Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 322

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 322
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 to make judgments, assumptions, and estimates that
affect the reported amounts of assets, liabilities and expenses and the related disclosure of contingent assets and liabilities as of the date of the consolidated financial statements and the reported amounts of expenses during the reporting
periods. Significant estimate and assumptions reflected within the consolidated financial statements include, but are not limited to, research and development expenses and accruals and the valuation of the Company’s common shares in connection
with the accounting for stock-based awards. The Company bases its estimates on historical experience and various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments
about the carrying values of assets and liabilities that are not readily apparent from other sources. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances and facts. Changes in estimates are recorded in the
period in which they become known. Actual results may differ from those estimates or assumptions.

Cash, Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments with original maturities of ninety days or less at the time of purchase to be cash equivalents.
Cash and cash equivalents typically include cash held in deposit accounts and money market funds.

Cash accounts with any type of restriction are
classified as restricted cash. For the years ended December 31, 2023 and 2022, the Company had restricted cash of $1.0 million held to secure a letter of credit associated with the Company’s leased corporate headquarters. The
restricted funds are maintained in a certificate of deposit account. The Company classified this amount as restricted cash in the accompanying consolidated balance sheets within non-current assets based on the
release date of the restrictions.

Marketable Securities

The Company classifies marketable securities with a remaining maturity greater than three months at the time of purchase and less than one year from the
balance sheet date as current. Marketable securities would be classified as long-term assets on the consolidated balance sheets if the maturity exceeded one year, and the Company did not intend to utilize the marketable securities to fund current
operations.

The Company classifies all of its investments as
available-for-sale securities. Accordingly, these investments are recorded at fair value. Realized gains and losses and amortization and accretion of discounts and
premiums are included in interest income, which is a component of other income. Unrealized gain and losses on available-for-sale securities are included in
“Accumulated other comprehensive loss” as a component of stockholders’ deficit until realized.

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