Company: SION
Filing Date: 2025-01-17
Form Type: S-1
Source: 0001193125-25-008474
Chunk: 44

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-01-17
Form: S-1
Chunk 44
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 event or penalty described above may inhibit our ability to commercialize any product candidates we develop and adversely affect our business, financial condition, results of operations and prospects. If we experience delays or difficulties in the enrollment and/or retention of patients in clinical trials, our clinical development activities could be delayed or otherwise adversely affected, and our receipt of necessary regulatory approvals could be delayed or prevented. Successful and timely completion of clinical trials will require that we identify and enroll a sufficient number of patients. Patient enrollment, a significant factor in the timing of clinical trials, is 32

affected by many factors, including the size and nature of the patient population and competition for patients with other trials. Trials may be subject to delays as a result of patient enrollment taking longer than anticipated or patient withdrawal. We may not be able to initiate or continue clinical trials for our product candidates if we are unable to locate and enroll a sufficient number of eligible patients to participate in these trials as required by the FDA or comparable foreign regulatory authorities, or if a large number of patients withdraw. We cannot predict how successful we will be at enrolling subjects in future clinical trials. We may conduct clinical trials that would require patients to discontinue standard of care therapy, and we may experience challenges finding, enrolling and retaining CF patients in our planned clinical trials who are willing to discontinue their current treatment regimens to participate in our trials. For example, AbbVie previously terminated part of a Phase 2 trial that was intended to evaluate multiple doses of navocaftor in combination with a fixed dose of galicaftor because this part was deemed not enrollable due to, among other reasons, the increasing availability of Trikafta. Subject enrollment is affected by other factors including:

| • |     | the patient eligibility criteria as defined in the applicable protocol; |

| • |     | the size of the patient population required for analysis of the trial’s primary endpoints and the process for 
 identifying patients;                                                                                         |

| • |     | the actual and perceived risks and benefits of the product candidate in the trial; |

| • |     | the design of the trial; |

| • |     | our ability to recruit clinical trial investigators with the appropriate competencies and experience; |

| • |     | competing clinical trials and clinicians’ and patients’ perceptions as to the potential advantages and risks of                                                                                                                                           
 the product candidate being studied in relation to other available therapies, including the current standard of care and any new drugs that may be approved for CF, which may vary across the jurisdictions where