Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 347

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 347
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 Company did not issue shares of restricted common stock to founders and officers during the years ended December 31, 2023 or 2022. The outstanding restricted shares are subject to a vesting schedule that varies among the grants, and vesting may be accelerated upon a change in control, as defined in the agreements. If the holders cease to have a business relationship with the Company, the Company may repurchase any unvested shares of common stock held by these individuals at their original purchase price. The unvested shares of common stock are not considered outstanding shares and are recorded as a liability until the shares vest. A summary of the Company’s restricted stock activity during the year ended December 31, 2023 is presented below:

|                                  |     | Number of  
 Restricted 
 Shares     |          |   |     | Weighted-Average 
 Per-Share        
 Grant-Date       
 Fair Value       |      |
|:---------------------------------|:----|:-----------|---------:|:--|:----|:-----------------|-----:|
| Unvested as of December 31, 2022 |     |            |  484,531 |   |     | $                | 0.76 |
| Vested                           |     |            | (222,382 | ) |     | $                | 0.75 |
| Unvested as of December 31, 2023 |     |            |  262,149 |   |     | $                | 0.78 |

For the years ended December 31, 2023 and 2022, the liability related to the payments received for shares of unvested restricted stock was de minimis. The aggregate fair value of restricted stock awards that vested during the years ended December 31, 2023 and 2022 was $1.4 million and $2.0 million, respectively. Stock Option Valuation The assumptions used to determine the fair values of stock options granted to employees and directors during the years ended December 31, 2023 and 2022 are presented as follows:

|                          |     | Year Ended December 31, |  2023 |   |     |     | 2022 |   |
|:-------------------------|:----|:------------------------|------:|:--|:----|:----|-----:|:--|
| Expected term (in years) |     |                         |   6.0 |   |     |     |