Iodinated bleomycin: an unsatisfactory radiopharmaceutical for tumor localization.
Cobalt-57-bleomycin is a clinically useful tumor-localizing agent, but attempts to label bleomycin (BLEO) with other radionuclides have been made because of the long physical half-life of 57Co. As an alternative labeling approach, we iodinated BLEO both directly on the imidazole ring and indirectly by reaction with N-succinimidyl 3-(4-hydroxy, 3-iodophenyl) propionate. Directly iodinated BLEO retained antibacterial activity, but in tumor-bearing rats it showed a lower tumor-to-blood ratio (2.3) at 2 hr than did 57Co-BLEO (11.8). The antibacterial activity of the indirectly labeled BLEO was markedly reduced and this material showed a tumor-to-blood ratio of 0.55 at 2 hr. The radioiodinated bleomycins are not suitable substitutes for 57Co-BLEO as tumor-imaging radiopharmaceuticals.
D000230:Adenocarcinoma / Q000175:diagnosis; D000818:Animals; D001761:Bleomycin; D003037:Cobalt Radioisotopes; D005260:Female; D007457:Iodine Radioisotopes; D008325:Mammary Neoplasms, Experimental / Q000175:diagnosis; D009369:Neoplasms / Q000175:diagnosis*; D011817:Rabbits; D011877:Radionuclide Imaging; D051381:Rats
D003037:Cobalt Radioisotopes; D007457:Iodine Radioisotopes; D001761:Bleomycin