Company: SION
Filing Date: 2025-02-07
Form Type: 424B4
Source: 0001193125-25-022709
Chunk: 129

Company: Sionna Therapeutics, Inc.
Filing Date: 2025-02-07
Form: 424B4
Chunk 129
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 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”). We believe stabilizing NBD1 is central to unlocking
dramatic improvements in clinical outcomes and quality of life for CF patients.

We are conducting ongoing Phase 1 trials of our two highly potent
NBD1 stabilizers—SION-719 and SION-451—evaluating the safety, tolerability and PK of single and multiple ascending doses of each product candidate in healthy subjects. These trials are randomized, doubled-blinded, placebo-controlled trials
being conducted in Australia. As of January 14, 2025, five SAD cohorts and three MAD cohorts of SION-719 have been completed, with over 60 healthy subjects dosed (randomized 3:1 active:placebo), and six SAD cohorts and three MAD cohorts of SION-451
have been completed, with over 70 healthy subjects dosed (randomized 3:1 active:placebo). Both SION-719 and SION-451 have been generally well tolerated based on interim Phase 1 clinical data as of the cutoff date of January 14, 2025. In these
trials, at both single and multiple doses, SION-719 and SION-451 exposures were achieved that have the potential, based on our preclinical CFHBE model, to provide clinically meaningful benefit if SION-719 or SION-451 were administered as part of a
dual combination or as an add-on to the standard of care (“SOC”). We plan to continue enrolling healthy subjects in the trial.

We are
also developing a portfolio of complementary CFTR modulators designed to work synergistically with our NBD1 stabilizers to improve CFTR function, as seen in preclinical models. In July 2024, we in-licensed
three clinical-stage compounds from AbbVie to expand our portfolio of combination product opportunities, including galicaftor (SION-2222), which targets CFTR’s transmembrane domain 1 (“TMD1”), and has completed Phase 2 clinical
trials. In addition, we have recently completed a Phase 1 clinical trial evaluating SION-109