ABSTRACT
This chapter discusses the extension of the technique fromγ-emitters to particulate-emitting radionuclides for use in radioimmunotherapy (RAIT). It presents the advantages of usingα-particle-emitting radionuclides for RAIT. The use of monoclonal antibodies (MoAbs) as targeting vectors for use in radioimmunoscintigraphy is becoming an established clinical procedure. The direct radioiodination of proteins, including MoAbs and their fragments whereby the iodonium ion adds to protein tyrosine residues in the position ortho to the hydroxyl group in the aromatic ring. Unfortunately, yttrium (Y) is an element with great avidity for cortical bone, and unbound metal will quickly localize in the bone, which for RAIT with Y results in unacceptable radiotoxicity. Radium has interesting properties for RAIT since it is an α-emittting radionuclide with an 11.4-d half-life. Direct labeling of antibodies with astatine using electrophilic addition to tyrosine residues results in a carbon-astatine bond which is not sufficiently stable for RAIT purposes.
