Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 274

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 274
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ici, M.D.(5)        |     |                |      — |     |               |       — |     |           |       — |
| H. Edward Fleming, Jr., M.D.(5)  |     |                |      — |     |               |       — |     |           |       — |
| Joshua Resnick, M.D.(5)          |     |                |      — |     |               |       — |     |           |       — |
| Laurie Stelzer(6)                |     |                |  5,217 |     |               | 333,784 |     |           | 339,001 |
| Peter A. Thompson, M.D.(5) . . . |     |                |      — |     |               |       — |     |           |       — |

| (1) | The amount reported represents the fees each director received for their services to our board of directors during the 
 fiscal year ended December 31, 2024.                                                                                   |

| (2) | The amounts reported represent the aggregate grant date fair value of stock option awards granted to Mr. Clancy and                                                                                                                                  
 Ms. Stelzer during fiscal year 2024, computed in accordance with FASB ASC Topic 718. A discussion of the assumptions used in determining grant date fair value may be found in Note 12 to our financial statements, included elsewhere in this       
 prospectus. Such grant date fair values do not take into account any estimated forfeitures related to service-based vesting. The amounts reported in this column reflect the accounting cost for the stock option award and do not correspond to the 
 actual economic value that may be received by Mr. Clancy and Ms. Stelzer upon the vesting of the awards or any sale of the underlying securities.                                                                                                    |

| (3) | As of December 31, 2024, Mr. Clancy held outstanding options to purchase an aggregate of 185,485 shares of our 
 common stock, and did not hold any other unvested stock awards.                                                |

| (4) | As of December 31, 2024, Mr. Rosenberg did not hold any outstanding options to purchase shares of our common                     
 stock, and did not hold any other unvested stock awards. Mr. Rosenberg resigned from the board of directors as of June 13, 2024. |

| (5) | As of December 31, 2024, Drs. Booth,