Lung cancer is the leading cause of cancer death worldwide, accounting for almost one in five cancer deaths. About 15 percent of cases are small cell lung cancer, and two thirds of those are diagnosed at the extensive stage (ES-SCLC) — a fast-growing, highly metastatic disease whose median survival on the current standard of care is roughly one year. Only 3.6 percent of ES-SCLC patients are alive five years after diagnosis.
At the ESMO Congress in Madrid on Saturday, researchers presented results from the Phase III DeLLphi-305 trial, published simultaneously in the New England Journal of Medicine. The trial randomised 563 patients who had not progressed after induction with Imfinzi (durvalumab) plus platinum chemotherapy and etoposide, one-to-one, to either Imfinzi plus tarlatamab or Imfinzi alone, continued until progression or unacceptable toxicity.
The result is unusual for this disease. In the planned interim analysis, median overall survival was 21.1 months for the combination versus 12.7 months for Imfinzi alone — a 58 percent reduction in the risk of death (hazard ratio 0.42; 95 percent confidence interval 0.32-0.54; p<0.001) at a median follow-up of about 16 months. An estimated 79 percent of patients on the combination were alive at one year, against 53 percent on the checkpoint inhibitor by itself.
Progression-free survival moved with it: 7.4 months versus 1.9 months (HR 0.34; 95 percent CI 0.28-0.42), a 66 percent reduction in the risk of progression or death. At one year, 38 percent of patients on the combination were alive and progression-free, against 10 percent. The confirmed objective response rate was 26.4 percent versus 4.1 percent, and median duration of response 12.7 months versus 5.6 months. The benefit held across all prespecified subgroups, including patients with brain or liver metastases — the groups that usually do worst.
Tarlatamab is a first-in-class bispecific T-cell engager: it binds DLL3 on tumour cells and CD3 on T cells, pulling immune cells into contact with DLL3-expressing SCLC cells. DLL3 sits on the surface of SCLC cells in 85 to 96 percent of patients and is barely present on healthy tissue, which is what makes it usable as a target. Combining it with durvalumab pairs two different attacks — checkpoint blockade that releases the immune response, and direct recruitment of T cells to the tumour.
Safety was consistent with the known profiles of the individual drugs. Grade 3 and 4 treatment-related adverse events occurred in 20.9 percent of patients on the combination and 10.8 percent on Imfinzi alone. Discontinuations were infrequent and there were no treatment-related deaths. After the first infusion, patients were monitored in a healthcare setting for one to two hours, and six to eight hours in some regions including Europe — a reminder that T-cell engagers carry cytokine release risk and are not an outpatient-easy class.
Several caveats belong in the same paragraph as the headline. DeLLphi-305 is open-label and these are interim numbers, not the final analysis. Amgen sponsors the trial; AstraZeneca provided partial funding and Imfinzi. Neither company disclosed filing timelines or pricing in the announcement, and a bispecific plus checkpoint inhibitor combination will not be cheap. The control arm was Imfinzi alone rather than a broader standard, which is defensible after induction but shapes how the hazard ratio should be read.
Jacob Sands of the Dana-Farber Cancer Institute, the trial's international coordinating investigator, called the magnitude and consistency of the benefit "striking" for a disease where durable survival has been extremely hard to achieve, and pointed to the effect in patients with brain metastases. Leora Horn of AstraZeneca went further: "will redefine treatment standards." For the roughly 195,000 people expected to be treated for extensive-stage SCLC globally in 2026, this is the first substantial survival gain in years — if they can get it.
