Sionna Therapeutics to Present Data at the 2026 North American Cystic Fibrosis Conference

Previously disclosed post hoc PreciSION CF analyses of SION-719 support advancement of SION-451 + SION-2222 into the AscenSION CF Phase 2a proof-of-concept trial

New preclinical data evaluating NBD1 stabilizers in combination with other CFTR modulators across F508del genotype groups demonstrated the potential of NBD1 stabilizer-based combinations to benefit a broad population of people with CF

WALTHAM, Mass., Oct. 08, 2026 (GLOBE NEWSWIRE) — Sionna Therapeutics, Inc. (Nasdaq: SION), a clinical-stage biopharmaceutical company on a mission to develop novel medicines for cystic fibrosis (CF), today announced data being presented at the 2026 North American Cystic Fibrosis Conference (NACFC) being held in Atlanta, Georgia on October 7-10, 2026.

Details of the presentation and posters are as follows:

Presentation Title: NBD1 is a novel target in Cystic Fibrosis, Clinical Learnings and Research Data
Presenters: Gregory S. Sawicki, M.D., M.P.H., Director of the Cystic Fibrosis Center at Boston Children’s Hospital and Associate Professor of Pediatrics at Harvard Medical School and Steve Altmann, M.S., Director of Research, Sionna Therapeutics
Session Title: S09 – Approaches to Increasing CFTR Expression & Function
Date and Time: Thursday, October 8th, 2026, 4:30 p.m. – 6:30 p.m. ET

Presentation Summary:
The oral presentation by Dr. Sawicki is a summary of the previously disclosed post hoc analyses of the PreciSION CF Phase 2a trial evaluating NBD1 stabilizer SION-719 when added to Trikafta. Although the trial did not achieve its key activity endpoint, post hoc analyses excluding three participants with PK patterns consistent with dosing non-adherence showed a mean placebo-adjusted sweat chloride reduction of 8.6 mmol/L. The analyses also identified lower exposures of all three Trikafta components during SION-719 treatment periods, signaling a complex four-drug interaction. In addition, there was a potential interaction between the NBD1 stabilizer SION-719, and the potentiator, ivacaftor, that may have blunted the additional benefit of NBD1 stabilization. The Company believes these findings alongside the nonclinical data presented by Steve Altmann are consistent with NBD1 biological activity. Taken together with favorable Phase 1 safety, tolerability and PK results, these data support advancing SION-451 + SION-2222 into AscenSION CF, an open-label, 28-day Phase 2a proof-of-concept trial assessing sweat chloride, safety and PK in adults with CF homozygous for F508del. The trial is expected to begin in the first quarter of 2027.

Poster Title: Assessing the effect of NBD1 stabilizers SION-451 and SION-719 in combination with other CFTR modulators on primary human bronchial epithelial cells from F508del/F508del and F508del/null donors
Authors: S. Altmann, S. Bercury, J. Foley, Z. Gao, A. Hunnicutt, Liao, A. Madanjian, M. Munson, G. Topalov, G. Hurlbut.
Poster Number: 295

Poster Summary: Sionna conducted preclinical experiments to assess the effects of Sionna’s clinical-stage NBD1 stabilizers, SION-451 and SION-719, in combination with complementary modulators, including SION-2222 (TMD1-directed modulator) and SION-109 (ICL4-directed modulator), across primary CF human bronchial epithelial (CFHBE) cells from donors with either one or two copies of F508del. Across both donor groups, NBD1-stabilizer combinations demonstrated improved CFTR trafficking and function up to wild-type levels, supporting their potential to benefit a broad population of people with CF.

The presentation and poster are available under the “Scientific Presentations” section within the Science page of Sionna’s website at https://www.sionnatx.com/our-science/.  

About Sionna Therapeutics
Sionna Therapeutics is a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis (CF) by developing novel medicines that improve the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Sionna’s 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), which Sionna believes is central to potentially unlocking meaningful improvements in clinical outcomes and quality of life for people with CF. For more information about Sionna, visit www.sionnatx.com.

Cautionary Note Regarding Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, implied and express statements about Sionna’s beliefs and expectations regarding: its goal of transforming the treatment paradigm for CF; its interpretation of the results of the PreciSION CF trial and the impact of potential confounding factors on the interpretation of those results; the potential for NBD1 stabilization to improve CFTR function and produce clinical benefit, including beliefs about biological activity of SION-719 in PreciSION CF and the translatability of preclinical and in vitro assay data to clinical outcomes; the objectives, design, timing, initiation and conduct of a planned Phase 2a proof-of-concept trial of SION-451 + SION-2222; the therapeutic potential, clinical benefits and safety of SION-451 + SION-2222; and other statements that are not historical facts.

In some cases, forward-looking statements can be identified by terms such as “may,” “will,” “should,” “would,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “believe,” “estimate,” “predict,” “potential” or “continue,” or the negative of these terms or other similar expressions. Any forward-looking statements are based on management’s current expectations and beliefs and are subject to risks, uncertainties and important factors that may cause actual events or results to differ materially, including uncertainties inherent in developing product candidates; interpreting the PreciSION CF results and potential confounding factors; the inherent limitations of post hoc analyses, which are exploratory and may not reliably predict future outcomes; the risk that in vitro and preclinical data may not translate to clinical benefit; the risk that results observed with one compound may not be predictive of results with a different compound or combination; and designing and conducting the planned Phase 2a trial.   Additional risks include the Company’s ability to demonstrate that its candidates are safe and effective; obtain regulatory feedback or approvals; achieve anticipated restructuring savings and runway extension; retain key personnel and capabilities following the workforce reduction; secure sufficient funding; and respond to general economic, industry and market conditions.   These risks and uncertainties are described in “Risk Factors” in Sionna’s most recent Quarterly Report on Form 10-Q and subsequent filings with the Securities and Exchange Commission. The events and circumstances reflected in the forward-looking statements may not be achieved or occur.   Any forward-looking statements represent Sionna’s views only as of today and should not be relied upon as representing its views as of any subsequent date. Sionna disclaims any obligation to update any forward-looking statements except as required by law. No representations or warranties, express or implied, are made about the accuracy of any such forward-looking statements.

Investor & Media Contact 
Juliet Labadorf 
ir@sionnatx.com 
media@sionnatx.com