Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 22

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 22
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 activities and scale up external commercial-scale manufacturing capabilities; |

| • |     | ultimately establish a sales, marketing and distribution infrastructure to commercialize any product candidates for which 
 we may obtain regulatory approval;                                                                                        |

| • |     | add additional operational, financial, clinical, quality and management information systems; and |

| • |     | incur additional audit, legal, regulatory, tax and other expenses with being a public company. |

We may encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may adversely affect our business. The size of our future net losses will depend, in part, on the rate of future growth of our expenses and our ability to generate revenue. Given the numerous risks and uncertainties associated with pharmaceutical product development, it is not certain if any of our current or future product candidates will advance through late-stage development or be approved for commercial sale; therefore, we are unable to predict if or when we will generate product revenue or achieve or maintain profitability. Even if we successfully complete development and obtain the necessary regulatory approval for commercialization for any of our product candidates, we anticipate incurring significant costs associated with launching and commercializing such products. If we fail to become profitable or do not sustain profitability on a continuing basis, we may be unable to continue our operations at planned levels and be forced to reduce or cease operations. Even if this offering is successful, we will need substantial additional funding. We may be unable to raise capital on acceptable terms, if at all, and, as a result, we may be required to delay, reduce or eliminate our product development programs or commercialization efforts. Our operations have consumed substantial amounts of cash since inception. Identifying potential product candidates and conducting preclinical testing and clinical trials is a time-consuming, expensive and uncertain process that takes years to complete, and we may never generate the necessary data or results required to obtain regulatory approvals and achieve product sales. We expect to continue to 18

incur significant and increasing expenses and operating losses for the foreseeable future as we initiate and conduct clinical trials of our current and future product candidates, scale-upand manufacture our product candidates, advance our preclinical programs, seek marketing and regulatory approvals for any product candidates that successfully complete clinical trials and commercialize our products, if approved. Because the outcome of any clinical trial or preclinical study is highly uncertain, we cannot reliably estimate the actual amount of financing necessary to successfully complete the development and commercialization of any of our product candidates. We believe that the anticipated net proceeds from this offering, together with our existing