Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 122

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 122
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 stock in this offering at the initial public offering price of $18.00 per share, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. |

The pro forma as adjusted information below is illustrative only, and our capitalization following the completion of this offering will be adjusted based on the actual initial public offering price and other terms of this offering determined at pricing. You should read this information in conjunction with our audited consolidated financial statements and the related notes included elsewhere in this prospectus and in “ Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

|                                                                                                                                                                                                                                                   |     | As of September 30, 2024 |          |   |     |           |          |   |     |             |          |   |
|:--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:----|:-------------------------|---------:|:--|:----|:----------|---------:|:--|:----|:------------|---------:|:--|
| (in thousands, except share and per share data)                                                                                                                                                                                                   |     | Actual                   |          |   |     | Pro Forma |          |   |     | Pro Forma   
 As Adjusted |          |   |
| Cash, cash equivalents and investments in marketable securities                                                                                                                                                                                   |     | $                        |  180,874 |   |     | $         |  180,874 |   |     | $           |  354,990 |   |
| Convertible preferred stock (Series Seed, A, B and C), par value $0.001 per share; 39,667,715 shares                                                                                                                                              
 authorized, issued and outstanding, actual; no shares authorized, issued or outstanding, pro forma and pro forma as adjusted                                                                                                                      |     | $                        |  330,368 |   |     | $         |        — |   |     | $           |        — |   |
| Stockholders’ (deficit) equity:                                                                                                                                                                                                                   |     |                          |          |   |     |           |          |   |     |             |          |   |
| Preferred stock, par value $0.001 per share; no shares authorized, issued or outstanding, actual; and                                                                                                                                             
 10,000,000 shares authorized and no shares issued or outstanding, pro forma and pro forma as adjusted                                                                                                                                             |     |                          |        — |   |     |           |        — |   |     |             |        — |   |
| Common stock