FDA Grants Priority Review to Lung Cancer Drug Candidate

Daiichi Sankyo and Merck & Co. (known as MSD outside the United States and Canada) have announced that the U.S. Food and Drug Administration has accepted and granted Priority Review for their Biologics License Application (BLA) for ifinatamab deruxtecan (I-DXd), a potential new treatment for extensive-stage small cell lung cancer (ES-SCLC).

The regulatory milestone marks a significant step forward for the investigational therapy, which is being developed for adult patients whose disease has progressed during or after platinum-based chemotherapy. Small cell lung cancer remains one of the most aggressive and difficult-to-treat forms of cancer, particularly in advanced stages where treatment options are limited.

Ifinatamab deruxtecan is a specifically engineered antibody drug conjugate (ADC) targeting B7-H3, designed to deliver chemotherapy directly to cancer cells while minimizing damage to healthy tissue. The drug candidate is considered a potential first-in-class therapy and was originally discovered by Daiichi Sankyo, with joint development efforts underway alongside Merck.

The U.S. Food and Drug Administration grants Priority Review to medicines that may provide significant improvements in safety or effectiveness compared to existing treatments, or that address serious conditions with unmet medical needs. In addition to Priority Review status, the application is being evaluated under the FDA’s Real-Time Oncology Review (RTOR) program and Project Orbis. These initiatives aim to accelerate the availability of promising cancer therapies by enabling earlier data review and coordinated international regulatory collaboration.

The FDA has set a target decision date under the Prescription Drug User Fee Act (PDUFA) for October 10, 2026.

The BLA submission is supported by clinical data from the phase 2 IDeate-Lung01 trial, with additional evidence from the phase 1/2 IDeate-PanTumor01 study. Findings from the primary analysis of IDeate-Lung01 were presented at the World Conference on Lung Cancer 2025 and published in the Journal of Clinical Oncology, underscoring the scientific interest in the therapy.

Notably, ifinatamab deruxtecan previously received Breakthrough Therapy Designation from the FDA in August 2025, further highlighting its potential to address a critical gap in cancer care.

John Tsai described the Priority Review as a major milestone in delivering innovative treatments to patients with ES-SCLC, emphasizing the company’s commitment to working closely with regulators to expedite access. Meanwhile, Eliav Barr noted the urgent need for new options in small cell lung cancer, particularly for patients who do not respond to standard therapies.

If approved, ifinatamab deruxtecan could represent a meaningful advancement in the treatment landscape for one of the most challenging forms of lung cancer, offering renewed hope for patients with limited alternatives.