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

• The drug, SION-719, was being tested as an addition to Vertex Pharmaceuticals' 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.

Aug 10 (Reuters) - Sionna Therapeutics 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.