Company: SION
Filing Date: 2025-02-03
Form Type: S-1/A
Source: 0001193125-25-018825
Chunk: 350

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-03
Form: S-1/A
Chunk 350
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 determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership change may further affect the limitation in future years.
The Company has not yet completed a change in control analysis, as defined under Section 382 and 383 of the Internal Revenue Code, through December 31, 2023, and the Company has not determined whether the future utilization of net
operating loss carryforwards may be materially limited based on past financings. In addition, the Company may complete future financings that could result in a change in control in the future which may limit the amount of tax attributes available to
offset future tax liabilities.

We account for income taxes by evaluating a probability threshold that a tax position must meet before a financial
statement benefit is recognized. The minimum threshold is a tax position that is more likely than not to be sustained upon examination by the applicable taxing authority, including resolution of any related appeals or litigation processes, based on
the technical merits of the position.

The Company didn’t have any unrecognized tax benefits as of December 31, 2023 or 2022,
respectively. The Company does not expect its unrecognized tax benefits to change significantly over the next year. Realization of the future tax benefits is dependent on the many factors, including the Company’s ability to generate taxable
income. The Company recognizes interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2023 and 2022, the Company’s balance of interest and penalties was zero.

F-27

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In a normal course of business, the Company is subject to examination by U.S. federal and states. The Company’s tax years are still open since inception. To the extent that the Company has tax attribute carryforwards, the tax year in which the attributes were generated may still be adjusted upon examination by the U.S. Internal Revenue Services or state tax authorities to the extent utilized in a future period. The Company is not currently under examination by any tax authorities. 14. Net Loss Per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the periods presented (in thousands, except share and per share amounts):

|                                                                                        |     | Year Ended December 31, 
 2023                    |           |   |     | 2022 |           |   |
|:---------------------------------------------------------------------------------------|:----|:------------------------|----------:|:--|: