The FDA accepted and granted priority review to Daiichi Sankyo and Merck’s ifinatamab deruxtecan for advanced extensive-stage small-cell lung cancer. The drug is a B7-H3-directed antibody-drug conjugate (ADC), moving faster through the review process than standard pathways. Priority review signals the agency expects a potential clinical impact in a disease area where treatment options remain limited. A decision timeline under the priority review program will follow the BLA acceptance. For competitors and ADC developers, the filing highlights the continuing bet on B7-H3 as an actionable tumor antigen in solid tumors and the ongoing expansion of ADC formats beyond first-line settings.