# EDGAR Filing Document

**Accession Number:** 0001574235
**File Stem:** 0001104659-26-046851
**Filing Date:** 2026-4
**Character Count:** 22346
**Document Hash:** 71bd3b884290fa778690d0142ef53e83
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-046851.hdr.sgml**: 20260422

**ACCESSION NUMBER**: 0001104659-26-046851

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260422

**DATE AS OF CHANGE**: 20260422

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Pulmatrix, Inc.
- **CENTRAL INDEX KEY:** 0001574235
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 461821392
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-88056
- **FILM NUMBER:** 26884125

**BUSINESS ADDRESS:**
- **STREET 1:** 945 CONCORD STREET
- **STREET 2:** SUITE 1217
- **CITY:** FRAMINGHAM
- **STATE:** MA
- **ZIP:** 01701
- **BUSINESS PHONE:** (888) 355-4440

**MAIL ADDRESS:**
- **STREET 1:** 945 CONCORD STREET
- **STREET 2:** SUITE 1217
- **CITY:** FRAMINGHAM
- **STATE:** MA
- **ZIP:** 01701

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Ruthigen, Inc.
- **DATE OF NAME CHANGE:** 20130411
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** RCM Eos PIPE HOLDINGS, LLC
- **CENTRAL INDEX KEY:** 0002127194

**ORGANIZATION NAME:**
- **EIN:** 415021434
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D

**BUSINESS ADDRESS:**
- **STREET 1:** 2710 REED ROAD
- **STREET 2:** SUITE 160
- **CITY:** HOUSTON
- **STATE:** TX
- **ZIP:** 77051
- **BUSINESS PHONE:** 3058096920

**MAIL ADDRESS:**
- **STREET 1:** 2710 REED ROAD
- **STREET 2:** SUITE 160
- **CITY:** HOUSTON
- **STATE:** TX
- **ZIP:** 77051

## Exhibit 99.3

#### Exhibit 3
**Joint Filing Agreement**

April 21, 2026

In accordance with Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned hereby agree that the Schedule 13D filed on or about the date first set forth above, and any amendments thereto, with respect to the shares of Common Stock and Series B Preferred Stock of the Issuer, is, and any further amendments thereto will be, filed on behalf of each of the undersigned.

This Agreement may be executed in counterparts, each of which shall be deemed an original, and all of which together shall constitute one and the same instrument.

**IN WITNESS WHEREOF**, the undersigned have executed this Joint Filing Agreement as of date first set forth above.

---

| | |
|:---|:---|
| **RCM EOS PIPE HOLDINGS, LLC** | **RCM EOS PIPE HOLDINGS, LLC** |
| By: Rapha Capital Management, LLC, its Manager | By: Rapha Capital Management, LLC, its Manager |
| By: | /s/ Kevin M. Slawin |
| Name: Kevin M. Slawin | Name: Kevin M. Slawin |
| Title: President | Title: President |
| **RAPHA CAPITAL MANAGEMENT, LLC** | **RAPHA CAPITAL MANAGEMENT, LLC** |
| By: | /s/ Kevin M. Slawin |
| Name: Kevin M. Slawin | Name: Kevin M. Slawin |
| Title: President | Title: President |
| /s/ Kevin M. Slawin | /s/ Kevin M. Slawin |
| Kevin M. Slawin, Individually | Kevin M. Slawin, Individually |

---

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

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**Pulmatrix, Inc.**

*(Name of Issuer)*

**Common Stock, par value $0.0001 per share**

*(Title of Class of Securities)*

**—**

*(CUSIP Number)*

**Kevin M. Slawin**<br>2710 Reed Road, Suite 160<br>Houston TX 77051<br>3058096920

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**04/16/2026**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**RCM Eos PIPE HOLDINGS, LLC** | Name of reporting person<br>**RCM Eos PIPE HOLDINGS, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**405358.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**405358.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**405358.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**405358.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**9.99%** | Percent of class represented by amount in Row (11)<br>**9.99%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** RCM Eos PIPE HOLDINGS, LLC, a Delaware limited liability company owns all of the issued and outstanding shares of Series B Convertible Preferred Stock of Pulmatrix, Inc. (the "Issuer"). The Series B Convertible Preferred Stock is convertible into shares of Common Stock, par value $0.0001 per share, of the Issuer, at a ratio of approximately 454.55 shares of Common Stock for each share of Preferred Stock, subject to a 9.99% beneficial ownership blocker. RCM Eos PIPE HOLDINGS, LLC is controlled by its manager, Rapha Capital Management, LLC, a Delaware limited liability company, which is in turn managed by its manager, Kevin M. Slawin.

