Company: RNAC
Filing Date: 2025-05-08
Form Type: S-8
Source: 0001453687-25-000087
Chunk: 0

Company: Cartesian Therapeutics, Inc.
Filing Date: 2025-05-08
Form: S-8
Chunk 0
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<div align='center'>As filed with the Securities and Exchange Commission on May 8, 2025</div>

#### Registration No. 333-_____

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### FORM S-8

### REGISTRATION STATEMENT

#### UNDER

#### THE SECURITIES ACT OF 1933

#### CARTESIAN THERAPEUTICS, INC.
<div align='center'>(Exact name of registrant as specified in its charter)</div>

| Delaware                                 |     |         26-1622110 |
| (State or other jurisdiction             
 of incorporation or organization)        |     |   -I.R.S. Employer 
 Identification No. |
| 7495 New Horizon Way                     
 Frederick, Maryland                      |     |              21703 |
| (Address of principal executive offices) |     |          -Zip code |

<div align='center'>(301) 348-8698

(Telephone number, including area code, of registrant's principal executive offices)

Cartesian Therapeutics, Inc. Amended and Restated 2016 Incentive Award Plan

Cartesian Therapeutics, Inc. Amended and Restated 2018 Employment Inducement Incentive Award Plan

(Full title of the plan)</div>

#### Carsten Brunn, Ph.D.

#### President and Chief Executive Officer

#### Cartesian Therapeutics, Inc.

#### 7495 New Horizon Way

#### Frederick, Maryland 21703
<div align='center'>(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copy to:</div>

#### Brian K. Rosenzweig

#### Sarah C. Griffiths

#### Covington & Burling LLP

#### One International Place, Suite 1020

#### Boston, Massachusetts 02110
<div align='center'>(617) 603-8805</div>

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 under the Exchange Act.

| Large accelerated filer | ☐ |     | Accelerated filer         | ☐ |
| Non-ac