Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 30

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 30
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 modulator candidate, we must satisfy the regulatory agencies’ requirements to demonstrate the contribution of each component in the combination. As neither product candidate in this potential combination is an approved drug, the FDA and other regulatory authorities will require full demonstration of the safety of each component (alone and in combination), as well as the efficacy of the combination (and the contribution of each component). Our current and future product candidates could fail to receive regulatory approval for many reasons, including the following:

| • |     | the FDA or comparable foreign regulatory authorities may disagree as to the design or implementation of our clinical trials 
 and interpretation of data from clinical trials or preclinical studies;                                                     |

| • |     | we may be unable to demonstrate to the satisfaction of the FDA or comparable foreign regulatory authorities that a product 
 candidate is safe and effective for its proposed indication;                                                               |

| • |     | the results of clinical trials may not meet the level of statistical significance required by the FDA or comparable foreign 
 regulatory authorities for approval;                                                                                        |

| • |     | we may be unable to demonstrate that a product candidate’s clinical and other benefits outweigh its safety risks; |

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| • |     | the data collected from clinical trials of our product candidates may not be sufficient to support the submission of an NDA 
 to the FDA or other submission to obtain regulatory approval in the European Union or elsewhere;                            |

| • |     | the FDA or comparable foreign regulatory authorities may find deficiencies with or fail to approve the manufacturing  
 processes or facilities of third-party manufacturers with which we contract for clinical and commercial supplies; and |

| • |     | the approval policies or regulations of the FDA or comparable foreign regulatory authorities may significantly change in a 
 manner rendering our clinical data insufficient for approval.                                                              |

Of the large number of products in development, only a small percentage successfully complete the FDA or foreign regulatory approval processes and are commercialized. The lengthy approval and marketing authorization process as well as the unpredictability of future clinical trial results may result in our failing to obtain regulatory approval to market our product candidates, which would significantly harm our business, financial condition, results of operations and prospects. The FDA and comparable foreign authorities have substantial discretion in the approval process and determining when or whether regulatory approval will be granted for any product candidate that we develop. The U.S. Supreme Court’s July 2024 decision to overturn prior established case law giving deference to regulatory agencies’ interpretations of ambiguous statutory language has introduced uncertainty regarding the extent to which the FDA’s regulations, policies and decisions may become subject