Company Announcements

Spinoff from Novartis AG's acquisition of Avidity Biosciences advances precision cardiology programs using targeted RNA delivery platform

Lead candidates ATR 1072 and ATR 1086 expected to enter clinical trials for PRKAG2 syndrome and PLN cardiomyopathy, respectively

SAN DIEGO , Feb. 27, 2026 /PRNewswire/ -- Atrium Therapeutics, Inc. (Nasdaq: RNA) launched today as a newly independent, publicly traded company dedicated to delivering RNA therapeutics directly to the heart to transform care for people living with rare, life-threatening genetic cardiomyopathies. Atrium Therapeutics was established in connection with Avidity Biosciences, Inc.'s acquisition by Novartis AG. The company is led by Kathleen Gallagher, President and Chief Executive Officer (CEO), and begins operations with two precision cardiology candidates, two undisclosed research targets and approximately $270 million in cash and cash equivalents.

Atrium Therapeutics' two lead development candidates are: ATR 1072 for PRKAG2 (Protein Kinase AMP-activated non-catalytic subunit Gamma 2) syndrome and ATR 1086 for PLN (phospholamban) cardiomyopathy. Both conditions are severe, life-threatening, rare autosomal dominant progressive cardiomyopathies with no approved therapies to treat the underlying cause of disease.

"The launch of Atrium Therapeutics marks an important milestone for people living with genetic cardiomyopathies," said Kathleen Gallagher, President and CEO of Atrium Therapeutics. "Patients and families facing these genetically driven rare cardiomyopathies have few if any options that address the underlying cause. Building on Avidity's pioneering work in targeted RNA delivery, Atrium is positioned to advance precision medicines designed to directly target the biologic drivers of cardiac disease. Atrium has the opportunity to help pave the way for a new era for RNA therapies in precision cardiology."

"As Atrium Therapeutics embarks on a new chapter today, I am incredibly proud of the team's commitment to advancing groundbreaking science for people with genetically driven cardiomyopathies," said Sarah Boyce, Chair of Atrium Therapeutics' board of directors and former CEO of Avidity. "Precision cardiology is an area of immense opportunity, and I am confident the Atrium Therapeutics team's experiences in rare disease, drug development and RNA therapeutics and patient-focused approach will urgently move its pipeline forward."

Pipeline and Development Milestones

• ATR 1072 (PRKAG2 syndrome): Investigational New Drug (IND)-enabling studies and CMC manufacturing underway. Atrium expects to file an IND in the second half of 2026.
• ATR 1086 (PLN cardiomyopathy): Chemistry Manufacturing and Controls (CMC) manufacturing planned to support initiation of IND-enabling preclinical studies in 2026, targeting an IND submission in 2027.

Pending supportive Phase 1 trial results, Atrium Therapeutics anticipates advancing both programs into clinical trials, while continuing to expand its additional precision cardiology pipeline and develop its next-generation RNA delivery platform.

About Atrium Therapeutics

Atrium Therapeutics, Inc. (Nasdaq: RNA) is pioneering targeted delivery of ribonucleic acid (RNA) therapeutics to the heart to transform the standard of care for people living with cardiomyopathies. The company's proprietary technology - designed at Avidity Biosciences, Inc. - combines the tissue selectivity of monoclonal antibodies (mAbs) and other targeted delivery ligands with the precision of oligonucleotides. Atrium Therapeutics' platform is designed to selectively target the underlying drivers of genetically driven cardiac diseases through targeted, non-viral delivery of small interfering RNA (siRNA). This approach builds upon learnings from delivery to the skeletal muscle and applies it for efficient delivery to the heart overcoming challenges associated with non-specific tissue delivery. The company's pipeline consists of two precision cardiology candidates, ATR 1072 and ATR 1086, and two undisclosed research targets in rare cardiomyopathies.

For more information about our RNA delivery platform, development pipeline and people, please visit https://atriumtherapeutics.com/ and engage with us on LinkedIn.

