Sionna said SION-719 missed the key activity endpoint in its Phase 2a PreciSION CF study, showing a mean placebo-adjusted sweat chloride change of -1.0 mmol/L with a p-value of 0.7.
The failure prompted the biotech to stop developing SION-719 as an add-on to Trikafta, though it is still reviewing the topline data received Friday for possible confounding factors.
Those factors included higher-than-expected variability in sweat chloride measurements and differences in Trikafta exposure between the SION-719 and placebo periods.
SION-719 was generally well tolerated over 14 days, with mostly mild to moderate adverse events, no serious adverse events and no meaningful liver-function safety signal.
A separate Phase 1 study met safety, tolerability and pharmacokinetic goals for SION-451 combinations, but Sionna is reassessing the broader program after the SION-719 setback.