Sionna Therapeutics on Thursday raised $191 million in an initial public offering that will fund its plan to challenge Vertex Pharmaceuticals’ dominant cystic fibrosis franchise.
The company sold nearly 10.6 million shares at $18 apiece, more than it projected in a filing earlier this week. It will start trading Friday on the Nasdaq stock exchange under the ticker symbol “SION.”
Sionna is pitching itself as a future threat to Vertex, which since 2012 has brought five cystic fibrosis drugs to market that collectively treat about 90% of people with the condition.
Vertex’s drugs generated about $10 billion in sales in 2023 and were on track to surpass that total last year. Those therapies have proven tough for other would-be rivals to match, too. Several, like AbbVie, Translate Bio and Proteostasis Therapeutics, have fallen short. Still, Sionna noted in its IPO prospectus how two-thirds of people on Vertex’s top-selling Trikafta don’t have normal CFTR function. People on Trikafta or other cystic fibrosis drugs can also still see their lung function decline.
Sionna said its drugs could improve upon Vertex’s medicines by more completely restoring the function of the protein, CFTR, that’s defective in cystic fibrosis. In its prospectus, the company said it has two “stabilizers” in early human testing that target an important, but difficult-to-reach area of the protein. It intends to select one to evaluate alongside Trikafta in further testing.
The company will separately search through its portfolio — which includes a trio of drugs licensed from AbbVie — for a unique two-drug regimen to advance. Multiple combination studies are planned this year.
Sionna was formed in 2019 and, prior to its IPO, had already secured about $330 million in venture funding from prominent investors such as RA Capital Management, Atlas Venture and OrbiMed. Upon raising its last round in 2024, CEO Mike Cloonan told BioPharma Dive that the funding would allow Sionna to consider an IPO “at a time that’s most advantageous to us.”
“We have the capital to make sure the data that we have is the most powerful data that we can have in advance of going public,” Cloonan said at the time.
Like Sionna, the six other biotechs to either outline IPO plans or go public in 2025 have drugs in human testing. Ascentage Pharma, Maze Therapeutics and Metsera — the three to price offerings in January — collected $541 million combined.
The majority of biotech IPOs, though, fared poorly in recent years, and 2024 was no exception — several companies to go public since last January have already suffered significant setbacks. The two top performers, CG Oncology and Arrivent Biopharma, had cancer drugs in late-stage trials when they debuted on Wall Street.
