Company: SION
Filing Date: 2025-02-07
Form Type: S-8
Source: 0001193125-25-022767
Chunk: 1

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: S-8
Chunk 1
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) of the Securities Act. ☐

Part I INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS Item 1. Plan Information. The documents containing the information specified in this Item 1 will be sent or given to participants as specified by Rule 428(b)(1) under the Securities Act of 1933, as amended (the “Securities Act”). In accordance with the rules and regulations of the U.S. Securities and Exchange Commission (the “Commission”) and the instructions to Form S-8,such documents are not being filed with the Commission either as part of this Registration Statement on Form S-8(this “Registration Statement”) or as prospectuses or prospectus supplements pursuant to Rule 424 under the Securities Act. Item 2. Registrant Information and Employee Plan Annual Information. The documents containing the information specified in this Item 2 will be sent or given to participants as specified by Rule 428(b)(1) under the Securities Act. In accordance with the rules and regulations of the Commission and the instructions to Form S-8,such documents are not being filed with the Commission either as part of this Registration Statement or as prospectuses or prospectus supplements pursuant to Rule 424 under the Securities Act. Part II INFORMATION REQUIRED IN THE REGISTRATION STATEMENT Item 3. Incorporation of Documents by Reference. The registrant hereby incorporates by reference into this Registration Statement the following documents filed with the Commission:

| (a) | Amendment No.                                                                                                                                             
 1 to the registrant’s Registration Statement on Form S-1 filed with the Commission on February 3, 2025                                                    
 (File No. 333-284352), which contains the registrant’s audited financial statements for the latest fiscal year for which such statements have been filed; |

| (b) | The prospectus to be filed by the registrant with the Commission pursuant to Rule                                                                        
 424(b) under the Securities Act, on or about February 7, 2025, relating to the Registration Statement on Form S-1, as amended (File No. 333-284352); and |

| (c) | The description of the registrant’s common stock contained in the registrant’s Registration Statement                                                                              
 on Form 8-A (File No. 001-42504), filed by the registrant with the Commission under Section 12(b) of                                                                               
 the Securities Exchange Act of 1934, as amended (the “Exchange Act”), on February 4, 2025,