Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 243

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 243
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 governance committee currently consists of Paul Clancy, M.B.A., chair of our nominating and corporate governance committee, Marcella Kuhlman Ruddy, M.D. and Peter A. Thompson, M.D. Our board of directors has determined that each member of the nominating and corporate governance committee is independent under the Nasdaq Listing Rules, a non-employeedirector, and free from any relationship that would interfere with the exercise of his or her independent judgment. The primary purpose of the nominating and corporate governance committee is to discharge the responsibilities of our board of directors with respect to our corporate governance functions and to identify, communicate with, evaluate and recommend candidates for our board of directors. Specific responsibilities of our nominating and corporate governance committee include:

| • |     | identifying and evaluating candidates, including the nomination of incumbent directors for reelection and nominees 
 recommended by stockholders, to serve on our board of directors;                                                   |

| • |     | considering and making recommendations to our board of directors regarding the composition and chairmanship of the 
 committees of our board of directors;                                                                              |

| • |     | instituting plans or programs for the continuing education of our board of directors and orientation of new directors; |

| • |     | developing and making recommendations to our board of directors regarding corporate governance guidelines and matters; and |

| • |     | overseeing periodic evaluations of the board of directors’ performance, including committees of the board of directors 
 and management.                                                                                                        |

Our nominating and corporate governance committee will operate under a written charter, which will be effective upon the completion of this offering, that satisfies the applicable Nasdaq Listing Rules. Code of Business Conduct and Ethics In connection with this offering, we adopted an amended and restated code of business conduct and ethics that applies to all our employees, officers and directors, to be effective upon the effectiveness of the registration statement of which this prospectus forms a part. This includes our principal executive officer, principal financial officer and principal accounting officer or controller, or persons performing similar functions. The full text of our code of business conduct and ethics will be posted on our website at www.sionnatx.com. We intend to disclose on our website any future amendments of our code of business conduct and ethics or waivers that exempt any principal executive officer, principal financial officer, principal accounting officer or controller, persons performing similar functions or our directors from provisions in the code of business conduct and ethics. Information contained on, or accessible through, our website is not a part of this prospectus, and the