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Sandy Srinivas, MD


ESMO 2023: Early Results With Novel Bispecific Antibody in Metastatic Prostate Cancer

By: Celeste L. Dixon
Posted: Monday, October 30, 2023

In a first-in-human phase I trial of AMG 509 (xaluritamig) monotherapy in heavily pretreated patients with metastatic castration-resistant prostate cancer, the drug was found to be tolerable—with low-grade cytokine-release syndrome occurring primarily during the first treatment cycle—and to have preliminary activity. William Kelly, DO, of Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, and colleagues presented the interim dose-exploration results of their study at the European Society for Medical Oncology (ESMO) Congress 2023 (Abstract 1765O).

Xaluritamig is a novel bispecific XmAb 2+1 T-cell engager with two STEAP1 binding sites designed to facilitate T-cell–mediated lysis of STEAP1-expressing cells. It was administered intravenously either once weekly or once every 2 weeks at 15 different dose levels. Eligible patients had metastatic castration-resistant prostate cancer refractory to prior hormonal therapy and one to two taxane regimens and an Eastern Cooperative Oncology Group performance status of 0 to 1.

As of March 2023, 97 patients (median age, 67 years) had received one or more doses of xaluritamig. Overall, 15 patients (22.7%) had confirmed partial responses, and 30 (45.5%) had stable disease. At the higher dose levels, 14 patients (38.9%) had confirmed partial responses, and 12 (33.3%) had stable disease. Declines in prostate-specific antigen (PSA) levels of 50% and 90% occurred in 42 (47.2%) and 24 (27.0%) patients, respectively. PSA responses were more frequent at higher dose levels than at lower dose levels, noted the team.

All patients had treatment-emergent adverse events (grade ≥ 3, 74.2%), and almost all (95.9%) reported treatment-related adverse events (grade ≥ 3, 52.6%). The most common adverse events were cytokine-release syndrome (72.2%)—primarily grade 1 or 2—fatigue (52.6%), anemia (45.4%), pyrexia (40.2%), and myalgia (39.2%). In 17.5% of patients, treatment-related adverse events led to discontinuation of treatment.

Disclosure: For full disclosures of the study authors, visit

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