Company: RNAC
Filing Date: 2025-04-28
Form Type: DEF 14A
Source: 0001453687-25-000075
Chunk: 0

Company: Cartesian Therapeutics, Inc.
Filing Date: 2025-04-28
Form: DEF 14A
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 14A
<div align='center'>(Rule 14a-101)</div>

### INFORMATION REQUIRED IN PROXY STATEMENT

#### SCHEDULE 14A INFORMATION

#### Proxy Statement Pursuant to Section 14(a) of the

#### Securities Exchange Act of 1934
| Filed by the Registrantþ |     | Filed by a Party other than the Registrant        ☐ |

Check the appropriate box:

| ☐ |     | Preliminary Proxy Statement                                                     |
| ☐ |     | Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) |
| þ |     | Definitive Proxy Statement                                                      |
| ☐ |     | Definitive Additional Materials                                                 |
| ☐ |     | Soliciting Material under § 240.14a-12                                          |

#### CARTESIAN THERAPEUTICS, INC.
<div align='center'>(Name of Registrant as Specified In Its Charter)</div>

<div align='center'>(Name of Person(s) Filing Proxy Statement, if other than the Registrant )</div>

| Payment of Filing Fee (Check the appropriate box) |     |                                                                                                     |
| þ                                                 |     | No fee required.                                                                                    |
| ☐                                                 |     | Fee previously paid with preliminary materials                                                      |
| ☐                                                 |     | Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11 |

#### CARTESIAN THERAPEUTICS, INC.

#### 7495 New Horizon Way

#### Frederick, Maryland 21703
To Our Stockholders:

You are cordially invited to attend the 2025 Annual Meeting of Stockholders (the “Annual Meeting”) of Cartesian Therapeutics, Inc. (the “Company”) to be held on Friday, June 13, 2025 at 10:00 a.m., Eastern Time. We are very pleased that our Annual Meeting will be a completely virtual meeting of stockholders, which will be conducted via live webcast. You will be able to attend the Annual Meeting online and submit your questions during the meeting by visiting www.virtualshareholdermeeting.com/RNAC2025 . You will also be able to vote your shares electronically at the Annual Meeting.

The Notice of Annual Meeting of