Investing.com -- Vertex Pharmaceuticals (NASDAQ: VRTX) shares rose 6% in early trading after Sionna Therapeutics reported its experimental cystic fibrosis treatment failed a key clinical trial, removing a potential competitive threat to Vertex's franchise.

Sionna Therapeutics (NASDAQ: SION) announced that its Phase 2a proof-of-concept trial of SION-719, tested as an add-on to Vertex's cystic fibrosis standard of care treatment Trikafta, failed to meet its primary endpoint of sweat chloride reduction. The study showed a non-statistically significant -1.0 mmol/L mean placebo-adjusted sweat chloride improvement.

Sionna said potential factors including sweat chloride variability and Trikafta exposure variability between treatment and placebo arms could have confounded the data. The company will not pursue development of SION-719 in combination with Trikafta.

BMO Capital analyst Evan David Seigerman commented, "We view this clinical development as a strong positive for VRTX; Expect shares strength on a major overhang removed."

The trial failure reinforces the durability of Vertex's cystic fibrosis franchise, according to Seigerman. Trikafta remains the standard of care treatment for cystic fibrosis patients without a successful challenger emerging from Sionna's development program.