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Merck, Daiichi pull US application for second partnered cancer therapy

By Thomson Reuters Sep 25, 2026 | 3:38 PM

Sept 25 (Reuters) – Merck and Daiichi Sankyo have withdrawn their US application seeking accelerated approval for an experimental lung cancer therapy, the companies said on ​Friday, marking the second pullback under their ‌multibillion-dollar cancer alliance.

The decision followed discussions with the US Food and Drug Administration, which determined that the data from a mid-stage clinical study testing the therapy, ifinatamab deruxtecan, did not satisfy requirements needed ‌to ​support an early green light.

The therapy ⁠was under review to ⁠treat adults with an aggressive condition, known as extensive-stage small cell lung cancer, whose disease had worsened after standard chemotherapy.

Ifinatamab deruxtecan belongs to a class of ​targeted cancer therapies, called antibody-drug conjugates, which work like “guided missiles” by killing tumor cells while leaving healthy ones ⁠unharmed.

It is the second of ⁠the three “guided missile” therapies, co-developed by Merck ​and Daiichi under their 2023 partnership worth up to $22 billion, ​to face a US application withdrawal. Last year, the ‌companies pulled the application for another lung cancer candidate, patritumab deruxtecan, after it failed to extend the lives of patients in a late-stage study.

Ifinatamab deruxtecan, patritumab deruxtecan and ⁠a third therapy, raludotatug deruxtecan, are all part of the collaboration.

Despite the setback, the companies said they would continue evaluating ⁠ifinatamab deruxtecan. Patient ‌enrollment is nearly complete for a larger, ⁠late-stage trial comparing the therapy against other ​standard ‌chemotherapy options.

The companies plan to use the ​results from ⁠that study to seek approvals from the FDA and other global health regulators.

The therapy is also being evaluated in separate late-stage clinical trials for advanced prostate and esophageal cancers.

(Reporting by Kamal Choudhury in Bengaluru; Editing by Maju Samuel ​and Shilpi Majumdar)