Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 321

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 321
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, if ever, the Company will realize significant revenue from product sales.

Liquidity and Going Concern

The Company has funded its operations primarily with proceeds from the sale of convertible preferred stock and has not generated
revenue from product sales or other sources. As of December 31, 2023, the Company has raised an aggregate of $149.0 million in net proceeds through the sale of convertible preferred stock. In March 2024, the Company issued and sold
18,628,970 shares of Series C convertible preferred stock, par value $0.001 per share (“Series C Preferred Stock”), for gross proceeds of $181.9 million (the “Series C Financing”). The Company has incurred annual net
operating losses and has generated negative operating cash flows in every year since inception. As of December 31, 2023, the Company had an accumulated deficit of $119.4 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 consolidated financial statements are issued. The Company believes that its
existing cash and cash equivalents of $38.5 million as of December 31, 2023, together with the additional proceeds received from the Series C Financing of $181.9 million in March 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 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 10).

F-7

2. Summary of Significant Accounting Policies

Basis of Presentation and Consolidation

The
accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) of
the Financial Accounting Standards Board (“FASB”). The accompanying consolidated financial statements include the accounts of Sionna Therapeutics, Inc., and its wholly owned subsidiary, Sionna Therapeutics Securities Corporation. All
intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with GAAP requires management