BIOBRIEF
A 15 patient Phase 2a study tested its experimental CF pill SION 719 as a complement to Vertex's standard cystic fibrosis therapy Trikafta; the company is shelving the drug and said it would take steps to preserve capital, a phrase investors read
Sionna Therapeutics lost roughly 90% of its pre-market value on Monday after a 15-patient Phase 2a study of SION-719, a pill the company was developing to add incremental benefit on top of Vertex's Trikafta, the dominant cystic fibrosis therapy. The study missed its key endpoint with a -1.0 mmol/L placebo-adjusted sweat chloride change (p=0.7).
The trial had aimed for a roughly 10 mmol/L drop in sweat chloride, a CF biomarker, on top of Trikafta. SION-719 was an NBD1 stabilizer, a small molecule meant to fix a different part of the defective CFTR protein than the modulators in Trikafta. The 15 patients, all on Trikafta, got 14 days of SION-719 on top. The drug was generally well tolerated, Sionna said.
Sionna will not advance SION-719 as an add-on to standard of care, citing higher-than-expected sweat chloride variability and differences in Trikafta exposure between drug and placebo periods. The company ended Q2 with about $268.3 million in cash and said it would "take actions to preserve capital while evaluating next steps", a phrase investors read as a layoff signal.
Vertex shares rose about 6% intraday. BMO framed the result as a positive for Vertex, and Truist said the lack of any activity signal "underscores the difficulty" of building add-ons on top of effective modulators. The open question is whether the NBD1 mechanism has any headroom on top of Trikafta at all.