PREPARATION AND EVALUATION OF PARA-[AT-211]ASTATOBENZOYL LABELED ANTIRENAL CELL-CARCINOMA ANTIBODY A6H F(AB')2 - IN-VIVO DISTRIBUTION COMPARISON WITH PARA-[I-125]IODOBENZOYL LABELED A6H F(AB')2

A preliminary investigation of an At-211 labeled anti-renal cell carci noma antibody fragment, A6H F(ab')2, was conducted. In the investigati on, A6H F(ab')2 was labeled by conjugation with N-succinimidyl p-[At-2 11]astatobenzoate, and the in vivo biodistribution was evaluated in at hymic mice bearing TK-82 renal cell carcinoma xenografts. As a control , p-[I-125]iodobenzoyl labeled A6H F(ab')2 was coinjected with the ast atinated F(ab')2. The data obtained demonstrated that the two radiolab els (At-211 and I-125) had quite similar distributions, providing evid ence that the At-211 remained attached to the A6H F(ab')2 in vivo. Fur ther, the astatinated antibody attained a 2:1 tumor-to-blood ratio, an d greater than 35:1 tumor-to-muscle ratio, at 4 h post-injection, sugg esting that this antibody conjugate could be used to evaluate treatmen t of metastatic renal cell carcinoma in a mouse model.