phase 2-ready asset with a Food and Drug Administration acceptance of an Investigational New Drug (“IND”) application for PUR3100 and receipt of a “study may proceed” letter to proceed with a Phase 2 study. The IND includes a Phase 2 clinical protocol where safety and preliminary efficacy of PUR3100 will be investigated in patients with acute migraine. | |
| ● | The Phase 2 IND builds on the Phase 1 trial results of PUR3100, which were published in 2024 in the peer-reviewed publication, Headache: The Journal of Head and Face Pain. The study showed that PUR3100 achieved peak exposures in the targeted therapeutic range and time to maximum concentration occurred at five minutes after dosing at all dosing levels. The PUR3100 dose groups also showed a lower incidence of nausea and no vomiting compared to observations of nausea and vomiting in the intravenously (“IV”) administered DHE dose group. |
PUR1800
| ● | PUR1800 is a Narrow Spectrum Kinase Inhibitor (“NSKI”), engineered with our iSPERSE™ technology, for the treatment of acute exacerbations in chronic obstructive pulmonary disease (“AECOPD”). In 2023, Pulmatrix presented complete results from a Phase 1b study of PUR1800 for AECOPD, indicating PUR1800 was well-tolerated with no observed safety signals. The topline data, along with the results from chronic toxicology studies, support the continued development of PUR1800 for the treatment of AECOPD and other inflammatory respiratory diseases. | |
| ● | In 2024, Pulmatrix published an abstract titled “Ex vivo evaluation of the potential for Narrow Spectrum Kinase inhibitors as a treatment for Idiopathic Pulmonary Fibrosis”. |
PUR1900
| ● | PUR1900 is the Company’s inhaled iSPERSE™ formulation of the antifungal drug itraconazole being investigated for various indications. The Company and its partner, Cipla, wound down a Phase 2b trial that the Company was operating in 2024. Cipla has continued clinical development outside the United States and in 2025 advised Pulmatrix that they have completed their Phase 2 study in India and have been approved by India’s Central Drug Standard Control Organization to proceed with a Phase 3 clinical trial. | |
| ● | Pulmatrix will receive 2% royalties on any potential future net sales by Cipla outside the United States should Cipla successfully market PUR1900 outside the United States. Within the United States, the Company and Cipla will seek to monetize PUR1900 for indications where an orally inhaled antifungal may provide a therapeutic benefit or fulfill an unmet medical need. |

About Pulmatrix, Inc.
Pulmatrix is a biopharmaceutical company that has focused on the development of novel inhaled therapeutic products intended to prevent and treat migraine and respiratory diseases with important unmet medical needs using its patented iSPERSE™ technology. The Company’s proprietary product pipeline includes treatments for central nervous system (“CNS”) disorders such as acute migraine and serious lung diseases such as Chronic Obstructive Pulmonary Disease (“COPD”) and allergic bronchopulmonary aspergillosis (“ABPA”). Pulmatrix’s product candidates are based on its proprietary engineered dry powder delivery platform, iSPERSE™, which seeks to improve therapeutic delivery to the lungs by optimizing pharmacokinetics and reducing systemic side effects to improve patient outcomes.
For more on the Company’s inhaled product candidates please visit:
https://www.pulmatrix.com/pipeline.html.
Forward-Looking Statements
Certain statements in this press release that are forward-looking and not statements of historical fact are forward-looking statements within the meaning of the federal securities laws. Such forward-looking statements include, but are not limited to, statements of historical fact and may be identified by words such as “anticipates,” “assumes,” “believes,” “can,” “could,” “estimates,” “expects,” “forecasts,” “guides,” “intends,” “is confident that,” “may,” “plans,” “seeks,” “projects,” “targets,” and “would,” and their opposites and similar expressions are intended to identify forward-looking statements. Such forward-looking statements are based on the beliefs of management as well as assumptions made by and information currently available to management. Actual results could differ materially from those contemplated by the forward-looking statements as a result of certain factors, including, but not limited to, the consummation of and the exact timing of the proposed Merger with Cullgen, the receipt of applicable regulatory approvals in connection with the proposed Merger with Cullgen, and satisfaction of closing conditions thereunder, among others; the Company’s ability to divest its clinical assets on terms favorable to the Company, or at all, the Company’s ability to maintain compliance with the listing standards of the Nasdaq Capital Market; the Company’s ability to conduct its business and raise capital in the future when needed; delays in planned clinical trials; the ability to establish that potential products are efficacious or safe in preclinical or clinical trials; the ability to establish or maintain collaborations on the development of therapeutic candidates; the ability to obtain appropriate or necessary governmental approvals to market potential products; the ability to obtain future funding for developmental products and working capital and to obtain such funding on commercially reasonable terms; the Company’s ability to manufacture product candidates on a commercial scale or in collaborations with third parties; changes in the size and nature of competitors; the ability to retain key executives and scientists; the ability to secure and enforce legal rights related to the Company’s products, including patent protection. A discussion of these and other factors, including risks and uncertainties with respect to the Company, including the proposed Merger with Cullgen, is set forth in the Company’s filings with the Securities and Exchange Commission, including its most recent Annual Report on Form 10-K, as may be supplemented or amended by the Company’s Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. The Company disclaims any intention or obligation to revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.
Investor Contact:
Chuck Padala
Managing Director
LifeSci Advisors
646-627-8390