Atrium Therapeutics launched as a San Diego‑based spinout taking on preclinical cardiac RNA programs that were not included in Novartis’s acquisition of Avidity Biosciences. The new company assumed Avidity’s public listing and roughly $270 million in cash to advance targeted RNA medicines for rare cardiomyopathies, including PRKAG2 syndrome and PLN cardiomyopathy. Atrium is led by former Avidity executives Kathleen Gallagher and Sarah Boyce and will focus on advancing two preclinical candidates toward IND‑enabling studies. The move underscores how large acquisitions can seed secondary startups to pursue niche indications excluded from the buyer’s core strategy.