The above listed shares are based on 3,652,285 shares of Common Stock of the Issuer outstanding on February 23, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, and the actual number of shares may differ at the time of the conversion, subject to the 9.99% beneficial ownership blocker.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Slawin Kevin M.** | Name of reporting person<br>**Slawin Kevin M.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**X1** | Citizenship or place of organization<br>**X1** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**405358.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**405358.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**9.99%** | Percent of class represented by amount in Row (11)<br>**9.99%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** RCM Eos PIPE HOLDINGS, LLC, a Delaware limited liability company owns all of the issued and outstanding shares of Series B Convertible Preferred Stock of the Issuer. The Series B Convertible Preferred Stock is convertible into shares of Common Stock, par value $0.0001 per share, of the Issuer, at a ratio of approximately 454.55 shares of Common Stock for each share of Preferred Stock, subject to a 9.99% beneficial ownership blocker. RCM Eos PIPE HOLDINGS, LLC is controlled by its manager, Rapha Capital Management, LLC, a Delaware limited liability company, which is in turn managed by its manager, Kevin M. Slawin.

The above listed shares are based on 3,652,285 shares of Common Stock of the Issuer outstanding on February 23, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, and the actual number of shares may differ at the time of the conversion, subject to the 9.99% beneficial ownership blocker.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Rapha Capital Management, LLC** | Name of reporting person<br>**Rapha Capital Management, LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**405358.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**405358.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | Aggregate amount beneficially owned by each reporting person<br>**405358.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**9.99%** | Percent of class represented by amount in Row (11)<br>**9.99%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** RCM Eos PIPE HOLDINGS, LLC, a Delaware limited liability company owns all of the issued and outstanding shares of Series B Convertible Preferred Stock of the Issuer. The Series B Convertible Preferred Stock is convertible into shares of Common Stock, par value $0.0001 per share, of the Issuer, at a ratio of approximately 454.55 shares of Common Stock for each share of Preferred Stock, subject to a 9.99% beneficial ownership blocker. RCM Eos PIPE HOLDINGS, LLC is controlled by its manager, Rapha Capital Management, LLC, a Delaware limited liability company, which is in turn managed by its manager, Kevin M. Slawin.

The above listed shares are based on 3,652,285 shares of Common Stock of the Issuer outstanding on February 23, 2026, as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, and the actual number of shares may differ at the time of the conversion, subject to the 9.99% beneficial ownership blocker.

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Stock, par value $0.0001 per share

**(b) Name of Issuer:**
Pulmatrix, Inc.

**(c) Address of Issuer's Principal Executive Offices:**
945 CONCORD STREET, SUITE 1217, FRAMINGHAM, MA, 01701

**Item 4. Purpose of Transaction**

RCM Eos acquired the securities of Pulmatrix, Inc. (the "Issuer") pursuant to that certain Securities Purchase Agreement, dated March 26, 2026 (the "Purchase Agreement"), which closed on April 16, 2026, pursuant to which RCM Eos purchased the Securities, which are convertible into shares of the Issuer's common stock, par value $0.0001 per share (the "Common Stock") at a ratio of approximately 454.55 shares of Common Stock for each share of Preferred Stock, subject to a 9.99% beneficial ownership blocker, in each case subject to the terms and conditions set forth in the Purchase Agreement and the related Certificate of Designation of the Issuer.

RCM Eos made the investment to provide the Issuer with interim financing prior to the consummation of the transactions contemplated by that certain Agreement and Plan of Merger and Reorganization, dated March 26, 2026 (the "Merger Agreement"), by and among the Issuer, PUOS Merger Sub, Inc. and Eos SENOLYTIX, Inc., a Delaware corporation ("Eos"), pursuant to which PUOS Merger Sub, Inc. will merge with and into Eos with Eos surviving the merger as a wholly-owned subsidiary of the Issuer (the "Merger"). In connection with the Purchase Agreement, RCM Eos entered into a Voting Agreement with the Issuer, pursuant to which RCM Eos agreed, subject to the terms thereof, to vote the Preferred Stock and any shares of Common Stock issuable upon conversion thereof in favor of, among other things, approval of the Merger Agreement and the Transactions contemplated thereby (including the Merger).

RCM Eos, its manager, Rapha, and Rapha's manager, Slawin, may each be deemed an affiliate of Eos (by virtue of being under indirect control by Slawin, who is also a director and the Chief Executive Officer of Eos and an indirect equityholder of Eos). The Reporting Persons understand that under the Exchange Ratio formula set forth in the Merger Agreement, upon the closing of the Merger, on a pro forma basis and based upon the number of shares of the Issuer's Common Stock expected to be issued in the Merger, the pre-Merger Eos stockholders, including investors participating in the financings and holders of shares issued in payment of placement agent and M&A advisory fees collectively will own approximately 94% of the combined company and the Issuer stockholders will own approximately 6% of the combined company on a fully-diluted basis (excluding any shares reserved for future grants under the Issuer's equity incentive plans). Eos disclaims beneficial ownership of the Securities described herein. Upon the closing of the transactions contemplated by the Merger Agreement, it is anticipated that Eos will be replacing the board of directors of the Issuer and that the Issuer will engage in the business of Eos.

Except as described above (including with respect to the Merger Agreement), each of RCM Eos, Rapha, and Slawin does not currently have any plans or proposals that relate to or would result in any of the maters enumerated in (a) through (j) of Item 4 of Schedule 13D, although each Reporting Person reserves the right, subject to applicable law and the terms of the transaction documents, to review its investment in the Issuer and to acquire additional securities of the Issuer or dispose of some or all of the securities of the Issuer it beneficially owns, from time to time, depending on market conditions and other factors.

