Clinical-stage biopharmaceutical company Sionna Therapeutics Inc. (NASDAQ:SION) announced topline clinical trial results from two nucleotide binding domain 1 (NBD1) stabilizer candidate programs targeting cystic fibrosis (CF).
The findings indicated that its PreciSION CF Phase 2a trial assessing SION-719 missed its key primary activity target, leading the company to halt further advancement of SION-719 as an add-on therapy.
SION-719 Fails Primary Endpoint In Phase 2a Trial
In the PreciSION CF Phase 2a proof-of-concept study, SION-719 was evaluated in combination with Trikafta (elexacaftor/tezacaftor/ivacaftor) among CF participants.
The trial yielded a -1.0 mmol/L mean placebo-adjusted change in sweat chloride (p=0.7), falling short of its activity target.
Sionna highlighted potential confounders, such as unexpected variability in individual sweat chloride levels and differences in Trikafta exposure across the SION-719 and placebo periods.
The firm received the data on August 7, 2026, and is actively analyzing these elements.
Although SION-719 proved generally well tolerated over 14 days with mostly mild-to-moderate treatment-emergent adverse events and no serious adverse events or liver function trends, Sionna will not advance the candidate further.
Phase 1 Trial Meets Safety Objectives for Dual Combinations
Separately, Sionna shared results from a Phase 1 study of SION-451 in proprietary dual combinations with SION-2222 or SION-109 in healthy subjects.
The trial fulfilled its target safety, tolerability, and pharmacokinetic objectives. Based on overall data and target coverage, the SION-451 and SION-2222 pairing was chosen as the preferred dual-combination regimen.
SION-451 twice-daily paired with SION-2222 once-daily was generally well tolerated, with one discontinuation caused by a rash.
In twice-daily cohorts for both drugs, most adverse events were mild to moderate, though two subjects discontinued due to elevated liver function tests and flu-like symptoms.
SION-451 and SION-109 combinations were also generally well tolerated, and Sionna is evaluating future steps.
SION Price Action: Sionna Therapeutics shares were down 91.84% at $4.86 at the time of publication on Monday. The stock is trading at a new 52-week low, according to Benzinga Pro data.
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