Sionna's SION-719 misses key endpoint in Phase 2a cystic fibrosis trial

Sionna Therapeutics announced topline results on August 10, 2026 from two nucleotide binding domain 1 stabilizer programs in cystic fibrosis. The PreciSION CF trial did not meet its key activity endpoint, with a -1.0 mmol/L mean placebo-adjusted sweat chloride change (p=0.7).¹

The company noted potential confounders were observed in the trial, including higher than anticipated levels of variability in individual sweat chloride levels and differences in Trikafta exposure levels between the SION-719 and placebo periods, which the company is evaluating for their impact on interpretation of the data.¹ Safety data showed SION-719 was generally well tolerated when added to Trikafta for 14 days with most treatment emergent adverse events mild to moderate, no serious adverse events, and no meaningful trends in adverse events related to liver function tests.¹ Based on these findings, Sionna does not plan to advance SION-719 as an add-on to standard of care.¹

In a separate Phase 1 trial, SION-451 in dual combinations with either SION-2222 or SION-109 achieved the safety, tolerability, and pharmacokinetic objectives, including target exposures defined prior to the Phase 2a PreciSION CF results.¹ Based on the totality of the data and target coverage observed, SION-451 plus SION-2222 was identified as the preferred dual combination.¹ Sionna is evaluating next steps for the SION-451 program.¹

Financially, Sionna ended Q2 with approximately $268.3 million in cash, cash equivalents, and marketable securities, and the company intends to take actions to preserve capital while evaluating next steps.¹