**Item 5. Interest in Securities of the Issuer**

**(a)**
1,000 shares of Series B Convertible Preferred Stock. The Series B Convertible Preferred Stock is convertible into shares of Common Stock, par value $0.0001 per share, of the Issuer at a ratio of approximately 454.55 shares of Common Stock for each share of Series B Preferred Stock, subject to a 9.99% beneficial ownership blocker. Based on 3,652,285 shares of Common Stock the Issuer outstanding on February 23, 2026,  as reported in the Issuer's Annual Report on Form 10-K for the year ended December 31, 2025, the 1,000 shares of Series B Convertible Preferred Stock are convertible into 405,358 shares of Common Stock (which such number shall be adjusted based on the total shares outstanding as of the time of the conversion), and amounts to 9.99% of the outstanding Common Stock after giving effect to the conversion.

**(b)**
RCM Eos has sole dispositive power over the aforementioned Securities. Rapha and Slawin may be deemed to share dispositive power over such Securities by virtue of the management structure of the aforementioned entities. RCM Eos has sole voting power over the Securities. Rapha and Slawin may be deemed to share voting power by virtue of the management structure described above. Each of Rapha and Slawin disclaims beneficial ownership of Securities held by RCM Eos, except to the extent of any pecuniary interest, or to the extent it actually exercises voting or dispositive power. The Issuer holds an irrevocable proxy to vote such Securities under certain circumstances pursuant to the Voting Agreement described in Item 6.

**(c)**
During the past sixty (60) days, RCM Eos acquired shares of the Issuer's Series B Convertible Preferred Stock in a private placement pursuant to the Purchase Agreement. This acquisition closed on April 16, 2026 for an aggregate purchase price of $1,000,000. Except as described above, RCM Eos has not effected any transactions in shares of Common Stock during the past sixty (60) days.

**Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.**

The following is a summary of the material contracts, arrangements, understandings or relationships between the Reporting Person (and persons named in response to Item 2) and any other person with respect to any securities of the Issuer.

Securities Purchase Agreement. On March 26, 2026, the Issuer and RCM Eos entered into the Purchase Agreement, which closed on April 16, 2026, pursuant to which RCM Eos purchased shares of the Issuer's Preferred Stock for an aggregate purchase price of $1,000,000. Under the Purchase Agreement, prior to the consummation of the Merger (as defined below), the Issuer is permitted to use up to $250,000 of the net proceeds for working capital and general corporate purposes, with the use of the remaining proceeds subject to certain restrictions set forth therein.

Certificate of Designation. In connection with the Purchase Agreement, the Issuer filed the Certificate of Designation with the Secretary of State of the State of Delaware. The Certificate of Designation provides, among other things, that the Preferred Stock is convertible into shares of Common Stock at a "Conversion Price" (as such term is used and defined in the Certificate of Designation) of $2.20 per share, subject to adjustment as set forth therein, and that holders of the Preferred Stock are entitled to vote together with the holders of Common Stock as a single class on an as-converted basis, subject to a beneficial ownership limitation. The Certificate of Designation also provides for cumulative dividends at 8% per annum, payable in shares of Common Stock upon conversion dates.

Voting Agreement. Concurrently with the execution of the Purchase Agreement, RCM Eos entered into a Voting Agreement, dated March 26, 2026 (the "Voting Agreement") with the Issuer, pursuant to which RCM Eos agreed, during the term thereof, to vote (or cause to be voted) the shares of Preferred Stock and any shares of Common Stock issuable upon conversion thereof in favor of matters that the Issuer's board of directors has recommended stockholders vote in favor of, including matters related to the approval of the Merger Agreement and the transactions contemplated thereby. The failure by RCM Eos to vote in accordance with the terms of the Voting Agreement grants the Issuer an irrevocable proxy to vote the shares for the purposes described in the Voting Agreement. The Voting Agreement also restricts transfers of the subject shares until the Expiration Time (as defined therein), subject to certain permitted transfers.

Merger Agreement. On March 26, 2026, the Issuer, PUOS Merger Sub, Inc., and Eos SENOLYTIX, Inc. ("Eos") entered into an Agreement and Plan of Merger and Reorganization (the "Merger Agreement"), pursuant to which, among other things, PUOS Merger Sub, Inc. will merge with and into Eos, with Eos surviving the merger as a wholly owned subsidiary of the Issuer (the "Merger"). Upon consummation of the Merger, the existing equityholders of Eos are expected to become the majority holders of the Issuer.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** RCM Eos PIPE HOLDINGS, LLC

**Signature:** By: Rapha Capital Management, LLC, its Manager, By: /s/ Kevin M. Slawin

**Name/Title:** Kevin M. Slawin/President

**Date:** 04/22/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Slawin Kevin M.

**Signature:** /s/ Kevin M. Slawin

**Name/Title:** Kevin M. Slawin

**Date:** 04/22/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Rapha Capital Management, LLC

**Signature:** /s/ Kevin M. Slawin

**Name/Title:** Kevin M. Slawin/President

**Date:** 04/22/2026