Merck and Daiichi Sankyo withdrew their FDA biologics license application for ifinatamab deruxtecan (i-dxd), removing the path they sought for accelerated approval in extensive-stage small cell lung cancer. The companies said the withdrawal occurred voluntarily two weeks before the PDUFA date for the B7-H3-directed ADC, following FDA feedback that the data generated so far would not support accelerated clearance. The decision further reshapes the competitive landscape in SCLC, where multiple ADC and immunotherapy approaches are vying for incremental benefit. The setback also narrows Merck’s near-term regulatory momentum tied to its Prometheus acquisition thesis, even as the company continues to advance other pipeline assets. The withdrawal leaves Merck and Daiichi with a narrower regulatory calendar footprint for October and signals that additional trial data or alternative endpoints may be required for this target-treatment strategy.