Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 342

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 342
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2 are presented as follows:

|                          |     | Year Ended December 31, |  2023 |   |     |     | 2022 |   |
|:-------------------------|:----|:------------------------|------:|:--|:----|:----|-----:|:--|
| Expected term (in years) |     |                         |   6.0 |   |     |     |  6.0 |   |
| Volatility               |     |                         | 107.0 | % |     |     | 96.4 | % |
| Interest rate            |     |                         |   4.1 | % |     |     |  2.2 | % |
| Dividend yield           |     |                         |     — |   |     |     |    — |   |

F-24

Stock Option Activity The following table summarizes the Company’s stock option activity under the 2020 Plan for the year ended December 31, 2023:

|                                     |     | Number of 
 Shares    |           |     | Weighted-Average 
 Exercise Price   |      |     | Weighted-Average 
 Remaining        
 Contractual Term 
 (in years)       |     |     | Aggregate       
 Intrinsic Value 
 (in thousands)  |       |
|:------------------------------------|:----|:----------|----------:|:----|:-----------------|-----:|:----|:-----------------|----:|:----|:----------------|------:|
| Outstanding as of December 31, 2022 |     |           | 1,945,186 |     | $                | 5.19 |     |                  | 9.1 |     | $               | 1,797 |
| Granted                             |     |           |   179,636 |     |                  | 6.11 |     |                  |     |     |                 |       |
| Exercised                           |     |           |   -35,552 |     |                  | 0.87 |     |                  |     |     |                 |       |
| Cancelled or forfeited              |     |           |  -174,908 |     |                  | 5.75 |     |                  |     |     |                 |       |
| Outstanding as of December 31, 2023 |     |           | 1,914,362 |     | $                | 5.