Sionna scraps genetic disorder drug program after trial setback; shares tank

Sionna Therapeutics

10/08/2026 13:03

Aug 10 (Reuters) - Sionna Therapeutics SION.O said on Monday it would stop developing its experimental drug as an addition to standard treatment for a type of genetic disorder after it failed to show a meaningful benefit in a mid-stage trial.
Shares of the company fell nearly 92% in premarket trading. 
The drug, SION-719, was being tested as an addition to Vertex Pharmaceuticals' VRTX.O Trikafta in 15 adults with cystic fibrosis, a genetic disease that causes thick mucus to build up in the lungs and can lead to breathing problems and repeated infections.
SION-719 failed to significantly lower chloride levels in patients' sweat, an important measure of whether a cystic-fibrosis treatment is working.
Sionna said variations in patients' test results and differences in their Trikafta levels may have influenced the trial's outcome. 
"We are disappointed in the unexpected results," CEO Mike Cloonan said, adding that the company is reviewing the data before deciding its next steps.
The drug was generally well tolerated during the 14-day study, with most side effects being mild to moderate and no serious side effects reported.
Sionna is separately developing a two-drug treatment for cystic fibrosis combining SION-451 with SION-2222. An early-stage study in healthy volunteers met its safety and drug-exposure goals, but the company is reviewing its next steps for the program.

 (Reporting by Kunal Das in Bengaluru; Editing by Mrigank Dhaniwala)
 ((Kunal.Das2@thomsonreuters.com;))