A Historic Success in Extensive-Stage Small Cell Lung Cancer: Meaningful Survival Benefit From the Tarlatamab and Durvalumab Combination

The global Phase 3 DeLLphi-305 trial met its primary endpoint at a pre-planned interim analysis: as first-line maintenance therapy in extensive-stage small cell lung cancer, tarlatamab plus durvalumab delivered a statistically significant improvement in overall survival compared with durvalumab alone. It is the first Phase 3 trial in which a BiTE therapy has shown a survival benefit in this setting.

8 September 2026 — The global Phase 3 DeLLphi-305 trial, evaluating first-line maintenance therapy in patients with extensive-stage small cell lung cancer (ES-SCLC), successfully met its primary endpoint at a pre-planned interim analysis. According to the data announced, the combination of tarlatamab (Imdelltra) and durvalumab (Imfinzi) produced a statistically significant and clinically striking improvement in overall survival (OS) compared with patients treated with durvalumab alone.

Striking Results From the DeLLphi-305 Trial

DeLLphi-305 was designed as first-line maintenance therapy in patients with extensive-stage small cell lung cancer (563 patients) whose disease had not progressed after initial treatment with durvalumab, platinum-based chemotherapy and etoposide.

Overall survival (OS): Overall survival was markedly longer in the arm receiving tarlatamab plus durvalumab than in the standard single-agent durvalumab arm.
Success in secondary endpoints: The trial also showed statistically significant improvements in critical secondary endpoints such as progression-free survival (PFS, the time lived without disease progression) and objective response rate (ORR).
A historic milestone: The trial enters the medical literature as the first Phase 3 clinical study in which a "bispecific T-cell engager" (BiTE) therapy has demonstrated an overall survival benefit as first-line maintenance treatment in extensive-stage small cell lung cancer.

Why Is This a Historic Step in Small Cell Lung Cancer?

Small cell lung cancer (SCLC) is one of the most aggressive and rapidly progressing cancer types, accounting for roughly 13-15% of the more than 2.6 million lung cancer cases diagnosed worldwide each year.

Even with current standard treatments, median survival from the start of first-line maintenance therapy generally remains around one year, and only about 40% of patients reach second-line treatment. The results of DeLLphi-305 carry the potential to change the natural course of SCLC and to offer patients a meaningfully longer life expectancy at an earlier stage.

An Innovative Mechanism of Action: BiTE Technology and the DLL3 Target

Tarlatamab, the first in its class, is a targeted immunotherapy (BiTE) designed to bind simultaneously to the DLL3 protein on tumor cells and to the CD3 receptor on the immune system's T cells.

This dual binding mechanism activates the patient's own T cells so that they directly destroy cancer cells expressing DLL3. The DLL3 protein is densely present on the tumor surface in roughly 85-96% of SCLC patients while being almost absent on healthy cells, which allows the drug to target the cancer directly.

Safety and Side Effect Management

The safety data obtained in the trial were consistent with the previously known safety profiles of tarlatamab and durvalumab, and no new or unexpected safety signal was identified.

Cytokine release syndrome (CRS) and neurologic toxicity (ICANS) are among the side effects requiring the closest attention with this combination.
Step-up dosing: To keep these side effects manageable, the drug must be administered with gradual dose escalation (step-up dosing).
Close monitoring: After the day 1 and day 8 infusions of the first cycle, patients must be kept under close observation at a healthcare facility (for periods ranging from 1-2 hours to, in some regions, 6-8 hours).

The full data from the Phase 3 trial are planned to be presented to the scientific community at an upcoming international medical congress ahead of detailed publication.

💬 Important Information for Our Patients

Although the active substance tarlatamab already holds an FDA approval for later lines of therapy in extensive-stage small cell lung cancer (in patients whose disease has progressed), the first-line maintenance therapy in combination with durvalumab that is the subject of this news has not yet been approved by the U.S. Food and Drug Administration (FDA) or other health authorities. When this innovative combination will enter standard use, and when it will reach our country, is not known at this stage. Our clinic continues to follow such promising developments in the field of oncology closely on behalf of our patients.

Conclusion

Small cell lung cancer has remained for decades one of the cancer types in which treatment options have advanced the least. DeLLphi-305 shows for the first time at Phase 3 level that an approach directing T cells straight at the tumor can extend survival at the most critical point of the disease, the maintenance phase after initial treatment. Whether this combination will redefine the standard of care will become clear once the full data are published and regulatory review is complete.

References

Amgen. (8 September 2026). IMDELLTRA® In Combination With IMFINZI® Demonstrated Landmark Improvement In Overall Survival In First-Line Extensive Stage Small Cell Lung Cancer [Press release].
ClinicalTrials.gov. (2026). Study comparing tarlatamab and durvalumab versus durvalumab alone in first-line extensive-stage small-cell lung cancer (ES-SCLC) following platinum, etoposide and durvalumab (DeLLphi-305). U.S. National Library of Medicine. ClinicalTrials.gov Identifier: NCT06211036.