Company: SION
Filing Date: 2025-01-24
Form Type: CORRESP
Source: 0001193125-25-012256
Chunk: 1

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-24
Form: CORRESP
Chunk 1
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 letter to the Office of Freedom of Information and Privacy Act Operations. FOIA CONFIDENTIAL TREATMENT REQUESTED BY SIONNA THERAPEUTICS, INC.

Division of Corporation Finance Office of Life Sciences U.S. Securities and Exchange Commission January 24, 2025 Page 2 We confirm on behalf of the Company that, prior to circulating copies of the preliminary prospectus in connection with the offering, the Company will file a pre-effectiveamendment to the Registration Statement that will include all information other than information that may be excluded in reliance upon Rule 430A of Regulation C, and the final price range to be included in such amendment which will comply with the Staff’s interpretation regarding the parameters of a bona fideprice range. Prior to the effectiveness of the Registration Statement, the Company intends to implement a reverse stock split of its common stock, par value $0.001 per share (“ Common Stock” and such reverse stock split, the “ Stock Split”). The Company expects to reflect the Stock Split in a pre-effectiveamendment to the Registration Statement that includes the actual price range. For purposes of this letter, we have presented all dollar and per share amounts without giving effect to the Stock Split to be consistent with the current presentation in the Registration Statement. The Company respectfully requests that the bracketed information contained in this letter be treated as confidential information pursuant to Rule 83 promulgated by the Commission, 17 C.F.R. §200.8, and that the Commission provide timely notice to Michael Cloonan before it permits any disclosure of the bracketed information in this letter. For the convenience of the Staff, we have recited the prior comment from the Staff in the Comment Letter in italicized type and have followed the comment with the Company’s response.

| 16. | Once you have an estimated offering price range, please explain to us how you determined the fair value of                                                                                                           
 the common stock underlying your equity issuances and the reasons for any differences between the recent valuations of your common stock leading up to the initial public offering and the estimated offering price. |

The Company respectfully submits the below additional information to assist the Staff in its review of the Company’s position with respect to its determination of the fair value of the Common Stock, underlying its outstanding equity awards and the reasons for the differences between the recent valuations of the Common Stock and the estimated offering price for its initial public offering (“ IPO”). Preliminary IPO Price Range The Company advises the Staff that it estimates a preliminary price range of approximately $[ ***