Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 42

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 42
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 the evaluation of such applications, and to shorten the FDA’s goal for taking action on a marketing application from ten months to six months
from FDA’s acceptance of the application for review. Priority review designation may be rescinded if a product no longer meets the qualifying criteria.

We may not be able to submit INDs or IND amendments to commence clinical trials on the timelines we expect, and even if we are able to, the FDA may not permit us to proceed.

We may not be able to submit INDs, including the IND for our lead NBD1 stabilizer product candidate, on the timelines we expect.
For example, we may experience manufacturing delays or other delays with IND-enabling studies. Moreover, we cannot be sure that submission of an IND will result in the FDA allowing clinical trials to begin, or
that, issues will not arise that suspend or terminate clinical trials. Additionally, even if such regulatory authorities agree with the design and implementation of the clinical trials set forth in an IND, we cannot guarantee that such regulatory
authorities will not change their requirements in the future. These considerations also apply to new clinical trials we may submit as amendments to existing INDs.

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Any product candidate for which we obtain marketing approval could be subject to restrictions or withdrawal from the market, and we may be subject to substantial penalties if we fail to comply with regulatory requirements or if we experience unanticipated problems with our products, when and if any of them are approved. As part of its decision to approve or grant marketing authorization for one or more of our product candidates, the FDA or other regulatory agencies may require us to perform certain post-marketing activities, such as completion of ongoing or planned studies, initiation of new studies or post-marketing clinical trials (including to assess safety risks), or additional analyses of existing data. Typically, we are required to provide annual updates on the progress of such required activities and to complete the activities by the assigned completion dates. Later discovery of previously unknown problems with our product candidates, including AEs of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, or failure to comply with regulatory requirements, may result in, among other things:

| • |     | restrictions on the marketing or manufacturing of such products, withdrawal of the product from the market or voluntary or 
 mandatory product recalls;                                                                                                 |

| • |     | restrictions on or revisions to the labeling or marketing of a medicine; |

| • |     | restrictions on the distribution or use of a medicine, including under a risk evaluation and mitigation