Daiichi Sankyo And Merck Receive Priority Review For Ifinatamab Deruxtecan In Previously Treated Extensive-Stage Small Cell Lung Cancer

Daiichi Sankyo and Merck?s Biologics License Application for ifinatamab deruxtecan (I-DXd) has been accepted and granted Priority Review by the U.S. Food and Drug Administration 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 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 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. 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.

Ifinatamab deruxtecan also was previously granted Breakthrough Therapy Designation by the FDA in August 2025 for the treatment of adult patients with ES-SCLC with disease progression on or after platinum-based chemotherapy. IDeate-Lung01 is a global, multicenter, randomized, open-label, two-part Phase 2 trial evaluating the safety and efficacy of ifinatamab deruxtecan in patients with ES-SCLC who were previously treated with at least one prior line of platinum-based chemotherapy and a maximum of three prior lines of therapy. Patients with asymptomatic brain metastases (untreated or previously treated) were eligible to participate.

In the first part of the trial (dose optimization), patients were randomized 1:1 to receive ifinatamab deruxtecan (8 or 12 mg/kg) given intravenously once every three weeks. In the second part of the trial (dose expansion), patients received ifinatamab deruxtecan (12 mg/kg) intravenously at the same dosing interval. The primary endpoint is objective response rate as assessed by blinded independent central review per RECIST v1.1. Secondary endpoints included duration of response, progression-free survival, disease control rate, time to response, overall survival, pharmacokinetics and safety.

Intracranial objective response rate was assessed by blinded independent central review as an exploratory analysis. IDeate-Lung01 enrolled 187 patients in Asia, Europe and North America. IDeate-PanTumor01 is a global, multicenter, first-in-human, open-label Phase 1/2 trial evaluating the safety and efficacy of ifinatamab deruxtecan in patients with advanced/unresectable or metastatic solid tumors that are refractory or intolerable to standard treatment or for whom no standard treatment exists.

The Phase 1 part of the trial (dose escalation) is assessing the safety and tolerability of increasing doses of ifinatamab deruxtecan to determine the maximum tolerated dose and recommended dose for expansion. The Phase 2 part of the trial (dose expansion) is evaluating the safety and efficacy of ifinatamab deruxtecan at the recommended dose for expansion of 12 mg/kg in patients with squamous non-small cell lung cancer, metastatic castration-resistant prostate cancer or esophageal squamous cell carcinoma. The dose escalation part of the trial is evaluating dose-limiting toxicity and safety.

The dose expansion part of the trial is evaluating objective response rate, duration of response, disease control rate, progression-free survival, overall survival and safety. Pharmacokinetic endpoints, exploratory biomarker and immunogenicity endpoints also will be assessed. IDeate-PanTumor01 will enroll approximately 250 patients in Asia and North America.

Approximately 250,000 patients are diagnosed with small cell lung cancer each year globally. There are currently no B7-H3 directed medicines approved for the treatment of cancer. Ifinatamab deruxtecan is an investigational potential first-in-class B7-H3 directed ADC.

Designed using Daiichi Sankyo?s proprietary DXd ADC Technology, ifinatamab deruxtecan is comprised of a humanized anti-B7-H3 IgG1 monoclonal antibody attached to a number of topoisomerase I inhibitor payloads (an exatecan derivative, DXd) via tetrapeptide-based cleavable linkers. Ifinatamab deruxtecan was granted Breakthrough Therapy Designation by the FDA for the treatment of adult patients with extensive-stage small cell lung cancer with disease progression on or after platinum-based chemotherapy. The program is currently comprised of three Phase 3 trials in advanced/metastatic disease, including small cell lung cancer (IDeate-Lung02), castration-resistant prostate cancer (IDeate-Prostate01) and esophageal squamous cell carcinoma (IDeate-Esophageal01).

Daiichi Sankyo and Merck entered into a global collaboration in October 2023 to jointly develop and commercialize ifinatamab deruxtecan (I-DXd), raludotatug deruxtecan (R-DXd) and patritumab deruxtecan (HER3-DXd), except in Japan where Daiichi Sankyo will maintain exclusive rights. Daiichi Sankyo will be solely responsible for manufacturing and supply. The Daiichi Sankyo ADC portfolio consists of eight ADCs in clinical development crafted from ADC technology discovered in-house by Daiichi Sankyo.

The DXd ADC Technology platform of Daiichi Sankyo consists of seven ADCs in clinical development where each ADC is comprised of a monoclonal antibody attached to a number of topoisomerase I inhibitor payloads (an exatecan derivative, DXd) via tetrapeptide-based cleavable linkers. The DXd ADCs include ENHERTU and DATROWAY, which are being jointly developed and commercialized globally with AstraZeneca, and ifinatamab deruxtecan (I-DXd), raludotatug deruxtecan (R-DXd) and patritumab deruxtecan (HER3-DXd), which are being jointly developed and commercialized globally with Merck. DS-3939 and DS3790 are being developed by Daiichi Sankyo.

An additional ADC being developed by Daiichi Sankyo is DS3610, which consists of an antibody attached to a novel payload that acts as an agonist of STING. Ifinatamab deruxtecan, raludotatug deruxtecan, patritumab deruxtecan, DS-3939, DS3610 and DS3790 are investigational medicines that have not been approved for any indication in any country. Safety and efficacy have not been established.