Tarlatamab and Durvalumab Combination Achieves Overall Survival Benefit in First-Line Extensive-Stage Small Cell Lung Cancer

Regulatory authorities reviewing treatments for the most aggressive form of lung cancer will soon evaluate a dual-immunotherapy maintenance strategy, following Phase 3 trial results that successfully met their primary survival endpoints. In September 2026, Amgen and AstraZeneca announced that combining the bispecific T-cell engager tarlatamab with the PD-L1 inhibitor durvalumab significantly extended overall survival for patients with extensive-stage small cell lung cancer (ES-SCLC). The data from the late-stage DeLLphi-305 trial will be submitted to global regulators, positioning the combination for potential approval as a first-line maintenance therapy and offering a new biological mechanism to patients immediately following their initial chemotherapy.[1][2][3]

The global DeLLphi-305 trial enrolled 563 patients who had already completed an initial induction regimen consisting of durvalumab alongside platinum-based chemotherapy and etoposide. Participants in the study were randomized evenly to receive either the combination of tarlatamab and durvalumab or to continue with durvalumab alone. At a pre-specified interim analysis, the dual-therapy arm demonstrated a statistically significant and highly clinically meaningful improvement in overall survival, which served as the trial's primary endpoint. By intervening before the cancer could resume its rapid growth, the combination therapy proved capable of extending the lives of patients facing a historically bleak prognosis.[3][6]

Beyond the primary survival metric, the combination therapy also succeeded across key secondary endpoints designed to measure the depth and durability of the clinical benefit. Patients receiving both drugs showed statistically significant improvements in progression-free survival and objective response rate compared to those on the monotherapy arm. While exact median survival estimates and hazard ratios were withheld pending a formal presentation at an upcoming medical congress, the trial sponsors confirmed the safety profile remained consistent with the known effects of the individual agents, with no new or unexpected safety signals identified during the interim analysis.[1][2][3]

The results represent a biological milestone for the use of bispecific T-cell engagers in solid tumors, a modality previously most successful in blood cancers. Tarlatamab is engineered to bind simultaneously to CD3 receptors on T cells and to delta-like ligand 3 (DLL3), a protein expressed on the surface of SCLC cells in approximately 85% to 96% of patients. By physically bridging the patient's own immune cells directly to the tumor cells, the drug forces the immune system to recognize and lyse the cancer, bypassing the tumor's typical evasion mechanisms and creating a highly targeted immune response.[6][7]

Extensive-stage small cell lung cancer accounts for roughly 70% of all SCLC diagnoses, typically presenting only after the disease has already metastasized beyond the lungs to other organs or the brain. Historically, the five-year overall survival rate for the extensive stage has hovered around a dismal 3%, with standard platinum-based chemotherapy regimens offering an average survival of just 7 to 11 months. The introduction of maintenance immunotherapies like durvalumab in recent years previously pushed that median survival to between 10 and 15 months, but long-term survival has remained exceedingly rare for this patient population.[7]

Tarlatamab, which is marketed by Amgen under the brand name Imdelltra, already holds an accelerated approval from the U.S. Food and Drug Administration for adults with ES-SCLC whose disease has progressed on or after platinum-based chemotherapy. The DeLLphi-305 trial was specifically designed to move the drug earlier in the treatment sequence, deploying it immediately after initial chemotherapy to delay that inevitable recurrence. The trial sponsors did not release direct commentary or quotations from the principal investigators in their initial data summaries, opting to hold detailed clinical perspectives and exact hazard ratios for the upcoming medical congress.[1][3]

For clinical oncology practice, the shift to a first-line maintenance setting means patients could receive the targeted BiTE therapy before their cancer develops the broad, aggressive resistance that characterizes relapsed SCLC. Durvalumab, marketed by AstraZeneca as Imfinzi, is already an established standard-of-care maintenance option for these patients. Adding tarlatamab to the regimen requires monitoring patients in a healthcare setting for up to eight hours during their initial infusions to manage potential immune-related adverse events, such as cytokine release syndrome, which is a known risk of T-cell engaging therapies.[3][7]

Amgen and AstraZeneca plan to submit the comprehensive DeLLphi-305 data to global regulatory authorities in the coming months to seek formal label expansions. If regulatory agencies approve the expanded indication, the tarlatamab and durvalumab combination would become the first BiTE-based regimen authorized for first-line maintenance in extensive-stage small cell lung cancer. This approval would fundamentally alter the standard sequence of care for the disease, establishing a new dual-immunotherapy baseline for patients who currently have very few options to prevent their cancer from returning.[1][2]