Metal complexes of bleomycin: evaluation of [Rh-105]-bleomycin for use in targeted radiotherapy

Bleomycin has been used as a carrier for several radioisotopes; however, its potential for clinical use has been limited either by the in vivo stability of the complexes or the half-life of the isotope used. The chemical, biological, and radiological properties of 105Rhodium appear to make it an ideal choice for targeted radiotherapy. The synthesis and purification of a hereto unreported 105Rhodium-bleomycin (105Rh-BLM) complex is described. The stability of this complex in plasma is sufficient to allow targeted delivery of the radioisotope. 57Cobalt-bleomycin was studied under identical conditions for comparative purposes. The suitability of 105Rh-BLM for targeted therapy, which appears to be limited by the renal clearance of this agent, is discussed.