Atrium Therapeutics launched as a spinout carrying preclinical RNA programs for rare cardiac diseases that were not part of Novartis’ acquisition of Avidity Biosciences. The new company assumed Avidity’s public listing, leadership (including former Avidity executives), and roughly $270 million in starting cash. Atrium’s initial pipeline targets PRKAG2 syndrome and PLN cardiomyopathy and plans preclinical to IND work. Atrium builds on Avidity’s muscle‑targeted RNA delivery platform but pivots to heart muscle as the target tissue. Investors and partners will assess whether Atrium can translate delivery advances into cardio‑focused milestones and whether its capital base supports IND‑enabling programs.