CYTOTOXICITY OF BI-213-IMMUNOCONJUGATES AND AC-225-IMMUNOCONJUGATES

This paper describes in vitro cytotoxicity experiments with Bi-213- an d Ac-225-immunoconjugates on the human epidermoid tumour cell line A43 1 using a blood group A-reactive murine IgG (2D11) as the specific ant ibody and MOPC 21 as the control antibody. With both radionuclides, sp ecific cell-killing was achieved. The observed cytotoxicity of Bi-213 (T-1/2 = 47 min) indicates that this radionuclide is a useful alternat ive for the alpha-emitter Bi-212 in the treatment of blood-borne malig nancies. Ac-225-immunoconjugates (T-1/2 of (225)AC is 10 days) may be applicable for the treatment of solid rumours, since the daughter radi onuclides of (225)AC contribute to the cytotoxic efficacy by a field e ffect (i.e. toxicity in an area distal from the antibody-binding site) . The lack of an adequate chelator for (225)AC is a major drawback.