Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 31

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 31
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 are promising, such data may not be sufficient to support approval by the FDA and other regulatory authorities. The FDA may also require us to conduct additional preclinical studies or clinical trials for our product candidates either prior to or after approval, or it may object to elements of our clinical development programs. For example, for our NBD1 stabilizer product candidates, which are being developed as a potential add-onto standard of care, we would be required to satisfy the regulatory agencies’ requirements to demonstrate clinically meaningful improvements in efficacy with the NBD1 stabilizer co-administeredwith the standard of care, as compared to the standard of care alone. It may be harder to show a clinically meaningful improvement in efficacy in this clinical trial where all participants are receiving the standard of care. Additional safety, efficacy and/or drug-drug interaction data may be required relative to what would be required for a single-agent study. Furthermore, because we intend to develop our NBD1 stabilizer product candidate in combination with our complementary 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