Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 292

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 292
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 the affirmative vote of at least two-thirds of the outstanding voting stock which is not owned by the interested stockholder. |

Section 203 defines a business combination to include:

| • |     | any merger or consolidation involving the corporation and the interested stockholder; |

| • |     | any sale, transfer, lease, pledge or other disposition involving the interested stockholder of 10% or more of the assets of 
 the corporation;                                                                                                            |

| • |     | subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the 
 corporation to the interested stockholder;                                                                             |

| • |     | subject to exceptions, any transaction involving the corporation that has the effect of increasing the proportionate share 
 of the stock of any class or series of the corporation beneficially owned by the interested stockholder; and               |

| • |     | the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial 
 benefits provided by or through the corporation.                                                                        |

In general, Section 203 defines an interested stockholder as any entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation and any entity or person affiliated with or controlling or controlled by the entity or person. Choice of Forum Our amended and restated bylaws provide that the Court of Chancery of the State of Delaware is the sole and exclusive forum for the following claims or causes of action under the Delaware statutory or common law: (i) any derivative action or proceeding brought on our behalf, (ii) any action asserting a claim of, or a claim based on, a breach of a fiduciary duty owed by any of our current or former directors, officers or other employees or stockholders to us or our stockholders, (iii) any action asserting a claim arising pursuant to any provision of the DGCL or our fifth amended and restated certificate of incorporation or amended and restated bylaws (including the interpretation, validity or enforceability thereof) or as to which the DGCL confers jurisdiction on the Court of Chancery of the State of Delaware or (iv) any action asserting a claim governed by the internal affairs doctrine. However, Section 27 of the Exchange Act creates exclusive federal jurisdiction over all claims brought to enforce any duty or liability created by the Exchange Act or the rules and regulations 211

thereunder. Consequently, this choice of forum provision would not apply to claims or causes of action brought to enforce a duty or