Sionna said on Monday that its mid-stage trial of SION-719 in 15 adults with cystic fibrosis already taking Vertex’s Trikafta failed to meet its main goal.
- Sionna said it will not advance SION-719 as an add-on therapy with Trifakta anymore.
- Stifel downgraded Sionna to Hold from Buy with a $7 target, from $55, saying it was “disappointed and very surprised” by the failure.
- Sionna ended the second quarter with about $268 million in cash and said it plans steps to preserve capital while assessing its path forward.
Shares of Sionna Therapeutics (SION) plunged roughly 92% on Monday after the biotech firm reported that its experimental cystic fibrosis drug failed to deliver meaningful benefits in a mid-stage trial, prompting it to abandon plans for the treatment as an add-on to existing standard care.
Sionna said its mid-stage trial of SION-719 in 15 adults with cystic fibrosis already taking Vertex’s (VRTX) Trikafta failed to meet its main goal. The drug barely lowered sweat chloride levels—a key marker of improved protein function—showing a minor difference versus placebo that was not statistically significant.
The stock is now on track for its worst day ever, if losses hold. VRTX stock, meanwhile, rose 7%, eyeing its best day since early March.
Trial Miss Ends One Program; Another Remains Under Review
Cystic fibrosis is a genetic condition that causes thick mucus to build up in the lungs and other organs, leading to breathing problems and infections. Trikafta is the leading approved treatment. Sionna had hoped SION-719 could further improve outcomes when added on top, but the company said it will not advance the drug in that role anymore after the trial outcomes.
The drug was generally well tolerated over 14 days, with mostly mild-to-moderate side effects and no serious issues. Sionna noted possible complicating factors, including unexpected variability in patients’ sweat chloride readings and differences in Trikafta levels during the study periods. It is still analyzing those results.
In a separate early-stage study in healthy volunteers, combinations involving Sionna’s related drug SION-451 met safety, tolerability, and exposure goals. The company said it is evaluating next steps for a combination of SION-451 with SION-2222.
“We are disappointed in the unexpected results from the Phase 2a trial,” said CEO Mike Cloonan. “We are further evaluating the data to decide on next steps for the SION-451 dual combination.”
Sionna ended the second quarter with about $268 million in cash and said it plans steps to preserve capital while assessing its path forward.
Analysts Weigh On VRTX, SION
Wall Street quickly weighed in. Bank of America raised its price target on Vertex to $672 from $605 and kept a ‘Buy’ rating, saying Sionna’s trial miss removes an overhang that investors had viewed as a potential threat to Vertex’s cystic fibrosis franchise.
Raymond James downgraded Sionna to ‘Market Perform’ from ‘Strong Buy’, calling the trial a clear failure and citing added uncertainty from possible drug interactions and safety signals.
Wedbush cut Sionna to ‘Neutral’ from ‘Outperform’ and lowered its target to $5 from $53, saying that questions remain about the platform’s potential, while shifting any SION-451 launch possibility to 2033.
Stifel downgraded Sionna to ‘Hold’ from ‘Buy’ with a $7 target, from $55, saying it was “disappointed and very surprised” by the failure and sees no clear Buy case until management explains what went wrong.
How Did SION Retail Traders React?
On Stocktwits, retail sentiment around SION stock jumped from ‘neutral’ to ‘extremely bullish’ territory over the past 24 hours, while message volume rose from ‘normal’ to ‘extremely high’ levels.
A Stocktwits user highlighted the company’s cash position and termed the stock a steal at current prices.
Another user took a more pessimistic take and wrote, “It may climb from here, but the story is dead.”
SION stock has fallen about 89% year-to-date.
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