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

Abstract

TPS261 Background: AMG 160 is a novel HLE BiTE immune therapy that redirects T cells to kill tumor cells by binding to PSMA on tumor cells and CD3 on T cells. Methods: Primary objectives of this open-label, ascending, multiple-dose, phase 1 study (NCT03792841) are to evaluate safety and tolerability and determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of AMG 160 in men with mCRPC; secondary objectives are to characterize pharmacokinetics (PK) and evaluate preliminary efficacy. The dose exploration will estimate the MTD or RP2D by Bayesian logistic regression modeling. The dose expansion will assess safety, efficacy, PK, and pharmacodynamics (PD) of the selected dose and provide further safety and efficacy data. PD biomarkers and potential patient selection biomarkers will be explored. Preliminary antitumor activity will be assessed by objective response per RECIST 1.1 with PCWG3 modifications, PSA response, duration of response, time to progression, PFS (radiographic and PSA)/OS, and circulating tumor cell (CTC) response (CTC0 and CTC conversion). Imaging will include CT/MRI, bone scan, 68Ga-PSMA-11 PET/CT, and 18F-FDG PET/CT. In cycle 1, patients will be pretreated with dexamethasone before short-term IV infusion of AMG 160 and will be hospitalized for 72 h after each AMG 160 dose. Key inclusion criteria: age ≥18 y; histologically/cytologically confirmed mCRPC that progressed after novel hormone therapy; failure of 1–2 taxane-based regimens or have refused a taxane regimen; bilateral orchiectomy or continuous androgen-deprivation therapy; evidence of progressive disease; total serum testosterone ≤50 ng/dL. Key exclusion criteria: active autoimmune disease or diseases requiring immunosuppressive therapy (low-dose prednisone permitted); CNS metastases, leptomeningeal disease, or spinal cord compression; prior PSMA-targeted therapy (177Lu-PSMA-617 may be allowed). The study will enroll 30–50 patients in the dose exploration and 50 patients in the dose expansion globally. The study opened in January 2019; dose exploration is ongoing. Clinical trial information: NCT03792841.