Merck (NYSE: MRK) and Daiichi Sankyo have voluntarily withdrawn a Biologics License Application (BLA) seeking accelerated U.S. approval for ifinatamab deruxtecan (I-DXd) in adult patients with extensive-stage small cell lung cancer (ES-SCLC) whose disease progressed on or after platinum-based chemotherapy.

The withdrawal followed discussions with the U.S. Food and Drug Administration, which indicated that data from the IDeate-Lung01 Phase 2 trial and other supporting data did not meet the requirements for accelerated approval of the proposed indication.

Patient enrollment continues in the IDeate-Lung02 Phase 3 trial, which is evaluating ifinatamab deruxtecan against physician's choice of chemotherapy — amrubicin, lurbinectedin, or topotecan — in patients with relapsed ES-SCLC following progression on one prior line of platinum-based chemotherapy. Enrollment in that trial is described as near completion.

"While we are disappointed that the current dataset are not supportive of an approval at this time, we are continuing to evaluate the role of ifinatamab deruxtecan in patients with extensive-stage small cell lung cancer and other types of difficult-to-treat cancer," said Marjorie Green, MD, senior vice president and head of oncology, global clinical development, Merck Research Laboratories.

Two additional Phase 3 trials are underway for ifinatamab deruxtecan: IDeate-Prostate01 for castration-resistant prostate cancer and IDeate-Esophageal01 for esophageal squamous cell carcinoma.

Ifinatamab deruxtecan has received orphan drug designation from the FDA, European Commission, Japan's Ministry of Health, Labor and Welfare, and Taiwan's Food and Drug Administration for the treatment of SCLC. The FDA also granted orphan drug designation for esophageal cancer.

Daiichi Sankyo and Merck entered their global collaboration to jointly develop and commercialize ifinatamab deruxtecan in October 2023.