# EDGAR Filing Document

**Accession Number:** 0001453687
**File Stem:** 0001453687-26-000030
**Filing Date:** 2026-1
**Character Count:** 7269
**Document Hash:** 30754b27cee9aea6812665da94012f7a
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001453687-26-000030.hdr.sgml**: 20260106

**ACCESSION NUMBER**: 0001453687-26-000030

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260102

**FILED AS OF DATE**: 20260106

**DATE AS OF CHANGE**: 20260106

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Singer Michael
- **CENTRAL INDEX KEY:** 0002000122

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-37798
- **FILM NUMBER:** 26511771

**MAIL ADDRESS:**
- **STREET 1:** C/O CARTESIAN THERAPEUTICS, INC.
- **STREET 2:** 704 QUINCE ORCHARD RD
- **CITY:** GAITHERSBURG
- **STATE:** MD
- **ZIP:** 20878
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Cartesian Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001453687
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 7495 NEW HORIZON WAY
- **CITY:** FREDERICK
- **STATE:** MD
- **ZIP:** 21703
- **BUSINESS PHONE:** 301-348-8698

**MAIL ADDRESS:**
- **STREET 1:** 7495 NEW HORIZON WAY
- **CITY:** FREDERICK
- **STATE:** MD
- **ZIP:** 21703

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** SELECTA BIOSCIENCES INC
- **DATE OF NAME CHANGE:** 20090109

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

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[ ] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>Singer Michael<br><sub>(Last) (First) (Middle)</sub><br>C/O CARTESIAN THERAPEUTICS, INC.<br>7495 NEW HORIZON WAY<br><sub>(Street)</sub><br>FREDERICK, MD 21703<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-01-02 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director [ ] 10% Owner<br>[ ] Officer (give title below) [ ] Other (specify below)<br>_ _ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>Cartesian Therapeutics, Inc. [ RNAC ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common  Stock | 2026-01-02 |  | A |  | 2600 | A<sup>(1)</sup> | $0 | 56133 | D |  |
| Common  Stock |  |  |  |  |  |  |  | 383796 | I | by trust<sup>(2)</sup> |
| Common  Stock |  |  |  |  |  |  |  | 56719 | I | by trust<sup>(3)</sup> |
| Common  Stock |  |  |  |  |  |  |  | 7127 | I | by trust<sup>(4)</sup> |
| Common  Stock |  |  |  |  |  |  |  | 14788 | I | by spouse<sup>(5)</sup> |
| Common  Stock |  |  |  |  |  |  |  | 96219 | I | as custodian<sup>(6)</sup> |
| Common  Stock |  |  |  |  |  |  |  | 96219 | I | as custodian<sup>(7)</sup> |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock Option (Right to Buy) | $6.76 | 2026-01-02 |  | A |  | 7800 |  | 2027-01-02 | 2036-01-01 | Common  Stock | 7800 | $0 | 7800 | D |  |

---

### Footnotes:

(1) Each Restricted Stock Unit represents a contingent right to receive one share of common stock, which will vest in full on January 2, 2027.

(2) Shares are held in a trust for the benefit of the reporting person's spouse and children. The reporting person's spouse is a trustee of the trust.

(3) Shares are held in a trust for which the reporting person is a beneficiary. The reporting person is a trustee of the trust.

(4) Shares are held in a trust for which the reporting person is a beneficiary. The reporting person's spouse is a trustee of the trust.

(5) Shares are held by the reporting person's spouse.

(6) The shares are held for LS, the child of the reporting person, through a custodial account established pursuant to the Uniform Transfer to Minors Act ("UTMA") for which the reporting person serves as custodian.

(7) The shares are held for SS, the child of the reporting person, through a custodial account established pursuant to the UTMA for which the reporting person serves as custodian.

**Signature:** /s/ Matthew Bartholomae, Attorney-in-Fact for Michael Singer  
**Date:** 2026-01-06

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**