Daiichi Sankyo and Merck’s Biologics License Application (BLA) for ifinatamab deruxtecan (I-DXd) has been accepted and granted Priority Review by the US Food and Drug Administration (FDA) for the treatment of adult patients with extensive-stage Small Cell Lung Cancer (ES-SCLC) with disease progression on, or after platinum-based chemotherapy. The Prescription Drug User Fee Act (PDUFA) date, the FDA action date for its regulatory decision, is October 10, 2026.

Ifinatamab deruxtecan is a specifically engineered, potential first-in-class B7-H3 directed DXd Antibody Drug Conjugate (ADC) discovered by Daiichi Sankyo and being jointly developed by Daiichi Sankyo and Merck.

The FDA is also reviewing the BLA under the Real-Time Oncology Review (RTOR) program and Project Orbis, two initiatives of the FDA which are designed to bring safe and effective cancer treatments to patients as early as possible. RTOR allows the FDA to review components of an application before submission of the complete application. Project Orbis provides a framework for concurrent submission and review of oncology medicines among participating international partners.

The BLA is based on results from the IDeate-Lung01 Phase 2 trial, with support from the IDeate-PanTumor01 Phase 1/2 trial. Results from the primary analysis of IDeate-Lung01 were presented at the 2025 World Conference on Lung Cancer hosted by the International Association for the Study of Lung Cancer (#WCLC25) and published in the Journal of Clinical Oncology.

 “The FDA’s granting of Priority Review for ifinatamab deruxtecan marks a significant milestone in our effort to provide new and innovative treatment options for patients with extensive-stage Small Cell Lung Cancer,” said John Tsai, MD, Global Head—R&D, Daiichi Sankyo. “We look forward to continuing to work with the FDA to bring this potential first-in-class B7-H3 directed DXd antibody drug conjugate to patients as quickly as possible.”

Ifinatamab deruxtecan also was previously granted Breakthrough Therapy Designation (BTD) by the FDA in August 2025 for the treatment of adult patients with ES-SCLC with disease progression on, or after platinum-based chemotherapy.

“Small Cell Lung Cancer remains one of the toughest cancers to treat, with few options if the disease progresses after standard of care treatments,” said Eliav Barr, MD, Senior Vice President, Head—Global Clinical Development and Chief Medical Officer, Merck Research Laboratories. “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.”