Process for preparing purified drug conjugates

Abstract

The invention provides a process for preparing a cell-binding agent chemically coupled to a drug. The process comprises covalently attaching a linker to a cell-binding agent, a purification step, conjugating a drug to the cell-binding agent and a subsequent purification step.

1 . A process for preparing a cell-binding agent-cytotoxic agent conjugate comprising the steps of:
 (a) contacting a cell-binding agent with a bifunctional crosslinking reagent to covalently attach a linker to the cell-binding agent and thereby prepare a first mixture comprising cell-binding agents having linkers bound thereto,   (b) subjecting the first mixture to tangential flow filtration, selective precipitation, adsorptive filtration, or adsorptive chromatography and thereby prepare a purified first mixture of cell-binding agents having linkers bound thereto,   (c) conjugating a cytotoxic agent to the cell-binding agents having linkers bound thereto in the purified first mixture by reacting the cell-binding agents having linkers bound thereto with a cytotoxic agent in a solution having a pH of about 4 to about 9 to prepare a second mixture comprising (i) cell-binding agent chemically coupled through the linker to the cytotoxic agent, (ii) free cytotoxic agent, and (iii) reaction by-products, and   (d) subjecting the second mixture to selective precipitation, adsorptive filtration, or adsorptive chromatography to purify the cell-binding agents chemically coupled through the linkers to the cytotoxic agent from the other components of the second mixture and thereby prepare a purified second mixture of cell-binding agents chemically coupled through the linkers to the cytotoxic agent, 
with the proviso that if the first mixture is subjected to tangential flow filtration in step (b), the second mixture is not subjected to adsorptive chromatography in step (d). 
     
     
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