CONJUGATE CHEMISTRY, IODINATION AND CELLULAR-BINDING OF MEGF-DEXTRAN-TYROSINE - PRECLINICAL TESTS IN PREPARATION FOR CLINICAL-TRIALS

A conjugate with specific binding to the epidermal growth factor recep tor, EGFR, and of interest for clinical tests was prepared using mouse epidermal growth factor, mEGF, and dextran. The mEGF was first couple d to dextran by reductive amination in which the free amino group on t he N-terminal of mEGF was reacted with the aldehyde group on the reduc tive end of the dextran chain. The end-end coupled intermediate was fu rther activated by the cyanopyridinium agent CDAP and tyrosines introd uced to the dextran part of the conjugate. The mEGF-dextran-tyrosine c onjugate was, with high efficiency, iodinated with the chloramine-T me thod. Approximately 25-35% of the radioactivity could be removed from the conjugate after exposure to protease K while 65-75% of the radioac tivity could be removed after exposure to dextranase. Thus, the larges t amount of the iodine was on the dextran part of the conjugate. The i odinated mEGF-dextran-tyrosine had EGFR specific binding since the bin ding to an EGFR rich human,glioma cell line could be displaced by an e xcess of non-radioactive mEGF. The conjugate was to a large extent int ernalized in these cells and the administrated radioactivity was there by retained inside the cells for at least up to 50 h.