Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 13

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 13
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 notes and “ Management’s Discussion and Analysis of Financial Condition and Results of Operations” for prior periods in this prospectus. Summary of Material Risks Associated With Our Business Our business is subject to a number of risks of which you should be aware before making an investment decision. These risks include, but are not limited to, the following:

| • |     | We are a clinical-stage biopharmaceutical company and have incurred significant operating losses since inception and                                                                                                                       
 anticipate that we will continue to incur significant operating losses for the foreseeable future. Our net losses were $47.3 million and $40.2 million for the years ended December 31, 2023 and 2022, respectively. We had an accumulated 
 deficit of $165.2 million and $119.4 million as of September 30, 2024 and December 31, 2023, respectively. We may never achieve or maintain profitability.                                                                                 |

| • |     | Even if this offering is successful, we will need substantial additional funding. We may be unable to raise capital on                                         
 acceptable terms, if at all, and, as a result, we may be required to delay, reduce or eliminate our product development programs or commercialization efforts. |

| • |     | We are substantially dependent on the success of our NBD1 stabilizers. If we are unable to advance a lead NBD1 stabilizer                                                                                       
 product candidate into later-stage clinical development or unable to obtain regulatory approval and commercialize an NBD1 stabilizer-anchored therapy for the treatment of CF, or experience significant delays 
 in doing so, our business will be materially harmed.                                                                                                                                                            |

| • |     | We intend to develop our lead NBD1 stabilizer product candidate to be administered in combination with one of our                                                                                                
 complementary modulators or as an add-on to the current standard of care. Developing combination treatments increases complexity and risk, including risks of drug-drug interactions, unforeseen side effects or 
 failures in our clinical trials that could delay or prevent their regulatory approval or limit the commercial profile of an approved label.                                                                      |

| • |     | The regulatory approval processes of the FDA and comparable foreign authorities are lengthy, time-consuming and inherently                         
 unpredictable. If we are not able to obtain the required regulatory approval for any product candidate, our business will be substantially harmed. |

| • |     | We have not yet completed all testing of any product candidate in clinical trials. Preclinical, interim, topline and                                                                                                                                    
 preliminary results from