Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 275

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 275
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 Iancovici, Fleming, Resnick and Thompson did not hold any outstanding options 
 or any unvested stock awards.                                                                                      |

| (6) | As of December 31, 2024, Ms. Stelzer held outstanding options to purchase an aggregate of 44,480 shares of our                                    
 common stock, and did not hold any other unvested stock awards. Ms. Stelzer was appointed to the board of directors, effective November 12, 2024. |

195

Effective January 6, 2025, Marcella Ruddy and Joanne Viney both joined our board of directors.

Director Engagement Letters

We have entered into
certain engagement letters with Paul Clancy, Laurie Stelzer, Marcella Ruddy and Joanne Viney. These engagement letters will be terminated in connection with this offering and director compensation shall be governed by the non-employee director
compensation policy, as further detailed below.

Paul Clancy, M.B.A.

In March 2022, we entered into a board of directors agreement with Paul Clancy (the “Clancy Agreement”) pursuant to which Mr. Clancy serves as
the independent chairman of our board of directors, effective as of June 6, 2022. Under the Clancy Agreement, Mr. Clancy was entitled to receive an initial equity grant consisting of an option to purchase 119,772 shares of common stock,
which vests over a four-year period in 16 equal quarterly installments following June 6, 2022, subject to Mr. Clancy’s continued service with us through each applicable vesting date. In addition, under the Clancy Agreement, Mr. Clancy
is entitled to an annual cash retainer of $50,000, payable quarterly, as well as reimbursement for reasonable travel expenses incurred by Mr. Clancy for his attendance at meetings of our board of directors.

In March 2024, following the Series C Financing, our board of directors granted Mr. Clancy a non-qualified
stock option to purchase 65,713 shares of common stock, which vests in 48 equal monthly installments over a period of four years following March 4, 2024, subject to Mr. Clancy’s continued service with us through each applicable vesting
date.

Laurie Stelzer

On November 12,
2024, we entered into a board of directors agreement with Laurie Stelzer (the “Stelzer Agreement”) pursuant to which