aibioSionna Therapeutics cuts about 46% of workforce, sees cash into second half of 2029
Tickers SION
Sionna Therapeutics said it will cut about 46% of its workforce, expects about $6.4 million in restructuring charges, and expects its cash to last into the second half of 2029. The cuts follow a missed key endpoint for SION-719 in a Phase 2a trial.
Key facts
- Company
- Sionna Therapeutics, Inc. (NASDAQ: SION)
- News type
- Distress
- Primary source
- Sionna Therapeutics, Inc. 8-K (2026-09-14)
Sionna Therapeutics, Inc. announced on September 14, 2026 that its board approved a workforce reduction of about 46%, along with other cost-saving measures. The company furnished the announcement with a Form 8-K. It says the cuts are meant to focus resources on its SION-451 and SION-2222 dual combination and to extend its operating runway. The company estimates aggregate restructuring and related charges of about $6.4 million. The release does not give the number of employees before or after the cut.
The runway
The company says it ended the second quarter of 2026 with about $268.3 million in cash, cash equivalents and marketable securities. It estimates that the workforce reduction, the discontinuation of SION-719 as an add-on to standard of care, and the other cost measures will extend its cash runway into the second half of 2029. A 10-Q filed August 6, 2026 separately reports $63.3 million in cash and cash equivalents at June 30, 2026.
The annual report, filed March 2, 2026, shows a 2025 net loss of $75.3 million, up from $61.7 million in 2024. Cash used in operations was $66.3 million in 2025, against $52.8 million in 2024. Research and development expense was $60.3 million in 2025 and $57.3 million in 2024. Year-end 2025 cash and cash equivalents were $58.5 million.
The trial that missed its endpoint
The release says the PreciSION CF Phase 2a trial did not achieve its key activity endpoint. That trial was a randomized, double-blind, placebo-controlled crossover study of SION-719 added to Trikafta, Vertex's approved triple combination, in 15 adult participants with two copies of the F508del mutation. Sweat chloride change was the key activity measure. Across the 14 evaluable participants, the placebo-adjusted change was -1.0 mmol/L in the primary analysis and -1.1 mmol/L in a prespecified secondary analysis.
After the topline results, the company ran a post hoc analysis. It identified three participants with drug exposures consistent with non-adherence (one with SION-719 and two with components of Trikafta), and said that excluding them produced a mean placebo-adjusted change of -8.6 mmol/L in the secondary analysis. The company believes the secondary analysis best accounts for the variability between treatment periods. The post hoc analysis is not the trial's prespecified result, the figure rests on a smaller group than the 14 evaluable patients, and the release itself says post hoc analyses are exploratory and may not reliably predict future outcomes.
The release also reports that Trikafta exposures fell by approximately 25-30% on average during SION-719 treatment periods, and it says a possible interaction between NBD1 stabilizers and a potentiator such as ivacaftor may have blunted any benefit. The company believes SION-719 was biologically active but that pharmacokinetic outliers and complex interactions may have affected the outcome.
The next trial
The company plans to move SION-451 and SION-2222 into an AscenSION CF Phase 2a proof-of-concept trial. That trial would be open label and enroll adults with two copies of F508del, who would switch from Trikafta to the combination for 28 days. Because it is open label, it has no placebo comparison. The company expects it to start in the first quarter of 2027.
The supporting Phase 1 study was in healthy volunteers. The company announced topline results for it on August 10, 2026, and says it achieved its safety, tolerability and pharmacokinetic objectives. The release says the planned doses fell within the range associated with meaningful improvement in CFTR function in the company's cell-based assay, which is a preclinical measure and not a patient outcome.
The business
Sionna describes itself as a clinical-stage biopharmaceutical company developing medicines for cystic fibrosis. Its annual report says at least two-thirds of patients on the current standard of care do not have normal CFTR function. PreciSION CF, the Phase 2a trial of SION-719, missed its key activity endpoint, and the release says the company is not advancing SION-719 as an add-on to standard of care.
The release names no new financing and does not say how much of the restructuring charge will be paid in cash.