Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 252

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 252
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 in his Severance and CIC Agreement (as
defined below) and/or the New Severance and CIC Plan (as defined below), as applicable. The restricted stock grant is further detailed in the “Outstanding Equity Awards at Fiscal 2024 Year-End” section below. Mr. Cloonan is also eligible to participate in our employee benefit plans, subject to the terms of such plans, and is entitled to severance benefits pursuant to his
Severance and CIC Agreement (as defined below) and/or the New Severance and CIC Plan (as defined below), as applicable.

In addition to
Mr. Cloonan’s severance entitlements under his Severance and CIC Agreement and/or the New Severance and CIC Plan, as applicable, each as described below, under the Cloonan Offer Letter, in the event Mr. Cloonan’s employment
ceases due to his death or disability (as defined in his Severance and CIC Agreement), he will be entitled to any earned but unpaid bonus for the year ending prior to the date of such cessation and the prorated portion of his annual target bonus for
the year in which such cessation takes place.

Elena Ridloff, C.F.A.

In August 2021, we entered into an offer letter with Ms. Ridloff (the “Ridloff Offer Letter”). Under the Ridloff Offer Letter,
Ms. Ridloff is entitled to receive an annual base salary (which has subsequently been increased as described above), a signing bonus (which was paid in 2021), an annual bonus opportunity, and an initial equity grant consisting of an option to
purchase 156,046 shares of our common stock, which vested as to 25% on the first anniversary following Ms. Ridloff’s start date and vests as to the remaining 75% in 36 equal monthly installments thereafter, subject to
Ms. Ridloff’s continued service with us through each applicable vesting date; provided that, the vesting of such shares will fully accelerate upon a “sale event” (as defined in the 2020 Plan and which does not include this
offering). The stock option grant is further detailed in the “Outstanding Equity Awards at Fiscal 2024 Year-End” section below. Ms. Ridloff is also eligible to participate in our
employee benefit plans, subject to the terms of such plans, and is entitled to severance benefits pursuant to her Severance and CIC Agreement (as defined below