Merck MRK and its Japanese partner Daiichi Sankyo announced that the FDA has accepted the biologics license application (BLA) seeking approval for ifinatamab deruxtecan (I-DXd), a B7-H3-directed DXd antibody-drug conjugate (ADC), for treating adult patients with extensive-stage small cell lung cancer (ES-SCLC) whose disease progressed on or after platinum-based chemotherapy.
With the FDA granting a priority review to the BLA, a decision from the regulatory body is expected on Oct. 10, 2026. This status is given to treatments that the FDA believes could significantly improve existing treatment options compared with standard applications.
If approved, I-DXd would become the first-in-class B7-H3-directed DXd ADC for the given patient population.
The FDA is also reviewing the BLA under its Real-Time Oncology Review and Project Orbis initiatives, which aim to speed up access to safe and effective cancer treatments for patients.
The BLA for I-DXd in ES-SCLC was based on data from the phase II IDeate-Lung01 study with support from the phase I/II IDeate-PanTumor01 study.
Year to date, shares of Merck have rallied 14.1% against the industry’s decrease of 2.4%.
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MRK & Daiichi's Deal for I-DXd & Other ADC Candidates
Besides ES-SCLC, I-DXd is being evaluated in separate phase III studies for treating esophageal cancer and prostate cancer. It is also being evaluated in various mid-stage studies for treating certain other types of cancer.
Developed by Daiichi Sankyo, I-DXd already enjoys an orphan drug designation for treating small-cell lung cancer in the United States, Europe and some other countries. Last August, the FDA granted a Breakthrough Therapy designation to I-DXd for treating ES-SCLC in adult patients whose disease progressed on or after platinum-based chemotherapy.
Merck acquired global co-development and co-commercialization rights to I-DXd and two other ADCs, patritumab deruxtecan and raludotatug deruxtecan, from Daiichi Sankyo in October 2023 for a total potential consideration of up to $22 billion. However, Daiichi Sankyo has retained exclusive rights for the development of the candidates in Japan.
In August 2024, Merck expanded the collaboration to co-develop and co-commercialize MK-6070, an investigational T-cell engager targeting delta-like ligand 3 (DLL3), which it obtained from its recent acquisition of Harpoon Therapeutics.
Patritumab deruxtecan is being developed in late-stage studies for breast cancer, while raludotatug deruxtecan is being developed in mid-stage studies for ovarian cancer as well as other cancer indications.
MRK’s Competition in the ADC Space
ADCs are being considered a disruptive innovation in the pharmaceutical industry, as these will enable better treatment of cancer by harnessing the targeting power of antibodies to deliver cytotoxic molecule drugs to tumors.
Daiichi Sankyo has several ADCs in clinical development across multiple types of cancer. It markets Enhertu, a HER2-directed ADC, in partnership with AstraZeneca AZN, which is presently approved across multiple indications, including HER2-mutated breast, lung and gastric cancers.
The FDA has also approved AZN and Daiichi’s second ADC drug, Datroway, for treating unresectable or metastatic HR-positive, HER2-negative breast cancer as well as EGFR-mutated non-small-cell lung cancer.
Pfizer PFE also forayed into the lucrative ADC space with the acquisition of Seagen for $43 billion in late 2023.
Following this acquisition, PFE added four ADCs to its portfolio — Adcetris, Padcev, Tukysa and Tivdak — all approved across various types of solid tumors and hematologic malignancies. These products contributed meaningfully to Pfizer’s revenues in 2025.
MRK’s Zacks Rank
Merck currently carries a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here.
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This article originally published on Zacks Investment Research (zacks.com).