The US FDA granted priority review to Daiichi Sankyo and Merck’s B7-H3-directed antibody-drug conjugate ifinatamab deruxtecan. The decision applies to the BLA for patients with advanced extensive-stage small-cell lung cancer. If approved, the ADC would add another mechanism to a difficult-to-treat setting where treatment options remain limited, and it underscores continued regulatory emphasis on next-generation targeted cytotoxic delivery in SCLC. Priority review can shorten the review timeline, making the decision a near-term catalyst for development and competitive positioning across solid-tumor ADC pipelines.