A direct labelling method for anti-CEA monoclonal antibody (McAb)

C 50 was labelled with 188Re has been established. Making use of sodium gluconate as chelator

SnCl 2 as reducing agent

the McAb C 50 was reduced by Vitamin C

and then labelled with 188Re. In this process

the in vitro stability of labelled 188Re-C 50 was observed

the concentration of SnCl 2

sodium gluconate

and McAb as well as the affection of interval time of adding McAb on radiochemical purity of labelled C 50 were determined. SPECT imaging was performed to show the biological distribution of 188Re labelled C 50 after injected into the tumor of nude mice. The pathologic study was observed by electron microscopy after therapy. The experimental results showed that the optimal condition for 188Re labelling C 50 was as follows: the concentration of SnCl 2

sodium gluconate and McAb was 2.2-4.0g/L

0.3mol/L and 2.5×10 5-5.0×10 5mol/L respectively. The labelling efficiency 2h post labelling was as high as 90%. The radioactivity was localized in the tumor after 188Re-C 50 was injected into it

and the tumor began to shrink 2 weeks later

the disruption and necrosis of the tumor cells were observed microscopically.