What type of study is this?

This is a Quantitative Study study.

September 16, 2025

Data from Safety and Efficacy of Tarlatamab in Patients with Neuroendocrine Prostate Cancer: Results from the Phase 1b DeLLpro-300 Study

Key Points

Tarlatamab achieved an objective response rate of 10.5% in neuroendocrine prostate cancer patients, indicating limited efficacy.
Among DLL3-positive tumors, the objective response rate was significantly higher at 22.2%, suggesting a targeted effect.
The most common adverse event was cytokine release syndrome, experienced by 82.5% of patients, primarily low-grade.
The median duration of response for tarlatamab was 7.3 months in the overall patient cohort, highlighting some clinical activity.

Abstract

AbstractPurpose:Neuroendocrine prostate cancer (NEPC) is an aggressive form of prostate cancer with poor prognosis and limited treatment options. As NEPC aberrantly expresses delta-like ligand 3 (DLL3), the activity of tarlatamab, a bispecific T-cell engager that directs cytotoxic T cells to DLL3-positive (DLL3+) cells, was evaluated in the DeLLpro-300 study (NCT04702737).Patients and Methods:This was a phase 1b, open-label study evaluating tarlatamab monotherapy in patients with metastatic de novo or treatment-emergent NEPC defined by histologic, genomic, or IHC criteria. Tarlatamab was administered intravenously every 2 weeks at a dose of 100 mg with a 1-mg step dose. The primary objective was safety, and a secondary objective was objective response rate (ORR) per RECIST v.1.1; DLL3 expression was retrospectively assessed by IHC.Results:Forty patients were enrolled (DLL3+ tumors, n = 18; DLL3− tumors, n = 14; and DLL3 unknown tumors, n = 8). The most common treatment-related adverse events were cytokine release syndrome (82.5%), dysgeusia (42.5%), and decreased appetite (40.0%). Cytokine release syndrome was predominantly of low grade (grade 1/2/3/4+, 62.5%/15%/5%/0%), occurred exclusively in cycle 1, and was transient in duration (median duration, 3 days). The ORR was 10.5% 95% confidence interval (CI), 2.9–24.8; the median duration of response was 7.3 months in the overall cohort. Patients with DLL3+ tumors (vs. patients with DLL3−/DLL3 unknown tumors) achieved a higher ORR 22.2% (95% CI, 6.4–47.6) vs. 0% (95% CI, 0–15.4) and radiographic progression-free survival rate at 6 months 27.7% (95% CI, 8.7–50.9) vs. 0%.Conclusions:The DeLLpro-300 study provides preliminary evidence for the safety and antitumor activity of tarlatamab in DLL3+ NEPC.

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