B7-H3-Targeted Ifinatamab Deruxtecan Achieves a 48% Response Rate in Small Cell Lung Cancer
In this article
Conference: IASLC World Conference on Lung Cancer (WCLC25) · Date: September 6–9, 2025 · Location: Barcelona, Spain
Presentation: Phase 2 IDeate-Lung01 Trial primary analysis · Presenter: Prof. Myung-Ju Ahn, MD (Samsung Medical Center, Seoul)
⚡ Why Does It Matter?
Extensive-stage small cell lung cancer (ES-SCLC)is one of the most challenging cancers to treat because of early relapse and limited second-/third-line options.
Ifinatamab deruxtecan (I-DXd)is an antibody–drug conjugate (ADC) under development in this field that offers promise for physicians.
Developers: The drug was discovered by Japan-based Daiichi Sankyo and is being developed globally in collaboration with Merck (MSD) under a partnership for global development and commercialization.
Approval status: It is an investigational drug that has not yet been approved in any country; however, the US Food and Drug Administration (FDA) has granted it Breakthrough Therapy Designation and multiple authorities have granted Orphan Drug support .
Nevertheless, the high response rate, rapid onset of action and signal of lasting benefit in the I-DXd Phase 2 trial suggest that it could bring a new option to clinical practice.
Study Design
This study investigated a new drug (I-DXd) in patients who had previously received chemotherapy at least once and whose disease had progressed, with a diagnosis of small cell lung cancer (SCLC).
- How many people participated? A total of 137 patients.
- How was the drug given? Intravenously, every 3 weeks.
- Who was eligible? Patients with imaging-confirmed disease progression and at least 1 measurable tumor. Patients with controlled brain metastases were also eligible.
- What was measured? The drug’s ability to shrink tumors and its success in controlling disease were assessed; in addition, side effects were closely monitored.
📊 Study Results (Summary)
- Tumor shrinkage (ORR): Approximately 48% of patients experienced substantial shrinkage.
- Disease control (DCR): In 88% of patients, the disease remained at least under control.
- Onset of drug effect: The first benefit was observed after an average of 1.5 months .
- Duration of response: In those who responded to treatment, the response lasted an average of 5 months .
- Average progression-free period (PFS): 4.9 months.
- Average overall survival (OS): 10.3 months.
Note: These values are averages for the study population; each patient’s situation may differ. Treatment decisions must always be made together with your doctor.
📊 Comparative Summary (Extensive-Stage Small Cell Lung Cancer; ≥2nd Line)
Why Did We Make This Comparison?
Seeing approved and investigational options used in the same clinical setting side by side helps rapidly compare efficacy (ORR, PFS, OS) and safety signals and clarify I-DXd’s position . This summary is not the sole source for guiding treatment selection ; it is intended to support decisions with your physician, considering the patient’s clinical characteristics (age, ECOG, CTFI, brain/liver metastases, comorbidities) and access/center resources . Note: Between the studies there is no direct comparison ; the results are an indirect comparison.
| Treatment | Trial / Context | ORR | DCR | Median PFS | Median OS | Key Safety Findings |
|---|---|---|---|---|---|---|
| Ifinatamab Deruxtecan (I-DXd) | IDeate-Lung01 Phase 2 (n=137) | 48.2% | 87.6% | 4.9 months | 10.3 months | TRAE 89.8%; ≥G3 36.5%; ILD 12.4% (G5 1.5%) |
| Tarlatamab (DLL3 BiTE) | DeLLphi-301 Phase 2, DeLLphi-304 Phase 3 | ~40–45% | — | — | ~14.3 months | CRS and neuroimmune events; FDA accelerated approval (2024) |
| Lurbinectedin (Zepzelca) | Phase 2 basket, after platinum | 35.2% | — | 3.5 months | 9.3 months | Myelosuppression; FDA-approved (2020) |
| Topotecan | Conventional 2nd-line standard | ~15–22% (sensitive), ~5% (refractory) | — | 3–4 months | 6–8 months | Significant hematological toxicity |
| Amrubicin | Phase 3 (Japan) | 31% vs 17% | — | 4.1 vs 3.5 months | 7.5 vs 7.8 months | No OS difference; monitor for cardiotoxicity |
| Platinum Rechallenge | Retrospective; sensitive relapse (CTFI ≥90 days) | ~30–40% | — | 3–6 months | 8–10 months | May be recommended for patients with CTFI ≥90 days |
🔍 Brief Reading Notes
- I-DXd: High ORR/DCR, rapid and durable responses (TTR 1.4 months, DoR 5.3 months). ILD risk is important.
- Tarlatamab: First DLL3-targeted BiTE; OS ~14.3 months; CRS and immune events are common.
- Lurbinectedin: Single-agent ORR 35%, OS 9.3 months; myelosuppression is common.
- Topotecan: Limited efficacy; standard for symptom control.
- Amrubicin: ORR/PFS advantage, no OS difference; regional use.
- Platinum rechallenge: May be preferred in sensitive relapse; heterogeneous after modern treatments.
🧭 A Quick Decision Framework for Clinical Practice
- 📌 DLL3-positive with suitable center/monitoring resources: Tarlatamab (FDA-approved).
- 📌 If unsuitable for immunotherapy: Lurbinectedin (approved, extensive practical experience).
- 📌 Sensitive relapse (CTFI ≥90 days): Platinum rechallenge.
- 📌 Investigational strategy: I-DXd (phase 3 ongoing, high ORR/DCR).
- 📌 Alternative chemotherapy: Topotecan (standardized, symptom control).
⚠️ Side Effects of Ifinatamab Deruxtecan
- Most patients (nearly 90%) experienced a side effect during treatment.
- In 36%, these side effects were more serious (grade 3 or higher).
- Drug dose delays or reductions: Approximately 1 in every 4 patients had a dose delay, and 15% had a dose reduction. Treatment was permanently discontinued in approximately 10%, and treatment-related death was reported in 4.4% of patients.
- Lung Inflammation (ILD/Pneumonia): Occurred in 12.4% of patients. Most cases were mild to moderate, but in 1.5% of patients it was severe and fatal.
- Most common side effects: Nausea, reduced white blood cell counts (neutropenia, leukopenia, lymphopenia), low red blood cell counts (anemia), loss of appetite, low platelets, fatigue, diarrhea, constipation and vomiting.
Important Note: Because of the risk of ILD (lung inflammation), measures such as immediate drug discontinuation and steroid treatment are vital if symptoms such as cough, shortness of breath or fever develop.
🔍 Clinical Interpretation and What Comes Next
- High ORR (48.2%) and rapid TTR (1.4 months) are noteworthy in refractory ES-SCLC.
- PFS 4.9 months, OS 10.3 months → promising compared with historical outcomes in this patient population.
- Phase 3 IDeate-Lung02 (12 mg/kg I-DXd vs physician’s choice: topotecan/amrubicin/lurbinectedin) will compare efficacy directly.
Sources
2. A study of Ifinatamab deruxtecan versus treatment of physician’s choice in subjects with relapsed small cell lung cancer (IDeate-Lung02). Clinical Trials.gov. Updated August 7, 2025. Accessed September 7, 2025. https://clinicaltrials.gov/study/NCT06203210
Was this article helpful?
Your feedback helps us improve our content.
Reader comments
Share your comment
Your name and comment are published only after administrator approval. Your email address is never shown to visitors.
Be the first to comment.