Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 322

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 322
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 to transfer a liability (an exit price) in the principal or most advantageous market for the
asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial
assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level1—Quoted market prices in active markets for identical assets or
liabilities.

Level2—Inputs other than Level 1 inputs that are either directly or
indirectly observable, such as quoted market prices, interest rates and yield curves.

Level3—Unobservable inputs for the asset or liability (i.e., supported by little or no market
activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of the fair
value requires more judgement. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on
the lowest level of input that is significant to the fair value measurement.

F-9

Property and Equipment, net Property and equipment is stated at cost net of accumulated depreciation. Costs of major additions and betterments are capitalized. Maintenance and repairs to an asset that do not improve or extend its life are expensed in the period incurred. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows:

|                        |     |               Estimated Useful Life (in years) |
| Lab equipment          |     |                                              5 |
| Furniture & fixtures   |     |                                              5 |
| Hardware & software    |     |                                              3 |
| Leasehold improvements |     | Shorter of useful life or remaining lease term |

Construction-in-progressis stated at cost, which includes direct costs attributable to the construction of the related asset. Depreciation expense is not recorded on construction-in-progressuntil the relevant assets are completed and placed into service. When an item is sold or retired, the costs and related accumulated depreciation are eliminated, and the resulting gain or loss, if any, is credited or charged to the consolidated statement of