Sionna Raises $182 Million to Advance Novel Small Molecules in Cystic Fibrosis

Rare Daily Staff

Sionna Therapeutics, a clinical-stage company developing differentiated treatments for cystic fibrosis, closed a $182 million series C financing to support the clinical development of first-in-class small molecules designed to fully restore the function of faulty protein underlying cystic fibrosis.

Enavate Sciences led the upsized and oversubscribed round with new investors Viking Global Investors and Perceptive Advisors, as well as participation by all existing investors including RA Capital, OrbiMed, TPG’s The Rise Fund, Atlas Venture, the Cystic Fibrosis Foundation, funds and accounts advised by T. Rowe Price Associates, and Q Healthcare Holdings, a wholly owned subsidiary of QIA. Edd Fleming, executive vice president of commercialization at Enavate Sciences, is joining Sionna’s Board of Directors.

“We have deep experience in CF and a sharp focus on advancing the development of novel small molecules targeting NBD1 and complementary modulators that enable the potential for full restoration of CFTR function for most people living with CF,” said Mike Cloonan, president and CEO of Sionna. “This capital raise provides financial flexibility positioning us to execute our clinical development plan with funding through 2026 and multiple value-creating clinical readouts.”

Cystic fibrosis is caused by mutations in the CFTR gene, which codes for an epithelial ion channel that is essential for producing healthy, freely flowing mucus in the airways, digestive system, and other organs. The most common mutation in CFTR, ΔF508, causes NBD1 to unfold at body temperature and severely impairs CFTR function.

Sionna has presented preclinical data, including data from the clinically predictive human bronchial epithelial cell (CFHBE) model, that demonstrate its NBD1 stabilizers can restore ΔF508-CFTR maturation, trafficking, and function to wild-type levels when combined with complementary modulators. A phase 1 clinical trial of its first clinical-stage NBD1 stabilizer, SION-638, has identified doses that are generally safe and well tolerated, and target exposure (based on the CFHBE assay) was achieved at all doses, with more time above target with increasing dose.

Sionna has nominated two additional NBD1 stabilizers from its second series, SION-451 and SION-719, and plans to advance both compounds to clinical trials in 2024 pending results from ongoing GLP toxicology studies. In addition, the company is continuing to advance the development of compounds targeting complementary mechanisms including SION-109, which targets NBD1’s interface with the CFTR intracellular loop 4 (ICL4) region; a phase 1 clinical trial with SION-109 began in January 2024.