The FDA granted priority review to Daiichi Sankyo and Merck’s B7-H3-directed antibody-drug conjugate ifinatamab deruxtecan, supported by a BLA submission for extensive-stage small-cell lung cancer. The action places the program on an accelerated regulatory track tied to the review timeline. Ifinatamab deruxtecan is designed to deliver a cytotoxic payload selectively to B7-H3-expressing tumors, a target that has been actively pursued in solid tumors. Priority review signals that regulators have accepted the application for an expedited assessment process. For developers and investors, priority review often serves as a near-term catalyst for trial readouts, post-marketing planning and competitive dynamics in ADC space—especially in disease areas with limited effective options.