The FDA imposed a partial hold on Daiichi Sankyo and Merck’s global Phase 3 program for their investigational antibody‑drug conjugate (ADC) after companies paused enrollment citing a “higher‑than‑anticipated incidence” of deaths. Sponsors initiated safety reviews and regulators have restricted new enrollments while investigations continue. The move affects an ADC program being tested in lung cancer and follows internal pauses across sites; companies are cooperating with health authorities and assessing adverse event causality. The hold will determine whether and how trials restart and could influence labeling, risk‑mitigation strategies and ongoing development timelines. Biotech and oncology teams will watch adjudication details, dose modifications and any follow‑on toxicology or mechanistic findings that explain mortality signals in ADC programs.