Targeted radioimmunotherapy (RIT) with 177Lutetium labeled J591, anti-prostate-specific membrane antigen (PSMA) monoclonal antibody: Initial results of a phase 2 trial in patients with metastatic androgen-independent prostate cancer (AIPC)

128 Objectives: J591 is a humanized antibody which specifically binds to an extra-cellular epitope of PSMA. A phase 1 dose-escalation trial of 177Lu-DOTA-J591 (177Lu-J591) in patients (pts) with metastatic AIPC demonstrated excellent targeting of metastatic sites and acceptable toxicity (maximum tolerated dose) at 70 mCi/m2. Based on these findings, a phase 2 multi-center trial trial was developed to evaluate response at this level and to confirm safety. Methods: Pts with progressive metastatic AIPC received 177Lu -J591; Cohort 1 (65 mCi/m2), 15 pts; Cohort 2 (70 mCi/m2). 7 Days post treatment, 177Lu imaging was performed to confirm tumor targeting. Pain relief, PSA, tumor size and myelotoxicity was assessed 12 weeks after therapy [Rx]. Results: 21 pts (8 chemo-naive) have been treated to date; 19 evaluable at this time. 2 pts with bone-only metastases achieved PSA declines of >50%. One had an 87% PSA decline with resolution of bone pain. A 2nd pt had a PSA decline of 58% without progression at 6 mo post-Rx. PSA stabilization (