Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 133

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 133
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 modulator candidates and select the most
promising candidates to advance into later-stage development. Initially, we intend to evaluate the lead NBD1 stabilizer candidate in combination with the current standard of care in a
proof-of-concept

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trial. In parallel, we will determine the proprietary dual combination that we believe is optimal to advance into a Phase 2b dose-ranging trial in CF patients. We currently have exclusive rights to develop and commercialize our compounds. Since our inception in 2019, we have not generated any revenue. To date, we have funded our operations primarily with proceeds from the sale and issuance of our preferred stock. We have received aggregate net proceeds of $330.4 million from the sale and issuance of our preferred stock. Due to our significant research, development and manufacturing expenditures, we have accumulated substantial losses and negative cash flows since our inception, including net losses of $45.8 million and $35.4 million for the nine months ended September 30, 2024 and 2023, respectively, and $47.3 million and $40.2 million for the years ended December 31, 2023 and 2022, respectively. As of September 30, 2024, we had an accumulated deficit of $165.2 million. We expect our expenses and operating losses will increase substantially as we:

| • |     | continue to advance the clinical development of our current and future product candidates, including our lead NBD1 
 stabilizer product candidate, including conducting our ongoing clinical trials;                                    |

| • |     | continue to advance our research activities and seek to discover and develop additional product candidates to expand our 
 pipeline;                                                                                                                |

| • |     | pursue regulatory approvals for any current or future product candidates, including our lead NBD1 stabilizer product 
 candidate, that successfully complete clinical trials;                                                               |

| • |     | continue to utilize third parties to manufacture our product candidates; |

| • |     | continue to develop, maintain, expand, enforce, defend and protect our intellectual property portfolio (including                             
 intellectual property obtained through license agreements) and provide reimbursement of third-party expenses related to our patent portfolio; |

| • |     | attract, hire and retain additional qualified personnel; |

| • |     | add operational, financial and management information systems; |

| • |     | undertake pre-commercial activities, and                                                                                                                       
 scale-up external commercial-scale manufacturing capabilities, to commercialize any current or future product candidates which may obtain regulatory approval; |