Sionna raises another $182M to challenge Vertex in cystic fibrosis

Dive Brief:

• Sionna Therapeutics, a Waltham, Massachusetts biotechnology startup, announced Wednesday it raised a $182 million Series C round to advance a group of experimental drugs for cystic fibrosis.  
• Founded in 2019 and incubated by investment firm RA Capital, the company aims to challenge Vertex Pharmaceuticals’ market-leading cystic fibrosis business. The company has five drugs in development, all of which work differently than Vertex’s medicines. Two are in clinical testing, and two more could join them by the end of 2024. 
• The company’s funding round was led by Enavate Sciences and involved participation from new investors Viking Global Investors and Perceptive Advisors, as well as all of its previous backers. The startup has now raised $332 million since its launch. 

Dive Insight:

Over the last decade, Vertex has built a dominant business in cystic fibrosis, one that’s turned it into one of the sector’s largest companies. The group of drugs it sells generated nearly $10 billion in sales in 2023.

Vertex has established that supremacy, in part, by fending off multiple competitors. Would-be challengers like AbbVie, Translate Bio and Proteostasis Therapeutics fell short in clinical testing. In the meantime, Vertex has raised the bar for its rivals, developing a series of medicines reaching more and more patients.

With the approval of Trikafta in 2019, Vertex’s drugs can now address up to 90% of the population with cystic fibrosis. That’s left some startups searching for ways to help the other 10%, instead of going after Vertex. 

Sionna is different, however. The startup is developing drugs for the same group of patients Vertex currently treats, but that are designed to work differently. It claims that Vertex’s therapies only partially restore the function of the protein, known as CFTR, that’s defective in cystic fibrosis. Sionna’s drugs “have the potential to get all the way up into normal CFTR function, much higher than where the standard of care is today,” said Mike Cloonan, Sionna’s CEO and a former Sage Therapeutics and Biogen executive.

Those therapies zero in on what’s called NBD1, a region of the CFTR protein that’s been historically tough to drug. The company says that Phase 1 trials of its first prospect, code-named SION-638, identified doses that were safe and well-tolerated. Sionna has nominated two others to bring into testing this year, while also working on medicines that target a “complementary” mechanism. One of them, SION-109, is also in early testing. 

The Series C raise gives Sionna enough cash to operate through 2026, enabling it to design multiple early- and mid-stage trials, Cloonan said.

Raising more funds also enables Sionna to consider an initial public offering “at a time that’s most advantageous to us,” he said. “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.”

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