Sionna Therapeutics Announces Workforce Reduction and Pivot to New Cystic Fibrosis Program
Sionna Therapeutics Inc (NASDAQ:SION) saw its shares decline approximately 3% in after‑hours trading on Monday following the disclosure of a 46% cut to its workforce. The board approved the reduction and accompanying cost‑saving measures, estimating restructuring charges of about $6.4 million.
The company is shifting its development focus to a proprietary dual combination therapy, SION‑451 plus SION‑2222, which will move into a Phase 2a clinical trial expected to commence in the first quarter of 2027. This new program, named AscenSION CF, will be an open‑label study enrolling adults with cystic fibrosis who are homozygous for the F508del mutation. Participants will transition from Trikafta to the dual combination for a 28‑day treatment period, during which sweat chloride levels, safety parameters, and pharmacokinetics will be evaluated.
The pivot follows an extensive review of data from the earlier PreciSION CF Phase 2a trial of SION‑719, an add‑on to Trikafta evaluated in 15 adult participants with the same genotype. The trial did not meet its primary activity endpoint. Post‑hoc analyses, however, identified a subset of participants showing a mean placebo‑adjusted sweat chloride reduction of up to –8.6 mmol/L, consistent with the intended NBD1 biological activity. The company attributed the overall trial outcome to three factors: (1) drug‑exposure outliers linked to non‑adherence in three participants, (2) reduced exposure to Trikafta components during SION‑719 treatment, and (3) possible pharmacodynamic interactions between the NBD1 stabilizer and ivacaftor that may have attenuated efficacy.
Financially, Sionna ended the second quarter of 2026 with cash, cash equivalents, and marketable securities totaling approximately $268.3 million. Management projects that this liquidity will sustain operations into the second half of 2029.