The FDA granted priority review to Daiichi Sankyo and Merck’s ifinatamab deruxtecan B7-H3 antibody-drug conjugate. The agency’s decision applies to a BLA seeking treatment for patients with advanced extensive-stage small-cell lung cancer. Priority review signals a faster regulatory timeline for the submission’s evaluation, which can affect both label expectations and downstream payer access discussions if approval is granted. The B7-H3-directed ADC adds to a crowded antibody-drug conjugate market, where target selection and confirmatory benefit data are closely scrutinized. The priority review outcome will shape the near-term competitive landscape for ADCs in small-cell lung cancer as companies race to demonstrate meaningful clinical improvements.