Amgen's cancer drug Imdelltra, combined with AstraZeneca's immunotherapy Imfinzi, reduced the risk of death by 58% in a Phase 3 trial involving patients with extensive-stage small cell lung cancer, according to results presented on October 24, 2026.
The DeLLphi-305 trial found that patients receiving the combination as maintenance treatment lived for a median of 21.1 months, compared with 12.7 months among those treated with Imfinzi alone. Nearly 80% of patients receiving both medicines were alive after one year, compared with 53% in the single-drug group.
The study involved 563 patients whose cancer had not progressed following initial treatment with Imfinzi, platinum-based chemotherapy and etoposide. Participants were randomly assigned to receive either the drug combination or Imfinzi alone as maintenance therapy.
The combination also improved progression-free survival, the period during which patients live without their disease worsening. Median progression-free survival was 7.4 months with both drugs, compared with 1.9 months with Imfinzi alone.
However, the combination was associated with additional safety risks. Grade 3 or higher treatment-related adverse events occurred in 20.9% of patients receiving both drugs, compared with 10.8% of those receiving Imfinzi alone. Cytokine release syndrome, an inflammatory reaction that can become serious, was reported in 49.6% of patients receiving Imdelltra. Most cases were mild or moderate, and one was classified as severe.
Imdelltra, also known as tarlatamab, is a targeted immunotherapy that helps immune T cells recognise and attack cancer cells expressing the DLL3 protein. In the United States, it is approved for adults with extensive-stage small cell lung cancer that has progressed during or after platinum-based chemotherapy.
The results could support wider use of the medicine earlier in treatment, although regulatory decisions and further clinical assessment will determine its future role.

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