Merck & Co (MSD) and Daiichi Sankyo have received priority review from the US Food and Drug Administration (FDA) for ifinatamab deruxtecan’s biologics licence application (BLA) to treat extensive-stage small cell lung cancer (ES-SCLC).
The treatment targets adult patients with ES-SCLC who have experienced disease progression on or after platinum-based chemotherapy.
The FDA has scheduled a decision date for 10 October 2026 under the Prescription Drug User Fee Act.
Ifinatamab deruxtecan is a specifically engineered B7-H3-directed DXd antibody drug conjugate (ADC), which was discovered by Daiichi Sankyo and is being co-developed with MSD.
The FDA priority review is granted to therapies that could offer substantial improvement over existing options, either through improved safety or efficacy, prevention of serious conditions, or enhanced patient compliance.
The regulator is also reviewing the BLA under its real-time oncology review (RTOR) programme and Project Orbis initiative.
RTOR permits a rolling review before formal application submission, and Project Orbis enables simultaneous submission and review of new therapies with participating international partners.
The BLA submission for ifinatamab deruxtecan draws on data from the IDeate-Lung01 Phase II trial, supported by findings from the IDeate-PanTumor01 Phase I/II trial.
Ifinatamab deruxtecan previously received breakthrough therapy designation from the FDA in August 2025 for adult ES-SCLC patients with disease progression after platinum-based chemotherapy.
Merck Research Laboratories senior vice-president, global clinical development head and chief medical officer Eliav Barr said: “Small cell lung cancer remains one of the toughest cancers to treat, with few options if the disease progresses after standard of care treatments.
“The FDA’s acceptance of the BLA reinforces the important role that ifinatamab deruxtecan could play in helping to address the needs of patients with extensive-stage small cell lung cancer.”
Earlier this month, MSD received the European Commission (EC) approval for Keytruda (pembrolizumab), along with paclitaxel, with or without bevacizumab, as a treatment for programmed death-ligand 1 (PD-L1)-positive ovarian cancer.
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