Pasotuxizumab, a BiTE ® immune therapy for castration-resistant prostate cancer: Phase I, dose-escalation study findings.

Aim:  We report results of a first-in-human study of pasotuxizumab, a PSMA bispecific T-cell engager (BiTE ^® ) immune therapy mediating T-cell killing of tumor cells in patients with advanced castration-resistant prostate cancer. Patients & methods: We assessed once-daily subcutaneous (SC) pasotuxizumab. All SC patients developed antidrug antibodies; therefore, continuous intravenous (cIV) infusion was assessed. Results:  A total of 47 patients received pasotuxizumab (SC: n = 31, 0.5-172 μg/d; cIV: n = 16, 5-80 μg/d). The SC maximum tolerated dose was 172.0 μg/d. A sponsor change stopped the cIV cohort early; maximum tolerated dose was not determined. PSA responders occurred (>50% PSA decline: SC, n = 9; cIV, n = 3), including two long-term responders. Conclusion: Data support pasotuxizumab safety in advanced castration-resistant prostate cancer and represent evidence of BiTE monotherapy efficacy in solid tumors. Clinical trial registration: NCT01723475 (ClinicalTrials.gov).