Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 356

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 356
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 from the sale of convertible preferred stock and has not
generated revenue from product sales or other sources. As of September 30, 2024, the Company has raised an aggregate of $330.4 million in net proceeds through the sale of convertible preferred stock. The Company has incurred annual net
operating losses and has generated negative operating cash flows in every year since inception. As of September 30, 2024, the Company had an accumulated deficit of $165.2 million. The Company expects its operating losses to continue into
the foreseeable future as it continues to pursue its research and development efforts.

The Company has evaluated whether there are conditions and
events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that these condensed consolidated financial statements are issued. The Company believes
that its existing cash, cash equivalents and marketable securities of $180.9 million as of September 30, 2024, will be sufficient to allow the Company to fund operations beyond twelve months from the date that the financial statements are
available for issuance.

The Company is seeking to complete an initial public offering (“IPO”) of its common stock. Upon the completion of
a qualified public offering on specified terms, the Company’s outstanding convertible preferred stock will automatically convert into shares of common stock (see Note 9).

F-35

2. Summary of Significant Accounting Policies

The Company’s significant accounting policies are disclosed in Note 2, “Summary of Significant Accounting Policies,” in the audited
consolidated annual financial statements for the years ended December 31, 2023 and 2022 included elsewhere in this prospectus. Since the date of those annual financial statements, there have been no changes to the Company’s significant
accounting policies, except as noted below.

Unaudited Interim Financial Information

The accompanying condensed consolidated balance sheet as of September 30, 2024, and the condensed consolidated statements of operations and
comprehensive loss, statements of convertible preferred stock and stockholders’ deficit and statements of cash flows for the nine months ended September 30, 2024 and 2023 are unaudited. The condensed consolidated interim financial
statements have been prepared on the same basis as the December 31, 2023 and 2022 audited annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for the
fair presentation of the Company’s financial position as of September