Atrium Therapeutics debuted as a spinout after Novartis closed its $12 billion acquisition of Avidity Biosciences. Led by former Avidity executives including Kathleen Gallagher and Sarah Boyce, Atrium picked up preclinical RNA programs targeting rare cardiac disorders and launched with about $270 million in cash. The company is developing RNA‑based therapies for PRKAG2 syndrome and PLN cardiomyopathy, with programs expected to enter IND‑enabling work over the next two years. Atrium’s leadership emphasized that these cardiac delivery programs were not part of the Novartis acquisition and will now receive focused development resources. Atrium’s formation illustrates a common post‑M&A outcome where acquirers retain core assets while new companies carry forward adjacent programs that buyers deemed nonstrategic.