Sionna Therapeutics Completes Enrollment in PreciSION CF Phase 2a Trial Evaluating NBD1 Stabilizer, SION-719, Added to Standard of Care in Participants with Cystic Fibrosis

WALTHAM, Mass., April 27, 2026 — Sionna Therapeutics, Inc. (Nasdaq: SION), a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis (CF), today announced the completion of enrollment in the PreciSION CF Phase 2a proof-of-concept (POC) trial. This trial is evaluating SION-719, a first-in-class nucleotide binding domain 1 (NBD1) stabilizer, when added to Trikafta® (elexacaftor/tezacaftor/ivacaftor), the current standard of care (SOC) in CF. Sionna anticipates data from the PreciSION CF trial in the summer of 2026.

“Completion of enrollment in our PreciSION CF proof-of-concept trial represents a significant milestone for both Sionna and the cystic fibrosis community,” said Charlotte McKee, M.D., Chief Medical Officer of Sionna. “This is the first clinical trial evaluating an NBD1 stabilizer in people with CF, marking an important step toward directly addressing the underlying defect of the most common CF-causing mutation. We are thankful to the patients, investigators, and the broader CF community for their strong engagement as we advance this trial. We remain focused on executing and look forward to our first data readout in CF patients this summer.”

The PreciSION CF Phase 2a trial (NCT07108153) is a randomized, double-blind, placebo-controlled, crossover POC study that enrolled adult CF patients homozygous for F508del on a stable dose of physician-prescribed Trikafta. The objectives of the trial are to evaluate the safety, tolerability, and pharmacokinetics of SION-719 when administered with SOC and to assess change in sweat chloride levels, an important measure of CFTR function. The PreciSION CF trial is being conducted at multiple sites, including sites in the CF Foundation-supported Therapeutics Development Network (TDN), the largest CF clinical trials network in the world.

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 normalize 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 dramatic improvements in clinical outcomes and quality of life for people with CF. Leveraging more than a decade of the co-founders’ research on NBD1, Sionna is advancing a pipeline of small molecules engineered to correct the defects caused by the F508del genetic mutation, which resides in NBD1. Sionna is also developing a portfolio of complementary CFTR modulators that are designed to work synergistically with its NBD1 stabilizers to improve CFTR function. For more information about Sionna, visit www.sionnatx.com.

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