Pulmatrix Files Merger Proxy for Reverse Merger With Eos SENOLYTIX

What happened

Pulmatrix, Inc. (Nasdaq: PULM), a clinical-stage pharmaceutical company, filed a definitive proxy statement (Form DEFM14A) with the SEC on September 25, 2026, ahead of a special meeting of stockholders scheduled for October 16, 2026 at 8:30 a.m. Eastern Time. The meeting will be held online only.

The filing asks stockholders to approve the company's merger with Eos SENOLYTIX, Inc., a privately held Delaware corporation. Under the Agreement and Plan of Merger signed March 26, 2026, a wholly owned Pulmatrix subsidiary, PUOS Merger Sub, Inc., will merge into Eos, and Eos will survive as a wholly owned Pulmatrix subsidiary. Eos is a privately held company; the filing identifies its sole stockholder as of March 26, 2026 as SENOTHERAPEUTIX, Inc., and states that Kevin Slawin, who is expected to become CEO of the combined company, holds a majority of SENOTHERAPEUTIX's voting power.

Pulmatrix common stock closed at $1.61 on the day the proxy was filed, down 3.59% from the prior close of $1.67, according to the price data. The filing itself cites September 24, 2026 — the last trading day before the proxy's date — when Pulmatrix closed at $1.67.

What the proxy asks stockholders to approve

The proxy sets out nine numbered proposals. The central one (Proposal No. 1) asks stockholders to approve the issuance of Pulmatrix common stock representing more than 20% of the shares outstanding immediately before the merger, to Eos stockholders, certain Eos noteholders, and to Palladium Capital Group, LLC as compensation for its M&A advisory work, and to approve the resulting change of control, under Nasdaq Listing Rules 5635(a) and 5635(b).

Other proposals would authorize a reverse stock split of Pulmatrix common stock at a ratio of one new share for every 2 to 10 outstanding shares (Proposal No. 2); increase authorized shares from 200,000,000 to 250,000,000 (Proposal No. 3); ratify CBIZ CPAs P.C. as auditor for fiscal 2026, with Stephano Slack LLC expected to be appointed if the merger closes (Proposal No. 4); elect two Class III directors (Proposal No. 5); hold advisory votes on executive compensation and its frequency (Proposals No. 6 and 7); approve the Eos SENOLYTIX, Inc. 2026 Equity Incentive Plan (Proposal No. 8); and allow adjournment to gather more proxies if needed (Proposal No. 9).

The filing states that Eos stockholders holding enough shares to adopt the merger agreement will be asked to do so by written consent, which is a way for a controlling stockholder to approve a transaction without waiting for a separate Eos stockholder meeting.

The exchange ratio and how much of the company Pulmatrix holders keep

The proxy describes an estimated exchange ratio of approximately 8.55 shares of Pulmatrix common stock for each share of Eos capital stock, based on the two companies' capitalizations and share purchase commitments as of August 28, 2026. The final ratio is subject to adjustment, and the stated figure does not account for the proposed reverse stock split.

Pulmatrix expects to issue 54,359,630 shares of common stock to Eos stockholders and concurrent-financing investors, plus 20,885,736 shares in new warrants, options and restricted stock units — 75,245,366 shares in total.

The proxy states that Pulmatrix securityholders owned about 4.0 million shares immediately before the merger agreement was signed (roughly 3.7 million common shares plus about 0.3 million underlying options and warrants), and are expected to own approximately 6% of the combined company on a fully diluted basis excluding the CEO RSUs. Eos securityholders are expected to own the remaining 94%. For the valuation analysis, the proxy allocates ownership as 6% to Pulmatrix common holders, 3% to Palladium Capital Group, and 91% to Eos, and states an implied value of approximately $7.85 million for Pulmatrix's 6% interest, derived from a $100.0 million pre-money valuation of Eos plus $18.0 million of anticipated capital-raising proceeds and $1.0 million invested in Pulmatrix Series B Preferred Stock.

The proxy also states that immediately after the merger, SENOTHERAPEUTIX, Inc. is expected to beneficially own more than 50% of the voting power of the combined company's common stock, making Pulmatrix a "controlled company" under Nasdaq rules.

What this means

A Form DEFM14A is a definitive proxy statement: the final version of the document a public company must send stockholders before they vote on matters that require their approval. "Definitive" distinguishes it from the preliminary proxy filed earlier; once a proxy is definitive, the company can begin soliciting votes. The special meeting on October 16, 2026 is where Pulmatrix stockholders cast those votes.

The transaction is a reverse merger in economic terms, even though the filing calls Eos the surviving corporation in the legal merger. Pulmatrix is the public shell doing the buying, but Eos's owners end up with about 94% of the combined company. This is why the proxy is also a prospectus for 75,245,366 shares of Pulmatrix common stock: those are the shares being created to pay Eos's owners, and they must be registered with the SEC before they can be issued. Pulmatrix's existing shares stay outstanding, and its existing warrants and options survive in accordance with the merger agreement.

Because the new shares exceed 20% of Pulmatrix's pre-merger shares, Nasdaq Listing Rules 5635(a) and 5635(b) require Pulmatrix stockholders — not just management — to approve the issuance and the resulting change of control. That is the legal trigger for the vote, not merely a courtesy to shareholders.

An exchange ratio is the number of acquirer shares each target share converts into. Here, one Eos share converts into roughly 8.55 Pulmatrix shares, so if the ratio holds, Eos's existing owners receive far more shares than Pulmatrix's, which is how a small public company becomes a small slice of its own acquirer. A 6% stake is the arithmetic consequence: the estimated ownership table in the proxy is what produces that figure, along with the 3% allocated to Palladium Capital Group for M&A advisory services.

A reverse stock split (Proposal No. 2) is the opposite of the more familiar split: it reduces the number of outstanding shares and raises the price per share proportionally, without changing the value of a holder's stake. Companies often propose one after issuing large numbers of shares to regain compliance with a stock exchange's minimum bid price rule. The proxy does not state a reason for the proposed split, and this article does not infer one. If approved, the ratio would be set by Pulmatrix's board within a range agreed with Eos: one new share for every 2 to 10 old shares.

The combined company is expected to be renamed "Eos SENOLYTIX Inc." and to trade on Nasdaq under the symbol "MTXL," according to the filing; Pulmatrix has filed an initial listing application for it. That means the ticker PULM would disappear and existing holders would hold MTXL shares, assuming the merger closes and Nasdaq approves the listing. The proxy states the combined company will be a "controlled company" under Nasdaq rules because SENOTHERAPEUTIX, Inc. is expected to hold more than 50% of the voting power. Controlled-company status exempts a listed company from certain Nasdaq corporate governance requirements, such as having a majority of independent directors and independent compensation and nominating committees. The proxy states Eos does not currently intend to rely on those exemptions but could do so later.

The proxy states each board approved the merger agreement and recommends that Pulmatrix stockholders vote for the proposals. Completion of the merger is conditioned on, among other things, the required stockholder approvals and Nasdaq listing. The proxy does not state a closing date.

What the sources do not say

The proxy does not explain why the two companies chose to merge, beyond reciting that each board determined the transaction was advisable, and it does not describe either company's pipeline, products or financial condition in the excerpt provided. Pulmatrix is identified in the filing and by its SEC classification as a pharmaceutical preparations company. This article does not attribute any motive for the merger that the filing does not state.

The price decline on the filing date is a fact from the price data. Nothing in the filing or the data attributes that move to the proxy, and the filing does not discuss the market reaction to it.