Imdelltra Plus Imfinzi Extends Survival in Small Cell Lung Cancer

Adding Imdelltra (tarlatamab) to Imfinzi (durvalumab) maintenance therapy helped people with extensive-stage small cell lung cancer live about eight months longer than Imfinzi alone, according to full results of the phase 3 DeLLphi-305 trial. The results were presented Oct. 24, 2026, at the European Society for Medical Oncology (ESMO) Congress 2026 in Madrid, Spain, and published at the same time in The New England Journal of Medicine.

CURE first reported on Oct. 5, 2026, that the trial met its main goal. At that time, the specific survival numbers had not been released.

Who This Applies To

Extensive-stage small cell lung cancer is small cell lung cancer that has spread widely in the chest or to other parts of the body. It tends to grow quickly. Many patients first receive chemotherapy (a platinum drug plus etoposide) together with the immunotherapy Imfinzi. If the cancer does not grow during that treatment, patients usually continue on Imfinzi alone. This is called maintenance therapy.

Imdelltra is a type of drug called a bispecific T-cell engager. It attaches to a protein called DLL3 on small cell lung cancer cells and to the body's T cells, a kind of immune cell, bringing them together so the T cells can attack the cancer. It is already approved in the United States for adults with extensive-stage small cell lung cancer that has worsened during or after platinum-based chemotherapy. DeLLphi-305 tested whether adding it earlier, during first-line maintenance, could help.

What the Trial Found

The trial included 563 patients whose cancer had not worsened after first-line Imfinzi plus chemotherapy. They were randomly assigned to receive either Imdelltra plus Imfinzi or Imfinzi alone. Patients with brain metastases, whether treated or untreated, could join if the metastases were not causing symptoms.

• Overall survival: Patients who received Imdelltra plus Imfinzi lived a median of 21.1 months, compared with 12.7 months for Imfinzi alone. This means a 58% lower risk of death.
• Survival at one year: Nearly 80% of patients in the Imdelltra group were alive at 12 months, compared with 53% in the Imfinzi-alone group.
• Progression-free survival: The cancer was kept from growing for a median of 7.4 months with the combination, compared with 1.9 months with Imfinzi alone.
• Response: The cancer shrank in 26.4% of patients in the combination group, compared with 4.1% of those on Imfinzi alone.

Patients were followed for a median of about 16 months.

Side Effects

Serious (grade 3 or higher) side effects related to treatment happened in 20.9% of patients who received the combination and 10.8% of those who received Imfinzi alone. The most common serious side effects with the combination included low white blood cell counts, decreased appetite, weakness and weight loss.

About half of patients (49.6%) who received Imdelltra had cytokine release syndrome, a reaction that happens when the immune system is activated and can cause fever, chills and low blood pressure. Almost all cases were mild or moderate, with one severe case and no life-threatening cases. A nervous system side effect called ICANS, which can cause confusion or trouble speaking, occurred in 1.1% of patients and was not severe in any case.

What Comes Next

Imdelltra is not yet approved for use in first-line maintenance. Amgen, which makes Imdelltra, said it plans to share the results with regulators around the world. In this trial, patients and their doctors knew which treatment each patient was getting, a design known as open-label.

Patients with extensive-stage small cell lung cancer who want to know whether these results may apply to them, or whether a clinical trial is an option, should talk with their oncologist.

References

1. "Imdelltra in Combination With Imfinzi Reduced Risk of Death by an Unprecedented 58% in First-Line Extensive Stage Small Cell Lung Cancer." Amgen. Oct. 24, 2026.
2. “Tarlatamab–Durvalumab Maintenance for Extensive-Stage Small-Cell Lung Cancer.” The New England Journal of Medicine. Oct. 24, 2026. DOI: 10.1056/NEJMoa2609482.

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