AstraZeneca (AZ) and Amgen have reported that the Phase III DeLLphi-305 trial met its primary overall survival (OS) endpoint for Imdelltra (tarlatamab), Amgen’s CD3×DLL3 bispecific antibody (BsAb), combined with Imfinzi (durvalumab), AZ’s PD-L1 antibody, as first-line maintenance in extensive-stage small cell lung cancer (SCLC) after induction with platinum chemotherapy, etoposide and durvalumab.

The global, randomised, open-label study enrolled 563 patients and also hit key secondary endpoints of progression-free survival (PFS) and objective response rate (ORR), setting up a regimen that layers DLL3-directed T-cell engagement (TCE) on top of PD-L1 blockade rather than relying on chemotherapy continuation or single-agent immunotherapy.

The commercial stakes are high: SCLC accounts for about 15% of lung cancers, two-thirds being extensive-stage, with roughly 195,000 patients worldwide, current first-line standards delivering a median OS near one year, and only 3.6% of patients alive at five years. Tarlatamab already generated USD 627 million in 2025 sales on its post-platinum US label, while durvalumab booked USD 6.063 billion across multiple indications.