Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 150

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 150
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7.07 per share as of October 2024. The fair value of our common stock was determined by our board of directors, with input from management and considering the independent third-party valuations and various objective and subjective factors as of each grant date, including:

| • |     | the prices at which we sold preferred stock and the superior rights and preferences of the preferred stock relative to our 
 common stock at the time of each grant;                                                                                    |

| • |     | our ability to raise future financings; |

| • |     | the progress of our research and development efforts, including the status of clinical trials for our product candidates; |

| • |     | the lack of liquidity of our equity as a private company; |

| • |     | our stage of development and business strategy and the material risks related to our business and industry; |

| • |     | the achievement of enterprise milestones, including entering into collaboration and license agreements; |

| • |     | the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed 
 mergers and acquisitions of peer companies;                                                                              |

| • |     | any external market conditions affecting the biotechnology industry and trends within the biotechnology industry; |

| • |     | the likelihood of achieving a liquidity event for the holders of our preferred stock and holders of our common stock, such 
 as an initial public offering, or a sale of our company, given prevailing market conditions; and                           |

| • |     | the analysis of IPOs and the market performance of similar companies in the biopharmaceutical industry. |

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The assumptions underlying these valuations were highly complex and subjective and represented
management’s best estimates, which involved inherent uncertainties and the application of management’s judgment. As a result, if we had used significantly different assumptions or estimates, the fair value of our common stock and our
stock-based compensation expense could be materially different.

Once a public trading market for our common stock has been established in
connection with the completion of this offering, it will no longer be necessary for our board of directors to estimate the fair value of our common stock in connection with our accounting for granted stock options and other such awards we may grant,
as the fair value of our common stock will be determined based on the quoted market price of our common stock.

Recent Accounting Pronouncements

A description of recently issued accounting pronouncements that may potentially impact our financial position and results of operations is disclosed in
Note 2, “Summary of Significant Accounting Policies