Recent regulatory developments include the FDA restricting use of bluebird bio's Skysona gene therapy due to increased cancer risk, denial of Stealth BioTherapeutics’ reconsideration request for an ultrarare disease drug, and approval of Boehringer Ingelheim's pill targeting HER2-mutated lung cancer. Additionally, Sanofi’s monoclonal antibody SAR446523 received orphan drug designation for multiple myeloma, and Jazz Pharmaceuticals gained FDA approval for the first therapy treating recurrent H3 K27M-mutant diffuse midline glioma in children. These regulatory actions underscore ongoing challenges and progress in rare diseases and oncology therapeutics.