Phase I study of AMG 160, a half-life extended bispecific T-cell engager (HLE BiTE immune therapy) targeting prostate-specific membrane antigen, in patients with metastatic castration-resistant prostate cancer (mCRPC).

Abstract

TPS5590 Background: Prostate-specific membrane antigen (PSMA) is a clinically validated therapeutic target for the imaging and treatment of mCRPC. AMG 160 is an HLE BiTE immune therapy designed to redirect T cells to cancer cells by binding to PSMA on cancer cells and CD3 on T cells. BiTE immune therapy leads to direct tumor cell killing, T-cell activation and expansion, and the creation of a pro-inflammatory tumor microenvironment. Combining AMG 160 with a PD-1 inhibitor may enhance antitumor activity by enabling sustained T-cell-dependent killing of tumor cells in the inflamed tumor microenvironment. Methods: NCT03792841 is a phase I study of AMG 160 as monotherapy (part 1) and in combination with pembrolizumab (part 2) in men with histologically/cytologically confirmed mCRPC who are refractory to a novel hormonal therapy (abiraterone, enzalutamide, and/or apalutamide) and have failed 1–2 taxane regimens (or are medically unsuitable or have refused taxanes), who have ongoing castration with total serum testosterone ≤ 50 ng/dL, and have evidence of progressive disease. Patients who received prior PSMA radionuclide therapy may be eligible. Patients with CNS metastases, leptomeningeal disease, spinal cord compression, or active autoimmune disease will be excluded. Primary objectives are to evaluate safety and tolerability and determine the maximum tolerated dose (MTD) or recommended phase II dose (RP2D) of AMG 160 given as monotherapy or in combination with pembrolizumab. Secondary objectives are to characterize pharmacokinetics and preliminary antitumor activity. Exploratory objectives include evaluation of potential pharmacodynamic and patient selection biomarkers, immunogenicity, and patient-reported pain and functional outcomes. The part 1 dose exploration will determine the MTD/RP2D of AMG 160. The part 1 dose expansion will confirm the safety and tolerability of the MTD/RP2D. The part 2 dose exploration will estimate the MTD/RP2D of AMG 160 in combination with pembrolizumab. Evaluation of preliminary antitumor activity will be based on RECIST 1.1 with Prostate Cancer Working Group 3 modifications, PSA response, CTC response, progression-free survival (radiographic and PSA), and overall survival. PSMA PET/CT and FDG PET/CT imaging will be used for evaluation of exploratory objectives. The study opened in February 2019 and is currently recruiting patients into both part 1 and part 2. Clinical trial information: NCT03792841 .