Sionna Therapeutics Reports Fourth Quarter and Full Year 2024 Financial Results

Phase 1 MAD dosing completed for SION-451 and final MAD cohort of SION-719 planned; Interim data in healthy volunteers show potential to provide clinically meaningful benefit to CF patients. Topline data anticipated in first half of 2025

On track to initiate NBD1 Phase 2a proof-of-concept trial in combination with SOC in CF patients and combination MAD trials of an NBD1 stabilizer with a complementary modulator in healthy volunteers in the second half of 2025, with topline data for both anticipated in mid-2026

Completed upsized IPO with gross proceeds of approximately $219 million, extending runway into 2028

WALTHAM, Mass., March 20, 2025 (GLOBE NEWSWIRE) -- Sionna Therapeutics, Inc. (Nasdaq: SION), a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis $(CF)$ by developing novel medicines that normalize the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, today reported financial results for the fourth quarter and full year ended December 31, 2024, and provided a business update.

"2024 was an excellent year for Sionna including strong clinical execution across multiple programs. Encouraging interim Phase 1 data for SION-719 and SION-451, our highly potent nucleotide-binding domain 1 (NBD1) stabilizers, showed that both candidates were generally well tolerated and achieved target exposures--reinforcing their potential to deliver meaningful clinical benefits for people with CF," said Mike Cloonan, President and Chief Executive Officer of Sionna. "Building on this momentum, we successfully completed an upsized IPO, a significant milestone that extends our cash runway into 2028 and provides financial and strategic flexibility. 2025 is off to a strong start with the consummation of the IPO and the progression of the Phase 1 single ascending dose (SAD) and multiple ascending dose $(MAD.AU)$ trials for SION-719 and SION-451. We look forward to announcing topline data in the first half of this year and initiating our Phase 2a proof-of-concept (POC) trial and the combination MAD Phase 1 program later this year."

Pipeline Updates

NBD1 Stabilizers

   -- Phase 1 MAD advancement: Sionna has completed dosing in the MAD part of 
      the Phase 1 healthy volunteer trial of SION-451 and the final MAD cohort 
      of SION-719 is planned. The additional completed cohorts since Sionna 
      reported interim Phase 1 data evaluated 225 mg and 25 mg (fed) of 
      SION-451 and 160 mg of SION-719, dosed twice daily $(BID.AU)$ over 10 days. 
      The final MAD cohort for SION-719 will evaluate 120 mg BID. All MAD data, 
      including from the recently completed cohorts, remain blinded to 
      individual subject treatment assignment. Both compounds were generally 
      well tolerated in these additional completed cohorts. There were no 
      serious adverse events (SAEs), and most treatment emergent adverse events 
      (TEAEs) were mild to moderate. There were no TEAEs related to liver 
      function tests and no TEAEs that led to discontinuation of trial drug. 
      Part C of both trials, in which Sionna is evaluating the effect of food 
      on the pharmacokinetics $(PK)$ of each product candidate and the 
      bioequivalence of a tablet formulation is ongoing. Topline data from both 
      trials are expected in the first half of 2025. 
 
   -- Encouraging Phase 1 Interim Data: Sionna previously reported encouraging 
      Phase 1 interim data from the completed SAD part and three cohorts of the 
      MAD part of each Phase 1 trial of SION-719 and SION-451 in healthy 
      subjects. As of the data cutoff date of January 14, 2025, both SION-719 
      and SION-451 were generally well tolerated at all administered dose 
      levels, achieving target exposures that have the potential, based on 
      Sionna's preclinical cystic fibrosis human bronchial epithelial (CFHBE) 
      model, to provide clinically meaningful benefit to patients if SION-719 
      or SION-451 were administered as part of a dual combination with one of 
      Sionna's complementary modulators or as an add-on to the current standard 
      of care $(SOC)$. 
 
   -- Phase 2a Proof-of-Concept Trial: Sionna plans to initiate a Phase 2a POC 
      trial in the second half of 2025, after completion of a drug-drug 
      interaction trial, to evaluate an NBD1 stabilizer in combination with the 
      current SOC in CF patients. Topline data from this trial are anticipated 
      in mid-2026. 
 
