Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 125

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 125
---
 2024. Our pro forma net tangible book value as of September 30, 2024 was $179.9 million, or $5.63 per share. Pro forma net tangible book value per share represents the amount of our total tangible assets (net of deferred offering costs) less our total liabilities, divided by the number of shares of our common stock outstanding as of September 30, 2024, after giving effect to the automatic conversion of all outstanding shares of preferred stock into 27,149,206 shares of common stock immediately prior to the completion of this offering. After giving further effect to the sale of 10,588,233 shares of common stock that we are offering at the initial public offering price of $18.00 per share, and after deducting underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value as of September 30, 2024 would have been $354.9 million, or $8.35 per share. This amount represents an immediate increase in pro forma net tangible book value of $2.72 per share to our existing stockholders and an immediate dilution in pro forma net tangible book value of $9.65 per share to new investors purchasing shares of common stock in this offering. Dilution per share to new investors is determined by subtracting pro forma as adjusted net tangible book value per share after this offering from the initial public offering price per share paid by new investors. The following table illustrates this dilution (without giving effect to any exercise by the underwriters of their option to purchase additional shares):

| Initial public offering price per share                                                                  
 Historical net tangible book deficit per share as of September 30, 2024                                  
 Pro forma increase in net tangible book value per share as of September 30, 2024 attributable to the pro 
 forma adjustment described above                                                                         |     |     | (31.46 
  37.09 | ) |     |   | 18.00 |
|:---------------------------------------------------------------------------------------------------------|:----|:----|-------:|:--|:----|:--|------:|
| Pro forma net tangible book value per share as of September 30, 2024                                     |     |     |   5.63 |   |     |   |       |
| Increase in pro forma net tangible book value per share attributable to new investors participating in   
 this offering                                                                                            |     |     |   2.72 |   |     |   |