METHOD FOR PREPARING CELL-BINDING AGENT-CYTOTOXIC AGENT CONJUGATES

Abstract

The present invention provides a novel method for preparing a cell-binding cytotoxic agent conjugate. The method comprises the steps of: (a) reacting a cytotoxic agent with a bifunctional crosslinking reagent represented by the structural formula (i) or a salt thereof, in a buffer solution comprising a buffering agent to provide a first mixture comprising a cytotoxic agent-binding compound, in which the buffering solution has a high buffering capacity; and (b) reacting the first mixture comprising the cytotoxic agent-binding agent of step (a) with a cell-binding agent in a solution having a pH of 4 to 9 to provide a second mixture comprising the cytotoxic agent conjugate. Cell-binding agent cytotoxic agent conjugates prepared according to the methods described herein are also included in the present invention.