Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 11

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 11
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 been prepared by, and is the responsibility of, our management. Our independent registered public accounting firm, Deloitte & Touche LLP, has not audited, reviewed, compiled or performed any procedures, and does not express an opinion or any other form of assurance, with respect to any of such data. This information should be read in conjunction with our consolidated financial statements and the related 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