Radioimmunoconjugates

Iodine-131 was among the first radioactive isotopes used for radioimmunoconjugate preparation (Order, 1982 Regoeczi, 1984). Since the earliest studies on the efficacy of radiotherapy, additional isotopes have been employed, such as iodine-125, bismuth-212, yttrium-90, yttrium-88, technetium-99 m, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-111, indium-114 m, indium-115, and boron-10. 

Order, S.E. (1989) Therapeutic use of radioimmunoconjugates. Antibody, Immunoconjugates, Radiopharm. 2, 235. 

Another anti-CD20 radioimmunoconjugate, IDEC-Y2B8, is a 90Yt-labeled version of the murine mAh parent of rituximab. In a phase I—II study, B-cell NHL patients received an initial dose of unlabeled rituximab to clear peripheral B cells and improve biodistribution of the RIT mAh, followed by escalating doses of IDEC-Y2B8, (179). 

IMMUNOTHERAPY WITH UNCONJUGATED MONOCLONAL ANTIBODIES AND RADIOIMMUNOCONJUGATES... 

Although no radioimmunoconjugates have progressed to the market, a number have been examined in clinical trials. Bexxar ( I-tositumomab) is an anti-CD20 MoAb examined in Phase III trials for... 

Besides intravenous injection, some radioimmunoconjugate-based drug candidates have also been directly injected into the tumor sites in clinical trials and have reached Phase II and phase III development. TheraGyn (90Y -anti-Mucl) is administered to colon cancer patients by intraperitoneal injection.18 A 131I-anti-tenascin radioimmunoconjugate is injected into a cranial resection cavity of glioma patients.19 Although benefits for the patient were observed in these trials, the absorbed dose of radiation was still below the estimated dose needed to eradicate solid tumors and will need to be increased in future evaluations. 

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