The FDA accepted and granted priority review to Daiichi Sankyo and Merck’s B7-H3-directed ADC ifinatamab deruxtecan. The application seeks approval for patients with advanced extensive-stage small-cell lung cancer, placing the program on an accelerated regulatory path. Priority review shortens the review timeline and signals early alignment on the potential clinical value of the therapy in a high-need oncology segment. The ADC approach leverages a targeted antibody delivery mechanism designed to bring a cytotoxic payload to B7-H3-expressing tumors. The regulatory update is a near-term pipeline catalyst for both companies and highlights how B7-H3 remains an active target area for next-generation antibody-drug conjugates. It also increases competition pressure among ADC and immunotherapy strategies in small-cell lung cancer.