Amgen's Imdelltra with Imfinzi cuts risk of death by 58% in first-line small cell lung cancer

Amgen and AstraZeneca reported on 24 October 2026 that adding Amgen's Imdelltra (tarlatamab) to AstraZeneca's Imfinzi (durvalumab) as first-line maintenance cut the risk of death by 58% in extensive-stage small cell lung cancer, against Imfinzi alone, in the Phase 3 DeLLphi-305 trial ¹². The interim results were presented in a Presidential Symposium at the ESMO Congress 2026 in Madrid (abstract LBA3) and published at the same time in The New England Journal of Medicine ¹².

What the trial found

DeLLphi-305 is a global, randomised, open-label study sponsored by Amgen, with AstraZeneca providing Imfinzi and part of the funding ¹². It randomised 563 patients 1:1 after they had completed induction with Imfinzi, platinum chemotherapy and etoposide without their disease progressing ². Overall survival was the primary endpoint ¹.

At a median follow-up of about 16 months, the overall survival hazard ratio was 0.42 (95% CI 0.32 to 0.54; p<0.001) ². Median survival was 21.1 months with the combination and 12.7 months with Imfinzi alone, and an estimated 79% of patients on the combination were alive at one year, against 53% ². AstraZeneca describes the combination's median survival as the longest reported in a Phase III trial in extensive-stage disease ².

The secondary endpoints moved the same way. Median progression-free survival was 7.4 months against 1.9 months (HR 0.34), and 38% of patients on the combination were alive without progression at one year, against 10% ². The confirmed response rate was 26.4% against 4.1%, and median duration of response was 12.7 months against 5.6 months ². The benefit held across all prespecified subgroups, including patients with brain or liver metastases ². Data were cut off on 7 July 2026 ².

Grade 3 or higher treatment-related adverse events affected 20.9% of patients on the combination and 10.8% on Imfinzi alone ¹. Cytokine release syndrome occurred in 49.6% of patients given Imdelltra, almost all of it Grade 1 or 2, with one Grade 3 event ¹. Neurotoxicity (ICANS) was seen in 1.1%, none of it Grade 3 or above ¹.

What it means for the market

The result moves a T-cell engager into the first-line setting of a cancer where, AstraZeneca notes, median survival on the current standard of care is approximately one year and only 3.6% of extensive-stage patients are alive five years after diagnosis ². AstraZeneca estimates that 195,000 people worldwide will be treated for extensive-stage disease in 2026 ².

For both companies the data widen the commercial case. Amgen said it is "moving with urgency to share these results with regulatory authorities worldwide" ¹. AstraZeneca presents the trial as support for keeping Imfinzi as the immunotherapy backbone across stages of the disease, and Leora Horn, its senior vice president for late development oncology, said the regimen "will redefine treatment standards" ². Amgen also reported longer follow-up from other studies: a median overall survival of 37.9 months in the Phase 1b DeLLphi-303 maintenance trial, and a 38% reduction in the risk of death against chemotherapy in the second-line Phase 3 DeLLphi-304 trial after 23 months of follow-up ¹.

Service capacity is a practical consideration for health systems. The protocol required patients to be monitored in a healthcare setting for 1 to 2 hours after the first two Imdelltra infusions, rising to 6 to 8 hours in some regions, Europe among them ¹².

The main caveat is that the survival figures come from a planned interim analysis of an open-label trial, so the final results may differ ². Neither company gave a date for regulatory filings ¹².