Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 252

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 252
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 stock options and stock awards, treatment as set forth in the applicable award agreement, and (C) 12 months’ extension of any post-termination exercise period for options held
by the NEO prior to the New Severance and CIC Plan Effective Date. The amounts payable under (i) through (iii) shall be paid out in a lump sum within 60 days after the date of termination. As of the New Severance and CIC Plan Effective Date,
prongs (i) and (iii) for Mr. Cloonan will be superseded by the New Severance and CIC Plan.

Pursuant to each of the Severance and CIC
Agreements, any payments and benefits provided to an NEO in connection with a change in control that would otherwise not be eligible for a federal income tax deduction for us pursuant to Section 280G of the Code and subject the NEO to an excise
tax under Section 4999 of the Code shall be reduced, but only if such reduction would result in the NEO retaining a larger portion of such payments and benefits on an after-tax basis than if no reduction
was made and the excises taxes had been paid (also known as a 280G modified cutback).

Severance and Change in Control Plan

On December 12, 2024, our board of directors adopted the New Severance and CIC Plan, subject to the effectiveness of the registration statement of
which this prospectus forms a part. Employees with the job title of vice president and above at the time of termination (or, if applicable, “change in control” (as defined in the New Severance and CIC Plan and which does not include this
offering)) and who have executed a participation agreement (each, an “Eligible Employee”), will be eligible to participate in the New Severance and CIC Plan.

The New Severance and CIC Plan will provide that, at any time outside of the period commencing upon a change in control (as defined in the New Severance
and CIC Plan) and ending 12 months after such change in control (the “change in control period”), upon a (i) termination by us for any reason other than due to “cause,” death or “disability” (as such terms are
defined in the New Severance and CIC Plan) or (ii) for Eligible Employees with a C-level position and who reports directly to our chief executive officer and/or has a job title of Executive Vice President