Atrium Therapeutics launched as a spinout preserving Avidity Biosciences’ cardiac RNA programs after Novartis closed its $12 billion acquisition of Avidity. Led by former Avidity executives, Atrium starts with about $270 million in cash and two preclinical candidates targeting PRKAG2 syndrome and PLN cardiomyopathy, with both programs described as preclinical. Atrium’s founders cast the company as a continuation of Avidity’s delivery expertise for RNA therapeutics into heart muscle — an area historically challenging for nucleic acid drugs. Management framed the spinout as an opportunity to focus on rare, genetically driven cardiomyopathies that were not part of Novartis’ strategic purchase. The new company will aim to advance its lead candidates toward the clinic over the next two years, while monitoring potential partnering or financing paths to support later‑stage development.