Sionna Therapeutics halts cystic fibrosis drug program after trial failure

Sionna Therapeutics has announced the discontinuation of its experimental drug, SION-719, following a mid-stage clinical trial that failed to demonstrate meaningful benefits for cystic fibrosis patients. The drug was being tested as an adjunctive treatment alongside Vertex Pharmaceuticals’ Trikafta in 15 adults.

The trial failed to significantly reduce chloride levels in patients’ sweat, a key metric for evaluating cystic fibrosis treatments. While the drug was generally well tolerated with only mild to moderate side effects, CEO Mike Cloonan expressed disappointment regarding the unexpected results. The company noted that variations in patient test results and Trikafta levels may have impacted the outcome.

Following the news, Sionna Therapeutics shares fell nearly 92% in premarket trading. The company is currently reviewing the data to determine its next steps. Sionna is also developing a separate two-drug treatment combining SION-451 and SION-2222, which recently met safety and drug-exposure goals in an early-stage study involving healthy volunteers.