Company: SION
Filing Date: 2025-04-29
Form Type: DEF 14A
Source: 0001193125-25-101830
Chunk: 1

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-04-29
Form: DEF 14A
Chunk 1
---
 the 2028 annual meeting of stockholders and until his or her successor has been duly elected and qualified, or until his or her earlier death, resignation or removal; |

| 3. | To transact any other business properly brought before the Annual Meeting or any adjournment or postponement of the Annual Meeting. |

You can find more information on each of the matters to be voted on at the Annual Meeting, including information regarding the nominees for election to our board of directors, in the accompanying proxy statement. The board of directors recommends a vote “FOR” the election of each of the three nominees for class I directors and “FOR” the ratification of the appointment of our independent registered public accounting firm for the fiscal year ending December 31, 2025. This year, we are following the Securities and Exchange Commission’s “Notice and Access” rule that allows companies to furnish their proxy materials by posting them on the Internet. As a result, we are mailing to our stockholders a Notice of Internet Availability of Proxy Materials (the “Notice”) instead of a paper copy of the accompanying proxy statement and our Annual Report on Form 10-Kfor the fiscal year ended December 31, 2024 (the “2024 Annual Report”). We are mailing the Notice on or about April 29, 2025, and it contains instructions on how to access both the 2024 Annual Report and accompanying proxy statement (the “Proxy Materials”) over the Internet. This method provides our stockholders with expedited access to Proxy Materials and not only lowers the cost of printing and distribution but also reduces the environmental impact of the Annual Meeting. If you would like to receive a print version of the Proxy Materials, free of charge, please follow the instructions on the Notice. Please visit www.virtualshareholdermeeting.com/SION2025to attend the Annual Meeting virtually via the Internet. You will not be able to attend the Annual Meeting in person. Whether or not you expect to attend the Annual Meeting online, we encourage you to read the accompanying proxy statement and vote your shares as promptly as possible to ensure your representation and

the presence of a quorum at the Annual Meeting on the Internet as described in the instructions included in the Notice by voting online at www.proxyvote.com. If you requested and received a paper copy of the Proxy Materials, you can vote by signing, dating and returning the enclosed proxy card, calling 1-800-690-6903and following the recorded instructions, or online at www.proxyvote.com. If you vote