A sponsor provided a monoclonal antibody conjugated to DOTA chelator through a surface lysine. Invicro radiolabeled the DOTA-conjugate with both In-111 for SPECT imaging and Ac-225 for targeted alpha-therapy. Next, a rodent xenograph model was implanted with antigen-expressing tumor cells in one flank. SPECT imaging of In-111 labeled mAb showed accumulation of the radiotracer in the tumor. Administration of the Ac-225 labeled mAb showed a significant reduction of the tumor volume over time, compared to the control.