Sionna Therapeutics said Monday that its experimental pill for cystic fibrosis did not show any benefit when added onto Vertex Pharmaceuticals' Trikafta in a Phase 2 trial. The company announced it will no longer try to advance the drug, called SION-719, as an add-on therapy for cystic fibrosis patients.
Following the announcement, Sionna Therapeutics stock plunged 92%. The Phase 2 trial was testing whether Trikafta and SION-719 could help lower sweat chloride levels more effectively than Trikafta alone. Going into the trial, Sionna executives had suggested that an improvement of 10 millimoles per liter of sweat would be clinically meaningful and differentiate its drug.
Sionna Therapeutics said the sweat chloride improvement number was just 1 millimole per liter, a difference that wasn't statistically significant. Stifel analyst Paul Matteis said the data are 'hard to explain [and] leaves us puzzled.'
RBC Capital Markets' Brian Abrahams wrote that the unfavorable setup of Sionna Therapeutics having a high valuation going into the readout played out. He called the news a 'clearing event' that makes him much more confident in recommending that investors buy Vertex Pharmaceuticals shares.
Challenging a blockbuster franchise
Sionna Therapeutics is one of many companies that have faltered in challenging Vertex Pharmaceuticals' main business. Vertex's Trikafta reached the market in 2019 and changed the lives of tens of thousands of cystic fibrosis patients, earning the company billions of dollars. Its main business is a multi-drug franchise projected to bring in $13 billion in revenue this year.
Sionna Therapeutics' goal has been to improve upon Vertex Pharmaceuticals' pioneering therapies, which modulate a key protein that is defective in cystic fibrosis. The company claimed its drugs could help normalize function of the CFTR protein in ways Vertex's medicines don't. Sionna amassed a portfolio of drugs designed to stabilize a particularly tricky region of the defective CFTR protein and licensed some drug prospects from AbbVie.
Sionna Therapeutics raised hundreds of millions of dollars in private and public funding since it was founded in 2019. Prior to this failure, the company reported positive data from a Phase 1 trial testing one of the AbbVie-acquired drugs in combination with a therapy Sionna developed.
Regarding next steps, Sionna Therapeutics hinted at potential layoffs, saying it will 'take actions to preserve capital while evaluating next steps.'
