Tarlatamab Plus Durvalumab Improves Survival in First-Line ES-SCLC

The combination of tarlatamab-dlle (Imdelltra; Amgen) and durvalumab (Imfinzi; AstraZeneca) significantly improved overall survival (OS) as first-line maintenance treatment for patients with extensive-stage small cell lung cancer (ES-SCLC), according to topline findings from the phase 3 DeLLphi-305 trial (NCT06211036).¹

The combination also produced statistically significant and clinically meaningful improvements in progression-free survival (PFS) and objective response rate compared with durvalumab alone. The findings represent the first reported phase 3 survival benefit from combining an immune checkpoint inhibitor with a bispecific T-cell engager in this treatment setting.¹

DeLLphi-305 Evaluates a New Maintenance Strategy

DeLLphi-305 is a global, randomized, open-label phase 3 trial that enrolled 563 patients with ES-SCLC. Patients first received induction treatment with durvalumab, etoposide, and either carboplatin or cisplatin. Those whose disease did not progress were randomly assigned to receive maintenance tarlatamab plus durvalumab or durvalumab alone until disease progression or unacceptable toxicity.^1,2

The primary end point was OS. PFS was a key secondary end point, with objective response rate also included in the efficacy assessment. The trial permitted patients with treated or untreated asymptomatic brain metastases at baseline, an important consideration because SCLC frequently spreads to the brain.¹

At a prespecified interim analysis, the combination met the primary OS end point and the secondary PFS and response end points. The overall safety and tolerability profiles were reportedly consistent with the known profiles of the individual agents, with no new safety signals identified.¹

Because the announcement contains only topline findings, the clinical magnitude of its benefit cannot yet be independently evaluated. Duration of follow-up, treatment discontinuation rates, subgroup outcomes, and the incidence of immune-mediated or T-cell–engager–associated toxicities will be essential when the complete data are reported.

Combining Complementary Immunotherapy Mechanisms

Durvalumab is a monoclonal antibody that blocks programmed death-ligand 1, limiting interactions with programmed cell death protein 1 and CD80. This releases inhibitory signaling that tumors can use to evade immune detection. Durvalumab combined with platinum-etoposide chemotherapy is an established first-line treatment for ES-SCLC based on the phase 3 CASPIAN trial (NCT03043872).³

Tarlatamab is a bispecific T-cell engager that binds delta-like ligand 3 (DLL3) on tumor cells and CD3 on T cells. This interaction brings T cells into proximity with DLL3-expressing cancer cells and promotes tumor-cell killing. DLL3 is expressed on the surface of SCLC cells in approximately 85% to 96% of patients, with limited expression in healthy tissue.¹

The FDA granted traditional approval to tarlatamab in November 2025 for adults with ES-SCLC whose disease progressed during or after platinum-based chemotherapy. That indication is supported by the phase 3 DeLLphi-304 trial and remains distinct from the investigational first-line maintenance use evaluated in DeLLphi-305.⁴

The new strategy moves tarlatamab earlier, before documented progression, and pairs it with continued checkpoint inhibition. This timing could matter in ES-SCLC because the disease often progresses rapidly, and some patients never remain well enough to receive subsequent therapy.

Pharmacist Role in Treatment Implementation

The potential addition of tarlatamab to first-line maintenance therapy would create important operational and safety considerations for oncology pharmacists. Tarlatamab carries a boxed warning for serious or life-threatening cytokine release syndrome (CRS) and neurologic toxicity, including immune effector cell–associated neurotoxicity syndrome.⁵

During DeLLphi-305, patients were monitored in a health care setting after tarlatamab administration on cycle 1, days 1 and 8.¹ If the combination receives regulatory approval, pharmacists would help implement step-up dosing and monitoring requirements based on the finalized prescribing information. They would also contribute to CRS management protocols, neurologic assessments, and patient education about symptoms requiring urgent evaluation.

Pharmacists would need to distinguish adverse effects related to T-cell engagement from immune-mediated toxicities that are associated with durvalumab. Medication reconciliation and supportive-care planning would remain important for patients who recently completed platinum-based chemotherapy and may enter maintenance with residual cytopenias or treatment-related fatigue.

The DeLLphi-305 results establish a promising direction for earlier DLL3-targeted therapy in ES-SCLC. Full efficacy and safety data will determine whether the combination can redefine maintenance treatment for this aggressive malignancy.

REFERENCES

1. Imfinzi plus Imdelltra demonstrated a statistically significant and highly clinically meaningful improvement in overall survival and progression-free survival in 1st-line extensive-stage small cell lung cancer. News release. AstraZeneca. September 8, 2026. Accessed September 9, 2026. https://www.astrazeneca.com/media-centre/press-releases/2026/imfinzi-imdelltra-improved-os-in-small-cell-lung.html

2. Study comparing tarlatamab and durvalumab versus durvalumab alone in first-line ES-SCLC following platinum, etoposide, and durvalumab. ClinicalTrials.gov identifier: NCT06211036. Updated December 17, 2025. Accessed September 9, 2026. https://clinicaltrials.gov/study/NCT06211036

3. Paz-Ares L, Dvorkin M, Chen Y, et al. Durvalumab plus platinum-etoposide versus platinum-etoposide in first-line treatment of extensive-stage small-cell lung cancer (CASPIAN): a randomised, controlled, open-label, phase 3 trial. Lancet. 2019;394(10212):1929-1939. doi:10.1016/S0140-6736(19)32222-6

4. FDA grants traditional approval to tarlatamab-dlle for extensive-stage small cell lung cancer. News release. FDA. November 19, 2025. Accessed September 9, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-traditional-approval-tarlatamab-dlle-extensive-stage-small-cell-lung-cancer

5. Imdelltra (tarlatamab-dlle) prescribing information. Amgen Inc. Accessed September 9, 2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/761344s000lbl.pdf