Company: SION
Filing Date: 2025-01-17
Form Type: CORRESP
Source: 0001193125-25-008482
Chunk: 0

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: CORRESP
Chunk 0
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| Goodwin Procter LLP 100 Northern 
 Avenue Boston, MA 02210          
 goodwinlaw.com +1 617 570 1000   |

January 17, 2025 VIA EDGAR AND FEDERAL EXPRESS United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F. Street, N.E. Washington, D.C. 20549 Attention: Tamika Sheppard, Laura Crotty, Jenn Do and Angela Connell

| Re: | Sionna Therapeutics, Inc. |

| Amendment No. 1 to Draft Registration Statement on Form 
 S-1                                                     |

| CIK No. 0002036042 |

Dear Ladies and Gentlemen: This letter is confidentially submitted on behalf of Sionna Therapeutics, Inc. (the “ Company”), in response to the comments of the staff of the Division of Corporation Finance (the “ Staff”) of the U.S. Securities and Exchange Commission (the “ Commission”) with respect to the Company’s Amendment No. 1 to Draft Registration Statement on Form S-1,confidentially submitted on November 26, 2024 (the “ Amendment No. 1”), as set forth in the Staff’s letter, dated December 10, 2024, addressed to Michael Cloonan (the “ Comment Letter”). The Company is concurrently publicly filing the Registration Statement on Form S-1(the “ Registration Statement”), which includes changes to reflect responses to the Staff’s comments and other updates. For reference purposes, the text of the Comment Letter has been reproduced herein with responses below each numbered comment. For your convenience, we have italicized the reproduced Staff comments from the Comment Letter. Unless otherwise indicated, page references in the descriptions of the Staff’s comments refer to the Amendment No. 1, and page references in the responses refer to the Registration Statement. All capitalized terms used and not otherwise defined herein shall have the meanings set forth in the Registration Statement. Amendment No. 1 Risk Factors We contract with third parties for the manufacture of our product candidates for clinical drug supply..., page 36

| 1. | We note your response to prior comment 13. Please revise your risk factor to disclose the single services                                                                                                                                               
 agreement with WuXi AppTec (HongKong) Limited, as WuXi is a Chinese biotechnology company of concern named in the BIOSECURE Act, which could impact the availability of U.S. government contracts, grants, and loans. Please also revise your statement