Sionna Therapeutics IPO Could Fuel Next-Gen Cystic Fibrosis Therapies

On February 10, 2025, Sionna Therapeutics Inc. announced the successful closing of its upsized initial public offering (IPO).

The Sionna Therapeutics IPO saw the company sell 12,176,467 shares of common stock at $18.00 per share — including an additional 1,588,234 shares from the underwriters’ option.

With gross proceeds of approximately $219.2 million (before deducting underwriting discounts, commissions and other expenses) — Sionna has marked a major milestone in its growth journey. Trading on the Nasdaq Global Market began on February 7, 2025, under the ticker “SION”.

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Sionna is a clinical-stage biopharma company dedicated to developing innovative treatments for cystic fibrosis — a genetic disorder that impairs lung and digestive function.

Sionna’s approach centers on normalizing the activity of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, which regulates salt and water movement in cells.

The core innovation is stabilizing the protein’s nucleotide-binding domain 1 (NBD1), long considered “undruggable.” By targeting NBD1, Sionna aims to repair the cellular “engine” disrupted by the F508del mutation, affecting nearly 90% of cystic fibrosis patients.

Building on over a decade of research, Sionna is advancing a robust pipeline of small molecules.

Its lead investigational candidates, SION-719 and SION-451, are currently in Phase I clinical trials in Australia, assessing safety, tolerability and pharmacokinetics. These trials have completed several single and multiple ascending dose cohorts with over 60 and 70 healthy subjects, respectively, with early results indicating that both compounds are well tolerated and reach target concentration levels that could restore near-normal CFTR function.

The company also employs a cystic fibrosis human bronchial epithelial model — a system that mimics lung tissue — to guide treatment optimization.

In parallel, Sionna is developing complementary CFTR modulators, including correctors and potentiators, designed to work synergistically with its NBD1 stabilizers — much like tuning different engine components for optimal performance.

Alongside the news of Sionna Therapeutics’ IPO, 2025 is emerging as a promising year for cystic fibrosis innovation. Vertex Pharmaceuticals secured FDA approval late last December for its once-daily triple combination CFTR modulator, Alyftrek (vanzacaftor/tezacaftor/deutivacaftor).

More recently, Boehringer Ingelheim initiated the LENTICLAIR 1 trial — a Phase I/II study evaluating BI 3720931, a first-in-class inhaled lentiviral vector-based gene therapy that utilizes OXB’s advanced manufacturing technology to insert a functional CFTR gene in airway cells, addressing the unmet needs of 10% to 15% of cystic fibrosis patients.

Going in a different and unique direction, Epicured is collaborating with Anagram Therapeutics following a successful dosing study focused on both cystic fibrosis and exocrine pancreatic insufficiency, highlighting a nutritional strategy to complement the genetic approaches in cystic fibrosis treatment.

Looking ahead, Sionna plans to select a lead candidate and conduct drug-drug interaction studies before launching a Phase IIa proof-of-concept trial later in 2025.

With Rare Disease Day 2025 fast approaching on February 28, these innovative pipelines offer renewed hope for patients battling cystic fibrosis.