Daiichi Sankyo and Merck Withdraw Ifinatamab Deruxtecan BLA Due to Insufficient Data

Daiichi Sankyo and Merck have withdrawn their Biologics License Application (BLA) for ifinatamab deruxtecan in extensive-stage small cell lung cancer (ES-SCLC), citing insufficient Phase II data to support accelerated approval.

The US FDA had granted Breakthrough Therapy Designation for the ES-SCLC indication in August 2025, followed by Priority Review in April 2026. However, after discussions with the agency concluded that the available data were not sufficient, the companies decided to withdraw the application.

Ifinatamab deruxtecan is a B7-H3-directed antibody-drug conjugate (ADC) being developed for various cancer types, including SCLC. The setback comes as competition intensifies in B7-H3-targeted ADCs, with Hansoh Pharmaceutical and GSK's risvutatug rezetecan recently reporting positive Phase III survival data in relapsed SCLC in China.

The withdrawal marks another regulatory setback for the Daiichi Sankyo-Merck ADC alliance, which had previously withdrawn the US BLA for patritumab deruxtecan in previously treated EGFR-mutated non-small cell lung cancer after a failed Phase III trial. Ifinatamab deruxtecan remains active in Phase III development, with enrollment nearing completion.