   -- Combination MAD Trials: Sionna plans to initiate combination MAD trials 
      in the second half of 2025, evaluating dual combinations of an NBD1 
      stabilizer with galifactor (SION-2222), a transmembrane domain 1 
      (TMD1)-directed CFTR corrector and/or SION-109, an intracellular loop 4 
      (ICL4)-directed CFTR corrector, in healthy subjects. Topline data are 
      expected in mid-2026. 

Complementary Modulators

   -- Successful Completion of Phase 1 Trial for SION-109: In December 2024, 
      Sionna completed a Phase 1 clinical trial of SION-109 in healthy 
      subjects. SION-109 was generally well tolerated at all dose levels 
      administered and its target exposure as part of a dual combination with 
      SION-451 or SION-719 was achieved with both single and multiple doses. 

Business Highlights

   -- Completion of Upsized IPO: In February 2025, Sionna completed its upsized 
      IPO, raising approximately $219 million gross proceeds before deducting 
      underwriting discounts and commissions and other expenses. Sionna issued 
      12,176,467 shares of its common stock at a public offering price of 
      $18.00 per share, which included 1,588,234 shares issued upon the full 
      exercise by the underwriters of their option to purchase additional 
      shares of common stock in the offering. Shares began trading on the 
      Nasdaq Global Market on February 7, 2025, under the symbol "SION." 
 
   -- Strengthened Leadership: Sionna enhanced its Board of Directors with the 
      appointments of Laurie Stelzer, Marcella Kuhlman Ruddy, M.D., and Jo 
      Viney, Ph.D., who collectively bring decades of leadership experience in 
      the biopharmaceutical industry, further supporting Sionna's strategic 
      growth and innovation. 

Financial Results for the Quarter and Year Ended December 31, 2024

Research and Development Expenses: Research and development expenses were $14.3 million for the fourth quarter of 2024 and $57.3 million for the year ended December 31, 2024, compared to $9.9 million and $40.6 million, respectively, for the same periods of 2023. These increases were mainly driven by direct program spend to support Sionna's clinical pipeline. In 2024, Sionna licensed three clinical-stage assets, galicaftor (SION-2222), navocaftor (SION-3067) and SION-2851, from AbbVie Global Enterprises LTD, which resulted in the recognition of in-process research and development expenses of $13.6 million, which consisted of a $5.0 million upfront payment and $8.6 million of non-cash expense.

General and Administrative Expenses: General and administrative expenses were $3.9 million for the fourth quarter of 2024 and $13.3 million for the year ended December 31, 2024, compared to $2.7 million and $9.7 million, respectively, for the same periods of 2023. The increase was primarily due to personnel-related costs, including stock-based compensation, and professional fees.

Net Loss: Net loss was $15.8 million for the fourth quarter of 2024 and $61.7 million for the year ended December 31, 2024, compared to a net loss of $11.9 million and $47.3 million, respectively, for the same periods of 2023.

Cash and Cash Equivalents: Cash, cash equivalents and marketable securities totaled $168.0 million as of December 31, 2024. This balance excludes net proceeds from our IPO of $199.6 million after deducting underwriting discounts and commissions and other offering costs. With the net IPO proceeds, Sionna expects its current cash position to fund operations into 2028.

About Sionna Therapeutics

Sionna Therapeutics is a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for CF by developing novel medicines that normalize the function of the CFTR protein. Sionna's goal is to deliver differentiated medicines for people living with CF that can restore their CFTR function to as close to normal as possible by directly stabilizing CFTR's nucleotide-binding domain 1 (NBD1), which Sionna believes is central to potentially unlocking dramatic improvements in clinical outcomes and quality of life for people with CF. Leveraging more than a decade of the co-founders' research on NBD1, Sionna is advancing a pipeline of small molecules engineered to correct the defects caused by the F508del genetic mutation, which resides in NBD1. Sionna is also developing a portfolio of complementary CFTR modulators that are designed to work synergistically with its NBD1 stabilizers to improve CFTR function. For more information about Sionna, visit www.sionnatx.com.

Sionna intends to use its Investor Relations website as a means of disclosing material nonpublic information and for complying with its disclosure obligations under Regulation FD. Accordingly, investors should monitor the Company's Investor Relations website, in addition to following the Company's press releases, SEC filings, public conference calls, presentations, and webcasts.

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