Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 129

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 129
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 data) |            |     | Percentage |       |   |     | Total Consideration 
 Amount              |         |     | Percentage |       |   |     | Weighted- 
 Average   
 Price Per 
 Share     |       |
|:-------------------------------------------------|:----|:---------------------------------------------------------|-----------:|:----|:-----------|------:|:--|:----|:--------------------|--------:|:----|:-----------|------:|:--|:----|:----------|------:|
| Existing stockholders before this offering       |     |                                                          | 31,932,467 |     |            |  78.4 | % |     | $                   | 330,537 |     |            |  68.8 | % |     | $         | 10.35 |
| New investors purchasing shares in this offering |     |                                                          |  8,823,529 |     |            |  21.6 | % |     | $                   | 150,000 |     |            |  31.2 | % |     | $         | 17.00 |
| Total                                            |     |                                                          | 40,755,996 |     |            | 100.0 | % |     | $                   | 480,537 |     |            | 100.0 | % |     |           |       |

Each $1.00 increase or decrease, as applicable, in the assumed initial public offering price of $17.00 per share, which is the midpoint of the estimated offering price range set forth on the cover page of this prospectus, would increase or decrease, as applicable, the total consideration paid by new investors by $8.8 million and, in the case of an increase, would increase the percentage of total consideration paid by new investors to 32.5% and, in the case of a decrease, would decrease the percentage of total consideration paid by new investors to 29.9%, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same. Similarly, each increase or decrease, as applicable, of 1.0 million shares in the number of shares offered by us, would increase or decrease, as applicable, the total consideration paid by new investors by $17.0 million and, in 92

the case of an increase, would increase the percentage of total consideration paid by new investors to 33.6% and,