Sionna cuts 46% of staff after cystic fibrosis trial failure, pivots to new drug combination

Sionna Therapeutics plans to cut approximately 46% of its workforce as part of a restructuring announced September 14–15, 2026.

The move follows failure of the Phase 2a PreciSION CF trial evaluating SION-719 alongside Vertex’s Trikafta in cystic fibrosis patients homozygous for the F508del mutation.

SION-719 produced only a 1.0 mmol/L mean placebo-adjusted reduction in sweat chloride, with p=0.7, and failed to meet the study’s key activity endpoint. Sionna will not advance it as an add-on therapy.

The company will focus resources on a different dual combination:
SION-451 plus SION-2222. A Phase 2a proof-of-concept study, called AscenSION CF, is expected to begin in the first quarter of 2027.

Sionna said post-hoc analyses suggested possible confounding factors in the failed trial, including exposure outliers, lower Trikafta component levels, and a potential interaction with ivacaftor.

The restructuring is expected to cost about $6.4 million but extend Sionna’s cash runway into the second half of 2029. Chief Business Officer Caroline Stark Beer is among the departures.