Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 0

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 0
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As filed with the Securities and Exchange Commission on February 3, 2025. Registration No. 333-284352 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 Amendment No. 1 to FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 Sionna Therapeutics, Inc. (Exact name of registrant as specified in its charter)

| Delaware                        |     |                         2834 |     | 84-2801521            |
| (State or other jurisdiction of 
 incorporation or organization)  |     | -Primary Standard Industrial 
   Classification Code Number |     | -I.R.S. Employer      
 Identification Number |

21 Hickory Drive, Suite 500 Waltham, MA 02451 (617) 819-2020 (Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices) Michael Cloonan President and Chief Executive Officer Sionna Therapeutics, Inc. 21 Hickory Drive, Suite 500 Waltham, MA 02451 (617) 819-2020 (Name, address, including zip code, and telephone number, including area code, of agent for service) Copies to:

| Gabriela Morales-Rivera                 
 William D. Collins Janet Hsueh          
 Goodwin Procter LLP 100 Northern Avenue 
 Boston, MA 02210 (617) 570-1000         |     | Jennifer Fitzpatrick                    
 Senior Vice President, General Counsel  
 21 Hickory Drive, Suite 500 Waltham, MA 
 02451 (617) 819-2020                    |     | Tara Fisher                        
 Thomas J. Danielski Ropes & Gray   
 LLP 800 Boylston Street Boston, MA 
 02199 (617) 951-7000               |

Approximate date of commencement of proposed sale to the public:As soon as practicable after this registration statement becomes effective. If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box: ☐ If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐ If this Form is a post-effective amendment filed pursuant to Rule