Rhodium-105 complexes of polydentate, aqueous-soluble, phosphine ligands: New radiochemical developments towards radioimmunotherapy

The water-soluble, dithio-bis(hydroxymethyl)phosphine ligands (HOH2C)(2)P(C H2)(x) S(CH2)(3)((CH4)(4)COOH)S(CH2)(x)P(CH2OH)(2) (X = 2 or 3) were comple xed with Rh-105. 'The new Rh-105-complexes were formed in high radiochemica l purity by addition of (105)RhCl(3)3H(2)O to an aqueous solution of the ap propriate ligand framework. The new complexes were formed as singular chemi cal species and did not undergo in vitro decomposition for less than or equ al to 24 hours as indicated by high performance liquid chromatographic anal yses. In vivo biodistribution analyses of the new complexes indicate that t he primary mode of excretion is the renal-urinary pathway. Results of this study suggest the potential development of new radiopharmaceuticals for the treatment of human metastases via conjugation of the new 105Rh-complexes t o site-specific biomolecular vectors.