About PRKAG2 Syndrome

PRKAG2 syndrome is a rare, autosomal dominant, early-onset cardiomyopathy caused by mutations in the PRKAG2 gene, which encodes the Gamma 2 regulatory subunit of AMPK. Mutations enhance AMPK activity leading to abnormal glycogen accumulation in heart muscle cells leading to thickened heart muscles, electrical conduction problems, and arrhythmias. There are 1,000 – 2,000 people with PRKAG2 syndrome in the US. Current management is limited to symptomatic treatment; no approved therapies exist to address the underlying genetic driver of disease.

About PLN Cardiomyopathy

PLN (phospholamban) cardiomyopathy is a rare autosomal dominant, progressive cardiac disease caused by mutations in PLN, a key regulator of SERCA2a calcium pump. Pathogenic variants produce protein aggregates that disrupt endoplasmic reticulum processes and lead to dilated, arrhythmogenic, or hypertrophic cardiomyopathies and a significantly increased risk of heart failure and sudden cardiac death. There are 2,000 – 4,000 people with pathogenic PLN variants in the US. No approved therapies target the underlying molecular cause of the disease.

Forward-Looking Statements

This communication contains forward-looking statements within the meaning of the United States Private Securities Litigation Reform Act of 1995. Forward-looking statements can generally be identified by words such as "potential," "can," "will," "plan," "may," "could," "would," "expect," "anticipate," "look forward," "believe," "committed," "investigational," "pipeline," "launch," or similar terms, or by express or implied discussions regarding Atrium Therapeutics' future results of operations and financial condition; research and development plans; anticipated timing, design and conduct of ongoing and planned preclinical studies and clinical trials for product candidates; the timing and likelihood of regulatory filings and approvals for product candidates; the potential safety and therapeutic benefits of our product candidates; the timing and likelihood of success; plans and objectives of management for future operations; and future results of anticipated product development efforts. You should not place undue reliance on these statements. Such forward-looking statements are based on our current beliefs and expectations regarding future events, and are subject to significant known and unknown risks and uncertainties. Particular areas where risks or uncertainties could cause Atrium Therapeutics' actual results to be materially different than those expressed in Atrium Therapeutics' forward-looking statements include but are not limited to: the initiation, timing, progress, potential registrational quality, and results of our research and development programs, preclinical studies, any clinical trials, and other regulatory submissions; the beneficial characteristics, including potential safety, efficacy and therapeutic effects of our product candidates and the potential advantages of our product candidates compared to alternative therapies; the success and capabilities of the RNA delivery platform; the prevalence of certain diseases and conditions we intend to treat and our estimates of the potential market opportunity for our product candidates; the timing of and costs involved in obtaining and maintaining regulatory approval of our current product candidates and any future product candidates that we may identify or develop; our ability to develop our current and future product candidates; the implementation of our strategic plans for our business, product candidates, research programs and technologies; anticipated developments related to our competitors and our industry; our competitive position and the success of competing therapies that are or may become available; our ability to maintain our current license agreements and collaborations and identify and enter into future license agreements and collaborations; the expected potential benefits of strategic collaborations with third parties and our ability to attract collaborators with development, regulatory, manufacturing or commercialization expertise; our reliance on third parties to conduct preclinical studies and clinical trials of our product candidates; our ability to efficiently and cost-effectively conduct our current and future clinical trials; our reliance on third parties for the manufacture of our product candidates; the costs of operating as a public company; the accuracy of our estimates regarding future expenses, future revenue, capital requirements and the need for additional financing; the period over which we estimate our existing cash and cash equivalents will be sufficient to fund our future operating expenses and capital expenditure requirements; and other factors specified in Atrium Therapeutics' Registration Statement on Form 10, initially publicly filed by Atrium Therapeutics with the Securities and Exchange Commission (the "SEC") on December 10, 2025 and in other filings and furnishings made by Atrium Therapeutics with the SEC from time to time. Atrium Therapeutics is providing the information in this communication as of this date and does not undertake any obligation to update any forward-looking statements contained in this communication as a result of new information, future events or otherwise, except to the extent required by law.

Investor and Media Contact:

Stephanie Kenney, Chief Corporate Affairs Officer
investors@atrium-tx.com

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SOURCE Atrium Therapeutics