Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 264

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 264
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3,700,335 shares of common stock at
a weighted average exercise price of $5.87 per share and 75,958 shares of restricted stock were outstanding under the 2020 Plan.

189

2025 Stock Option and Incentive Plan

Our 2025 Stock Option and Incentive Plan (the “2025 Plan”) was adopted by our board of directors on December 12, 2024, adopted by our
stockholders on January 31, 2025, and will become effective upon the date immediately preceding the date on which the registration statement of which this prospectus forms a part is declared effective by the SEC. The 2025 Plan will replace the
2020 Plan, as our board of directors has determined not to make additional awards under the 2020 Plan following the closing of this offering. However, the 2020 Plan will continue to govern outstanding equity awards granted thereunder. The 2025 Plan
allows us to make equity-based and cash-based incentive awards to our employees, non-employee directors and consultants. The following summary describes the material terms of the 2025 Plan. This summary is not
a complete description of all provisions of the 2025 Plan and is qualified in its entirety by reference to the 2025 Plan, which will be filed as an exhibit to the registration statement of which this prospectus forms a part.

We have initially reserved 5,060,000 shares of our common stock for the issuance of awards under the 2025 Plan (the “Initial Limit”). The 2025
Plan provides that the number of shares reserved and available for issuance under the 2025 Plan will automatically be cumulatively increased on January 1, 2026 and each January 1 thereafter through January 1, 2035, by 4% of the sum of
(x) the number of shares of our common stock outstanding and (y) the number of shares of our common stock issuable pursuant to the exercise of any outstanding, pre-funded warrants to acquire common
stock for a nominal exercise price ((x) and (y) together, the “Outstanding Shares”) on the immediately preceding December 31 or such lesser number of shares as determined by our administrator (the “Annual Increase”).
The number of shares reserved under the 2025 Plan is subject to adjustment in the event of a stock split, stock dividend or other change in our capitalization.

The shares we issue under the 2025 Plan will be authorized but unissued