PURPOSE: Metastatic castration-resistant prostate cancer (mCRPC) remains a disease with high unmet medical need, as most patients do not achieve durable response with available treatments. Prostate-specific membrane antigen (PSMA) is a compelling target for mCRPC. It is highly expressed by primary and metastatic prostate cancer (PCa) cells, with increased expression after progression on androgen deprivation therapy. EXPERIMENTAL DESIGN: We developed AMG 160, a half-life extended bispecific T-cell engager (HLE BiTE(®)) immuno-oncology therapy that binds PSMA on PCa cells and CD3 on T cells for treatment of mCRPC. AMG 160 was evaluated in vitro and in mCRPC xenograft models. AMG 160 tolerability was assessed in non-human primates (NHP). AMG 160 activity as monotherapy and combination with a PSMA imaging agent, novel hormonal therapy, and immune checkpoint blockade was evaluated. RESULTS: AMG 160 induces potent, specific killing of PSMA-expressing PCa cell lines in vitro, with half-maximal lysis of 6-42 pM. In vivo, AMG 160 administered weekly at 0.2 mg/kg engages T cells administered systemically and promotes regression of established 22Rv-1 mCRPC xenograft tumors. AMG 160 is compatible with the imaging agent (68)Ga-PSMA-11 and shows enhanced cytotoxic activity when combined with enzalutamide or anti-PD-1 antibody. AMG 160 exhibits an extended half-life and has an acceptable safety profile in NHP. CONCLUSIONS: The preclinical characterization of AMG 160 highlights its potent antitumor activity in vitro and in vivo, and its potential for use with known diagnostic or therapeutic agents in mCRPC. These data support the ongoing clinical evaluation of AMG 160 in patients with mCRPC.