Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 2

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 2
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 Results of Operations” and our audited consolidated financial statements and the related notes included elsewhere in this prospectus, before making an investment decision. Unless otherwise indicated, all references in this prospectus to “Sionna,” the “company,” “we,” “our,” “us” or similar terms refer to Sionna Therapeutics, Inc. and its wholly owned subsidiary, or either or both of them as the context may require.

Overview

We are a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis (“CF”)
patients by developing novel medicines that normalize the function of the cystic fibrosis transmembrane conductance regulator (“CFTR”) protein to deliver clinically meaningful benefit to CF patients. Our goal is to deliver differentiated
medicines for people living with CF that can restore their CFTR function to as close to normal as possible by directly stabilizing CFTR’s nucleotide-binding domain 1 (“NBD1”). Despite having long been identified as a critical
component for proper CFTR function, NBD1 has been considered “undruggable,” and none of the currently approved CF therapies directly stabilizes NBD1. Worldwide revenue for approved CFTR modulators was approximately $10 billion in 2023
and is expected to grow to $15 billion by 2029. Leveraging more than a decade of our co-founders’ research on NBD1, we are advancing a pipeline of small molecules engineered to correct the defects
caused by the F508del genetic mutation, which resides in the NBD1 domain. Approximately 90% of people with CF carry at least one copy of the F508del genetic mutation. We believe stabilizing NBD1 is central to unlocking dramatic improvements in
clinical outcomes and quality of life for CF patients. We have employed biophysical, cell-based and virtual screening campaigns and extensive use of structural biology to guide the optimization of novel small molecule NBD1 stabilizers.

We are conducting ongoing Phase 1 trials of our two highly potent NBD1 stabilizers, SION-719 and SION-451, evaluating the safety, tolerability and
pharmacokinetic (“PK”) profile of single and multiple ascending doses in healthy subjects. These trials are randomized (3:1 active:placebo), doubled-blinded, placebo-controlled and are being conducted in Australia. As of January 14,
2025, five single ascending dose (“SAD”) cohorts and three multiple ascending dose (“MAD