Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 268

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 268
---
 in exchange for cash or other awards, in each case, without stockholder
approval. No awards may be granted under the 2025 Plan after the date that is 10 years from the effective date of the 2025 Plan. No awards under the 2025 Plan have been made prior to the date of this prospectus.

2025 Employee Stock Purchase Plan

Our 2025
Employee Stock Purchase Plan (the “ESPP”) was approved by our board of directors on December 12, 2024, adopted by our stockholders on January 31, 2025, and will become effective on 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 ESPP has two components: a component intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the
Code (the “423 Component”), and a component that is not intended to qualify (the “Non-423 Component”). Except as otherwise provided, the Non-423
Component will be operated and administered in the same manner as the 423 Component, except where prohibited by law or as provided by the administrator. The following summary describes the material terms of the ESPP. This summary is not a complete
description of all provisions of the ESPP and is qualified in its entirety by reference to the ESPP, which will be filed as an exhibit to the registration statement of which this prospectus forms a part.

The ESPP initially reserves and authorizes the issuance of up to a total of 390,127 shares of our common stock to participating employees. The ESPP
provides that the number of shares reserved and available for issuance will automatically be cumulatively increased on January 1, 2026 and each January 1 thereafter through January 1, 2035, by the least of (i) 780,254 shares of
common stock, (ii) 1% of the Outstanding Shares on the immediately preceding December 31 or (iii) such number of shares of common stock as determined by the administrator of the ESPP. The number of shares reserved under the ESPP is subject
to adjustment in the event of a stock split, stock dividend or other change in our capitalization.

All employees who are customarily employed
by us or one of our designated subsidiaries for more than 20 hours per week and who have been employed for at least 30 days in advance of an offering are eligible to participate in the