Sionna Therapeutics will not advance SION-719 as an add-on treatment to standard cystic fibrosis therapy after its Phase 2a PreciSION CF trial failed to meet its key activity endpoint of sweat chloride reduction.
The study evaluated the company’s nucleotide binding domain 1, or NBD1, stabilizer SION-719 in participants receiving Trikafta, the combination of elexacaftor, tezacaftor and ivacaftor. The trial produced a mean placebo-adjusted sweat chloride change of minus 1.0 mmol/L, which was not statistically significant, with a p-value of 0.7.
Sionna said SION-719 was generally well tolerated during 14 days of treatment alongside Trikafta. Most treatment-emergent adverse events were mild to moderate, and the study recorded no serious adverse events or meaningful liver-function-test trends. Still, the company said it does not plan to continue developing SION-719 as an add-on to current standard care.
The company is assessing factors that may have affected interpretation of the results, including higher-than-anticipated variability in individual sweat chloride measurements and differences in Trikafta exposure between SION-719 and placebo treatment periods. Sionna received the topline data Aug. 7 and said its analysis is ongoing.
Sionna also reported results from a separate Phase 1 study of SION-451, another NBD1 stabilizer, in proprietary dual combinations with SION-2222 or SION-109 in healthy volunteers. The study met safety, tolerability and pharmacokinetic objectives, including pre-defined target exposures.
Based on total data and observed target coverage, the company identified SION-451 plus SION-2222 as its preferred dual combination. In the once-daily SION-2222 cohorts, one participant discontinued because of a rash. In twice-daily SION-2222 cohorts, two participants discontinued due to elevated liver-function tests and flu-like symptoms. No serious adverse events were reported.
Sionna said it is evaluating next steps for SION-451 and will take actions to preserve capital. The company reported approximately $268.3 million in cash, cash equivalents and marketable securities as of June 30.
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