Sionna’s cystic fibrosis candidate misses primary endpoint in Phase 2 trial, shares plunge

Sionna Therapeutics announced that its experimental cystic fibrosis drug SION-719 failed to meet the primary endpoint in a Phase 2 trial that added the drug to Vertex Pharmaceuticals' Trikafta.

The study measured change in sweat chloride levels, a biomarker for cystic fibrosis, and the combination did not produce a statistically significant, placebo-adjusted improvement over Trikafta alone.

After the announcement, Sionna's shares fell about 92% in early trading, leaving the company's market value below its cash holdings. Executives said they will take actions to preserve capital while evaluating next steps.

Vertex shares rose roughly 7% on the same day, reflecting continued market confidence in its Trikafta franchise.