Merck and Daiichi Sankyo withdraw ifinatamab deruxtecan BLA

A U.S. accelerated approval application for a small cell lung cancer drug was withdrawn Friday as Merck & Co., Inc. NYSEMRK and Daiichi Sankyo TYO4568 said its evidence did not meet the FDA's requirements. The application had an Oct. 10, 2026 action date after the agency granted it priority review in April.

The biologics licence application sought treatment of adults whose extensive-stage small cell lung cancer progressed on or after platinum-based chemotherapy. The partners said their discussions with the U.S. Food and Drug Administration showed the supporting data, including from Phase 2 IDeate-Lung01, did not satisfy the requirements for accelerated approval of that indication.

Merck and Daiichi Sankyo are large U.S. and Japanese drugmakers jointly developing Daiichi's B7-H3-directed antibody drug conjugate, ifinatamab deruxtecan, across several cancers. The companies continue to enroll patients in a randomized Phase 3 lung cancer trial and said that trial is nearing full enrollment.

The Sept. 25 company release went out at 4:30 p.m. EDT, after regular U.S. trading. No verified post-announcement Merck share reaction was available at filing. The companies gave no Phase 3 readout date in Friday's release.

Phase 2 Interim Data Measured Tumour Response

The companies said in the Sept. 25 release that IDeate-Lung01 enrolled 187 patients across Asia, Europe and North America. Its dose-optimization stage randomized patients between two doses of ifinatamab deruxtecan, followed by a single-dose expansion stage. The trial's primary endpoint was objective response rate by blinded independent central review, and it did not include a chemotherapy control arm.

The interim analysis published Sept. 7, 2024 reported a 54.8 per cent response rate among 42 patients receiving the selected higher dose. The lower-dose group had a 26.1 per cent response rate among 46 patients. Those figures describe a dose study, while the priority-review application later rested on the trial's primary analysis and a separate early-stage study.

The older dataset also recorded grade 3 or higher treatment-emergent adverse events in 50.0 per cent of higher-dose recipients as of April 25, 2024. The lower-dose group included one treatment-related fatal case of interstitial lung disease. The Sept. 25 release did not identify a particular safety finding as the reason for withdrawal.

Read more: Gossamer Bio submits seralutinib NDA after Phase 3 endpoint miss

IDeate-Lung02 instead compares ifinatamab deruxtecan with physicians' choice of amrubicin, lurbinectedin or topotecan after one previous line of platinum chemotherapy. The company release says enrollment is near completion, but gives neither a data-readout date nor a new filing timetable.

"Enrollment into the IDeate-Lung02 Phase 3 trial is near completion and we look forward to assessing the potential for a future filing of ifinatamab deruxtecan with the FDA and other global regulatory authorities based on those results," Daiichi Sankyo's head of therapeutic area oncology development Abderrahmane Laadem said in the Sept. 25 release.

Merck and Daiichi Sankyo are also studying the drug in Phase 3 trials for prostate and esophageal cancers, according to the same release.

Read more: aTyr Pharma says FDA aligned on 372-patient sarcoidosis trial

Amgen Has a Full Approval in the Same Setting

Amgen Inc. NASDAQAMGN said in a Nov. 19, 2025 release that the FDA granted full approval to its Imdelltra treatment for adults with extensive-stage small cell lung cancer after progression on or after platinum chemotherapy. Its randomized Phase 3 trial showed median overall survival of 13.6 months, compared with 8.3 months for chemotherapy. Imdelltra targets DLL3, while ifinatamab deruxtecan targets B7-H3.

Oct. 10 was the FDA action date for the withdrawn application. The partners said they look forward to assessing the potential for a future U.S. filing based on IDeate-Lung02 results; their Sept. 25 release gave no readout date.