Sionna lays off 46% of workforce in strategic shift after cystic fibrosis trial fail

Biotech Sionna lays off 46% of workforce in strategic shift after cystic fibrosis trial fail By James Waldron Sep 15, 2026 7:19am Sionna Therapeutics layoffs cystic fibrosis Sionna Therapeutics is laying off almost half of its workforce as the company reels from the failure of its closely watched cystic fibrosis (CF) add-on program. A month ago, Sionna revealed that a small study of its NBD1 stabilizer SION-719 on top of Vertex Pharmaceuticals’ Trikafta wasn’t able to trigger a statistically significant reduction in sweat chloride among patients with CF homozygous for the F508del mutation. The failure seemed to put paid to Sionna’s most advanced attempt to challenge Vertex for the CF market.

Investors drove Sionna’s stock down 90% in the aftermath of the readout, and the company has spent the following five weeks deciding on a path forward. Now, the biotech has opted to push ahead into a phase 2 study of another of its NBD1 stabilizers, dubbed SION-451, combined with its CFTR corrector SION-2222 for patients with CF homozygous for F508del. “It was important for us to take the time to complete a comprehensive post hoc data analysis to better understand the SION-719 PreciSION CF trial results and their potential implications before determining the right path forward for our dual combination,” Sionna CEO Mike Cloonan said in a Sept.

14 release. “The analysis identified important factors that we believe complicated interpretation of the trial and may have blunted the impact of NBD1 stabilization,” Cloonan added. “The post hoc findings, together with the favorable phase 1 results for SION-451 plus SION-2222, support advancing the dual combination into phase 2a.” This combo treatment already hinted at its potential last month when Sionna pitted the SION-451 and SION-2222 option against a combo of SION-451 and another CFTR corrector called SION-109.

Target exposures exceeded the level Sionna set before the failed PreciSION CF readout, with SION-451 plus SION-2222 emerging as the preferred combination. To keep the resources flowing to this new strategy, Sionna is reducing its headcount by around 46%, including the departure of Chief Business Officer Caroline Stark Beer. The company oversaw 59 full-time employees at the start of the year.

Sionna said it expects to “retain the core clinical, scientific, regulatory, technical and corporate capabilities required to advance the dual combination program.” The biotech ended June with $268.3 million in the bank, and said it expects the restructuring to cost around $6.4 million in the near-term while extending the company’s cash runway into the second half of 2029. Sionna Therapeutics layoffs cystic fibrosis Biotech