CA9 and neoplasm: Here, we investigate the potential of TAT as monotherapy and in combination with immune checkpoint inhibitors (ICI) to treat hypoxic tumors.<h4>Methods</h4>Monoclonal anti-CAIX antibody DOTA-MSC3 was labeled with indium-111 (<sup>111</sup>In) or actinium-225 (<sup>225</sup>Ac), and binding to CAIX-expressing hypoxic tumor cells was determined <i>in vitro</i>.