ERBB2 and cancer: As main goal, we evaluated site-specific conjugation of DTPA chelator to A9, labelling of DTPA-A9 conjugate with radionuclide 111In, evaluation of 111In-DTPA-A9 binding to living HER2-expressing cancer cells in vitro, its stability in vitro and in vivo and biodistribution of 111In-DTPA-A9 in vivo.