Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 136

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 136
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 of our current or future product candidates or fail to obtain regulatory approval for any that successfully complete clinical trials, our ability to generate future revenues, and our results of operations and financial position would be adversely affected. Operating Expenses Our operating expenses consist of (i) research and development expenses and (ii) general and administrative expenses. Research and Development Expenses Research and development expenses consist primarily of costs associated with the preclinical and clinical development of our current and potential future product candidates. In particular, our research and development expenses include:

| • |     | personnel-related costs, including salaries, payroll tax, bonuses, benefits and stock-based compensation for employees 
 engaged in research and development functions;                                                                         |

| • |     | the costs to acquire in-process research and development with no alternative future 
 use acquired in an asset acquisition;                                               |

| • |     | external expenses, including expenses incurred under arrangements with third parties, such as contract research                  
 organizations (“CROs”), contract development and manufacturing organizations (“CDMOs”), consultants and our scientific advisors; |

| • |     | the cost of manufacturing our product candidates, including costs for laboratory supplies, research materials and reagents; |

| • |     | facility costs, depreciation and other expenses, which include direct and allocated expenses; and |

| • |     | the cost of obtaining and maintaining patent and trade secret protection for our product candidates. |

We recognize research and development costs in the periods in which they are incurred. Most of our research and development expenses have been related to identifying and developing our product candidates. Typically, external expenses are recognized based on an evaluation of the progress to 97

completion of specific tasks using information provided to us by our service providers as of each reporting date. Advance payments that we make for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses, which are expensed as the related goods are delivered or the services are performed, or when it is no longer expected that the goods will be delivered, or the services rendered. Significant judgments and estimates are made in determining the accrued, or prepaid expense balances at the end of any reporting period. External costs represent a significant portion of our research and development expenses, which we track on a program-by-programbasis following the nomination of a product candidate. Our internal research and development expenses consist primarily of personnel-related expenses, including stock-based compensation expenses and allocated expenses. We do not track our internal research and development expenses on a program-by-programbasis as they either relate to early-stage research expenses