The U.S. Food and Drug Administration has accepted and granted Priority Review to a Biologics License Application for ifinatamab deruxtecan (I-DXd) for treating adult patients with extensive-stage small cell lung cancer who experienced disease progression on or after platinum-based chemotherapy, according to statements from Daiichi Sankyo and Merck (NYSE: MRK).

The FDA action date under the Prescription Drug User Fee Act is set for October 10, 2026. The application is also being reviewed under the Real-Time Oncology Review program and Project Orbis, initiatives designed to expedite safe and effective cancer treatments.

Ifinatamab deruxtecan is an investigational B7-H3 directed antibody drug conjugate discovered by Daiichi Sankyo and jointly developed with Merck. If approved, it would be the first medicine in its class for these patients.

The application is based on results from the IDeate-Lung01 phase 2 trial, supported by data from the IDeate-PanTumor01 phase 1/2 trial. The IDeate-Lung01 study enrolled 187 patients in Asia, Europe and North America with extensive-stage small cell lung cancer previously treated with at least one prior line of platinum-based chemotherapy.

The FDA previously granted Breakthrough Therapy Designation to ifinatamab deruxtecan in August 2025 for the same indication. The drug has also received Orphan Drug Designation from multiple regulatory authorities for small cell lung cancer treatment.

Small cell lung cancer accounts for approximately 12% of all lung cancer cases in the U.S., with about 27,000 new cases diagnosed in 2025. The disease is aggressive and progresses rapidly to distant metastatic stages.