Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 99

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 99
---
 common stock is substantially higher than the net tangible book value per share
of our common stock immediately after the completion of this offering. Therefore, if you purchase shares of our common stock in this offering, you will pay a price per share that substantially exceeds our pro forma as adjusted net tangible book
value per share after this offering. Based on the initial public offering price of $18.00 per share, you will experience immediate dilution of $9.65 per share, representing the difference between our pro forma as adjusted net tangible book value per
share as of September 30, 2024 and the initial public offering price. For a further description of the dilution that you will face immediately after this offering, see “Dilution.”

A significant portion of our total outstanding shares are restricted from immediate resale but may be sold into the market in the near future. This could cause the market price of our common stock to drop significantly, even if our business is doing well.

Sales of a substantial number of shares of
our common stock in the public market could occur at any time. If our stockholders sell, or the market perceives that our stockholders intend to sell, substantial amounts of our common stock in the public market, the market price of our common stock
could decline significantly and impair our ability to raise adequate capital through the sale of additional equity or equity-linked securities.

Upon the closing of this offering, we will have 42,520,700 shares of common stock outstanding (or 44,108,934 shares if the underwriters exercise their
option to purchase additional shares from us in full), based on the number of shares outstanding as of September 30, 2024 and after giving effect to the automatic conversion of our redeemable convertible preferred stock outstanding immediately prior
to this offering into 27,149,206 shares of our common stock. Of these, the shares sold in this offering will be freely tradable immediately after this offering and substantially all of the additional shares of common stock will be available for sale
in the public market beginning 180 days after the date of this prospectus following the expiration of lock-up agreements between our directors, officers, substantially all of our stockholders and the
underwriters. The foregoing agreements are subject to certain limited exceptions, and Goldman Sachs & Co. LLC and TD Securities (USA) LLC may release these stockholders from their lock-up agreements
with the underwriters at any time and without notice, which would allow for earlier sales of shares in the public market. See “