Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 276

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 276
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gregator, LP beneficially owns more than 5% of our outstanding capital stock. Sionna Aggregator, LP is an                                                        
 affiliate of Enavate Sciences. H. Edward Fleming, Jr., M.D., a member of our board of directors, is an executive vice president of commercialization at Enavate Sciences. |

| (6) | Consists of 1,765,541 shares of Series C preferred stock held by The Rise Fund Sling II, L.P. Entities affiliated with                                                        
 TPG Growth beneficially owns more than 5% of our outstanding capital stock. Lucian Iancovici, M.D., a member of our board of directors, is a managing director at TPG Growth. |

| (7) | Consists of (i) 1,715,837 shares of Series C preferred stock held by Viking Global Opportunities Illiquid Investments Sub-Master LP and (ii) 845,113 shares of Series C preferred stock held by Viking Global Opportunities Drawdown (Aggregator) LP. Entities affiliated with Viking Global Opportunities beneficially own more than 5% of 
 our outstanding capital stock.                                                                                                                                                                                                                                                                                                              |

Employment Arrangements We have entered into employment agreements with certain of our named executive officers, and granted stock options to our named executive officers and certain of our directors, as more fully described in “ Executive Compensation” and “ Director Compensation.” 199

Investors’ Rights Agreement

In March 2024, we entered into a third amended and restated investors’ rights agreement (the “investors’ rights agreement”) with
certain holders of more than 5% of our outstanding capital stock.

This investors’ rights agreement provides certain holders of our preferred
stock with a participation right to purchase their pro rata share of new securities that we may propose to sell and issue, subject to certain exceptions. Such participation right will terminate upon the completion of this offering. The
investors’ rights agreement further provides certain holders of our preferred stock with certain rights, including certain registration rights with respect to the registrable securities held by them. See the section titled “Description of Capital Stock—Registration Rights” for additional information.

Voting Agreement

In March 2024, we entered into a second amended and restated voting agreement (“voting agreement”) with certain holders of more than 5% of our
outstanding capital stock.

Our voting agreement provides for drag-along rights in respect of sales by certain holders of our capital stock. The
voting agreement