Sionna Therapeutics cuts 46% of staff after cystic fibrosis trial miss

Sionna Therapeutics announced it will lay off roughly half of its employees as it reassesses its strategy following a recent setback in its cystic fibrosis program.

The company’s lead candidate, SION-719, was tested as an add-on to Vertex’s Trikafta in a small study of patients homozygous for the F508del mutation. The trial did not achieve a statistically significant reduction in sweat chloride, a key biomarker for cystic fibrosis.

The disappointing readout sent Sionna’s share price tumbling, and the board spent weeks evaluating options. It has now decided to continue development of a different NBD1 stabilizer, SION-451, in combination with its own CFTR corrector SION-2222, and plans to enter a phase-2 trial for the same patient population.